Abstract
AbstractThe accuracy of sea-ice motion products provided by the National Snow and Ice Data Center (NSIDC) and the Ocean and Sea Ice Satellite Application Facility (OSI-SAF) was validated with data collected by ice drifters that were deployed in the western Arctic Ocean in 2014 and 2016. Data from both NSIDC and OSI-SAF products exhibited statistically significant (p< 0.001) correlation with drifter data. The OSI-SAF product tended to overestimate ice speed, while underestimation was demonstrated for the NSIDC product, especially for the melt season and the marginal ice zone. Monthly Lagrangian trajectories of ice floes were reconstructed using the products. Larger spatial variability in the deviation between NSIDC and drifter trajectories was observed than that of OSI-SAF, and seasonal variability in the deviation for NSIDC was observed. Furthermore, trajectories reconstructed using the NSIDC product were sensitive to variations in sea-ice concentration. The feasibility of using remote-sensing products to characterize sea-ice deformation was assessed by evaluating the distance between two arbitrary positions as estimated by the products. Compared with the OSI-SAF product, relative errors are lower (<11.6%), and spatial-temporal resolutions are higher in the NSIDC product, which makes it more suitable for estimating sea-ice deformation.
Highlights
Satellite sensors provide images at various resolutions from which sea-ice motion can be retrieved
To compare sea-ice drift speeds derived from sea-ice motion products with those from drifters, drifter data were downsampled to 1 d to be consistent with National Snow and Ice Data Center (NSIDC) and 2 d for Ocean and Sea Ice Satellite Application Facility (OSI-SAF)
Correlation coefficient (R) for NSIDC through the whole ice season in 2014/15 was 0.88, which is statistically significant at the 99.9% level ( p < 0.001); root mean square error (RMSE) was 0.029 m s−1
Summary
Satellite sensors provide images at various resolutions from which sea-ice motion can be retrieved. Using in situ measurements from acoustic Doppler current profilers, Rozman and others validated sea-ice motion products obtained over the Laptev Sea (Rozman and others, 2011); with a correlation coefficient (R) of 0.86 between the CERSAT product and in situ measurements, which is higher than the correlation between the OSI-SAF product and in situ measurements (R = 0.63). Hwang (2013) compared position data from six different satellite ice motion products with measurements by ice-tethered profilers; with a mean deviation of drift speed of 0.22 ± 2.47 km d−1, errors in the OSI-SAF product are lower than those in the CERSAT product. Because of the limited spatial coverage of buoy data for one given year, seasonal and regional variations in the accuracy of sea-ice motion products remain unknown. When sea-ice motion products are assimilated into numerical models, it is essential to understand variations of the accuracy of the products to quantify errors in model output (Rollenhagen and others, 2009)
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