Philip Meister
email: philip.meister@awi.de

Anne Alexandre

Hannah Bailey

Philip Barker

Boris K Biskaborn

Ellie Broadman

Rosine Cartier

Bernhard Chapligin

Martine Couapel

Jonathan R Dean

Bernhard Diekmann

Poppy Harding

Andrew C G Henderson

Armand Hernandez

Ulrike Herzschuh

Svetlana S Kostrova

Jack Lacey

Melanie J Leng

Andreas Lücke

Anson W Mackay

Eniko Katalin Magyari

Biljana Narancic 19

Cécile Porchier

Gunhild Rosqvist

Aldo Shemesh

Corinne Sonzogni

George E A Swann

Florence Sylvestre

Hanno Meyer

A global compilation of diatom silica oxygen isotope records from lake sediment -trends, and implications for climate reconstruction

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

Introduction

Scientific background

Oxygen isotopes are ubiquitous within the global water cycle and are among the best (hydro)climate proxies worldwide as a result of their potential quantitative interpretability. The most abundant isotope 16 O and the rarer isotope 18 O are subject to fractionation during water phase transformation and transport processes (Fig. 1). As a result, the relative abundance of these isotopes varies across space, time and reservoirs. The IAEA's standard Vienna Standard Mean Ocean Water (VSMOW) serves as a baseline, closely resembling the isotopic composition of modern seawater. Relative abundance of 18 O with regard to 16 O is expressed relative to the VSMOW standard as δ 18 O and given in units of permil.

Measuring δ 18 O in water, vapor, snow and ice allows for quantifying hydroclimatic processes in the global water cycle and has been used to this end for many decades [START_REF] Dansgaard | Stable isotopes in precipitation[END_REF][START_REF] Konecky | The Iso2k database: a global compilation of paleoδ18O and δ2H records to aid understanding of Common Era climate[END_REF]. In addition to its use in present-day hydrology, δ 18 O in environmental archives also serves as a powerful proxy for past hydrology and, in turn, climate. As such, δ 18 O is a crucial and quantitative tool for both reconstructions of past climate and for comparison of proxy data to climatemodel outputs.

Oxygen isotope records are available from different palaeoenvironmental archives e.g. in glaciers and ice sheets [START_REF] Andersen | North Greenland Ice Core Project, m.: High-resolution record of Northern Hemisphere climate extending into the last interglacial period[END_REF], permafrost (Meyer et al., 2015b), marine [START_REF] Spielhagen | Upper ocean variability off NE Greenland (79°N) since the last glacial maximum reconstructed from stable isotopes in planktic foraminifer morphotypes[END_REF] and lacustrine [START_REF] Leng | Isotopes in palaeoenvironmental research[END_REF] environments as well as different materials, such as carbonates [START_REF] Kwiecien | Dynamics of the last four glacial terminations recorded in Lake Van, Turkey[END_REF], silicates [START_REF] Leng | Isotopes in palaeoenvironmental research[END_REF], biomarkers [START_REF] Lasher | Holocene temperatures and isotopes of precipitation in Northwest Greenland recorded in lacustrine organic materials[END_REF], cellulose [START_REF] Wolfe | Progress in isotope paleohydrology using lake sediment cellulose[END_REF], glacier [START_REF] Andersen | North Greenland Ice Core Project, m.: High-resolution record of Northern Hemisphere climate extending into the last interglacial period[END_REF] and ground ice [START_REF] Opel | Ground-ice stable isotopes and cryostratigraphy reflect late Quaternary palaeoclimate in the Northeast Siberian Arctic (Oyogos Yar coast, Dmitry Laptev Strait)[END_REF]. Therefore, oxygen isotopes offer the possibility for directly comparing data from different palaeoenvironmental archives.

The predictability of isotope fractionation processes in the water cycle due to clear physical constraints allows for using δ 18 O not only as a quantitative tool for past (hydro)climate reconstructions, but also for implementing δ 18 O in global climate models (e.g. [START_REF] Danek | Eurasian Holocene climate trends in transient coupled climate simulations and stable oxygen isotope records[END_REF]. However, challenges persist in understanding and comparing data and model outputs, partly due to complex signal formation in environmental archives [START_REF] Danek | Eurasian Holocene climate trends in transient coupled climate simulations and stable oxygen isotope records[END_REF]. Lake sediments are prominent and widespread archives in terrestrial environments [START_REF] Leng | Isotopes in palaeoenvironmental research[END_REF][START_REF] Biskaborn | Late Quaternary vegetation and lake system dynamics in north-eastern Siberia: Implications for seasonal climate variability[END_REF][START_REF] Subetto | Paleolimnological studies in Russian northern Eurasia: A review[END_REF]. Like glaciers and ice caps, lakes may record the isotopic signature of past precipitation (Shemesh et al., 2001a).

The signal formation in lakes, however, is fundamentally different from that in glaciers and ice caps with the lake water body acting as a buffer of the enclosed (hydro)climate signal, influenced by factors such as, catchment hydrology, lake ontogeny, and sediment accumulation rates [START_REF] Bittner | The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms[END_REF]. While biogenic silica is also found in phytoliths, sponge spicules and chrysophytes, this work focuses exclusively on diatoms. Diatoms are microscopic algae synthesizing their frustules from lake water and the silica dissolved therein, thereby preserving the isotope signal of past lake water. The oxygen isotope composition of the biogenic silica of diatom frustules (δ 18 OBSi) buried in lake sediment therefore provides valuable insight on past lake water and, in turn, precipitation.

Naturally, the interplay of hydrological and sedimentological processes limits the time span and resolution over which environmental information can be obtained from a lake system, and this varies from lake to lake. Most commonly, δ 18 OBSi has https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. been applied to lake sediments devoid of carbonates. These lakes are especially common in high altitude and high latitude regions [START_REF] Leng | A review of the oxygen isotope composition of lacustrine diatom silica for palaeoclimate reconstruction[END_REF]. 95

Controls on δ 18 OBSi

As a result of the complex signal formation in δ 18 OBSi records, most authors refer to a combination of factors for interpreting a given individual record. A schematic overview of some of the main processes is provided in Fig. 1. Lake water temperature (Tlake) imparts a direct effect on δ 18 OBSi due to temperature-dependent fractionation during biosynthesis of biogenic silica. The temperature-dependent fractionation coefficients were initially determined for marine environments [START_REF] Leclerc | Temperature dependence of the oxygen isotopic fractionation between diatom silica and water[END_REF][START_REF] Matheney | Oxygen-isotope fractionation between marine biogenic silica and seawater[END_REF] and later adapted for lacustrine sediments, as well. The effect of Tlake amounts to ca. -0.2‰/°C during biosynthesis [START_REF] Dodd | A laser fluorination method for oxygen isotope analysis of biogenic silica and a new oxygen isotope calibration of modern diatoms in freshwater environments[END_REF][START_REF] Moschen | Sensitivity of biogenic silica oxygen isotopes to changes in surface water temperature and palaeoclimatology[END_REF]. However, the applicability of these calibrations to sedimentary records is debated due to possible disequilibrium between diatom frustules and lake water, as well as taphonomic and diagenetic processes [START_REF] Leng | A review of the oxygen isotope composition of lacustrine diatom silica for palaeoclimate reconstruction[END_REF][START_REF] Ryves | Understanding the transfer of contemporary temperature signals into lake sediments via paired oxygen isotope ratios in carbonates and diatom silica: Problems and potential[END_REF][START_REF] Smith | An experiment to assess the effects of diatom dissolution on oxygen isotope ratios[END_REF][START_REF] Tyler | Post-mortem oxygen isotope exchange within cultured diatom silica[END_REF].

More commonly, changes in δ 18 OBSi are attributed to δ 18 O of lake water (δ 18 Olake) and, with the lake as a buffer, to the isotopic composition of precipitation (δ 18 Oprecipitation). Locally, δ 18 Oprecipitation is primarily influenced by air temperature (Tair) with a fractionation of 0.7‰/°C on global average [START_REF] Dansgaard | Stable isotopes in precipitation[END_REF]. On a broader scale, parameters such the moisture source region and atmospheric circulation patterns are important. Air masses transported to a lake are linked to their trajectories and source regions. Hence, changes in δ 18 OBSi records may be indicative of changes in atmospheric circulation patterns, also influencing the local ratio of precipitation to evaporation (P/E). The parameter P/E refers to the balance between the amount of precipitation and evaporation within a lake and its catchment. Typically, water loss through evaporation leads to higher δ 18 Olake values due to evaporative enrichment, and therefore higher δ 18 OBSi. Yet, precipitation amount and seasonality (e.g., rain vs. snow) will also strongly impact the isotope signal of the lake water. Disentangling the effects of precipitation and evaporation in δ 18 OBSi records is thus a major challenge and therefore some authors commonly refer to P/E-changes in conjunction with other factors [START_REF] Hernandez | Climate, catchment runoff and limnological drivers of carbon and oxygen isotope composition of diatom frustules from the central Andean Altiplano during the Lateglacial and Early Holocene[END_REF][START_REF] Rosqvist | Shifts in precipitation during the last millennium in northern Scandinavia from lacustrine isotope records[END_REF]Broadman et al., 2020a). Shemesh et al. (2001a) have attributed the δ 18 OBSi signal changes of Lake 850 in Swedish Lapland to different contributions of main source regions of precipitation, namely the Atlantic and Arctic Oceans. Indeed, for this location, changes in atmospheric circulation patterns imply changes in both, Tair and humidity.

