Multiyear Volume, Liquid Freshwater, and Sea Ice Transports through Davis Strait, 2004-10

摘要

Davis Strait is a primary gateway for freshwater exchange between the Arctic and North Atlantic Oceans including freshwater contributions from west Greenland and Canadian Arctic Archipelago glacial melt. Data from six years (2004-10) of continuous measurements collected by a full-strait moored array and concurrent high-resolution Seaglider surveys are used to estimate volume and liquid freshwater transports through Davis Strait, with respective annual averages of -1.6 ± 0.5 Sverdrups (Sv; 1 Sv = 10~6m~3s~(-1)) and -93 ± 6mSv (negative sign indicates southward transport). Sea ice export contributes an additional -10 ± 1mSv of freshwater transport, estimated using satellite ice area transport and moored upward-looking sonar ice thickness measurements. Interannual and annual variability of the net transports are large, with average annual volume and liquid freshwater transport standard deviations of 0.7 Sv and 17 mSv and with interannual standard deviations of 0.3 Sv and 15 mSv. Moreover, there are no clear trends in the net transports over the 6-yr period. However, salinity in the upper 250 m between Baffin Island and midstrait decreases starting in September 2009 and remains below average through August 2010, but appears to return to normal by the end of 2010. This freshening event, likely caused by changes in arctic freshwater storage, is not apparent in the liquid freshwater transport time series due to a reduction in southward volume transport in 2009-10. Reanalysis of Davis Strait mooring data from the period 1987-90, compared to the 2004-10 measurements, reveals less arctic outflow and warmer, more saline North Atlantic inflow during the most recent period.