SPURS-MIDAS Cruise Plan v3
The SPURS-MIDAS cruise (Las Palmas de Gran Canaria 16 March 2013 – Ponta Delgada, Açores 13 April) on board the Spanish R/V Sarmiento de Gamboa is a contribution to the SPURS experiment (Salinity Processes in the Upper ocean Regional Study, http://spurs.jpl. nasa.gov/SPURS/) aimed at understanding the processes that drive the upper ocean dynamics and the role that salinity plays on them in the area of maximum salinity in the center of the North Atlantic subtropical gyre. The experiment is coordinated by WHOI (R. Schmitt) and sponsored by NASA (E. Lindstrom), and includes intensive field work with a large variety of state-of-the-art instrumentation, the use of satellite remotely sensed salinity information (Aquarius and SMOS), as well as dedicated numerical modeling.
The cruise is a component of the ICM-CSIC subproject of the MIDAS-6 project (SMOS ocean salinity and soil moisture products. Improvements and applications demonstration) funded by the Spanish R+D National Plan (grant AYA2010-22062-C05, PI J. Font) that encompasses also processing and mapping SMOS salinity data as well as numerical modeling work.
The Sarmiento will be in the SPURS site together with the US R/V Endeavor in a coordinated program to continue the SPURS field work initiated by the French R/V Thalassa (STRASSE cruise, August-September 2012) and US R/V Knorr (September-October 2012). The main role of our cruise is to run first a general survey for mesoscale mapping of the area by means of TSG, ADCP and undulating CTD (SeaSoar), and on the same time to deploy a total of 48 surface salinity drifters in a 15 nm grid around WHOI mooring. After this initial survey the Sarmiento will participate in submesoscale high resolution specific samplings, as well as performing turbulence (ASIP profiler) and other mixed-layer measurements. Additional opportunity measurements will be done to collect water and plankton samples for objectives from Spanish researchers not belonging to the MIDAS team (ICM, U. Vigo, U. Autònoma Barcelona). We may also pick-up a Mixed Layer Float (MLF) from U. Washington drifting in the area.
The cruise plan can be drafted as follows:
March 8: Equipment loaded in Vigo (NW Spain mainland)
March 10 or 11: Sarmiento de Gamboa leaves Vigo to Las Palmas
March 16 (approx. 18h GMT): Sarmiento leaves Las Palmas (28N, 15.3W) steaming at 10 knt heading 25.25N, 36.5W. Nighttime plankton haul (Neuston, daily while in transit). During the first two hours a zig-zag track at 8 knt will be done for ADCP alignment calibration
March 17 morning (time always GMT): 18W approx., CTD test@500m, SeaSoar deployment test (navigation at 8 knt for 3 h)
March 18 morning: 22W, CTD@2000m, plankton haul (Bongo, when daytime), Apex floats tests (total 6 h)
(note: CTD always means + LADCP + rossette water samples at 0, 5, 10, 50, 100, 125, 150, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1400, 1600, 1800 and 2000 m & Deep Chlorophyll Maximum)
March 19 morning/afternoon: 25.5 oW, CTD@2000m, plankton haul, ASIP float tests (6 h)
March 20: steaming
March 21 after midnight: 31oW, CTD@2000m, plankton haul
March 22 morning: 15 nm N of point a (see figure 1), CTD@2000m (symbol +), plankton haul. SeaSoar mesoscale survey (SPURS-MIDAS leg 1) starts heading South (some 80 nm East of WHOI mooring 24o 34.867’N, 38o 0.0’W)
The survey will proceed at 8 knt following the N-S 75 nm tracks spaced 15 nm (letters a-r)
March 25 early afternoon: interruption of survey along track 7 (line m-n) to approach the WHOI mooring and deploy several buoys (ASIP, Surpact, Apex), CTD@2000m. Survey resumed after 4-5 h
March 26 evening: Survey ends at point r. Starts deployment of surface drifters in a squared box (SPURS-MIDAS leg 2). CTD casts@2000m at each corner (see figure 2). 18 out of the total 48 drifters will be released in triplets. This will be done to study the dispersion near features such as fronts that should be revealed by the SeaSoar survey. Otherwise the triplets will be just deployed at the four corners and two near the center of the box, at either two of the four center nodes
March 27: During the release of drifters along the line p-o (between 3rd and 4th points) we will go to the WHOI mooring area to recover the buoys deployed two days before
March 28: At each release point along the line n-m a CTD cast will be done down to 700 m to get information on the surface and subduction waters, as well as to take water samples for comparison with measurements taken in a S-N transect along 28.5W by R/V Hesperides in early May for the FICARAM project
May 29: Once the drifters deployment is finished we will continue the SeaSoar mesoscale survey in the southern part of the area, starting at point g (see figure 3). Three 2000 m CTD casts will be done to complete the sampling below the surface layer.
April 3: Southern survey ends at point r. Shallow CTD cast for SeaSoar calibration
April 3-8: Targeted submesoscale measurements on specific sites identified during the mesoscale survey (1-2 days duration each). One of the samplings will be ASIP profiling close to a WHOI turbulence glider now in operation in the area. When/if possible plankton hauls and CTD stations will also be done. The final strategy for all these measurements will be fixed by joint data analysis with the Endeavor team and will be performed in an optimized way by the two vessels
April 8: End of operations in the SPURS site. Transit to Azores with some CTD casts and plankton hauls as in the transit from Las Palmas
April 13: End of SPURS-MIDAS cruise in Ponta Delgada (Azores). Sarmiento returns to Vigo, where equipment and samples will be downloaded