School of Earth and Environmental Sciences,
Seoul National University, Seou, Korea
Based on the use of analytically-derived “combined Fresnel equation”, combining two Fresnel equations for polarized reflectivities, we were able to retrieve the ice surface temperature below the snow layer (referred to as snow-ice interface temperature: SIIT), over the Arctic sea ice area. Aimed at retrieving the long-term SIIT information over the Arctic sea ice region, we attempted to retrieve the SIIT from 30-year long SSM/I and SSMIS FCDR (Fundamental Climate Data Record) data. In doing so we developed a linear regression model, relating AMSR-retrieved SIIT to SSM/I frequency channel measurement (here at 19.4 GHz), with a correction factor introduced for removing the influences of surface roughness and volume scatterings on the measured brightness temperature.
By applying the developed algorithm to 30 years of SSM/I and SSMIS 19.4 GHz brightness temperatures over the Arctic sea ice region, winter time (December-January-February) daily SIIT data were produced. Results indicate that there is a rapid warming of sea ice, much faster than surface air temperature; a continuous and dramatic increase of about 3K/decade (> 9K over a 30-year period) over the central Arctic multi-year sea ice area is found over the 30-year period (1987-2017), implying the rapid decrease sea ice depth in particular over the multi-year sea ice area. Prospect of future sea ice melt will be discussed by interpreting such unprecedentedly rapid warming of the Arctic sea ice.