Physical forcings and intense shelf–slope fluxes of particulate matter in the halocline waters of the Canadian Beaufort Sea during winter

Current surges and seabed erosion near the shelf break in the Canadian Beaufort Sea: A response to wind and ice motion stress

“…Mean current patterns vary markedly over the slope as water depth and distance from the shelf break increase. The mean subsurface current pattern near the shelf break (50-200 m) reflects the propagation of an eastward shelfbreak jet in the Canadian Beaufort Sea (Forest et al, 2015;Dmitrenko et al, 2016) as observed in the Alaskan Beaufort Sea (Pickart, 2004;Nikolopoulos et al, 2009;von Appen and Pickart, 2012). This current can be defined as a narrow flow (10-15 km width) trapped to the shelf break near 100 m and transporting~20% of the Pacific water entering the Bering Strait and directed eastward.…”

“…1) can be characterized as a bottom-intensified jet carrying Pacific Winter Water (salinity~33) with mean velocities of 15 cm s -1 (Spall et al, 2008;von Appen and Pickart, 2012). At 20-30 km from the shelf break, the eastward shelfbreak jet is no longer present and the mean current vectors in the upper 200 m are progressively directed to the west in the opposite direction than near the shelf edge (Forest et al, 2015). Strong easterly winds that enhance the anticyclonic motion of the Beaufort Gyre and generate coastal upwelling Tremblay et al, 2011) are known to be able to reverse the shelfbreak jet resulting in an intense flow to the west (up to 1 m s -1 ) in the Alaskan Beaufort Sea (Pickart et al, 2011(Pickart et al, , 2013.…”

“…Ocean currents in the upper 50 m of the water column in the southeastern Beaufort Sea are typically directed to the west following the anti-cyclonic motion of the Beaufort Gyre Forest et al, 2015). The water mass that occupies this interval is the Polar mixed-layer with salinity~30-31 (practical scale, as throughout this study), which is largely influenced by seasonality, river inputs and ice growth/melt cycles.…”

“…The latter particles represent in fact the oldest suspended matter 14 C values out of a large radiocarbon database covering all Earth's oceans , which suggests active transport of resuspended material from the shelf to the basin in the Arctic Ocean (see also the review of Macdonald et al, 2015). Recent particle flux measurements by epipelagic sediment traps moored in the Canadian Beaufort Sea demonstrate that intense events of shelf-slope sediment transport recurrently occur near the bottom across the shelf break and in the mid-water column over the slope (Forest et al, 2007(Forest et al, , 2015. These events appear to be driven by downwelling-favorable wind storms and the cascading flow of dense winter water down the shelf, which both represent mechanisms able to entrain material from the shelf BBL toward the margin and beyond.…”

“…The resuspension, entrainment and seaward advection of shelf bottom material is increasingly recognized as an important component of particulate matter cycling in the Arctic Ocean system (Forest et al, 2007(Forest et al, , 2015Hwang et al, 2008;Honjo et al, 2010;Macdonald et al, 2015;Magen et al, 2010;Mucci et al, 2008;Smith, 2010;O'Brien et al, 2011O'Brien et al, , 2013Watanabe et al, 2014). This is partly due to the inherent characteristics of this ocean, which is comprised of 36% of shallow shelves less than 200 m (~20 % of the world's continental shelf) and is pervasively influenced by large riverine sediment outputs, accelerating permafrost thawing, and coastal erosion (Macdonald et al, 1998;Stein and Macdonald, 2004;Smith, 2010).…”