Control by the Circulation Transport Outside the Arctic on Transient
Response of AMOC to Global Warming
Abstract
Using the Alfred Wegener Institute Climate Model (AWI-CM 1.1 LR), we
conduct sensitivity experiments separating the Arctic and extra-Arctic
warming to investigate the transient response of AMOC to quadrupled
carbon dioxide (4×CO2) forcings. The results suggest that AMOC weakening
is primarily affected by circulation adjustment induced by the
outer-Arctic warming, while the effects of Arctic warming are confined
to the polar range and contribute less to AMOC changes. When warming
forcing is applied outside the Arctic, the increases of northward
advective heat transport dominate the weakening of deep convection in
the Nordic Seas, while the reduction of heat loss from ocean to
atmosphere is prevalent in Labrador Sea. Besides, the weakening of deep
convection in Nordic Seas is more pronounced than in Labrador Sea,
implying a leading role of Nordic Seas in the weakening of AMOC under
global warming.