OS Ocean Science OS Ocean Sci. 1812-0792 Copernicus Publications Göttingen, Germany 10.5194/os-10-141-2014 Halocline water modification and along-slope advection at the Laptev Sea continental margin Bauch D. 1 Torres-Valdes S. 2 Polyakov I. 3 Novikhin A. 4 Dmitrenko I. 5 McKay J. 6 Mix A. 6 GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstr. 1–3, 24148 Kiel, Germany Ocean Biogeochemistry and Ecosystems, National Oceanography Centre (NOC), European Way, Southampton, SO14 3ZH, UK International Arctic Research Center and College of Natural Science and Mathematics, University of Alaska Fairbanks, Fairbanks, Alaska, USA Arctic and Antarctic Research Institute, St. Petersburg, Russia Centre for Earth Observation Science, University of Manitoba, Winnipeg, Manitoba, Canada College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA 25 02 2014 10 1 141 154 Copyright: © 2014 D. Bauch et al. 2014 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://os.copernicus.org/articles/10/141/2014/os-10-141-2014.html The full text article is available as a PDF file from https://os.copernicus.org/articles/10/141/2014/os-10-141-2014.pdf

A general pattern in water mass distribution and potential shelf–basin exchange is revealed at the Laptev Sea continental slope based on hydrochemical and stable oxygen isotope data from the summers 2005–2009. Despite considerable interannual variations, a frontal system can be inferred between shelf, continental slope and central Eurasian Basin waters in the upper 100 m of the water column along the continental slope. Net sea-ice melt is consistently found at the continental slope. However, the sea-ice meltwater signal is independent from the local retreat of the ice cover and appears to be advected from upwind locations. <br><br> In addition to the along-slope frontal system at the continental shelf break, a strong gradient is identified on the Laptev Sea shelf between 122° E and 126° E with an eastward increase of riverine and sea-ice related brine water contents. These waters cross the shelf break at ~ 140° E and feed the low-salinity halocline water (LSHW, salinity <i>S</i> < 33) in the upper 50 m of the water column. High silicate concentrations in Laptev Sea bottom waters may lead to speculation about a link to the local silicate maximum found within the salinity range of ~ 33 to 34.5, typical for the Lower Halocline Water (LHW) at the continental slope. However brine signatures and nutrient ratios from the central Laptev Sea differ from those observed at the continental slope. Thus a significant contribution of Laptev Sea bottom waters to the LHW at the continental slope can be excluded. The silicate maximum within the LHW at the continental slope may be formed locally or at the outer Laptev Sea shelf. Similar to the advection of the sea-ice melt signal along the Laptev Sea continental slope, the nutrient signal at 50–70 m water depth within the LHW might also be fed by advection parallel to the slope. Thus, our analyses suggest that advective processes from upstream locations play a significant role in the halocline formation in the northern Laptev Sea.

