Marie Protin
email: protin@cerege.fr

Irene Schimmelpfennig

Jean-Louis Mugnier

Ludovic Ravanel

Melaine Le Roy

Philip Deline

Vincent Favier

Jean-François Buoncristiani

Aster Team

Climatic reconstruction for the Younger Dryas/Early Holocene transition and the Little Ice Age based on paleo-extents of Argentière glacier (French Alps)

Keywords: Holocene, Glaciation, Western Europe, Cosmogenic nuclides, Glacier fluctuations, French Alps, Moraine dating, Paleoclimate reconstruction, PDD modeling

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

Introduction

Investigating natural climate changes during the Holocene is relevant for assessing the impact of the current climate changes, because Holocene climate variations were similar in amplitude to the ones that are historically observed and predicted for the next few decades (e.g. [START_REF] Marcott | A Reconstruction of Regional and Global Temperature for the Past 11,300 Years[END_REF]. Mountain glaciers are known to be sensitive climate change indicators [START_REF] Oerlemans | Extracting a Climate Signal from 169 Glacier Records[END_REF], as their dynamics in the mid-latitudes, e.g. in the European Alps, depend both on summer temperature and winter precipitation variations. They thus represent a highly useful proxy for Holocene climate reconstructions. The ongoing trend of global glacier retreat, which started after the end of the Little Ice Age (LIA), in the middle of the 19 th century, is well recorded with instrumental measurements [START_REF] Leclercq | A data set of worldwide glacier length fluctuations[END_REF]. Evidence of pre-instrumental glacier fluctuations are recorded by glacial landforms, which provide the opportunity to reconstruct past glacier chronologies and examine glacier-climate interactions over a longer period. In particular, moraine deposits give valuable information about past glacier extents and dating them using in situ cosmogenic nuclides allows us to put glacier variations into a spatio-chronological framework. Over the past few years, a growing number of studies in the Alps have reported advanced glacier positions during the Late Glacial and Holocene relying on in situ-produced cosmogenic beryllium-10 ( 10 Be) moraine dating (e.g. [START_REF] Moran | Evidence of central Alpine glacier advances during the Younger Dryas-early Holocene transition period[END_REF][START_REF] Schimmelpfennig | A chronology of Holocene and Little Ice Age glacier culminations of the Steingletscher, Central Alps, Switzerland, based on highsensitivity beryllium-10 moraine dating[END_REF][START_REF] Schindelwig | Lateglacial and early Holocene dynamics of adjacent valley glaciers in the Western Swiss Alps[END_REF]. In several of these studies, the corresponding equilibrium line altitudes (ELA) were estimated (e.g. [START_REF] Baroni | Double response of glaciers in the Upper Peio Valley (Rhaetian Alps, Italy) to the Younger Dryas climatic deterioration[END_REF][START_REF] Hofmann | Post-Last Glacial Maximum glacier fluctuations in the southern Écrins massif (westernmost Alps): insights from 10 Be cosmic ray exposure dating[END_REF][START_REF] Roy | 10Be exposure dating of the timing of Neoglacial glacier advances in the Ecrins-Pelvoux massif, southern French Alps[END_REF]. As the ELA directly depends on the climate, in particular on atmospheric temperature and precipitation, reconstruction of past ELAs provides the opportunity to estimate paleoclimate conditions. Atmospheric temperature variations can be inferred using the adiabatic lapse rate or an ELA sensibility to atmospheric temperature, as has previously been done in the Alps by [START_REF] Hofmann | Post-Last Glacial Maximum glacier fluctuations in the southern Écrins massif (westernmost Alps): insights from 10 Be cosmic ray exposure dating[END_REF], Le [START_REF] Roy | 10Be exposure dating of the timing of Neoglacial glacier advances in the Ecrins-Pelvoux massif, southern French Alps[END_REF] and [START_REF] Moran | Evidence of central Alpine glacier advances during the Younger Dryas-early Holocene transition period[END_REF]. However, this approach assumes that the impact of precipitation on the glacier behavior is negligible or that the precipitation amount did not change through time, potentially leading to a bias in the deduced temperature variations. In the Alps, only few studies have attempted so far to infer precipitation changes from past glacier extents (e.g. [START_REF] Keeler | Development and Validation of a Physically Based ELA Model and its Application to the Younger Dryas Event in the Graubünden Alps[END_REF][START_REF] Kerschner | Palaeoclimate from glaciers: Examples from the Eastern Alps during the Alpine Lateglacial and early Holocene[END_REF], as disentangling the detailed contributions of both precipitation and temperature changes to glacier fluctuations is still difficult [START_REF] Solomina | Glacier fluctuations during the past 2000 years[END_REF].

In this study, we explore the frontal and lateral moraines, as well as roches moutonnées located beyond the limits of the LIA extent of Argentière glacier with the objective to present the first alpine Holocene glacier chronology based on 10 Be dating in the Mont-Blanc massif.

Potential climatic conditions corresponding to past extents of Argentière glacier are determined using two different approaches, including a PDD mass-balance model, which allows considering both precipitation and temperature variations.

Study site, geomorphologic setting and previous work on the past fluctuations of

Argentière glacier

45°55'N 6°57' )

h h-western side of the Mont Blanc massif, is the second largest glacier in the French Alps (Figure 1). In 2008, it covered a surface of ~14 km 2 with a length of almost 10 km and an altitude range spanning 3530 m to 1550 m a.s.l. [START_REF] Six | The evolution of the Italian glaciers from the previous data base to the New Italian Inventory. Preliminary considerations and results[END_REF][START_REF] Vincent | Glacier thickening and decay analysis f 50 y f f ' area, France[END_REF]. Since 2009, the tongue (7 % of the glacier area) is disconnected from the main glacier body and remains fed by an icefall located at ~2200 m a.s.l. This tongue is covered by debris since at least the middle of the 20th century (aerial photography from IGN, https://remonterletemps.ign.fr), while it was uncovered in the middle of the 19 th century according to pictorial documents from the LIA (Fontaine, 2015).

The ELA has been measured at ~2890 m a. s.l. between 1995and 2011[START_REF] Six | The evolution of the Italian glaciers from the previous data base to the New Italian Inventory. Preliminary considerations and results[END_REF]. The mean annual temperature and precipitation were 6.5°C and 1238 mm in Chamonix -Le Bouchet, the nearest weather station located at 1042 m a.s.l. for the time period 1961-1990 (Météo France) and are estimated at 1.8°C and 1783 mm at ~2000 m a.s.l. next to Argentière glacier for the time period 1979[START_REF] André | Rates of postglacial rock weathering on glacially scoured outcrops (abiskoriksgränsen area, 68°n)[END_REF](Joly et al., 2018 and personal communication of D. Joly). Snow accumulation on the glacier at 3000 m a.s.l. is known to be 3 times larger than valley precipitation due to the orographic effect on precipitation, impact of the wind and of avalanches, as the glacier is surrounded by steep slopes [START_REF] Six | The evolution of the Italian glaciers from the previous data base to the New Italian Inventory. Preliminary considerations and results[END_REF]. Climatic data began to be collected in the Alpine region in the year 1760 (temperature measurements) and in the year 1800 (precipitation) and are compiled in the HISTALP project (http://www.zamg.ac.at/histalp/; [START_REF] Auer | HISTALP-historical instrumental climatological surface time series of the Greater Alpine Region[END_REF]. The Argentière glacier catchment is mainly formed by granite from the late Hercynian along with Variscan metamorphic rocks [START_REF] Bussy | Bimodal magmatism as a consequence of the post-collisional readjustment of the thickened Variscan continental lithosphere (Aiguilles Rouges-Mont Blanc Massifs, Western Alps)[END_REF]. Numerous preserved moraine ridges and moraine remnants are visible in the catchment, close to the glacier, and downstream in the Arve valley providing evidence of the past fluctuations of Argentière glacier (Figure 2).

