C J Sapart
email: c.j.sapart@uu.nl

Patricia Martinerie

Jérôme Chappellaz

R S W Van De Wal

P Sperlich

C Van Der Veen

Serge Bernard

W T Sturges

T Blunier

Emmanuel Witrant

J Schwander

D Etheridge

T R Öckmann

Reconstruction of the carbon isotopic composition of methane over the last 50 yr based on firn air measurements at 11 polar sites

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Methane (CH 4 ) is a strong greenhouse gas and plays an important role in atmospheric chemistry. Its atmospheric mixing ratios rapidly increased since 1800 in response to anthropogenic emissions (e.g. MacFarling [START_REF] Macfarling Meure | Law Dome CO 2 , CH 4 and N 2 O ice core records extended to 2000 years BP[END_REF]IPCC, 2007). Understanding the factors responsible for changes in atmospheric CH 4 is not straightforward, because the CH 4 atmospheric mixing ratio depends on the strength of its numerous sources and on the rate at which it is removed from the atmosphere by its different sinks (oxidation by tropospheric OH, stratospheric loss and soil uptake).

Stable isotope analysis represents an excellent tool to investigate changes of individual CH 4 sources and sinks in the atmosphere, because each type of emission/removal process is associated with a characteristic isotope signature (Quay et al., Figures Back Close

Full 1999; [START_REF] Houweling | The modeling of tropospheric methane: How well can point measurements be reproduced by a global model?[END_REF][START_REF] Miller | Development of analytical methods and measurements of δ 13 C in atmospheric CH 4 from the NOAA/CMDL global air sampling network[END_REF]Mikaloff Fletcher et al., 2004a,b;Tyler et al., 2007). Air enclosed in polar firn and ice represents an archive of past atmospheric composition (e.g. [START_REF] Craig | Methane -the record in polar ice cores[END_REF][START_REF] Schwander | The age of the air in the firn and the ice at summit, Greenland[END_REF][START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF]. The snow accumulates at the surface of the ice sheets and gradually densifies which leads to a slow trapping of the air in bubbles in the interstitial spaces. Firn represents the porous layer from the ice sheet surface down to the bubble close-off depth (40-120 m), where all the air is occluded in the ice, i.e. totally isolated from the atmosphere above. Trace gases moving downward with air in the firn column are affected by several mechanisms: molecular diffusion and gravitational settling [START_REF] Craig | Gravitational separation of gases and isotopes in polar ice caps[END_REF]Schwander et al., 1989;[START_REF] Sowers | Elemental and isotopic composition of occluded O 2 and N 2 in polar ice[END_REF], Spahni et al., 2003), thermal diffusion and turbulent transport [START_REF] Severinghaus | Thermal fractionation of air in polar firn by seasonal temperature gradients[END_REF], convection in the upper firn [START_REF] Sowers | Delta 15 N of N 2 in air trapped in polar ice -a tracer of gas-transport in the firn and a possible constraint on ice age-gas differences[END_REF] and advection caused by the firn sinking and the air being trapped in bubbles (Stauffer et al., 1985;[START_REF] Schwander | The age of the air in the firn and the ice at summit, Greenland[END_REF]. Firn transport models including those properties (e.g. [START_REF] Schwander | The age of the air in the firn and the ice at summit, Greenland[END_REF]Buizert et al., 2011, and reference therein) can calculate the evolution of trace gas concentrations in the atmosphere based on depth-dependent physical parameters of the firn (density, porosity, and tortuosity) and site-dependent surface conditions (temperature, precipitation and pressure).

Previous studies have shown the potential of reconstructing the history of the CH 4 budget using mixing and stable isotope ratios measurements from firn air [START_REF] Etheridge | Atmospheric CH 4 between 1000 AD and present: evidence of antropogenic emissions and climatic variability[END_REF][START_REF] Francey | A history of δ 13 C in atmospheric CH 4 from the Cape Grim air archive and Antarctic firn air[END_REF][START_REF] Br Äunlich | Changes in the global atmospheric CH 4 budget over the last decades inferred from δ 13 C and δD isotopic analysis of Antarctic firn air[END_REF][START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF]. Those studies reported CH 4 stable isotope data of firn air from Antarctica and suggested a rise in the stable carbon isotope of atmospheric CH 4 (noted thereafter: δ 13 C(CH 4 )) during the 20th century, which was ascribed to an increase of anthropogenic enriched (fossil and pyrogenic) CH 4 sources during this period.

Here we combine previously published firn air δ 13 C(CH 4 ) results from 5 sites and new results from 6 sites from both Greenland and Antarctica. Our goal is to reconstruct a multisite "best-estimate" atmospheric history for both hemispheres. To this end, we first reconstruct the atmospheric isotope histories from measurements at individual Figures sites, using the new LGGE-GIPSA firn model [START_REF] Rommelaere | Reconstructing recent atmospheric trace gas concentrations from polar firn and bubbly ice data by inverse methods[END_REF][START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF]Wang et al., 2011). We then discuss the differences among the 11 sites and use a multi-site inversion to retrieve the best-estimate reconstruction of δ 13 C(CH 4 ) from firn air over the last 50 yr. Finally, the math/mismatch of these firn air results with atmospheric data and ice core results is discussed.

Firn air sampling and isotope analysis

Firn air samples discussed in this paper come from 11 sites from both Greenland and Antarctica and were extracted between 1993 and 2009 (Table 1). The air extraction was carried out using different set-ups based on the principle described by [START_REF] Schwander | The age of the air in the firn and the ice at summit, Greenland[END_REF]. Air was pumped out of the firn after a stepwise drilling of the borehole in intervals of a few meters. At each depth, the hole was sealed by an inflatable rubber bladder through which a tube was introduced to pump out firn air to the surface into stainless steel, glass or aluminum containers. The containers were analyzed for δ 13 C(CH 4 ) in 4 different laboratories: Institute for Atmospheric and Marine research (IMAU), Laboratoire de Glaciologie et G éophysique de l'Environnement (LGGE), the Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the Center for Ice and Climate in Copenhagen (CIC) (Table 1). The different analytical systems are described in [START_REF] Francey | A history of δ 13 C in atmospheric CH 4 from the Cape Grim air archive and Antarctic firn air[END_REF][START_REF] Br Äunlich | Changes in the global atmospheric CH 4 budget over the last decades inferred from δ 13 C and δD isotopic analysis of Antarctic firn air[END_REF], [START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF], Brass and[START_REF] Sapart | Simultaneous stable isotope analysis of methane and nitrous oxide on ice core samples[END_REF] and [START_REF] Sperlich | A combustion setup to precisely reference δ 13 C and δD isotope ratios of pure methane to produce isotope reference gases of methane in air akin to atmosphere[END_REF].

To verify the mutual consistency among datasets from different laboratories, IMAU measured samples from NGRIP (NGR) and Dome C (DC), which were previously analyzed by LGGE [START_REF] Br Äunlich | Changes in the global atmospheric CH 4 budget over the last decades inferred from δ 13 C and δD isotopic analysis of Antarctic firn air[END_REF]. The average δ 13 C(CH 4 ) difference between IMAU and LGGE is 0.14 ± 0.07 ‰ for which IMAU data have been corrected. The same correction is applied to NEEM 2008 firn samples from the European hole (NM-EU-08), which were measured at both IMAU and CIC in this study. It has been shown previously that there are no systematic differences between LGGE and CSIRO [START_REF] Bernard | Evolution temporelle du m éthane et du protoxyde d'azote dans l'atmosph ère: contrainte par l'analyse de leurs isotopes stables dans le n év é et la glace polaires[END_REF]. Figures

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Full The error bars assigned to individual data points in this paper generally represent the standard deviation of several measurements on the same firn air sample. Measurements of other trace gases samples from the same boreholes usually lead to the conclusion that possible sampling artifacts such as fractionation during the firn extraction or leaks of the bladders are negligible on the investigated sites.

Data

The δ 13 C(CH 4 ) firn air results are separately presented for the Northern Hemisphere (NH) sites and the Southern Hemisphere (SH) sites in Fig. 1. At each location, δ 13 C(CH 4 ) shows a stable or slowly decreasing trend with depth in the upper firn and stronger isotope depletions in the bubble close-off zone (deeper firn). The firn structure and thickness depend on the snow accumulation rate and on temperature at each site (Table 1) hence these parameters cause differences in the depth profiles observed among the sites (Fig. 1). For the NH sites, the differences are small between the Greenland sites (NEEM and NGR), because the surface conditions (temperature, snow accumulation, etc.) are rather similar at these sites. The Devon Island (DI) dataset shows a different pattern, as surface conditions differ significantly from the Greenland sites. Numerous melt layers have been detected in the DI firn column (e.g. [START_REF] Martinerie | Long-lived halocarbon trends and budgets from atmospheric chemistry modelling constrained with measurements in polar firn[END_REF], which largely reduce molecular diffusivity with depth. The SH data show larger differences between the sites, because the meteorological/glaciological variables (temperature, snow accumulation, snow morphology, etc.) in Antarctica differ strongly from site to site. Firn air was sampled in different years (Table 1), but the upper firn data, corrected for seasonality (see Supplement) for the NH sites, do not show a systematic trend in correlation with the sampling date.

