Antarctic ice-sheet dynamics and climatic change: Modelling and Ice Composition Studies (AMICS): final report

• Main Authors: Lorrain, R., Pattyn, F., Souchez, R., Debecker, F., De Brabander, S., De Smedt, B., Huyghe, A., Samyn, D., Sleewaegen, S., Tison, J.-L., Decleir, H.
• Format: Book
• Language: English
• Published: 2006
• Subjects: Climatic changes; Dynamics; Ice caps; Modelling; Antarctica; Antarctic; Frozen Lake; Lake Vostok; The Antarctic; Antarc*; Cold-based glacier; DML; EPICA; ice core; Ice Sheet
• Online Access: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=109746

The main objective of AMICS (Antarctic ice-sheet dynamics and climatic change: Modelling and Ice Composition Studies) is to contribute to the international research effort leading to an improved understanding of the dynamic behaviour of the Antarctic ice sheet resulting from climatic change, through a better knowledge of the internal ice dynamics and the ice sheet’s interactions with the subglacial environment. To clarify the dynamic interactions between the ice sheet and the subglacial environment a new thermomechanical ice-sheet model was developed, including higher-order stress gradients. Such a model is capable of properly simulating the ice flow in areas characterized by complex basal interaction (ice streams, subglacial lakes, .). As a contribution to the EPICA project, the model is imbedded in a large-scale model of the Antarctic ice sheet to determine the chronology and the origin of the ice within the EPICA DML ice core. A comprehensive effort to improve our understanding of the physical processes at the interface between a frozen lake and a cold-based glacier explained the complex formation of the lake ice cover. It showed how sediments become trapped in lake ice and how this lake has contributed to the formation of the basal ice layer of the adjacent damming glacier. Moreover, an isotopic model has been elaborated for basal freeze-on associated with subglacial upward flow of pore water and tested against two Antarctic outlet glaciers by studying the dD-d18O relationships in the basal ice layers of these glaciers. Investigation of the isotopic composition of the deepest part of the Vostok ice core shows the build-up of a highly deformed basal ice layer. Therefore, Lake Vostok’s behaviour has been reassessed from new and existing ice core data. In view of these results, the higher-order model was applied to the area surrounding subglacial Lake Vostok. This showed for the first time that the surface flattening and turning of the ice flow across the lake are a direct consequence of the lack of friction at the ice-water interface, and that subglacial lakes can be at the origin of enhanced ice flow and the onset of continental ice streams. A detailed numerical investigation of such streams demonstrated that a large variability in glacier response can be expected when interaction with subglacial water flow is considered. Speedup and slowdown of such large flow features may be a result of ice piracy of neighboring streams. The AMICS project has demonstrated that basal processes play an important - if not crucial - role in the ice flow of the vast interior of the ice sheet, a zone which was previously thought of being unconditionally stable. Subglacial interactions determine the onset of fast-flowing areas such as ice streams, which has its consequence for the stability of the Antarctic ice sheet with changing climate.