Articles | Volume 9, issue 1
Research article
10 Feb 2015
Research article |  | 10 Feb 2015

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

R. Lindsay and A. Schweiger

Abstract. Sea ice thickness is a fundamental climate state variable that provides an integrated measure of changes in the high-latitude energy balance. However, observations of mean ice thickness have been sparse in time and space, making the construction of observation-based time series difficult. Moreover, different groups use a variety of methods and processing procedures to measure ice thickness, and each observational source likely has different and poorly characterized measurement and sampling errors. Observational sources used in this study include upward-looking sonars mounted on submarines or moorings, electromagnetic sensors on helicopters or aircraft, and lidar or radar altimeters on airplanes or satellites. Here we use a curve-fitting approach to determine the large-scale spatial and temporal variability of the ice thickness as well as the mean differences between the observation systems, using over 3000 estimates of the ice thickness. The thickness estimates are measured over spatial scales of approximately 50 km or time scales of 1 month, and the primary time period analyzed is 2000–2012 when the modern mix of observations is available. Good agreement is found between five of the systems, within 0.15 m, while systematic differences of up to 0.5 m are found for three others compared to the five. The trend in annual mean ice thickness over the Arctic Basin is −0.58 ± 0.07 m decade−1 over the period 2000–2012. Applying our method to the period 1975–2012 for the central Arctic Basin where we have sufficient data (the SCICEX box), we find that the annual mean ice thickness has decreased from 3.59 m in 1975 to 1.25 m in 2012, a 65% reduction. This is nearly double the 36% decline reported by an earlier study. These results provide additional direct observational evidence of substantial sea ice losses found in model analyses.

Short summary
The sea ice thickness of the Arctic Basin is estimated from sources that include upward-looking sonars, electromagnetic sensors, and lidar or radar altimeters. Good agreement is found between five of the systems while larger systematic differences are found for others. The trend in annual mean ice thickness, 2000--2013, is –0.58–/+0.07m decade–1; for the central Arctic Basin alone the annual mean ice thickness has decreased from 3.45m in 1975 to 1.11m in 2013, a 68% reduction.