North Siberian ice wedges reveal Arctic winter warming thoughout the Holocene

• Main Authors: Meyer, Hanno, Opel, Thomas, Laepple, Thomas, Dereviagin, Alexander Yu, Hoffmann, Kirstin
• Format: Conference Object
• Language: unknown
• Published: 2014
• Subjects: Arctic; Ice; lena river; permafrost; wedge*
• Online Access: https://epic.awi.de/id/eprint/36111/; https://hdl.handle.net/10013/epic.44020

The Arctic climate has experienced a major warming over the past decades, which is unprecedented in the past 2 kyrs. There are, however, still major uncertainties about the temperature evolution during the Holocene. Most Northern Hemisphere proxy reconstructions suggest a cooling in mid-and late Holocene (e.g. Wanner et al., 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 most promising climate archive in permafrost that were 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 (δ18O, δD, d excess) of wedge ice may be attributed to the cold period climate conditions (winter and spring). 42 samples of organic material enclosed in ice wedges has been directly dated by Radiocarbon methods. Here, we present the first stable-isotope winter proxy record in up to centennial-scale resolution from permafrost ice wedges (Lena River Delta; Siberian Arctic) for the Holocene. The Lena ice-wedge record shows that the recent isotopic temperatures were unprecedented in the past 8000 years. While confirming the Arctic temperature reconstructions of the last two millennia (Kaufman et al., 2009), it suggests a winter warming throughout the mid and late Holocene, thus contradicting most existing other proxy records (Wanner et al., 2008). This apparent contradiction can be explained by (1) the seasonality of the ice-wedge genesis and season-specific orbital forcing, (2) greenhouse gas forcing as well as by (3) regional peculiarities (i.e. the marine transgression). We believe that the present model-data mismatch might be an artefact of the summer bias of the existing proxy records and thus, our record provides important new information for the understanding of the seasonality aspect in the northern hemisphere Holocene temperature ...