Joint Seminar: On the Impact of Southern Ocean Eddies on the Lower Atmosphere and Biology

Mesoscale ocean eddies are ubiquitous features in the global ocean, however their role in the Earth system is not yet thoroughly understood. We explore a few aspects of it based on satellite observations of the Southern Ocean, an area of intense eddy activity. To this end, we identify and track individual eddies as well as the associated 'atmospheric state' (wind/clouds/precipitation) and chlorophyll-a (CHL). The large number of detected eddies (>1,000,000) between 1997 and 2010 south of 30°S yields robust results despite frequent missing values and a high background variability.

Firstly, 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 O(5%) related to warm (cold)  core anticy-clonic (cyclonic) eddies (AE, CE). Secondly, we find an impact of  ocean eddies on CHL, i.e. biology, where AE (CE) feature negative (positive)  CHL anomalies of O(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 degree to mere lateral stirring. The net impact of eddies on the surface CHL distribution is small,  though, as the eff ects of AE and CE mostly cancel.

Date

14.11.2012

Time

13:30 h

Place

Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg

Speaker

Ivy Frenger, Center for Climate Systems Modeling Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich

Organizers

Florian Ziemen

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