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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.
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.
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.
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.