The dominant contribution of Southern Ocean heat uptake to time-evolving
radiative feedback in CESM
Abstract
Radiative feedbacks are found to vary with time in both historical
records and future warming projections. Previous studies proposed two
factors that determine the variation of radiative feedbacks: (i) the
evolution of tropical sea surface warming patterns and (ii) the
tropical-extratropical contrast of ocean heat uptake. Our results bridge
the two factors by evaluating the remote impact from the extratropical
ocean on tropical temperature patterns, accounting for the changes in
radiative feedbacks. Based on the Green’s Function approach that
quantifies the non-local contributions of regional ocean heat uptake, we
show that the net radiative feedback evolution in CESM can be mostly
attributed to the heat uptake variations in the Southern Ocean. The
enhanced surface warming associated with the weakened heat uptake
decades after quadrupling CO2 is not confined over the
Southern Ocean, but extends to tropical Southeastern Pacific, which
leads to decreasing tropospheric stability and more positive cloud
feedbacks.