Circulation in the vicinity of Mackenzie Canyon from a year-long mooring array

Robert S Pickart1, Peigen Lin1, Francis Wiese2, David B Fissel3, Ed Ross3, Jeremy Kasper4, Frank Bahr1, Daniel J Torres5, Jeff K. O'Brien5, Humfrey Melling6, Keath Borg3 and Rowenna Gryba7, (1)Woods Hole Oceanographic Institution, Woods Hole, MA, United States, (2)Stantec, Environmental Services, Anchorage, AK, United States, (3)ASL Environmental Sciences, Victoria, BC, Canada, (4)University of Alaska Fairbanks, Fairbanks, United States, (5)WHOI, Woods Hole, MA, United States, (6)Inst Ocean Sciences, Sidney, BC, Canada, (7)Stantec Consulting, Burnaby, BC, Canada
Abstract:
Data from a five-mooring array extending from the inner shelf (14 m water depth) to the mid-continental slope (440 m) on the western flank of Mackenzie Canyon (139oW) are analyzed to elucidate the components of the boundary current system and their variability. The array, part of the Marine Arctic Ecosystem Study (MARES), was deployed from October 2016 to September 2017 and included measurements of physical, chemical, and biological variables. Here we focus on physical attributes of the system. Three distinct currents were identified: a westward-flowing, surface-intensified jet on the outer-shelf; a mid-depth intensified shelfbreak jet flowing to the east; and a recirculation at the base of the continental slope. The outer-shelf current transports 0.11 Sv in the mean; it is primarily wind-driven, although the response is modulated by the presence of fast-ice in the winter months. The shelfbreak jet transports 0.034 Sv in the mean, which matches well with the value measured upstream in the Alaskan Beaufort Sea. It is strongest in summer and weakens in winter, at times reversing. The deep recirculation appears to be the result of local dynamics whereby a portion of the westward-flowing southern limb of the Beaufort Gyre is diverted up the western flank of the canyon. This is supported by the fact that the monthly variability of the recirculation is correlated with that of the wind-stress curl in the Canada Basin. The seasonality of the measured water masses is not related to the strength of the flow components. Notably, the presence of meteoric and sea ice melt water is more prevalent in this portion of the Beaufort Sea than farther west in the Alaskan Beaufort Sea boundary current. The nature of the Mackenzie river water signal over the course of the year is addressed.