Holocene Paleo-environmental Variability Reconstructed from a Lake Sediment Record from Southeast Greenland

• Main Author: De Wet, Gregory A
• Format: Text
• Language: unknown
• Published: ScholarWorks@UMass Amherst 2013
• Subjects: Paleoclimate; Lakes; Paleolimnology; Sedimentology; Geochemistry; Geology; Biogeochemistry; Climate; Arctic; Greenland; Climate change; Greenland ice core; ice core; Magnetic susceptibility
• Online Access: https://scholarworks.umass.edu/theses/1032; https://scholarworks.umass.edu/cgi/viewcontent.cgi?article=2192&context=theses

Arctic climate variability over the Holocene has been both extensive and, at times, abrupt. Current understanding of these changes is still quite limited with few high-resolution paleoclimate records available for this period. In order to place observed and predicted 21st century climate change in perspective, reliable and highly resolved paleo-reconstructions of Arctic climate are essential. Using an 8.5 m sediment core from Nanerersarpik Lake, this project will characterize climate changes during the Holocene, including the deglacial transition, the rapid changes that are known to have occurred around 8,200 years ago, the transition from Holocene thermal maximum (HTM) to the colder Neoglacial period, and intervals of abrupt climate change during the late Holocene such as the Medieval Warm Period and Little Ice Age. The 8.5 m sediment core from Nanerersarpik contains a dense gray clay in the lower 0.5m. The upper 8.0m of sediment is light brown and organic-rich with centimeter to half-centimeter laminations, interrupted by mass-movement events. Paleoenvironmental conditions have been interpreted using magnetic susceptibility, grain size, biogenic silica, TOC, C/N, organic lipid biomarkers, and δ13Corg, as well as with high-resolution spectral reflectance and scanning XRF profiles. These parameters allow us to interpret changes in autochthonous productivity and clastic input throughout the Holocene. A chronology for the record has been established using 7 radiocarbon dates. The age-model indicates Nanerersarpik Lake contains an ~8,500-yr sediment record with a linear age/depth relationship and a sedimentation rate of 0.1cm/yr, allowing for potentially decadal scale resolution of environmental changes. An abrupt transition from dense glacial clay to laminated organic rich sediment occurs near the base of the core. This is interpreted as marking the retreat of glacial ice from the catchment around 8,250 cal yr BP. High frequency variations dominate the spectral, scanning XRF, and magnetic susceptibility data and indicate some correlation with Holocene climate intervals. Biogenic silica and TOC analysis indicate broad scale changes in primary productivity generally consistent with known Holocene climatic intervals: the deglacial period, the Holocene Thermal Maximum, and the Neoglacial, with high variability during the late Holocene. High resolution biogenic silica data over the past 1500 cal yr BP show some correspondence to Greenland Ice Core paleotemperature reconstructions, suggesting biogenic silica may be responding to temperature on short timescales and should be used as a paleo-environmental proxy in future studies. Alkenones and glycerol dialkyl glycerol tetraethers were present in Nanerersarpik sediments, suggesting this location or others in SE Greenland might be suitable for future high-resolution paleotemperature studies using biomarkers.