While it' h h LI w -known [START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF][START_REF] Payot | Oscillations des quatre grands glaciers de la vallée de Chamonix et énumération des ascensionnistes au Mont-Blanc[END_REF][START_REF] Vincent | Glacier thickening and decay analysis f 50 y f f ' area, France[END_REF], few chronological data constrain its Holocene fluctuations prior to the 17 th century [START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF][START_REF] Roy | Reconstitution des fluctuations glaciaires holocènes dans les Alpes h de la datation par isotopes cosmogéniques produits in situ[END_REF]. During the Last Glacial Maximum (LGM), the valleys around the Mont Blanc massif were glacierized, and the glacier surface reached an altitude of 2400 m a.s.l. at the location of Argentière glacier, as reconstructed from the trimline positions in the region of the Mont Blanc massif (Figure 2, [START_REF] Coutterand | Paléogéographie du dernier maximum glaciaire du Pléistocène récent de la région du Massif du Mont Blanc, France[END_REF]. During the Late-Glacial, glaciers located on the western flank of the Mont-Blanc massif were still connected as one glacier named Arve glacier, extending in the Arve valley over a distance of 30 km, where numerous and mostly lateral moraine relicts attest to multiple glacier fluctuations during that period (Coutterand and Nicoud, 2005). At one point during the retreat from the large Late-Glacial glacier extents, Argentière glacier disconnected from its neighbors Mer de Glace and Tour Glacier, which is revealed by two latero-frontal moraines sets near La Joux et near Le Planet in the Arve valley (Figure 2). Due to the lack of direct dating methods, 20 th century studies on past glacier fluctuations were often based on the comparison of ELA depressions, geomorphic moraine characteristics, pollen analyses or limiting radiocarbon dates to correlate moraines within regionally defined relative glacier chronologies like the " " f h w y . [START_REF] Maisch | Glazialmorphologische und gletschergeschichtliche Untersuchungen im Gebiet zwischen Landwasser-und Albulatal[END_REF]. Such relative dating was applied to the extent of Le Tour and Argentière glaciers and several interpretations suggest that these moraines were deposited during the Late-Glacial or Early Holocene [START_REF] Jaillet | La transition Tardiglaciaire/Holocène à travers les fluctuations du glacier du Tour (Vallée de Chamonix, Alpes du Nord françaises) [Lateglacial/Holocene transition through glacier du Tour fluctuations (upper Chamonix valley, French Alps)[END_REF][START_REF] Lucéna | Rythme des fluctuations glaciaires et détritisme alluvial h ' f ç N ) [ f rythm and postglacial alluvial detritism in high Arve valley (French North Alps)[END_REF][START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF], although there is no indication for an univocal correlation to the classical Swiss alpine nomenclature. Further evidence of Argentière glacier variations during the Holocene are provided by [START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF] and Le [START_REF] Roy | Reconstitution des fluctuations glaciaires holocènes dans les Alpes h de la datation par isotopes cosmogéniques produits in situ[END_REF]. Radiocarbon dating of subfossil organic material found in stratigraphic position in the right-lateral composite moraine (yellow dot on Figure 2) gave evidence of five glacier advances between ~4 ka and 1.2 ka, i.e. during the so-called Neoglacial, a period when the climatic conditions became more suitable for glacial advances [START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF]. In the same moraine profile, dating of detrital wood embedded-in-till 30 years later, indicates an advance during the 9 th century, similar in elevation to the LIA maxima (Le Roy, 2012). Finally, Argentière glacier reached its LIA frontal maximum extent during the 17 th century, according to several written reports about the destruction or menace of villages by the advancing glacier [START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF]. [START_REF] Gardent | Multitemporal glacier inventory of the French Alps from the late 1960s to the late 2000s[END_REF]. Geomorphologic features were mapped based on [START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF] and Le [START_REF] Roy | Reconstitution des fluctuations glaciaires holocènes dans les Alpes h de la datation par isotopes cosmogéniques produits in situ[END_REF], DEM interpretation and field observations. Dashed lines represent undated moraines, their ages are presumed from their position relative to moraines of known ages; grey lines are moraines attributed to nearby glaciers.

Methodology

Moraine mapping

The geomorphologic map presented in Figure 2 was produced using Geographic Information System (GIS). It is based on field observations along with interpretation of recent aerial images (from the IGN, 50 cm resolution) and LIDAR digital elevation models (DEM), with resolution of 1 m (Arve valley) and 2 m (Argentière catchment). The map in Figure 2 also includes moraines that were mapped in earlier studies (Le [START_REF] Roy | Reconstitution des fluctuations glaciaires holocènes dans les Alpes h de la datation par isotopes cosmogéniques produits in situ[END_REF][START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF].

Sampling and cosmogenic 10 Be ages

All samples were obtained using a cordless angle grinder, chisel and hammer (Figure 3).

Boulder samples were collected from the top of boulders embedded in the crests or on the slopes of selected moraines and bedrock samples were preferentially taken from sloping surfaces to minimize the risk of cover by vegetation, sediment or snow (Figure 3). We only sampled surfaces with minimal signs of erosion, exhibiting glacial striation when possible, and moraine boulders that were big enough (>1 m) to avoid the risk of exhumation. In total, 20 moraine boulders and 5 bedrock samples were collected. Topographic shielding was determined in the field using a clinometer.

