Microwave and thermal infrared emission from young sea ice and pancake ice

Abstract

The goals of this study are to observe the development of multifreqency microwave emissivity (e) of new and young sea ice grown under dynamic conditions, and to investigate the effects of ice growth and structural changes on its microwave signature. In particular, the authors are interested in three ice types, whose signatures are particularly difficult to investigate under normal field conditions. Unconsolidated frazil ice and pancake ice, which occur when ice forms in a wave field under stormy conditions, are found in abundance in the marginal ice zones of the Arctic and Antarctic sea ice packs. They make up a significant portion of the area covered by the new and young ice. Because new and young ice types are weaker than the surrounding thick ice and fracture first under conditions of high ice stress, a large percentage of the ridged ice consists of thin saline ice. As the ridges evolve, brine drains out of the elevated parts causing substantial changes in the permittivity distribution which can affect their microwave emissivities. Previous studies have shown that the microwave signatures of these ice types appear to be distinct in several respects, but the data from these experiments are sparse and the uncertainties are still relatively large. The differences between the microwave signatures of these ice types and those of first-year (FY) ice types grown under relatively calm conditions are important for interpreting satellite derived ice concentrations and ice type distributions. This paper presents the results of the author's latest studies of the microwave emissivities of these ice types.