Circulation response to aerosol forcing of the 1970s and 2000s - the
case of the North Atlantic warming hole
Abstract
We show how changes in the global distribution of anthropogenic aerosols
favour different spatial patterns in the North Atlantic sea-surface
temperature (NASST). The NASSTs largely show the expected decrease
associated with the anthropogenic aerosols in the 1970s, but also a
surprising warming response in the eastern sub-polar gyre, the region of
the North Atlantic warming hole. The NASST response reversed for the
anthropogenic aerosols in the 2000s against 1970s. The regional
reduction in anthropogenic aerosols favoured (1) a strengthening of the
warming hole and (2) a NASST increase at high latitudes associated with
changes in the atmosphere-ocean dynamics. The gyre component of the
northward Atlantic heat transport in mid- to high latitudes is an
important driving mechanism. At least two-thirds of the NASST response
is associated with the magnitude of aerosol-cloud interactions.
Constraining the NASST response therefore depends on a better
understanding of the uncertain aerosol effects on clouds.