Additionally, δ 18 Oprecipitation may also be linked to shifts in the seasonality of precipitation [START_REF] Swann | A combined oxygen and silicon diatom isotope record of Late Quaternary change in Lake El'gygytgyn, North East Siberia[END_REF][START_REF] Kostrova | Oxygen isotope composition of diatoms from sediments of Lake Kotokel (Buryatia)[END_REF][START_REF] Harding | Hydrological (in)stability in Southern Siberia during the Younger Dryas and early Holocene[END_REF], which is linked to Tair change, but also atmospheric circulation patterns (Shemesh et al., 2001a;[START_REF] Jones | Holocene climate of the Kola Peninsula; evidence from the oxygen isotope record of diatom silica[END_REF][START_REF] Leng | Investigating late holocene climate variability in central mexico using carbon isotope ratios in organic materials and oxygen isotope ratios from diatom silica within lacustrine sediments[END_REF][START_REF] Rosqvist | Shifts in precipitation during the last millennium in northern Scandinavia from lacustrine isotope records[END_REF] and, on longer timescales, insolation [START_REF] Swann | A combined oxygen and silicon diatom isotope record of Late Quaternary change in Lake El'gygytgyn, North East Siberia[END_REF][START_REF] Kostrova | Holocene hydrological variability of Lake Ladoga, northwest Russia, as inferred from diatom oxygen isotopes[END_REF][START_REF] Kostrova | Climate and environmental changes of the Lateglacial transition and Holocene in northeastern Siberia: Evidence from diatom oxygen isotopes and assemblage composition at Lake Emanda[END_REF]. Tair as often inferred from δ 18 OBSi can, therefore, be a parameter with local, regional and global significance.

Insolation is not strictly speaking an environmental parameter which can be inferred from δ 18 OBSi records. It is, however, commonly used as an explanatory variable and underlying driver of Holocene climate change. Insolation can be calculated for any given place throughout time [START_REF] Laskar | A long-term numerical solution for the insolation quantities of the Earth[END_REF], which allows for direct comparison with δ 18 OBSi time series. Insolation primarily influences Tair and, indirectly, the P/E balance and atmospheric circulation patterns. Moreover, hydrological processes within a lake's catchment may substantially impact δ 18 Olake and hence, δ 18 OBSi. Some of these processes are closely linked to climate and precipitation patterns described above. Most notable are variations in the amount of snow melt [START_REF] Mackay | Hydrological instability during the Last Interglacial in central Asia: a new diatom oxygen isotope record from Lake Baikal[END_REF][START_REF] Rosqvist | Shifts in precipitation during the last millennium in northern Scandinavia from lacustrine isotope records[END_REF][START_REF] Meyer | Lacustrine diatom oxygen isotopes as palaeo precipitation proxy -Holocene environmental and snowmelt variations recorded at Lake Bolshoye Shchuchye, Polar Urals, Russia[END_REF] and glacial influx (Meyer et al., 2015a) reaching the lake. Glaciers or snow fields in the hinterland, may provide more melt (with lower/depleted δ 18 O) in warm phases -countering the influence of warming on δ 18 Oprecipitation (Meyer et al., 2015a).

Other hydrological processes, however, are only indirectly linked to climate. These include the formation and closure of outflows to the lake which change the lake's hydrological setting [START_REF] Hernandez | The palaeohydrological evolution of Lago Chungara (Andean Altiplano, northern Chile) during the Lateglacial and early Holocene using oxygen isotopes in diatom silica[END_REF][START_REF] Vyse | Geochemical and sedimentological responses of arctic glacial Lake Ilirney, chukotka (far east Russia) to palaeoenvironmental change since ∼51.8 ka BP[END_REF][START_REF] Bittner | The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms[END_REF]. Associated changes in mass-balance of a lake and, thus, P/E-balance may lead to a different δ 18 OBSi signal.

In order to interpret a given δ 18 OBSi, information about the present hydrology is important as it provides insight on which processes influence δ 18 OLake and, in turn, δ 18 OBSi. Naturally, as the hydrology of a given lake can only offer snapshots of present-day constraints, caution has to be applied when extrapolating these into the past. The isotopic composition of three components is of interest for assessing the signal properties of δ 18 OBSi records: (1) δ 18 O lake water, (2) δ 18 O of inflows to the lake and (3) δ 18 O of precipitation. Lake water composition can provide insight on whether lake water is isotopically homogenous, both spatially and at different depths of the lake basin.

Offsets of δ 18 OLake from the Local Meteoric Water Line (LMWL) give hints on whether or not lake evaporation may have had a significant effect on lake water isotopic composition. δ 18 OLake can also be used in conjunction with Tlake and the most recent δ 18 OBSi value for testing the temperature-dependent fractionation and, in turn, the applicability of the proxy for paleoclimate reconstructions. Complementing the lake water isotopic composition with the isotopic composition of inflow (rivers) provides further information on specific hydrological constraints. For larger lakes and catchments, the different inflows and their effect on the lake's isotopic mass balance have been used for inferring changing hydrology or precipitation regimes in different parts of the catchment (e.g. [START_REF] Mackay | A reassessment of late glacial -Holocene diatom oxygen isotope record from Lake Baikal using a geochemical mass-balance approach[END_REF].

While the isotopic composition of precipitation provides useful information, it is often not available for field studies and few monitoring studies of precipitation and lake water isotope compositions in combination with δ 18 OBSi do exist [START_REF] Kostrova | Holocene hydrological variability of Lake Ladoga, northwest Russia, as inferred from diatom oxygen isotopes[END_REF][START_REF] Hernandez | ENSO and solar activity signals from oxygen isotopes in diatom silica during late glacial-Holocene transition in Central Andes (18A degrees S)[END_REF]. A possible workaround can be derived from the GNIP database (IAEA/WMO, 2022) and spatial interpolations thereof, e.g. The Online Isotopes in Precipitation Calculator (Bowen, 2017).

Sample preparation and measurement

Extracting pure diatom valves (frustules) from lake sediments is a complex process and depends on a sufficiently high diatom concentration in the sediment. Various cleaning procedures for diatom extraction exist, which are mainly based on the use of H2O2 for removing organic matter from the sediment and HCl for the removal of carbonate (Chapligin et al., 2012a). Detrital components are often separated by being centrifuged in heavy liquid solution, i.e. Sodium Polytungstate [START_REF] Morley | Cleaning of lake sediment samples for diatom oxygen isotope analysis[END_REF]Chapligin et al., 2012a). Different procedures in sample preparation, i.e. different temperatures, may result in offsets of measured δ 18 OBSi [START_REF] Swann | A combined oxygen and silicon diatom isotope record of Late Quaternary change in Lake El'gygytgyn, North East Siberia[END_REF]Chapligin et al., 2012b;[START_REF] Tyler | Post-mortem oxygen isotope exchange within cultured diatom silica[END_REF]. Impurities due to incomplete removal of https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. detrital components may also affect the measured δ 18 OBSi [START_REF] Lamb | A comparison of the palaeoclimate signals from diatom oxygen isotope ratios and carbonate oxygen isotope ratios from a low latitude crater lake[END_REF]Chapligin et al., 2012b). To account for this, the purity of samples is usually assessed prior to measurement by visual inspection or direct measurement of the amount of contaminants of a given sample [START_REF] Bailey | Holocene atmospheric circulation in the central North Pacific: A new terrestrial diatom and δ18O dataset from the Aleutian Islands[END_REF]Broadman et al., 2020a). Fewer studies determine the isotopic composition of detrital contaminants to apply a correction to the measured δ 18 OBSi values [START_REF] Brewer | Unravelling contamination signals in biogenic silica oxygen isotope composition: the role of major and trace element geochemistry[END_REF][START_REF] Mackay | A reassessment of late glacial -Holocene diatom oxygen isotope record from Lake Baikal using a geochemical mass-balance approach[END_REF]Wilson et al., 2014a;[START_REF] Bittner | The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms[END_REF][START_REF] Kostrova | Climate and environmental changes of the Lateglacial transition and Holocene in northeastern Siberia: Evidence from diatom oxygen isotopes and assemblage composition at Lake Emanda[END_REF]. Consequently, caution has to be applied when comparing absolute values of different individual δ 18 OBSi records, as offsets between individual records may result from both different preparation and measurement techniques and different isotopic signals of the corresponding lake water. The potential and challenges associated with data stemming from different preparation and measurement techniques have already been addressed [START_REF] Chapligin | Inter-laboratory comparison of oxygen isotope compositions from biogenic silica[END_REF][START_REF] Mackay | A reassessment of late glacial -Holocene diatom oxygen isotope record from Lake Baikal using a geochemical mass-balance approach[END_REF].

Aim of this work

A comprehensive compilation and assessment of the lake sediment δ 18 OBSi records published to date is missing. Due to the crucial role of lake and catchment hydrology in signal formation, such a compilation needs to include individual lake basin parameters, such as lake volume and lake water residence time (tres), in order to provide reliable constraints for interpreting and comparing the individual records. Proxy data compilations have already addressed a lack of standardized metadata, data availability and data uniformity of paleo-data [START_REF] Pfalz | Harmonizing heterogeneous multi-proxy data from lake systems[END_REF]. Such compilations, however, generally do not include δ 18 OBSi-records and do not provide all relevant lake basin parameters [START_REF] Kaufman | Holocene global mean surface temperature, a multi-method reconstruction approach[END_REF] or have a more limited temporal focus [START_REF] Konecky | The Iso2k database: a global compilation of paleoδ18O and δ2H records to aid understanding of Common Era climate[END_REF]. Consequently, no study has yet empirically linked the signal properties of δ 18 OBSi records and lake basin parameters in a harmonized dataset.

In order to overcome these gaps, this paper aims at providing a comprehensive compilation and combined statistical evaluation of the lake sediment δ 18 OBSi-records published to date. We accomplish these objectives by means of the following working steps: 1) collecting available lake sediment δ 18 OBSi-records published to date, 2) complementing these records with the individual lake basin parameters and 3) assessing the signal properties of δ 18 OBSi records with regard to lake basin parameters, in order to 4) identify common spatio-temporal patterns and trends in the δ 18 OBSi signals. This effort shall lead to a better understanding of the general constraints for interpreting lake sediment δ 18 OBSi-records and make these records more readily usable also for proxy-model comparisons. It is, hence, a contribution to bridge the gap between modelling and isotope geochemistry approaches in paleoclimate science.

https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License.

Methods

This study follows a three-stage approach: the first stage (data acquisition) comprises identifying lacustrine δ 18 OBSi datasets and publications published to date. A second stage includes acquiring the actual δ 18 OBSi datasets and archiving them in a standardized format. Where appropriate, the identified published datasets were arranged into longer continuous records. This includes records from the same sediment core published in different manuscripts and records from different sediment cores from the same lake but similar locations. The third and final stage (record analysis) interprets the actual lacustrine δ 18 OBSi isotope records with respect to their hydrological and geographical constraints in order to identify possible common trends and signal properties of all isotope records or smaller spatially or temporally constrained datasets.