The chemical procedure for 10 Be extraction from the rock was conducted at CEREGE (Aixen-Provence, France). Samples were crushed and sieved to the 250-500 µm fraction. Quartz was isolated from other grains first by magnetic separation, then either by repeated leaching in a H 2 SiF 6 /HCl mixture or by froth flotation, and finally by at least three sequential leaching steps in concentrated HF to remove remaining feldspar grains and atmospheric 10 Be. About 0.1 g of a 3025 ± 9 ppm in-house 9 Be carrier solution [START_REF] Merchel | Towards more precise 10Be and 36Cl f h 10-14 I f f . N . I[END_REF] was added to the purified quartz before its complete dissolution in concentrated HF. Beryllium was extracted and purified by separation on anion and cation columns and by successive alkaline precipitations of Be(OH) 2 , and the samples were then oxidized for one hour at 700°C. The final BeO oxides were mixed with Nb powder and loaded into nickel cathodes for AMS measurements. The 10 Be/ 9 Be ratios of all samples were measured at the French national AMS facility ASTER [START_REF] Arnold | The French accelerator mass spectrometry facility ASTER: Improved performance and developments[END_REF] and calibrated against in-house standard STD-11 with an assigned 10 Be/ 9 Be ratio of (1.191 ± 0.013) x 10 -11 [START_REF] Braucher | Preparation of ASTER in-house 10Be/9Be standard solutions[END_REF] using the 10 Be halflife of (1.387 ± 0.0012) x 10 6 years [START_REF] Chmeleff | Determination of the 10Be half-life by multicollector ICP-MS and liquid scintillation counting[END_REF][START_REF] Korschinek | A new value for the half-life of 10Be by Heavy-Ion Elastic Recoil Detection and liquid scintillation counting[END_REF].

Analytical uncertainties due to AMS measurement include ASTER counting statistics and stability (~0.5 %; [START_REF] Arnold | The French accelerator mass spectrometry facility ASTER: Improved performance and developments[END_REF]) and blank correction. Correction for the chemical blanks, whose 10 Be/ 9 Be ratios range between (3.21 ± 0.50) x 10 -15 and (4.87 ± 0.63) x 10 -15 , were performed by subtracting their numbers of atoms 10 Be from those of the samples calculated from the 10 Be/ 9 Be ratios (Table 1). Surface exposure ages were calculated with the CREp online calculator [START_REF] Martin | The CREp program and the ICE-D production rate calibration database: A fully parameterizable and updated online tool to compute cosmic-ray exposure ages[END_REF] applying the Lal-Stone time corrected scaling scheme, the ERA40 Atmosphere model and the Atmospheric 10 Be-based VDM for geomagnetic database (see [START_REF] Martin | The CREp program and the ICE-D production rate calibration database: A fully parameterizable and updated online tool to compute cosmic-ray exposure ages[END_REF] and f h ).

h " " 10 Be production rate of 4.11 ± 0.10 atoms 10 Be/g established by [START_REF] Claude | The Chironico landslide (Valle Leventina, southern Swiss Alps): age and evolution[END_REF] was retained here as it is the only available regional production rate. In addition, it yields results very similar to the NENA production rate [START_REF] Balco | Regional beryllium-10 production rate calibration for late-glacial northeastern North America[END_REF], which has often been used in previous studies in the Alps and has a value of 4.10 ± 0.17 atoms 10 Be/g when recalculated in CREp with the above parameters. We note that the " " [START_REF] Young | A 10Be production-rate calibration for the Arctic[END_REF]4.12 ± 0.25 atoms 10 Be/g according to CREp), also used for several alpine studies, would lead to ages younger by ~ 0.25 %. Calculated exposure ages are presented in Table 1. We did not correct the ages for snow cover effects or surface erosion, as these effects were minimized by sampling boulders least likely to have been snow covered and with minimal signs of erosion. Applying a high snow cover correction corresponding to 50 cm of snow for 6 months, as used in [START_REF] Chenet | 10Be cosmic-ray exposure dating of moraines and rock avalanches in the Upper Romanche valley (French Alps): Evidence of two glacial advances during the Late Glacial/Holocene transition[END_REF], would lead to y ≤ 8 % and assuming an erosion rate of 1 mm.kyr -1 [START_REF] André | Rates of postglacial rock weathering on glacially scoured outcrops (abiskoriksgränsen area, 68°n)[END_REF] would lead to ages older by only 1%. Nonetheless, the presented ages should be considered minimum exposure ages.

Glacier reconstruction and paleoclimatic modelling

Two approaches were used to infer paleoclimatic conditions from the extents of Argentière glacier. Both approaches are based on the simplified assumption that the glacier is in equilibrium with the climate conditions during the respective present-day reference periods detailed below.

GIS-based ELA reconstruction and paleo-temperature determination

In the first approach, 3D glacier surface reconstructions were generated for different glacier extents in the past using the ArcGIS toolbox GlaRe [START_REF] Pellitero | GlaRe, a GIS tool to reconstruct the 3D surface of palaeoglaciers[END_REF] based on the mapping of the moraines presented in Figure 2. The topography of the bedrock beneath of Argentière glacier used for the reconstruction was determined by subtracting the ice thickness [START_REF] Rabatel | Estimation of Glacier Thickness From Surface Mass Balance and Ice Flow Velocities: A Case Study on Argentière Glacier, France[END_REF] from the 25 m IGN DEM BD Alti. ELA calculations were then done using the ArcGIS toolbox developed by [START_REF] Pellitero | A GIS tool for automatic calculation of glacier equilibrium-line altitudes[END_REF] according to the Area-Altitude Balance Ratio (AABR) with a balance ratio of 1.59 and the Accumulation Area Ratio (AAR) method with a ratio of 0.67, both values representative for the Alps [START_REF] Pellitero | A GIS tool for automatic calculation of glacier equilibrium-line altitudes[END_REF][START_REF] Rea | Defining modern day Area-Altitude Balance Ratios (AABRs) and their use in glacier-climate reconstructions[END_REF]. While the AAR methods is simply based on the ratio between the surface of the accumulation area and the surface of the entire glacier, the AABR method take into account the hypsometry of the glacier [START_REF] Osmaston | Estimates of glacier equilibrium line altitudes by the Area×Altitude, the Area×Altitude Balance Ratio and the Area×Altitude Balance Index methods and their validation[END_REF] and the mass balance gradient [START_REF] Benn | Mass balance and equilibrium-line altitudes of glaciers in high-mountain environments[END_REF] and is therefore considered more reliable to approximate ELAs [START_REF] Lukas | Early-Holocene glacier fluctuations in Krundalen, south central Norway: palaeoglacier dynamics and palaeoclimate[END_REF][START_REF] Pellitero | A GIS tool for automatic calculation of glacier equilibrium-line altitudes[END_REF]. However, the AAR method has most often been used in the Alps (e.g. [START_REF] Hofmann | Post-Last Glacial Maximum glacier fluctuations in the southern Écrins massif (westernmost Alps): insights from 10 Be cosmic ray exposure dating[END_REF][START_REF] Roy | 10Be exposure dating of the timing of Neoglacial glacier advances in the Ecrins-Pelvoux massif, southern French Alps[END_REF][START_REF] Moran | Evidence of central Alpine glacier advances during the Younger Dryas-early Holocene transition period[END_REF]. Thus, for the paleoclimatic discussion we prefer the results inferred from the ELAs calculated with the AABR method and the results from the AAR method are only used for the sake of comparison with other Alpine sites. We adjusted the shear stress value along the flowlines in the ArcGIS toolbox GlaRe [START_REF] Pellitero | GlaRe, a GIS tool to reconstruct the 3D surface of palaeoglaciers[END_REF] The difference of the resulting paleo-ELAs between two periods allows for determination of the associated variation in atmospheric temperature (T) by using a constant ELA sensitivity to atmospheric temperature (S) and assuming the same precipitation as today, following the q Δ = Δ L / . The ELA sensitivity to summer temperature is nonetheless difficult to estimate and two values are used in this paper: 115 m°C -1 , which is relevant for French Alpine glaciers [START_REF] Rabatel | Changes in glacier equilibriumline altitude in the western Alps from 1984 to 2010: evaluation by remote sensing and modeling of the morpho-topographic and climate controls[END_REF]; and 72 m°C -1 , which was empirically quantified for Argentière glacier by [START_REF] Six | The evolution of the Italian glaciers from the previous data base to the New Italian Inventory. Preliminary considerations and results[END_REF] and takes into account the local effects of temperature and all meteorological parameters that influenced the snow and ice ablation.

