Foehn Winds on Larsen C Ice Shelf During Polar Night: Impacts on the
Surface Energy Budget and Melt
Abstract
Larsen A and B ice shelves were affected by surface melt which
preconditioned them for rapid disintegration due to hydrofracture and
densification. Recently, warm and dry foehn winds have been discovered
to melt the vulnerable Larsen C Ice Shelf (LCIS) surface via sensible
heat transfer during polar night. The climatological extent and
intensity of polar night surface melt and their effects on the ice
surface energy budget are unknown. Here we quantify the spatial pattern
and temporal variability of foehn winds and associated melt events
during polar night to understand the ice shelf surface mass balance and
indirect implications for ice shelf vulnerability. Our Foehn Detection
Algorithm (FonDA) uses events identified from in situ Automated Weather
Stations (AWS) to calibrate foehn detection from reanalysis data
covering all of Antarctica and Greenland. We present a climatology of
foehn-driven surface melt days, melt water equivalent, fraction of melt
that occurs during polar night, and the surface energy budget.
Preliminary results show that foehns perturb sensible heat fluxes by up
to 300 Wm-2 and surface air temperatures by up to 13 °C in the absence
of shortwave radiation.