 References Aagaard, K., Coachman, L. and Carmack, E.: On the halocline of the Arctic Ocean, Deep-Sea Res., 28, 529–545, 1981. Abrahamsen, E. P., Meredith, M. P., Falkner, K. K., Torres-Valdes, S., Leng, M. J., Alkire, M. B., Bacon, S., Laxon, S., Polyakov, I., Ivanov, V., and Kirillov, S.: Tracer-derived freshwater budget of the Siberian Continental Shelf following the extreme Arctic summer of 2007, Geophys. Res. Lett., 36, L07602, <a href="http://dx.doi.org/10.1029/2009GL037341">https://doi.org/10.1029/2009GL037341</a>, 2009. Aksenov, Y., Ivanov, V. V., Nurser, A. J. G., Bacon, S., Polyakov, I. V., Coward, A. C., Naveira-Garabato, A. C., and Beszczynska-Moeller, A.: The Arctic Circumpolar Boundary Current, J. Geophys. Res.-Oceans, 116, C09017, <a href="http://dx.doi.org/10.1029/2010JC006637">https://doi.org/10.1029/2010JC006637</a>, 2011. Anderson, L. G., Andersson, P. S., Björk, G., Peter Jones, E., Jutterström, S., and Wåhlström, I.: Source and formation of the upper halocline of the Arctic Ocean, J. Geophys. Res.-Oceans, 118, 410–421, <a href="http://dx.doi.org/10.1029/2012JC008291">https://doi.org/10.1029/2012JC008291</a>, 2013. Bareiss, J., Eicken, H., Helbig, A., and Martin, T.: Impact of river discharge and regional climatology on the decay of sea ice in the Laptev Sea during spring and early summer, Arct. Antarct. Alp. Res., 31, 214– 229, 1999. Bauch, D., Schlosser, P., and Fairbanks, R. F.: Freshwater balance and the sources of deep and bottom waters in the Arctic Ocean inferred from the distribution of H<sub>2</sub><sup>18</sup>O, Progr. Oceanogr., 35, 53–80, 1995. Bauch, D., Erlenkeuser, H., and Andersen, N.: Water mass processes on Arctic shelves as revealed from <sup>18</sup>O of H<sub>2</sub>O, Global Planet. Change, 48, 165–174, <a href="http://dx.doi.org/10.1016/j.gloplacha.2004.12.011">https://doi.org/10.1016/j.gloplacha.2004.12.011</a>, 2005. Bauch, D., Dmitrenko, I. A., Wegner, C., Hölemann, J., Kirillov, S. A., Timokhov, L. A., and Kassens, H.: Exchange of Laptev Sea and Arctic Ocean halocline waters in response to atmospheric forcing, J. Geophys. Res.-Oceans, 114, C05008, <a href="http://dx.doi.org/10.1029/2008JC005062">https://doi.org/10.1029/2008JC005062</a>, 2009. Bauch, D., Hölemann, J., Andersen, N., Dobrotina, E., Nikulina, A., and Kassens, H.: The Arctic shelf regions as a source of freshwater and brine-enriched waters as revealed from stable oxygen isotopes, Polarforschung, 80, 127–140, 2010. Bauch, D., Gröger, M., Dmitrenko, I., Hölemann, J., Kirillov, S., Mackensen, A., Taldenkova, E., and Andersen, N.: Atmospheric controlled freshwater water release at the Laptev Sea Continental margin, Polar Res., 30, 5858, <a href="http://dx.doi.org/10.3402/polar.v30i0.5858">https://doi.org/10.3402/polar.v30i0.5858</a>, 2011a. Bauch, D., Rutgers van der Loeff, M., Andersen, N., Torres-Valdes, S., Bakker, K., and Abrahamsen, E. P.: Origin of freshwater and polynya water in the Arctic Ocean halocline in summer 2007, Progr. Oceanogr., 91, 482–495, <a href="http://dx.doi.org/10.1016/j.pocean.2011.07.017">https://doi.org/10.1016/j.pocean.2011.07.017</a>, 2011b. Bauch, D., Hölemann, J. A., Dmitrenko, I. A., Janout, M. A., Nikulina, A., Kirillov, S. A., Krumpen, T., Kassens, H., and Timokhov, L.: The impact of Siberian coastal polynyas on shelf-derived Arctic Ocean halocline waters, J. Geophys. Res.