Changes in the fabric of the Arctic's greenhouse blanket

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.