Research papers On the waters upstream of Nares Strait, Arctic Ocean, from 1991 to 2012 Jennifer M. Jackson a,n , Camille Lique b,1 , Matthew Alkire a , Michael Steele a , Craig M. Lee a , William M. Smethie c , Peter Schlosser c a Applied Physics Laboratory, University of Washington, Seattle, WA, USA b Joint Institute for the Study of the Atmosphere and Ocean, University of Washington, Seattle, WA, USA c Lamont-Doherty Earth Observatory, Earth Institute at Columbia University, Palisades, NY, USA article info Article history: Received 6 June 2013 Received in revised form 29 October 2013 Accepted 28 November 2013 Available online 6 December 2013 Keywords: Arctic Ocean Lincoln Sea Nares Strait Ocean circulation Water mass modification abstract The Lincoln Sea is a bifurcation point, where waters from the Canadian and Eurasian Basins flow to Nares or Fram Strait. Mechanisms that control which waters are found in the Lincoln Sea, and on its continental shelves, are unknown. Using conductivity–temperature–depth (CTD; from hydrographic and ice-tethered profiler surveys), nutrient, and mooring data with the DRAKKAR global 3-D coupled ocean/sea-ice model, the Lincoln Sea was examined from 1991 to 2012. Although both Pacific and Atlantic waters were observed on the North Ellesmere and North Greenland shelves, Atlantic water was shallower on the North Greenland shelf. Thus, deeper than 125 m, water was warmer and saltier on the North Greenland shelf than the North Ellesmere shelf. Three different water types were identified on the North Ellesmere shelf – waters from the Canadian Basin were observed 1992, 1993, 1996, 2005, and 2012, waters from both the Canadian and Eurasian Basins were observed in 2003, 2004, and 2008, and waters with no temperature minima or maxima below the surface mixed layer were observed in 1991, 2006, 2009, and 2010. Mixing with vertical advection speeds of 1  10 4 ms 1 were observed on the continental slope and this mixing could cause the disappearance of the temperature maxima. Model results suggest that currents on the North Ellesmere shelf were weak (less than 10 cm s 1 ), baroclinic, and directed away from Nares Strait while currents on the North Greenland shelf were stronger (less than 15 cm s 1 ), and primarily directed towards Nares Strait. CTD, mooring, and model results suggest that the water advected to Nares Strait is primarily from the North Greenland shelf while water on the North Ellesmere shelf is advected westward. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction Water from the Arctic Ocean flows to the North Atlantic Ocean through Fram Strait and the Canadian Arctic Archipelago (CAA) (Aagaard and Carmack, 1989). The Arctic Ocean is fresher than the North Atlantic, so water exported from the Arctic has the potential to influence the global freshwater cycle (Dickson et al., 1988) and meridional overturning circulation (Dickson et al., 1996; Koenigk et al., 2007; Rennermalm et al., 2007). Nares Strait is one of the two main passages through the CAA and year-round mooring data have estimated that the volume flux through Nares Strait ranges from 0.47 70.05 Sv (Rabe et al., in press) to 0.57 70.09 Sv (Münchow and Melling, 2008), or roughly half of the total CAA transport (McGeehan and Maslowski, 2012). Nares Strait separates northern Ellesmere Island from northern Greenland. At its northern end, Robeson Channel, Nares Strait is about 35 km wide and about 500 m deep (Fig. 1). At the southern end of Nares Strait, about 530 km south of Robeson Channel, Smith Sound separates Nares Strait from Baffin Bay. Nares Strait is covered year- round by sea-ice. Despite its relatively narrow width, the circulation through Nares Strait is complex. Based on a 3-year mooring study across southern Robeson Channel, Rabe et al. (2010) found that flow was strongest on the Ellesmere Island side of Nares Strait, with average speeds of 0.2 m s 1 southward. Circulation varied with sea-ice condi- tions – under mobile ice, a second southward current was often observed in the middle of Robeson Channel while under land-fast ice a single southward current against Ellesmere Island was observed (Rabe et al., in press). It is thought that variability in the southward flow through Nares Strait can be explained by the sea surface height in northern Baffin Bay (Münchow et al., 2006; Houssais and Herbaut, 2011; McGeehan and Maslowski, 2012; Rudels, 2012), wind speed and direction under mobile ice conditions (Samelson et al., 2006; Münchow et al., 2006; Rabe et al., in press), and tides (Münchow and Melling, 2008). Hydrographic data collected in Nares Strait in the 1970s and 1980s showed that all of the water in Robeson Channel was from the Arctic Ocean (Sadler, 1976; Bourke et al., 1989). Both Pacific and Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/csr Continental Shelf Research 0278-4343/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.csr.2013.11.025 n Corresponding author. at: ASL Environmental Sciences Inc., Victoria, British Columbia, Canada. E-mail address: jjackson@aslenv.com (J.M. Jackson). 1 Now at: Department of Earth Sciences, University of Oxford, Oxford, UK. Continental Shelf Research 73 (2014) 83–96