Modeling trace gas transport in firn

To convert vertical δ 13 C(CH 4 ) depth profiles in the firn into temporal atmospheric isotope scenarios, we use a modelling approach based on the mathematics described in [START_REF] Rommelaere | Reconstructing recent atmospheric trace gas concentrations from polar firn and bubbly ice data by inverse methods[END_REF][START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF]. The physical model uses atmospheric scenarios (best-guess historic evolution of trace gas concentrations) to calculate vertical profiles of concentrations in firn. In the case of isotopic ratios, two simulations are performed for the major and minor isotopologues, 12 CH 4 and 13 CH 4 , respectively. Besides atmospheric scenarios, the site temperature, accumulation rate, depth of the convective layer in the upper firn, and the close-off depth are used to constrain the model together with profiles of firn density and effective diffusivity. The effective diffusivity is not affected by the micro-structure of the firn, i.e. pore spreading, size and shape, but is related to molecular diffusion occurring at the macro-structure scale, i.e. the density fluctuations [START_REF] Fabre | Determination of gas diffusivity in polar firn: comparison between experimental measurements and inverse modeling[END_REF]. The effective diffusivity is determined as a function of depth for each firn drilling site by modeling the concentrations in firn for trace gases with well-known recent histories [START_REF] Rommelaere | Reconstructing recent atmospheric trace gas concentrations from polar firn and bubbly ice data by inverse methods[END_REF][START_REF] Trudinger | Modeling air movement and bubble trapping in firn[END_REF]. Here we used a multi-gas constrained inverse method [START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF] to calculate the firn diffusivity at each site. It is important to note that the diffusivity is not constrained equally well at all sites. This is firstly due to the fact that a different number of species has been used for diffusivity reconstruction for each site, and secondly because firn data were obtained with different depth resolutions (less than 1 m to ∼10 m sampling intervals).

Once the diffusivity is obtained, another version of the model based on the forward model physics was used to reconstruct atmospheric time trend scenarios from firn concentration data. We use the Green function approach introduced by Rommelaere et al. (1997), which has been recently extended to isotopic ratios (Wang et al., 2011;[START_REF] Sapart | Natural and anthropogenic variations in methane sources over the last 2 millennia[END_REF] to calculate the probability to have air of a certain age at a certain depth.

Single-site δ 13 C scenarios

In order to investigate the consistency among the different sites, the inverse scenario model has been applied to the isotope data from each site individually and single site δ 13 C(CH 4 ) atmospheric trends have been determined (Fig. 2). The center panels in Fig. 2 show the comparison of the modeled δ 13 C(CH 4 ) firn profiles using the scenarios shown in the left hand panels and the measurements. The differences between the modeled and measured firn air datasets (panels c and f) are in the majority of the cases similar to or smaller than the assigned measurement uncertainties. This shows that mathematically the inversion setup performs well, i.e. the reconstructed atmospheric δ 13 C(CH 4 ) scenarios produce firn air isotope profiles, which are in agreement with the measurements. Strong deviations are observed for two data points only, the DI value at 54 m depth, and the SPO-01 value at 53 m depth. We consider the anomalous data point at SPO-01 as an outlier, because it occurs in the upper firn, where fast diffusion combined with the long time scales of isotope variations is inconsistent with strong isotope variability. Removing this point does not significantly affect the reconstructed scenario. The numerous melt layers (up to 7 cm of thickness) identified in the DI firn column likely imply that horizontal diffusion is no longer negligible, because gases may have to travel horizontally around the impermeable layers to reach the deeper firn. Low permeability layers and horizontal transport are not represented in our 1-D firn model. In addition, the model assumes steady-state of the firn structure, whereas at DI the diffusivity/depth profile probably changed with time due to the unequal distribution of melt layers with depth. DI will thus not be used in the final multisite scenario reconstruction.

Whereas the inversion technically adequately fits the measurements at individual sites, an important result of these single site inversions is that the atmospheric histories reconstructed from individual sites show a large variability, as seen in the left panels of Fig. and SH high latitudes, due to the longer time required for isotopic ratios than mixing ratios to adapt to a new source configuration [START_REF] Tans | A note on isotopic ratios and the global atmospheric methane budget[END_REF]. On the other hand the scenario based on SPO-01 shows large discrepancies (more than 2 ‰) in comparison with other SH sites. DC and SPO-95 based scenario are flatter than the previously published scenarios for these sites [START_REF] Br Äunlich | Changes in the global atmospheric CH 4 budget over the last decades inferred from δ 13 C and δD isotopic analysis of Antarctic firn air[END_REF][START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF] ably result from the use of different diffusivity profiles and modeling approach. Indeed in a firn model intercomparison study, [START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF], conclude that diffusive fractionation of isotopes is insufficiently constrained by firn models and that using different firn air models can result in significantly different reconstructions. We further investigate this issue in Sects. 5.3 and 5.4.

Effect of firn fractionation

The difference of molecular diffusion coefficient in air between the two isotopologues 12 CH 4 and 13 CH 4 produces large changes of δ 13 C(CH 4 ) in the firn column even in absence of δ 13 C(CH 4 ) trend in the atmosphere. Therefore it is important to evaluate the amplitude of the combined effects of isotopic fractionation in firn due to molecular diffusion and gravitational settling using a firn model runs in forward mode [START_REF] Trudinger | Modeling air movement and bubble trapping in firn[END_REF]. An atmospheric CH 4 scenario based on NOAA-ESRL atmospheric network and ice core data [START_REF] Etheridge | Atmospheric CH 4 between 1000 AD and present: evidence of antropogenic emissions and climatic variability[END_REF][START_REF] Macfarling Meure | Law Dome CO 2 , CH 4 and N 2 O ice core records extended to 2000 years BP[END_REF], assuming a constant atmospheric δ 13 C(CH 4 ) history, is used as input to model 12 CH 4 [START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF] The calculated 12 CH 4 and 13 CH 4 mixing ratios in firn air are then recombined to yield a δ 13 C(CH 4 ) depth profile which is only due to isotopic fractionation in firn and not to changes in the atmospheric history.

Results are shown in Fig. 3 as the difference between δ 13 C(CH 4 ) at the surface and δ 13 C(CH 4 ) at each sample depth level, and compared with the same difference in the firn data (δ 13 C(CH 4 )δ 13 C(CH 4 ) surface ). Gravitational fractionation produces a slight upward trend in δ 13 C(CH 4 ) in the diffusive part of the firn column (see Supplement, Fig. S1) whereas molecular diffusion in combination with the CH 4 mixing ratio gradient along the firn profile produces a clear trend in δ 13 C(CH 4 ) towards more depleted values in the deep firn, the amplitude being site-dependent (Fig. 3).

At most sites, isotopic fractionation in firn alone can already explain a large fraction of the trends in the observed δ 13 C(CH 4 ) depth profiles. This implies that only a small and positive trend in atmospheric δ 13 C(CH 4 ) is needed to fit the measurements (Fig. 3). For DI, DML, and SPO-01, however, the difference between the constant δ 13 C(CH 4 )

scenario and the data is large. Therefore, the scenarios reconstructed from these sites show rather large atmospheric trends in comparison with the other sites as shown in Fig. 2. Although firn data do not suggest strong differences in the firn physical properties between the two drill holes at South Pole (1995 and2001), the model produces different estimates of isotopic fractionation in firn and the possible reason for this is debated in the next section.

Sensitivity to small changes in diffusivity

The discrepancy between the reconstructed histories at South Pole from the two firn air campaigns in 1995 and 2001 is puzzling and we investigated possible causes. An important input parameter in firn models is diffusivity (e.g. [START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF], which is constructed for each site and drilling operation from an inversion approach using trace gas mixing ratios with relatively well-known atmospheric histories, as explained Introduction

Conclusions Figures

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Full in Sect. 4. For SPO-95, the diffusivity is constrained by a combination of 6 species (CO 2 , CH 4 , SF 6 , CH 3 CCl 3 , CFC-11, CFC-12) whereas data for only 3 species (CO 2 , CH 4 , SF 6 ,) are available for SPO-01, hence these diffusivities are not equally well constrained [START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF]. [START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF] only used the CO 2 atmospheric history and firn air profile to deduce the diffusivity profile used for both SPO-95 and SPO-01. The CH 4 depth profile only qualified a posteriori the CO 2 -constrained diffusivity profile.

To investigate the sensitivity of δ 13 C(CH 4 ) to small differences in the diffusivity profile, atmospheric scenarios were simulated for SPO-01 using the better constrained diffusivity profile of SPO-95 (Fig. 4). The rationale behind this approach is that the diffusivity profiles at nearby drilling locations (with density profiles and close-off depths nearly similar) are expected to be comparable even if the firn core is drilled in a different year. A diffusivity profile from a nearby firn drilling site where more trace gas profiles are available may then be more realistic than the profile from a certain location where only few species are available. Figure 4 shows that this slight change in diffusivity has apparently a large effect on the δ 13 C(CH 4 ) reconstruction and removes much of the discrepancy that was apparent for the SPO-01 samples in the original inversion.

It is important to note that the model runs with the modified diffusivity still produce acceptable agreement with the CO 2 , CH 4 and SF 6 mixing ratios (the tracers used for determining the diffusivity profile) measured at SPO-01 (Witrant et al., 2011). the isotopic fractionation in firn of NM-EU-08 leads to a reduced fractionation below ∼60 m (Fig. 4: purple long dashed-line) than using the NM-09 diffusivity (Fig. 4: purple long dashed-line). This means that even though the diffusivity profiles of NM-US-08 and NM-09 which were constrained by almost the same species, show significant differences. These diffusivity differences might be due to lateral inhomogenities in the firn or by sampling or analytical artifacts, e.g.: sample contaminations or bladder outgassing [START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF]. Additionally, we compared the effect of diffusivity for two Antarctic sites with high (DE08) and low (DML) snow accumulation rates (Table 1). Indeed, high accumulation sites are expected to be less affected by isotopic fractionation in firn, due to a thinner diffusive column height and due to a stronger advection/faster gas trapping in bubbles. For DEO8, we used two different diffusivity profiles (constrained with/without the CO 2 outlier at 80 m depth, [START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF] and this leads to a small difference in δ 13 C(CH 4 ) (∼0.2 ‰) in the calculated isotopic fractionation at 80 m depth (Fig. 4: yellow full and dashed lines). This indicates that for high accumulation sites, changing the diffusivity has a limited effect on isotopic fractionation. A very small firn fractionation estimate is obtained at DML whereas it belongs to the low accumulation rate category. This results in a very strong change in atmospheric δ 13 C(CH 4 ) with time in the singlesite reconstruction, which is not in agreement with the isotope histories at most other sites (Fig. 2). Here, we do not have an alternative diffusivity profile from a similar site.

