Five thousand years of sediment transfer in a High Arctic watershed recorded in annually
laminated sediments from Lower Murray Lake, Ellesmere Island, Nunavut, Canada
Sediments in Lower Murray Lake, northern Ellesmere Island, Nunavut Canada (81°21’N, 69°32’W) contain annual laminations (varves) which provide a record of sediment accumulation spanning the past 5000+ years. Annual mass accumulation rates in Lower Murray Lake were compared to instrumental climate data, long term records of climatic forcing mechanisms and other regional paleoclimate records which indicate that lake sedimentation is positively correlated with regional melt season temperatures driven by radiative forcing. Lower Murray Lake mass accumulation rates were positively correlated with mean July 600 m free air temperatures at the two nearest permanent 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. 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. By calibrating the mass accumulation record in terms of July temperatures we were able to produce a quantitative estimate of the range of past temperature variations at Lower Murray Lake (standard error +/- 1.04 °C). The temperature reconstruction 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.