Sedimentary pellets as an ice cover proxy in a High Arctic ice-covered lake

Tomkins, J.D., Lamoureux, S.F., Antoniades, D., and Vincent, W.F.

Abstract

Study Location

Lake A is a meromictic, perennially ice-covered lake on the northern coast of Ellesmere Island, Nunavut, Canada. The 4.9 km² lake is located at 4 m a.s.l. within an unglacierized, 37 km² catchment in the Challenger Mountains. Sediment cores were obtained from Lake A in spring 2005 and 2006.

Climate Proxy

Within the lake’s sedimentary record are small, sub-rounded sedimentary pellets that are composed of coarser material than the surrounding sediment. These pellets are found within sediment cores throughout the lake and they are interpreted to be formed through ice-rafting processes. Pellets are deposited during summers with reduced ice cover, when sediment held within the lake’s ice cover is released through ice melt. Thus, the frequency of sedimentary pellets within Lake A’s sedimentary record is a proxy record of ice cover and, by extension, summer temperature.

Results

A varve chronology was developed for Lake A and used to develop an age-depth model with which to date the sedimentary pellet frequency record. The resulting ~1000-year record identifies periods with more summers with reduced ice cover ca. 1582-1774 AD and, most notably, after 1891 AD. Prior to 1582 AD and from 1775-1890 AD, ice cover is interpreted to have been more persistent. This record largely corresponds with regional melt-season proxy temperature and paleoecological records, particularly during the 1800s and 1900s.

References

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• Fisher, DA, Koerner, RM, Reeh, N (1995) Holocene Climatic Records from Agassiz Ice Cap, Ellesmere Island, NWT, Canada. The Holocene 5: 19-24
• Hughen, KA, Overpeck, JT, Anderson, RF (2000) Recent warming in a 500-year palaeotemperature record from varved sediments, Upper Soper Lake, Baffin Island, Canada. The Holocene, 10: 9-19
• Lamoureux, SF and Bradley, RS (1996) A late Holocene varved sediment record of environmental change from northern Ellesmere Island, Canada. J Paleolimnol 16: 239-255
• Lasca, AN (1997) Climate change from laminated sediments in the Canadian High Arctic. B.A. unpublished thesis. Department of Geology, Bates College, Lewiston, Maine
• Overpeck, J, Hughen, K, Hardy, D, Bradley, R, Case, R, Douglas, M, Finney, B, Gajewski, K, Jacoby, G, Jennings, A, Lamoureux, S, Lasca, A, MacDonald, G, Moore, J, Retelle, M, Smith, S, Wolfe, A, Zielinski, G (1997) Arctic environmental change of the last four centuries. Science 278: 1251-1256

Related Websites:

• EVEX Laboratory, Queen’s University