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Title:
A tentative record of the last 1,000 years of Greenland temperature from occluded air in the GISP2 ice core
Authors:
Kobashi, T.; Severinghaus, J. P.; Barnola, J.; Kawamura, K.; Beaudette, R.
Affiliation:
AA(Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093 United States ; ), AB(Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093 United States ; ), AC(Laboratoire de Glaciologie et G‚ophysique de l'Environnement, CNRS, Saint-Martin d'H‚res, F-38402 France ; ), AD(Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093 United States ; ), AE(Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093 United States ; )
Publication:
American Geophysical Union, Fall Meeting 2005, abstract #PP52A-0663
Publication Date:
12/2005
Origin:
AGU
AGU Keywords:
1616 Climate variability (1635, 3305, 3309, 4215, 4513), 1630 Impacts of global change (1225), 1650 Solar variability (7537), 4918 Cosmogenic isotopes (1150), 4932 Ice cores (0724)
Abstract Copyright:
(c) 2005: American Geophysical Union
Bibliographic Code:
2005AGUFMPP52A0663K

Abstract

Ice borehole temperature inversion has been used to reconstruct Greenland surface temperature during the last millennium (Dahl-Jensen et al, Science, 1998). However, this technique does not preserve high frequencies because of diffusion of heat in the ice. Here, we present a tentative reconstruction of the past 1,000 years of central Greenland temperature using nitrogen and argon isotopes from occluded air in the GISP2 ice core. This technique preserves decadal-to-centennial-scale temperature variations and complements the borehole technique. Nitrogen and argon isotopes in the porous snow layer (~80m) experience two isotopic fractionations by gravitation and temperature gradients (ΔT) between the top and bottom of the snow layer. The simultaneous analysis of argon and nitrogen isotopes allows us to separate these two effects, and obtain a history of ΔT in the layer. To a first approximation, ΔT change on decadal to centennial time scales is a surface temperature history because the heat conductivity of snow is much smaller than that of ice, and the heat capacity of the ice sheet is quite large. The preliminary ΔT history (20-year interval) shows a Medieval Warm Period in the 11th to 12th centuries and the Little Ice Age in the 15th to 19th centuries. Furthermore, the record shows a clear similarity with the Be-10 record (a proxy for solar activity) with Wolf, Sporer, Maunder, and Dalton minima clearly seen in the cold periods. This finding is consistent with the hypothesis that solar activity influenced Greenland temperature during the past 1000 years.
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