Tropical forcing of Circumpolar Deep Water Inflow and outlet
glacier thinning in the Amundsen Sea Embayment, West Antarctica
Outlet glaciers draining the Antarctic ice sheet into the Amundsen Sea Embayment (ASE)
have accelerated in recent decades, most likely as a result of increased melting of their ice-shelf termini
by warm Circumpolar Deep Water (CDW). An ocean model forced with climate reanalysis data shows
that, beginning in the early 1990s, an increase in westerly wind stress near the continental shelf edge
drove an increase in CDWinflow onto the shelf. The change in local wind stress occurred predominantly
in fall and early winter, associated with anomalous high sea-level pressure (SLP) to the north of the ASE
and an increase in sea surface temperature (SST) in the central tropical Pacific. The SLP change is
associated with geopotential height anomalies in the middle and upper troposphere, characteristic of a
stationary Rossby wave response to tropical SST forcing, rather than with changes in the zonally
symmetric circulation. Tropical Pacific warming similar to that of the 1990s occurred in the 1940s, and
thus is a candidate for initiating the current period of ASE glacier retreat.
Authors: Steig, E.J., Ding, Q., Battisti, D.S., Jenkins, A.