24.01.2022: Ocean Circulation and Climate Dynamics Colloquium

When?     Monday, 24. January 2022 at  5 pm
Where?    ZOOM meeting room: https://geomar-de.zoom.us/j/86381635858?pwd=VVF1Q1JsVS9BOS85ZDBWTHJ6bmphQT09

Meeting-ID: 863 8163 5858

Kenncode: 523532

The prevailing easterly winds bring up cold waters from the thermocline on the equator. The thermocline water that upwells on the equator originates from the winter subtropical gyre, riding on a shallow meridional overturning circulation (MOC). Equatorial wave adjustments to the variable trade winds allow positive feedback from the mutual interaction and cause the Pacific to oscillate between El Nino and La Nina.
Global-mean surface temperature has risen by more than 1^oC in response to anthropogenic increase of atmospheric greenhouse gases. How does the ocean circulation change, by what mechanisms, and how does it affect the atmospheric circulation and regional climate change? This lecture explores these questions brought to the fore by climate change. Major changes in the ocean circulation are expected. In the midlatitudes, while the wind change is weak and uncertain, models project robust changes in the subtropical ocean gyre—which intensifies in the upper layer and weakens in the lower thermocline due to increased density stratification.
Ocean uptake of anthropogenic heat and storage below the mixed layer slow the surface warming. The ocean heat uptake is so far concentrated in the Southern Ocean, an interhemispheric asymmetry that seems due to the cooling effect of anthropogenic aerosols. With the reduction of aerosols to curb air pollution, the subpolar North Atlantic is expected to emerge as a major heat sink as the deep Atlantic MOC slows down. The subpolar ocean heat uptake has important effects on the atmospheric circulation and regional climate change. Oceanographers led the development of coupled ocean-atmosphere theory of El Nino and the Southern Oscillation, leading to operational seasonal forecast. Ongoing global warming opens new frontiers for dynamic oceanography to uncover how ocean changes affect climate, marine geochemistry, and biology.

 

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