We thus attempted to use a data based δ 13 C(CH 4 ) atmospheric trend as an additional constraint in the construction of the diffusivity profile. We used a δ 13 C(CH 4 ) scenario may be due to an insufficient sampling resolution below 70 m depth (2 depth levels), where steep concentration gradients are observed for all species. This example of using δ 13 C(CH 4 ) as a constraint confirms the strong sensitivity of δ 13 C(CH 4 ) to the firn diffusivity profiles. This implies that -once a reliable isotope history has been established -δ 13 C(CH 4 ) may be a valuable constraint to obtain realistic firn diffusivity profiles. In this case, the "weakness" of δ 13 C(CH 4 ), namely that the isotopic fractionation in firn is of the same order of magnitude or even larger than the atmospheric changes, turns into an advantage. In summary, these results show that model estimates of isotopic fractionation in firn are strongly dependent on the diffusivity profile used. Although constrained in our case with multiple gas histories, the firn diffusivity is not always sufficiently constrained for an accurate estimate isotopic fractionation for δ 13 C(CH 4 ) at least in the deep firn and thus for atmospheric reconstruction of δ 13 C(CH 4 ) from a single site.

Multi-site δ 13 C reconstruction

We have shown that trying to reconstruct atmospheric scenarios of δ 13 C(CH 4 ) from single sites leads to sometime inconsistent solutions. We thus try in the following to extract a "best estimate" by performing two inversions for all sites from the SH and NH, respectively (Fig. 5). In the NH multi-site inversion, the DI data are excluded as the firn column at this site is affected by melt layers, which likely caused the inconsistency with other sites as shown by the single site reconstructions (Fig. 3). In the SH multi-site inversion, the SPO-95 diffusivity profile is used for the SPO-01 site. The deepest firn data points provide constraints further back in time compared with shallower data points in the bubble close-off zone, thus potentially extending the historical reconstruction of atmospheric δ 13 C(CH 4 ) back to the early 20th century [START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF]. As the correction for isotopic fractionation in firn is most uncertain for the deepest samples, where strong differences between individual firn air models have been reported [START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF] fractionation were excluded (Fig. 3). In the NH, as NM-09 diffusivity is constrained with only two gases (CO 2 and CH 4 ) instead of nine gases for NEEM-EU, a larger number of data are eliminated for NEEM-09. The excluded data points are shown in grey in Fig. 5. As this data elimination procedure is somewhat subjective, an alternative method was also used where all data below the lock-in depth (LIDgas in Table 2 of [START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF] were eliminated. The two methods lead to very similar results (see Supplement, Fig. S4). This restricts the duration of the scenario constrained by the remaining firn data to the last ∼50 yr (mean ages at the last depth levels used are provided in Table 1), but it provides a more robust scenario.

In the multisite inversion, each firn profile is given equal weight (red lines in the left panels of Fig. 5). In a second inversion (green lines in left panels of Fig. 5), the contribution of each site is weighted according to the inverse of the RMS (root mean squared) difference of the model results from single site inversions (Fig. 2) and the measurements. This weighting reduces the relative weight of sites that are supposedly affected by larger experimental uncertainties. It leads to slightly flatter δ 13 C(CH 4 ) scenarios in the latter multi-site inversion, but the results in Fig. 5 show that the differences are well within the uncertainty envelopes of the original multisite inversion. The middle panels in Fig. 5 show how the modeled firn air δ 13 C(CH 4 ) profiles, based on the multisite atmospheric reconstructions, agree with the experimental data. The right hand panels show the model-measurement differences. Overall, the differences are of the order of the analytical uncertainty 0.05-0.3 ‰. The multisite δ 13 C(CH 4 ) reconstructions (Fig. 5) show an increase in δ 13 C(CH 4 ) over the last decades, but the magnitude of the increase (0.7 ‰ over 50 yr) is about 50-60 % smaller than reported previously [START_REF] Francey | A history of δ 13 C in atmospheric CH 4 from the Cape Grim air archive and Antarctic firn air[END_REF][START_REF] Br Äunlich | Changes in the global atmospheric CH 4 budget over the last decades inferred from δ 13 C and δD isotopic analysis of Antarctic firn air[END_REF][START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF][START_REF] Ferretti | Unexpected changes to the global CH 4 budget over the past 2000 years[END_REF].

As a further check of consistency of the individual firn air measurements with the multisite δ 13 C(CH 4 ) scenario, we convert the measurements from each depth into temporal isotope values, using the mean age of the samples and taking into account the isotopic fractionation in firn. This approach was also used in e.g. and [START_REF] Ferretti | Unexpected changes to the global CH 4 budget over the past 2000 years[END_REF]. Figure 6 shows that the data from the individual sites fall within the uncertainty range of the multisite reconstruction. Note that for the readability of the figure, the age spread is not represented in Fig. 6, but note that no discrete age exist for a given firn air sample. The lower panel shows that the data from DE08 and SPO-01 are near the lower envelope of the multisite reconstruction, whereas the data from VOS are for a large part of the record near the higher end. This reflects the results from the single site reconstructions, where the VOS data required only a weak δ 13 C(CH 4 ) atmospheric trend, whereas DE08 and SPO-01 required a strong δ 13 C(CH 4 ) atmospheric trend.

The multisite reconstruction is constrained by δ 13 C(CH 4 ) data from the ten sites presented in Table 1 (i.e. excluding DI). For the NH sites, the "best estimate" scenario is constrained by only a few data points before 1990. Furthermore, the firn profiles at the three sites that enter the multisite inversion (NGR, NM-EU-08 and NM-09) are alike, as shown by the similar vertical profiles in Fig. 1. Therefore, the NH scenario is much less constrained than the SH scenario, where data from sites with very different firn characteristics and sampling dates are available. The lack of independent constraints and the relatively small number of data points may explain the higher variability of the NH δ 13 C(CH 4 ) reconstruction.

Although the multisite scenarios for the SH and NH agree within the uncertainty envelopes, the shape of the best estimate slightly different scenarios for the two hemispheres. Due to the fact that the main anthropogenic CH 4 sources are in the NH, it cannot be excluded that the inter-polar gradient (IPG) of δ 13 C(CH 4 ) changed, but given the short interhemispheric mixing time of 1 yr, large variations on short timescales are unlikely. In any case, given the larger errors of the multisite reconstructions it is not possible to extract robust information about the IPG.

Alternatively, in order to combine all available independent constraints, in the last step we attempt to reconstruct a combined global δ a multisite inversion was performed using all data from both hemispheres together. This exercise was performed with values for the IPG between 0.2 and 0.5 ‰. The scenario with the lowest RMS difference is obtained for an IPG of 0.3 ‰. The results from this "global multisite" inversion are depicted in green dashed-lines in Fig. 7 and they may be compared to the hemispheric multisite reconstructions (red lines).

Comparison of our firn reconstructions with atmospheric and ice core data

In Fig. 7, we compare our firn air reconstructions with direct and archive atmospheric measurements, and ice core data. Continuous atmospheric measurements of δ 13 C(CH 4 ) have been carried out over the last ten years in both hemispheres. For the NH, no direct atmospheric data are available before 2000. For the SH, δ 13 C(CH 4 )

was determined from archived air samples collected at Cape Grim, Australia from the late 1970's [START_REF] Francey | A history of δ 13 C in atmospheric CH 4 from the Cape Grim air archive and Antarctic firn air[END_REF]. Moreover, ice core data from Law Dome, Antarctica [START_REF] Ferretti | Unexpected changes to the global CH 4 budget over the past 2000 years[END_REF] overlap in time with the period of our multisite reconstruction.

For the NH, no δ 13 C(CH 4 ) ice core data are available for the reconstructed period, because the age of the youngest air from Greenland ice cores is older than 50 yr. We thus show in Fig. 7 a comparison with five data points from EUROCORE [START_REF] Sapart | Natural and anthropogenic variations in methane sources over the last 2 millennia[END_REF] covering the period 1800-1950. It shows that the δ 13 C(CH 4 ) reconstruction from the firn gas samples agrees well with the direct measurements over the last decade (light grey lines), which provides evidence for a negligible δ 13 C(CH 4 ) trend over this period. The Cape Grim archive data from the SH (dashed grey line in Fig. 7, lower panel) show a steeper temporal trend and fall outside the low end of our reconstruction before ∼1975. Here, the fact that inter-laboratory calibration offsets can considerably hamper direct comparison of the datasets has to be taken into account. The Cape Grim and Law Dome data were measured in the same lab, and have been reported to be on the same scale as the PSU measurements [START_REF] Mischler | Carbon and hydrogen isotopic composition of CH 4 over the last 1000 years[END_REF]). An offset of 0.28 ‰ between the IMAU and PSU scales has been identified in an intercalibration exercise [START_REF] Sapart | Simultaneous stable isotope analysis of methane and nitrous oxide on ice core samples[END_REF]. If the Cape Grim data are corrected upwards for Figures

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Full this difference based on this indirect evidence, they become in acceptable agreement with the lower envelope of our best estimate scenario and the direct atmospheric data. Whereas an absolute offset can thus tentatively be attributed to uncertainties in the calibration scales, the Cape Grim data also show a somewhat stronger δ 13 C(CH 4 ) trend than the multisite firn air scenario. One should keep in mind that our reconstructed scenarios are sensitive to the best-guess CH 4 input scenario. A sensitivity test (Supplement, Fig. S2) shows that using atmospheric CH 4 values at the upper end of their uncertainty envelope leads to a slope nearly consistent with the one from the Cape Grim air archive.

