Was there a late-Würm Arctic Ice Sheet?

Hughes, Terence J.; Denton, George H.; Grosswald, M. G.

doi:10.1038/266596a0

Cited by 283 publications

(140 citation statements)

References 22 publications

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“…For example, a 635þ m thick ice stream in the M'Clure Strait that fed an ice shelf beyond its grounding line is suggested in a recent reconstruction of the Late Wisconsinan Laurentide Ice Sheet (England et al, 2009). Our data do not support a continuous 1000 m thick Arctic Ocean ice shelf during the LGM, as previously suggested (Grosswald, 1988;Grosswald and Hughes, 2008;Hughes et al, 1977), principally because there is little evidence to suggest ice-grounding on the Morris Jessup Rise, Lomonosov Ridge or Yermak Plateau during the LGM. All the geophysical and core data indicate notable grounding events prior to the LGM.…”

Section: An Arctic Ocean Ice Shelf During Mis 6 Versus Miscontrasting

confidence: 52%

“…Mercer's hypothesis was further developed by Hughes et al (1977) to involve a continuous 1000 m thick ice shelf covering the Arctic Ocean that, together with surrounding grounded marine and terrestrial ice sheets, behaved as a single dynamic Arctic Ice Sheet during the LGM. In comparison, the mean thickness of the Antarctic ice shelves is estimated to be 440 m, although thicknesses >1000 m can be found near the grounding lines (Lythe et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

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An Arctic Ocean ice shelf during MIS 6 constrained by new geophysical and geological data

Nilsson

O’Regan

Backman

et al. 2010

Quaternary Science Reviews

119

118

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a b s t r a c tThe hypothesis of floating ice shelves covering the Arctic Ocean during glacial periods was developed in the 1970s. In its most extreme form, this theory involved a 1000 m thick continuous ice shelf covering the Arctic Ocean during Quaternary glacial maxima including the Last Glacial Maximum (LGM). While recent observations clearly demonstrate deep ice grounding events in the central Arctic Ocean, the ice shelf hypothesis has been difficult to evaluate due to a lack of information from key areas with severe sea ice conditions. Here we present new data from previously inaccessible, unmapped areas that constrain the spatial extent and timing of marine ice sheets during past glacials. These data include multibeam swath bathymetry and subbottom profiles portraying glaciogenic features on the Chukchi Borderland, southern Lomonosov Ridge north of Greenland, Morris Jesup Rise, and Yermak Plateau. Sediment cores from the mapped areas provide age constraints on the glaciogenic features. Combining these new geophysical and geological data with earlier results suggests that an especially extensive marine ice sheet complex, including an ice shelf, existed in the Amerasian Arctic Ocean during Marine Isotope Stage (MIS) 6. From a conceptual oceanographic model we speculate that the cold halocline of the Polar Surface Water may have extended to deeper water depths during MIS 6 inhibiting the warm Atlantic water from reaching the Amerasian Arctic Ocean and, thus, creating favorable conditions for ice shelf development. The hypothesis of a continuous 1000 m thick ice shelf is rejected because our mapping results show that several areas in the central Arctic Ocean substantially shallower than 1000 m water depth are free from glacial influence on the seafloor.

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Section: An Arctic Ocean Ice Shelf During Mis 6 Versus Miscontrasting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

An Arctic Ocean ice shelf during MIS 6 constrained by new geophysical and geological data

Nilsson

O’Regan

Backman

et al. 2010

Quaternary Science Reviews

119

118

View full text Add to dashboard Cite

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“…These results brought new life into the debate on the existence of a continuous 1000 m thick ice shelf occupying the Arctic Ocean during the LGM (e.g. Hughes et al, 1977;Grosswald and Hughes, 2008). However, QUEEN showed that the LGM ice sheet had limited extension eastward of the Kara Sea (Svendsen et al, 2004) and the ice grounding on the Lomonosov Ridge is dated to have occurred during MIS 6, i.e.…”

Section: Central Arctic Ocean Ice Shelves and Marginal Marine Ice Sheetsmentioning

confidence: 99%

“…Both the impact from a limited ice shelf in the Amerasian Basin and a continuous 1000 m thick ice shelf covering the entire Arctic Ocean (e.g. Hughes et al, 1977) is investigated. The inferred ice shelves clearly have regional cooling effects since they insolate heat flux from the underlying ocean and combined with the, albeit relatively low, surface elevation prevent the snow cover from melting during summer.…”

Section: Central Arctic Ocean Ice Shelves and Marginal Marine Ice Sheetsmentioning

confidence: 99%

New insights on Arctic Quaternary climate variability from palaeo-records and numerical modelling

Jakobsson

Long

Inǵólfsson

et al. 2010

Quaternary Science Reviews

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a b s t r a c tTerrestrial and marine geological archives in the Arctic contain information on environmental change through Quaternary interglacialeglacial cycles. The Arctic Palaeoclimate and its Extremes (APEX) scientific network aims to better understand the magnitude and frequency of past Arctic climate variability, with focus on the "extreme" versus the "normal" conditions of the climate system. One important motivation for studying the amplitude of past natural environmental changes in the Arctic is to better understand the role of this region in a global perspective and provide base-line conditions against which to explore potential future changes in Arctic climate under scenarios of global warming. In this review we identify several areas that are distinct to the present programme and highlight some recent advances presented in this special issue concerning Arctic palaeo-records and natural variability, including spatial and temporal variability of the Greenland Ice Sheet, Arctic Ocean sediment stratigraphy, past ice shelves and marginal marine ice sheets, and the Cenozoic history of Arctic Ocean sea ice in general and Holocene oscillations in sea ice concentrations in particular. The combined sea ice data suggest that the seasonal Arctic sea ice cover was strongly reduced during most of the early Holocene and there appear to have been periods of ice free summers in the central Arctic Ocean. This has important consequences for our understanding of the recent trend of declining sea ice, and calls for further research on causal links between Arctic climate and sea ice.

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“…Questions raised by this possibility will be discussed in a later section. In addition to helping us to predict ice-sheet response to possible changes in climate, an understanding of marine-ice-sheet dynamics may provide valuable insights into past glacial epochs since it appears likely that large portions of the Pleistocene ice sheets rested on rock which was below sea-level (Hughes and others, 1977) .…”

Section: Introductionmentioning

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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Was there a late-Würm Arctic Ice Sheet?

Cited by 283 publications

References 22 publications

An Arctic Ocean ice shelf during MIS 6 constrained by new geophysical and geological data

An Arctic Ocean ice shelf during MIS 6 constrained by new geophysical and geological data

New insights on Arctic Quaternary climate variability from palaeo-records and numerical modelling

The Dynamics of Marine Ice Sheets

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