PDD modelling

In the second approach, combinations of precipitation and temperature variations and ELAs for different glacier extents were determined by using a PDD mass-balance model coupled with a dynamic ice flow model, described in [START_REF] Blard | Persistence of full glacial conditions in the central Pacific until 15,000 years ago[END_REF]. This model has previously been used for glaciers in the central pacific by [START_REF] Blard | Persistence of full glacial conditions in the central Pacific until 15,000 years ago[END_REF], in the Andes by [START_REF] Jomelli | Irregular tropical glacier retreat over the Holocene epoch driven by progressive warming[END_REF] and in Greenland by [START_REF] Biette | Estimation des températures au début ' ' ' q y degré-jour sur le glacier du Lyngmarksbraeen[END_REF]. The topography of the watershed of Argentière glacier used for the modeling is the same used for the GIS-based reconstructions (see section 3.3.1.). The model was calibrated using the mass-balance data from 1979 to 2002

(considered here as the present-day reference period) collected at Argentière glacier by the GlacioClim Network (https://glacioclim.osug.fr) from extensive field measurements on 10 markers distributed along the glacier (5 in the ablation area and 5 in the accumulation area)

and local monthly values of temperature and precipitation for the same period (personal communication of D. Joly), inferred at 2000 m a.s.l. in the Argentière catchment from a downscaling method based on a geomatic spatial model [START_REF] Joly | Geomatic downscaling of temperatures in the Mont Blanc massif: A NEW STATISTICAL DOWNSCALING APPROACH[END_REF]. Figure 4 depicts the monthly values of temperature and precipitation of Argentière glacier averaged from 1979 to 2002 as used in the model. This interval is nearly twice as long as the 10-14 years response time of the glacier front position to a mass balance change [START_REF] Vincent | Glacier thickening and decay analysis f 50 y f f ' area, France[END_REF] and is long enough to fade out the inter-annual variability. In addition, the glacier length at the beginning of this period is very similar to that at the end, as it includes an advance of the glacier followed by an equal retreat (Figure 5). This consolidates the assumption that the glacier was roughly in equilibrium with the mean climatic condition during this period. This period is put into a broader context and compared to the variations of Argentière glacier since 1800 in Figure 5. The atmospheric lapse rate of temperature and precipitation are fixed at 0.65°C/m and 80mm/100m/year, respectively. This precipitation lapse rate matches best the field data taking into the range of the precipitation lapse rate between precipitation in the valley and at high altitude in the MMB of 52mm/100m/years [START_REF] Corbel | Glaciers et climats dans le massif du Mont-Blanc[END_REF] as well as the variable ratio between valley precipitation and winter accumulation on Argentière glacier [START_REF] Six | The evolution of the Italian glaciers from the previous data base to the New Italian Inventory. Preliminary considerations and results[END_REF] equivalent to a lapse rate of ∼95mm/100m/years. precipitation in the west part of the Alps from the HISTALP time series [START_REF] Auer | HISTALP-historical instrumental climatological surface time series of the Greater Alpine Region[END_REF] and (c) front variation of the Argentière glacier -the origin of the axis is arbitrary (1818-1880[START_REF] Payot | Oscillations des quatre grands glaciers de la vallée de Chamonix et énumération des ascensionnistes au Mont-Blanc[END_REF]in Fontaine, 2015;1850[START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF]1880[START_REF] Alley | The Younger Dryas cold interval as viewed from central Greenland[END_REF]: Francou and Vincent, 2007;[START_REF] Alley | The Younger Dryas cold interval as viewed from central Greenland[END_REF][START_REF] Vincent | Glacier thickening and decay analysis f 50 y f f ' area, France[END_REF] Red and blue curves represent 10-years running means.

Period of reference of the climatic data of Argentière glacier [START_REF] Rabatel | Changes in glacier equilibriumline altitude in the western Alps from 1984 to 2010: evaluation by remote sensing and modeling of the morpho-topographic and climate controls[END_REF]. Furthermore, the length of the modeled glacier is between 600 and 300 m shorter than that of Argentière glacier between 1990 and 2001. As the lower part of the Argentière glacier is covered by debris from before the middle of the 20 th century, and termini of debris-covered glaciers, like the Miage glacier in the Mont Blanc massif [START_REF] Smiraglia | Recent areal and altinietric variations of Miage Glacier (Monte Bianco massif[END_REF], are often less responsive to climatic variability than non-covered glaciers [START_REF] Scherler | Spatially variable response of Himalayan glaciers to climate change affected by debris cover[END_REF], this might be the reason why the model predicts a shorter length. Nonetheless, due to the excellent agreement between calculated and measured mass balance (Figure 6), we consider that the above calibration of the model is suited for modeling the past extents of the glacier. For each investigated extent, the model considers all potential combinations of precipitation and temperature conditions that lead to a match of the front of the modeled paleo-glacier with the position of the corresponding frontal moraine mapped in the field.

ELAs correspond to the altitudes where the glacier mass balance is zero. For each glacier extent, ELAs vary over a range of more than 100 m, due to the large range of assumed precipitation conditions (between 0 and 2 times that of the reference period).

Results

Description of the geomorphological evidence

Figure 2 presents a moraine map of the Argentière catchment. The frontal moraines located around 1.5-2 km downstream of the present glacier front (purple moraines in Figure 2) have been assigned by [START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF] to four LIA advances between the 17 th century and 1850 based on analysis of historical written documents and paintings combined with lichenometry dating.

On both lateral sides, the LIA advances are represented by massive composite moraines of up

80 h h ≥ 1 k h.
e between the ~1850 frontal moraine and the current front, representing the generally gradual retreat of the glacier since the end of the LIA (pink moraines in Figure 2). Immediately to the north, slightly outboard of the right-lateral LIA composite moraine, four short ridges of so far unknown age are preserved (orange moraines in Figure 2). This area, hereafter calle "Crèmerie", is covered by a dense conifer forest, but the morphology of the ridges is noticeable on the DEM and attested by a few disseminated moraine boulders.

