Variations of ice sheet geometry, ice flow, and mass distribution in Northeast Greenland in the context of oceanic and atmospheric interactions
Zusammenfassung der Projektergebnisse
The project objectives were (a) to determine the state and the changes of ice sheet geometry, ice flow, and ice mass in the Northeastern part of the Greenland Ice Sheet by exploring and using the new quality and comprehensiveness of sensors such as CryoSat‐2, TerraSAR‐X and TanDEM‐X; and (b) to integrate the results into modelling studies of a companion DFG proposal ("COUPLING") in order to study the linked ice sheet‐ocean‐atmosphere system in the region. For objective (a) a series of methodological developments and data analyses was performed. Concerning radar altimetry analysis, methods to derive volume changes were assessed in a detailed simulation study. They were then applied to CryoSat‐2 data over the entire Greenland Ice Sheet. Concerning TanDEM‐X, the methodology of multitemporal DEM generation and of the correction for absolute height ambiguities was refined. Time series of TanDEM‐X DEMs were used to derive spatially detailed surface elevation maps over the termini of the Northeast Greenland outlet glaciers. As the precise and reproducible delineation of individual glacier drainage basins was identified as an open issue for detailed mass balance studies, a suitable method was developed and implemented. It combines remote‐sensing‐based flow velocity data and DEMs based on both remote sensing and satellite altimetry. Approaches for a combined analysis of surface elevation changes and satellite gravimetry results with the target quantity of ice mass changes were investigated. The results from CryoSat‐2 altimetry and TanDEM‐X multitemporal DEMs as well as GRACE satellite gravimetry are being combined at the time of this report to provide a spatially detailed description of geometry changes and mass changes of the individual outlet glaciers in Northeast Greenland. Objective (b) needed to be modified since the COUPLING proposal was not funded. Therefore, collaborations with external partners were used and are being used to incorporate the project results into more comprehensive studies in the context of ice sheet‐ocean‐atmosphere interaction. Specifically, TanDEM‐X DEM differencing results contributed to a detailed study on ice losses of the floating ice tongue of Nioghalvfjerdsfjorden (79°North) Glacier. This study concluded that increased ocean heat flux has been the cause for continuous thinning, which, if sustained, will lead to a loss of large parts of the ice shelf within a few decades, with significant, but locally restricted thinning upstream of the grounding line in response. TanDEM‐X multitemporal DEMs generated within this project also contributed to a study of seasonal and interannual variabilities of glacier geometry and flow for the Helheim and Kangerlussuaq Glaciers in East Greenland, revealing the role of seasonal elevation variations in modulating the dynamic response of the tidewater glaciers to environmental change. Overall, the project has made important contributions to the evolving research field on ice sheet‐ ocean‐atmosphere interaction by further developing methods for radar altimetry and TanDEM‐X data analysis and their combination, by integrating results into process‐oriented studies, and by serving the qualification of two PhD students.
Projektbezogene Publikationen (Auswahl)
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(2017). Seasonal and interannual variabilities in terminus position, glacier velocity, and surface elevation at Helheim and Kangerlussuaq Glaciers from 2008 to 2016. Journal of Geophysical Research: Earth Surface, 122(9), 1635‐1652
Kehrl, L. M., Joughin, I., Shean, D. E., Floricioiu, D., & Krieger, L.
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Automatic glacier calving front delineation on TerraSAR‐X and Sentinel‐1 SAR imagery. In 2017 IEEE International Geoscience and Remote Sensing Symposium (IGARSS), pp. 2817‐2820
Krieger, L., & Floricioiu, D.
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(2018). Large ice loss variability at Nioghalvfjerdsfjorden Glacier, Northeast‐ Greenland. Nature Communications, 9(1)
Mayer, C., Schaffer, J., Hattermann, T., Floricioiu, D., Krieger, L., Dodd, P. A., Kanzow, T., Licciulli, C., & Schannwell, C.
