Ice flow velocity, elevation change and discharge variation in Novaya Zemlya using SAR and Landsat offset-tracking and radar altimetry
Abstract:Discharge is one of the most important parameters for describing the dynamic status of glaciers. In recent years, observations from satellite sensors and in-situ stations have been combined to provide this critical data. However, over the regions with little or no in-situ data, such as Novaya Zemlya, satellite remote sensing technique becomes the only option. Without the in-situ ice thickness data, the absolute glacier discharge could not be obtained. An alternative way would be to combine the ice velocity and elevation change to estimate the discharge change.
In order to obtain the ice flow velocity, Landsat 7 ETM+ and SAR offset-tracking of eight L-band ALOS PALSAR data are performed for these fast-moving glaciers spanning from 2007 to 2010. Envisat RA-2 radar altimetry data are used to estimate glacier elevation changes from 2002 to 2010 using collinear method (Lee et al., RSE, 2013) over eight different locations. All of the altimetry time series reveal decreasing elevation changes until year 2007, and then increasing elevation changes. This change in trends also agrees with the mass change time series obtained from GRACE. Snow depth and temperature anomalies from ERA-interim are also examined to explain change in mass variation rates. However, since all of the Envisat altimetry stations are located upstream of the glaciers, we attempt to extrapolate Envisat-derived elevation changes along the glacier streams with an aid of ICESat altimetry that passes exactly along the glacier stream. Estimated discharge changes along the glacier stream will be compared with an existing approach using ice thickness derived from ice flow velocity.