Sack Lunch Seminar (SLS)

Here we suggest a new "teleconnection" mechanism by which the Southern Ocean can induce anomalies in the tropical oceans and atmosphere. A 5000 year long control simulation in a coupled atmosphere-ocean model (CM2Mc, a low-resolution GFDL model), shows a natural, highly regular decadal oscillation between periods of Southern Ocean (SO) open sea convection and non-convective periods. We have recently found this process to happen naturally, with different frequencies and durations of convection across the majority of CMIP5 under preindustrial forcing (deLavergne et al, 2014).

In our model, oscillations in Weddell Sea convection drive multidecadal variability in SO and global SSTs, as well as SO heat storage, with convective decades relatively warm due to the heat released from the Circumpolar Deep Water and non-convective decades cold due to subsurface heat storage. Pulses of Weddell Sea convection drive local SST and sea ice variations, influencing absorbed shortwave and emitted longwave radiation, winds, cloud and precipitation patterns.

Furthermore, SST changes south of 60S immediately trigger changes in the Ferrell and Hadley atmospheric cells, atmospheric energy budget, global hydrological cycle and cross-equatorial heat exchange, ultimately influencing - via fast atmospheric teleconnections - the position of the Intertropical Convergence Zone and rain patterns in the tropics. Finally, we show that the SO convection pulses can also be propagated to the tropics via oceanic pathways on relatively fast (decadal) timescales. We advocate the collection of both paleo and modern proxies that can verify these model-derived Southern Ocean - tropical teleconnection mechanisms.