deployment plan for glider

STATUS

An important task of MERSEA WP3 is the assessment of available long-range glider technologies which meet MERSEA requirements (reliability, long range/endurance at sea, and the possibility to carry bio-geochemical sensors). Three partners in this workpackage are acquiring gliders and expertise in operating them, to demonstrate glider technology capabilities including real-time transmission, quality control, and integration and feeding to the MERSEA data server.  Training and in-lab testing, as well as field mission program design will be performed followed by field trials in deep and coastal environments. Glider usage will be optimized against moored instruments (time-series sites) in the Mediterranean Sea and Atlantic Ocean.  

A: Deep Mediterranean deployments  

Several gliders have been deployed in the western Mediterranean Sea in the framework of the MERSEA project between mid January and mid June.  Thanks to coordinated efforts and great support of local institutions as well as the Spanish Rescue Service and the French Navy, a fleet of, gliders could continuously operate in the area. MERSEA funded gliders
Maya (IMEDEA), Spray016 (SIO, IFM-GEOMAR, LPO, LOCEAN), and Potame (LPO) have been working together with other gliders Ammonite, Bellamite, Coprolite (NOCS), and Pytheas (LOCEAN) in order to  sample thoroughly the northwestern Mediterranean Sea.

Around 1500 deep casts (down to ~1000m depth) and 1700 shallow casts (down to ~200m depth) have been carried out by these autonomous platforms. All the Temperature and Salinty data was transmitted in real time to the Coriolis data center (Figure 1), quality-controlled, distributed, and assimilated by operational models. Biogeochemical data was also collected and distributed, since some gliders were equipped with additional sensors of Oxygen (Potame, Pytheas), Fluorescence (Spray016, Pytheas), and Turbidity (Pytheas).

 

Figure 1: a) MFSTEP Glider deployment operations on board of the coastal vessel IMEDEA 1, offshore the northwestern coast 
of Mallorca Island. b) MFSTEP glider at sea just before starting her operation.  

In Yellow the Glider missions begining of 2007

I

B: Coastal Mediterranean deployments

Calibration of ENVISAT altimetry with in situ data gathered from a glider

The main goal of this operation is to cover part of an ENVISAT trajectory with a glider, simultaneously with the pass of the satellite. Specifically, the satellite passed  through the transect marked with red line in Figure 4 on Sunday July 8th, 2007 at 20:00 pm. A glider was deployed on Friday July 7th, 2007 to cover the satellite transect providing a section of the density field. The operation was supported by in situ CTD casts (circles) from the oceanographic ship García del Cid. The mission concluded on July 13th, 2007. Glider data have been employed together with CTD casts to calibrate altimetry from satellite in coastal region  See results

Sustained and continuous glider observations of the channels in the Balearic Sea

Two gliders will cover the open boundaries of the Balearic Sea during September to December 2007, Figure 5. The first glider will cover the southwards part of the region, providing data from the channels of Mallorca and Ibiza. A second glider will carry out a transect between the western coast of Mallorca and mainland. Data will provide information about the geostrophic transport of inflows and outflows.

 
Figure 4. CTD casts (circles) and glider transect (red line). The transect carried out by the glider exactly corresponds to the pass of the ENVISAT satellite on July 8th

Figure 5: Sections carried out by the gliders  in the Balearic Sea

C: Atlantic Ocean deployments

The Spray 04 (figure 6), an open-ocean deep glider rented from Scripps Institution of Oceanography (San Diego), performed 2 successful missions in the North Atlantic in 2005-2006. This glider provided profiles of temperature, conductivity (salinity) and fluorescence (chlorophyll-a) between the surface and 1000m (or less) at a 1-meter vertical resolution. The spacing between the slanted profiles is proportional to the chosen target depth, typically with a factor of 6 for regions with weak/no oceanic currents.

The first experiment, called PAP-1, occurred from December 4, 2005 to March 12, 2006. The glider performed 473 dives along the Armorican Shelf and near the PAP mooring at 49°N 16°W (figure 6) to survey the spatial variability around that mooring. It appeared later that the mooring data could not be recovered for this study since the observatory was nearly totally destroyed by fishing activities. As an unexpected consequence, the glider data help to fill the gap of the PAP observatory time series.

The second experiment, called CIS-1, occurred from June 17, 2006 to August 24, 2006. The glider performed 310 dives across the Irminger Basin and around the CIS mooring (figure 7). A special care was taken to calibrate the data of CIS-1 mission with CTD (for T and S) + bottle sampling (for S and chlor-a) at deployment and recovery. The CIS mooring was maintained a few days after the glider recovery, and mooring and glider datasets are currently processed.

Both experiments went very smoothly, cumulating a 4118-km trip on 5.5 months. In November 2006, Spray 04 was deployed again for the PAP-2 experiment. Unfortunately, the instrument was lost, due to the conjunction of a mechanical failure and quite tough weather conditions. Spray16, which was successfully tested in the Mediterranean Sea until April 2007, is now ready for another Atlantic deployment.

All the data was transmitted in real time to the Coriolis data center, where they are collected, controlled and distributed in real-time for scientific or operational experiences. A specific Coriolis glider page was built, were data of all the MFSTEP and MERSEA experiments can be downloaded and visualized.

Figure 6: Spray-04

Figure 7: Glider trajectory of the PAP-1 and CIS-1 experiments, on top of climatological MODIS SST