- Related Research Areas
- Earth Surface & Interior
East Antarctica’s “megadunes” cover 1,250,000 km2 in the low accumulation plateau area and have unique visible, radar, and altimeter remote sensing characteristics that are related to their sinuous form and persistent winds across the regional topography. Analysis of ICESat-1 and other remote sensing data indicates these dunes are up to 10 m in height, typically have wavelengths of 3-5 km and lengths up to 100 km. Study of one large area where megadunes lie obliquely across the regional slope shows that the dune orientation/motion is at an angle to the GPS-derived flow vector (~E at ~4 m/yr). Because these features are sustained by differential accumulation - ranging from ~10 cm/yr increases in elevation on their windward faces due to local accumulation to sinking from firn compaction and vertical ice flow due to near zero accumulation/ablation on their lee faces in East Antarctica’s typical wind field - we believe that analysis of fully-saturation- corrected ICESat-1 data can confirm estimates of active dune migration derived from field observations. We will utilize two types of ICESat-to-ICESat elevation differences once correction of residual saturation errors has been addressed: 1) from crossovers (intersections of ascending and descending altimeter passes with known interpolation geometries between footprints) and 2) from exact repeat tracks (ascending to ascending or descending to descending profiles with small spatial footprint offsets). By statistically accumulating “windward face”, “dune crest”, and “lee face” elevation differences across a substantial portion of these megadune features, we can confirm the model-based estimates of active dune migration due to differential accumulation. Because these elevation change differences between fore (upwind) and back (downwind) slopes are expected to be at the decimeter level, these features present an effective test of the limit of change detection from ICESat-1 across much of the interior of Antarctica. In addition, because of the their near-zero accumulation, the lee faces of the megadunes are subjected to extreme metamorphism and have distinctly different radar signatures from the accumulating windward dune faces. Changes in microwave scattering seen in SAR imagery will also lead to differential penetration for the CryoSat-2 radar altimeter’s footprint. Utilizing corrected ICESat-1 data, we see these areas as critical places to investigate penetration effects for CryoSat-2. These effects, when aggregated over the whole of the low accumulation plateau of East Antarctica, could lead to unanticipated mass balance uncertainty. But by using fully-corrected ICESat-1 elevation data and spatial patterns of backscatter variation from SAR to assess CryoSat-2 differential penetration, we will make progress on understanding this effect and its impact on mass balance data. In support of our work with ICESat data, we will also populate a publicly-available database with these data. We have used a version of this database for prior ICESat work at UNH, to support web-based geographic queries. This will provide a more flexible interface to the data than the evolving data releases on the restricted access, but more complete, database available to Shuman at NASA/GSFC. We are proposing to document and extend the database access to ICESat data at UNH to improve access to these data by the research community at large. Our work to date allows two laser operations periods over Greenland to be viewed against high resolution imagery in a selection of browsers; we have demonstrated the capability to handle the global data set as well, using open-source tools that can be migrated to an archive as they prove useful. The goal is refined data access; as a side effect the data become easier to browse. A simple (and unrefined) global browse for Google Earth is here (zoom in to see shots and ellipsoidal elevations): http://planet.sr.unh.edu/GLAS/glas06.kml
Project PI : Christopher Shuman/UMBC/GEST @ NASA/Goddard Space Flight Center
Solar System Divisions Building 33, Room A210 NASA GSFC, Code 698.0 Greenbelt, MD 20771 USA
Phone: (301) 614-5706
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