-Oceans, 117, C00G12, <a href="http://dx.doi.org/10.1029/2011JC007282">https://doi.org/10.1029/2011JC007282</a>, 2012. Bauch, D., Hölemann, J. A., Nikulina, A., Wegner, C., Janout, M. A., Timokhov, L. A., and Kassens, H.: Correlation of river water and local sea-ice melting on the Laptev Sea shelf (Siberian Arctic), J. Geophys. Res.-Oceans, 118, 550–561, <a href="http://dx.doi.org/10.1002/jgrc.20076">https://doi.org/10.1002/jgrc.20076</a>, 2013. Bordovsky, O. K. and Ivanenkov, V. N.: Modern methods of hydrochemical studies of the ocean, IORAS, Moscow, 1992. Broecker, W. S. and Peng, T. H.: Tracers in the Sea, Eldigio, Palisades, NY, 1982. Cooper, L. W., Whitledge, T. E., Grebmeier, J. M., and Weingartner, T.: The nutrient, salinity, and stable isotope composition of Bering and Chukchi seas waters in and near the Bering Strait, J. Geophys. Res., 102, 12563–12573, 1997. Craig, H.: Standard for reporting concentrations of Deuterium and Oxygen-18 in natural waters, Science, 133, 1833–1834, 1961. Devol, A. H., Codispoti, L. A., and Christensen, J. P.: Summer and winter denitrification rates in western Arctic shelf sediments, Cont. Shelf Res., 17, 1029–1050, <a href="http://dx.doi.org/10.1016/S0278-4343(97)00003-4">https://doi.org/10.1016/S0278-4343(97)00003-4</a>, 1997. Dmitrenko, I. A., Kirillov, S. A., and Tremblay, L. B.: The long-term and interannual variability of summer fresh water storage over the eastern Siberian shelf: Implication for climatic change, J. Geophys. Res.-Oceans, 113, C03007, <a href="http://dx.doi.org/10.1029/2007JC004304">https://doi.org/10.1029/2007JC004304</a>, 2008. Dmitrenko, I. A., Kirillov, S. A., Tremblay, L. B., Bauch, D., Hölemann, J. A., Krumpen, T., Kassens, H., Wegner, C., Heinemann, G., and Schröder, D.: Impact of the Arctic Ocean Atlantic Water layer on Siberian shelf hydrography, J. Geophys. Res.-Oceans, 115, C08010, <a href="http://dx.doi.org/10.1029/2009JC006020">https://doi.org/10.1029/2009JC006020</a>, 2010. Dmitrenko, I. A., Ivanov, V. V., Kirillov, S. A., Vinogradova, E. L., Torres-Valdes, S., and Bauch, D.: Properties of the Atlantic derived halocline waters over the Laptev Sea continental margin: Evidence from 2002 to 2009, J. Geophys. Res.-Oceans, 116, C10024, <a href="http://dx.doi.org/10.1029/2011JC007269">https://doi.org/10.1029/2011JC007269</a>, 2011. Dmitrenko, I. A., Kirillov, S. A., Ivanov, V. V., Rudels, B., Serra, N., and Koldunov, N. V.: Modified Halocline Water over the Laptev Sea Continental Margin: Historical Data Analysis, J. Climate, 25, 5556–5565, <a href="http://dx.doi.org/10.1175/JCLI-D-11-00336.1">https://doi.org/10.1175/JCLI-D-11-00336.1</a>, 2012. Ekwurzel, B., Schlosser, P., Mortlock, R., and Fairbanks, R.: River runoff, sea ice meltwater, and Pacific water distribution and mean residence times in the Arctic Ocean, J. Geophys. Res.