Identification and acquisition of the datasets and publications in this work followed an additive approach, i.e. thorough literature survey. We have chosen this approach due to the limited number of laboratories and working groups worldwide measuring δ 18 OBSi. In this study, we focused exclusively on down-core records from lacustrine sediments. Identified publications and datasets were entered into a uniform metadata table giving one entry to each publication and each dataset. If more than one publication was written about the same sediment core, each of these publications was given a separate entry.

Likewise, if one publication presents data from more than one sediment core, each of the sediment cores was given a separate entry to the database.

For each of these entries, metadata on coring procedure, hydrological setting and chronology were supplemented. Data were extracted from the corresponding publication(s), from public repositories or directly from the authors. Hydrological parameters such as catchment area, average depth and tres were additionally obtained from the HydroLAKES database [START_REF] Messager | Estimating the volume and age of water stored in global lakes using a geo-statistical approach[END_REF] and stored as separate variables. For a detailed description on how the values in the HydroLAKES database were created, we refer to [START_REF] Messager | Estimating the volume and age of water stored in global lakes using a geo-statistical approach[END_REF]. This procedure was necessary because original publications do not always specify all of these parameters and because parameters supplied in original publications may not be consistent. For further analysis and for linking the individual isotope records with lake basin parameters, the HydroLAKES database entries were given preference.

Original publications were only used for lakes where no data were available from the HydroLAKES database. The parameter "maximum water depth" was always taken from the original publications since this parameter is not provided by the HydroLAKES database. While the geo-statistical approach of the HydroLAKES database may not provide the most precise values for individual lake basin characteristics, it ensures comparability among the different lake basins analyzed in this study.

It also prevents potential issues arising from different authors providing conflicting values for the same lake basin (i.e. Lake Baikal, Lake El'gygytgyn).

Isotope datasets for each of the entries were archived in separate tables specifying depth, age and measured isotope values.

Datasets were taken directly from the respective publication, whenever possible. If datasets were not available, within the original publications or as supplements thereof, public repositories (such as www.pangaea.de; ncei.noaa.gov) were searched.

In case datasets were unavailable from repositories, the lead authors were contacted directly. In case of published data unavailable from repositories or authors, plots of the original publications were digitized, if possible [START_REF] Rietti-Shati | A 3000-Year Climatic Record from Biogenic Silica Oxygen Isotopes in an Equatorial High-Altitude Lake[END_REF] https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. Hu and Shemesh, 2003). Where digitizing plots was not feasible, records were excluded from further consideration; this was the case for [START_REF] Chondrogianni | Millennial to interannual climate variability in the Mediterranean during the Last Glacial Maximum[END_REF] and Hu et al. (2003).

Chronologies were adapted from the original publications, where available and stored in cal yrs BP format (relative to 1950 CE). Sample ages given in different formats (e.g. b2K or CE) were converted to cal yrs BP. This procedure also applies to radiocarbon-based chronologies. Chronologies were not recalculated because the effect of different 14 C-calibrations and different age model approaches is supposedly minor with regard to the aim of this study. This is especially true when considering the fact that high-resolution datasets (annual to decadal resolution) are the exception among all datasets identified.

The error introduced by the different age models is, thus, considered minor when compared to the resolution of the datasets.

For applications requiring more precise chronologies and better comparability of datasets, we provide the radiocarbon measurements of respective datasets as well. This enables future users to create tailor-made chronologies if needed. Datasets without chronologies were stored using depth notation only.

For further analysis, datasets were partly regrouped and combined to generate longer continuous δ 18 OBSi datasets, henceforth referred to as «records». This comprised treating datasets with data from several coring sites or outcrops from the same lake as one single record, in agreement with the author's original interpretation [START_REF] Quesada | Impact of Bolivian paleolake evaporation on the δ18O of the Andean glaciers during the last deglaciation (18.5-11.7 ka): diatom-inferred δ18O values and hydro-isotopic modeling[END_REF][START_REF] Swann | Lake Baikal isotope records of Holocene Central Asian precipitation[END_REF]. Data stemming from the same sediment core but published in different manuscripts were combined into single continuous records. This applies to records from Lake Kotokel (Kostrova et al., 2013a;Kostrova et al., 2013b;[START_REF] Kostrova | The last glacial maximum and late glacial environmental and climate dynamics in the Baikal region inferred from an oxygen isotope record of lacustrine diatom silica[END_REF][START_REF] Kostrova | Oxygen isotope composition of diatoms from sediments of Lake Kotokel (Buryatia)[END_REF] and Lago Chungará [START_REF] Hernandez | The palaeohydrological evolution of Lago Chungara (Andean Altiplano, northern Chile) during the Lateglacial and early Holocene using oxygen isotopes in diatom silica[END_REF][START_REF] Hernandez | ENSO and solar activity signals from oxygen isotopes in diatom silica during late glacial-Holocene transition in Central Andes (18A degrees S)[END_REF][START_REF] Hernandez | Biogeochemical processes controlling oxygen and carbon isotopes of diatom silica in Late Glacial to Holocene lacustrine rhythmites[END_REF][START_REF] Hernandez | Climate, catchment runoff and limnological drivers of carbon and oxygen isotope composition of diatom frustules from the central Andean Altiplano during the Lateglacial and Early Holocene[END_REF].

Likewise, data from different cores presented in different publications but stemming from identical or reasonably similar coring sites were combined to single records. This applies to data from Lake Nar [START_REF] Dean | Seasonality of Holocene hydroclimate in the Eastern Mediterranean reconstructed using the oxygen isotope composition of carbonates and diatoms from Lake Nar, central Turkey[END_REF] and Vuolep Allakasjaure [START_REF] Rosqvist | Diatom oxygen isotopes in pro-glacial lake sediments from northern Sweden: a 5000 year record of atmospheric circulation[END_REF][START_REF] Jonsson | High-resolution diatom δ18O records, from the last 150 years, reflecting changes in amount of winter precipitation in two sub-Arctic high-altitude lakes in the Swedish Scandes[END_REF]. Lakes consisting of several basins were generally treated as one; this includes Lake Baikal and several smaller lakes.

For trend analysis and comparison of records with regard to Holocene and Common Era climate, we focused on records from northern hemisphere (NH) extratropic lakes (45-90° N) because these time periods and geographical focus are the only options with a significant number of records which makes an interpretation departing from case studies feasible.

In a first step, records were binned to 1 kyr intervals (for the Holocene) and 200 year intervals (for the CE), respectively. These intervals were chosen based on the temporal resolutions of the original records in order to ensure continuous binned records with no empty bins. Choosing higher resolutions would have resulted in many records having empty bins with no datapoints, thus leading to different temporal resolutions even after binning. The binning was done by calculating the mean value of all samples within the respective age interval for each individual record. For the analysis of the Holocene period, datapoints with ages <150 yrs BP were excluded to eliminate any possible effects of recent warming. Analysis of Common Era climate on the other hand makes use of these datapoints. For an assessment of the timing of Holocene maxima and minima, records covering less than 10 bins were discarded. For trend analysis of Holocene and Common Era climate, records covering less than seven bins were discarded. In order to eliminate offsets between individual binned records, a mean removal was performed by subtracting the mean of a given binned record from the respective record. After mean removal, two subsequent filtering steps were performed in order to exclude records most prone to secondary lake evaporation. First, a subset consisting only of records from open lakes was created, discarding records from semi-closed lakes, closed lakes and paleo-lakes. In a second step, this open-lakes-subset was filtered by discarding all records with tres>100 years. This threshold was chosen in accordance with previous works classifying lakes and their isotopic signals with respect to hydrologic setting and tres [START_REF] Leng | Palaeoclimate interpretation of stable isotope data from lake sediment archives[END_REF].

After applying these filters, combined trends for geographical regions (NH, Eurasia, North America) were created by calculating the mean of all records for each bin.

Results

Published datasets

Following a thorough literature survey, a total number of 71 published down-core datasets of δ 18 OBSi from 64 sites has been identified. Ever since the first records of δ 18 OBSi from lake sediments have been published [START_REF] Rietti-Shati | A 3000-Year Climatic Record from Biogenic Silica Oxygen Isotopes in an Equatorial High-Altitude Lake[END_REF][START_REF] Shemesh | Oxygen isotopes in fresh water biogenic opal -Northeastern US Alleröd-Younger Dryas temperature shift[END_REF], there has been a growing research interest, manifest in an increasing number of publications (Fig. A1). Only recently has there been a stagnation of the number of records published. A detailed overview of the identified publications and the records presented therein is provided in Tab. A2.

Most publications give the δ 18 OBSi data as time series, as is usual in paleoenvironmental studies. The chronologies rely on a wide variety of dating methods (Fig. A2), with 14 C (used on 46 records) being by far the most frequent. For subrecent time periods and shorter time scales, 210 Pb and 137 Cs are also used extensively (on 21 and 12 records, respectively). Globally or regionally correlated time markers such as tephra layers [START_REF] Heyng | Middle and Late Holocene paleotemperatures reconstructed from oxygen isotopes and GDGTs of sediments from Lake Pupuke, New Zealand[END_REF] or high-resolution methods such as varve counts [START_REF] Rozanski | Oxygen-isotope geothermometers in lacustrine sediments: New insights through combined δ18O analyses of aquatic cellulose, authigenic calcite and biogenic silica in Lake Gościąż, central Poland[END_REF] are used relatively sparsely as they are not available for all time periods and/or lake basins.

Combined records

We combined separate records stemming from the same lake sites to longer, continuous composite records and yielded a total of 54 combined δ 18 OBSi records, seven of which stem from paleolakes (three with and four without chronology) while 49 records stem from present, still existing lakes (44 with and five without chronology). An overview of these combined records is provided in Tab. A1, complemented by metadata of the records and the corresponding lake basins. Each individual record received a number (#X) which is used consistently throughout the text.

