November 12, 2012: FB2-Seminar

13 c.t., Hörsaal WEST, Düsternbrooker Weg 20

Abstract:

Mesoscale ocean eddies are ubiquitous features in the global ocean, yet their
role in the Earth system is not thoroughly understood. Here, we explore a few
aspects of the these eddies and their impacts based on satellite observations of
the Southern Ocean, an area of intense eddy activity. To this end, we identi-
fied and tracked individual eddies, the associated chlorophyll-a (CHL) and the
’atmospheric state’ (winds, clouds and precipitation). The large number of de-
tected eddies (>1,000,000) between 1997 and 2010 south of 30◦ S yields robust
results despite frequent gaps and high background variability.
We find firstly that ocean eddies have an impact on CHL, i.e., biology: anticy-
lonic (cyclonic) eddies, AE (CE), feature negative (positive) CHL anomalies of
about 10% north of the Antarctic Circumpolar Current (ACC), and vice versa
in the vicinity of the ACC. We attribute this imprint on CHL largely to eddy
trapping and pumping and, to a lesser extent, to simple lateral stirring. The net
impact of eddies on the surface CHL distribution is small, though, as the effects
of AE and CE mostly cancel. Secondly, the anomalous sea surface temperatures
of ocean eddies (several 1/10 ◦ C) and resulting intensified air-sea fluxes lead to
a local mean increase (decrease) of winds, clouds and precipitation of several
percent related to warm (cold) core AE (CE).