NOAA/WDS Paleoclimatology - Unit Lake, Manitoba Holocene Multiproxy Sediment Data

STUDY NOTES: Multiproxy sediment data from Unit Lake, Manitoba for the past 12,000 years. Paleoenvironmental proxies measured include fossil pollen and diatom assemblages, charcoal, magnetic properties (susceptibility and remanance), mineral grain size, bulk density, organic-matter content, elemental geochemistry, sediment cation (K+, Mg2+, Ca2+, Fe2+/Fe3+) and macronutrient (P, N, C) contents, biogenic-silica content, basal peat dates (wetland initiation), and stable isotopes (d13C, d15N). Unit Lake, Manitoba, Canada: 59.404°N, 97.493°W, 294m elevation, 11m water depth.
ABSTRACT SUPPLIED BY ORIGINATOR: The low-Arctic region of western Hudson Bay in interior Canada is one of the most poorly described areas of North America in terms of Holocene climate history. Here, we present new data from a well-dated lake sediment core from northern Manitoba, Canada. We assemble one of the richest multi-proxy datasets to date for a low-Arctic lake and characterize terrestrial and lake processes and exchanges between them. These proxies include fossil pollen and diatom assemblages, charcoal, magnetic properties (susceptibility and remanance), mineral grain size, bulk density, organic-matter content, elemental geochemistry, sediment cation (K+, Mg2+, Ca2+, Fe2+/Fe3+) and macronutrient (P, N, C) contents, biogenic-silica content, basal peat dates (wetland initiation), and stable isotopes (d13C, d15N). The sediment proxies record both broad- and fine-scale (millennial and sub-millennial) climate change. We find indirect evidence for a cool and dry post-glacial period from 9,000 to 6,500 cal yr BP, a warm and moist mid-Holocene period from 6,500 to 2,500 cal yr BP, and a cool and moist late-Holocene period from 2,500 cal yr BP to present. High-resolution geochemical data suggests 300- to 500-year-long dry periods at ~6,500-6,100, 5,300-5,000, 3,300-2,800, and 400-0 cal yr BP. These results suggest that terrestrial and aquatic ecosystem dynamics in the western Hudson Bay region are sensitive to past climate change and are likely to respond to future changes in temperature and precipitation.