Ocean Science www.ocean-sci.net 1812-0784 1812-0792 5 3 2009 10.5194/os-5-219-2009 http://www.ocean-sci.net/5/219/2009/ http://www.ocean-sci.net/5/219/2009/os-5-219-2009.html http://www.ocean-sci.net/5/219/2009/os-5-219-2009.pdf 219 233 2009-07-07 Freshwater components and transports in the Fram Strait &ndash; recent observations and changes since the late 1990s B. Rabe benjamin.rabe@awi.de U. Schauer A. Mackensen M. Karcher E. Hansen A. Beszczynska-Möller Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany Norwegian Polar Institute, Tromsoe, Norway We present the late summer distribution and transports of freshwater components in the upper western part of the Fram Strait during 1998, 2004 and 2005. Hydrographic data and and water &delta;¹⁸O values are analyzed to distinguish Atlantic Water, ice melt (SIM) and freshwater removal from ice formation (IFB), and Meteoric Water (precipitation and riverine sources; MW). Concentrations of these water masses are combined with volume transport estimates from an inverse model. The average liquid freshwater transport relative to a reference salinity of 34.92, was 2500 km³/yr or 80 mSv southward, which is at the upper end of values reported in the literature. Our results indicate that not only the region of the continental slope but also parts of the East Greenland Shelf are important for freshwater transports. <br><br> We estimate the average transports of of MW and IFB to be between 130 to 160 mSv (4100 to 5000 km³/yr) and 60 to 90 mSv (1900 to 2800 km³/yr) southward, respectively. The southward transport of MW was higher in 2005 than in 1998, but was compensated by a higher IFB transport. These differences in transports were associated with stronger southward velocities and the absence of northward velocities over the continental slope and the eastern East Greenland Shelf in 2005. A simulation using the North Atlantic-Arctic Ocean Sea Ice Model (NAOSIM) shows that the high transport of MW in the Fram Strait in 2005 is in agreement with the temporary storage of river water on the Siberian shelf in the mid-1990s, which reached the north of Greenland in 2003. Our results indicate that the accumulation of increased amounts of river water on the shelves is associated with enhanced ice formation. Aagaard, K. and Carmack, E C.: The role of sea ice and other fresh water in the Arctic circulation, J. Geophys. Res., 94, 14485–14498, 1989. Anderson, L G., Jutterström, S., Kaltin, S., Jones, E P., and Björk, G.: Variability in river runoff distribution in the Eurasian Basin of the Arctic Ocean, J. Geophys. Res., 109, C01016, \doi10.1029/2003JC001773, 2004. Bauch, D., Schlosser, P., and Fairbanks, R G.: Freshwater balance and the sources of deep and bottom waters in the Arctic Ocean inferred from the distribution of $H_2^18O$, Progress Oceanogr., 35, 53–80, 1995. Bauch, D., Erlenkeuser, H., and Andersen, N.: Water mass processes on Arctic shelves as revealed from $\delta_18$O of $H_2$O, Global Planet. Change, 48, 165–174, 2005. Behrendt, A.: Comparison of the Current Field in Fram Strait derived from ADCP Measurements and Mooring Data, Master's thesis, University of Bremen, 2008. Bourke, R H., Newton, J L., Paquette, R G., and Tunnicliffe, M D.: Circulation and water masses of the East Greenland Shelf, J. Geophys. Res., 92, 6729–6740, 1987. Brauch, J P. and Gerdes, R.: Reaction of the northern North Atlantic and Arctic oceans to a sudden change of the NAO, J. Geophys. Res., 110, C11018, \doi10.1029/2004JC002436, 2005. Budéus, G., Schneider, W., and Kattner, G.: Distribution and exchange of water masses in the Northeast Water Polynya (Greenland Sea), 10, 123–138, 1997. de Steur, L., Hansen, E., Gerdes, R., Karcher, M., Fahrbach, E., and Holfort J.: Freshwater fluxes in the East Greenland Current: a decade of observations, in preparation, 2009. Dickson, R., Rudels, B., Dye, S., Karcher, M., Meincke, J., and Yashayaev, I.: Current estimates of freshwater flux through Arctic and subarctic seas, Progress in Oceanography, 73, 210–230, \doi10.1016/j.pocean.2006.12.003, 2007. Dodd, P.: Freshwater Transport in the East Greenland Current, Ph.D. thesis, University of East Anglia, 2008. Dodd, P., Heywood, K J., Meredith, M P., Naveira~Garabato, A C., Marca, A D., and Falkner, K K.: The Sources and Fate of Freshwater Exported in the East Greenland Current, Geophys. Res. Lett., in