Further upstream near the present-day Argentière glacier icefall, multiple ridges of lateral moraines are preserved. On the left-lateral side, in the "Lognan" h prominent moraine, ~15 m-high and 700 m-long is attributed to the LIA (Figure 2). Downstream in the Arve valley near La Joux, relicts of a latero-frontal moraine set are preserved (dark blue moraines in Figure 2). These moraines, smooth and covered by conifer trees, were studied and mapped in detail by [START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF] and [START_REF] Lucéna | Rythme des fluctuations glaciaires et détritisme alluvial h ' f ç N ) [ f rythm and postglacial alluvial detritism in high Arve valley (French North Alps)[END_REF] "L h ff II" "L J x" [START_REF] Lucéna | Rythme des fluctuations glaciaires et détritisme alluvial h ' f ç N ) [ f rythm and postglacial alluvial detritism in high Arve valley (French North Alps)[END_REF]

Moraine and bedrock exposure ages

All 10 Be exposure ages are listed in Table 1 and depicted in Figure 7. In the text, individual exposure ages are presented with their 1 analytical errors; in addition, Table 1 shows the 1 external errors, including the 10 Be production rate error. Before calculating the mean ages of the glacial landforms, each age population was subject to a 2 test (2 ) to identify any potential outliers. The landform ages correspond to the arithmetic means of the sample ages and the uncertainties to their standard deviations (in the text and figures for internal comparison); Table 1 also shows the errors that include the 10 Be production rate errors.

Probability plots of all boulder and moraine mean ages are illustrated in Figure 8.

Five samples from La Joux area yield ages between 13.2 ± 0.4 ka (LJX-17-5), corresponding to an isolated boulder in front of the outmost moraine (J1), and 9.7 ± 0.3 ka (LJX-17-4), which is the only age from J1 moraine. The mean age for the J2 moraine is 10.9 ± 0.9 ka (n =

2), after discarding sample LJX-17-1 (51.9 ± 2.7 ka) as an outlier. This latter boulder surface was most likely affected by isotope inheritance from earlier periods of exposure to cosmic radiation. Ages for the J1 and J2 frontal moraines are not in stratigraphic order, but the J1 age relies upon only one sample, which might have been underestimated due to surface cover by vegetation, erosion or anthropogenic impact, as the La Joux area is located in an area covered by forest, close to a village. Samples from the Crèmerie area have been discarded (D) as the current were <1µA and blank corrections >50%. In the Lognan area, the three bedrock samples taken from roches moutonnées slope between Rognons glacier and Argentière glacier yield ages of 11.0 ± 0.4 (ARG-15-7), 12.5 ± 0.5 (ARG-15-6) and 11.0 ± 0.4 ka (ARG-15-5). From the moraine sequence located directly to the north, we dated three moraines (L1-L3), two of which lie very close together (L2, L3;

Figure 7) The outmost one (L1) yields five boulder ages between 12.2 ± 0.6 and 10.6 ± 0.4 ka, with a mean of 11.7 ± 0.7 ka, after discarding ARG-16-10 (10.1 ± 0.6 ka) as an outlier.

Three boulders were dated from L2, giving ages between 10.3 ± 0.7 and 10.7 ± 0.3 ka and a mean age of 10.4 ± 0.2 ka. L3 yields five ages between 10.0 ± 0.3 and 10.9 ± 0.3 ka with a mean age of 10.4 ± 0.4 ka, after removing ARG-16-5 (17.4 ± 1.5 ka) as an outlier. These glacial landform ages are in good stratigraphic order. The similar 10 Be ages of the laterofrontal moraines in the La Joux area (between ~10.9 ka and 9.7 ka) and of the lateral moraines in the Lognan area (between ~11.7 ka and 10.4 ka) implies that the deposition of these moraines most likely corresponds to the same glacier advances or stillstands. Two additional bedrock surfaces were sampled next to the Lognan moraines. One on the foot of the bedrock slope at the southern extremity of L1 was dated at 10.4 ± 0.5 ka (ARG-16-8), and another one located between L1 and L3, taken from the flat ground, was dated at 10.0 ± 0.4 ka (ARG-16-14). Even if these two ages are statistically indistinguishable from the mean ages of the moraines that framed them and the low number of bedrock ages does not allow a robust comparison, they apparently tend to be slightly younger than the moraines. This could be explained by degradation and erosion of the samples (in the case of ARG-16-8) and sediment, vegetation and/or snow cover, in particular for ARG-16-14 as it is on ground level, which in both cases results in an underestimation of the ages.

The batch of the five samples taken in the Crèmerie area (C1 and C2 moraines) was subject to a failure during the chemical preparation of the samples, leading to low-quality measurements. Only sample ARG-17-2 from moraine C1 was retained due to sufficiently high 9 Be currents (>1 µA) during the AMS measurements, and yielded an age of 0.9 ± 0.2 ka.

However, as this is only a single moraine age with high analytical error and therefore does not allow us to reliably interpret the deposition age of the moraines in the Crèmerie area, we do not consider it further.

Based on presented ages and on the mapping of all preserved moraines, we reconstruct the extents of the glacier during the YD/EH transition and the Little Ice Age maximum in comparison with that of the year 2008, as shown in Figure 9.

ELA determination

The ELAs resulting from the different methods described in section 3.2 are presented in Table 2. The contours of the ice surface resulting from the 3D reconstructions using the ArcGIS toolbox GlaRe and used for the ELAs calculations are represented in Figure 9 (blue areas).

According to the GIS-based reconstruction method, the ELAs computed for the glacier extent corresponding to the LIA maximum (17 th century) and the moraine J2 (∼11 ka) using the AABR method are 2738 m and 2523 m a. methods and 1979-2002 for the PDD modeling), the LIA maximum (17 th century) and the J2 moraine (~11 ka; YD/EH transition). For the AABR method a Balance ratio of 1.59 (Rea, 2009) is used and for the AAR method a ratio of 0.67 [START_REF] Gross | Methodische Untersuchungen über dieSchneegrenze in alpinen Gletschergebieten[END_REF], both representative for the Alps. For the PDD model, ELA values are inferred with the same precipitation condition as today.

Paleoclimatic results

Temperature results from the GIS-based reconstructions

The temperature differences inferred from the GIS-based ELA reconstructions (AABR and AAR methods) between ~11 ka, the LIA maximum (17 th century) and the year 2008 are presented in Table 3. The 128-m rise of the ELA between the LIA maximum and the year 2008 inferred from the AABR method is equivalent to a +1.1°C difference in summer temperature, according to the ELA sensitivity to summer temperature of 115 m°C -1 [START_REF] Rabatel | Changes in glacier equilibriumline altitude in the western Alps from 1984 to 2010: evaluation by remote sensing and modeling of the morpho-topographic and climate controls[END_REF]. Using the local ELA sensitivity of 72 m°C -1 [START_REF] Six | The evolution of the Italian glaciers from the previous data base to the New Italian Inventory. Preliminary considerations and results[END_REF], it is +1.8°C. The temperature difference between ~11 ka and the year 2008 (ELA-rise of 331 m), using the same two ELA temperature-sensitivity values as above, is +3°C and +4.8°C, respectively.

