December 18, 2023: Ocean Circulation and Climate Dynamics Colloquium

Hybrid Colloquium

When?  Monday, December 18, 2023 at 11 am
Where?    Lecture Hall, Building 8A, Wischhofstr. 1-3 and via Zoom: https://geomar-de.zoom.us/j/84289388604?pwd=dGlpeTBUd1Nxem5Ec3dRYXh4NFpOUT09

Abstract:

In the equatorial upwelling system of the Atlantic Ocean, temperature, salinity, sea surface height, and ocean velocity variations on time scales of tens of days are dominated by the presence and propagation of mesoscale Tropical Instability Waves (TIWs). Lateral advection and vertical mixing due to TIWs have a considerable impact on the mixed layer heat budget in the equatorial cold tongue region, and have been shown to influence variability of biogeochemical parameters such as chlorophyll, oxygen, carbon, and nutrients. This presentation gives an overview of two recent studies focusing on long-term changes in Atlantic TIW activity and the impact of interannual climate modes. Multi-parameter analyses of in-situ measurements and satellite observations provide evidence for a multidecadal intensification of TIW activity in the Atlantic Ocean. Long-term trends are significant, but convolved with strong interannual variability due to the impact of Atlantic Niño and Niña events. Our results show that the extreme 2021 Atlantic Niño was strong enough to cause the weakest TIW season in decades, based on temperature, salinity, sea surface height, and current velocity data. Despite extremely weak TIW velocities, unexpectedly normal levels of surface chlorophyll intraseasonal variability were observed during the 2021 Atlantic Niño. Possible explanations will be discussed.

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