Antarctic ice-sheet meltwater reduces transient warming and climate
sensitivity through the sea-surface temperature pattern effect
Coupled global climate models (GCMs) generally fail to reproduce the
observed sea-surface temperature (SST) trend pattern since the 1980s.
The model-observation discrepancies may arise in part from the lack of
realistic Antarctic ice-sheet meltwater imbalance in GCMs. Here we
employ two sets of CESM1-CAM5 simulations forced by anomalous Antarctic
meltwater fluxes over 1980–2013 and into the 21st century. Both show a
reduced global warming rate and an SST trend pattern that better
resembles observations. The meltwater drives surface cooling in the
Southern Ocean and the tropical southeast Pacific, in turn increasing
low-cloud cover and driving radiative feedbacks to become more
stabilizing (corresponding to a lower effective climate sensitivity).
These feedback changes contribute more than ocean heat uptake efficiency
changes in reducing the global warming rate. Accurately projecting
historical and future warming thus requires improved representation of
Antarctic meltwater and its impacts in models.