For the sake of comparison with other studies from the Alps, we also give the results from the AAR method, noting that the ELA-rise is traditionally estimated with reference to the LIA maximum glacier extent. According to this approach, our reconstruction leads to an ELA-rise between ~11 ka and the LIA maximum of 105 m, which corresponds to +0.9°C and +1.4°C, respectively. Between ~11 ka and 2008, this approach gives a difference of +1.3°C and +2.1°C, respectively, equivalent to an ELA rise of 153 m. And between the LIA maximum and 2008, the ELA-rise is 48 m, corresponding to a temperature difference of +0.4°C and +0.7°C, respectively. These latter results seem to be underestimated when comparing them to the values inferred from the measurements at the beginning of the 19 th century (~+1.0°C; [START_REF] Auer | HISTALP-historical instrumental climatological surface time series of the Greater Alpine Region[END_REF]; Figure 5), a period when the glacier was even slightly smaller than during the 17 th century. On the other hand, the temperature results from the AABR method (+1.1°C/+1.8°C) are coherent with the instrumental data. Table 3: Comparison of the temperature differences inferred from the ΔELA calculated from the AABR and AAR methods (presented in Table 2) using two different ELA sensitivity to temperature: 115 m°C -1 [START_REF] Rabatel | Changes in glacier equilibriumline altitude in the western Alps from 1984 to 2010: evaluation by remote sensing and modeling of the morpho-topographic and climate controls[END_REF] on the left and 72 m°C -1 [START_REF] Six | The evolution of the Italian glaciers from the previous data base to the New Italian Inventory. Preliminary considerations and results[END_REF] on the right. LIA refers to the LIA maximum (17 th century).

Paleoclimatic results from the PDD modeling

Applying the PDD modeling approach, we determined the potential combinations of precipitation and temperature conditions corresponding to each investigated glacier extent.

The glacier extents at four different dates were investigated (see Figure 2 to visualize the extents): the years 1850 and 1820, for which the glacier extents and regional climate conditions are well known, the 17 th century (LIA maximum) and the extent at ~11 ka using the moraine J2 as the frontal limit. The modeling gives an infinite number of combinations of temperature and precipitation conditions that explain the frontal moraine position at the four investigated dates. The curves in Figure 10 represent these combinations, considering temperatures between 0°C and 8°C below that of the reference period and precipitation amounts between 0 and 2 times that of the reference period. This figure also

shows the range of ELAs resulting from the model for each of the four glacier extents. The

ELAs increase with precipitation. Climate influence on Argentière glacier is explored through modeling of its extents at the end of the LIA, when climatic evolution is already instrumentally recorded. As the instrumental climatic data used for comparison with our results do not cover the 17 th century, only the results of 1850 and 1820 are subject to discussions of the LIA paleoclimate. Based on the data collected in the HISTALP project (http://www.zamg.ac.at/histalp/; [START_REF] Auer | HISTALP-historical instrumental climatological surface time series of the Greater Alpine Region[END_REF], we estimate the annual temperature for the years 1850 and 1820. We then deduce the precipitation, which is more likely to vary locally, from the PDD model. All values are calculated relative to the 1979-2002 wh h h " -y" f iod used in the PDD model (see section 3.2). A shift of 10-14 years between the extraction of the temperature value and the date of the studied extent has been applied in order to take into account the ' response time [START_REF] Vincent | Glacier thickening and decay analysis f 50 y f f ' area, France[END_REF]. The measured temperature differences compared to the period of reference are around -1.4°C for 1850 and around -1.0°C

for 1820 (Figure 5). Thus, colder conditions prevailed when the glacier was shorter, in 1850.

According to these temperature differences and the temperature-precipitation relationships in The relatively high potential temperature ranges reflect the uncertainty arising from the choice of the value for the ELA sensitivity to temperature in the first approach and from the range of possible precipitation amounts in the second approach. can be distinguished (among them J1 and J2). The similarity of the moraine and bedrock ages as well as the smooth and low morphology of the moraines suggest that the glacier did not retreat far up-valley between the moments of moraine deposition and that these moraines correspond to periods of glacier stillstands during the deglaciation rather than to massive readvances. Finally, the innermost moraine ages and the bedrock ages in the Lognan area imply that the glacier definitively retreated from its Early Holocene extent at ~10.4 ka ago.

Further evidence of advanced extents of Argentière glacier during the Late Holocene comes from the study by [START_REF] Bless | Beträge zur Spät und Postglazialen Geschichte der Gletscher im Nordöstlichen Mont Blanc Gebiet[END_REF] who suggested five advances of Argentière glacier between ~4 ka and ~1.2 ka, based on radiocarbon-dated subfossil wood found in the right-lateral moraine outcrop (location in Figure 2). Multiple advances during this period were also reported for other glaciers in the Mont-Blanc massif (e.g. [START_REF] Deline | Glacier fluctuations in the western Alps during the Neoglacial, as indicated by the Miage morainic amphitheatre (Mont Blanc massif, Italy)[END_REF][START_REF] Roy | Calendar-dated glacier variations in the western European Alps during the Neoglacial: the Mer de Glace record, Mont Blanc massif[END_REF]. In particular, the numerous dendrochronologically-dated advances of the neighbor Mer de Glace between ~3.5 ka and 0.7 ka ago (Le [START_REF] Roy | Calendar-dated glacier variations in the western European Alps during the Neoglacial: the Mer de Glace record, Mont Blanc massif[END_REF]; location in Figure 1), support the hypothesis of Late Holocene advances of Argentière glacier. However, considering that so far none of the preserved and dated moraines gave a Late Holocene age that pre-dates the LIA, we assume that the Late Holocene extents of Argentière glacier were smaller than those during the LIA maximum.

Paleoclimatic interpretations

Comparison with previously glacier-derived paleoclimate reconstructions from

Argentière glacier and other sites in the Alps

The results of the PDD modeling for the 1820 and 1850 extents indicate that precipitation was higher in 1820 than in 1850. Regionally higher precipitation in 1820 was also recorded in the western part of the Alps according to the HISTALP annual precipitation time series (Figure 5), but the difference in precipitation amount between 1850 and 1820 is only of ~10%, against ~20% according to our modeling. Our results are consistent with the conclusions from previous PDD modeling of Argentière glacier [START_REF] Vincent | Solving the paradox of the end of the Little Ice Age in the Alps[END_REF], which explains observed glacier advances during the period 1760-1830 with winter precipitations higher by at least 25% than the 20 th century average, while summer temperature had not decreased. They also attribute the subsequent retreat of the glacier to a decrease in winter precipitation. Even if our findings are not directly comparable, as our modelling only allows us to consider the annual and not the seasonal climate variations and [START_REF] Vincent | Solving the paradox of the end of the Little Ice Age in the Alps[END_REF] based their model on less cooling than we do here, we can still notice that the trend is the same, i.e. higher precipitation in 1820 compared to 1850 explains the bigger glacier extent. Given that the 19 th century maximum of bigger glaciers in the Swiss Alps occurred in 1850-1860 rather than in 1820 [START_REF] Holzhauser | Glacier and lake-level variations in westcentral Europe over the last 3500 years[END_REF], the glacier size and local variations in precipitations during the LIA could explain the detailed differences in the behavior of Argentière glacier compared to smaller glaciers in other Alpine regions. These results illustrate that ignoring the role of precipitation might lead to a first-order approximation of past temperature conditions. Our results also show that the impact of local precipitation variations on mountain glacier dynamics superimposes on those of large scale temperature variations and can thus explain the local differences in the behavior of glaciers from different parts of a massif, like the Alps, and the small fluctuations of a glacier during one glacial stadial, like the LIA.