The temporal coverage of these combined records (Fig. 2) varies from centennial-scale at Laguna Zacapu [START_REF] Leng | Investigating late holocene climate variability in central mexico using carbon isotope ratios in organic materials and oxygen isotope ratios from diatom silica within lacustrine sediments[END_REF] and a specific study at Lake Baikal [START_REF] Swann | Lake Baikal isotope records of Holocene Central Asian precipitation[END_REF] (records #50, #51) to glacial-interglacial cycles e.g. 250 kyrs at Lake El'gygytgyn (#3, (Chapligin et al., 2012b)). Most records (N=32) cover the last several thousand up to about 10 kyr BP while only a few records cover several tens of thousands of years (e.g. #8 to #10). Likewise, the time periods covered do vary either https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. due to the availability of lake sediments, diatom abundances in a lake and/or scientific foci of the research groups. By far the highest number of records is available for MIS 1 (N=37) and especially for the last 2 kyrs (N=48). MIS 2 is still covered by 19 records, whereas towards MIS 3 (N=5) and beyond fewer records have been generated. However, single records cover even time periods in MIS 11 (at Lake Baikal; #2) and beyond (MIS G1/104, #1), outlining the applicability of this proxy across a wide range of time scales. A paleo lake from the Baringo-Bogoria Basin (record #1), is the oldest lacustrine δ 18 OBSi record and has been dated to the onset of MIS 104 in the late Pliocene (Wilson et al., 2014b).

Regarding the number of published records by continent (Fig. 3), there is a clear focus on Asia and Europe with 21 and 15 records published, respectively. In Asia, there is a strong regional focus on Siberia, whereas most other parts of the continent

are not yet investigated for lake sediment δ 18 OBSi. A regional focus also occurs in Africa and South America. While a sizeable number of records stemming from these continents have been published (N=10 and N=11, respectively), there are pronounced regional foci in the East African Rift and the Andes, respectively. Another focus region is Alaska, where most (N=6) of the published North American records (N=7) are located. δ 18 OBSi work has also been carried out in Oceania with published records from lakes in New Zealand (#42) and South Georgia (#19).

In summary, the distribution of available δ 18 OBSi data displays, thus, a bias towards the mid-to high latitudes of the northern hemisphere. Additionally, this distribution is also indicative of the site accessibility and (regional) research foci of the working groups. This has a rather pronounced effect on the spatial distribution of available δ 18 OBSi records. The geographical distribution is also indicative of cold regions devoid of carbonates where biogenic silica is the most promising archive to obtain oxygen isotope records from lake sediments. This pattern also affects the latitudinal distribution of the records (see also Tab. A1) with records ranging from 54.17 °S (# 19) to 69° N (# 39). Records stemming from low-latitude lakes (particularly in Africa and South America) are often located at high altitudes above 3000 m asl (above sea level; e.g., #11, 17, 18, 21). Lake Simba Tarn (record #34) features the maximum altitude for an individual δ 18 OBSi record of 4959 m asl. Altitudes below 1000 m asl, however, are most common (N=36), especially for high-latitude lakes. In total, 12 lakes are located below 100 meters asl (e.g., #29, 35). Many of these low-altitude lakes are located in maritime locations in immediate proximity to the coast (e.g., #19, 30) or have even had marine intrusion stages in the past (a postglacial transgression at Nettilling Lake; #41). Extremely continental environments are tackled in central and eastern Siberia and the Lake Baikal region (e.g., #4, 8, 9, 10, 25).

Spatial coverage and resolution of combined records

Varying spatial resolution among the compiled isotope records is linked to the fact that lakes and their corresponding 330 catchments are not points in space but areas. Consequently, lake water and, thus, the related δ 18 OBSi-signal represent a spatial average, integrating over the catchment size of the respective lake. Lake basin sizes range from small ponds of <1 km² (e.g. #19, 11, 23, 33, 34) to some of the largest lakes in the world, including lake Malawi and Lake Baikal covering 29,544 km² and 31,968 km², respectively (Fig. 4A). Large and voluminous lakes are the exception, however, and most of the lakes represented here are <10 km² in size (N=25). Note that in case of paleo lakes, such parameters are not applicable. While authors sometimes 335 provide estimates on paleo lake extent, these figures are not consistent with the values determined for present lakes and are https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. therefore not included in the evaluation of the dataset. Catchment sizes vary by several orders of magnitude as well. For small lakes, catchments are often <10 km² (N=13, e.g. #22, 33, 37), whereas the largest lakes, Lake Malawi and Lake Baikal feature catchments of 128,727 km² and 569,176 km², respectively (Fig. 4A). Therefore, these lakes integrate the environmental signal over a large and potentially diverse region in terms of hydrology. While most of the lakes compiled in this study are primarily fed by surface runoff and/or precipitation (according to the original publications of records), groundwater influx may also play a pivotal role. Groundwater influx may introduce a large memory effect of past precipitation due to the generally long residence times of aquifers. This may have an impact on records especially when looking at short timescales. Groundwater input, however, is usually not accounted for and, thus, beyond the scope of our study. In summary, both lake sizes and catchment sizes vary by several orders of magnitude (Fig. 4A) among the sites with existing δ 18 OBSi records, and span from local signals

Temporal coverage and resolution of combined records

Temporal resolution of the records and the resulting signal properties are determined by both the lake basin itself (i.e. accumulation rates and preservation of diatom silica) and the sampling routine applied to the sediment core (i.e. the https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. sampled intervals as well as the thickness of individual samples). Data on the thickness of single sediment samples taken from the cores are, however, scarce in the original publications. The same applies for information on the time interval or number of years represented by a single sediment sample. Consequently this parameter and its potential effect on the records' signal properties could not be investigated in detail in this manuscript. We therefore focus on tres and sampling frequency of a core as a means of characterizing the records and their temporal resolution.

The tres is closely linked to the size of lake basins and varies accordingly. It ranges from several weeks for small lakes (e.g., #49, 50) to centuries (219 and 375 years for Lake Malawi and Lake Baikal, respectively). On the whole, tres of sub-annual to annual scale are most common (N=17) among the lakes considered in this study (Fig. 4B). It should be noted that longer tres leads to averaging of the signal over a longer time period. Likewise, different tres may also have an effect on absolute δ 18 OBSi values and variabilities. Lakes with very long tres (tres>100 years) are tendentially more susceptible to lake evaporation, and may effectively behave like closed-system lakes with regard to the δ 18 OBSi signal even if they are hydrologically open (i.e. have outflows). These are still referred to as hydrologically open in this work and hydrological settings and tres are addressed separately in the discussion.

Also the sampling frequency varies by several orders of magnitude (Fig. 4B). It stretches from annual to multi-millenial timescales. Consequently, the signal properties and the recorded climatic and/or hydrological forcings of the identified records can be expected to vary accordingly. Most records, however, plot in the top left half of graph of Fig. 4B, which indicates that the temporal offset between two sediment samples exceeds tres. This suggests that the sampling routine is the limiting factor of the temporal resolution of these records. Only three records from Lake Baikal plot in the lower right half of Fig. 4B, suggesting in these cases (#4, #20, #51) tres to be the dominant factor in determining the record's resolution, at least with respect to inflowrelated changes.

We thus conclude that the sampling resolution is the main factor determining the temporal resolution of most records with tres acting as an additional smoothing mechanism. A lake with a centennial-scale tres can, therefore, display centennial-scale changes of climate and hydrology to their full amplitude. Decadal-scale changes, on the other hand, can be expected to be attenuated by an order of magnitude in a lake with centennial-scale tres. Based on tres and sampling resolutions of the records, comparing records on a centennial or millennial scale is the most promising approach for assessing common patterns.

Discussion

Common Era Climate

The Common Era subset of records including only records stemming from sites north of 45° N (Fig. 5A,N=19), comprises 460 datapoints. The records display considerable offsets with δ 18 OBSi values ranging from +19‰ (#34) to +33‰ VSMOW (#35). These offsets can be linked to their individual environmental setting, e.g. latitudinal and continentality effects, as well as to their potential to be prone for lake evaporation. Amplitudes in δ 18 OBSi of these records vary from 0.4‰ (#24) to circa 9‰ https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License.

VSMOW (#35

). This variability might correspond to their different hydrological settings. Closed lakes (such as Sunken Island Lake; #26) have a tendency towards higher δ 18 OBSi amplitude likely due to lake evaporation leading to a more enriched isotope signature in the lake (Broadman et al., 2020b).

Binned records (Fig. 5B,N=14) do not display any common pattern and feature δ 18 OBSi-values ranging from +20‰ to +31‰ VSMOW. However, binning of datapoints and exclusion of shorter records reduces the δ 18 OBSi amplitudes of individual records, to less than 5‰. Offsets between individual records may be linked to site-specific characteristics of individual lakes and catchments, as well as latitudinal and continentality effects.

After mean removal (Fig. 5C) the CE data suggest a common trend with high δ 18 OBSi values at 1900 yrs BP and a general decrease until the present with the lowest values occurring in the last two bins (or 400 years). Some records also show maxima between 500 and 1100 yrs BP and minima at ca. 1300 yrs BP. The subsets for hydrologically open lakes (N=13, Fig. 5D) and hydrologically open lakes with tres<100yrs (N=9, Fig. 5E) show a similar picture.

The combined Common Era records (Fig. 5F) comprise 8 records and show a general δ 18 OBSi decrease over the last 2 kyr amounting to ca. 2‰ VSMOW. The δ 18 OBSi amplitude within individual bins, however, might exceed this number, most notably at 100, 1300 and 1900 yrs BP, which show the highest amplitudes of up to 5‰ for the Common Era. This is in line with differences between the timing of δ 18 OBSi maxima and minima between North American and Eurasian records. At centennial scale, these differences might also be linked to dating uncertainties. Moreover, the record of Lake Bolshoye Shchuchye (#16) features a much larger amplitude. Its exceptional δ 18 OBSi variability has been attributed by the authors to variations of snow and snow melt in the lake's catchment and therefore does represent a different kind of precipitation-based signal compared to most other records. The combined trend features its highest δ 18 OBSi values at 1900 yrs BP, followed by a decrease leading to a relative minimum at 1100 and 1300 yrs BP. This phase is followed by a second δ 18 OBSi peak at 700 and 900 yrs BP, after which a decrease can be observed. The decrease at 300 and 500 yrs BP features the least deviation between individual records. The most recent bin shows again a much larger δ 18 OBSi variability. While most records display the lowest values at this time, Lake Kotokel (#8) for instance shows an increase compared to the previous bins. This increase may or may not be related to recent warming; and due to the complex hydrology of the lake even lake evaporation cannot be ruled out. The majority of the records however does not indicate a recent δ 18 OBSi maximum, indicative for any impact of recent warming. It has to be noted that there is bias of data points towards the older end of the most recent bin. An absence of recent warming in the data therefore might be linked to this bias and does not rule out a reaction of lake systems to recent warming. As Eurasian records constitute the majority of records (N=7), the Eurasian trend is similar to the NH picture (Fig. 5H).