-Oceans, 106, 9075–9092, 2001. Gruber, N. and Sarmiento, J. L.: Global patterns of marine nitrogen fixation and denitrification, Global Biogeochem. Cy., 11, 235–266, 1997. Guay, C. K., Falkner, K. K., Muench, R. D., Mensch, M., Frank, M., and Bayer, R.: Wind-driven transport pathways for Eurasian Arctic river discharge, J. Geophys. Res., 106, 11469–11480, 2001. Holmes, R. M., McClelland, J. W., Peterson, B. J., Tank, S. E., Bulygina, E., Eglington, T. I., Gordeev, V. V., Gurtovaya, T. Y., Raymond, P. A., Repeta, R., Staples, R., Striegl, R. G., Zhulidov, A. V., and Zimov, S. A.: Seasonal and annual fluxes of nutrients and organic matter from large rivers to the Arctic Ocean and surrounding seas, Estuaries Coasts, 35, 369–382, <a href="http://dx.doi.org/10.10007/s12237-011-9386-6">https://doi.org/10.10007/s12237-011-9386-6</a>, 2012. Jones, E., Anderson, L., and Swift, J.: Distribution of Atlantic and Pacific water in the upper Arctic Ocean: Implications for circulation, Geophys. Res. Lett., 25, 765–768, 1998. Karcher, M., Gerdes, R., and Kauker, F.: Modeling of ?18O and 99Tc dispersion in Arctic and subarctic seas, ASOF Newsletter, Issue No 5, April 2006, available at: <a href="http://epic.awi.de/epic/Main?static=yes&page=abstract&entry_dn=Kar2006d">http://epic.awi.de/epic/Main?static=yes&page=abstract&entry_dn=Kar2006d</a>, 2006. Kassens, H. and Dmitrenko, I. A.: The TRANSDRIFT II expedition to the Laptev Sea, Rep. Polar Res., 182, 1–180, 1995. Kassens, H. and Volkmann-Lark, K.: Eurasische Schelfmeere im Umbruch Ozeanische Fronten und Polynjasysteme in der Laptev-See, 2010. Krumpen, T., Janout, M., Hodges, K. I., Gerdes, R., Girard-Ardhuin, F., Hölemann, J. A., and Willmes, S.: Variability and trends in Laptev Sea ice outflow between 1992–2011, The Cryosphere, 7, 349–363, <a href="http://dx.doi.org/10.5194/tc-7-349-2013">https://doi.org/10.5194/tc-7-349-2013</a>, 2013. Macdonald, W., Paton, D., Carmack, E., and Omstedt, A.: The freshwater budget and under-ice spreading of Mackenzie River water in the Canadian Beauford Sea based on salinity and <sup>18</sup>O/<sup>16</sup>O measurements in water and ice, J. Geophys. Res.-Oceans, 100, 895–919, 1995. Newton, R., Schlosser, P., Martinson, D. G., and Maslowski, W.: Freshwater distribution in the Arctic Ocean: Simulation with a high resolution model and model-data comparison, J. Geophys. Res.-Oceans, 113, C05024, <a href="http://dx.doi.org/10.1029/2007JC004111">https://doi.org/10.1029/2007JC004111</a>, 2008. Newton, R., Schlosser, P., Mortlock, R., Swift, J., and MacDonald, R.: Canadian Basin freshwater sources and changes: Results from the 2005 Arctic Ocean Section, J. Geophys. Res.-Oceans, 118, 2133–2154, <a href="http://dx.doi.org/10.1002/jgrc.20101">https://doi.org/10.1002/jgrc.20101</a>, 2013. Nitishinsky, M., Anderson, L. G., and Hölemann, J. A.: Inorganic carbon and nutrient fluxes on the Arctic Shelf, Cont. Shelf Res., 27, 1584–1599, <a href="http://dx.doi.org/10.1016/j.csr.2007.01.019">https://doi.org/10.1016/j.csr.2007.01.019</a>, 2007. Östlund, H. and Hut, G.: Arctic Ocean water mass balance from isotope data, J. Geophys. Res.-Oceans, 89, 6373–6381, 1984. Overland, J. E. and Wang, M.: When will the summer arctic be nearly sea ice free? Geophys. Res. Lett., 40, 1–5, <a href="http://dx.doi.org/10.1002/grl.50316">https://doi.org/10.1002/grl.50316</a>, 2013. Pivovarov, S. V., Hölemann, J. A., Kassens, H., Piepenburg, D., and Schmidt, M. K.: Laptev and East Siberian Seas, in: The Sea, edited by: Robinson, R. A. and Brink, K. H., 14, 1107–1133, Harvard University Press, 2004. Rudels, B.: Atlantic sources of the Arctic Ocean surface and halocline waters, Polar Res., 23, 181–208, 2004. Rudels, B., Anderson, L. G., and Jones, E. P.: Formation and evolution of the surface mixed layer and halocline of the Arctic Ocean, J. Geophys. Res.