摘要：The Arctic is rapidly losing its permanent ice. While increases in greenhouse gases are
believed to be the underlying cause of the melting, interactions among the Arctic's
changing thermodynamic and dynamic processes driving ice loss are poorly understood.
The emission of infrared radiation from the atmosphere to the surface has been recently
implicated as an important factor governing the extent of summer perennial sea ice. In this
study we use new satellite-derived products to investigate which atmospheric parameters
are contributing to observed increases in the downwelling flux in longwave radiation (DLF)
during spring in six regions around the periphery of the Arctic Ocean. In areas
dominated by low clouds containing liquid water, we find that DLF trends are driven
primarily by increasing cloud fraction and more abundant water vapor, and offset
by lowering cloud-base heights. In ice-cloud dominated regions (seas north of
Siberia), we find that changing water vapor assumes a more important role, while
effects of changing cloud fraction and cloud-base height are reduced. Results
highlight the need for improved information about Arctic cloud-base heights,
cloud phase, and the height and strength of surface-based temperature inversions.
