Abstract
Abstract. We assess different methods and input parameters, namely snow depth, snow density and ice density, used in freeboard-to-thickness conversion of Arctic sea ice. This conversion is an important part of sea ice thickness retrieval from spaceborne altimetry. A data base is created comprising sea ice freeboard derived from satellite radar altimetry between 1993 and 2012 and co-locate observations of total (sea ice + snow) and sea ice freeboard from the Operation Ice Bridge (OIB) and CryoSat Validation Experiment (CryoVEx) airborne campaigns, of sea ice draft from moored and submarine upward looking sonar (ULS), and of snow depth from OIB campaigns, Advanced Microwave Scanning Radiometer (AMSR-E) and the Warren climatology (Warren et al., 1999). We compare the different data sets in spatiotemporal scales where satellite radar altimetry yields meaningful results. An inter-comparison of the snow depth data sets emphasizes the limited usefulness of Warren climatology snow depth for freeboard-to-thickness conversion under current Arctic Ocean conditions reported in other studies. We test different freeboard-to-thickness and freeboard-to-draft conversion approaches. The mean observed ULS sea ice draft agrees with the mean sea ice draft derived from radar altimetry within the uncertainty bounds of the data sets involved. However, none of the approaches are able to reproduce the seasonal cycle in sea ice draft observed by moored ULS. A sensitivity analysis of the freeboard-to-thickness conversion suggests that sea ice density is as important as snow depth.
Highlights
As part of the European Space Agency (ESA) Climate Change Initiative (CCI) Sea Ice Essential Climate Variable (ECV) project (SICCI project), quality-controlled long-term data sets of sea ice thickness and concentration will be derived from Earth observation data
In the following we present the results of comparing the various data sets
We report on the results of an investigation of the sensitivity of satellite radar altimeter (RA) freeboard-to-thickness conversion to input parameters and assumptions carried out within the European Space Agency Climate Change Initiative Sea Ice Essential Climate Variable project using Environmental Satellite (Envisat) radar altimetry (RA-2)
Summary
As part of the European Space Agency (ESA) Climate Change Initiative (CCI) Sea Ice Essential Climate Variable (ECV) project (SICCI project), quality-controlled long-term data sets of sea ice thickness and concentration will be derived from Earth observation data. The main data source for hemispheric sea ice thickness distribution is satellite radar altimetry. Laxon et al (2003) used European Remote Sensing Satellites (ERS1/2) radar altimeter (RA) data to obtain a first estimate of the sea ice thickness distribution in the Arctic Ocean south of 81.5◦ N. S. Kern et al.: About uncertainties in sea ice thickness retrieval from satellite radar altimetry up to 88◦ N. In a number of studies, the retrieved sea ice freeboard and its derived thickness product were evaluated To be calculated and evaluated is the sea ice thickness using the combined time series of ERS-1/2 RA data and Environmental Satellite (Envisat) radar altimeter-2 (RA-2) data of the period 1993 to 2012
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have