-Oceans, 101, 8807–8821, <a href="http://dx.doi.org/10.1029/96JC00143">https://doi.org/10.1029/96JC00143</a>, 1996. Santschi, P., Höhener, P., Benoit, G., and Buchholtz-ten Brink, M.: Chemical processes at the sediment-water interface, Marine Chem., 30, 269–315, <a href="http://dx.doi.org/10.1016/0304-4203(90)90076-O">https://doi.org/10.1016/0304-4203(90)90076-O</a>, 1990. Schauer, U.: The expedition ARKTIS-XXII/2 of the research vessel "Polarstern" in 2007, Alfred-Wegener Institute for Polar and Marine Research, Bremerhaven, 2008. Schlitzer, R.: Ocean Data View, available at: <a href="http://www.awi-bremerhaven.de/GEO/ODV">http://www.awi-bremerhaven.de/GEO/ODV</a>, 2001. Spreen, G., Kaleschke, L., and Heygster, G.: Sea ice remote sensing using AMSR-E 89-GHz channels, J. Geophys. Res.-Oceans, 113, C02S03, <a href="http://dx.doi.org/10.1029/2005JC003384">https://doi.org/10.1029/2005JC003384</a>, 2008. Steele, M. and Boyd, T.: Retreat of the cold halocline layer in the Arctic Ocean, J. Geophys. Res.-Oceans, 103, 10419–10435, 1998. Tanaka, T., Guo, L., Deal, C., Tanaka, N., Whitledge, T., and Murata, A.: N deficiency in a well-oxygenated cold bottom water over the Bering Sea shelf: influence of sedimentary denitrification, Cont. Shelf Res., 24, 1271–1283, <a href="http://dx.doi.org/10.1016/j.csr.2004.04.004">https://doi.org/10.1016/j.csr.2004.04.004</a>, 2004. US Environmental Protection Agency: Methods of chemical analysis of water and wastes, Cincinnati, Ohio, EPA 600/4-79/020, p. 460, 1983. Wegner, C., Bauch, D., Hölemann, J. A., Janout, M. A., Heim, B., Novikhin, A., Kassens, H., and Timokhov, L.: Interannual variability of surface and bottom sediment transport on the Laptev Sea shelf during summer, Biogeosciences, 10, 1117–1129, <a href="http://dx.doi.org/10.5194/bg-10-1117-2013">https://doi.org/10.5194/bg-10-1117-2013</a>, 2013. Wessel, P. and Smith, W. H. F.: New improved version of the Generic Mapping Tools released, EOS Trans. AGU, 79, 579, 1998. Woodgate, R. A., Aagaard, K., Muench, R. D., Gunn, J., Björk, G., Rudels, B., Roach, A. T., and Schauer, U.: The Arctic Ocean Boundary Current along the Eurasian slope and the adjacent Lomonosov Ridge: Water mass properties, transports andtransformations from mooredinstruments, Deep-Sea Res. I, 48, 1757–1792, 2001. Yamamoto-Kawai, M., Carmack, E., and McLaughlin, F.: Nitrogen balance and Arctic throughflow, Nature, 443, 43–43, <a href="http://dx.doi.org/10.1038/443043a">https://doi.org/10.1038/443043a</a>, 2006. Yamamoto-Kawai, M., McLaughlin, F. A., Carmack, E. C., Nishino, S., and Shimada, K.: Freshwater budget of the Canada Basin, Arctic Ocean, from salinity, δ<sup>18</sup>O, and nutrients, J. Geophys. Res.-Oceans, 113, C01007, <a href="http://dx.doi.org/10.1029/2006JC003858">https://doi.org/10.1029/2006JC003858</a>, 2008. Zhang, X., He, J., Zhang, J., Polyakov, I., Gerdes, R., Inoue, J., and Wu, P.: Enhanced poleward moisture transport and amplified northern high-latitude wetting trend, Nature Clim. Change, 3, 47–51, <a href="http://dx.doi.org/10.1038/nclimate1631">https://doi.org/10.1038/nclimate1631</a>, 2013.