Dual-Pol X-Band Pol-InSAR Time Series of a Greenland Outlet Glacier

Abstract

The Helheim glacier in south-east Greenland faces a retreat and thinning like many other Greenland outlet glaciers, but showed two particular huge and fast retreats between 2000 and 2005, coinciding with an acceleration of glacier flow [1]. The estimation of glacier retreat and thinning are established procedures based on a variety of remote sensing techniques, e.g. SAR interferometry (InSAR) [1]. However, due to densification processes, e.g. refreezing of meltwater, changes in the mass balance cannot be calculated solely from changes in the volume of a glacier derived from interferometric elevation models [2]. A near surface densification related to refreezing of meltwater leads to a reduction in surface elevation, but does not contribute to a mass loss and thus cannot be attributed to a potential sea level rise. Likewise, the measurement of snow accumulation and its spatial distribution is error prone due to the penetration bias of InSAR measurements. While local data of accumulation or densification give precise information [2], satellite based polarimetric and interferometric SAR (Pol-InSAR) data has the potential to assess these changes in the near surface snow and firn layers with a better spatial and temporal coverage. This study investigates X-band (TanDEM-X) Pol-InSAR data in order to retrieve information about the temporal and spatial variations of surface and near- surface parameters of the Helheim glacier. [1] I.M. Howat, I. Joughin, S. Tulaczyk, and S. Gogineni, “Rapid retreat and acceleration of Helheim Glacier, east Greenland”, Geophysical Research Letters, vol. 32, 2005 [2] V. Parry, P. Nienow, D. Mair, J. Scott, B. Hubbard, K. Steffen and D. Wingham, “Investigations of meltwater refreezing and density variations in the snowpack and firn within the percolation zone of the Greenland ice sheet”, Annals of Glaciology, vol 46, no. A252, pp. 61-68, 2007