Temperature reconstructions for the YD/EH transition using the AAR method have previously been performed at glacier sites in the Alps. [START_REF] Moran | Evidence of central Alpine glacier advances during the Younger Dryas-early Holocene transition period[END_REF] reconstructed from the extents of two glaciers in the Eastern Alps that summer temperatures were 1.5°C lower during the YD/EH transition than in the mid 20 th century, which is in good agreement with the difference of 1.3°C/2.1°C inferred from the extents of Argentière glacier during the YD/EH transition and the year 2008 when using the AAR method. These results are also coherent with the findings of [START_REF] Hofmann | Post-Last Glacial Maximum glacier fluctuations in the southern Écrins massif (westernmost Alps): insights from 10 Be cosmic ray exposure dating[END_REF] who inferred a temperature difference of 1.5°C

between the YD/EH transition and the LIA in the westernmost French Alps. Nonetheless, due to the extremely simplified assumptions on the glacier geometry of the AAR method (section 3.3.1), we believe that temperature reconstructions based on this approach should be taken with caution. The coherence between the relative temperature reconstructed from the local LIA maximum glacier extent and the one measured at the end of the LIA (section 4.4.1) makes us indeed confident that the AABR method is more reliable than the AAR method when inferring paleotemperatures from ELA reconstructions.

Comparison with paleoclimate results from independent proxy records

Comparison of our precipitation range assumptions for the YD/EH transition (-45% to +10%

of the present precipitation amount) with independent proxy records is difficult. Given that precipitation can significantly vary locally, it would be ideal to consider a local precipitation estimate in or near the Mont-Blanc massif for this period. However, to our knowledge this does not exist. The complexity of the precipitation variability during the Younger Dryas and the Early Holocene has indeed been underlined by [START_REF] Magny | Quantitative Reconstruction of Younger Dryas to Mid-Holocene Paleoclimates at Le Locle, Swiss Jura, Using Pollen and Lake-Level Data[END_REF]. Recent global climate simulations combined with proxy-based temperature reconstructions suggest that the Younger Dryas was considerably drier and the Early Holocene was less dry in Central Europe than the preceding Allerod period [START_REF] Renssen | The global hydroclimate response during the Younger Dryas event[END_REF], but no quantification of the precipitation conditions relative to the present is available.

Alpine and European temperature reconstructions for the Younger Dryas and Early Holocene based on independent proxies are more frequent. However, the range of reconstructed annual and summer temperatures for the Younger Dryas is large, it varies from 6 to 2°C below modern values when inferred from records of pollen and cladocera assemblages from Gerzensee in the North-alpine foreland in Switzerland [START_REF] Lotter | Younger Dryas and Allerød summer temperatures at Gerzensee (Switzerland) inferred from fossil pollen and cladoceran assemblages[END_REF], investigation of stalagmites in Hölloch cave in the German Alps [START_REF] Wurth | The Younger Dryas and Holocene climate record of a stalagmite from Hölloch Cave(Bavarian Alps, Germany[END_REF] or chironomid records from a paleolake in the Central Swiss Alps [START_REF] Ilyashuk | Lateglacial environmental and climatic changes at the Maloja Pass, Central Swiss Alps, as recorded by chironomids and pollen[END_REF]. Based on high-resolution oxygen isotope records, the beginning of the Holocene is associated with an abrupt temperature rise on regional and hemispheric scale [START_REF] Alley | The Younger Dryas cold interval as viewed from central Greenland[END_REF][START_REF] Schwander | Oxygen isotopes of lake marl at Gerzensee and Leysin (Switzerland), covering the Younger Dryas and two minor oscillations, and their correlation to the GRIP ice core[END_REF].

Early Holocene temperature reconstructions in the region of the Alps yield, similar to those for the Younger Dryas, a large range of values depending on the used proxy. For example, the chironomid record in the Swiss central Alps indicates ~1-4°C above the present July air temperatures for the very beginning of the Holocene [START_REF] Ilyashuk | Lateglacial environmental and climatic changes at the Maloja Pass, Central Swiss Alps, as recorded by chironomids and pollen[END_REF], while a second chironomid record, also from the Swiss Alps, indicates ~1-1.5°C below it [START_REF] Heiri | A chironomid-based Holocene summer air temperature reconstruction from the Swiss Alps[END_REF].

Reconstruction from pollen data indicates an annual anomaly relative to the present of as low as -4.5°C (around 12-11 ka) for the central-western part of Europe [START_REF] Davis | The temperature of Europe during the Holocene reconstructed from pollen data[END_REF] and summer temperatures of 4.5-5°C below those of the present at Gerzensee [START_REF] Lotter | Younger Dryas and Allerød summer temperatures at Gerzensee (Switzerland) inferred from fossil pollen and cladoceran assemblages[END_REF].

The temperature range inferred for the YD/EH transition from our PDD modeling of -5.5°C to -3.6°C and from the ELA reconstruction with the AABR method of -4.8°C/-3.0°C, agrees with the coldest results from alpine proxy records for this period (e.g. [START_REF] Davis | The temperature of Europe during the Holocene reconstructed from pollen data[END_REF][START_REF] Lotter | Younger Dryas and Allerød summer temperatures at Gerzensee (Switzerland) inferred from fossil pollen and cladoceran assemblages[END_REF], reinforcing our results for the western Alps.

However, the large divergence between the paleo-temperature reconstructions depending on the method and parameters used highlights that further investigations are necessary to refine methods that aim at inferring paleo-climate conditions from past glacier extents and to complete the here presented findings.

Conclusions

Our new Holocene chronology for the Argentière glacier based on 29 cosmogenic 10 Be cosmogenic dates of moraines and bedrock suggests that Argentière glacier retreated from its large Late-Glacial extent during the Younger Dryas/Early Holocene transition, around 11.7 ka, and that this retreat was interrupted by several stillstands during ~1 ka, followed at ~10.4 by the final glacier retreat to within the LIA limits. We do not have any evidence of glacial advances until the Late Holocene.

Climate reconstruction corresponding to two different glacier extents during the LIA, using a PDD model coupled with a dynamic ice flow model, highlights the influence of local precipitation changes, superimposed on the dominant impact of temperature, on the detailed glacial fluctuations of Argentière glacier. This suggests that disregarding the role of precipitation might lead to first-order temperature approximations when reconstruction paleoclimate conditions from past glacier extents.

