Last intact ice shelf in Canadian Arctic may be slipping away [Milne ice shelf, Ellesmere Island]

by Eilís Quinn, Eye on the Arctic, Alaska Dispatch, August 10, 2013

Courtesy Ian Joughin.     

 

The last fully intact ice shelf on northern Ellesmere Island in Canada’s Arctic may soon be slipping away.


Ice shelves found in the north of the island are formed from sea ice and glacier ice, measuring some 100 yards thick. While other ice shelves nearby have long since broken up, the Milne Ice Shelf remained intact, blocking the mouth of the Milne Fjord.

Cracks and fractures

But this year, scientists have noticed fractures to the Milne ice shelf that indicate it may be reaching the end of its life cycle.

“It’s become a maze or a network of many different crevasses, which very much indicates that the ice shelf is reaching its structural-integrity limit,” says Andrew Hamilton, a PhD candidate at the University of British Columbia in Vancouver, Canada, who studies the Milne ice shelf.

“In the coming years it will most likely continue to break up and eventually float away as icebergs or ice islands into the Arctic Ocean.”

This story is posted on Alaska Dispatch as part of Eye on the Arctic, a collaborative partnership between public and private circumpolar media organizations.

http://www.alaskadispatch.com/article/20130810/last-intact-ice-shelf-canadian-arctic-may-be-slipping-away

Arctic sea ice thickness characteristics in winter 2004 and 2007 from submarine sonar transects, JGR 116 (2011), Peter Wadhams, Nick Hughes & João Rodrigues; doi:10.1029/2011JC006982

Journal of Geophysical Research 116 (2011) C00E02; doi:10.1029/2011JC006982

Arctic sea ice thickness characteristics in winter 2004 and 2007 from submarine sonar transects

Peter Wadhams (Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, U.K., and Laboratoire d'Océanographie de Villefranche, Université Pierre et Marie Curie, Villefranche-sur-Mer, France),  Nick Hughes (Forecasting Division for Northern Norway, Norwegian Ice Service, Tromsø, Norway) and  João Rodrigues (Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, U.K.)

Abstract

A transect of the Arctic Ocean by the British submarine Tireless in March 2007 enabled the thickness characteristics of the ice cover to be measured during the winter immediately preceding the exceptional retreat of summer 2007. In this paper we report on mean and modal drafts, probability density functions of draft, and the frequency and depth distribution of pressure ridges, and we compare results with those from an earlier submarine cruise in winter 2004 which covered part of the same area. In the region from north of Fram Strait to Ellesmere Island (about 85° N, 0–70° W) we find no change in mean drafts between 2004 and 2007 though there is a change in ice composition, with more ridging in 2007 but a lesser modal draft. This agrees with the observations of younger ice being driven toward Fram Strait in 2007. The region north of Ellesmere Island continues to be a “redoubt” containing more thick deformed multiyear ice than any other part of the transect. In the west the submarine profiled extensively under the SEDNA ice camp at 73° N 145° W. This is in the same location as the 1976 AIDJEX ice camp and a sonar survey done by a U.S. submarine in April 1976. We found that a large decrease in mean draft had occurred (32%) over 31 years and that in 2007 the SEDNA region contained the thinnest ice of any part of the Arctic surveyed by the submarine; this was a region from which the ice completely retreated during the subsequent summer of 2007.

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Received 21 January 2011; accepted 14 June 2011; published 27 September 2011.

Citation: Wadhams, P., N. Hughes, and J. Rodrigues (2011), Arctic sea ice thickness characteristics in winter 2004 and 2007 from submarine sonar transects, J. Geophys. Res., 116, C00E02, doi:10.1029/2011JC006982

Key Points

• Measurement of sea ice thickness from the submarine during winters of 2004 and 2007
• More first-year ice in 2007 but similar overall mean ice thickness to 2004
• Ice thickness distribution obtained from region later ice free in summer 2007

http://www.agu.org/pubs/crossref/2011/2011JC006982.shtml

Recent melt rates of Canadian Arctic ice caps are the highest in four millennia, by David Fishe et al., Global and Planetary Change, doi:10.1016/j.gloplacha.2011.06.005

Global and Planetary Change, doi:10.1016/j.gloplacha.2011.06.005 

Recent melt rates of Canadian Arctic ice caps are the highest in four millennia

David Fisher, James Zheng, David Burgess, Christian Zdanowicz, Christophe Kinnard, Martin Sharp and Jocelyne Bourgeois

