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We document the isotopic evolution of near-surface snow at the East Greenland Ice Core Project (EastGRIP) ice core site in northeast Greenland using a time-resolved array of 1 m deep isotope (δ18O , δD) profiles. The snow profiles were taken from May–August during the 2017–2019 summer seasons. An age–depth model was developed and applied to each profile, mitigating the impacts of stratigraphic noise on isotope signals. Significant changes in deuterium excess (d) are observed in surface snow and near-surface snow as the snow ages. Decreases in d of up to 5 ‰ occur during summer seasons after deposition during two of the three summer seasons observed. The d always experiences a 3 ‰–5 ‰ increase after aging 1 year in the snow due to a broadening of the autumn d maximum. Models of idealized scenarios coupled with prior work indicate that the summertime post-depositional changes in d (Δd) can be explained by a combination of surface sublimation, forced ventilation of the near-surface snow down to 20–30 cm , and isotope-gradient-driven diffusion throughout the column. The interannual Δd is also partly explained with isotope-gradient-driven diffusion, but other mechanisms are at work that leave a bias in the d record. Thus, d does not just carry information about source-region conditions and transport history as is commonly assumed, but also integrates local conditions into summer snow layers as the snow ages through metamorphic processes. Finally, we observe a dramatic increase in the seasonal isotope-to-temperature sensitivity, which can be explained solely by isotope-gradient-driven diffusion. Our results are dependent on the site characteristics (e.g., wind, temperature, accumulation rate, snow properties) but indicate that more process-based research is necessary to understand water isotopes as climate proxies. Recommendations for monitoring and physical modeling are given, with special attention to the d parameter. [ABSTRACT FROM AUTHOR] more...

We document the isotopic evolution of near-surface snow at the EastGRIP ice core site in the Northeast Greenland National Park using a time-resolved array of 1-m deep isotope (δ18rscript> O , δ D) profiles. The snow profiles were taken from May–August during the 2017–2019 summer seasons. An age-depth model was developed and applied to each profile mitigating the impacts of stratigraphic noise on isotope signals. Significant changes in deuterium excess (d) are observed in surface snow and near-surface snow as the snow ages. Decreases in d of up to 5 ‰ occurs during summer seasons after deposition during two of the three summer seasons observed. The d always experiences a 3–5 ‰ increase in d after aging one year in the snow due to a broadening of the autumn d maximum. Models of idealized scenarios coupled with prior work (Wahl et al., 2022) indicate that the summertime post-depostional changes in d (Δ d) can be explained with surface sublimation, forced ventilation of the near-surface snow down to 20–30 cm, and isotope-gradient-driven (IGD) diffusion throughout the column. The interannual Δ d is also partly explained with IGD diffusion, but other mechanisms are at work that leave a bias in the d record. Thus, d does not just carry information about source region conditions and transport history as is commonly assumed, but also integrates local conditions into summer snow layers as the snow ages. Finally, we observe a dramatic increase in the seasonal isotope-to-temperature sensitivity occurs, which can be explained solely by IGD diffusion. Our results are dependent on the site characteristics (e.g. wind, temperature, accumulation rate), but indicate that more process-based research is necessary to understand water isotopes as climate proxies. Recommendations for monitoring and physical modeling are given, with special attention to the d parameter. [ABSTRACT FROM AUTHOR] more...

It is highly uncertain how the humidity flux between the snow surface and the atmosphere contributes to the surface mass balance (SMB) of the interior Greenland Ice Sheet (GrIS). Due to sparse observations, evaluations of the simulated humidity flux are limited. Model-based estimates of the humidity flux contribution to the SMB are, therefore, unconstrained and even disagree in magnitude and sign. In this study, we evaluate the regional climate model MAR at the EGRIP (East Greenland Ice-Core Project) site in the accumulation zone of the GrIS. We use a combined dataset of continuous one-level bulk estimates of the humidity flux covering the period 05/2016-08/2019 and direct eddy-covariance humidity flux measurements from all four summer seasons. In summer, we document a bias of too little sublimation (-1.3Wm-2) caused by a cold bias in both air and surface temperature leading to a reduced humidity gradient. In winter, MAR overestimates deposition by about one order of magnitude. This is a consequence of an overestimated temperature gradient in too stable atmospheric conditions compared to observations. Both systematic errors cause a large discrepancy in the annual net humidity flux between the model and observations of -9mmw. eq. yr-1. Remarkably, the simulated net annual humidity flux contributes positively to the SMB, contrary to observations documenting a net sublimation flux. We correct the systematic errors by applying a simple but effective correction function to the simulated latent heat flux. Using this correction, we find that 5.1% of the annual mass gain at the EGRIP site sublimates again, and 4.3% of the total mass gain is deposited vapor from the near-surface air. The estimated net humidity flux contribution to the annual SMB is about -1% (net sublimation) compared to +5.6% for the uncorrected simulation. In summer, the corrected MAR simulation shows that deposition accounts for 9.6% of the total mass gain and that 31% of the total mass gain at the EGRIP site sublimates again. The net fluxes contribute to -32% of the summer SMB. These results demonstrate that the humidity flux is a major driver of the summer SMB in the accumulation zone of the GrIS and highlight that even small changes could increase its importance for the annual SMB in a warming climate. [ABSTRACT FROM AUTHOR] more...

