The Recovery Ice Stream with its large catchment basin plays an important role in discharging ice from East Antarctica into the Weddell Sea through the Filchner Ice Shelf. Its scientific interest is also linked to the discovery that the ice flow is influenced by the discharge of several subglacial lakes, which could trigger a faster flow due to reduced friction on the glacier bed. We analyzed surface elevations of the Recovery Glacier system in Antarctica derived from time series of TanDEM-X data with focus on location of subglacial lakes. The absolute calibration of the TanDEM-X DEMs was performed using airborne laser altimetry datasets from NASA's Operation Icebridge ATM and AWI's Polar 6. In addition the grounding line position for the neighbouring Slessor, Bailey and Recovery glaciers was estimated through DInSAR with TerraSAR-X data acquired in 2014 and 2015.

Determining the frontal position of a calving glacier at different moments of time is a prerequisite for the estimation of the calving rate and flux. Therefore, we developed an automatic detection algorithm of glacier fronts which should be applied to large time series of SAR data and replace the manually mapping. The methodology is based on the analysis of the SAR backscattering amplitude value distribution along defined longitudinal profiles which cover the glacier terminus and traverse the transition zone between the glacier ice and the water at its front. The technique reduces the 2D amplitude image to 1D amplitude profiles and is therefore called profile method.

We performed three field campaigns in 2004, 2007, and 2010 at the southern margin of the Jakobshavn Isbræ, West Greenland, in order to infer flow velocities and their changes from photogrammetric time‐lapse imagery with a temporal resolution of 20 min and a spatial spacing of about 30 m on the glacier surface. Area‐wide analysis of more than 3000 three‐dimensional trajectories at individual glacier positions allow for both the mapping of the grounding line and the detailed observation of flow variations during major calving events. From 2004 to 2010, the grounding line of Jakobshavn Isbræ retreated 3.5 ± 0.2 km. Considering previously published results, the grounding line retreat amounts to 6 km since 1985. The glacier has an ephemeral floating tongue that can establish during the readvance of the glacier front and break apart after large calving events. Observations of a major calving event show that an acceleration of flow velocities coincides with the onset of the break up during which flow velocities of up to 70 m/d can be reached. Moreover, large vertical displacements of the glacier front in the order of 15 m and lowering of 8 m at positions 500 m beyond the calving front were observed 2 days before the calving event. After the break up, the glacier slowly adjusts to the new boundary conditions within the next 4–5 days. Flow velocity variations caused by calving were detected up to 1 km upstream only which indicates that individual calving events have no immediate effect on the large‐scale glacier dynamics.

We derived flow velocity fields over the last decade for all outlet glaciers with a frontal width larger than 1 km along the Greenland coast using a feature tracking approach in Landsat imagery. The velocity fields were used to determine both the linear trend and the seasonal variation of the flow regime. Additionally, we map the advance or retreat of the frontal position for individual glaciers. In this paper we focused on two regions in West Greenland (Jakobshavn Isbræ) and Southeast Greenland (Køge Bugt). For the Jakobshavn Isbræ the frontal glacier area accelerated from 15 m/day in 1999 to over 30 m/day in 2011 and thereby retreated over 12 km. In the Køge Bugt region, some glaciers show a similar acceleration in flow velocity while some do not vary in flow velocity significantly.

We discuss TerraSAR-X observations of three Transantarctic Mountain (TAM) outlet glaciers: Byrd, Nimrod and Beardmore. High resolution TerraSAR-X data acquired over the area in late 2009 and late 2010 using left looking mode were processed to generate detailed 2D ice velocity maps by means of speckle tracking. The ice dynamics from East Antarctica to Ross Ice Shelf through the three TAM fjords is compared. The position of the grounding line is determined by DInSAR and compared to other sources. The surface velocity at the grounding line is needed for estimating the magnitude of ice flux from East Antarctica fast glaciers into the Ross Ice Shelf.

