Integrative Observational Platforms, Ocean Physics Dept., Applied Physics Laboratory, University of Washington

Observing array deployed 2004-2009 (and continuing)

The array is deployed across Davis Strait between Baffin Island, Canada and Greenland. The initial array deployment occurred in September 2004. The array was turned in September 2005, October 2006, October 2007, and Septembet 2008. The initial array consisted of moored and bottom mounted elements. In the most recent deployments, all elements have been moved onto moorings to reduce bottom related fouling. Mouse over the symbols in the array map to see what instruments are deployed at each location. In addition to the science measurements (currents, temperature, salinity, ice thickness), we have deployed RAFOS sources and six moored receivers in a variety of geometries to study the propagation of RAFOS signals in ice covered environments. In 2005, 2006, and 2008 the RAFOS sources have also supported glider navigation.

Seagliders have been deployed in Davis Strait in 2005 (SG018), 2006 (SG109 and SG110), 2007 (SG112), and 2008 (SG108 and SG113). As expected at the outset of this effort, the strait has proven to be a difficult environment for gliders due to remoteness and ice. In addition to ice related difficulties, the remoteness of the strait means that even when more typical problems occur in open water, recovery operations are difficult. This was the case with SG018 in 2005 (probable pump failure) and SG112 in 2007 (satellite phone failure).

SG109 made the first successful under ice section across the strait in December 2006. From the ice edge on the eastern side of the strait the vehicle navigated to a waypoint 50 km west under ice and back east again over the course of one week. Unfortunately the vehicle was lost shortly after this achievement. The failure mode is unknown.

SG108 and SG113 were launched in September 2008 during the yearly array servicing cruise. Both functioned successfully to the start of the icing period in mid-November. On November 15, SG108 went under the ice on the eastern side of the strait for the first of two successful cross-strait transects. Due to strong currents along the Baffin slope the glider was pushed south off the line survey line in both cases and had to work its way back to the northeast to the eastern end of the line. The return trip followed the ice edge in some cases and thus the glider was in and out of ice cover during this period. The movie below indicates glider position and ice coverage based on Canadian Ice Service maps beginning November 5 (when the first map for the area was produced) and ending February 25, 2009 when the glider was recovered by the Danish Navy after successfully transiting from the survey region to a recovery point off Nuuk, Greenland. Red positions indicate GPS navigation fixes (and thus periods or dive when there was open water), blue indicates RAFOS acoustic fixes (periods or dive when the glider was under ice and unable to come to the surface) and green are interpolated positions indicating that the glider was under ice and did not have a recent acoustic navigation solution.