HR: 10:35h
AN: PP31D-02    [PDF]
TI: Estimating peak last-interglacial warmth in the Eastern Canadian Arctic
AU: * Miller, G H
EM: gmiller@colorado.edu
AF: INSTAAR/Geological Sciences, University of Colorado, Boulder, CO 80309-0450 United States
AU: Francis, D
EM: dfrancis@geo.umass.edu
AF: Geosciences, University of Massachusetts, Amherst, MA 01003 United States
AU: Wooller, M
EM: ffmjw@uaf.edu
AF: Alaska Stable Isotope Facility, University of Alaska, Fairbanks, AK 99775 United States
AU: Fogel, M
EM: fogel@gl.ciw.edu
AF: Geophysical Lab/CIW, Broadbranch Road, Washington,, DC 20015 United States
AU: wolfe, A P
EM: awolfe@ualberta.ca
AF: Earth & Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3 Canada
AB: The last interglacial is represented by stratified lake sediments and buried soils across much of Baffin Island, Arctic Canada. Seven lakes situated distal to the limits of the last glacial maximum Laurentide Ice Sheet outlet glaciers preserve undisturbed interglacial sediments, and one lake just inside this limit yielded stratified interglacial sediment beneath a thin till. Macrofossil remains from all of the interglacial units yield radiocarbon dates in excess of 40 ka. Two of the sites have been dated by luminescence methods to more than 90 ka. All exhibit evidence of terrestrial summers warmer than at any time in the Holocene. Pollen assemblages are dominated by exotic taxa, mostly Alnus and Betula that do not currently live at these sites. Pollen percentages and absolute concentrations are much higher than at any time in the Holocene, but difficulties in separating exotic influxes from locally produced pollen limit quantitative summer paleotemperature estimates. Chironomid assemblages provide a second summer-temperature proxy, and because they live where they are found, are less susceptible to the uncertainties characteristic of palynology at high latitudes. Chironomid transfer functions are based on 40 modern surface samples from Baffin Island, and additional sites from eastern North America and Greenland. One third of the interglacial chironomid taxa are extralimital; collectively the interglacial taxa from two lakes suggest summer temperatures 3 to 10$\deg$C higher than in the Holocene. An alternative method for quantifying summer temperatures is reconstructing d18O of precipitation from the d18O of chironomid larvae chitin. Assuming similar basic circulation patterns in the last and present interglacials, we can estimate mean annual temperatures from the reconstructed d18O of precipitation. These independently derived estimates (one lake) suggest peak last interglacial warmth 2$\deg$C higher than the mid Holocene.
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting