Research experience
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Feb 2012–
presentResearch: Alfred Wegener Institute for Polar and Marine Research
Alfred Wegener Institute for Polar and Marine Research · Abteilung PeriglazialforschungGermany · Bremerhaven/Potsdam -
Feb 2011–
Dec 2011Research: Humboldt-Universität zu Berlin
Humboldt-Universität zu Berlin · Department of GeographyGermany · Berlin
Publications (8) View all
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Article: Last Glacial Maximum records in permafrost of the East Siberian Arctic
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ABSTRACT: Palaeontological proxy data and cryolithological information from Siberian Arctic permafrost preserves records of late Quaternary climate and environmental conditions in West Beringia and their variability which results from interglacial-glacial and interstadial-stadial dynamics. To date, the Last Glacial Maximum (LGM) period has been rather poorly represented in East Siberian permafrost records. Here, we present pollen, sediment, and ground-ice stable water isotope data obtained from coastal exposures on Bol'shoy Lyakhovsky Island (New Siberian Archipelago, Arctic Ocean) that mirror the coldest conditions during the Sartan period between about 26 and 22 ka BP, using pollen and sediment data for summer conditions and stable water isotope data for winter conditions. The pollen record revealed a cold tundra-steppe vegetation with characteristic predominance of grass pollen over sedge pollen while the stable isotope ice-wedges data indicate extremely cold winter temperatures with mean values of d18O of about -37‰, dD of about -290‰. Combined with available regional LGM permafrost records that extend from the Taymyr Peninsula in the west to the Yana River lowland in the east, the new data set from Bol'shoy Lyakhovsky Island indicate that the regional appearance of LGM conditions depended on atmospheric circulation patterns that were influenced by the extent of the Northern Hemisphere glaciation.Quaternary Science Reviews 09/2011; 30:3139e3151. · 3.97 Impact Factor -
Article: Palaeoclimatic information from stable water isotopes of Holocene ice wedges on the Dmitrii Laptev Strait, northeast Siberia, Russia
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ABSTRACT: The stable isotopic composition (δ18O, δD, d) of three Holocene-age ice wedges at the Dmitrii Laptev Strait, Russia (Oyogos Yar coast, 72.7°N, 143.5°E) was studied at high resolution (100 to 200 samples each) in order to develop palaeoclimatic records. AMS 14C ages of organic matter in the ice prove the Late Holocene age of the studied horizontal ice-wedge profiles and indicate syngenetic growth associated with sediment accumulation. Co-isotopic relationships of wedge ice close to the Global Meteoric Water Line point to a good suitability for palaeoclimate studies and all three profiles show similar isotopic features. A general Late Holocene winter warming trend is inferred from δ18O data changing from about −26‰ to values of −23‰ to −21‰, with periods of marked variability superimposed on the trend. This trend is accompanied by a shift in the d excess from 8‰–11‰ to 5‰–8‰, probably caused by varying proportions of differing moisture sources for precipitation. The highest winter temperatures and an increased influence of regional moisture in recent decades may reflect ongoing Arctic climate change. Copyright © 2010 John Wiley & Sons, Ltd.Permafrost and Periglacial Processes 12/2010; 22(1):84 - 100. · 2.52 Impact Factor -
Article: Severe winter cooling during the Younger Dryas in northern Alaska - evidence from the stable isotope composition of a buried ice-wedge system
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ABSTRACT: The Younger Dryas (YD) interval, from approximately 12.9 to 11.5 kyr cal BP, a rapid reversion to glacial climate conditions at the Pleistocene-Holocene transition, has generally been attributed to the release of meltwater from the Laurentide Ice Sheet to the North Atlantic or Arctic oceans. The reaction of the North Pacific region to this "shutdown" of the thermohaline circulation in the North Atlantic during Younger Dryas is, however, little understood. The YD cold interval is of great interest for understanding rapid natural climate change, especially with regard to recent global warming scenarios. Various archives such as glacier ice, tree rings, lacustrine and marine sediments provide evidence for strong climate variability during the Late Glacial-Holocene transition. In our study, we investigated a relict, buried ice-wedge system within the continuous permafrost zone near Barrow, northern Alaska (71°18'N, 156°40'W). The Barrow ice-wedge system is buried under about three meters of Late Glacial/early Holocene ice-rich sediments. The ice wedges are accessible through a shaft which extends into an underground excavation, where a detailed description and sampling with an electrical chain saw were carried out. Permafrost is not only susceptible to recent climate change, it also may store evidence of these changes in ground ice, especially in ice wedges. Ice wedges can be assessed by stable