Abstract

This study investigates the sensitivity of modeled surface melt and subsurface heating on the Antarctic ice sheet to a new spectral snow albedo and radiative transfer scheme in the Regional Atmospheric Climate Model (RACMO2), version 2.3p3 (Rp3). We tune Rp3 to observations by performing several sensitivity experiments and assess the impact on temperature and melt by changing one parameter at a time. When fully tuned, Rp3 compares well with in situ and remote sensing observations of surface mass and energy balance, melt, temperature, albedo and snow grain specific surface area. Furthermore, the introduction of subsurface heating in Rp3 significantly improves the snow temperature profile. Near surface snow temperature is especially sensitive to the prescribed fresh snow specific surface area and fresh dry snow metamorphism. These processes, together with the refreezing grain size and subsurface heating, are important for melt around the margins of the Antarctic ice sheet. Moreover, small changes in the albedo and the aforementioned processes can lead to an order of magnitude overestimation of melt, locally leading to runoff and a reduced surface mass balance.

Highlights

  • The contemporary climate of the Antarctic ice sheet (AIS) has been relatively stable, but recently the ice sheet has started losing mass at an accelerated pace (Shepherd et al, 2018)

  • This study investigates the sensitivity of modeled surface melt and subsurface heating on the Antarctic ice sheet to a new spectral snow albedo and radiative transfer scheme in the Regional Atmospheric Climate Model (RACMO2), version 2.3p3 (Rp3)

  • Several Antarctic heat records have been broken in the past decade (Bozkurt et al, 2018), with an all-time record for continental Antarctica of 18.4 ◦C observed at the tip of the Antarctic Peninsula (AP) in February 2020 (WMO, 2020)

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Summary

Introduction

The contemporary climate of the Antarctic ice sheet (AIS) has been relatively stable, but recently the ice sheet has started losing mass at an accelerated pace (Shepherd et al, 2018). The temperature of and melt in the (sub)surface snow of the AIS is sensitive to snow grain conditions and subsurface heating This sensitivity can be investigated locally by using in situ observations, but a polar regional climate model is required to study it for the entire ice sheet. 45 In this study, we use the polar (p) version of the Regional Atmospheric Climate Model (RACMO2) to analyse the impact of a spectral snow albedo scheme on the (sub)surface temperature and melt of the AIS. To investigate the sensitivity of the AIS to (sub)surface heating and snow conditions, we conduct several sensitivity experiments with Rp3, changing one parameter at a time to assess the impact on melt and temperature In this manuscript, we first discuss RACMO2 and the sensitivity experiments in more detail in Sect.

Methods and data
Surface mass balance and energy budget
RACMO2 experiments
Observational data
Results
Specific surface area comparison
Surface energy balance and albedo analysis
Comparison with an EBM
Findings
Summary and conclusions

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