12.11.2012: FB2-Seminar

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

Abstract:

Mesoscale ocean eddies are ubiquitous features in the global ocean, yet theirrole in the Earth system is not thoroughly understood. Here, we explore a fewaspects 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 ofabout 10% north of the Antarctic Circumpolar Current (ACC), and vice versain the vicinity of the ACC. We attribute this imprint on CHL largely to eddytrapping and pumping and, to a lesser extent, to simple lateral stirring. The netimpact of eddies on the surface CHL distribution is small, though, as the effectsof AE and CE mostly cancel. Secondly, the anomalous sea surface temperaturesof ocean eddies (several 1/10 ◦ C) and resulting intensified air-sea fluxes lead toa local mean increase (decrease) of winds, clouds and precipitation of severalpercent related to warm (cold) core AE (CE).