The knowledge of accurate surface topography heights and ice dynamics is a key issue for mass flux and mass balance calculations. In this study we use interferometry to derive surface heights and horizontal ice flow velocities for grounded parts in Western Dronning Maud Land, Antarctica. Additionally, a feature and speckle tracking is performed to also estimate horizontal ice flow velocities for the Riiser-Larsen ice shelf and its grounding zone. This flow velocity field is afterwards used to remove the horizontal flow velocity component from the interferograms in order to obtain the vertical changes in the ice shelf area which are caused by ocean tides. The measured height changes are than compared to the predicted height changes of current ocean tide models which allow a validation of the models quality.

During the summer of 2004, the front area of the Jakobshavn Isbræ was monitored using a geodetic‐photogrammetric survey with temporarily coincident precise observations of local ocean tides in the Disko Bay close to Ilulissat. The geodetic and photogrammetric observations were conducted at the southern margin of the glacier front. The largest observed horizontal flow velocities are in the central part of the front with values up to 45 m/d. This is a factor of 2 greater than the average velocities at the front area observed in the last century. Our new observations confirm previous estimates of an acceleration of glacier flow during the last decade. The photogrammetric survey provided flow trajectories for 4000 surface points with a time resolution of 30 min. These flow trajectories were used to compare the vertical motion of the glacier with the observed tides. The existence of a free‐floating glacier tongue in 2004 was confirmed by these data. However, it occupied only a small belt, of at most a few 100 m width, in the central part of the glacier front. Horizontal motion did not appear to depend on the tidal phase, unlike some of the fast‐moving ice streams of West Antarctica.

Extensive observations on Nivlisen, an ice shelf on Antarctica's Atlantic coast, are analyzed and combined to obtain a new description of its complex glaciological regime. We generate models of ice thickness (primarily from ground-penetrating radar), ellipsoidal ice surface height (primarily from ERS-1 satellite altimetry), freeboard height (by utilizing precise sea surface information) and ice-flow velocity (from ERS-1/-2 SAR interferometry and GPS measurements). Accuracy assessments are included. Exploiting the hydrostatic equilibrium relation, we infer the 'apparent air layer thickness' as a useful measure for a glacier's density deviation from a pure ice body. This parameter exhibits a distinct spatial variation (ranging from approximate to 2 to approximate to 16 m) which we attribute to the transition from an ablation area to an accumulation area. We compute mass-flux and mass-balance parameters on a local and areally integrated scale. The combined effect of bottom mass balance and temporal change averaged over an essential part of Nivlisen is -654 +/- 170 kg m(-2) a(-1), which suggests bottom melting processes dominate. We discuss our results in view of temporal ice-mass changes (including remarks on historical observations), basal processes, near-surface processes and ice-flow dynamical features. The question of temporal changes remains open from the data at hand, and we recommend further observations and analyses for its solution.

A more accurate assessment of the contemporary evolution of the Greenland ice sheet and its major drainage basins requires a close interaction between observational data and modeling. The main challenge when interpreting satellite and observational data is to separate the ice mass contribution from the contribution of postglacial isostatic rebound, to separate ice-sheet dynamic changes from interannual surface mass balance changes, and to separate long-term ice-dynamic changes from short-term flow fluctuations. Here we report from recent progress towards these goals within the DFG SPP 1257 project 'Assessing the current evolution of the Greenland ice sheet' from studies combining observational data with glaciological modeling. This comprises studies to reconstruct the surface mass balance of the Greenland ice sheet between 1866 and 2006, optical satellite data from ASTER to obtain surface velocities, modelled balance velocities, and simulations with a three-dimensional thermomechanical ice-sheet model. In combination with GRACE data, these studies are expected to contribute to an improved estimate of the present-day contribution of the Greenland ice sheet to global sea-level change and a better understanding of the various contributions to current ice mass changes and their associated uncertainties.