The same interpretation holds for the firn and ice core data from [START_REF] Ferretti | Unexpected changes to the global CH 4 budget over the past 2000 years[END_REF] from Law Dome, which are also included in Fig. 7, lower panel. A shift of 0.28 ‰ would bring these results closer to the scenario range reconstructed from the firn air data, but the Law Dome data still suggest stronger isotope changes in the past than our multisite reconstruction (this was also inferred from the single site scenario reconstruction based on DE08 firn data only shown in Fig. 2). Ice core data are also affected by isotopic fractionation effects in the overlying firn, and the data published in [START_REF] Ferretti | Unexpected changes to the global CH 4 budget over the past 2000 years[END_REF] were corrected for these effects using the CSIRO firn air model (Fig. 7: orange dots). To be consistent with our own reconstructions, the corresponding corrections were also calculated with the LGGE-GIPSA model using regular diffusivity (Fig. 7: black stars) and "slightly modified diffusivity" as explained in Sect. 5.3. (Fig. 7: red stars). The corrected firn air data with the CSIRO model (orange dots) and with the LGEE-GIPSA model with modified diffusivity (red stars) show quite similar results which implies that the difference in firn air models is not responsible for the differences between the Law Dome records and our SH firn reconstruction. The differences between the raw and firn fractionation-corrected δ 13 C(CH 4 ) shown in Fig. 7 demonstrate that the young ice core data are also significantly affected by isotopic fractionation in the firn. This is expected since these samples contain air from a period when CH 4 mixing ratios in the atmosphere strongly increased. The same is true for the only available ice core data from the NH site EUROCORE (Fig. 7, upper panel). However, here the Introduction

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Full [START_REF] Sapart | Simultaneous stable isotope analysis of methane and nitrous oxide on ice core samples[END_REF], and a corresponding correction would obviously bring the data in better agreement with the firn reconstruction. The firn/ice data comparison for the Northern Hemisphere is limited by the absence of overlapping period but the large difference between the EUROCORE and Law Dome data at 1950 additionally implies a possible unidentified interlaboratory offset between these datasets.

Discussion

The data evaluation and interpretation above highlights the importance of isotopic fractionation in polar firn for reconstructions of δ 13 C(CH 4 ). This is because isotopic fractionation effects are of the same order of magnitude or even larger than the atmospheric δ 13 C(CH 4 ) signal. When analyzed with the same inverse firn air model, single site reconstructions from 11 sites lead to strongly different atmospheric isotope histories.

Investigation of the data used to derive diffusivity profiles indicate that in general diffusivity profiles constrained by a larger number of atmospheric species lead to stronger isotopic fractionation effects and thus smaller isotope trends in the model than at sites with diffusivity profiles constrained by less species. For the two firn air sampling campaigns performed at South Pole, our work shows that a single site inversion of the SPO-01 data agrees much better with reconstructions from other sites when the presumably better constrained diffusivity profile of SPO-95 is used. When the deepest firn data-points are neglected, due to assumed larger uncertainties in the isotopic fractionation affecting these samples, it is possible to build a multisite firn air δ 13 C(CH 4 ) reconstruction that leads to consistent results at all sites (when the diffusivity profile of SPO-95 is used for the SPO-01 data). This scenario is consistent with recent atmospheric data, but shows differences with Cape Grim air archive and Law Dome ice Figures

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Full core data. Those differences maybe due to calibration issues, uncertainties on the CH 4 scenario and/or insufficiently constrained diffusivity. Another source of uncertainty is the firn model itself. [START_REF] Buizert | Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland[END_REF] showed that different firn air models produce isotopic fractionation effects of different magnitude. For δ 13 C(CO 2 ), the LGGE-GIPSA model produces the largest diffusive fractionation in the lock-in-zone. This may bias our reconstructions slightly towards smaller required atmospheric trends. On the other hand, the correction for isotopic fractionation along the Law Dome firn column and in ice bubble show that our model is consistent with the CSIRO model and yields the same trend in δ 13 C(CH 4 ). Our best estimate scenario based on multi-site inversion can be considered as the state-of-the-art of conclusions bearable from the existing δ 13 C(CH 4 ) firn air data. However, due to uncertainties in estimating the isotopic fractionation effects, it remains tentative to reconstruct δ 13 C(CH 4 ) during periods of strong CH 4 increase.

The difficulties in constraining the atmospheric isotope history of δ 13 C(CH 4 ) may turn into an advantage when investigating the consistency between diffusivity profiles at different firn air sites. The sensitivity of δ 13 C(CH 4 ) to diffusivity profiles provide a useful model constraint if the atmospheric record is independently known. But for the time being, this turns into a circular argument since the δ 13 C(CH 4 ) history since pre-industrial times is not uniquely defined yet. Our reconstructed δ 13 C(CH 4 ) trend between 1960 and 2009 is only half of the previously published trends in δ 13 C(CH 4 ) [START_REF] Francey | A history of δ 13 C in atmospheric CH 4 from the Cape Grim air archive and Antarctic firn air[END_REF][START_REF] Br Äunlich | Changes in the global atmospheric CH 4 budget over the last decades inferred from δ 13 C and δD isotopic analysis of Antarctic firn air[END_REF][START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF]. On the other hand, the measurements on ice core samples in the period before the strong increase in CH 4 started clearly implies that there must have been a strong increase in δ 13 C(CH 4 ) since pre-industrial times. Whereas the previous studies concluded that most of the enrichment occurred during the last 50 yr, the firn air reconstruction would imply that there was also a strong increase already before 1960. Introduction

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Full

Conclusions

We reconstructed δ 13 C(CH 4 ) atmospheric scenarios over the last 50 yr for both Northern and Southern hemispheres using a firn transport model taking as input δ 13 C(CH 4 )

firn air measurements at 11 sites. Our calculations reveal discrepancies between sites while running single-site inversion and show that the estimate of isotopic fractionation between 12 CH 4 and 13 CH 4 along the firn column is highly dependent on how good the diffusivity profiles are constrained for each site.

After plausible adjustments of diffusivity profiles at individual sites, and neglecting the deepest firn air samples (where the isotopic fractionation is strongest), it is possible to reconstruct a best estimate of δ 13 C(CH 4 ) for each hemisphere from a multisiteinversion, which fits all measurements within the errors of the reconstruction. This scenario shows an increase of about 0.7 ‰ between 1960 and 2000 followed by a period of relatively stable δ 13 C(CH 4 ) values since then, in agreement with direct atmospheric measurements. The scenario shows, however, remaining discrepancies with the deepest firn air data, and with published ice core data [START_REF] Ferretti | Unexpected changes to the global CH 4 budget over the past 2000 years[END_REF] for the same period. Interlaboratory calibration offsets likely contribute to the differences with the ice core data, but uncertainties in the isotopic fractionation in firn air models is important as well. The reconstructed isotope trend between 1960 and 2009 is a factor of 2 smaller than previously published trends in δ 13 C(CH 4 ) [START_REF] Francey | A history of δ 13 C in atmospheric CH 4 from the Cape Grim air archive and Antarctic firn air[END_REF][START_REF] Br Äunlich | Changes in the global atmospheric CH 4 budget over the last decades inferred from δ 13 C and δD isotopic analysis of Antarctic firn air[END_REF][START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF]. Discuss., 11, 30627-30663, doi:10.5194/acpd-11-30627-2011, 2011. Witrant, E., Martinerie, P., Hogan, C., Laube, J. C., Kawamura, K., Capron, E., 7: Multi--site "best estimate" δ 13 C(CH4) scenario compare with atmospheric archive from Cape Grim (dashed grey line) and ice core data (dots). The red dashed--lines are the "best--estimate" scenario for each hemisphere. The green dashed--lines are the scenarios including all sites from both hemispheres together and using an inter--polar gradient of 0.3‰. a: NH raw δ 13 C(CH4) data (light blue dots) and δ 13 C(CH4) data corrected for firn fractionation from EUROCORE ice core (Sapart et al., under review). b: SH raw δ 13 C(CH4) firn and ice data at DEO8 (yellow dots) and the same data corrected for firn fractionation with the CSIRO model (orange dots) [START_REF] Francey | A history of δ 13 C in atmospheric CH 4 from the Cape Grim air archive and Antarctic firn air[END_REF][START_REF] Ferretti | Unexpected changes to the global CH 4 budget over the past 2000 years[END_REF], with the LGGE--GIPSA model using regular diffusivity (black stars) and with the LGGE--GIPSA model but with "slightly modified diffusivity" as in Fig. 4 (red stars). The grey lines represent continuous atmospheric monitoring data from the NOAA--ESRL network (NH and SH). . ! Fig. 7. Multi-site "best estimate" δ 13 C(CH 4 ) scenario compare with atmospheric archive from Cape Grim (dashed grey line) and ice core data (dots). The red dashed-lines are the "bestestimate" scenario for each hemisphere. The green dashed-lines are the scenarios including all sites from both hemispheres together and using an inter-polar gradient of 0.3 ‰. (a) NH raw δ 13 C(CH 4 ) data (light blue dots) and δ 13 C(CH 4 ) data corrected for firn fractionation from EUROCORE ice core [START_REF] Sapart | Natural and anthropogenic variations in methane sources over the last 2 millennia[END_REF]. (b) SH raw δ 13 C(CH 4 ) firn and ice data at DEO8 (yellow dots) and the same data corrected for firn fractionation with the CSIRO model (orange dots) [START_REF] Francey | A history of δ 13 C in atmospheric CH 4 from the Cape Grim air archive and Antarctic firn air[END_REF][START_REF] Ferretti | Unexpected changes to the global CH 4 budget over the past 2000 years[END_REF], with the LGGE-GIPSA model using regular diffusivity (black stars) and with the LGGE-GIPSA model but with "slightly modified diffusivity" as in Fig. 4 (red stars). The grey lines represent continuous atmospheric monitoring data from the NOAA-ESRL network (NH and SH).

