The impact of freshwater and brines from Arctic shelf regions on the transformation of water masses along the Arctic Ocean continental margin
Zusammenfassung der Projektergebnisse
The overall purpose of the project was to provide a quantitative observationally based assessment of circulation and water mass transformation processes along the continental margin of the Eurasian Basin of the Arctic Ocean. Fractions of river water and sea-ice meltwater in the low-saline near-surface layer ("halocline") were quantified by a combination of salinity and stable oxygen isotope (δ18O) data of sea water obtained from measurements performed within the project. Several samples and datasets from the continental slope of the Eurasian Basin were obtained in the frame of the Nansen and Amundsen Basins Observational System (NABOS) project. In addition, a geographically widespread quasi-synoptic data and sample set from the Eurasian Basin and part of the Canadian Basins was obtained with RV Polarstern during the International Polar Year 2007. Based on these datasets it appears now that the strong frontal systems within the Arctic Ocean halocline are not only subject to inter-decadal changes but also to considerable inter-annual changes. The results from the central Arctic Ocean were connected to δ18O-based tracer studies on the Siberian shelves that revealed the sea-ice related formation of local brine-enriched bottom waters. The distribution of river water and sea-ice meltwater at the continental margin of the Laptev Sea in the Siberian Arctic is related to an export of waters from the shelves found to be controlled by regional atmospheric forcing. The correlation between river water and sea-ice signals in the Eurasian Basin of the Arctic Ocean is in contrast to results reported from the continental margin of the Beaufort Sea in the Canadian Basin of the Arctic Ocean, where variations in sea-ice meltwater and river water were found to be independent from each other. River water and seaice signals in the Arctic Ocean interior are mainly found at 30 to 50 m water depth with a maximum over the Lomonosov Ridge within the Transpolar Drift that transports Siberian shelf waters across the Arctic Ocean southwards towards the North Atlantic. The geographically distinct definition of this maximum demonstrates the rapid release and transport of signals from the shelf regions in discrete pulses within the Transpolar Drift. The ratio of sea-ice derived brine influence and river water is roughly constant within each layer of the Arctic Ocean halocline in the Eurasian Basin of the Arctic Ocean. The results of our study allow an identification of the layers of the Arctic Ocean halocline primarily influenced by sea-ice formation in coastal polynyas and of layers primarily influenced by sea-ice formation over the open ocean. Accordingly we could use the ratio of sea-ice derived brine waters and river water to link the maximum in brine influence within the Transpolar Drift seen in 2007 with a pulse of shelf waters from the Laptev Sea that was likely released in summer 2005. It is known that there are inter-decadal variations in the distribution of the Pacific component in the Arctic Ocean. It is not known whether the strong variations and the rapid transport of signals from the shelf regions in discrete pulses observed 2007 within the Transpolar Drift are a permanent feature and whether they are related to the absence of Pacific waters during that time. Further studies are needed to understand the potential feedbacks within the Arctic Ocean hydrography and within the ongoing and potential changes related to climate change.
Projektbezogene Publikationen (Auswahl)
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2008: The effects of atmospheric vorticity on the seasonal hydrographic cycle over the eastern Siberian Shelf, Geophysical Research Letters, 35, L03619, 2008
Dmitrenko, I. A., Kirillov, S. A., Tremblay, L. B., Bauch, D. and Makhotin, M.
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Oceanology. Doklady Akademii Nauk, 2008, Vol. 418, No. 3, pp. 401–406
A.Yu. Rozhkova, I.A. Dmitrenko, D. Baukh, L.A. Timokhov
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Variations in Characteristics of the Barents Branch of the Atlantic Water in the Nansen Basin under the Influence of Atmospheric Circulation over the Barents Sea. Doklady Earth Sciences, Vol. 418, No. 1, pp. 149–154, 2008
Rozhkova, A. Yu., I. A. Dmitrenko, D. Bauch, and L. A. Timokhov
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Barents Sea upstream events impact the properties of Atlantic water inflow into the Arctic Ocean: Evidence from 2005-2006 downstream observations, Deep Sea Res. I, 2009
Dmitrenko, I. A., D. Bauch, S. A. Kirillov, N. Koldunov, P. J. Minnett, V. V. Ivanov, J. A. Hölemann, and L. A. Timokhov
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Exchange of Laptev Sea and Arctic Halocline waters in response to atmospheric forcing, J. Geophys. Res., 114, C05008, 2009
Bauch, D., I. A. Dmitrenko, C. Wegner, J. A. Hölemann, S. A. Kirillov, L. A. Timokhov, and H. Kassens
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Seasonal modification of the Arctic Ocean intermediate water layer off the eastern Laptev Sea continental shelf break, J. Geophys. Res., 2009
Lalande, L. Kaleschke, D. Bauch, J. Hölemann, and L. A. Timokhov
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Impact of the Arctic Ocean Atlantic water layer on Siberian shelf hydrography, J. Geophys. Res., 115, C08010, 2010
Dmitrenko, I. A., S. A. Kirillov, L. B. Tremblay, D. Bauch, J. A. Hölemann, T. Krumpen, H. Kassens, C. Wegner, G. Heinemann, and D. Schröder
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Atlantic Water advection to the eastern Fram Strait multiproxy evidence for late Holocene variability, Palaeogeography Palaeoclimatology Palaeoecology, 308(3-4), pp. 264-276, 2011
Werner, K., R. F. Spielhagen, D. Bauch, H. C. Hass, E. Kandiano, and K. Zamelczyk
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Atmospheric controlled freshwater release at the Laptev Sea Continental margin, Polar Research, 30: 5858, 2011
Bauch, D., M. Gröger, I. Dmitrenko, J. Hölemann, S. Kirillov, A. Mackensen, E. Taldenkova, N. Andersen
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Origin of freshwater and polynya water in the Arctic Ocean halocline in summer 2007, Progress in Oceanography, 482-495, 2011
Bauch, D., M. Rutgers van der Loeff, N. Andersen, S. Torres-Valdes, K. Bakker, and E. P. Abrahamsen
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Properties of the Atlantic derived halocline waters over the Laptev Sea continental margin: Evidence from 2002 to 2009, J. Geophys. Res., 2011
Dmitrenko, I. A., V. V. Ivanov, S. A. Kirillov, E. L. Vinogradova, S. Torres-Valdes, and D. Bauch
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The Arctic shelf regions as a source of freshwater and brine-enriched waters as revealed from stable oxygen isotopes, Polarforschung, 80(3), 127-140, 2010 (publ. 2011)
Bauch, D., J. Hölemann, N. Andersen, E. Dobrotina, A. Nikulina, and H. Kassens
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Dissolved iron in the Arctic shelf seas and surface waters of the central Arctic Ocean: Impact of Arctic river water and icemelt, J. Geophys. Res., 117(C1), C01027, 2012
Klunder, M. B., D. Bauch, P. Laan, H. J. W. de Baar, S. van Heuven, and S. Ober
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Shelf-basin exchange times of Arctic surface waters estimated from 228Th/228 Ra disequilibrium, Journal of Geophysical Research, 117(C03024), 2012
Rutgers van der Loeff, M., P. Cai, I. Stimac, D. Bauch, C. Hanfland, T. Roeske, and S. B. Moran
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Utility of dissolved Ba in distinguishing North American from Eurasian runoff in the light of its part in biogeochemical cycling of the Arctic Ocean, Marine Chemistry, 132-133, 1-14, 2012
Roeske, T., D. Bauch, M. R. v. d. Loeff, and B. Rabe
