Formation, Flow, and Disintegration Of Ice Shelves

Abstract

ABSTRACT. I ce shelves may develop either by continued thickening of sea ice tha t is held fast to the shore, or by the seaward extension of inla nd ice. For both p rocesses, as well as for an understanding of ablation and of accumula t ion a t the bottom surface of ice shelves, we n eed to understand melting and freezing processes in relation to salinity, temperature, and pressure. Consideration of these factors shows that b asal m elting beneath the thicker p a rts of ice shelves is much greater tha n is generally apprecia ted . This could b e sufficient to bring the estimated mass balance of Antarctica into a pproximate equilibrium. It appears that most Antarctic ice shelves are dependent on the supply of inla nd ice for their continued existence. However the thick layer of sea ice b eneath the Am ery I ce Shelf is readily explained in terms of sub-ice water circula tion.T ransport of h eat a nd mass by water m otion beneath ice shelves has the potential to change ice thicknesses by similar amounts to that caused by internal deformatio n of the ice shelf. Bottom freezing due to thermal conduction througho ut the ice shelf is of minor importa n ce.While attentio n is drawn to the basic equations for fl ow of ice shelves, it is pointed out that they have yet to be applied satisfacto rily to the problem of iceberg calving. This appears from field observations to be due primarily to creep fa ilure of spreading ice shelves, possibly a ided by impact from floating icebergs. R ecent observations show the effectiveness a nd likely quantitative importance of this " big bang" theory of iceberg for mation in Anta rctica.A brief discussio n of the effects of climatic change on the disintegration of ice shelves is presented . R ESUME. Formation, ecoulement et disp arition des platiformes de glace. Les pla teformes de glace p euvent se d evelopper soit p a r epaississement continu de la glace d e m er qui se soude solidement au rivage ou par I'extension vers la m er de la glace recou vra nt une ile. Pour les d eux processus comme pour l'intelligen ce de I'ablation et de I'accumulation a la face inferieure de la b a nquise, nous devons comprendre les m ecanismes lia nt la fusion et le regel a la salinite, a la temperature et a la pression. Des considerations sur l'action de ces facteurs montrent que la fusion a la base sous les parties les plus epaisses de la couverture de glace est b eaucoup plus importa nte qu' o n ne la pensait. Ce phenomene pourra it suffire a faire p asser I'estimation du bila n de masse de l'Anta rctique a un equilibre approximatif. Il semble que la plus gra nd e partie des plateformes de glace Antarctique d ep end pour lui p ermettre de subsister d e \'a pport de la glace continentale. Cep endant I'epaisse couche d e glace de mer sous le Amery I ce Shelf p eut facilement s'expliquer par une circula tion d'eau sous la glace.Les transpor ts d e cha leur et de m asse p ar mouvement d e I'eau sous les pla teformes de glace sont capables de modifier \' ep a isseur de glace da ns les m emes proportio n s q...

The variety and distribution of submarine glacial landforms and implications for ice-sheet reconstruction

“…By contrast, the often very subdued vertical topography associated with GZWs implies limited accommodation space beneath the confining ceilings of ice shelves extending beyond the grounding zone (Dowdeswell & Fugelli 2012;Batchelor & Dowdeswell 2015). This is important information for palaeoclimate reconstruction, in that comparisons between the modern distribution of Antarctic ice shelves and observed atmospheric temperatures show that ice shelves tend not to develop where mean annual temperatures exceed 258C (Robin 1979). The southward migration of the 258C isotherm down the western Antarctic Peninsula, where temperatures have risen by about 2.58C in the past half century or so, has coincided with the break-up of fringing ice shelves (Vaughan & Doake 1996;Domack et al 2005;Turner et al 2005).…”

Distribution of Oxygen Isotope Ratio of Precipitation in the Atlantic-Indian Sectors of the Southern Ocean

“…Moreover, precipitation on the Antarctic continent supplies the fresh water that constitutes the vast ice sheet. This ice sheet slides outward to form ice streams and ice shelves, the terminuses of which are eventually melted and calved (e.g., Robin 1979), supplying continental freshwater to the ocean. In the Southern Ocean surrounding the Antarctic continent, the estimation of the abovementioned freshwater fluxes is important in understanding sea water property and hence global ocean circulation.…”

Temperature investigation and modeling on the Filchner-Ronne Ice Shelf, Antarctica

“…This process is caused by a large circulation system in the water column Olbers, 1989, 1991;.Jenkins, 1991) and can be eXplained by an ice-pump model, which was first introduced by Robin (1979) and Lewis and Perkin (1986). The ice platelets first form a slushy layer at the icc-shelf bottom (Thyssen, 1986;Engelhardt and Determann, 1987), which then condense during its accretion to a compact layer.…”