Supplementary material related to this article is available

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  A possible trend in δ 13 C(CH 4 ) in the atmosphere between 1993 and 2009 is thus not detectable in our dataset. The effect of seasonality on the upper firn data is discussed in more detail in Sect. 1 of the Supplement. Discussion Paper | Discussion Paper | Discussion Paper |

  2. Differences could be expected between the δ 13 C(CH 4 ) trends at NH Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

  for the NH and Witrant et al., 2011 for the SH), and 13 CH 4 in the firn column. Discussion Paper | Discussion Paper | Discussion Paper |

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A

  similar comparison was made for the two different NEEM holes drilled in 2008 and 2009. Although the single site isotope reconstructions from these sites are not as different as for SPO (Fig. 2), we ran the inversion of the 2009 hole with the diffusivity profile reconstructed from the 2008 hole. Diffusivity for the NM-09 hole was constrained with 2 species (CO 2 and CH 4 ) and diffusivity for NM-08 by 9 species (CO 2 , CH 4 , SF 6 , CH 3 CCl 3 , CFC-11, CFC-12, CFC-13, HFC-134a, 14 CO 2 ). The atmospheric δ 13 C(CH 4 ) history for the 2009 reconstruction with the (better constrained) 2008 diffusivity is in good agreement with the original NM-EU-08 results (see Fig. 4, upper panel). Using the diffusivity of NM-US-08, constrained by three species (CO 2 , CH 4 , SF 6 ) to estimate Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

  based on our single-site reconstructions and ice core data from[START_REF] Ferretti | Unexpected changes to the global CH 4 budget over the past 2000 years[END_REF], in addition to six other gases species (CO 2 , CH 4 , SF 6 , CH 3 CCl 3 , CFC-12, CFC-113). As expected, the simulations with this modified diffusivity profile lead to a considerably stronger isotopic fractionation along the DML firn column (Fig.4: black dashed-line). On the other hand, the other gases are still fitted well with this modified diffusivity profile (not shown). The large uncertainty of the isotopic fractionation in the deep DML firn Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

  , the deep firn data points showing strong deviations with the modeled isotopic Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

  [START_REF] Francey | A history of δ 13 C in atmospheric CH 4 from the Cape Grim air archive and Antarctic firn air[END_REF] Discussion Paper | Discussion Paper | Discussion Paper |

  13 C(CH 4 ) history, assuming that the IPG of δ 13 C(CH 4 ) has not changed over the period of the reconstruction. To facilitate this, the NH data were shifted by the magnitude of an assumed constant IPG, and then Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

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  Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | δ 13 C(CH 4 ) data corrected for isotopic fractionation are rather at the high end of the firn air reconstruction. The ice core EUROCORE data are possibly enriched 0.25 ‰ with respect to the firn air data based on comparison of ambient and ice air samples

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  Discussion Paper | Discussion Paper | Discussion Paper | Tyler, S. C., Rice, A. L., and Ajie, H. O.: Stable isotope ratios in atmospheric CH 4 : implications for seasonal sources and sinks, J. Geophys. Res., 112, D03303, doi:10.1029/2006JD007231, 2007. Wang, Z., Chappellaz, J., Martinerie, P., Park, K., Petrenko, V., Witrant, E., Blunier, T., Brenninkmeijer, C. A. M., and Mak, J. E.: The isotopic record of Northern Hemisphere atmospheric carbon monoxide since 1950, implications for the CO budget, Atmos. Chem. Phys.

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Figure 1 :

 1 Figure 1: δ 13 C(CH4) of firn air. a: The NH sites are: Devon Island (DI), North GRIP (NGR), NEEM 2009 (NM--09), NEEM--EU 2008 (NM--EU--08) measured by IMAU and CIC. b: The SH sites are: DE08--2 (DE08), Berkner Island (BI), Vostok (VOS), Dronning Maud Land (DML) and Dome Concordia (DC) (Bräunlich et al., 2001), South Pole 1995 (SPO--95) and South Pole 2001 (SPO--01)[START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF]. The numbers associated to the names on the legend are the dates (year) of the firn sampling for each site.

Fig. 1 .Figure 2 :Fig. 2 .Fig. 3 .Fig. 5 .Fig. 6 .

 122356 Fig. 1. δ 13 C(CH 4 ) of firn air. (a) The NH sites are: Devon Island (DI), North GRIP (NGR), NEEM 2009 (NM-09), NEEM-EU 2008 (NM-EU-08) measured by IMAU and CIC. (b) The SH sites are DE08-2 (DE08), Berkner Island (BI), Vostok (VOS), Dronning Maud Land (DML) and Dome Concordia (DC) (Br äunlich et al. 2001), South Pole 1995 (SPO-95) and South Pole 2001 (SPO-01)[START_REF] Sowers | Records of the δ 13 C of atmospheric CH 4 over the last 2 centuries as recorded in Antarctic snow and ice[END_REF]. The numbers associated to the names on the legend are the dates (year) of the firn sampling for each site.

Table 1 .

 1 Montzka, S. A., Dlugokencky, E. J., Etheridge, D., Blunier, T., and Sturges, W. T.: A new multi-gas constrained model of trace gas non-homogeneous transport in firn: evaluation and behavior at eleven Figures Eleven firn air pumping sites. The NH sites (blue shaded) are: Devon Island (DI),

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polar sites, Atmos. Chem. Phys. Discuss.,

11, 23029-23080, doi:10.5194/acpd-11-23029- 2011, 2011.

ACPD ACPD ACPD ACPD ACPD ACPD ACPD ACPD ACPD ACPD ACPD ACPD ACPD Acknowledgements. We like to thank the team involved in the firn air sampling at NEEM site during the 2008 and 2009 field seasons. NEEM is directed and organized by the Center of Ice and Climate at the Niels Bohr Institute and US NSF, Office of Polar Programs. It is supported by funding agencies and institutions in Belgium (FNRS-CFB and FWO), Canada (NRCan/GSC), China (CAS), Denmark (FIST), France (IPEV, CNRS/INSU, CEA and ANR), Germany (AWI), Iceland (RannIs), Japan (NIPR), Korea (KOPRI), The Netherlands (NWO/ALW), Sweden (VR), Switzerland (SNF), UK (NERC) and the USA (US NSF, Office of Polar Programs).

Aside from NEEM, firn air sampling programs were supported by: at DI, IPEV (France) and the Canadian Continental Polar Shelf Project; at BI, IPEV and the British Antarctic Survey; at VOS, IPEV; at SP: US-NSF; at DC, IPEV, ENEA (Italy) and the ESF/EC program EPICA; at DML: British Antarctic Survey; at DE08; at NGRIP: Funding Agencies in Denmark (SNF), Belgium (FNRSCFB), France (IPEV and INSU/CNRS), Germany (AWI), Iceland (RannIs), Japan (MEXT), Sweden (SPRS), Switzerland (SNF) and the United States of America (NSF). We thank all participants to the field work at the 11 sites for drilling and firn air sampling operations.

LGGE δ 13 C(CH 4 ) analyses were supported by the European Commission project CRYOSTAT (EVK2-CT2001-00116) funded under the Energy, Environment and Sustainable Development Programme, 1998-2002. We would also like to acknowledge the Dutch Science Foundation (NWO) for funding (Projects: 851.30.020 and 865.07.001). This work also received funding from CNRS/INSU program LEFE. ACPD ACPD ACPD ACPD


Eloria Vigouroux-Zugasti
email: eloria.vigouroux-zugasti@u-pem.fr

Christian Bourret
email: christian.bourret@u-pem.fr

Sylvie Parrini-Alemanno
email: sylvie.parrini-alemanno@lecnam.net

From Theory to Reality Health Data Management in a Complex System

Keywords: Health, Data, Patient Records, Quality, Confidential Medical Data, Territory, Organization

With the recent promulgation of the General Data Protection Regulations (DGPS), data management is becoming a crucial strategic issue in organizations. The quality of data dissemination is of utmost importance in the healthcare environment. Indeed, medical confidentiality is closely linked to the dissemination of personal information inherent in the patient's record. Yet, how can a complex system, composed of multiple multidisciplinary actors (medical, paramedical, administrative, etc.), deal with the potential disclosure of personal data? What steps can be taken to manage this risk? How to ensure legal compliance with medical confidentiality, while ensuring the interoperability of professionals and the quality of care? To answer these questions, a case study was conducted in the Multidisciplinary Care House of Mimizan (France, Landes, New Aquitaine Region). The goal was to investigate the importance of data management for traceability of care. This medical organization is composed of medical and paramedical professionals, but also a relatively large administrative team for such an institution. Nevertheless, it manages to set up, at the initiative of the professionals, both flexible and structured processes, allowing optimal follow-up of patients, while guaranteeing respect for their personal information.

I. INTRODUCTION

The management of personal data, with the recent promulgation of the General Data Protection Regulations (GDPR -May 2018), is becoming a crucial and strategic issue for organizations. In the healthcare sector, where respect for medical confidentiality is closely linked to the dissemination of patients' personal records, data have to be managed with great care, in order to limit the risk of unfortunate disclosure or data loss and to tackle their specificity of very sensitive data (privacy challenges).

However, the current French health organization tends to evolve to a collaborative working method. For the past ten years, French health authorities have been witnessing the emergence of some new organizations of health professionals and the exponential growth of groups of (para)medical professionals, attesting the growing complexity of health organizations [START_REF] Doucet | Quality[END_REF]. This is particularly the case for Multidisciplinary/Multiprofessional Health Houses (MCHs), with 910 establishments active in France in March 2017, compared to only 240 in 2013 [START_REF] French | Access to care: health innovation promoted in French territories[END_REF]. These establishments are made complex by the number of interacting actors they involve. They also tend to rely on the notion of sharing and circulating data, especially health information about patients. By doing so, they tend to improve patients' health care and health monitoring.

Does this new type of establishment pose some risks for private heath data policy? As they are composed of many multidisciplinary actors (medical, paramedical, administrative, etc.), do not they increase the number of possible accidental disclosures or loss of confidential data? Thus, how could legal compliance guarantee medical confidentiality and manage the inherent risks, while ensuring the interoperability of professionals and the quality of care? It seems that the challenge is mainly about the ability of the French health system to increase its level of performance [START_REF] Vilcot | Quality indicators in health: Certification and evaluation of professional practices, Second release[END_REF].

