Is the west Antarctic Ice Sheet disintegrating?

Hughes, Terence J.

doi:10.1029/jc078i033p07884

Cited by 272 publications

(170 citation statements)

References 51 publications

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“…39° E. It is concluded that the ice sheet was shrinking along a part of the chain during this observation period, as estimated using a similar method in the West Antarctic ice sheet (Hughes, 1973;Whillans, 1973;Thomas, 1976). However, surface lowering was not necessarily · taking place over the entire area of Mizuho Plateau.…”

Section: Discussionmentioning

confidence: 96%

“…Using their data, Nye ( 1975) discussed the resultant lowering of the ice-sheet surface. Meanwhile, it was suggested that the West An tarctic ice sheet is currently thinning (Hughes, 1973;Weertman, 1976 ;Thomas, 1976) and is slightly thinning or stable (Whillans, 1973(Whillans, , 1976(Whillans, , 1977. Thomas ( 1976) estimated that the Ross Ice Shelf is growing thicker by almost I m a-I in the vicinity of its grounding line.…”

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confidence: 99%

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Thinning of the Ice Sheet in Mizuho Plateau, East Antarctica

Naruse

1979

J. Glaciol.

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ABSTRACT. Surveys of a triangulation chain 250 km in length were carried out in December 1969and December 1973-January 1974 along the surface contour lines from 2 250 m to 2 600 m in Mizuho Plateau, East Antarctica. Horizonta l velocities were obtained as small values near the Yamato Mountains, while they had maxima of more than 2o ± 0.7 m a-I a round long. 39° E., lat. 72° S. in the drainage of the Shirase G lacier. Submergence velocities showed la rge valu es, such as (0.7 to 1)± 0.25 m a -I, in the region along lat. 72° S . from long. 39° E. eastward to long. 43° E. The amount of snow accumulation there, of average thi ckness 0.2 m a -I, was not enough to compensate for the deficit of the ice mass caused by the submergence flow. It follows that the ice sheet was thinning there. It is suggested that the ice sheet of Mizuho Plateau is in an unstable conditio n as a whole.R EsuME. m a -I autour de 39° E., 72° S. Les vitesses verticales indiquent de forts affa issements tels que de 0,7 a I ± 0,25 m a -I dans la region du parallele de 72° S . entre 39° E. a 43° E. Le niveau d'accumulation de la neige en ce point 0,2 m a -I de l'epaisseur moyenn e, n' etait pas suffisant pour compenser le deficit de la masse d e glace cause par l' eco ulement vel'S le fond. 11 s'en suit que la calotte glaciaire est ici en voie d'amincissem ent. On emet l'hypothese que la calotte glaciaire de Mi zuho Plateau toute e ntiere est dans l'ensemble dans un etat instable. ZUSAMMENFASSUNG. Die Ausdiinnung des Eisschildes au! dem Mi z uho-Plateau, Ostantarktis.In den SiidsommeI'n 1969 und 1973/74 wurde la ngs des 72 siidl. P a ra llelkreises auf dem Mizuho-Plateau, O stantarktis, eine Tria ngulationskette von 250 km Lange eingemessen. Nahe dem Yamato Mountains waren die H orizontalgeschwindigkeiten gering, wahrend sie sum 39° E , 72° S Maximalwerte von iibcr 2o ± o·7 m pro Jahr erreichten. Die Vertikalgeschwindigkeiten deutete n a uf ein betrachtliches Absinken, wie etwa 0,7 bis I ± o,25 m pro J a hr im Gebiet langs des 72. siidl. P arallelkreises von 39° E ostwarts bis 43° E. Die Menge del' Schneeakkumulation in diesem Gebiet, die im Mittel 0,2 m pro Jahr betragt, reicht ni cht zum Ausgleich des Massendefizits, das durch die Abtauchbewegung entsteht. AIs Folge e rgibt sich eine Ausdiinnung des Eises. E~ ist anzunehmen, dass del' Eisschild a uf dem Mi zu ho Plateau sich in seineI' Gesamtheit instationar verhalt.

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Section: Discussionmentioning

confidence: 96%

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confidence: 99%

Thinning of the Ice Sheet in Mizuho Plateau, East Antarctica

Naruse

1979

J. Glaciol.

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“…There is considerable disagreement concerning the current state of equilibrium of the West Antarctic ice sheet. Hughes ( 1975) suggested that the ice sheet may be collapsing, and measurements of surface strain-rate that were made near the ice-sheet summit have been interpreted as indicating thinning of perhaps a few centimetres per year (Whillans, 1973(Whillans, , 1977Hughes, 1973;Thomas, 1976) . There is poor agreement between the various estimates of thinning-rate because of lack of information on the behavior of deep ice, and errors are difficult to assess since the result is rather sensitive to errors in the strain-rate measured perpendicular to the flow direction.…”

