Monday, February 25, 2013

Cruise Plan for the Sarmiento

From Chief Scientist Jordi Font



SPURS-MIDAS Cruise Plan v2

The SPURS-MIDAS cruise (Las Palmas de Gran Canaria 16 March 2013 – Ponta Delgada, A├žores (to be confirmed) 17 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 measurements (ASIP profiler) and a combined CTD stations-SeaSoar sampling for a mixed-layer depth evolution study. Additional opportunity measurements will be done to collect water and plankton samples for chemical and biological objectives from Spanish researchers not belonging to the MIDAS team.
The cruise plan can be drafted as follows:
March 8: Equipment loaded in Vigo (NW Spain mainland)
March 10: Sarmiento de Gamboa leaves Vigo to Las Palmas
March 16 (approx. 17h GMT): Sarmiento leaves Las Palmas steaming for the SPURS site (around 25N, 38W), nighttime plankton haul (daily while in transit)
March 17 morning: 18oW, CTD@2000m, plankton haul
(note: CTD always means + rossette water samples)

March 18 morning: 22oW, CTD@2000m, plankton haul, Apex floats tests
March 19 morning/afternoon: 26 oW, CTD@2000m, plankton haul, ASIP float tests
March 20 afternoon: 30 oW, CTD@2000m, plankton haul, more tests if necessary
March 21 afternoon: 34 oW, CTD@2000m, plankton haul, SeaSoar first deployment
March 22 early morning: 36 oW (approx.), CTD@4000m close to French deep-Arvor profiling float, plankton haul. Mesoscale survey starts heading South, some 100 nm East of WHOI mooring (see figure)
March 23 daytime: Survey interrupted to pick up the Mixed Layer Lagrangian Float (MLF)
The survey will proceed at 8 knt following the N-S tracks spaced 15 nm (letters a-s), with some CTD casts@1000 m (+) and release of surface drifters in 36 regularly spaced points (blue dots), 30 single, 6 triplets. Plankton hauls in the CTD stations. ASIP operations (and eventually Apex profiles) to be added to this survey plan.
April 2 afternoon (estimated): point s 38.7oW, mesoscale survey ends
April 2-12: Targeted submesoscale measurements started 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. In between or after the above mentioned submesoscale measurements a combined 1000 m CTD stations-SeaSoar sampling- Apex profiling will be performed to study the mixed-layer depth evolution in an area of approx. 100 nm radius. Duration is expected to be of the order of 5-7 days (details to be provided in further versions of this cruise plan).
12 April: End of operations in the SPURS site
12-17 April: Transit to the Azores. CTD stations and plankton hauls also done like in the first transit
17 April: End of SPURS-MIDAS cruise in Ponta Delgada (port still to be confirmed). Sarmiento returns to Vigo, where equipment can be downloaded