To answer these questions, a case study was conducted in the Multidisciplinary Care House of Mimizan (MCHM). To do so, an exploratory qualitative approach was conducted via focus groups with the whole team of the institution and via an interview with its two managers. The goal is to establish an inventory of good practices, particularly in terms of data quality management in complex health institutions. The analytical approach presented here is based on the structural level of MCH actions, in which resources (human and material) are mobilized to ensure a good coordination for patients' care and confidential data policy [START_REF] Bartoli | Multidisciplinary Care Houses facing territorial coordination[END_REF]. MCHs are a recent and emergent phenomenon, with heterogeneous ways of working. The goal of this article is to explore one of the biggest and formalized MCH, from a exploratory point of view, in order to understand its organisation and its capacity to be considered as a model for other MCH.

The rest of this article is structured as follows. In Section II, with the overall contextualization of the study. The Section III will present the institution selected for the study, the MCHM, in order to show how it is representative of the new health institutions needed in fragile territory. In Section IV, the article will analyse the quality processes inherent in the management of this institution's data. The Section V will present the specifications of the MCHM. In Section VI, we provide details on the general lack of use of the national digital health record. We conclude the article in Section VII.

II. STUDY BACKGROUND

In this section, the study background is explained. The specific context of the current French public health context and policy are also detailed for a better understanding of the study.

A. Challenging health context

In 2014, the population density of Landes fluctuated between 2 and 45 inhabitants/km², with an aging index among the highest in the region [START_REF]New Aquitaine Regional Health Authority, Population and its characteristics in New Aquitaine[END_REF]. In 2015, 31.5% of Landes' population was over 60 years of age, a great increase compared to 2011 [START_REF]Complete File -Landes[END_REF]. According to the Regional Health Authority (RHA), in 2016, the rural population represented more than 50% of the whole Landes population. In addition, this region also has a medical demography and a density of specialists lower than regional and national averages, as well as a small number of health establishments. It also has few alternatives to the nursing homes for old people [START_REF]New Aquitaine Regional Health Authority, Population and its characteristics in New Aquitaine[END_REF]. Therefore, old people's loss of autonomy is more difficult to manage. According to RHA, 1/3 of liberal general practitioners were over 60 years old in 2017 [START_REF]New Aquitaine Regional Health Authority, Key Metrics[END_REF]. This is a very problematic issue: combined with the difficulties of attractiveness of the territory, it becomes more and more difficult to maintain the number of practitioners in this area. The RHA demographic patterns of Landes health care show a highly unfavorable public health context:

• White areas (towns located more than fifty kilometers away from a hospital emergency department), combined with an insufficient number of expert services (radiology, rheumatology, gynecology, allergology, pneumology, dermatology, etc.) • Medical desertification: unattractive territory for young (para)medical professionals (region's remoteness from large cities, low internet coverage, few cultural offers, etc.). Doctors are struggling to find successors, despite administrative provisions and facilitations offered by health authorities. • Fragile areas: unequal distribution of health professionals in areas with an imbalance between the number of potential patients and the number of doctors, as well as areas where the advanced age of patients (or the doctor) would require urgent decisions. Facing these difficulties, some political representatives try to shed some light on the issue of medical deserts: in October 2018, the mayor of a small town called Ychoux proposed to prohibit, by municipal decree, his fellow citizens from falling ill, due to the lack of medical care in its surroundings. The study was conducted in this area for its relevance concerning the challenges France will have to face in the coming years. The main problem in France is getting young medical staff to settle in countryside areas, where living standards are less attractive than urban contexts.

B. Management of de-materialized health data in a complex system

Personal data, such as medical data, is defined by the French Data Protection Act, called Loi informatique et liberté, (paragraph 2, article 2) as an information relating to a person who is physically identified or who can be identified, directly or indirectly, by reference to an identification number or to one or more elements specific to him/her [START_REF]French Data Protection Act. Loi informatique et liberté, Law[END_REF]. In addition, in order to make sense, this data must be processed. This process is defined by the same law (paragraph 3, article 2) as a transaction or set of transactions, whatever the process used [START_REF]French Data Protection Act. Loi informatique et liberté, Law[END_REF]: collection, recording, organisation, storage, modification, consultation, communication by transmission, etc. Data are also part of an exchange, characterized by the provision to several professionals, such as health staff, who are entitled to know everything about these data. Their goals are to insure the coordination and continuity of patients' medical care [START_REF] Miguel-Chamion | Protection of shared health data[END_REF].

However, the exploitation of personal data remains a sensitive subject. It directly affects the privacy of each individual [START_REF] Béranger | Data ethical value of health big data[END_REF], especially when it comes to medical data. In complex systems, such as MCH, there are several issues related to the management and to the protection of health data. From an organizational point of view, it is essential to set up procedures to secure access to data. Those procedures tend to limit the structural disorders that can affect the confidential standards of data, by establishing, for example, quality indicators. Measurement and management tools in health establishments are essential [START_REF] Vilcot | Quality indicators in health: Certification and evaluation of professional practices, Second release[END_REF]. In addition, complex systems have a large number of stakeholders, but they do not have the same level of data access authorization. It increases the risks of fraudulent or accidental access to information.

With the multiplication of MCHs, the French health sector must now face a multitude of risks related to data, which require close scrutiny of each elementary activity [START_REF] Doucet | Quality[END_REF]. These establishments are the result of a clustering of health professionals who, until now, had been working alone. However, using common resources and administrative staff lead professionals to rethink their working methods, while insisting on control and rigour. The various stakeholders in the project have to develop fundamental procedures for collaborative work. This aims at reducing and optimizing work processes [START_REF] Doucet | Quality[END_REF], while considering the topics of control and quality as the heart of these processes. Professionals, in this new context, must demonstrate that their services are delivered in a secure environment. This environment helps controlling the risks and meet the expectations/requirements of patients [START_REF] Vilcot | Quality indicators in health: Certification and evaluation of professional practices, Second release[END_REF].

C. Multidisciplinary health centre: although need for a restructured health policy -from a political point of view

MCHs are a model that catalyzes needs, from health professional, public decision makers and patient care points of view [START_REF] Bartoli | Multidisciplinary Care Houses facing territorial coordination[END_REF]. The creation of this type of institution represents the convergence of three complementary processes, identified by Autès and Dufay [START_REF] Autès | Health Care Houses and territories layout: a dynamic to share[END_REF]:

• Movement initiated by health professionals to gather their activities within MCHs and health centers. • Reflection of local officials, concerned by the management of health in their districts, involved in logics of prevention, of permanence of care, of first aid and the continuum between outpatient services and hospitals. They also care about offering external and specialized consultations to the people living in areas where there is a shortage of health practitioners; • Necessary reorganization of the supply of care due, first, to the constraints of modern medicine and pathologies and, second, to the effects induced by the anticipated decline in medical demography. From a territorial point of view, the MCHM aims at meeting the four standards of public health action: 1) maintaining a local offer, 2) guaranteeing equal access to health for all, 3) ensuring continuity of care between the primary care offer and graduated hospital care 4) and, finally, strengthening health prevention policies. For local officials, the issue is to strengthen weakened health districts and care offer [START_REF] Autès | Health Care Houses and territories layout: a dynamic to share[END_REF], by proposing long-term ways-out to solve the current problems. In addition, since MCHs are subjected to accreditation rules, by responding to quality indicators established by public health authorities [START_REF] Vilcot | Quality indicators in health: Certification and evaluation of professional practices, Second release[END_REF], they contribute to an increased performance of districts' medical management.

III. METHODOLOGICAL APPROACH

In this section, the sampling and methodological procedures are presented.

A. Why Study the MCHM?

By definition, MCHs depend on specific contexts. It is important to identify the territory's needs, to take into account the needs of its population and its state of supply. MCHM is considered as representative of this movement of territorial restructuring in the field of health, both in its conditions of implementation and in its daily functioning, structured around the interrelationships between territorial stakeholders [START_REF] Bartoli | Multidisciplinary Care Houses facing territorial coordination[END_REF]. Indeed, despite its recent implementation, it manages to meet the whole public health objectives, both mandatory and optional, imposed by the "RHA Interprofessional Agreement" contract, particularly in terms of shared information systems, which are at the heart of the challenges related to data quality. The dynamic of the creation of the MCHM was, in the first place, launched by health practitioners themselves, in reaction to the progressive desertification of their territory and the challenges it involves [START_REF] Autès | Health Care Houses and territories layout: a dynamic to share[END_REF]. The project of creating the MCHM began in 2004. The district's doctors wanted to cluster their activities in a single establishment, to pool their administrative tasks and to offer a better access to care for their patients. This approach is in line with the observations of some researchers, who state that medical desertification in rural areas has been the main motivation for the mobilization of health professionals [START_REF] Autès | Health Care Houses and territories layout: a dynamic to share[END_REF]. One of the main problems lays in Landes' unattractiveness for doctors. The mere proximity of the beach and the "sweetness of life" are not enough to attract young professionals willing to settle down. It is necessary to provide health professionals with some attractive and secure professional conditions of practice.

However, the notion of attractiveness of the project is very important here [START_REF] Bartoli | Multidisciplinary Care Houses facing territorial coordination[END_REF]. Offering a young professional an isolated practice in a small town does not have the same appeal as a long-term position in a multidisciplinary institution, in which he or she could be supervised, advised and supported by administrative services, surrounded by colleagues and supported by financial and material resources. Collegiality and plurality of perspectives make the medical practice both more reassuring and richer [START_REF] Autès | Health Care Houses and territories layout: a dynamic to share[END_REF], especially at the beginning of a career. This is the appeal proposed, in general, by MCHs and, in particular, by the case studied in this article, which is one of the biggest and dynamic MCHs in France. Its professionals have been recently asked to present their institution in the next National French Congress of MCH. This type of organizational dynamism is a movement widely desired and claimed by the younger generations of medical and paramedical professionals [START_REF] Autès | Health Care Houses and territories layout: a dynamic to share[END_REF].

