Ice characteristics and processes, and remote sensing of frozen rivers and lakes

This chapter is a broad overview of ice characteristics and processes on northern rivers and lakes in the time between initial ice formation in autumn and final melt-out in spring. Using primarily synthetic aperture radar (SAR: ERS-1, ERS-2, JERS-1, RADARSAT-1) images supplemented by aerial photographs, passive microwave and Landsat images, and examples from the literature, the aim is to illustrate the potential for remote sensing to contribute to a better knowledge and understanding of river ice and lake ice in the context of their role in northern hydrology and their value as sensitive indicators of northern environmental variability and change. The following seasonal ice characteristics and processes are described: (1) autumn freeze-up; (2) growth, thickening, and grounding; (3) fracturing and motion, including the effect on Mentasta Lake, Alaska, of the magnitude 7.9 earthquake of 3 November 2002; (4) aufeis; and (5) spring break-up. They are followed by a description of perennial ice characteristics, processes, and recent (1997-2002) change on lakes and epishelf lakes in northernmost Ellesmere Island, Nunavut, Canada. The merits of different current and future remote sensing instruments are briefly discussed. We conclude that, as the constellation of increasingly sophisticated spaceborne instruments grows, multisensor remote sensing of frozen rivers and lakes has the potential to contribute more to the study of the role of bodies of water in northern hydrology and of the effects of environmental variability and change on the ice and hydrological system.