Abstract
Sea ice concentration (SIC) plays a significant role in climate change research and ship’s navigation in polar regions. Satellite-based SIC products have become increasingly abundant in recent years; however, the uncertainty of these products still exists and needs to be further investigated. To comprehensively evaluate the consistency of the SIC derived from different SIC algorithms in long time series and the whole polar regions, we compared four passive microwave (PM) satellite SIC products with the ERA-Interim sea ice fraction dataset during the period of 2015–2018. The PM SIC products include the SSMIS/ASI, AMSR2/BT, the Chinese FY3B/NT2, and FY3C/NT2. The results show that the remotely sensed SIC products derived from different SIC algorithms are generally in good consistency. The spatial and temporal distribution of discrepancy among satellite SIC products for both Arctic and Antarctic regions are also observed. The most noticeable difference for all the four SIC products mostly occurs in summer and at the marginal ice zone, indicating that large uncertainties exist in satellite SIC products in such period and areas. The SSMIS/ASI and AMSR2/BT show relatively better consistency with ERA-Interim in the Arctic and Antarctic, respectively, but they exhibit opposite bias (dry/wet) relative to the ERA-Interim data. The sea ice extent (SIE) and sea ice area (SIA) derived from PM and ERA-Interim SIC were also compared. It is found that the difference of PM SIE and SIA varies seasonally, which is in line with that of PM SIC, and the discrepancy between PM and ERA-Interim data is larger in Arctic than in Antarctic. We also noticed that different algorithms have different performances in different regions and periods; therefore, the hybrid of multiple algorithms is a promising way to improve the accuracy of SIC retrievals. It is expected that our findings can contribute to improving the satellite SIC algorithms and thus promote the application of these useful products in global climate change studies.
Highlights
Sea ice concentration (SIC) is defined as the percentage of the area occupied by sea ice, which is a common parameter used in climate models [1,2], and it plays a vital role in ship navigation [3,4]
To further investigate the annual discrepancy of each satellite algorithm, we examined the spatial pattern of annual SIC to make a clearer view of the consistency between them, shown in Figure 5 for Arctic and Figure 6 for Antarctic
These comparisons yield a better understanding of remotely sensed SIC products, which is conducive to the improvement of the SIC retrieval algorithms
Summary
Sea ice concentration (SIC) is defined as the percentage of the area occupied by sea ice, which is a common parameter used in climate models [1,2], and it plays a vital role in ship navigation [3,4]. Long-term and large-scale SIC data of polar regions are essential for climate change studies, especially with the recent decline of Arctic sea ice and increase of Antarctic sea ice [5,6,7,8,9]. Passive microwave (PM) remote sensing has been proved to be an effective way to observe sea ice in polar regions both temporally and spatially, mainly due to its high sensitivity to dielectric properties of sea ice and its capability of all-time and all-weather coverage. It is necessary and essential to examine the uncertainties and limitations of various remotely sensed SIC products in polar regions
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