Arctic sea ice thickness loss determined using subsurface, aircraft, and satellite observations

摘要

Sea ice thickness is a fundamental climate state variable that provides anintegrated measure of changes in the high-latitude energy balance. However,observations of mean ice thickness have been sparse in time and space, makingthe construction of observation-based time series difficult. Moreover,different groups use a variety of methods and processing procedures tomeasure ice thickness, and each observational source likely has different andpoorly characterized measurement and sampling errors. Observational sourcesused in this study include upward-looking sonars mounted on submarines ormoorings, electromagnetic sensors on helicopters or aircraft, and lidar orradar altimeters on airplanes or satellites. Here we use a curve-fittingapproach to determine the large-scale spatial and temporal variability ofthe ice thickness as well as the mean differences between the observationsystems, using over 3000 estimates of the ice thickness. The thicknessestimates are measured over spatial scales of approximately 50 km or timescales of 1 month, and the primary time period analyzed is 2000–2012 whenthe modern mix of observations is available. Good agreement is found betweenfive of the systems, within 0.15 m, while systematic differences of up to0.5 m are found for three others compared to the five. The trend in annualmean ice thickness over the Arctic Basin is ?0.58 ± 0.07 m decade?1over the period 2000–2012. Applying our method to the period1975–2012 for the central Arctic Basin where we have sufficient data (the SCICEXbox), we find that the annual mean ice thickness has decreased from 3.59 min 1975 to 1.25 m in 2012, a 65% reduction. This is nearly double the36% decline reported by an earlier study. These results provideadditional direct observational evidence of substantial sea ice losses foundin model analyses.