Diminishing Sea-Ice Extent and Thickness in the Arctic Ocean

Abstract

Rapid changes are occurring to Arctic sea ice thickness and extent. We survey the reasons for them, and the methods being used to monitor the changing thickness. Through the late twentieth century Arctic sea ice extent shrank at a relatively modest rate of 3–4% per decade (annually averaged) but after 1996 this speeded up to 10% per decade and in summer 2007 there was a massive collapse of ice extent to a new record minimum of only 4.1 million sq km. Thickness has been falling at a more rapid rate (43% in the 25 years from the early 1970s to late 1990s) with a specially rapid loss of mass from pressure ridges. The summer 2007 event may have arisen from an interaction between the long-term retreat and more rapid thinning rates. We review thickness monitoring techniques which show the greatest promise on different spatial and temporal scales, and for different purposes, and we show results from some recent work from submarines.KeywordsArctic OceanSynthetic Aperture RadarAutonomous Underwater VehicleMultibeam SonarAirborne Laser AltimetryThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.