Arctic Ocean outflow and glacier–ocean interaction modify water over the Wandel Sea shelf, northeast Greenland

Abstract

Abstract. The first-ever conductivity–temperature–depth (CTD) observations on the Wandel Sea shelf in North Eastern Greenland were collected in April–May 2015. They were complemented by CTD profiles taken along the continental slope during the Norwegian FRAM 2014–15 drift. The CTD profiles are used to reveal the origin of water masses and interactions with ambient water from the continental slope and the outlet glaciers. The subsurface water is associated with the Pacific Water outflow from the Arctic Ocean. The underlying Halocline separates the Pacific Water from a deeper layer of Polar Water that has interacted with the warm Atlantic water outflow through Fram Strait recorded below 140 m. Over the outer shelf, the Halocline shows numerous cold density-compensated intrusions indicating lateral interaction with an ambient Polar Water mass across the continental slope. At the glacier front, colder and turbid water intrusions were observed at the base of the Halocline. In temperature–salinity space, these data follow a mixing line that diverges from ambient water properties and indicates ocean–glacier interaction. Our observations of Pacific Water are set within the context of upstream observations in the Beaufort Sea and downstream observations from the Northeast Water Polynya and clearly show the modification of Pacific water during its advection across the Arctic Ocean. Moreover, ambient water over the Wandel Sea slope shows different thermohaline structures indicating the different origin and pathways of the on-shore and off-shore branches of the Arctic Ocean outflow through western Fram Strait.

Storm-induced water dynamics and thermohaline structure at the tidewater Flade Isblink Glacier outlet to the Wandel Sea (NE Greenland)

“…A general conception about the shelf circulation can be deduced from the analysis of the local thermohaline structure. Dmitrenko et al (2017) reported that the shelf waters of the Wandel Sea during winter are mainly comprised of Pacific water (PcW) in the depth range of 20-70 m and warmer Arctic-derived Atlantic water (ArAW) outflowing the Arctic Ocean via the western Fram Strait at greater depths. Within the cold halostad (the layer of weakly stratified salinity below the surface mixed layer; Shimada et al, 2015), represented by PcW, salinity increased from about 30 to 31.5 and temperature decreased from −1.6 to −1.7 • C (Fig.…”

“…The bottom topography of Wandel Sea adjacent to the northern FIIC glacier outlets is poorly known, with only depth measurements available from the sparse echosounding and CTD pressure records obtained in 2006, respectively (Nørgaard-Pedersen et al, 2008Dmitrenko et al, 2017). The key feature of bottom topography near the FIIC glacier is a submarine glacier valley with depths increasing from ∼ 130 m (2 km east of the mooring position) to more than 180 m measured about 18 km north of the glacier terminus (Fig.…”

“…6c). Dmitrenko et al (2017) attributed the thermohaline intrusions over the outer Wandel Sea shelf to the lateral interaction between the on-shelf warm halocline waters and the off-shelf cold polar water. The reference CTD profiles (ARK 267, 268, and 270, Fig.…”

“…Despite the fact that the Wandel Sea is covered with landfast sea ice almost all year round, the fjords and inner shelf have been mostly ice free in August and early September during the last decade. These near-land open water areas are separated from the deep ocean by a permanent multi-year landfast ice fringe (∼ 3.5 m and thicker; Dmitrenko et al, 2017) between FIIC to the northern tip of Prinsesse Margrethe Island or even right up to the Peary Land coast. This ice fringe remains in place throughout the year and probably traps and accumulates meltwater in the surface layer of the inner part of the Wandel Sea.…”

“…Johnson et al, 2011;Rignot et al, 2010) that might further enhance the freshwater input to the coastal waters (Bartholomaus et al, 2013). Although Dmitrenko et al (2017) demonstrated that frontal interleaving was occurring at the outer Wandel Sea shelf, none of the mentioned mechanisms was carefully considered due to the scarcity of oceanographic observations in the Wandel Sea region.…”