review, 2009. Eicken, H.: Factors determining microstructure, salinity and stable-isotope composition of Antarctic sea ice: deriving modes and rates of ice growth in the Weddell Sea, in: Antarctic sea ice physical processes, edited by: Jeffries, M O., vol 74 of AGU Antarct. Re. Ser., 89–122, 1998. Eicken, H., Kolatschek, J., Freitag, J., Lindemann, F., and Kassens, H.: A key source area and constraints on entrainment for basin-scale sediment transport by Arctic sea ice, Geophys. Res. Lett., 27, 1919–1922, 2000. Eicken, H., Dmitrenko, I., Tyshko, K., Darovskikh, A., Wierking, W., Lahak, U., Groves, J., and Kassens, H.: Zonation of the Laptev Sea landfast ice cover and its importance in a frozen estuary, Global Planet. Change, 48, 55–83, 2005. Ekwurzel, B., Schlosser, P., Mortlock, R A., and Fairbanks, R G.: River runoff, sea ice meltwater, and Pacific water distribution and mean residence times in the Arctic Ocean, J. Geophys. Res., 106, 9075–9092, 2001. Fahrbach, E., Meincke, J., Østerhus, S., Rohardt, G., Schauer, U., Tverberg, V., and Verduin, J.: Direct measurements of volume transports through Fram Strait, Polar Res., 20, 217–224, 2001. Fahrbach, E., Rohardt, G., and Sieger, R.: 25 Years of Polarstern Hydrography (1982–2007), 5, Alfred Wegener Institute for Polar and Marine Research: Bremerhaven, \doi10013/epic.30213.d001, 2007. Falck, E., Kattner, G., and Budèus, G.: Disappearance of Pacific Water in the northwestern Fram Strait, Geophys. Res. Lett., 32, L14619, \doi10.1029/2005GL023400, 2005. Foldvik, A., Aagaard, K., and Tørresen, T.: On the velocity field of the East Greenland Current, Deep-Sear Res., 35, 1335–1354, 1988. Gerdes, R., Karcher, M., Köberle, C., and Fieg, K.: Simulating the long term variability of liquid freshwater export from the Arctic Ocean, in: Arctic-Subarctic Ocean Fluxes: Defining the role of the Northern Seas in climate, edited by: Dickson, R R., Meincke, J., and Rhines, P., chap 17, 405–425, Springer Science and Business Media, 2008. Guay, C. K H., 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. Haak, H., Jungclaus, U., Mikolajewicz, U., and Latif, M.: Formation and propagation of great salinity anomalies, Geophys. Res. Lett., 30, 1473, \doi10.1029/2003GL01765, 2003. Häkkinen, S.: A simulation of the thermohaline effects of a great salinity anomaly, J. Climate, 12, 1781–1795, 1999. Häkkinen, S. and Proshutinsky, A.: Freshwater content variability in the Arctic Ocean, J. Geophys. Res., 109, C03051, \doi10.1029/2003JC001940, 2004. Holfort, J., Hansen, E., Østerhus, S., Dye, S., Jonsson, S., Meincke, J., Mortensen, J., and Meredith, M.: Freshwater fluxes east of Greenland, in: Arctic-Subarctic Ocean Fluxes: Defining the role of the Northern Seas in climate, edited by Dickson, R R., Meincke, J., and Rhines, P., chap 11, 263–287, Springer Science and Business Media, 2008. Jakobsson, M., Macnab, R., Mayer, M., Anderson, R., Edwards, M., Hatzky, J., Schenke, H.-W., and Johnson, P.: An improved bathymetric portrayal of the Arctic Ocean: Implications for ocean modeling and geological, geophysical and oceanographic analyses, Geophys. Res. Lett., 35, L07602, doi:10.1029/2008GL033520, 2008. Jones, E P., Anderson, L G., Jutterström, S., Mintrop, L., and Swift, J H.: Pacific fresh water, river water and sea ice meltwater across Arctic Ocean basins: Results from the 2005 Beringia Expedition, J. Geophys. Res., 113, C08012, \doi10.1029/2007JC004124, 2008a. Jones, E P., Anderson, L G., Jutterström, S., and Swift, J H.: Sources and distribution of freshwater in the East Greenland Current, Progress in Oceanography, 78, 37–44, \doi10.1016/j.pocean.2007.06.003, 2008b. Karcher, M., Gerdes, R., Kauker, F., Köberle, C., and Yashayaev, I.: Arctic Ocean change heralds North Atlantic freshening, Geophys. Res. Lett., 32, L21606, \doi10.1029/2005GL023861, 2005. Karcher, M., Gerdes, R., and Kauker, F.: Modeling of $\delta_18$O and $_99$Tc dispersion in Arctic and subarctic seas, ASOF Newsletter, 5, available from: http://asof.npolar.no, 2006. Kiilerich, A.: On the hydrography of the Greenland Sea, Medd. Groenl., 144, 1–63, 1945. Köberle, C. and Gerdes, R.: Simulated variability of the Arctic Ocean fresh water balance 1948-2001, J. Phys. Oceanogr., 37, 1628–1644, \doi10.1175/JPO03063.1, 2007. Losch, M., Sidorenko, D., and Beszczynska-Möller, A.: FEMSECT: An inverse