Moreover, Landes is the largest region of France, with a mainly rural territory and offers most of the current and forthcoming public health services presented in the contextualisation part of this article. Having such an innovative MCH in this kind of area is an example of how to deal with public health issues in other regions in France, especially concerning the rural ones.

B. Methodological Approach and Sampling

At the beginning of the survey, the goal was to identify the organizational model and rules implemented by the MCHM's team, specially concerning working processes and data management. To do so, a qualitative approach has been chosen This method has been selected for its ability to investigate the practices and interpret the results. It considers that the "confrontation with the corpus is a necessary condition for the perception of social practices" [START_REF] Monnoyer-Smith | For a complex epistemology of information and communication sciences[END_REF]. The goal was also to confront the different points of view concerning the organizational processes. The potential divergences and discordances regarding the positions can be highlighted. Does a secretary think the same thing of the establishment than a doctor or paramedical worker? Concerning data privacy management, the heads of the MHCM in charge have been interviewed. They had to explain their choices in terms of data management policy, of coordination put in place and of emergency plans in case of unfortunate disclosure.

Regarding the questions, all the members of the MHCM staff we asked about two common topics. The first was about the daily-work and its organization, both concerning the inner-group and the relationships with the other members of the MCHM (for example: secretary-secretary, secretarymedical, etc.). The goal was to highlight relational and organizational dysfunctions. Secondly, all the staff members were asked about their own professional uses of patients' health records, in terms of access of use and of transmission. The purpose was to identify good and problematic uses.

The second questions asked for some more specific topics. The goal was to have a better understanding of each specific staff members (medical doctor, paramedical, administrative, etc.), to point out the benefits and the limits of their new work, management and organizational processes since they entered the MCHM. Four focus groups took place in December 2018, with the four specific staff members. Then, interviews were conducted in January 2018, with the head of the administrative staff and the heads of the MCHM. They all were realized in the MCHM, in the meeting room. The goal was to make the people feel comfortable and to prevent conversations from being heard by the patients or the other staffs' members. This approach seemed relevant, as it helped people to speak freely.

C. Health Records Management in the Multidisciplinary Care House of Mimizan

The MCHM brings together three main crews: doctors (8 + 2 regular substitutes + 1 trainee), paramedics (3 nurses and their collaborators, 2 physiotherapists, 2 podiatrists, 1 psycho-motor therapists, 1 dietician) and administrative staff (5 secretaries, only working for doctors, managed by an executive). Including trainee doctors and nursing staff, the sample is composed of thirty individuals involved in the daily operations of the MCHM. They are all subjected to the institution's collective agreement, in which respect for medical confidentiality is clearly enshrined. Data is managed and stored on a specific medical database software, Weda [19], which is also used by the surrounding external collaborators (pharmacies, specialists, hospitals, etc.). The choice to use the same software aims at facilitating the medical and administrative aspects concerning the caring continuum. Each member of the MCHM has secure access provided by the software. These codes are not stored on the institution's digital devices, in order to limit the risk in case of theft or hacking.

However, not all MCHM members have the same level of access to patients' records. Doctors, as well as their secretaries, have full access to all the information concerning: files, auxiliary session schedules, secure messaging, etc. This is justified by the need for doctor/doctor and doctor/secretary interoperability, for the smooth functioning of the MCHM and good patient care. At the request of a patient or a staff member, restrictions may be applied to limit secretaries' or doctors' access to some records. All patients were asked about this sharing consent.

Then come the paramedics, with a diffusion specific to each specialty. Their access is conditioned by the needs of their activity. A physiotherapist, for example, will have access to the patient's x-rays and related prescriptions; a nurse will have access to history, specialist contacts, blood test results or vaccines, depending on needs. These professionals do not have access to the content of visits, letters, prescriptions, unless some specific case discussed with the doctor. The accreditation of external professionals is aligned with the system applied within the institution, according to the needs of the patient, the activity or the specialty. Collaborative patient follow-up is governed by Multi-Professional Consultation Meetings (MPCMs), planned or impromptu, attended by all the professionals involved in the presented case. Each meeting is documented, stored via Weda and only accessible to the concerned professionals. Doctors and secretaries meet weekly to monitor performance and improve organizational quality processes. The doctors interviewed also associate these meetings with team management (trust, accountability, etc.), to ensure cohesion among all workers and to involve them in the administration of the MCHM.

IV. ANALYSIS OF DATA MANAGEMENT PROCESSES

This section is dedicated to the analysis of MCHM data management concerning patients' records. Thanks to the study, the main protagonists of this type of management tasks have been identified, such as the governance of the establishment, from a managerial point of view.

A. Data Ethics and Dissemination Quality

An organization can be defined as a set of recurring transactional programs that constitute transactional flows. They are driven by a set of conventions and rules in a given context [START_REF] Zacklad | Management as a scoping activity in a context of cooperative transactions[END_REF]. For its proper functioning, given the complexity of its transactions, it is essential to give access to the right information, at the right time, to make a selective transmission of users, in order to fight against misinformation, over-abundance and deviant uses [START_REF] Béranger | Data ethical value of health big data[END_REF]. The principle of data management is based on the ability of actors to select information and analyze it, in such a way that it is only disseminated to its legitimate recipients. The interest of this approach is twofold. On the one hand, it allows a smooth organization of sharing actions, making the institutional processes efficient. On the other hand, it makes it possible to limit the risks linked to the poor dissemination of data, thus guaranteeing respect for confidential medical records.

The ethical processing of information seems to be the starting point of the MCHM's data management strategy. Béranger defines it as a mechanism for the interpretation of data, by a person or an organization, that will lead to give a specific meaning to data [START_REF] Béranger | Data ethical value of health big data[END_REF]. By giving attention to information, by analyzing it, the heads of MCHM tend to give meaning and value to data, as well as to determine the logistics of action to be applied: censorship, global dissemination, limited dissemination, etc. In the medical sector, it is fundamental to establish a reflection on personal health data through an ethical prism "in order to [remove] doubt and control uncertainties" [START_REF] Béranger | Data ethical value of health big data[END_REF] and to manage the risks inherent in the nature of patients' records. It leads to speak of the non-maleficence nature of the MCHM's information strategy: access to data is examined according to the profile and nature of the user [START_REF] Béranger | Data ethical value of health big data[END_REF]. Data sharing is conditioned by the profile of the information receiver, ranging from full sharing to very limited access, depending on activity and needs. This improves the security, confidentiality and protection of such data [START_REF] Béranger | Data ethical value of health big data[END_REF], as well as the performance of the information management system. By analyzing the data, determining the conditions for sharing and clearly identifying the receivers, the quality of access to patients' personal data is guaranteed.

B. Informational Lean Management: no Unnecessary Information

The data processing method leads us to analyze the notion of lean in quality management. Lean School is defined as "the search for process optimization by chasing down everything that is inappropriate or superfluous" guaranteeing "performance by eliminating waste" [START_REF] Doucet | Quality[END_REF]. This method is usually applied to inventory management (0 stock), document management (0 paper), or logistics (0 unnecessary transport, 0 waiting, etc.). This can be relied to information management, in order to analyze the transaction rationalization activities [START_REF] Zacklad | Management as a scoping activity in a context of cooperative transactions[END_REF].

Indeed, the info-ethical treatment as previously mentioned tends towards a very low entropy, i.e. a degree of almost nil disorder [START_REF] Béranger | Data ethical value of health big data[END_REF]. A system in which information is transmitted without analysis increases the level of confusion, as well as the slowness of decision-making and the risks of accidental dissemination of personal records. On the contrary, in a complex system such as the MCHM, the implementation of a hierarchy in information management (doctors analyse and choose the criteria before disseminating information) makes the actions of all team members easier and more fluid, by sending them only the data that will be useful to them in the exercise of their activity. This is a kind of lean management, applied to information management. This data dissemination method tends towards the goal of "0 useless information", in order to guarantee both respect for medical confidentiality (0 information poorly disseminated), the quality of patient care (0 information missing) and the fluidity of actions (0 dysfunction linked to poor information dissemination). This information management method seems to be perfectly adapted to the performance requirements of MCHM's missions, while benefiting the daily tasks (administrative and patient care).

V. ORGANIZATIONAL PROCESSES: GUARANTEEING THE QUALITY OF DATA MANAGEMENT

In this section, the organizational processes observed during the survey will be discussed, which refers to data and patients' records management.

A. The Human Relations Theory as a Leading Light

In the MCHM, the mobilization of the whole staff tends to improve the processes' efficiency [START_REF] Doucet | Quality[END_REF]. The MCHM's management method is based on the involvement of all teams in improving the life of the institution: meetings, taking into account opinions, professional development, empowerment, etc. This method seems to be similar to the collaborative processes set up within the MCHM, although the institution does not claim any particular managerial method: unexpected discussions, weekly team meetings, festive group cohesion events, etc. This team management aims at analyzing defects and dysfunctions, and then seeking solutions [START_REF] Doucet | Quality[END_REF]. This tends to improve the overall functioning of the establishment, where, according to Zacklad, all persons involved in the transaction are in the position of (co-)director, (co-)beneficiary, (co-)recipient (principal) and (co-)recipient [START_REF] Zacklad | Management as a scoping activity in a context of cooperative transactions[END_REF]. Emphasis is placed on freedom of speech, professional responsibilities, skills of each individual and, above all, the necessary trust between employees, which is considered essential by all MCHM staff.

