This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
A full understanding of the flow and dynamics of an ice sheet will require knowledge of the state of its subglacial interface. While the topography of the Greenland Ice Sheet bed has been studied by radio echo sounding, its state in terms of melting and freezing, which itself affects its future evolution, has been inferred from numerical models, rather than from direct evidence.
This project is for analysis of existing radar echo data gathered under the PARCA and CReSIS programs, with the objective of generating direct evidence of the extent of subglacial water in Greenland and providing the glaciological community with maps of its extent.
Previous echo analysis has found the variability of the received signal too great to extract the component due to variation of the bed material. Now, a method has been developed, validated and reported, based on further analysis of radio echo signal intensities, which allows the state of the bed to be determined reliably. This work will apply this method to all the available radio echo data, to generate maps of the extent of basal melting throughout Greenland. The procedure relies on a more precise assessment of radio echoes from the bed of the ice sheet than has previously been provided. It allows the variability of echo intensity to be reduced, and the variation of the bed material to be detected. It has been tested with data from a number of flights over Greenland during the 1999 field season, and is validated by tests of self-consistency, of echo intensity statistics, of interface smoothness, and of the relation between measured surface and interface slopes. The team will process data from flights undertaken between 1998 and 2005. Appropriate tests of self-consistency and statistical behavior will be applied.
The presence or absence of water will be determined throughout. Results will be interpreted and maps compiled illustrating these results. The continuity and topographical context of each major water feature will be investigated and compared.
