Distribution of basal melting and freezing beneath tributaries of Ice Stream C: implication for the Holocene decay of the West Antarctic ice sheet

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Abstract:

Ice-stream tributaries connect the relatively slow-moving interior of the West Antarctic ice sheet (WAIS) with the fast-flowing Siple Coast ice streams. Basal water underneath these ice streams reduces basal resistance and enables the fast motion of the ice. Basal melting being the only source for this water, it is important to include the distribution of basal melting and freezing into numerical models assessing the stability of the WAIS. However, it is very difficult to constrain its distribution from existing field observations. Past borehole observations confirmed the presence of a wet bed at Byrd Station in the WAIS interior and at different locations within Siple Coast ice streams. However, the recent discovery of a 12–25 m thick sediment-laden bubble-free basal ice layer at the UpC boreholes indicates that basal freezing is either currently occurring or had occurred upstream during the last glacial–interglacial cycle. We use a flowline model of ice thermodynamics to assess and quantify the spatial and temporal distribution of basal melting and freezing beneath Ice Stream C tributaries, taking into account the geothermal flux, shear heating and heat conduction away from the bed. Under the assumption that the ice was moving over a weak bed (b =1–10kPa) our model is able to reproduce a layer of frozen-on ice similar in thickness to the UpC "sticky spot" basal ice layer. Increased basal melting in the early Holocene possibly could have initiated the Holocene decay of the WAIS, whereas increased freezing rates over the past few thousand years could have decreased the amount of basal water in the system, resulting in a strengthening of the bed. This is consistent with current force-budget calculations for ice-stream tributaries and with observed stoppages and slow-downs of ice streams.

Document Type: Research Article

DOI: http://dx.doi.org/10.3189/172756403781816112

Publication date: January 1, 2003

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  • The Annals of Glaciology is a peer-reviewed, thematic journal published 2 to 4 times a year by the International Glaciological Society (IGS). Publication frequency is determined and volume/issue numbers assigned by the IGS Council on a year-to-year basis and with a lead time of 3 to 4 years. The Annals of Glaciology is included in the ISI Science Citation Index from volume 50, number 50 onwards.

    Themes can be on any aspect of the study of snow and ice. Individual members can make a suggestion for a theme for an Annals issue to the Secretary General, who will forward it to the IGS Publications Committee. The IGS Publication Committee will make a recommendation for an individual themed Annals issue, together with a potential Annals Chief Editor for that issue, to IGS Council. The IGS Council will make the decision whether to proceed, taking into account the spread of topics and the overall capacity for publication of pages in Annals.

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