Oceanic freshwater and heat exchange between the Arctic and North Atlantic provide critical mechanisms through which the Arctic and global climate interact. Arctic freshwater, from riverine input and melting sea ice, flows southward through the Arctic ?Gateways? to the west (Davis Strait) and east (Fram Strait) of Greenland into the regions of the subpolar North Atlantic where the waters that occupy the deep ocean interior are formed. At these sites, strong wintertime storms cool the upper ocean, making these waters dense enough to cause them to sink to depth, effectively communicating this atmospheric forcing into the ocean interior and driving the equator-to-pole transport of heat. Fresh, buoyant Arctic outflow reduces the density of surface waters in these deepwater formation regions, and thus has the potential to slow the sinking and modulate equator-to-pole heat transport. Changes in Arctic outflow also impact broad North Atlantic circulation patterns and circulation off the Labrador coast, with wide-ranging impacts to ecosystems. Conversely, the northward flow of relatively warm Atlantic waters can supply oceanic heat to melt Greenlandic glaciers where they encounter the ocean, thus accelerating the melting of Greenland ice cap. Uncertainty surrounding the role of oceanic heat in accelerating the melt of Greenland?s glaciers is one of the largest sources of uncertainty in numerical predictions of future sea level rise. The critical role of Arctic-subpolar heat and freshwater exchange motivates renewed efforts to maintain sustained, persistent, measurements across Davis Strait, capturing exchange between the Arctic and subpolar North Atlantic (Labrador Sea) at a choke point at the southern end of Baffin Bay.
This project will renew the integrated observational program at Davis Strait, delivering data to the community and matching ongoing collections at Bering Strait, Utqiagvik, Alaska, and Fram Strait to extend the time series of concurrent measurements across the major Arctic Gateways. The extended timeseries will document changes in freshwater and heat fluxes, and will be combined with numerical modeling to investigate the processes that control variability in the strait and the potential impacts. The backbone system relies on the tested combination of moorings instrumented with sensors to measure ice thickness and motion, ocean currents, temperature and salinity, and biennial ship-based sampling of chemical and biological properties that have successfully delivered core measurements for the past decade. Bottom pressure sensors augment the system to quantify sea surface height gradients, which will support investigations of the primary forcing mechanisms. Integrated marine ecosystem observing includes biogeochemical and marine mammal passive acoustic measurements augmented with tracking of key fish species, and zooplankton and phytoplankton observations. These observations will launch the Davis Strait/Baffin Bay Distributed Biological Observatory (DBO) in Davis Strait, complementing the developing Atlantic DBO that includes transect lines in Fram Strait and Barents Sea, and the existing Pacific DBO in the northern Bering, Chukchi and Beaufort Seas.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
