Ellesmere Island, Canada. The ecology (limnology) of this small Arctic lake is has
recently undergone profound change, as recorded by the diatom fossils observed in the
sediments. Photo credit: Marianne Douglas.
Photomicrograph of pre-1850 Elison Lake sediment sample, Ellesmere Island, Canada. Shows
scarcity of diatoms before the post-1850 Arctic warming event. Photo credit: Marianne
Photomicrograph of present-day Elison Lake sediment sample, Ellesmere Island, Canada.
Shows abundance of diatoms that characterizes sediment samples younger than 1850. Photo
credit: Marianne Douglas.
illustrates lake sediment records from climatically and limnologically contrasting regions
of Ellesmere Island (M.S.V. Douglas, J.P. Smol, W. Blake Jr., Science 226, 416 (1994);
N.C. Doubleday, M.S.V. Douglas and J.P. Smol, The Science of the Total Environment
160/161, 661 (1995); A.P. Wolfe, in Climate Change in the High Arctic, M. Garneau, Ed.
(Geological Survey of Canada Memoir) in press., The inflection between unsupported and
background (in situ production) 210Pb activities in the Col Pond and
Elison Lake cores indicates apporximately 1850 AD, which coincides with the onset of major
diatom shifts in these cores. The Solstice Lake chronology is based on a linear
interpolation between calendar-age-calibrated radiocarbon ages. This model place the major
diatom changes within the last 120 years. The Lower Dumbell Lake core is without a
radiometric chronology, but also suggests that substantial floristic change occured within
the last 100 to 150 years.), each showing abrupt changes in the composition of fossil
diatom assemblages deposited within approximately the last 150 years. These
biostratigraphic changes are unrelated to differential silica preservation and represent
the greatest floristic shifts of the middle to late Holocene. Taxonomic diversification
with greater representations of littoral and periphytic taxa (A-C), increased diatom algal
biomass (C), and recent diatom (re)colonization (D) are all consistent with the abrupt
19th- to 20th-century shift towards longer summer growing seasons, reduced lake-ice
severity, and greater habitat availability. The limnological consequences of the 19th to
20th century warming appear to be unprecedented in the context of pre-18th century natural
variability. To access the diatom data used to construct this figure, please click here.