Section: The Stability Of the West Antarctic Ice Sheetmentioning

confidence: 99%

The Dynamics of Marine Ice Sheets

Thomas

1979

J. Glaciol.

189

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ABSTRACT. Marine ice sh eets rest on land that, for the most part, is below sea-level. Ice that flows across the grounding line, where the ice sheet becomes a float, either calves into icebergs or forms a floating ice shelf joined to the ice sheet. At the grounding line there is a transition from ice-sheet dynamics to ice-shelf dynamics, and the creep-thinning rate in this region is very sensitive to sea depth; rising sea-level causes increased thinning-rates a nd grounding-line retreat, falling sea-level has the reverse effect . If the bedrock slopes down towards the centre of the ice sheet there may be only two stable modes: a freely-floating ice shelf or a ma rine ice sheet that extends to the edge of the continental shelf. Once started, collapse of such an ice sheet to form a n ice shelf may take place extremely rapidly. Ice sh elves which form in embayments of a marine ice sh eet, or which are partially grounded, have a stabilizing influence since ice flowing across the grounding line has to push the ice shelf past its sides. Retreat of the grounding line tends to enlarge the ice shelf, which ultimately may become large enough to prevent excessive outflow from the ice sheet so that a new equilibrium grounding line is established ; removal of the ice shelf would allow r etreat to continue. During the late-Wisconsin glacial maximum there may have been marine ice sheets in the northern hemisphere but the only current exa mple is the W est Antarctic ice sh eet. This is buttressed by the Ross and Ronne Ice Shelves, and if clima tic warming were to prohibit the ex isten ce of these ice shelves then the ice sheet would collapse. Field observations suggest that, a t present, the ice sh eet may be advancing into parts of the R oss I ce Shelf. Such advance, however, would not ensure the secu rity of the ice sh eet since ice streams that dra in to the north appear to fl ow directly into the sea with little or no ice shelf to buttress them. If these ice streams do not flow over a sufficiently high bedrock sill then they provide the most likely avenues for ice-sh eet retreat. R EsuME. La dynamique des calottes glaciaires marines. L es calottes glaciaires marines resposent sur un sol qui, pour la plus gran de part est en dessous du ni veau de la mer. La glace qui s'ecoule a travers la ligne d e decollem ent, lorsq ue la glace commence a flotter, soit vele en icebergs soit form e une cou verture de glace qui se raccorde a la calotte glaciaire. A la lign e de decollement il y a un e transition de la dynamique des calottes a celle des plateformes d e glace, et I'amin cissement dli au mouvement des glaces dans cette region est tres sensible a la profondeur d e la mer; si le niveau marin s'eleve, la vitesse de I'amincissement s'accroit et la ligne d e decollement recul e, un e baisse du niveau des mers a I'effet inverse. Si la pente du lit rocheux descend vers le centre de la calotte gl aciaire il ne peut y avoir que d eux etats stables : une plateforme flottant librement ou une calotte glacia ire marine qui s'etend jusqu'a l...

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“…RonnelFilchner and Ross ice shelves especially, probably play a significant role in influencing the evolution of the West Antarctic Ice Sheet (WAIS) whose base is mostly below sea level and so may be vulnerable to small changes in thickness around itsmargin (e.g. Hughes 1973, Mercer 1978,ThomasetaL 1979. TheAntarctic Peninsula Ice Sheet is somewhat different from the rest of WAIS, in that it covers a mountainous terrain with the bedrock mostly well above sea level.…”

Section: Introductionmentioning

confidence: 99%

Implications of the break-up of Wordie Ice Shelf, Antarctica for sea level

Vaughan

1993

Antartic science

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Temperature records in the Antarctic Peninsula have shown a climatic warming of 1.5"C over the past 30 years and a number of ice shelves have retreated. The most dramatic retreat has been that of Wordie Ice Shelf which has undergone a catastrophic disintegration since the 1960s. Understanding the cause and mechanism of the break-up may provide important clues to the fate of ice shelves farther south which, it has been suggested, help to stabilize the West Antarctic Ice Sheet. The break-up of Wordie Ice Shelf has been analysed using Landsat and SPOTimagery. Theseobservationsshowthattherelativecontributionofthevariousinput glacierstothe grounding line flux has not altered during the break-up. This means that the effect of the rapid and almost complete removal of the ice shelf has not been transmitted upstream and is not causing a rapid increase in velocities on the input glaciers. The volume of grounded ice in the catchment of Wordie Ice Shelf will thus, be largely unaffected by the break-up and there will be no significant contribution to sea level change. Since other ice shelves around the Antarctic Peninsula are also fed by relatively steep mountain glaciers the effect of the loss of the ice shelves on sea level would be likely to be similarly small.

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Is the west Antarctic Ice Sheet disintegrating?

Cited by 272 publications

References 51 publications

Thinning of the Ice Sheet in Mizuho Plateau, East Antarctica

Thinning of the Ice Sheet in Mizuho Plateau, East Antarctica

The Dynamics of Marine Ice Sheets

Implications of the break-up of Wordie Ice Shelf, Antarctica for sea level

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