Paper published on Arctic sea ice thickness by NIERSC and NERSC

A paper on sea ice thickness retrieval from freeboard data is published in The Cryosphere Discussions 4, 641-661, 2010 with title "The relation between sea ice thickness and freeboard in the Arctic" by Vitaly Alexandrov, Stein Sandven, Johan Wåhlin and Ola M. Johannessen. The paper is available at the link below and is open for interactive discussion.


Retrieval of Arctic sea ice thickness from radar altimeter freeboard data, to be provided by CryoSat-2, requires observational data to verify the relation between the two variables. In this study in situ ice and snow data from about 689 observation sites obtained during the Sever expeditions in the 1980s, are used to establish an empirical relation between ice thickness and freeboard. Furthermore, estimates of mean and variability of snow depth, snow density and ice density are derived from many field observations. The isostatic equilibrium equation is used to estimate ice thickness as function of ice freeboard, snow depth and snow/ice density. The accuracy of the ice thickness retrieval has been calculated from the documented variability in ice and snow parameters and errors in ice freeboard measurements. For FY ice, retrieval of ≈ 1.0 m (2.0m) thickness has an uncertainty of 50% (40%). For MY ice the main uncertainty is ice density error, since the freeboard error is relatively smaller than for FY ice. Retrieval of 2.3 m (3.0 m) thick MY ice has an error of 20 % (18 %). The freeboard error is + 0.05 m for both the FY and MY ice. If the freeboard error can be reduced to 0.01 m, by averaging a large number of measurements from CryoSat, the error in thickness retrieval is reduced to about 32 % for a 1.0 m thick FY floe and to about 16 % for a 2.3 m thick MY floe. The remaining error is dominated by uncertainty in ice density. Provision of improved ice density data is therefore important for retrieval of accurate ice thickness data from CryoSat.