North American records (N=2) do not show a consistently decreasing trend (Fig. 5G), but slightly higher values at 1700 and 1900 yrs BP compared to the most recent bins (100 and 300 yrs BP, respectively). They do, however, show lower δ 18 OBSi values between 900 and 1300 yrs BP, followed by a δ 18 OBSi maximum at 500 yrs BP. As there are only two records available after filtering, caution has to be applied in interpreting this pattern.

Common patterns among Eurasian, and possibly NH, δ 18 OBSi records do suggest a common NH signal throughout the Common Era. The observed maxima and minima correspond to previously described climatic events, notably the Roman Warm Period from 2000 yrs BP to about 1600 yrs BP [START_REF] Ljungqvist | A new reconstruction of temperature variability in the extra-tropical northern hemisphere during the last two millennia[END_REF], the Dark Ages Cold Period from 1600 to 1200 yrs BP [START_REF] Büntgen | Cooling and societal change during the Late Antique Little Ice Age from 536 to around 660 AD[END_REF][START_REF] Helama | Dark Ages Cold Period: A literature review and directions for future research[END_REF] the Medieval Climatic Anomaly (MCA) from 1200 yrs BP to 800 yrs BP [START_REF] Bradley | Climate in Medieval Time[END_REF][START_REF] Mann | Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly[END_REF] and the Little Ice Age from 700 yrs BP to 100 yrs BP [START_REF] Matthews | The 'Little Ice Age': Re-Evaluation of an Evolving Concept[END_REF]. The good accordance of our data with these previously described warm and cold phases suggests that δ 18 OBSi records presented are influenced by Tair change, either directly or via other parameters which are linked to Tair. Recent research has rejected the global nature of these climatic events and suggested that they are regionally constrained [START_REF] Neukom | No evidence for globally coherent warm and cold periods over the preindustrial Common Era[END_REF]. However, the accordance of our data -when assessed at centennial scale -with these climatic events makes sense because they were initially described for North America and Europe.

Holocene (corresponding to MIS 1) Climate

The Holocene NH subset of records consists of 21 records which display considerable offsets of their mean δ 18 OBSi values ranging from +20‰ (#3) to +35‰ (#31) VSMOW (Fig. 6A). Lake El'gygytgyn (#3) is located in a continental, high-latitude environment with little secondary evaporation (Chapligin et al., 2012b) whereas Lake Ladoga (#31) is situated in a less continental, lower latitude setting with a complex hydrological history of changing inflows and outflows [START_REF] Kostrova | Holocene hydrological variability of Lake Ladoga, northwest Russia, as inferred from diatom oxygen isotopes[END_REF].

Amplitudes of the individual Holocene records vary from less than 5‰ (#3) to circa 10‰ VSMOW (#20, #35). Lake

El'gygytgyn (#3) is a voluminous, deep hydrologically open lake with little lake evaporation, whereas Heart Lake (#35) is a much smaller, less voluminous lake. Lake Baikal (#20) is a deep voluminous lake like Lake El'gygytgyn, however with a centennial-scale tres making it effectively closed and thus potentially subject to secondary evaporation. Consequently, differences in their isotopic variability might correspond to their different hydrological settings. Closed lakes (such as Sunken Island Lake; #26) have a tendency towards higher δ 18 OBSi amplitude likely due lake evaporation leading to a more enriched isotope signature of lake water (Broadman et al., 2020b). VSMOW, similar to the original records. However, binning of datapoints and exclusion of shorter records results in smoothed amplitudes of less than 5‰ VSMOW. Early Holocene binned records seem to have δ 18 OBSi values (up to 2.5‰) higher than the Holocene mean, whereas late Holocene values are generally up to 2‰ below the Holocene mean. However, some records do not follow this general pattern after mean removal (Fig. 6C). This could be indicative of the fact that the dataset still features lakes with different hydrological settings and tres which have a substantial impact on the recorded signal.

Filtering for hydrologically open lakes (Fig. 6D,N=13) and tres<100 yrs (Fig. 6E, N=10) displays a clear decreasing δ 18 OBSi trend of 2.5‰ throughout the Holocene. Differences between individual records do exist, though. Most notably, the absolute δ 18 OBSi maxima of individual records do not occur at the same time. While some records feature maxima at the beginning of the Holocene, other records feature maxima between 5 and 8 kyr BP. This pattern is in line with Holocene Tair reconstructions which have found spatial differences of the timing of the Holocene thermal maximum [START_REF] Kaufman | Holocene thermal maximum in the western Arctic (0-180°W)[END_REF][START_REF] Renssen | The spatial and temporal complexity of the Holocene thermal maximum[END_REF].

Based on this subset of hydrologically open lakes with tres<100 yrs, a combined millennial scale NH trend was calculated. This combined Holocene trend (Fig. 6F) shows a decrease throughout the Holocene amounting to ca. 2‰ VSMOW. The absolute maximum is observed for the Early Holocene bin at 11-12 kyr BP. A decrease at the beginning of the Holocene between 12 kyr BP and 10 kyr BP is followed by a relatively stable middle Holocene until 6 kyr BP and subsequent stronger decrease towards the absolute δ 18 OBSi minimum in the youngest bin (0-1 kyr BP).

When considered separately, North American (N=2) and Eurasian (N=8) records show different patterns and have been described and interpreted differently in the case studies published to date. While the former are primarily liked to atmospheric circulation changes in Alaska [START_REF] Bailey | Holocene atmospheric circulation in the central North Pacific: A new terrestrial diatom and δ18O dataset from the Aleutian Islands[END_REF]Broadman et al., 2020b;Broadman et al., 2020a), the latter are at least partly interpreted as indicative of Tair and insolation changes [START_REF] Swann | A combined oxygen and silicon diatom isotope record of Late Quaternary change in Lake El'gygytgyn, North East Siberia[END_REF][START_REF] Mackay | A reassessment of late glacial -Holocene diatom oxygen isotope record from Lake Baikal using a geochemical mass-balance approach[END_REF]Chapligin et al., 2012b;Kostrova et al., 2013a;[START_REF] Kostrova | Holocene hydrological variability of Lake Ladoga, northwest Russia, as inferred from diatom oxygen isotopes[END_REF][START_REF] Kostrova | Climate and environmental changes of the Lateglacial transition and Holocene in northeastern Siberia: Evidence from diatom oxygen isotopes and assemblage composition at Lake Emanda[END_REF]. Eurasian δ 18 OBSi records (N=8) display a slight decrease from 12 kyr BP to 10 kyr BP and suggest a second maximum at 7 kyr BP followed by a second relatively stable phase. An accelerated decrease starting at ca. 4 kyr BP constitutes a more abrupt change than in the NH trend. North American records do not show a consistently decreasing trend throughout Holocene (Fig. 6G), but rather slightly higher ∆ 18 OBSi values in the first half of the Holocene as compared to the second half. Since there are only two North American records fulfilling the aforementioned criteria, it is difficult to meaningfully go beyond the existing case studies, outlining the necessity for further research in this region.

The regional differences between North America and Eurasia are also manifested in the timing of absolute δ 18 OBSi minima and maxima of individual records (Fig. 7). The spatial pattern of the Holocene maxima of binned records shows a different timing of maxima for different regions (Fig. 7). Eastern Eurasian sites feature a pronounced early Holocene maximum (at 12 kyr BP), whereas sites more to the west of Eurasia show tendentially rather a middle Holocene maximum, around 6-8 kyr BP. This suggests that the double maxima of the Eurasian trend (Fig. 6H) is at least partly caused by the regional differences over The timing of Holocene minima is rather homogenous in northern Eurasia with all records reaching their minimum in the last 1 kyr BP or between 1 kyr BP and 2 kyr BP (Fig. 7). While the records generally follow the same decreasing long-term δ 18 OBSi trend, they feature either early or late Holocene minima. Since datapoints of 1850 CE and younger have been removed from the dataset prior to analysis to exclude the industrial era, a potential effect of recent climate change is not covered in this subset of data. As with the Holocene maximum, sites in Alaska also differ with regard to Holocene minimum. They tendentially show absolute minima earlier than Eurasian records (3 and 4 kyr BP, respectively). This underlines once more, the different behaviour of the regions (North America and Eurasia).

Combined Holocene trend in the hemispheric context

The combined trends of δ 18 OBSi for NH, Eurasia and North America are shown in comparison to other NH proxy records in Fig. 8. As individual δ 18 OBSi records are commonly discussed with respect to insolation, we provide June and December insolation curves for 60°N, calculated using [START_REF] Laskar | A long-term numerical solution for the insolation quantities of the Earth[END_REF]. As visible in Fig. 8, Eurasian and NH combined trends show a similarity with the June insolation as all records feature a decreasing trend throughout the Holocene. However, insolation decreases steadily after an early Holocene maximum whereas combined NH and Eurasian δ 18 OBSi trends feature a stable early Holocene and a second peak at 7 kyr BP. This presumably relates to the geographical distribution of the timing of δ 18 OBSi maxima and minima as discussed above. Therefore, eastern Eurasian records are most in line with June insolation which has been regarded as a proxy of summer Tair. Records stemming from sites further west are less directly correlated with June insolation. A striking difference is the accelerated decrease of δ 18 OBSi after 4 ka, co-incident with neo-glacial-cooling which is not mirrored in the insolation curve. The relatively stable insolation during this time suggests that the accelerated decrease visible in δ 18 OBSi records must be driven by other factors.

