Climatology and Evolution of the Antarctic Peninsula Fohn Wind-induced
Melt Regime from 1979-2018
Abstract
Warm and dry fohn winds on the Antarctic Peninsula (AP) cause surface
melt that can destabilize vulnerable ice shelves. Topographic funneling
of these downslope winds through mountain passes and canyons can produce
localized wind-induced melt that is difficult to quantify without direct
measurements. Our Fohn Detection Algorithm (FonDA) identifies the
surface fohn signature that causes melt using data from twelve Automatic
Weather Stations on the AP, used to train a machine learning model to
detect fohn in 5km Regional Atmospheric Climate Model 2 (RACMO2.3p2)
simulations and in the ERA5 reanalysis model. We estimate the fraction
of AP surface melt attributed to fohn and possibly katabatic winds and
identify the drivers of melt, temporal variability, and long-term trends
and evolution from 1979-2018. We find fohn wind-induced melt accounts
for 3.1% of the total melt on the AP but can be as high at 18% close
to the mountains where the winds are funneled through mountain canyons.
Fohn-induced surface melt does not significantly increase from
1979-2018, despite a warmer atmosphere and more positive Southern
Annular Mode. However, a significant increase (+0.1Gt y-1) and
subsequent decrease/stabilization occurred in 1979-1998 and 1999-2018,
consistent with the AP warming and cooling trends during the same time
periods. Fohn occurrence more than fohn strength drives the annual
variability in fohn-induced melt. Long-term fohn-induced melt trends and
evolution are attributable to seasonal changes in fohn occurrence, with
increased occurrence in summer, and decreased occurrence in fall,
winter, and early spring over the past 20 years.