section model based on the finite element method, J. Geophys. Res., 110, C12023, \doi10.1029/2005JC002910, 2005. Mackensen, A.: Oxygen and carbon stable isotope tracers of Weddell Sea water masses: new data and some paleoceanographic implications, Deep-Sea Res. I, 48, 1401–1422, 2001. Majoube, M.: Fractionation factor of $^18O$ between water vapor and ice, Nature, 226, 1242, \doi10.1038/2261242a0, 1970. Manley, T O.: Branching of Atlantic Water within the Greenland-Spitsbergen Passage: An estimate of recirculation, J. Geophys. Res., 100, 20627–20634, 1995. Melling, H. and Moore, R M.: Modification of halocline source waters during freezing on the Beaufort Sea shelf: evidence from oxygen isotopes and dissolved nutrients, Cont. Shelf. Res., 15, 89–113, 1995. Meredith, M., Heywood, K., Dennis, P., Goldson, L., White, R., Fahrbach, E., Schauer, U., and Østerhus, S.: Freshwater fluxes through the western Fram Strait, Geophys. Res. Lett., 28, 1615–1618, 2001. Morrison, J., Steele, M., Kikuchi, T., Falkner, K., and Smethie, W.: Relaxation of central Arctic Ocean hydrography to pre-1990s climatology, Geophys. Res. Lett., 33, L17604, \doi10.1029/2006GL026826, 2006. Nilsson, J., Björk, G., Rudels, B., Winsor, P., and Torres, D.: Liquid freshwater transport and Polar Surface Water characteristics in the East Greenland Current during the AO-O2 Oden expedition, Progress Oceanogr., 78, \doi10.1016/j.pocean.2007.06.002, 2008. O'Neil, J R.: Hydrogen and oxygen isotope fractionation between icena and water, J. Phys. Chem., 72, 3683–3684, 1968. Østlund, H G. and Hut, G.: Arctic Ocean water mass balance from isotope data, J. Geophys. Res., 89, 6373–6381, 1984. Padman, L. and Erofeeva, S.: A barotropic inverse tidal model for the Arctic Ocean, Geophys. Res. Lett., 31, L02303, \doi10.1029/2003GL019003, 2004. Rudels, B., Fahrbach, E., Meincke, J., Budèus, G., and Ericksson, P.: The East Greenland Current and its contribution to the Denmark Strait overflow, ICES J. Mar. Sci., 59, 1133–1154, \doi10.1006/jmsc.2002.1284, 2002. Rudels, R., Jones, E P., Schauer, U., and Ericksson, P.: Atlantic sources of the Arctic Ocean surface and halocline waters, Polar Res., 23, 181–208, 2004. Schauer, U.: The Expedition ARKTIS-XXII/2 of the Research Vessel "Polarstern" in 2007, vol. 579 of \em Reports on polar and marine research\/, Alfred-Wegener Institute for Polar and Marine Research: Bremerhaven, 2008. Schauer, U., Fahrbach, E., Østerhus, S., and Rohardt, G.: Arctic warming through the Fram Strait: Oceanic heat transport from 3 years of measurements, J. Geophys. Res., 109, C06026, \doi10.1029/2003JC001823, 2004. Schlichtholz, P. and Houssais, M.-N.: An overwiew of the θ - S correlations in Fram Strait based on the MIZEX 84 data, Oceanologia, 44, 243–272, 2001. Schlosser, P., Bauch, D., Fairbanks, R G., and Bönisch, G.: Arctic river-runoff: mean residence time on the shelves and in the halocline, Deep-Sea Res., 41, 1054–1068, 1994. Schlosser, P., Ekwurzel, B., Khatiwala, S., Newton, R., Maslowski, W., and Pfirman, S.: Tracer studies of the Arctic freshwater budget, in: Freshwater balance of the Arctic Ocean, edited by: Lewis, E L., NATO, 2000. Schlosser, P., Newton, R., Ekwurzel, B., Khatiwala, S., Mortlock, R., and Fairbanks, R.: Decrease of river runoff in the upper waters of the Eurasian Basin, Arctic Ocean, between 1991 and 1996: evidence from $\delta_18$O data, Geophys. Res. Lett., 29, 1289, \doi10.1029/2001GL013135, 2002. Serreze, M C., Barrett, a P., Slater, A G., Woodgate, R., Aagaard, K., Lammers, R B., Steele, M., Moritz, R., Meredith, M., and Less, C M.: The large-scale freshwater cycle of the Arctic, J. Geophys. Res., 111, C11010, \doi10.1029/2005JC003424, 2006. Steele, M., Morison, J., Ermold, W., Rigor, I., Ortmeyer, M., and Shimada, K.: Circulation of summer Pacific halocline water in the Arctic Ocean, J. Geophys. Res., 109, C02027, \doidoi10.1029/2003JC002009, 2004. Taylor, J R., Falkner, K K., Schauer, U., and Meredith, M.: Quantitative considerations of dissolved barium as a tracer in the Arctic Ocean, J. Geophys. Res., 108, 3374, \doi10.1029/2002JC001635, 2003. Yamamoto-Kawai, M., McLaughlin, F A., Carmack, E C., Nishino, S., and Shimada, K.: Freshwater budget of the Canada Basin, Arctic Ocean, from salinity, $\delta_18O$, and nutrients, J. Geophys. Res., 113, C01007, \doi10.1029/2006JC003858, 2008.