Abstract
Models from the Coupled Model Intercomparison Project phase 6 (CMIP6)
typically struggle to reproduce observed Antarctic sea ice trends, a
bias that is substantially alleviated when constraining winds. Here we
use wind-nudged simulations from two CMIP models to investigate the
influence of clouds on sea ice area (SIA). We find that nudging model
winds in coupled simulations towards reanalysis, in addition to
improving SIA variability, is crucial to reproduce realistic cloud
radiative effect (CRE) and cloud cover. We then unveil a negative
relationship between biases in CRE anomalies near the sea ice edge and
SIA anomalies, which helps explain the remaining discrepancies between
simulated and observed SIA: a positive 1 Wm-2 CRE anomaly
bias contributes to a negative 0.43 106 km2 SIA anomaly
bias. Finally, we find that most CMIP6 models (10 of 12) show positive
trends in CRE anomaly biases, which should amplify SIA decline in
response to climate warming.