Seminars

The Southern Ocean contains one of the largest current systems in the
world, the Antarctic Circumpolar Current (ACC). The ACC is the largest
current system in the world, and connects the three major oceans. This
allows an interbasin exchange of heat, salt, carbon, and other chemical and
biological properties. The ACC isolates Antarctica from much of the
poleward heat transport in the ocean, so knowledge of how this transport is
changing in time is vital to understanding future climate change in
Antarctica. As important as the ACC is, however, measurements of how its
transport varies in time has been limited by the difficulty of obtaining in
situ measurements in the extreme environment of the Southern Ocean. The
majority of observations have been made across the Drake Passage, where
the width of the ACC is limited and regular scientific cruises travel between
South America and the Antarctic Peninsula.
In this presentation, I will summarize recent work that I have done with
students and other colleagues on using satellite observations to study the
variability of the ACC in regions away from the Drake Passage. The satellite
measurements include altimetry to measure eddy-kinetic energy and upper
ocean baroclinic transport, gravimetry from the GRACE mission to study
full-depth transport variability, and satellite winds. We have found a
significant increase in eddy-kinetic energy in the Indian and Pacific Oceans
over the last twenty years connected to increasing wind stress. Over the
last decade, we find a deceleration in the ACC transport in the Indian Ocean
and an acceleration west of the Drake Passage which is connected to
regional wind changes. Based on altimetry and in situ full depth
hydrographic measurements, we have found this deceleration has been
occurring since the mid 1990s.