Conversely, December insolation shows an anticorrelation with the δ 18 OBSi records. However, as both the absolute values and the changes in December insolation are an order of magnitude lower than those of June insolation, a decisive influence of December insolation on δ 18 OBSi records can be ruled out. This is in good agreement with previous works, claiming that the δ 18 OBSi proxy yields a summer-dominated signal (Shemesh et al., 2001a;[START_REF] Kostrova | Climate and environmental changes of the Lateglacial transition and Holocene in northeastern Siberia: Evidence from diatom oxygen isotopes and assemblage composition at Lake Emanda[END_REF]. It has to be noted that the records displayed still stem from different latitudes and the insolation patterns are not identical at all these sites. A decrease of summer insolation, however, is generally the case for high latitude regions throughout the Holocene. Temperature reconstructions by [START_REF] Vinther | Holocene thinning of the Greenland ice sheet[END_REF] using δ 18 O data from ice cores at Agassiz ice cap and Greenland (between 65°N and 80°N) show a pronounced Tair increase of about 5°C at the beginning of the Holocene until 10 kyr BP, followed by a stable phase until 7 kyr BP. While the NH and Eurasian trends do not feature this increase during the early Holocene, they 535 do show a relatively stable phase from 10 kyr BP to 7 kyr BP. After 7 kyr BP, both the NH δ 18 OBSi trend and the NH Tair reconstruction feature a decrease of circa 2°C and 1.5‰ VSMOW, respectively. As the present-day global average Tairdependent fractionation in precipitation amounts to 0.695‰/°C [START_REF] Dansgaard | Stable isotopes in precipitation[END_REF], a 1.5‰ δ 18 O decrease would, thus, https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. correspond to a 2°C cooling, the same Tair-change as found by [START_REF] Vinther | Holocene thinning of the Greenland ice sheet[END_REF]. This good agreement of δ 18 OBSi combined trends (NH and Eurasia) and the Tair-reconstructions by [START_REF] Vinther | Holocene thinning of the Greenland ice sheet[END_REF] suggests summer Tair to have a major impact on δ 18 OBSi records on millennial time scales.

Multi-proxy-based temperature reconstructions by [START_REF] Marcott | A Reconstruction of Regional and Global Temperature for the Past 11,300 Years[END_REF] (regional stack 30°N to 90°N) also show a temperature increase until 10 kyr BP, followed by a stable phase until ca. 7 kyr BP and a decrease of ca. 2°C thereafter. This temperature reconstruction includes a much broader geographical focus as well as different archives. Thus, the stable phase from 10 kyr BP to 7 kyr BP and a maximum around 7 kyr BP are shared features of the δ 18 OBSi trends of this work, the ice core reconstruction from [START_REF] Vinther | Holocene thinning of the Greenland ice sheet[END_REF] and the temperature reconstructions by [START_REF] Marcott | A Reconstruction of Regional and Global Temperature for the Past 11,300 Years[END_REF]. However, the early Holocene maximum of the δ 18 OBSi trends is not represented in reconstructions by [START_REF] Vinther | Holocene thinning of the Greenland ice sheet[END_REF] and [START_REF] Marcott | A Reconstruction of Regional and Global Temperature for the Past 11,300 Years[END_REF]. This discrepancy might reflect different regional biases of [START_REF] Marcott | A Reconstruction of Regional and Global Temperature for the Past 11,300 Years[END_REF] and this work, which is also in line with the different timing of Holocene maxima in the δ 18 OBSi data (Fig. 8). Additionally, it might also indicate other influences than Tair on the δ 18 OBSi signal in the frame of a more complex climate system during the early Holocene. Given the discrepancy between temperature reconstructions and δ 18 OBSi records in the early Holocene, it is likely that the influence of factors other than Tair is especially pronounced in the early Holocene. The LR04 stack of the δ 18 O of benthic foraminifera [START_REF] Lisiecki | A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records[END_REF] features continuously decreasing δ 18 O throughout the Holocene which is in accordance with the combined Eurasian δ 18 OBSi trend.

Pollen records may help to further investigate this issue as they stem from terrestrial environments, often even also from lake sediments. Moreover, they offer a similar temporal and geographical focus compared to our records, extending to high latitudes. For this comparison we have used a pollen data compilation by [START_REF] Herzschuh | Xianyong: Northern Hemisphere temperature and precipitation reconstruction from taxonomically harmonized pollen data set with revised chronologies using WA-PLS and MAT (LegacyClimate 1.0)[END_REF] comprising data from 864 records from sites north of 45°N for the Holocene. Changes of annual Tair and July Tair relative to modern values were retrieved from the pollen dataset. Annual and July Tair show similar patterns with a pronounced early Holocene increase, followed by middle Holocene maximum and a less pronounced decrease until the present day. Both the middle Holocene maximum and the subsequent decrease of Tair are in good agreement with the combined Eurasian δ 18 OBSi trend (Fig. 8A,8D). This further supports a substantial influence of Tair on the δ 18 OBSi signal. However, the early Holocene maximum of δ 18 OBSi in our combined NH and Eurasian trends is not reflected by pollen-based reconstructions. Caution has to be applied when using pollen-based climate reconstructions for comparison because vegetation changes may lag behind changes of climatic variables [START_REF] Herzschuh | Glacial legacies on interglacial vegetation at the Pliocene-Pleistocene transition in NE Asia[END_REF]. In summary, the similarity of our combined δ 18 OBSi trends with NH temperature reconstructions and insolation data allows for deducing a clear link to summer Tair for the Holocene records.

It has to be stressed that this influence of Tair may act both directly and indirectly. Directly by means of the temperaturedependent fractionation during precipitation formation, and indirectly via the impact of temperature on the hydrological cycle and δ 18 O of water compartments. This includes factors such as moisture origin, precipitation intermittency and atmospheric circulation patterns which have been described as key drivers in numerous case studies. This underlines the importance of scale when assessing δ 18 OBSi records, both temporally and spatially. On a millennial and hemispheric scale, Tair can be identified as one main driver of δ 18 OBSi records even though the signal formation is generally complex and challenging to interpret with https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. individual records. A Tair influence for certain records on the millennial scale is therefore not necessarily a contradiction to the findings of the original publications which may have attributed the record's signal to other factors (e.g., hydrological processes) on shorter timescales.

Frontiers and Challenges (Records older than MIS 1)

Further back in time than MIS 1, coverage with δ 18 OBSi records is generally limited. As MIS 1 (N=37) and MIS 2 (N=18) have the highest numbers of records, they offer the best possibility of comparing glacial and interglacial records. Records beyond MIS 2 are very sparse and do not allow for filtering and generating common trends. Here, the interpretation has to rely on comparison of individual datasets. There are few (N=16) records only which cross the MIS 1-MIS 2 boundary and these records cover neither MIS 1 nor MIS 2 entirely. A quantitative comparison of MIS 1 and MIS 2 is therefore difficult. Again, caution has to be applied due to the fact that these records stem from lakes with different hydrological and climatic settings (i.e. maritime Alaskan sites vs. continental Siberian sites).

The most promising approach for investigating MIS 1 and MIS 2 is extending the NH MIS 1 datasets to the past (Fig. 9). Five NH δ 18 OBSi records (#3,8,15,24,25) extend back from MIS 1 into MIS 2 and offer insight into the hydroclimate history of Siberia during the last glacial and the deglaciation. Most of these records display a maximum near the MIS 1-MIS 2 boundary and a decrease of δ 18 OBSi with increasing age in MIS 2, suggesting decreasing Tair. This is the case for all records except #3 which displays a relative δ 18 OBSi maximum at ca. 16 kyr BP. This maximum may also be caused by dry conditions outperforming the effect of lower Tair. Only records #3, #8 and #15 extend beyond 13 kyr BP. Both #3 and #15 reach their absolute minima at 23 kyr BP and 24 kyr BP, respectively. Record #8 does not show such a clear pattern and shows a relative maximum at 25 kyr BP instead. This is likely due to the complex hydrological setting (alternating between open and closed at present) which may have changed over these timescales. Generally, most records suggest a lower δ 18 OBSi in MIS 2 when compared to MIS 1. This is remarkable as glacial and interglacial periods feature different environments, atmospheric circulation patterns and likely hydrological settings (e.g. formation or closure of outflows from lakes, lake level fluctuations). Potentially, lower δ 18 OBSi values would be conform with either lower Tair or more humid conditions. In case of MIS2, generally associated with cold and dry conditions, a lower Tair is the more plausible scenario.

