Abstract
NASA’s Ice, Cloud and land Elevation Satellite-2 (ICESat-2) mission was launched in September 2018. The sole instrument onboard ICESat-2 is ATLAS, a highly precise laser that now provides routine, very-high-resolution, surface height measurements across the globe, including over the Arctic. To further improve the detection accuracy of the sea ice concentration (SIC), we demonstrate a new processing chain that can be used to convert the along-track sea ice freeboard products (ATL10) obtained by ICESat-2 into the SIC, with our initial efforts being focused on the Arctic. For this conversion, we primarily make use of the classification results from the type (sea ice or lead) and segment length data gathered from ATL10. The along-track SIC is the ratio of the area that is covered by sea ice segments to the area of all of the along-track segments. We generated a monthly gridded SIC product with a 25 km resolution and compared this to the NSIDC Climate Data Record (CDR) sea ice concentration. The highest correlation was determined to be 0.7690 in September at high latitudes and the lowest correlation was found to be 0.8595 in June at mid-latitudes. The regions with large standard deviations in summer and autumn are mainly distributed in the thin-ice areas at mid-latitudes. In the Laptev Sea and Kara Sea of east Siberia, the differences in the standard deviation were large; the maximum bias was −0.1566, in November, and the minimum bias was −0.0216, in June. ICESat-2 shows great potential for the accurate estimation of the SIC.
Highlights
Spatial–temporal changes in sea ice extent are sensitive indicators of climate change.The sea ice concentration (SIC) is an important parameter for the study of sea ice changes.The SIC represents the density of the sea ice in space and refers to the ratios of ice-covered areas to the total unit area
We demonstrate the production of gridded fields to obtain sea ice concentration data, highlight the regional and seasonal variability in these fields and make a comparison with coincident estimates obtained from the National Snow and Ice Data Center (NSIDC)/Climate Data Record (CDR) SIC data (Section 4)
Results and Discussion where σIS−2 and σN represent the standard deviation of the ICESat-2 SIC and NSIDC/CDR
Summary
Spatial–temporal changes in sea ice extent are sensitive indicators of climate change. This study proposes a method that can be implemented to obtain the SIC based on ICESat-2 using the ATL10 sea ice freeboard products and compares and evaluates these new SIC estimates with National Snow and Ice Data Center’s (NSIDC) CDR SIC products. We used the ICESat-2 ATL10 sea ice freeboard products (Release 003), which are available to the public through NSIDC[25]. The ATL10 products provide freeboard estimates within 10 km segments that include at least one sea surface reference. ATL10 products provide freeboard estimates may contain one or more consecutive seaformat surface height (SSHseg). In ATL10, the freeboard is only provided if may contain one or more consecutive sea surface height segments (SSHseg). 150-photon aggregates in an effort to produce the heights, as described in the ATL07 sea ice/seadatasets, surface height product andand. Data were collected on 2 June 2019; along-track surface height profiles from ATL07 (blue line) and data were collected on 2 June 2019; along-track surface height profiles from ATL07 (blue line) and ATL10 freeboard data (red line) for a small (~1 km) profile (location in 83.7 N, 101.9 W)
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