Browsing by Author "Jokinen, Ari-Pekka"

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.