The amount of Arctic sea ice predicted by the Hadley Centre Global Cilimate
Model (GCM) is evaluated using 15 years of passive-microwave data. While the
Hadley model reproduces the seasonal cycle reasonably well, it
underestimates the total area of sea ice by more than 3 × 106
km2 for most of the year. In the winter months, most of the
underestimate in ice area results from the prediction of far too little ice
in Hudson Bay and the Sea of Okhotsk, leading to an excess of up to 0.2 PW
heat input to the atmosphere from Hudson Bay alone. The surface-energy
budget of Hudson Bay is investigated using a mixture of surface observations
(POLES), satellite data (ATSR, SSM/I and ISCCP) and output from the Goddard
Data Assimilation Office analysis. Flux adjustments of the order of 200
Wm−2, resulting from anomalously high sea-surface temperatures
in the Levitus (1982) climatology,
are found to be the cause of the model’s underestimation of sea ice in both
Hudson Bay and the Sea of Okhotsk. The fact that flux adjustments based on
an inaccurate climatology will produce errors, even if the model physics is
correct, underlines the need both for improved climatologies and for models
accurate enough not to require flux adjustment.