NEOGLACIAL COOLING AND 20TH CENTURY WARMTH PRESERVED IN THE SEDIMENT RECORD OF PROGLACIAL LAKE LONGSPUR, BAFFIN ISLAND, CANADA

It has been debated whether anthropogenic induced global warming has abated a natural climatic cooling trend. It is important, therefore, to obtain high resolution climate records of neoglacial cooling to better understand 21^st century global warming. Climate proxies preserved in several well dated lacustrine archives have been used to characterize the timing and extent of local glacier fluctuations since the middle Holocene on Baffin Island, Arctic Canada. Analysis of sediment cores from proglacial Lake Longspur, Baffin Island, have been radiocarbon dated and used in conjunction with rhythmically laminated sediments in surface cores to create a 5,000-year-long record of environmental change. Although this work is still in progress, preliminary textural changes and a pronounced decrease in organic matter suggest that neoglaciation intensified ~2.5 ka. Distinct couplets (assumed to be annual varves) and Cs-137 analysis are used to establish a chronology for ~200-yr-long varve record obtained from surface cores. Varve thickness shows a modest, albeit significant correlation (r²=0.35) to JJA summer temperature from a nearby climate station for 1946 to 1972 (when sediments cease to be varved), indicating some influence of summer temperature on varve thickness. The average varve thickness of this lake is 1.3 mm; average varve thicknesses increases after 1945 from 1.2 mm to 1.8 mm. The increase in varve thickness in the 20^th century corresponds with, and is remarkably similar to, the melt record from the Agassiz and Devon ice caps located several hundred km to the north. This abrupt change in sedimentation may suggest that local glaciers in this basin began accelerated retreat ~60 years ago.  A strong multi-decadal periodicity exists in the varve thickness record, which is also apparent in the ice cap melt layer records, may represent a multi-decadal climate mode such as the North Atlantic or Arctic oscillations. Future research of this lake will include a down core grain-size analysis, cross-correlation with other laminated surface cores, and the addition of several more radiocarbon dates to improve lake core chronology. Combined with existing records, this data will be used to improve the timing and spatial pattern of the onset and termination of Neoglaciation.