Global Climate Response to an Abrupt Meltdown of the West Antarctic Ice Sheet

1
Global Climate Response to an Abrupt Meltdown of
the West Antarctic Ice Sheet A. Timmermann and L.
Menviel
Time series of meltwater pulse (black), strength
of the AABW (blue), and transport through Drake
passage (green)? in Sv.
SST anomalies (ºC, shaded) - Windstress anomalies
(Pa, vectors)?
To assess the possible climate impact of a
meltdown of the West Antarctic Ice Sheet, an
idealized experiment was conducted with LOVECLIM,
an earth system model of intermediate complexity.
A meltwater pulse equivalent to a 6-m sea-level
rise over 200 years (left panel) was added in the
Southern Ocean (158ºE-60ºW, 80ºS-70ºS). This
addition of freshwater decreases surface density
and increases stratification of the Southern
Ocean, inhibiting Bottom Water formation. The
Antarctic Circumpolar Circulation transport is
sharply reduced due to a weaker meridional
density gradient. Right panel shows sea surface
temperature anomalies and windstress anomalies
100 years into the experiment. The Southern
Hemisphere upper ocean regions have cooled by up
to 6ºC due to the greater stratification and the
sea ice margin stretches further equatorward. The
Southern Hemispheric westerlies have intensified,
which leads to greater equatorward Ekman
transport. The Northern Hemisphere warms slightly
while the Southern Hemisphere cools, indicating a
weak seesaw effect. The reduction in atmospheric
CO2 (not shown) is relatively small (about -6
ppmv).