Abstract

There has been a rapid acceleration in ice-cap melt rates over the last few decades across the entire Canadian Arctic. Present melt rates exceed the past rates for many millennia. New shallow cores at old sites bring their melt series up-to-date. The melt-percentage series from the Devon Island and Agassiz (Ellesmere Island) ice caps are well correlated with the Devon net mass balance and show a large increase in melt since the middle 1990s. Arctic ice core melt series (latitude range of 67° to 81° N) show the last quarter century has seen the highest melt in two millennia and the Holocene-long Agassiz melt record shows the last 25 years has the highest melt in 4,200 years. The Agassiz melt rates since the middle 1990s resemble those of the early Holocene thermal maximum over 9,000 years ago.

http://www.sciencedirect.com/science/article/pii/S092181811100097X

"Recent melt rates of Canadian Arctic ice caps are the highest in four millennia" by David Fisher et al., Global and Planetary Change (2011) in press

Global and Planetary Change, doi: 10.1016/j.gloplacha.2011.06.005

Recent melt rates of Canadian Arctic ice caps are the highest in four millennia

David Fisher^a, , , , James Zheng^a, David Burgess^a, Christian Zdanowicz^a, Christophe Kinnard^b, Martin Sharp^c and Jocelyne Bourgeois^a

^aGlaciology Section, Northern Division, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada

^bCentro de Estudios Avanzados en Zonas Aridas-CEAZA, Casilla 599-Campus Andres Bello, Colina El Pino s/n, La Serena, Chile

^cEarth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta T6G 2E3, Canada

(Received 3 January 2011; revised 12 June 2011; accepted 13 June 2011.  Available online 30 June 2011.)

Abstract

There has been a rapid acceleration in ice-cap melt rates over the last few decades across the entire Canadian Arctic. Present melt rates exceed the past rates for many millennia. New shallow cores at old sites bring their melt series up-to-date. The melt-percentage series from the Devon Island and Agassiz (Ellesmere Island) ice caps are well correlated with the Devon net mass balance and show a large increase in melt since the middle 1990s. Arctic ice core melt series (latitude range of 67° to 81° N) show the last quarter century has seen the highest melt in two millennia and The Holocene-long Agassiz melt record shows the last 25 years has the highest melt in 4,200 years. The Agassiz melt rates since the middle 1990s resemble those of the early Holocene thermal maximum over 9,000 years ago.

http://www.sciencedirect.com/science/article/pii/S092181811100097X

M. Zreda et al., Nature, 398, Unblocking of the Nares Strait by Greenland and Ellesmere ice-sheet retreat 10,000 years ago

Nature 398, 139-142 (11 March 1999); doi: 10.1038/18197; received 31 March 1998; accepted 22 December 1998.

Unblocking of the Nares Strait by Greenland and Ellesmere ice-sheet retreat 10,000 years ago

Marek Zreda^*,1, John England², Fred Phillips³, David Elmore⁴ and Pankaj Sharma⁴

1. Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721, USA
2. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, T6G 2E3, Canada
3. Department of Earth and Environmental Science, New Mexico Tech, Socorro, NM 87801, USA
4. Department of Physics, Purdue University, West Lafayette, IN 47907, USA

*Correspondence e-mail: marek@hwr.arizona.edu

Abstract

The extent of glaciation at the northern margin of the Canadian/Greenland high-latitude Arctic region over the past 30,000 years is uncertain. Geological arguments have been made for Greenland and Ellesmere Island ice sheets that coalesced to block the Nares Strait¹, and for restricted ice sheets on the two islands² leaving the strait open, as it is today³. Distinguishing between these two possibilities would provide significant constraints on present understanding of the past circulation between the Arctic and Atlantic oceans⁴,⁵, on estimates of past ice-volume⁶, and on the response of the Greenland ice sheet to climate change⁷. Radiocarbon analyses provide dates for the deglaciation of the islands' coasts, but do not yield information on whether ice filled the strait. Here we present measurements of cosmogenic ³⁶Cl that has accumulated in situ in erratics and glacially polished bedrock on islands within the Nares Strait. These data allow us to determine the time for which the rocks have been recently exposed to the atmosphere, and thus the age of the final deglaciation of the strait. We show that Greenland and Ellesmere ice sheets retreated from the Nares Strait about 10,000 years ago. The strait was filled with ice during the last glaciation, blocking this connection between the Arctic and Atlantic oceans, and supporting the model of extensive and long-lasting ice on land and sea in this region^{8, 9, 10, 11}.

Link to abstract:  http://www.nature.com/nature/journal/v398/n6723/full/398139a0.html