Satellite Passive-Microwave Measurements of Sea Ice

Abstract

Sea ice spreads over millions of square kilometers in each polar region at all times and has numerous impacts on the polar atmosphere, oceans, and ecosystems, making it a key variable in the polar climate system. Satellite passive-microwave observations have proven effective for monitoring the sea ice covers due to the strong contrast between the microwave emissions of ice and liquid water and the fact that microwave measurements of the Earth’s surface can be made from satellites during nighttime as well as daytime and under cloudy as well as cloud-free conditions. Satellite passive-microwave measurements of sea ice began in the early 1970s and have been made routinely since the late 1970s, providing a record of the ice cover of each polar region every few days to a spatial resolution of 25–50km or better. These measurements have been used to determine sea ice concentration, extent, type, season length, temperature, melt, and velocity. The record has quantified seasonal, regional, and interannual variabilities and decadal scale trends. It has revealed statistically significant decreases in Arctic sea ice coverage from the late 1970s to the early twenty-first century and much lesser magnitude increases in Antarctic sea ice coverage over the same period.