Subduction of Pacific Summer Water into sub-surface eddies; coordinated observations from late summer 2018
Jennifer A MacKinnon1, Harper L Simmons2, John T. Hargrove3, Jim Thomson4, Thomas Peacock5, Matthew H Alford6, Marion S Alberty1, Benjamin Iolo Barton7, Samuel Brenner8, Nicole Couto6, Seth L Danielson9, Elizabeth Fine10, Hans Christian Graber11, John Guthrie12, Joanne Hopkins13, Steven R Jayne14, Thilo Klenz15, Craig Lee16, Yueng Djern Lenn17, Drew J. Lucas18, Madison Smith19, Sinhue Torres-Valdes20, Kevin R Wood21 and John Woods22, (1)Scripps Institution of Oceanography, La Jolla, United States, (2)University of Alaska Fairbanks, Fairbanks, United States, (3)University of Miami, Center for Southeastern Tropical Advanced Remote Sensing, Miami, FL, United States, (4)University of Washington, Seattle, United States, (5)Dept of Mech Eng - RM 1-310, Cambridge, United States, (6)Scripps Institution of Oceanography, UC San Diego, La Jolla, United States, (7)University of Western Brittany, Laboratoire d'Océanographie Physique et Spatiale (LOPS), Plouzané, France, (8)Brown University, Department of Earth, Environmental, and Planetary Sciences, Providence, RI, United States, (9)Univ Alaska, Fairbanks, AK, United States, (10)Scripps Institution of Oceanography, La Jolla, CA, United States, (11)University of Miami, Center for Southeastern Tropical Advanced Remote Sensing, Miami, United States, (12)Polar Science Center, APL-UW, Seattle, WA, United States, (13)National Oceanography Centre, Liverpool, United Kingdom, (14)WHOI, Department of Physical Oceanography, Woods Hole, MA, United States, (15)University of Alaska Fairbanks, College of Fisheries and Ocean Sciences, Fairbanks, United States, (16)Univ Washington, Seattle, United States, (17)Bangor University, Wales, School of Ocean Sciences, Menai Bridge, United Kingdom, (18)University of California San Diego, Scripps Institution of Oceanography, La Jolla, United States, (19)Applied Physics Laboratory University of Washington, Seattle, United States, (20)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany, (21)NOAA Pacific Marine Environmental Laboratory, Seattle, WA, United States, (22)U.S. National Ice Center, Washington D.C., DC, United States
Abstract:
Advective heat fluxes in the Pacific Summer Water (PSW) class into the Arctic Ocean have
been steadily increasing. Some of this heat is sequestered through subduction
into
warm intrathermocline eddies and filaments,
which
are becoming a new normal part of the Arctic halocline. These heat reservoirs can lurk for weeks to years, potentially
bringing substantial sub-surface heat into the central gyre that can be, given the right
circumstances,
mixed upwards towards sea ice.
Though evidence of very warm (6+ degrees C) sub-surface eddies
is increasing, their
formation process has not previously
been
documented in
detail.
Here we present a novel suite of observations from the September 2018 ONR-funded Stratified Ocean Dynamics of the Arctic process cruise. Using a combination of ship-board sampling, autonomous instruments and drifter data, we observed a 50-100 meter deep surface intensified jet of warm PSW heading offshore from Barrow Canyon. The meandering warm jet can also be seen clearly in satellite data. In conjunction with meanders of the jet, energetic subduction resulted in the formation of coherent sub-surface eddies with a 7-10 km radius. Upward turbulent heat fluxes of 10-100+ W/m^2 move heat towards the surface, which was anecdotally associated with melting of remnant multi-year sea ice in this vicinity. Implications of both the heat and nutrient transport of subduction events like this for the central basin will be discussed.
