Abstract
Satellite remote sensing data including Landsat-8 (optical), Sentinel-1, and RADARSAT-2 (synthetic aperture radar (SAR) missions) have recently become routinely available for large scale ice velocity mapping of ice sheets in Greenland and Antarctica. These datasets are too large in size to be processed and calibrated manually as done in the past. Here, we describe a methodology to process the SAR and optical data in a synergistic fashion and automatically calibrate, mosaic, and integrate these data sets together into seamless, ice-sheet-wide, products. We employ this approach to produce annual mosaics of ice motion in Antarctica and Greenland with all available data acquired on a particular year. We find that the precision of a Landsat-8 pair is lower than that of its SAR counterpart, but due to the large number of Landsat-8 acquisitions, combined with the high persistency of optical surface features in the Landsat-8 data, we obtain accurate velocity products from Landsat that integrate well with the SAR-derived velocity products. The resulting pool of remote sensing products is a significant advance for observing changes in ice dynamics over the entire ice sheets and their contribution to sea level. In preparation for the next generation sensors, we discuss the implications of the results for the upcoming NASA-ISRO SAR mission (NISAR).
Highlights
During the last decade, ice velocity mapping at continental scale [1,2,3] has allowed major advances in the study of polar regions by providing complete and precise observations of the complex flow pattern of ice sheets in the Arctic and Antarctic, from coastal regions to the deep interior
This work initially started from the digital optical images acquired by Landsat [7,8], since about the 1990s synthetic aperture radar (SAR) instruments have been the method of choice to map ice motion at the continental scale [1,2,3,4,12,15,16,17,18,19] because of their ability to work irrespectively of cloud cover and solar illumination, their higher temporal and spatial correlation compared to optical sensors, winter and summer alike, and their finer spatial resolution available at the time
The 2013–2014 mosaic (Figure 2a) is the least complete in the interior because fewer acquisitions were made compared to later years, but it includes a complete coverage of the coastal regions
Summary
Ice velocity mapping at continental scale [1,2,3] has allowed major advances in the study of polar regions by providing complete and precise observations of the complex flow pattern of ice sheets in the Arctic and Antarctic, from coastal regions to the deep interior. This has significantly improved our understanding of the physics of ice flow, the determination of the mass balance of ice sheets, and their contribution to sea level. The Remote Sens. 2017, 9, 364; doi:10.3390/rs9040364 www.mdpi.com/journal/remotesensing
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