Considering all records covering the MIS 1-MIS 2 boundary, without geographical or hydrological constraints, yields a less clear picture (Fig. 9). The calculated offsets of MIS 1 and MIS 2 datapoints may show both higher and lower δ 18 OBSi values in MIS 2 compared to MIS 1. Again, an MIS 2 climate colder and drier than Holocene (MIS 1) may produce either lower or higher δ 18 OBSi values due to opposing effects of Tair and evaporation. A geographical pattern of either of these effects prevailing is not obvious, which suggests that rather than the climatic background, the individual hydrological settings of the lakes in question play a prominent role in determining the δ 18 OBSi signal. This supports the approach of using lakes with both similar latitudinal and hydrological characteristics. Further back in time than MIS 2, records become even scarcer, as do lake sediments in general. Additionally, lake sediments covering these time periods often lack sufficient diatoms, especially in cold stages, i.e. Lake Baikal during MIS 4 (Mackay et al., 2008;[START_REF] Mackay | A reassessment of late glacial -Holocene diatom oxygen isotope record from Lake Baikal using a geochemical mass-balance approach[END_REF][START_REF] Mackay | Hydrological instability during the Last Interglacial in central Asia: a new diatom oxygen isotope record from Lake Baikal[END_REF]. Lake El'gygytgyn is a peculiar example of a continuous sedimentation history with δ 18 OBSi showing glacial-interglacial cycles at least back to MIS 9 (Chapligin et al., 2012b), which have been attributed by the authors to Tair changes. In addition to glacialinterglacial cycles, it is also possible to compare δ 18 OBSi of interglacials, i.e. MIS 1, MIS 5, MIS 11, when diatoms during cold stages are absent. In the sedimentary records of Lake El'gygytgyn, Chapligin (2012) investigated the δ 18 OBSi differences between the warm stages MIS 1, MIS 5 and MIS 11 and found MIS 11 as warmest interglacial. This interpretation has been supported by pollen-based Tair reconstructions by [START_REF] Melles | 2.8 Million Years of Arctic Climate Change from Lake El’gygytgyn[END_REF] and underlines the applicability of the δ 18 OBSi proxy on glacial-interglacial timescales. Studies on Lake Baikal have also investigated past interglacials and have addressed changes in precipitation intermittency and cooling events during MIS 11 [START_REF] Mackay | Reconstructing hydrological variability in Lake Baikal during MIS 11: an application of oxygen isotope analysis of diatom silica[END_REF]. During MIS 5, millennial-scale variability is suggested to have been more stable than during MIS 1 [START_REF] Mackay | Hydrological instability during the Last Interglacial in central Asia: a new diatom oxygen isotope record from Lake Baikal[END_REF]. Older δ 18 OBSi records do exist and often rely on paleo-lakes i.e. Ribains Maar, Baringo-Bogoria Basin, Makgadikgadi and Dethlingen (Shemesh et al., 2001b;[START_REF] Koutsodendris | A short-term climate oscillation during the Holsteinian interglacial (MIS 11c): An analogy to the 8.2ka climatic event?[END_REF]Wilson et al., 2014b;[START_REF] Schmidt | Paleolimnological features of a mega-lake phase in the Makgadikgadi Basin (Kalahari, Botswana) during Marine Isotope Stage 5 inferred from diatoms[END_REF]. These offer the possibility of extending the picture past still existing lakes, however lacking (present) hydrological constraints, which makes their interpretation and comparison to other, better-constrained records more challenging. Further research on δ 18 OBSi is therefore needed in order to complement the picture and provide insight into past climate and environmental conditions in continental regions, particularly valuable for high latitude and high-altitude regions poorly covered by other proxy data.

Hydrologically open lakes with a long, continuous sedimentation history are most promising for extending climate reconstructions further into the past.

Conclusions

In this study, we have identified and gathered the existing lacustrine δ 18 OBSi records published to date in order to generate an added value by unifying them into a first δ 18 OBSi data compilation. We have identified 53 δ 18 OBSi records derived from 71 publications. These records stem from the entire globe with their geographical distribution focusing on high altitude and high latitude lacustrine environments. Diatoms bear the advantage of being available in dilute, non-alkaline lakes common in these environments. Regional clusters of records (e.g. northern Eurasia, East Africa) indicative of the research foci of the individual research groups employing the δ 18 OBSi proxy allow for generating regional subsets of data. Temporal coverage stretches from sub-recent timescales to the Pliocene which highlights the applicability of δ 18 OBSi on different timescales. Best coverage is available in MIS 1 which is linked to the age of lakes, and hence the availability of lake sediments, especially in high latitudes.

Moreover, biogenic silica (here entirely diatom-based) is most abundant during warm periods (interstadials and interglacials) compared to colder periods. The interpretability of δ 18 OBSi records relies on regional setting, hydrological constraints of individual lakes and catchments, and preferably supported by isotope measurements of present lake water. Most δ 18 OBSi records stem from open lakes (N= 41), suggesting for these lakes a negligible influence of lake evaporation. In contrast, closed lakes (N=12) and paleo-lakes (N=9) have been investigated less. It has to be noted that a lake's ontogeny and hydrology may change throughout time and thus, hydrological changes constitute an approach for interpreting these δ 18 OBSi records. Spatial resolution of the δ 18 OBSi records is determined by the size of the lake and its corresponding catchment with lake water effectively integrating the input signal. While this regional signal may integrate large areas such as in the case of lake Baikal, most catchments (N=18) are <100 km 2 , suggesting a locally confined signal for these lakes. Regarding temporal resolution, most records feature sampling resolutions which by far exceed tres, suggesting sampling resolution to be the decisive factor in determining a record's signal. However, in case of tres >100yrs, lakes may be subject to increased lake evaporation. (hydrologically open lakes with tres<100 yrs), we find a common pattern throughout the Common Era at the centennial scale, which we attribute to changing hydroclimate conditions. Changes are similar between Eurasia and North America, but they still differ in the timing of δ 18 OBSi maxima. Generally, the combined Eurasian δ 18 OBSi record seems to include major climate episodes during this period, including Roman Climate Optimum, Migration Period Pessimum, Medieval Climatic Anomaly (MCA) and Little Ice Age. An effect of recent warming is not visible in the Common Era data, likely due to a lack of records meeting the filter criteria.

For the entire Holocene (MIS 1) in Eurasia and the NH (for hydrologically open lakes with tres<100 yrs), we find a common decreasing δ 18 OBSi trend on the millennial scale which roughly follows summer insolation. The timing of the absolute δ 18 OBSi maxima of individual records in Eurasia differs and shows an east-west gradient with eastern Eurasian records featuring earlier Holocene maxima compared to western Eurasian records. Holocene minima occur within the last 2000 kyrs for all Eurasian records. North American records diverge from this MIS 1 pattern with later maxima and earlier minima. This behaviour is likely linked to atmospheric circulation patterns as also described by the authors of the individual records.

Extending the millennial-scale trend of Eurasian records into MIS 2 shows generally lower δ 18 OBSi values in MIS 2, suggesting lower Tair (and not P/E) in Glacial times, also visible in most other records that act on glacial-interglacial timescales. The applicability of the δ 18 OBSi proxy beyond MIS 2 is generally constrained by the availability of lake sediments and the abundance of diatoms in the respective sediments. Lake El'gygytgyn, as a prime example of hydrological continuity, displays glacialinterglacial cycles in the δ 18 OBSi record, supporting Tair being a prominent driver of δ 18 OBSi on millennial time scales. In Glacial periods, diatoms abundances are low, and this limitation does sometimes not allow for oxygen isotope analysis. However, comparison between interglacials where diatoms are generally more abundant, is feasible, i.e. at Lake Baikal and Lake El'gygytgyn. In summary, we demonstrate the applicability and intercomparability of combined δ 18 OBSi records into a first lacustrine δ 18 OBSi compilation allow for paleoclimate reconstructions, when accounting for regional offsets, different temporal resolutions and hydrological backgrounds. δ 18 OBSi records compiled in this study are, thus, an important tool for reconstructing paleoclimate across the globe and across a variety of time scales. In NH extratropic regions, their Tair-driven, quantitative signal makes them especially usable for use in conjunction with paleoclimate models. Future research would be most valuable in complementing the existing data with longer records (covering MIS 2 and beyond) as well as records from regions underrepresented thus far (especially the southern hemisphere).

Figure 1 .

 1 Figure 1. Schematic overview of select reservoirs and processes within the global water cycle influencing the δ 18 OBSi signal of records. (a) Overview of the global water cycle with reservoirs and processes. (b) Depleting and enriching factors influencing δ 18 O values in precipitation, lake water, and biogenic silica. Corresponding fractionation processes are indicated on the right-hand side.100

  https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License.

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Figure 2 .

 2 Figure 2. Temporal coverage by records and datapoints during MIS 1 -MIS 5. a) Total number of datapoints available 320 during each Marine Isotope Stage. b) Temporal coverage of records.

Figure 3 .

 3 Figure 3. World map depicting the locations of δ 18 OBSi records with chronology. Note that one location may correspond to more than one records. ©ESRI 2022

  to regional averages. However, most of the records (N=18) stem from lakes with catchments <100 km², suggesting rather local signals. While single local signals represent small areas, different local signals may well correlate on continental and hemispheric scales.

Figure 4 .

 4 Figure 4. A) Depiction of corresponding lake and catchment sizes of the records compiled within this study. One lake may correspond to more than one records. Note that records from Paleo-lakes and lakes with incomplete information on lake and catchment size were not considered for this figure (N=33). B) Depiction of corresponding sampling intervals and tres. Note that records from lakes without information on tres were not considered for this figure (N=37).

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Figure 5 .

 5 Figure 5. Common Era Northern hemispheric records (45-90 N) compiled in this study. A) Original records, B) data binned to 200 year intervals, only showing records covering at least 7 bins, C) binned records with mean of individual records removed, D) filtered for records from open lakes only, E) filtered for records from lakes with tres<100 yrs, F) NH trend, calculated as mean of all records in each bin. Shadings show 1 and 2 standard deviations, respectively. G) North American and H) Eurasian trend.

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Figure 6 .

 6 Figure 6. MIS1 Northern hemispheric records (45-90 N) compiled in this study. A) Original records, B) data binned to 1-kyr intervals, only showing records covering at least 7 bins, C) binned records with mean of individual records removed, D) filtered for records from open lakes only, E) filtered for records from lakes with tres<100 yrs, F) NH trend, calculated as mean of all records in 455

  https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License.Eurasia. There are also individual records, however, which do show two peaks within the Holocene e.g. Lake Bolshoye Shchuchye from the Polar Ural Mountains (#16). Records from Alaska feature later δ 18 OBSi maxima (5 kyr BP and 7 kyr BP, respectively).

Figure 7 .

 7 Figure 7. Timing of maxima and minima of binned records in the Holocene. Filter criteria are the same as indicated in Fig. 10 and only records covering at least 10 bins have been considered. ©ESRI 2022

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Figure 8 .

 8 Figure 8. Combined Trend of δ18OBSi compared to other climate reconstructions. A) Greenland ice sheet temperature reconstruction, B) Multi-proxy temperature reconstruction (30-90 N), C) global stack of δ18O from benthic foraminifera, D) temperature reconstruction (45-90 N) based on pollen data, E) Insolation anomaly for June and December, F) Combined Eurasian 530

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Figure 9 .

 9 Figure 9. Comparison of MIS 1 and MIS 2 data. a) continuation of records from NH Stack (see Fig. 6F) into MIS 2. b) Difference between MIS 1 and MIS 2 means of all individual records covering the MIS 1 -MIS 2 boundary. ©ESRI 2022

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  https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. Accounting for offsets and different temporal resolution of records and filtering for similar hydrological settings

  Figure A1. Geographical distribution of published δ 18 OBSi records and year of publication (N=64).

Figure A2 .

