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  • 1
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    Spatial and temporal Antarctic Ice Sheet mass trends, glacio-isostatic adjustment, and surface processes from a joint inversion of satellite altimeter, gravity, and GPS data (2016)
    Wiley
    In:  EPIC3Journal of Geophysical Research: Earth Surface, Wiley, 121(2), pp. 182-200, ISSN: 2169-9011
    Details
    Publication Date: 2016-08-15
    Description: We present spatiotemporal mass balance trends for the Antarctic Ice Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic-corrected GPS data for the period 2003–2013. Our method simultaneously determines annual trends in ice dynamics, surface mass balance anomalies, and a time-invariant solution for glacio-isostatic adjustment while remaining largely independent of forward models. We establish that over the period 2003–2013, Antarctica has been losing mass at a rate of −84 ± 22 Gt yr−1, with a sustained negative mean trend of dynamic imbalance of −111 ± 13 Gt yr−1. West Antarctica is the largest contributor with −112 ± 10 Gt yr−1, mainly triggered by high thinning rates of glaciers draining into the Amundsen Sea Embayment. The Antarctic Peninsula has experienced a dramatic increase in mass loss in the last decade, with a mean rate of −28 ± 7 Gt yr−1 and significantly higher values for the most recent years following the destabilization of the Southern Antarctic Peninsula around 2010. The total mass loss is partly compensated by a significant mass gain of 56 ± 18 Gt yr−1 in East Antarctica due to a positive trend of surface mass balance anomalies.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    Calving Induced Speedup of Petermann Glacier (2019)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Earth Surface, Wiley, 124, pp. 216-228, ISSN: 0148-0227
    Details
    Publication Date: 2019-08-14
    Description: This study assesses the response on ice dynamics of Petermann Glacier, a major outlet glacier in northern Greenland, to the 2012 and a possible future calving event. So far Petermann Glacier has been believed to be dynamically stable as another large calving event in 2010 had no significant impact on flow velocity or grounding line retreat. By analyzing a time series of remotely sensed surface velocities, we find an average acceleration of 10% between winter 2011/2012 and winter 2016/2017. This increase in surface velocity is not linear but can be separated into two parts, starting in 2012 and 2016 respectively. By conducting modeling experiments, we show that the first speedup can be directly connected to the 2012 calving event, while the second speedup is not captured. However, on recent remote sensing imagery newly developing fractures are clearly visible ∼12 km upstream from the terminus, propagating from the eastern fjord wall to the center of the ice tongue, indicating a possible future calving event. By including these fracture zones as a new terminus position in the modeling domain, we are able to reproduce the second speedup, suggesting that surface velocities remain on the 2016/2017 level after the anticipated calving event. This indicates that, from a dynamical point of view, the terminus region has already detached from the main ice tongue.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev , info:eu-repo/semantics/article
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  • 3
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    Missing evidence of widespread subglacial lakes at Recovery Glacier, Antarctica (2018)
    Wiley
    In:  EPIC3Journal of Geophysical Research: Earth Surface, Wiley, 123, pp. 2802-2826
    Details
    Publication Date: 2018-12-20
    Description: Recovery Glacier reaches far into the East Antarctic Ice Sheet. Recent projections point out that its dynamic behavior has a considerable impact on future Antarctic ice loss (Golledge et al., 2017, https://doi.org/10.1002/2016GL072422). Subglacial lakes are thought to play a major role in the initiation of the rapid ice flow (Bell et al., 2007, https://doi.org/10.1038/nature05554). Satellite altimetry observations have even suggested several actively filling and draining subglacial lakes beneath the main trunk (B. E. Smith et al., 2009, https://doi.org/10.3189/002214309789470879). We present new data of the geometry of this glacier and investigate its basal properties employing radio-echo sounding. Using ice sheet modeling, we were able to constrain estimates of radar absorption in the ice, but uncertainties remain large. The magnitude of the basal reflection coefficient is thus still poorly known. However, its spatial variability, in conjunction with additional indicators, can be used to infer the presence of subglacial water. We find no clear evidence of water at most of the previously proposed lake sites. Especially, locations, where altimetry detected active lakes, do not exhibit lake characteristics in radio-echo sounding. We argue that lakes far upstream the main trunk are not triggering enhanced ice flow, which is also supported by modeled subglacial hydrology.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    Impact of snow accumulation on CryoSat-2 range retrievals over Arctic sea ice: An observational approach with buoy data (2015)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, ISSN: 0094-8276
    Details
    Publication Date: 2019-07-17
    Description: Radar altimetry measurements of the current satellite mission CryoSat-2 show an increase of Arctic sea ice thickness in autumn 2013, compared to previous years but also related to March 2013. Such an increase over the melting season seems unlikely and needs to be investigated. Recent studies show that the influence of the snow cover is not negligible and can highly affect the CryoSat-2 range retrievals if it is assumed that the main scattering horizon is given by the snow-ice interface. Our analysis of Arctic ice mass balance buoy records and coincident CryoSat-2 data between 2012 and 2014 adds observational evidence to these findings. Linear trends of snow and ice freeboard measurements from buoys and nearby CryoSat-2 freeboard retrievals are calculated during accumulation events. We find a positive correlation between buoy snow freeboard and CryoSat-2 freeboard estimates, revealing that early snow accumulation might have caused a bias in CryoSat-2 sea ice thickness in autumn 2013.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    Impact of snow accumulation on CryoSat-2 range retrievals over Arctic sea ice: An observational approach with buoy data (2015)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, 42(11), pp. 4447-4455
    Details
    Publication Date: 2016-02-08
    Description: Radar altimetry measurements of the current satellite mission CryoSat-2 show an increase of Arctic sea ice thickness in autumn 2013, compared to previous years but also related to March 2013. Such an increase over the melting season seems unlikely and needs to be investigated. Recent studies show that the influence of the snow cover is not negligible and can highly affect the CryoSat-2 range retrievals if it is assumed that the main scattering horizon is given by the snow-ice interface. Our analysis of Arctic ice mass balance buoy records and coincident CryoSat-2 data between 2012 and 2014 adds observational evidence to these findings. Linear trends of snow and ice freeboard measurements from buoys and nearby CryoSat-2 freeboard retrievals are calculated during accumulation events. We find a positive correlation between buoy snow freeboard and CryoSat-2 freeboard estimates, revealing that early snow accumulation might have caused a bias in CryoSat-2 sea ice thickness in autumn 2013.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
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  • 6
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    Evidence of Cascading Subglacial Water Flow at Jutulstraumen Glacier (Antarctica) Derived From Sentinel-1 and ICESat-2 Measurements (2021)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, 48(20), ISSN: 0094-8276
    Details
    Publication Date: 2021-10-22
    Description: Migration of subglacial water underneath thick Antarctic ice is difficult to observe directly but is known to influence ice flow dynamics. Here, we analyze a 6-year time series of displacement maps from differential Sentinel-1 SAR interferometry (DInSAR) in the upstream region of Jutulstraumen Glacier. Our results reveal short-term (between 12 days and 1 year) interconnected subsidence- and uplift events of the ice surface, which we interpret as a pressure response to the drainage and filling of subglacial lakes. This indicates an episodic cascade-like water transport with longer quiescent phases in a dynamically stable glacial setting. Abrupt events appear in the DInSAR time series and are confirmed by ICESat-2 altimetry. The events can be traced for a 1-year period along a urn:x-wiley:00948276:media:grl63164:grl63164-math-0001175 km flow path. We are able to observe the migration of subglacial water with unprecedented spatial and temporal resolution, providing a new observational baseline to further develop subglacial hydrological models.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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