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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 6 | Copyright
The Cryosphere, 11, 2743-2753, 2017
https://doi.org/10.5194/tc-11-2743-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 05 Dec 2017

Research article | 05 Dec 2017

Centuries of intense surface melt on Larsen C Ice Shelf

Suzanne L. Bevan1, Adrian Luckman1, Bryn Hubbard2, Bernd Kulessa1, David Ashmore3, Peter Kuipers Munneke4, Martin O'Leary1, Adam Booth5, Heidi Sevestre6, and Daniel McGrath7 Suzanne L. Bevan et al.
  • 1Geography Department, College of Science, Swansea University, Singleton Park, Swansea, SA2 8PP, UK
  • 2Centre for Glaciology, Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK
  • 3School of Environmental Science, Roxby Building, University of Liverpool, Liverpool, L69 7ZT, UK
  • 4Institute for Marine and Atmospheric Research, Utrecht (IMAU), Utrecht University, P.O. Box 80000, 3508 TA Utrecht, the Netherlands
  • 5School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
  • 6School of Geography and Geosciences, University of St Andrews, College Gate, St Andrews, KY16 9AJ, UK
  • 7Department of Geosciences, Colorado State University, Fort Collins, Colorado, USA

Abstract. Following a southward progression of ice-shelf disintegration along the Antarctic Peninsula (AP), Larsen C Ice Shelf (LCIS) has become the focus of ongoing investigation regarding its future stability. The ice shelf experiences surface melt and commonly features surface meltwater ponds. Here, we use a flow-line model and a firn density model (FDM) to date and interpret observations of melt-affected ice layers found within five 90m boreholes distributed across the ice shelf. We find that units of ice within the boreholes, which have densities exceeding those expected under normal dry compaction metamorphism, correspond to two climatic warm periods within the last 300 years on the Antarctic Peninsula. The more recent warm period, from the 1960s onwards, has generated distinct sections of dense ice measured in two boreholes in Cabinet Inlet, which is close to the Antarctic Peninsula mountains – a region affected by föhn winds. Previous work has classified these layers as refrozen pond ice, requiring large quantities of mobile liquid water to form. Our flow-line model shows that, whilst preconditioning of the snow began in the late 1960s, it was probably not until the early 1990s that the modern period of ponding began. The earlier warm period occurred during the 18th century and resulted in two additional sections of anomalously dense ice deep within the boreholes. The first, at 61m in one of our Cabinet Inlet boreholes, consists of ice characteristic of refrozen ponds and must have formed in an area currently featuring ponding. The second, at 69m in a mid-shelf borehole, formed at the same time on the edge of the pond area. Further south, the boreholes sample ice that is of an equivalent age but which does not exhibit the same degree of melt influence. This west–east and north–south gradient in the past melt distribution resembles current spatial patterns of surface melt intensity.

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Five 90 m boreholes drilled into an Antarctic Peninsula ice shelf show units of ice that are denser than expected and must have formed from refrozen surface melt which has been buried and transported downstream. We used surface flow speeds and snow accumulation rates to work out where and when these units formed. Results show that, as well as recent surface melt, a period of strong melt occurred during the 18th century. Surface melt is thought to be a factor in causing recent ice-shelf break-up.
Five 90 m boreholes drilled into an Antarctic Peninsula ice shelf show units of ice that are...
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