A 20-year study of melt processes over Larsen C Ice Shelf using a
high-resolution regional atmospheric model: Part 2, Drivers of surface
melting
Abstract
Quantifying the relative importance of the atmospheric drivers of
surface melting on the Larsen C ice shelf is critical in the context of
recent and future climate change. Here, we present analysis of a new
multi-decadal, high-resolution model hindcast using the Met Office
Unified Model (MetUM), described in part 1 of this study. We evaluate
the contribution of various atmospheric conditions in order to identify
the most significant causes of melting over the recent past. We find the
primary driver of surface melting on Larsen C is solar radiation. Foehn
events are the second most important contributor to surface melting,
especially in non-summer seasons when relatively less solar radiation is
received at the surface of the ice shelf. Thirdly, cloud influences
surface melting via its impact on the surface energy balance (SEB); when
the surface temperature is warm enough, cloud can initiate or prolong
periods of melting. Lastly, large-scale circulation patterns such as the
Southern Annular Mode (SAM), El Niño Southern Oscillation (ENSO) and
Amundsen Sea Low (ASL) control surface melting on Larsen C by
influencing the local meteorological conditions and SEB. These drivers
of melting interact and overlap, for example, the SAM influences the
frequency of foehn, which are commonly associated with leeside cloud
clearances and sunnier conditions. Ultimately, these drivers matter
because sustained surface melting on Larsen C could destabilise the ice
shelf via hydrofracturing, which would have consequences for the fate of
the ice shelf and sea levels worldwide.