Response of Subglacial Drainage Network in Western Greenland to Changing Boundary Conditions Revealed by X-band SAR Data
Nagler, Thomas¹; Scharrer, Kilian¹; Hetzenecker, Markus¹; Floricioiu, Dana²; Rott, Helmut^1
1ENVEO IT GmbH, AUSTRIA; ²DLR / IMF, GERMANY

About 50% of the current mass loss of the Greenland ice sheet (GrIS) is attributed to meltwater runoff from the land-terminating parts of the ice sheet. However, the impact of increasing summer melt on the dynamics and stability of the GrIS is not fully understood. Therefore, sub-seasonal information about the icesheets’ dynamics and the cyclic evolution and capacity of the subglacial drainage system is crucial, as it links ice sheet acceleration, melting, and supraglacial lake drainage. We use a time series of 14 ascending and descending X-band stripmap scenes acquired by TerraSAR-X and TanDEM-X over Russell glacier in West Greenland covering the melt period in 2011 to study sub-seasonal changes of surface elevation and ice dynamics. We apply a novel approach utilising incoherent offset tracking on SAR amplitude images of crossing ascending and descending orbits. In contrast to the conventional technique, this method delivers the three components of the displacement vector (x, y, and z).
We will report on the time series of velocity and surface elevation change. We find a gradual slow-down of the ice in the course of the summer, indicating the development of an effective subglacial drainage system. However, the entire area speeds up again in late summer which is due to intensive rainfall. During this event, large areas of the icesheet show high uplift rates indicating the accumulation of water beneath the ice. Furthermore, the spatial pattern of surface elevation changes reveals the seasonal development of a subglacial drainage system in the area which seems to be governed by channel flow.