Browsing by Subject "Greenland"
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(2021)Glaciers and ice caps (GICs) excluding Greenland and Antarctic ice sheets account for large proportion of potential future sea level rise and are losing great amount of their mass in high confidence by 2100. Glacier elevation change observations covering whole Greenland’s GICs are limited to the 21st century and regional geodetic mass balance estimates are scarce. Recent development of photogrammetric software and rediscovery of old aerial photographs has been increasingly used to extend temporal resolution of glacier change studies. Besides for extended mass balance observations, historical photographs may be used in observing glacier surge events to improve their coverage in glacier inventories. In this study, 320 historical aerial photographs from 1953/1954 were photogrammetrically processed to create new digital elevation model (DEM) of the 1953 surface. Comparing the 1953 DEM with 1985 and 2016 DEMs extended the geodetic mass balance records on Nuussuaq peninsula to 63 years. Moreover, differenced DEMs were used with orthophotomosaics to identify glacier surface changes and advances and their possible relation to glacier surges. The study also explored the usage of Open Global Glacier Model (OGGM) with user defined input data for simulating future glacier changes in small scale regional setting. The geodetic mass balance results showed clear change from near equilibrium mass balance in 1953-1985 to overall mass loss in 1985-2016. Glacier surface lowering was found to shift to higher elevations along with the change to negative mass balance and occurred throughout the elevation range in 1985-2016. In contrast to generally retreating glaciers, advancing and/or surface elevation increases at the glacier fronts with glaciomorphological evidence of surging were observed on 5 glaciers. OGGM model is easily applicable for smaller regions but correcting the OGGM calibration with a fit to the geodetic mass balance data didn’t provide explicit result of the re-calibration efficiency. Historical photographs provide source to extend geodetic mass balance estimates and means to observe past glacier changes in more detail. Therefore, their incorporation in glacier change studies should be continued and create consistent datasets over larger regions. More research is needed with additional reference data to assess the reliability of the OGGM performance on a region without the reference data from default reference glacier network and the effect of re-calibrating with geodetic fit.
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The future of Narsap Sermia: Documenting the retreat of a tidewater glacier in Southwest Greenland (2023)The behaviour of Greenland's tidewater glaciers is crucial for the understanding of the Greenland Ice Sheet. The retreat of those marine-terminating glaciers has far-reaching implications, impacting not only the regional hydrography but also the diverse fjord ecosystems. Here, this study investigated the rapid retreat of Narsap Sermia (NS), a tidewater glacier located in Southwest Greenland. Between 1987 and 2022, the volume of ice discharged from NS increased by 45%, a rate more than double the Greenlandic mean. This destabilization led to retreat events occurring in three distinct episodes: 2004-2005, 2010-2012, and 2019-2021. The study identified that changes in subglacial hydrology were pivotal in triggering and sustaining these retreats. Drainage of ice-dammed lakes or increased meltwater resulting from heatwaves over the ice sheet suddenly increased subglacial freshwater discharge, subsequently instigating these retreat events. Once initiated, exposure to elevated ocean temperatures or retreat into a glacial trough further sustained ice loss at the terminus, eventually resulting in a collapse of the glacial front. As of the summer of 2023, Narsap Sermia is still retreating, and the study anticipates that further retreat of approximately 3 kilometers is inevitable. Subsequently, should air and ocean temperatures continue to rise, Narsap Sermia is poised to retreat further for 30 km, dramatically transitioning into a land-terminating glacier. This drastic transformation could occur in as little as 30 years, with profound consequences for local eco-hydrology and nearby communities.
Now showing items 1-2 of 2