North Siberian Permafrost reveals Holocene Arctic Winter Warming

Tuesday, 16 December 2014: 2:55 PM
Hanno Meyer1, Thomas Opel2, Thomas Laepple2, Dereviagin Alexander3, Kirstin Hoffmann4 and Martin Werner5, (1)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Potsdam, Potsdam, Germany, (2)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Potsdam, Department of Periglacial Research, Potsdam, Germany, (3)Moscow State University, Department of Geocryology, Faculty of Geology, Vorob’evy Gory, 119899 Moscow, Russia, Moscow, Russia, (4)Niels Bohr Institute - University of Copenhagen, Copenhagen, Denmark, (5)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany
The Arctic climate has experienced a major warming over the past decades, which is unprecedented in the last 2000 yrs. There are, however, still major uncertainties about the temperature evolution during the Holocene. Most proxy reconstructions suggest a cooling in mid-and late Holocene (e.g. Wanner, 2008), whereas climate model simulations show only weak changes or even a moderate warming (e.g. Lohmann et al., 2013).

In this study, we used ice wedges as promising permafrost climate archive studied by stable water isotope methods. Ice wedges may be identified by vertically oriented foliations, and they form by the repeated filling of winter thermal contraction cracks by snow melt water in spring. Therefore, the isotopic composition of wedge ice may be attributed to the climate conditions of the cold season (i.e. winter and spring). 42 samples of organic material enclosed in ice wedges have been directly dated by Radiocarbon methods. Here, we present the first terrestrial stable oxygen isotope record of Holocene winter temperatures in up to centennial-scale resolution based on permafrost ice wedges (Lena River Delta; Siberian Arctic).

The Lena ice-wedge record shows that the recent isotopic temperatures are the highest of the past 7000 years. Despite similarities to Arctic temperature reconstructions of the last two millennia (Kaufman et al., 2009), it suggests a winter warming throughout the mid and late Holocene, opposite to most existing other proxy records (Wanner, 2008).

This apparent contradiction can be explained by the seasonality of the ice-wedge genesis in combination with orbital and greenhouse gas forcing and is consistent with climate model simulations. We conclude that the present model-data mismatch might be an artefact of the summer bias of the existing proxy records and thus, our record helps to reconcile the understanding of the northern hemisphere Holocene temperature evolution. This is particular true for the Russian Arctic significantly underrepresented in Arctic-wide climate reconstructions.

Kaufman, D. S. et al. Science 325, 1236-1239 (2009).

Wanner, H. et al. Quat. Sci. Rev. 27, 1791-1828, (2008).

Lohmann, G., Pfeiffer, M., Laepple, T., Leduc, G. & Kim, J. H. Clim. Past 9, 1807-1839, (2013).