The reconstruction of the climatic conditions corresponding to the YD/EH transition extent of the glacier using the PDD model and a simpler approach that only considers the impact of summer temperature on the reconstructed ELAs yield comparable results. The results from the PDD model suggests a temperature difference range of -5.5°C to -3.6°C compared to the present-day period . This agrees with earlier paleoclimate reconstructions from pollen records for the same period, but seems to be quite cold in comparison with the results from other proxy studies and another simple approach of glacier-based temperature reconstruction. The large differences in temperature reconstructions from the various paleoclimate studies and the scarcity of paleo-precipitation records for the Younger Dryas and the Early Holocene highlight the need of additional efforts in investigating the paleoclimatic conditions for these periods.

IN / N h N h h h " j h q ' x " f h " q ' x " -CEREGE action and IRD. We thank Benjamin Chandler and one anonymous reviewer whose relevant remarks have helped to improve this manuscript.

Figure 1 :

 1 Figure 1 : General overview of the study area. (a) Location of the Mont Blanc massif (red

Figure 2 :

 2 Figure 2 : Geomorphic map of the study area with individual sample locations on the 5 m

Figure 3 :

 3 Figure 3 : Photographs of sample sites at Argentière glacier. Example of (a) moraine boulder

  by comparing the ELA calculated for the 2008 extent of Argentière glacier to the mean ELA measured in the field between 1995 and 2011 (∼2890 m, Six and Vincent, 2014). The best estimate are found for a shear stress value of 150 kPa and an automatic shape factor. The calculated ELAs for the 2008 extent are 2866 m using the AABR method and 2801 m using the AAR method. These two values are close, yet inferior, to the measured ELA. It has to be noted that in 2008 the glacier was not in steady-state, therefore the measured ELA does not reflect an equilibrium position unlike the calculated values, which hinders us from accurately fitting both and might explain the difference between them.

Figure 4 :

 4 Figure 4 : Climatic data of Argentière glacier between 1979 and 2002 at ∼ 2000 m a.s.l.. Blue

Figure 5 :

 5 Figure 5 : (a) Annual temperature anomalies (reference period 1979-2002); (b) annual

Figure 6

 6 Figure6shows the correlation between observed and calculated mass balance of Argentière glacier. This best fit (R 2 = 0.97) was obtained using the least mean square optimization on the

Figure 6 :

 6 Figure 6: (a) Comparison between observed mass balance(1979[START_REF] André | Rates of postglacial rock weathering on glacially scoured outcrops (abiskoriksgränsen area, 68°n)[END_REF] Glacioclim Network)

  Only a few tens of meters outboard, two dissected main ridges and several subridges lie tight together (among them L2 and L3 in Figure2), and another dissected ridge is preserved about 150-200 m further outboard (L1 in Figure2). According to their positions, these ridges are pre-LIA moraine relicts but were undated until now. They display a smoother morphology than the massive LIA moraine, but are located around the same altitude, and exhibit several boulders suitable for sampling. At their upstream (southern) ends, these moraines abut against a steep and up to a 150 m-high bedrock outcrop, which testifies to past glacial cover owing to numerous roches moutonnées (Figure3). This roche moutonnée area lies between the current terminus of Rognons glacier and the left-lateral bank of Argentière glacier and is framed by two moraines deposited by Rognons glacier during its retreat. A similar moraine sequence pattern is observed on the north-eastern bank of the glacier. Moraines located further to the west of the pre-LIA deposits in the Lognan area (grey moraines on Figure2) are not considered as moraines built by Argentière glacier. They were most likely deposited by the Lognan glacier, a smaller nearby glacier. This is suggested by their composition of gneiss boulders, transported from the Lognan glacier catchment, whereas the boulders embedded in the sampled moraines are granitic according to the main lithology of the Argentière glacier catchment.

  , corresponding to J1 and J2 moraines respectively in Figure 2. Furthermore, remnant of at least one other moraine is located between J1 and J2. Some boulders are embedded in these moraines. A set of lateral ridges are observed along the right-lateral valley flanks on the NW side of the Argentière glacier catchment, especially south of Le Planet. North of these moraines, another set of latero-frontal moraine relicts deposited by the neighbor Tour Glacier are visible near Le Planet (Figure 2).

Figure 7 :

 7 Figure 7: Individual 10 Be exposure ages (white boxes) and mean 10 Be ages (colored boxes) of

Figure 8 :

 8 Figure 8 : Summed probability plots (colored curvescolors refer to the legend of Figure 2) of 10 Be boulder ages from Argentière glacier. Probability curves of individual ages (black

Figure 9 :

 9 Figure 9 : Black curves represent the reconstruction of past extents of the Argentière glacier, based on mapping of the preserved moraines and interpretation of 10 Be dating, for the (A) Younger Dryas/Early Holocene transition (~11 ka -J2 moraines) (B) LIA maximum (17 th

Figure 10 :

 10 Figure 10 : Paleoclimatic reconstructions of the Argentière glacier for the YD/EH transition (blue) and the 17 th century (orange), 1820 (purple) and 1850. (pink) glacier extent.

Figure 11 ,

 11 Figure11, precipitation amounts were lower by ~15% in 1850 and higher by ~10% in 1820

Figure 11 :

 11 Figure 11 : Same as Fig. 10, but for the YD/EH transition (blue), 1820 (purple) and 1850

  s.l., respectively. With the AAR method, they are 2753 m and 2648 m a.s.l., respectively. The ELA rise between the two extents is of 215 m with the AABR method, while it is 105 m with the AAR method. The modeling of the same extents using the PDD model, assuming the same precipitation as today, leads to ELA values of 2753 m for the 17 th century and 2442 m a.s.l. for the ~11 ka period. The associated ELA rise between the two extents is 311 m.

			ELA (m a.s.l.)		ΔELA (m)
		present	LIA	~11 ka (J2 moraine)	LIA -present ~11 ka -present	11 ka -LIA
	AABR	2866	2738	2523	128	343	215
	AAR	2801	2753	2648	48	153	105
	PDD	2940	2753	2442	187	498	311

Table 2 :

 2 Comparison of ELA calculations using the AABR and AAR methods and the PDD modeling for Argentière glacier for the present-day (i.e. year 2008 for the AABR and AAR

Acknowledgements

This study is part of ANR project 14-CE03-0006 VIP Mont-Blanc. We thank Laëtitia Léanni (CEREGE) for support during sample chemistry, Pierre Jégot and Jules Fleury (CEREGE) for help during ELA determination and Daniel Joly and Benjamin Pohl for sharing temperature and precipitation data. The 2015 DEM of Argentière glacier catchment has been acquired within the project ISOTHERM led by Antoine Rabatel (Univ. Grenoble Alpes, IGE) founded by EUFAR (EUropean Facility for Airborne Research). We also thank the IRSTEA for the Arve valley DEM. The ASTER AMS national facility (CEREGE) is supported by the