09 Aug 2023
 | 09 Aug 2023
Status: this preprint is currently under review for the journal TC.

Historical snow and ice temperature observations document the recent warming of the Greenland ice sheet

Baptiste Vandecrux, Robert S. Fausto, Jason E. Box, Federico Covi, Regine Hock, Asa K. Rennermalm, Achim Heilig, Jakob Abermann, Dirk van As, Elisa Bjerre, Xavier Fettweis, Paul C. J. P. Smeets, Peter Kuipers Munneke, Michiel R. van den Broeke, Max Brils, Peter L. Langen, Ruth Mottram, and Andreas P. Ahlstrøm

Abstract. The surface melting of the Greenland ice sheet has been increasing over the last decades due to Arctic atmospheric warming. Surface melt depends on the energy balance which includes the atmospheric forcing but also the thermal budget of the snow, firn and ice near the ice sheet surface. We present a compilation of more than 4500 measurements of ice, snow and firn temperature at 10 m below the surface (T10m) across Greenland spanning from 1912 to 2022. The measurements are either instantaneous or monthly averages. We train an Artificial Neural Network model (ANN) on these observations, weighted by their relative representativity, and use it to reconstruct T10m over the entire Greenland ice sheet. We use 10 year averages and mean annual values of air temperature and snowfall from the ERA5 reanalysis dataset (1950–2022) as model input. The ANN indicates a Greenland-wide positive trend of T10m at 0.2 °C decade-1 during the 1950–2022 period, with a cooling during 1950–1985 (-0.3 °C decade-1) followed by a warming during 1985–2022 (+0.7 °C decade-1). Regional climate models HIRHAM5, RACMO2.3p2 and MARv3.12 show mixed results compared to the observational T10m dataset with mean differences ranging from -0.4 °C (HIRHAM) to 1.3 °C (MAR) and root mean squared differences ranging from 2.8 °C (HIRHAM) to 4.7 °C (MAR). The corresponding values for the ANN are -0.2 °C and 1.7 °C. The observation-based ANN also reveals an underestimation of the subsurface warming trends in climate models for the bare ice and dry snow areas. The subsurface warming brings the Greenland ice sheet surface closer to the melting point, reducing the amount of summer energy input required for melting. Our compilation documents the response of the ice sheet subsurface to atmospheric warming and will enable further improvements of models used for ice sheet mass loss assessment and reduce the uncertainty in projections.

Baptiste Vandecrux et al.

Status: open (until 13 Oct 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Baptiste Vandecrux et al.

Data sets

Greenland ice sheet 10 m subsurface temperature compilation 1912-2022 Baptiste Vandecrux

Greenland ice sheet ice and firn temperature reconstruction at 10 m depth, 1950-2022 Baptiste Vandecrux

Model code and software

Greenland ice sheet subsurface temperature compilation scripts Baptiste Vandecrux

Baptiste Vandecrux et al.


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Short summary
How fast is the Greenland ice sheet warming? In this study, we collected 4500+ temperature measurements at 10 m below the ice sheet surface (T10m) from 1912 to 2022. We trained a machine learning model on these data and reconstructed T10m for the ice sheet during 1950–2022. After a slight cooling during 1950–1985 and the ice sheet warmed at a rate of 0.7 °C per decade until 2022. Climate models showed mixed results compared to our observations and underestimated the warming in key regions.