Five thousand years of sediment transfer in a High Arctic watershed recorded in annually laminated sediments from Lower Murray Lake, Ellesmere Island, Nunavut, Canada

cook, t., bradley, r.s., stoner, j.s., and francus, p.

Abstract

Study Location

Lower Murray Lake (81°21’N, 69°32’W) is located in north-central Ellesmere Island, Nunavut, Canada. The 5 km² lake is fed by several small ice caps and contains annually laminated (varved) sediments in its deepest (47 m) basin. Sediment cores were collected in June 2005.

Climate Proxy

Annual sediment mass accumulation was positively correlated with July 600 m free air temperatures at the two nearest weather stations at Alert and Eureka (r²=0.61 and 0.50, respectively). Consequently, we suggest that sediment mass accumulation in Lower Murray Lake is dominantly influenced by July temperatures in the upper watershed which have a controlling influence on snowmelt, streamflow and sediment transport into the lake.

Results

The lowest rates of sediment accumulation and by inference the coldest periods of the record occurred around varve year 1800 AD and prior to ~4200 varve years ago. In contrast, periods of increased sedimentation, and by inference the warmest conditions, occurred in the 12th, 14th, and 20th centuries, and throughout the middle portion of the record, approximately 1000 to 4200 varve years ago. Calibrating mass accumulation rates in terms of July temperatures suggests: (1) recent temperatures are ~2.6 °C higher than temperature minima observed during the Little Ice Age, ca. 1800 AD, (2) maximum temperatures during the past 5200 years exceeded modern values by ~0.6 °C, (3) minimum temperatures observed approximately 4900 varve years before present were ~3.5 °C colder than recent conditions. Click here for the full 5200 year temperature reconstruction.

Related websites

• UMass Climate System Research Center