Millennial modulation of Atlantic Multi decadal Variability

Seminar by Prof. Joakim Kjellsson from GEOMAR Helmholtz Centre for Ocean Research Kiel

20 November 2023
KST 10:30 – 11:30

The Seminar is being held in Room 1010 (Jasmin) – Integrated mechanical engineering building. Click here for the campus map.

The Atlantic Multi-decadal Variability (AMV) is a prominent mode of sea-surface temperature (SST) variability over the North Atlantic and can impact European weather and climate, such as droughts and Atlantic hurricane activity. We study the AMV and its key processes in a 2000-year-long control simulation from a climate model and find that the AMV behaviour is modulated by a mode of millennial vari- ability characterized by warm and cold periods. In the warm period, the AMV is preceded by a strong Atlantic meridional overturning cir- culation (AMOC) and the surface warming is accompanied by warming of the subsurface, implying that the AMV is driven by anomalies in ocean circulation and poleward heat and salt transport. Conversely, in the cold period, the AMV is preceded by downward air-sea heat flux in the subpolar North Atlantic, the warming is only found near the surface, and AMOC anomalies peak after the AMV, implying that the AMV is driven by heat flux from the atmosphere. This indicates that the phase of a millennial-scale mode of ocean variability modulates the main mechanisms of the AMV as well as the AMV-AMOC relationship.