Dynamics of the Antarctic ice cap
Decleir, H.; Huybrechts, P.; De Vos, L.; Pattyn, F. (1989). Dynamics of the Antarctic ice cap, in: Caschetto, S. (Ed.) Belgian scientific research programme on Antarctica: scientific results of phase I (10/1985-01/1989): 3. Glaciology and climatology. pp. 1-51 In: Caschetto, S. (Ed.) (1989). Belgian scientific research programme on Antarctica: scientific results of phase I (10/1985-01/1989): 3. Glaciology and climatology. Belgian scientific research programme on Antarctica. Science Policy Office of Belgium: Brussel. 280 pp., more In: Belgian scientific research programme on Antarctica. Belgian Science Policy Office: Brussel. , more |
| Authors | | Top | - Decleir, H., more
- Huybrechts, P., more
- De Vos, L.
- Pattyn, F., more
| | |
| Abstract | The Antarctic Ice Sheet plays an important role in the glacio-climatic system of the earth. The cap and the marginal mountain areas in Antarctica contain a fascinating archive of past environmental changes. Modelling these changes and predicting future behaviour is a major task for those concerned with the global environment. In view of this, the development of a 3-D thermo-mechanical model of the Antarctic Ice Sheet was undertaken. In a first stage, a 2-D flowline version has been extensively tested and used toinvestigate the reaction of the East Antarctic Ice Sheet with respect to a full glacial cycle. These studies have , amongst other things brought to light that i) creep instability is unlikely to occur and initate surging of the East Antarctic Ice Sheet ii) the evolution of ice thickness following a glacial- interglacial climatic shift is strongly controlled by the different heat transfer mechanisms and related time scales and iii) that due to the diffusive heat time scale operating on 104 years, a steady state cannot possibly be reached. As the flow and temperature fields were shown to encompass a number of counteracting effects, typical elevation changes in central East Antarctica may not have exeeded 100 m, implying that the palaeotemperature record recovered at Vostok Station is primarily of climatic origin. The complete 3-D model covering the entire Antarctic Ice Sheet has been implemented on a CRAY-2 super computer and experiments with this model are still in progress. First results of some diagnostic runs seem to indicate that i) the model yields stable solutions ii) the diagnostic flow field cannot possibly in accordance with steady state requirements iii) basal ice at pressure melting is confined to West Antarctica, the Antarctic Peninsula, outlet glaciers and the thick interior ice areas of East Antarctica. However, it appears that for a good evaluation of the present state of the ice cap a long time integration over the 160,000 year long Vostok signal is necessary . Interpreting the glacier variations as observed in the marginal mountain areas and explaining the role of those changes in the dynamics of the ice sheet was the second objective of this Research Program. During the Austral summer 1986-87 an expedition to the Sdr Rondane Mountains, Dronning Maud Land, was carried out in collaboration with the Japanese Antarctic Research Expedition (JARE 28). The subglacial relief of the mountains in the central part of the area was mapped, using a gravimeter survey, extending to the previous glaciological work carried out by former Belgian Expeditions. A comparison with radar echo sounding lines allowed to test the new modelling procedure and the gravimetric method in general as compared to the radar technique (within 10%). The results indicate a subglacial fiordlandscape witb overdeepened glacial valleys. One-dimensional flow line models were developed to simulate the glacier behaviour. It shows that some glaciers are in the process of being cut off from the main ice supply and confirms their present local character. As for explaining the glacier expansion in the past, it was shown that a 500m increase in ice thickness can be obtained by an advance of the grounding line towards the edge of the continental shelf. A possible scenario might be a lowering of the sea level with 150m and a temperature drop of 11K. |
|