As Doucet points out, it is essential that the direction of quality action be collegial. This makes it possible [in particular] to respect responsibilities and involve departments [START_REF] Doucet | Quality[END_REF]. As a large number of individuals have access to the institution's health data, the use of this collaborative and collegial approach is essential to the MCHM. The increase in performance can only be achieved through the collaboration with the departments involved in this approach. By soliciting and valuing all staff members, the MCHM ensures fine relationship management, but also encourages professionalism and accountability of each individual. They also do so by regularly reminding them of the need for secrecy and rigour (formally and informally), especially concerning the performance of their daily tasks relating to patient health records. Transactional relationships lead to overcome formal/informal oppositions by insisting on their complementarity [START_REF] Bartoli | Multidisciplinary Care Houses facing territorial coordination[END_REF].

B. Leadership: Team, Quality and Performance Management

This managerial approach is in line with the objective of promoting confidentiality and trust with producers and suppliers of information, thus contributing to the control of risks and deviations of data [START_REF] Béranger | Data ethical value of health big data[END_REF]. However, for MCHM staff management to be effective, it must also deal with some leadership issues. Leadership and management of the institution must be provided by a person of influence who, thanks to his or her managerial skills is able to guarantee, effective cooperation and coordination, based on mutual trust [START_REF] Bartoli | Multidisciplinary Care Houses facing territorial coordination[END_REF]. The notions of cooperation and trust seem to be interdependent key resources for the management of complex systems. Cooperation relies on a clear commitment of each member of the group and is strengthened by trust and by the working contract [START_REF] Carnal | Federating and stimulating energies, building trust to face crisis situations[END_REF]. In a complex system, each member of the team contributes to the success of the institution goals, so it is important for all team members to be aware of the values their work involves, such as secrecy, efficiency, empathy, etc. [START_REF] Cardinal | Trust as a fundamental element of society[END_REF] It is up to the leader to make the team understand these fundamental values defended by the institution, from which ethics rules of behaviour flow. To do so, in the MCHM, many meetings are held, with the whole staff or with some subgroups (doctors-doctors, doctors-secretaries, etc.). Managing does not mean dominating. It is rather knowing how to talk to teams and how to get them to work towards a common goal [START_REF] Goleman | Emotional intelligence[END_REF]. Even if some members sometimes complain about the high number of meetings, they seem essential for the good management of the institution. Those meetings allow the team to have some feedback on the work and outline all technical or relational issues. It helps the manager to resolve the disagreements before they worsen and help the team to work with fluency [START_REF] Goleman | Emotional intelligence[END_REF].

The operational management of the MCHM is based on the involvement of the two doctors, whom will here be called P. and T. The influence they have is based on their legitimacy within the team, gained through their seniority, their involvement in the project and their ability to organize the run of the institution. The team trusts in them. Trust is built over time and in the relationships. It is a capital that the two doctors accumulated through years [START_REF] Cardinal | Trust as a fundamental element of society[END_REF]. They are well known by all the team members, sometimes for more than twenty years. They are also known for their emotional competencies [START_REF] Goleman | Emotional intelligence[END_REF], that combines feeling with objective cooperation skills. The long-term trust of the team gives P. et T. the ability to engage and influence each member of the group, which helps the team to solve complex issues [START_REF] Goleman | Working with emotional intelligence[END_REF] and aim for an outstanding performance of their work. P. and T. are complementary, both in terms of relational aspects and in the conduct of data establishment and management. However, for a good cohabitation, the roles must be clear and non-antagonistic [START_REF] Doucet | Quality[END_REF]. The risk associated is the disappearance of authority representatives. The smooth running of the institution must be based on the clear identification of authority figures, to which the staff can refer. The figure of authority also allows to the control of practices, beyond the "self-control" by the operator himself, in which skills and responsibilities are assumed by himself/herself [START_REF] Doucet | Quality[END_REF], but not objectified by an external point of view. Each member is a part of the system and they have to work toward the same goal for the institution to reach its goals and insure the quality of care [START_REF] Goleman | Emotional intelligence[END_REF].

However, this verification dimension, in order to ensure the quality of the tasks performed, is quite crucial when it comes to such sensitive data as those referred to in this article: respect for medical confidentiality, quality of transmission of information, management of the risks of records leakage, etc. Taking leadership within the MCHM then seems to represent an additional element in the performance of strategies to protect patient medical records. The leaders act here as an element of internal data protection control, which compliance must be assessed and objectified externally by a notational Data Protection Officer [START_REF] Doucet | Quality[END_REF]. This perspective can also be considered by taking as a model the Zacklad cooperative transaction logic reading grid, framework for analysing action and practice at the meso level [START_REF] Zacklad | Management as a scoping activity in a context of cooperative transactions[END_REF].

VI. GENERAL LACK OF USE OF THE NATIONAL DIGITAL HEALTH RECORD

The MCHM tends to present organizational processes in accordance with public health requirements, while following effective procedures for the management of patients' personal records. It should, however, be noted that the national digital health folder (Dossier Medical Partagé -DMP) is not integrated into any of the care management approaches within this institution. The study case tends to reveal an attitude of rejection of this instrument by MCHM staff members. They themselves state that this folder "is not designed for medical practice", although they admit the promising nature of such a tool.

"In case of emergency, the DMP becomes counterproductive. Of course, all the information about the patient is included, but it is not sorted or classified. It is up to us to find the right information and, in emergency situations, we have something more important to do than sorting information" says E., one of the MCHM doctors. They also confess that they are disturbed by the additional and timeconsuming actions required to update the patients' DMP, since this platform does not provide any automatic downloading add-ons for the software they use. It seems that the DMP system is in contradiction with the practices of MCHM professionals, with regard to their quality management processes. This notion is closely linked to the need for procedural rationality of the care action, namely an "orientation of the activity". In this orientation, the action is justified by taking into account the way in which the tools contribute to performance. It is partly defined by the quality of the realization process [START_REF] Zacklad | Management as a scoping activity in a context of cooperative transactions[END_REF]. Doctors highlight a logic "inherent in our relationship with objects and our environment, which we judge according to their adaptation to our expectations and needs" [START_REF] Doucet | Quality[END_REF]. Applying this to Doucet reasoning, it would seem that doctors judge the use of the DMP in terms of its field operability and its ability to meet the needs imposed by their profession.

However, according to their statements, data's quality processing on the DMP is incompatible with their needs. Charlotte Maday, in her article [START_REF] Carnal | Federating and stimulating energies, building trust to face crisis situations[END_REF], uses the image of deepsea fishing: throwing a net on the ocean floor, collecting information indiscriminately and presenting it to users. This image seems to be applicable to doctors' feeling towards the DMP. By presenting the "raw" data, the system is not in line with their requirements for efficient data management. It does not fit their ethical approaches or the "informational lean", the main data management strategies used within the MCHM. More broadly, DMP raises the need for coproduction concerning innovation and the necessary collaboration between producers and users to guarantee the quality of a product or a service. Bringing together the documents and data, for process governance, requires mastering the notion of a system but, above all, acting in a spirit of active collaboration [START_REF] Carnal | Federating and stimulating energies, building trust to face crisis situations[END_REF]. The main issues related to the DMP concern its digital features, ethical uses of data and the ability of professionals from various trades to collaborate on the same project. It represents a question to investigate, specially concerning the conception and the interoperability of various medical software. The goal is to ensure the performance of software and improve the quality of care.

VII. CONCLUSION

The sharing procedures introduced at the MCHM raise questions about risk assessment. In this institution, different informational and managerial strategies were put in place to secure the exchange of personal data. However, during the investigation, it seemed that the process of quality of care evaluation and "information crisis" management protocols (accidental or fraudulent disclosure, for example) were relatively minor. Since its launch, the institution does not seem to have been confronted with a crisis of this type. Its youth and its efficient management can explain this situation. Emergency protocols to resolve this type of situation are non-existent in the MCHM. It is problematical, as this implementation is one the most important principles of evaluating the quality of care in France, since the publication of the law of 31 July 1991 [START_REF] Vilcot | Quality indicators in health: Certification and evaluation of professional practices, Second release[END_REF].

In the field of health, apparently minor errors or failures can have vital consequences [START_REF] Doucet | Quality[END_REF] or endanger a health care institution and its staff. The management of the quality approach of such an institution cannot be done without a risk management component, nor a more global and formalized evaluation aspect. The measurement principles are inseparable from the principle of quality management [START_REF] Vilcot | Quality indicators in health: Certification and evaluation of professional practices, Second release[END_REF]. It, therefore, seems necessary to study this institution in greater depth in order to explore more obscure aspects of its management and to consider a global quality approach, in order to find criteria encouraging its external recognition, particularly in the management of personal data.

It would also be interesting to study the management of the MCHM through the notion of emotional intelligence. Quality and data management rely to some rational perspectives. However, the others aspects of the institution depend on human and emotional aspects. The price for the lack of emotional intelligence can end up compromising the existence of the institution [START_REF] Goleman | Emotional intelligence[END_REF]. The study highlights some minor problems, especially concerning a doctor, who sometimes awkwardly criticizes his colleagues (doctors and secretaries). Until now, it has been resolved with discretion and fluency. However, this kind of criticism precedes the loss of trust in a team work [START_REF] Goleman | Emotional intelligence[END_REF]. The MCHM does not seem to be prepared for this kind of situation. Investigating emotional intelligence as a key resource could insure the stability and the fluency of the MCHM team.

It would also be interesting to investigate, on a larger scale, other MCHs, in order to compare the results of this study with other territorial and technical contexts. The objective is also to consider the development of a single working model for all MCHs, specially concerning data privacy management. As each MCH has its own specifications (socioeconomical context, number of the staff members, equipment, competences, etc.) would it be possible and relevant to propose a single model to all of them?

TABLE I

 I

	.	DISTRIBUTION OF THE INTERVIEWED SAMPLE
	Criteria	Distribution	Number	%
	Gender	Male Female	14 13	51,9 48,1
		25-35	6	22,2
	Age	35-45 45-55	7 8	25,9 29,7
		55-65	6	22,2
		Medical doctors	11	40,7
		Paramedical staff	8	29,7
		Administrative staff	5	18,5
	Professional activity	Executive of administrative staff	1	3,7
		Executive of the
		MCHM	2	7,4
		(also doctors)