Liquid freshwater transport and Polar Surface Water characteristics in the East Greenland Current during the AO-02 Oden expedition Johan Nilsson a, * , Göran Björk b , Bert Rudels c , Peter Winsor d , Daniel Torres d a Department of Meteorology, Stockholm University, SE-10691 Stockholm, Sweden b Department of Oceanography, Earth Sciences Centre, Göteborg University, Box 460, SE 40530 Göteborg, Sweden c Finnish Institute of Marine Research, Box 2, FI 00561 Helsinki, Finland d Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA article info Article history: Received 11 August 2005 Accepted 26 June 2007 Available online 1 May 2008 Keywords: East Greenland Current Late-winter observations Freshwater transport Polar Surface Water abstract Dynamical features of the East Greenland Current (EGC) are synthesized from a survey conducted by the Swedish icebreaker Oden during the International Arctic Ocean – 02 expedition (AO-02) in May 2002 with emphasis on the liquid freshwater transport and Polar Surface Water. The data include hydrography and lowered acoustic doppler current profiler (LADCP) velocities in eight transects along the EGC, from the Fram Strait in the north to the Denmark Strait in the south. The survey reveals a strong confinement of the low-salinity polar water in the EGC to the continental slope/shelf—a feature of relevance for the stability of the thermohaline circulation in the Arctic Mediterranean. The southward transport of liquid freshwater in the EGC was found to vary considerably between the sections, ranging between 0.01 and 0.1 Sverdrup. Computations based on geostrophic as well as LADCP velocities give a section-averaged southward freshwater transport of 0.06 Sverdrup in the EGC during May 2002. Furthermore, Oden data suggest that the liquid freshwater transport was as large north of the Fram Strait as it was south of the Denmark Strait. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Some 5–8 Sverdrup (Sv; 1 Sv = 1  10 6 m 3 s 1 ) of warm Atlantic water enter the Arctic Mediterranean over the Greenland–Scotland Ridge (Hansen and Østerhus, 2000). As the Atlantic water circu- lates through the Arctic Mediterranean, it loses heat to the atmo- sphere and becomes less saline due to freshwater input. The action of these two transformation processes separates the Atlantic water into two circulation loops (cf. Rudels, 1995; Mauritzen, 1996). The major deep loop is determined mainly by the cooling occurring in the Norwegian Sea and the Barents Sea, which in- creases the density of the Atlantic water. This loop creates the dense deep waters of the Arctic Mediterranean and supplies the overflow water to the North Atlantic. The second weaker surface loop is dominated by the river runoff to and the melting of sea ice in the Arctic Ocean, forming the low salinity, less dense Polar Surface Water. After following several and different circulation paths in the Arctic Mediterranean the waters of the two loops join the East Greenland Current in and north of Fram Strait. The less dense surface loop, augmented with Pacific Water from the Bering Strait (Jones et al., 1998), forms a low-salinity wedge near the coast above the denser water masses of the deep loop. The interaction between the two loops is limited but not absent. Ice formation in lee polynyas on the Arctic Ocean shelves may, through brine rejec- tion, create waters saline and dense enough to supply the deeper loop, and the open ocean convection in the Greenland and Iceland Sea can bring low-salinity surface water, detached from the East Greenland Current, into the deep. The Arctic Mediterranean receives a freshwater input of about 0.28 Sv, which originates from river runoff (0.13 Sv), net precipita- tion (0.06 Sv), and inflow of low-salinity Pacific water through the Bering Strait (0.09 Sv) (see Aagaard and Carmack, 1989; Dickson et al., 2007, and references therein). The freshwater supplied to the Arctic Mediterranean is exported to the North Atlantic west and east of Greenland, through the Canadian Arctic Archipelago and across the Greenland–Scotland Ridge, respectively. The fresh- water transport east of Greenland is about 0.19 Sv of which 0.05 Sv is carried by the dense overflow waters (Dickson et al., 2007). The freshwater in the EGC—should it enter the central Green- land Sea—has the potential to decrease the surface density and thus reduce the convective activity and the associated deep-water production, hereby curtailing or disrupting the thermohaline ex- change over the Greenland–Scotland Ridge (Stigebrandt, 1985). Thus, the transport and horizontal mixing of freshwater in the EGC are important for the operation and stability of the thermoha- line circulation in the Arctic Mediterranean and the Nordic Seas 0079-6611/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.pocean.2007.06.002 * Corresponding author. Tel.: +46 8161736. E-mail address: nilsson@misu.su.se (J. Nilsson). Progress in Oceanography 78 (2008) 45–57 Contents lists available at ScienceDirect Progress in Oceanography journal homepage: www.elsevier.com/locate/pocean