Climate and environmental change over the past 4000 years in a High Arctic polynya – a biomarker approach

• Main Author: Kumar, Natasha
• Format: Thesis
• Language: unknown
• Published: University of Glasgow 2019
• Subjects: Palaeoclimate, biomarkers, geochemical analyses, IP25, PIP25, North Water Polynya, Arctic, sea ice, climate change, sterols, n-alkanes, highly branched isoprenoids, hopanoids, Holocene, Medieval Warm Period, Little Ice Age, paleoclimate.; Arctic; Canada; Greenland; Climate change; Ice Sheet; North Atlantic; North Atlantic oscillation; Phytoplankton; Sea ice
• Online Access: https://dx.doi.org/10.5525/gla.thesis.38941; http://theses.gla.ac.uk/id/eprint/38941

High-resolution, late Holocene marine sediments are rare due to low accumulation and preservation, thus are of great scientific interest for detailed reconstructions of paleoenvironments. There is high potential for this data to be used in climate modelling and to understand rates of environmental change in the recent geological past. In this study, a continuous (5.43m) sediment core spanning the last 4000 years was obtained from the continental shelf of the North Water Polynya and analysed for lipid biomarkers. Organic compounds such as lipids are obtained from several sources such as plant leaf waxes and microorganisms and are usually well preserved in marine sediments. While biomarker studies have been performed previously in the Arctic, this study is the first to focus on paleoclimate reconstructions using both marine biomarkers (e.g., sterols and HBIs) and terrestrial biomarkers (i.e., n-alkanes, sterols and hopanes). A multi-proxy approach was taken in this study to analyse data using well-established n-alkane proxies such as the Carbon Preference Index (CPI), Average Chain Length (ACL), and ‘portion aquatic’ index (Paq) and newer proxies such as the sea ice proxy, IP25, and the phytoplankton marker-IP25 index, PIP25 combining sterol and HBI data. These data are interpreted as indicators in changes of sea ice extent surrounding the polynya and provides insight into warm and cold periods, as well as, nutrient availability to microorganisms and thus primary productivity. The study identifies globally recognised climatic events such as the Medieval Warm Period (MWP) and the Little Ice Age (LIA) that occur ca. 1200-650BP and ca. 600-100BP, respectively, which highlights the widespread effect of the events in the Northern Hemisphere. The complexity of the North Water Polynya is highlighted in this study, with regional changes occurring on multi-decadal, centennial and millennial scales in response to atmospheric temperature changes, freshwater influxes from the Greenland Ice Sheet, but also to some degree - natural forcings such as the North Atlantic Oscillation, Arctic Oscillation and solar radiation, and anthropogenic influences such as rapidly increasing global temperatures. The timing, magnitude and rate of environmental changes associated with these climatic events within the North Water Polynya are investigated in the context of previously published data on early settlements and migrations within high arctic West Greenland and Canada.