water isotope methods similar to glacier ice climate reconstructions. Ice wedges are assumed to be indicative of winter climate conditions, because the seasonality of thermal contraction cracking and of the infill of frost cracks are generally related to winter and spring, respectively. In this paper, we present a winter climate record from ice wedges in permafrost of northern Alaska, a region, where paleoclimate records extending beyond the Late Glacial-Holocene transition are generally rather sparse, often restricted to lake sediments and rely mostly on summer indicators such as pollen. This reconstruction is the first radiocarbon-dated centennial-scale stable water isotope record from permafrost at all. The Late Glacial winter climate reconstruction from Barrow ice wedges clearly demonstrates the existence of a Younger Dryas cold event, formerly believed to be reduced or absent in this area. Comparing the Barrow ice-wedge record to Greenland ice cores (such as N-GRIP), we observe similar and contemporaneous isotopic variations in the same order of magnitude, underpinning the climatic relevance of our ice wedge data. The Barrow ice-wedge stable isotope record additionally displays a gradual change of the atmospheric moisture source conditions during the Younger Dryas reflected in a shift of the d excess, potentially being associated with the successive opening of the Bering Strait.04/2010; 12:5677. -
Article: Permafrost evidence for severe winter cooling during the Younger Dryas in northern Alaska
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ABSTRACT: The Younger Dryas cold event, a rapid reversion to glacial climate conditions at the Pleistocene‐Holocene transition, has generally been attributed to the release of meltwater from the Laurentide Ice Sheet to the North Atlantic or Arctic oceans. The reaction of the North Pacific region to this "shutdown" of the thermohaline circulation in the North Atlantic during Younger Dryas is little understood. In this paper, we present the first radiocarbon‐dated centennial‐scale stable water isotope record from permafrost in northern Alaska. This Late Glacial winter climate reconstruction from Barrow ice wedges demonstrates the existence of a Younger Dryas cold event, formerly believed to be reduced or absent in this area. Our stable isotope data display a gradual change of the atmospheric moisture source conditions during the Younger Dryas, likely associated with the successive opening of the Bering Strait.Geophysical Research Letters 02/2010; 37(L03501). · 3.79 Impact Factor -
Article: Lateglacial and Holocene isotopic and environmental history of northern coastal Alaska - Results from a buried ice-wedge system at Barrow
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ABSTRACT: Barrow, the northernmost point in Alaska, is one of the most intensively studied areas in the Arctic. However, paleoenvironmental evidence is limited for northern Alaska for the LateglacialeHolocene transition. For a regional paleoenvironmental reconstruction, we investigated a permafrost ice-wedge tunnel near Barrow, Alaska. The studied site was first excavated in the early 1960s and intercepts a buried ice-wedge system at 3-6 m depth below the surface. A multi-methodological approach was applied to this buried ice-wedge system and the enclosing sediments, which in their combination, give new insight into the Late Quaternary environmental and climate history. Results of geochronological, sedimento-logical, cryolithological, paleoecological, isotope geochemical and microbiological studies reflect different stages of mid to late Wisconsin (MW to LW), Allerød (AD), Younger Dryas (YD), Preboreal (PB), and Late Holocene paleoenvironmental evolution. The LW age of the site is indicated by AMS dates in the surrounding sediments of 21.7 kyr BP at the lateral contact of the ice-wedge system as well as 39.5 kyr BP below the ice-wedge system. It is only recently that in this region, stable isotope techniques have been employed, i.e. to characterize different types of ground ice. The stable isotope record (oxygen: d18O; hydrogen: dD) of two intersecting ice wedges suggests different phases of the northern Alaskan climate history from AD to PB, with radiocarbon dates from 12.4 to 9.9 kyr BP (ranging from 14.8 to 10.6 kyr cal BP). Stable isotope geochemistry of ice wedges reveals winter temperature variations of the Lateglacial-Holocene transition including a prominent YD cold period, clearly separated from the warmer AD and PB phases. YD is only weakly developed in summer temperature indicators (such as pollen) for the northern Alaska area, and by consequence, the YD cold stadial was here especially related to the winter season. This highlights that the combination of winter and summer indicators comprehensively describes the seasonality of climate-relevant processes in discrete time intervals. The stable isotope record for the Barrow buried ice-wedge system documents for the first time winter climate change at the Lateglacial-Holocene transition continuously and at relatively high (likely centennial) resolution.Quaternary Science Reviews 01/2010; 29:3720-3735. · 3.97 Impact Factor
