213
reads

Mojib Latif

2012-09-17
13:50:00 - 14:40:00

101 , Mathematics Research Center Building (ori. New Math. Bldg.)

It is well established that centennial climate variability can be externally forced by e.g. variations of the solar constant or varying atmospheric aerosol concentrations. Climate models suggest that pronounced centennial variability can be also produced internally. However, different mechanisms were proposed. This paper deals primarily with the internal centennial climate variability in the Southern Hemisphere. The latter featured some rather unexpected trends during the recent trends, e. g. a lack of surface warming in contrast to the Northern Hemisphere which did strongly warm. The decadal trends in the Southern Hemisphere are explained as part of a longer-term centennial variability of the Southern Ocean circulation. The long timescale originates from the slow accumulation of North Atlantic Deep Water (NADW) in the Weddell Sea at mid-depth, which destabilizes the water column from below and eventually stimulates deep convection there. The heat accumulation during the non-convective regime and its subsequent release to the atmosphere during the convective regime can be viewed as a non-linear recharge oscillator. The Southern Ocean centennial variability has global climate impacts. In particular, the Atlantic Meridional Overturning Circulation (AMOC) responds with a time delay of several decades to a century to the variations in the Southern Ocean.

For material related to this talk, click here.