40 Years of Föhn Winds on the Antarctic Peninsula: Impact on Surface
Melt from 1979-2018
Abstract
Warm and dry föhn winds on the lee side of the Antarctic Peninsula (AP)
mountain range cause surface melt that can destabilize vulnerable ice
shelves. Topographic funneling of these winds through mountain passes
and canyons leads to localized wind-induced melt which is difficult to
identify without direct measurements. Our Föhn Detection Algorithm
(FonDA) identifies the surface Föhn signature using data from twelve
Automatic Weather Stations on the AP and uses machine learning to detect
föhn in 5km Regional Atmospheric Climate Model 2 (RACMO2.3p2) output and
ERA5 reanalysis data. We estimate and compare the climatology and impact
of föhns on the AP surface energy budget, surface melt pattern, and melt
quantity from 1979-2018. We show that föhn-induced melt is strongest at
the eastern base of the AP and the northern portion of the Larsen C ice
shelf. We identify previously unknown wind-induced melt possibly
katabatic in nature on the Wilkins and George VI ice shelves. Neither
RACMO2 nor ERA5 datasets show a significant increase in föhn melt thus
far despite a more positive Southern Annular Mode and increasing surface
temperatures. The warming climate and associated southward shift of
westerly winds on the AP suggest a likely increase in the wind-induced
melt that can densify firn, form melt ponds, and weaken ice shelf
stability, however that trend remains insignificant for the past 40
years.