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SYKW: Symposium Klimawandel: Gibt es eine Erwärmungspause?

SYKW 1: Symposium - Klimawandel, gibt es eine Erwärmungspause ?

SYKW 1.4: Hauptvortrag

Dienstag, 18. März 2014, 18:00–18:30, Audimax

Internal Southern Ocean Centennial Variability: Implications for Global Warming — •Mojib Latif — GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel

Some of the recent decadal trends observed in the Southern Hemisphere including the lack of a strong Southern Ocean surface warming may have originated from longer-term internal centennial variability. This is supported by the instrumental sea surface temperatures, a multi-millennial reconstruction of Tasmanian summer temperatures from tree rings, and a millennial control integration of the Kiel Climate Model (KCM). In the model, the centennial timescale originates from the slow accumulation of heat in the Weddell Sea at mid-depth. During phases of Weddell Sea deep convection, vast amounts of heat are released to the atmosphere, which drives global teleconnections. After the deep convection halts, the heat accumulation at mid-depth resumes, and this phase is accompanied by expanding Antarctic sea ice cover and Southern Ocean Sector surface cooling, similar to what was observed during the recent decades. This suggests that internal centennial variability should be considered in addition to external forcing when discussing the climate of the 20th century and that of the 21st century. In the KCM, the centennial variability is associated with global average surface air temperature changes of the order of a few tenths of a degree per century, suggesting a contribution to the current hiatus in global warming through an enhanced deep ocean heat uptake.