Demonstration of Spray Ocean Gliders for Basin Scale Climate Monitoring: Greenland to the Iberian Peninsula Sections
OCCI Funded Project: 2005 and 2006
Proposed ResearchThis grant is intended to test the ability of spray ocean gliders to make long-range ocean sections across ocean basins for use in monitoring the major parts of the meridional overturning circulation. To this end, we had planned to make two sections from the east coast of Greenland to Vigo, Spain. These sections are planned to repeat one of the CLIVAR repeat sections that are occupied on an approximate 2-year repeat schedule. The glider sections were to be made in the early summer and mid-Fall to examine two different seasons. The glider sections would sample the upper 1 kilometer of the ocean. Variations between the glider and shipboard measurements will be used to characterize the variability in the transports of mass, heat, and fresh water. Two cruises on European research ships were identified and arrangements were made to deploy the glider in June 2006 and September 2006.
The June 2006 deployment was organized with INFREMER scientists as part of their OVIDE project that supports the CLIVAR repeat section between Greenland and the Iberian Peninsula. The Principle Investigator for the cruise was Pascale Lherminier. The cruise plan is shown in Figure 1. This cruise was on the R.V. Maria S. Merian, a new German research ship departing Lisbon, Portugal. In addition to making the CLIVAR repeat section, they were also going to launch their own spray glider to make repeated sections across the East Greenland Boundary Current. We were able to take delivery of a new spray glider that was purchased through Bluefin, Inc. The glider was delivered to WHOI with only a few weeks to prepare it for sea, but Brian Guest was able to prepare the glider and have it delivered to Lisbon, Portugal in time for the cruise. Owens went to Lisbon and working with Thierry Terre who was the engineer in charge of the INFREMER spray glider the glider was prepared for deployment. There appear to be some irregularities with the glider flux-gate compass, but eventually it seemed to work. Fortunately, during the cruise, the technician in charge of the gliders sent an incorrect command to our glider that erased the compass calibration data. Despite heroic attempts on their part, they were unable to get the compass to recalibrate. The glider was eventually shipped back to WHOI. During testing at WHOI, it was determined that the flux-gate compass had failed and it was probably fortuitous that it was not deployed. The compass was replaced and the glider prepared for sea. More careful checks of the compass are now routinely carried out before deployment.
A second cruise on the R.V. Discovery to the region to the east coast of Greenland was carried out in September-October 2006, lead by Detlef Quadfasel with Peter Winsor from WHOI as part of the scientific party. Winsor was trained in the deployment of the glider and Guest went to Reykjavik to prepare the glider for deployment. The glider was successfully deployed off Greenland. However, a few hours after deployment it was discovered that the glider was aborting every two hours. We determined that the watchdog timer that aborts the glider if the glider computer fails was not being properly reset. We were eventually able to program the glider to make two dives to a little more than 100 m depth before it would abort. Software was written at WHOI to automatically send resets to the glider every two hours and the glider was diverted to Iceland. Through colleagues in Iceland, we were able to arrange for the recovery of the glider offshore of Vestmannaeyjar, Iceland that are small volcanic islands off the south coast of Iceland where there is a small marine research facility. After nearly 3 months, the glider successfully navigated to Vestmannaeyjar (Figure 2). Owens and Ben Carr were able to carry out a successful recovery of the glider on 6, December. The glider is now in shipment back to WHOI.
We are now investigating other deployment opportunities for 2007 and hope to carry out the planned deployments next year. We have also been working closely with Jeff Sherman of the Scripps Institution of Oceanography who is the designer of the Spray glider to modify the standard preparation procedures to identify the problems that we encountered during the last year. All though these problems were unfortunate, they are part of the normal process of bringing a new vehicle into service.