Updated Climatology and Surface Mass Balance for the period 1979-2024 of the Antarctic Peninsula using RACMO2.4p1

In this contribution, we present a novel simulation with RACMO2.4p1 of the present-day Antarctic Peninsula (AP) climate, including the surface energy balance (SEB) and surface mass balance (SMB) of glacier and ice shelf surfaces. These model results can be used for estimating freshwater fluxes into the ocean, integrated glacier SMB, and regional climate patterns and trends, for the period 1979-2024 at a 5.5 km grid resolution.

The AP is the warmest region of Antarctica and has been subject to major calving events, notably in 1995 and 2002 (breakup of Larsen A and B, respectively), and in 2017 (breakoff of the A68 iceberg from Larsen C). Mass loss from the Eastern AP is mainly driven by atmospheric warming, as opposed to oceanic warming in the Western AP. Accurate estimates of the SEB and SMB are therefore essential to study the future stability of Eastern AP ice shelves. Our main objective is to explain the simulated and observed melt patterns over Larsen C. To that end, we investigate the temporal trends and spatial variability in SMB components over the simulated period, evaluated with the AntSMB dataset. We connect this to the SEB components, which we evaluate using automatic weather station (AWS) data starting in 2009.

We find good agreement with temperature (bias = -1.1 K, RMSE = 3.6 K) and wind speed (bias = +0.1 m s^-1, RMSE = 2.6 m s^-1) observations from the AntAWS dataset, as well as with the observed melt energy on Larsen C at the IMAU AWS stations (bias = +0.2 W m^-2, RMSE = 6.8 W m^-2). However, substantial biases remain in terms of downward longwave radiation and sensible heat flux (-18.7 W m^-2 and +8.7 W m^-2, respectively). Furthermore, we find large variability in mean annual temperature (SD = 1.3 K), SMB (SD = 61.0 mm w.e. yr^-1), and melt (SD = 100.5 mm w.e. yr^-1) on Larsen C. As a result, the data provide no evidence of statistically significant temporal trends for these variables over the period 1979-2024, which is consistent with earlier reports on natural variability on the AP. Our updated monthly SEB and SMB fields will become publicly available and will form the basis for future studies on the evolution of the Larsen C firn layer.