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  • INT GLACIOL SOC  (2)
  • Taylor & Francis  (2)
  • American Geophysical Union (AGU)  (1)
  • Institute of Electrical and Electronics Engineers (IEEE)  (1)
  • 1
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    Improvement and sensitivity snalysis of thermal thin-ice thickness retrievals (2013)
    Institute of Electrical and Electronics Engineers (IEEE)
    In:  IEEE Transactions on Geoscience and Remote Sensing, 51 (6). pp. 3306-3318.
    Details
    Publication Date: 2020-07-29
    Description: Considering the sea ice decline in the Arctic during the last decades, polynyas are of high research interest since these features are core areas of new ice formation. The determination of ice formation requires accurate retrieval of polynya area and thin-ice thickness (TIT) distribution within the polynya. We use an established energy balance model to derive TITs with MODIS ice surface temperatures (Ts) and NCEP/DOE Reanalysis II in the Laptev Sea for two winter seasons. Improvements of the algorithm mainly concern the implementation of an iterative approach to calculate the atmospheric flux components taking the atmospheric stratification into account. Furthermore, a sensitivity study is performed to analyze the errors of the ice thickness. The results are the following: 1) 2-m air temperatures (Ta) and Ts have the highest impact on the retrieved ice thickness; 2) an overestimation of Ta yields smaller ice thickness errors as an underestimation of Ta; 3) NCEP Ta shows often a warm bias; and 4) the mean absolute error for ice thicknesses up to 20 cm is ±4.7 cm. Based on these results, we conclude that, despite the shortcomings of the NCEP data (coarse spatial resolution and no polynyas), this data set is appropriate in combination with MODIS Ts for the retrieval of TITs up to 20 cm in the Laptev Sea region. The TIT algorithm can be applied to other polynya regions and to past and future time periods. Our TIT product is a valuable data set for verification of other model and remote sensing ice thickness data.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1109/TGRS.2012.2219539
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Sea ice leads detection using SARAL/AltiKa altimeter (2015)
    Taylor & Francis
    In:  Marine Geodesy, 38 . pp. 522-533.
    Details
    Publication Date: 2016-02-23
    Description: Sea ice leads play an essential role in ocean-ice-atmosphere exchange, in ocean circulation, geochemistry and in ice dynamics. Their precise detection is crucial for altimetric estimations of sea ice thickness and volume. This study evaluates the performance of the SARAL/AltiKa altimeter to detect leads and to monitor their spatio-temporal dynamics. We show that a pulse peakiness parameter (PP) used to detect leads by Envisat RA-2 and ERS-1,-2 altimeters is not suitable because of saturation of AltiKa return echoes over the leads. The signal saturation results in loss of 6–10% of PP data over sea ice. We propose a different parameter: maximal power of waveform, and define the threshold to discriminate the leads. Our algorithm can be applied from December until May. It detects well the leads of small and medium size: from 200 m to 3–4 km. So, the combination of the high-resolution altimetric estimates with low-resolution thermal infra-red or radiometric lead fraction products could enhance the capability of remote sensing to monitor sea ice fracturing.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1080/01490419.2015.1019655
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    High radar-backscatter regions on Antarctic sea-ice and their relation to sea-ice and snow properties and meteorological conditions (2011)
    Taylor & Francis
    In:  International Journal of Remote Sensing, 32 (14). pp. 3967-3984.
    Details
    Publication Date: 2014-12-09
    Description: The temporal and spatial variability of sea-ice radar signatures in the Southern Ocean during late winter, spring and early summer from QuikSCAT data is presented. We observe a circumpolar and broad band of sea-ice close to the marginal ice zone that is characterized by very high radar backscatter. This feature is explained through detailed in situ observations of snow and sea-ice properties as well as in relation to meteorological conditions, which were derived from US National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data. Our results indicate that high backscatter regions are caused by metamorphous snow, which forms through re-freezing after short-term melt events. This process is connected with the episodic passes of low-pressure systems entraining warmer air from the north. South of the Antarctic Circumpolar Trough, sea-ice is not affected by this influence and shows spatially homogenous microwave signatures with low backscatter.
    Type: Article , PeerReviewed
    DOI: 10.1080/01431161003801344
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Ice platelets below Weddell Sea landfast sea ice (2015)
    INT GLACIOL SOC
    In:  EPIC3Annals of Glaciology, INT GLACIOL SOC, 56(69), pp. 175-190, ISSN: 0260-3055
    Details
    Publication Date: 2019-12-03
    Description: Basal melt of ice shelves may lead to an accumulation of disc-shaped ice platelets underneath nearby sea ice, to form a sub-ice platelet layer. Here we present the seasonal cycle of sea ice attached to the Ekström Ice Shelf, Antarctica, and the underlying platelet layer in 2012. Ice platelets emerged from the cavity and interacted with the fast-ice cover of Atka Bay as early as June. Episodic accumulations throughout winter and spring led to an average platelet-layer thickness of 4m by December 2012, with local maxima of up to 10 m. The additional buoyancy partly prevented surface flooding and snow-ice formation, despite a thick snow cover. Subsequent thinning of the platelet layer from December onwards was associated with an inflow of warm surface water. The combination of model studies with observed fast-ice thickness revealed an average ice-volume fraction in the platelet layer of 0.25+-0.1. We found that nearly half of the combined solid sea-ice and ice-platelet volume in this area is generated by heat transfer to the ocean rather than to the atmosphere. The total ice-platelet volume underlying Atka Bay fast ice was equivalent to more than one-fifth of the annual basal melt volume under the Ekström Ice Shelf.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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    PAPER (OA)
  • 5
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    The impact of early-summer snow properties on Antarctic landfast sea-ice X-band backscatter (2015)
    INT GLACIOL SOC
    In:  EPIC3Annals of Glaciology, INT GLACIOL SOC, 56(69), pp. 263-273, ISSN: 0260-3055
    Details
    Publication Date: 2015-06-09
    Description: Up to now, snow cover on Antarctic sea ice and its impact on radar backscatter, particularly after the onset of freeze/thaw processes, are not well understood. Here we present a combined analysis of in situ observations of snow properties from the landfast sea ice in Atka Bay, Antarctica, and high-resolution TerraSAR-X backscatter data, for the transition from austral spring (November 2012) to summer (January 2013). The physical changes in the seasonal snow cover during that time are reflected in the evolution of TerraSAR-X backscatter. We are able to explain 76–93% of the spatio-temporal variability of the TerraSAR-X backscatter signal with up to four snowpack parameters with a root-mean-squared error of 0.87–1.62 dB, using a simple multiple linear model. Over the complete study, and especially after the onset of early-melt processes and freeze/thaw cycles, the majority of variability in the backscatter is influenced by changes in snow/ice interface temperature, snow depth and top-layer grain size. This suggests it may be possible to retrieve snow physical properties over Antarctic sea ice from X-band SAR backscatter.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    Retrieval of Wintertime Sea Ice Production in Arctic Polynyas Using Thermal Infrared and Passive Microwave Remote Sensing Data (2019)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Geophysical Research: Oceans, American Geophysical Union (AGU), 124(8), pp. 5503-5528, ISSN: 2169-9275
    Details
    Publication Date: 2022-11-02
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
    Format: application/pdf
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