Arctic Sea Ice Surface Temperature from AVHRR

Abstract

The surface temperature of arctic sea ice is estimated using the infrared channels of the Advanced Very High Revolution Radiometer (AVHRR) on satellites NOAA-10 and NOAA-11. Temperature statistics are analyzed for 478 cells measuring 200 km square distributed over the entire Arctic basin throughout 1989. The images are cloud masked manually, and the surface temperature of the cloud-free area is estimated using an algorithm specific to Arctic pack ice. The rms error of the estimate is thought to be about 3.2°C, largely due to uncertainty in cloud masking and the lack of knowledge of hall and ice crystal precipitation occurrence. The mean temperatures of the cells range from near O°C in summer to below ?45°C in winter. Monthly averages range down to ?40°C for the central Arctic and ?29°C for the peripheral seas. The monthly average standard deviation within cells in the central Arctic is highest in November (2.2°C) and drops to almost O°C in the summer. It is commonly twice as large in the peripheral seas as in the central Arctic. A computation of the sensible heat flux at the surface is formulated based on the spatial variations of the surface temperature estimated with AVHRR. The contribution to the heat flux by the thin ice and leads that contribute to the spatial variability is found to be 8 W m?2 larger in the central Arctic than found in earlier estimates.