Abstract:
Data consists of summer temperature reconstruction based on laminae thickness
in sediments from Upper Soper Lake, Baffin Island, Canada.
ABSTRACT (from the online documentation): Laminated sediments from Upper Soper
Lake on southern Baffin Island provide a new 500-year record of temperature
change in the Arctic. Radiometric dating, using 210 Pb and Pu, shows that
... the
light- and dark-coloured laminae couplets are annually deposited varves. Dark
laminae thickness is strongly correlated to average June temperature from
Kimmirut (r = 0.82), reflecting the influence of temperature on snowmelt and
fluxes of runoff and suspended sediment. This relationship allowed the
construction of a palaeotemperature record that documents large-amplitude
interannual to decadal variability superimposed on distinct century-scale
trends, including 2 deg C average warming and maximum temperatures during the
1900s. Similar patterns of change are seen in individual and regionally
averaged palaeotemperature records from around the circum-Arctic. Upper Soper
Lake records temperatures, rates of change and variance during the twentieth
century that are all anomalously high within the context of the last 500
years, and outside the observed range of natural variability. Comparisons of
Upper Soper Lake and Arctic average palaeotemperature to proxy-records of
hypothesized forcing mechanisms suggest that the recent warming trend is
mostly due to anthropogenic emissions of atmospheric greenhouse gases. The
magnitude of the warming and decade-scale variability throughout the records,
however, indicate that natural forcing mechanisms such as changing solar
irradiance and volcanic activity, as well as positive feedbacks within the
Arctic environment, also play an important role. 