This study investigates how variations in Arctic sea ice and sea surface conditions influence δ18O of present-day Arctic precipitation. This is done using the model isoCAM3, an isotope-equipped version of the National Center for Atmospheric Research Community Atmosphere Model version 3. Four sensitivity experiments and one control simulation are performed with prescribed sea surface temperature (SST) and sea ice. Each of the four experiments simulates the atmospheric and isotopic response to Arctic oceanic conditions for selected years after the beginning of the satellite era in 1979. Changes in sea ice extent and SSTs have different impacts in Greenland and the rest of the Arctic. The simulated changes in central Arctic sea ice do not influence δ18O of Greenland precipitation, only anomalies of Baffin Bay sea ice. However, this does not exclude the fact that simulations based on other sea ice and sea surface temperature distributions might yield changes in the δ18O of precipitation in Greenland. For the Arctic, δ18O of precipitation and water vapour is sensitive to local changes in sea ice and sea surface temperature and the changes in water vapour are surface based. Reduced sea ice extent yields more enriched isotope values, whereas increased sea ice extent yields more depleted isotope values. The distribution of the sea ice and sea surface conditions is found to be essential for the spatial distribution of the simulated changes in δ18O. [ABSTRACT FROM AUTHOR] more...

This study investigates how variations in Arctic sea ice cover influence δ18O of present day Arctic precipitation. This is done using the model isoCAM3, an isotope-equipped version of the National Center for Atmospheric Research Community Atmosphere Model version. Four sensitivity experiments and one control simulation are performed with prescribed SST and sea ice. Each of the four experiments simulates the atmospheric and isotopic response to Arctic oceanic conditions for selected years after the beginning of the satellite era in 1979. Results show that δ18O of precipitation is sensitive to local changes of sea ice concentration. Reduced sea ice extent yields more enriched isotope values while increased sea ice extent yields more depleted isotope values. The distribution of the sea ice cover is essential for the spatial distribution of the simulated changes in δ18O. The experiments of this study show no changes of δ18O for central Greenland. However, this does not exclude that simulations based on other sea ice distributions might yield changes in Greenland δ18O. [ABSTRACT FROM AUTHOR] more...

Can we use the general interest of Arctic climate to introduce students to climate science? In the project IGLO we aim make knowledge about the Arctic climate system more accessible for high school students in Scandinavia. We have done that by developing IGLO, a web portal that helps teachers build their own teaching on Arctic climate change (see more at www. iglo.w.uib.no). IGLO is thus a web portal that works as a tool that makes it easier to plan your own teaching. The purpose is to make it easy and efficient to find high quality material about Arctic climate change. The web portal is especially made to target the teachers. Here updated information about climate changes (and updated animations and graphs) is presented. Furthermore, the web portal is designed for teachers by categorizing all types of teaching material (e.g. "classical" climate change animations) into subjects and themes so that teachers easier can handpick and «build their own teaching». In addition, we give students and other interested people opportunities to follow the life of young scientists by using an Instagram account where young Arctic climate researchers communicate their work. The goal is that project IGLO helps to bridge the gap between Arctic climate researchers and teachers. [ABSTRACT FROM AUTHOR] more...

Ice cores allow us to investigate the past abrupt climate changes. The improved spatial distribution of ice core locations in recent years provide a deeper insight into the glacial conditions and the characteristics of Dansgard-Oeschger (D-O) events, as recorded from the Greenland Ice Sheet. In this study the atmospheric climate conditions during D-O events are explored. Using a set of coupled The Norwegian Earth System Model (NorESM) model simulations that simulate the stadial and interstadial parts of D-O-events, it is investigated how changes in sea ice and ocean conditions influence the Greenland climate conditions. A particular focus is on the atmospheric dynamics relevant for Greenland conditions, such as the jet stream. The seasonal and interannual variability in the simulations are explored and compared to information from ice core records in order to benchmark the model simulations. The use of model simulations makes it possible to explore the dynamics of the D-O events, as recorded by Greenland ice cores, in greater detail. [ABSTRACT FROM AUTHOR] more...