 A2 Figure A2. Overview of the dating methods used for age-model creation of published δ 18 OBSi time-series (N=64). Note that a single record can rely on multiple methods.

Figure A3 .

 A3 Figure A3. Overview of isotope hydrological background information considered in publications presenting δ 18 OBSi records (N=64).690

Figure A4 .

 A4 Figure A4. Hydrological settings of the lakes corresponding to the δ 18 OBSi records compiled in this study, as indicated in the original publications (N=64). Owing to a lack of present constraints, paleo lakes are listed as a separate category.

Table A1 . Overview of the records compiled and analyzed in this study. Lake basin parameters shown are taken from the HydroLakes database ((Messager et al., 2016) for consistency. In 697 case of major discrepancies between the HydroLakes database and the values provided by individual case studies, values of case studies are given in brackets and marked with an asterisk.

 A1 ://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. ://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License. doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License.

	698	No. Archive No. Archive	Lake Lake	Short Reference Short Reference	Lat. [dec deg] Lat. [dec deg]	Lon. [dec deg] Lon. [dec deg]	Water depth [m] Water depth [m]	Altitude [m asl] Altitude [m asl]	Lake Area [km2] Lake Area [km2]	Catchment Area [km2] Catchment Area [km2]	Residence time [a] Residence time [a]	Chron. Chron.	Rec_ID Rec_ID
	699	Lake 47 Lake Lake 48 Lake	Lake Brazi Laguna Zacapu Nar Gölü Lake Stuor	Magyari et al. (2013) Leng et al. (2005) Dean et al. (2018) Rosqvist et al. (2013)	45.40 19.83 38.34 67.85	22.90 -101.79 34.46 19.68	1.1 2.0 25.0 6	1740 1987 1369 559	0.004 0.23 0.52 0.28	0.10 66 3.5 0.5	0.5 0.037 15 5.6	Y N Y Y	TDB1 ZAC3 NAR0110 LSG1
	700	Lake 49 Lake	Lake Emanda Goussasjavri Lake Spaime	Kostrova et al. (2021) Rosqvist et al. (2013)	65.28 63.12	135.75 12.32	14.6 4	654 887	33.10 0.03	118 3.5	26 0.04	Y Y	Co1412 LS1
		No. Archive Lake 50 Lake 1 Paleo Lake Baringo-Bogoria Basin Wilson et al. (2014b) Lake Short Reference Baunt Lake Harding et al. (2020) Laguna Zacapu Leng et al. (2005) Lake Sunken Island Lake Broadman et al. (2020b) 51 Lake Baikal Swann et al. (2018) 2 Lake Baikal Mackay et al. (2008) Lake Grandfather Lake Hu and Shemesh (2003) 52 Paleo Lake Dethlingen Koutsodendris et al. (2012) 3 Lake El'gygytgyn Chapligin et al. (2012b) Lake Lago Chungara Hernandez et al. (2008); Hernandez et al. (2010); 53 Lake Yellowstone Lake (Brown et al., 2021)	Lat. [dec deg] 55.19 19.82 0.55 60.59 51.77 53.70 60.80 52.96 67.50 -18.25 44.54	Lon. [dec deg] 113.03 -101.79 35.94 -150.89 104.42 108.35 -158.52 10.14 172.08 -69.17 -110.39	Water depth [m] 33 8 7 1360 321 20 170 40 61	Altitude [m asl] 1052 1987 1178 84 449 449 142 65 471 4556 2360	Lake Area [km2] 112 0.23 0.44 31968 31968 0.35 119 21.27 340	Catchment Area [km2] 10256 66 28.3 569176 569176 292 265 2579	Residence time [a] 1.1 0.037 0.18 375 375 64 289 (15*) 21 (14*)	Chron. Y N Y Y Y Y Y N Y Y Y	BNT1418 ZK2 Rec_ID SILMC BAIK13 BD4 GL1 D110 BDP962 Lz1024 LG1 YL16-2C
		4 Lake	Baikal	Mackay et al. (2013) Hernandez et al. (2011); Hernandez et al. (2013)	53.96	108.91		386		449	31968	569176	375	Y	CON016032
		5 Paleo Lake Ribains Maar Lake Lake Gosciaz	Shemesh et al. (2001b) Rozanski et al. (2010)	44.84 52.58	3.82 19.35	25		1074 63	0.38	20.6	0.51	N Y	RM1 G702
		6 Paleo Lake Makgadikgadi Lake Linsley Pond	Schmidt et al. (2017) Shemesh and Peteet (1998)	-20.29 41.30	24.27 -72.75	9		8	934	0.93			N Y	MBG1 LP1
		7 Lake Lake	Lake Pinarbasi Lake Ladoga	Leng et al. (2001) Kostrova et al. (2019)	37.47 60.98	33.12 30.68	111		1000	0.002 17444	279581	11	Y Y	PN94C Co1309
		8 Lake Lake	Kotokel Lake Laguna Verde Alta	Kostrova et al. (2013a); Polissar et al. (2006)	52.78 8.85	108.12 -70.87	3	4	453 4215	65.7	170	58	Y Y	KTK2 LVA1
		Lake 9 Lake Lake	Garba Guracha Baikal Simba Tarn	Kostrova et al. (2013b); Bittner et al. (2021) Kostrova et al. (2014); Kostrova et al. (2016) Kalmychkov et al. (2007) Barker (2001)	6.88 53.75 -0.15	39.88 108.41 37.32	5	348	3950 449 4959	0.15 31968 0.00	0.15 569176	375	Y N Y	BALGGU17 1 LB0301 ST1
		10 Lake Lake	Baikal Heart Lake	Kalmychkov et al. (2007) Bailey et al. (2018)	53.39 51.85	107.53 -176.69	7.6	233	449 60	31968 0.25	569176 8	375 0.038	N Y	LB0402 HL1
		11 Lake Lake	Lake Rutundu Mica Lake	Street-Perrott et al. (2008) Schiff et al. (2009)	-0.03 60.96	37.45 -148.15	58	11	3078 93	0.40 0.63	3.2	0.46	Y Y	R1 MC2
		12 Paleo Lake Les Echets Lake Lake 850	Ampel et al. (2009) Shemesh et al. (2001a)	45.90 68.25	4.93 19.12	8		267 850		0.5		Y Y	EC1 L850
		13 Lake Lake	Lake Challa Lake Chuna	Barker et al. (2011) Jones et al. (2004)	-3.32 67.95	37.42 32.48		94	878 475	4.12 0.13	6.4 2	86 0.30	Y Y	LCHA1 LC1
		14 Lake Lake	Lake Malawi Schrader Pond	Barker et al. (2007) Broadman et al. (2020a)	-9.98 69.36	34.23 -145.08		363	476 869	29544	128727	219	Y Y	M982P SCP162A
		15 Lake Lake	El'gygytgyn Lake Tilo	Chapligin et al. (2012b) Lamb et al. (2005)	67.66 7.06	172.14 38.10	177.0 10	471 1551	119 0.66	292 144	64 0.15	Y Y	Lz1029 LT1
		16 Lake Lake	Bolshoye Shchuchye Nettilling Lake	(Meyer et al., 2022) Narancic et al. (2016) Chapligin et al. (2016b);	67.88 66.50	66.32 -70.50	132.0 14	186 18	11.80 4872.70	227 63400	5 5.5	Y N	Co1321 Ni2B
		17 Paleo Lake Tauca Lake Lake Pupuke	Quesada et al. (2015) Heyng et al. (2015)	-19.16 -36.78	-68.20 174.77	58		3685 11	1.01	1	5.8	Y Y	PTAU1 P210/P260
		18 Lake Lake	Laguna Verda Baja Vuolep Allakasjaure	Polissar et al. (2006) Jonsson et al. (2010)	8.86 68.18	-70.87 18.17	11	5	4170 991	1.01	1	5.8	Y Y	LVB1 VA
		19 Lake Lake	Tonsberg Lake Lac Petit	Rosqvist et al. (1999) Cartier et al. (2019a)	-54.17 44.11	-36.69 7.19	7		70 2200	0.01 0.018	6		Y Y	TL1 PET09P2
		20 Lake Lake	Baikal Two-Yurts Lake	Mackay et al. (2011) Meyer et al. (2015a)	51.58 56.82	104.85 160.11	600.0 28	449 264	31968 0.02	569176 6	375	Y Y	CON016053 PG1857
		21 Lake Lake	Small Hall Tarn Hausberg Tarn	Barker (2001) Rietti-Shati et al. (1998)	-0.15 -0.15	37.35 37.30			4289 4369	11.39	206	1.9	Y Y	SHT1

httpshttps701 https://

Acknowledgements

PM is funded by German Ministry of Education and Research via the Palmod2-Projek (01LP1923B). HB is funded by the Academy of Finland (grant 348536). AH is funded by the Spanish Ministry of Science and Innovation through the Ramón y Cajal Scheme (RYC2020-029253-I). We thank xx (anonymous) reviewers whose comments helped improving the manuscript.

We also thank all scientists and technicians developing and advancing the research field of oxygen isotopes in diatom silica. https://doi.org/10.5194/cp-2022-96 Preprint. Discussion started: 24 January 2023 c Author(s) 2023. CC BY 4.0 License.

Data availability

The dataset is being submitted to PANGAEA.

LCHA1 Lake Lake Challa composite 03-2K; 05-4P [START_REF] Barker | Seasonality in equatorial climate over the past 25 k.y. revealed by oxygen isotope records from Mount Kilimanjaro[END_REF] M982P Lake Lake Malawi single M98-2P [START_REF] Barker | Century-to-millennial scale climatic variability in Lake Malawi revealed by isotope records[END_REF] SHT1 Lake Small Hall Tarn [START_REF] Barker | A 14,000year oxygen isotope record from diatom silica in two alpine lakes on Mt. Kenya[END_REF] ST1 Lake Simba Tarn [START_REF] Barker | A 14,000year oxygen isotope record from diatom silica in two alpine lakes on Mt. Kenya[END_REF] BALGGU171 Lake Garba Guracha composite BAL-GGU17-1A; BAL-GGU17-1B

Competing Interests

The authors declare that they have no conflict of interest.

Disclaimer

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