Cruise Plan Seafloor Geodesy, Southern Juan de Fuca plate Sept 4-22, 2003

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Brandon Blankenship
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1 Cruise Plan Seafloor Geodesy, Southern Juan de Fuca plate Sept 4-22, 2003 We will use the R.V. Roger Revelle to [1] deploy a direct- path transponder array across the ~1-km-wide axial valley of the south Cleft segment of the Juan de Fuca Ridge [2] collect GPS-Acoustic data at two seafloor geodetic arrays, one approximately 25 km east of the south Cleft segment and a second 150 km west of Newport, Oregon. [3] test synthetic aperture sonar (SAS) and interferometric synthetic aperture sonar (InSAS) imaging using the Simrad EM 120 and [4] provide facilities for two Central Washington University scientists to collect aerosols for study of the impact of iron and sulfur speciation on biological activity in the ocean. During the cruise multibeam data will be collected when appropriate. The cruise will depart from Newport at 1600 on 4 September and return to San Diego at 0800 on 22 September Map of ship track. 1

2 Personnel The following people will be part of the scientific party on this cruise: Dave Chadwell Chief Scientist SIO-MPL Dave Sandwell Co-Chief Scientist SIO-IGPP Neil Kussat Grad. Student SIO-MPL Davis Thomsen Grad. Student SIO-IGPP Katie Gagnon Grad. Student SIO-MPL TBD Volunteer TBD Volunteer Richard Zimmerman Sr. Dev. Eng. SIO-MPL Denis Rimington Asst. Dev. Eng. SIO-MPL Dave Price Sr. Elec. Tech. SIO-MPL TBD Computer Technician SIO-STS TBD Resident Technician SIO-STS Anne Johansen Scientist Central Washington University Jennifer Key Grad. Stud. Central Washington University On-Loading The ship is scheduled to arrive Newport at 0800 on 02 Sept Deep Tow van, GPS towers and slack tensioner will be already onboard and placed on the aft main deck. Once aboard, several tasks must be completed before departure: Put up the 2 aft GPS towers (1 day, 3 people) Put up the main mast GPS tower (1 day, 3 people) [may leave up following the Hildebrand cruise, pending approval] Assemble the stinger (1 day, 3 people) Load direct-path anchor frames Assemble direct-path units Move the GPS receivers from Van and setup in the Hydro Lab 2

3 Move the computers and controls from VAN and setup in the Electronics Lab Set up storage and instrument staging in the Main Lab String wires from computer lab to wet lab String wires from computer lab to Hydro Lab Position slack tensioner, feed main cable through sheaves Terminate fiber optic cable (pull test to 5k lbs, electrical checks of power conductors, test optical fibers) Spot CV aft under A-frame hanging sheave and secure (sheave hanging from pad eye 46 inches port from center) Spot one DPXP tripod under A-frame wide mouth sheave (sheave hanging from pad eye 46 inches starboard from center) Prep CV for sea CV systems checks then bay test Verify stinger hydrophone operation prior to departure IGPP group load concrete boxes, CWU group setup in bio-analytical lab, mount topside detectors (see notes below) Secure all gear for sea At-Sea Tasks Once at sea, we will complete a number of different tasks: Install direct-path system at axial Cleft (see notes below) Conduct GPS/Acoustic Surveys at each site (see figure above) Conduct vertical position surveys using seafloor survey device Deploy concrete boxes (3 ~ 1 m sq. at 1000 lbs in air) Collect multibeam bathymetry data using on-board SIMRAD system for SAS and InSAS study (see notes below) Collect aerosols for CWU study (see notes below) 3

4 Tentative Calendar/Timeline (Subject to weather, equipment performance, etc.) Sept Revelle arrives Newport (begin loading) Sept 03 continue loading and setup Sept , Depart Newport for So Cass site Sept 05 Arrive So. Cass., wake up PXPs, continue to Cleft Site Sept 06 Deploy Nav. Trans. at Cleft, cut-in transponder, launch CV for recon Sept 07 Deploy DPXP, GPS-A and/or SAS at night, deploy tide gauge, SV data logger Sept 08 Deploy DPXP, Sept 09 Deploy DPXP, Sept 10 Deploy DPXP, Sept 11 DPXP tests Sept 12 SAS test, recover tide gauge Sept 13 GPS-A, CV opps or SAS Sept 14 GPS-A, CV opps Sept 15 Check DPXP, transit to So. Cass. site Sept 16 GPS-A, CV opps, SAS Sept 17 GPS-A, CV opps Sept 18 GPS-A, CV opps, Sept 19 Depart for Pt. Loma Sept 20 Transit - prepare gear for Peru shipment Sept 21 Transit - Sept 22 Arrive San Diego at 0800 at Fuel pier Sept 23 offload gear at NMF 4

5 Off-Loading Once docked at Nimitz Marine Facility, we will complete several off-loading tasks which will include repacking gear in the Deeptow Van for possible storage on the 02 deck forward for transit to South America: Take down 3 GPS towers (2 aft and 1 main mast) Move GPS receivers and gear to Deep Tow van Move computer gear and control from Computer/Electronics lab to Deep Tow van Pull out stinger (clean all parts, store in staging bay, pack Deep Tow extension in Deep Tow van) Store CV in Deep Tow van Move Deep Tow van and GPS towers to 02 deck forward Move aboard additional gear for South America cruise. DPXP Tripod Launch Procedure with CV on R/V Revelle The project calls for precision placement on the sea floor of four Direct Path Precision Transponders (DPXP) at the corners of a 1km square. Water depth is approximately 2300 meters. To execute the placement we will use the MPL Control Vehicle (CV). The CV and one DPXP will both be placed 46 inches off center under the A-frame with the CV port and the DPXP starboard of centerline. The CV and DPXP sheaves will be suspended from the type 2 pad eyes (ref. Glosten Revelle Dwg. # sk2, Revelle A-Frame, Pad Eye Load Key). To do this the slack line tensioner will also have to be moved 48 in port from the usual spot. The DPXP tripod is 10 feet tall and weighs about 1000 lbs in air. The tripod will be lifted by a three point bridle that has a D ring at the vortex. The D ring will have the suspension (launch) line (approx. 20 ft.) attached and a slip line during launch. One end of the slip line will be secured to a cleat just aft of the CV to aid in the transfer of the load from the capstan to the CV. 1) Tie capstan line to DPXP suspension line 2) Put two taglines on DPXP (one each on forward legs) 3) Lift DPXP with capstan and move aft with A-frame 4) Lower DPXP into water with capstan. 5) When top of DPXP is in the water secure slip line on cleat just aft of CV 5

6 6) Continue paying out capstan until load is transferred to slip line. 7) Secure capstan 8) Remove capstan line from suspension line 9) Reposition A-frame for CV launch 10) Put suspension line on CV electromechanical release and close release 11) Take up 0.68 slack wire with winch, tension both CV tag lines 12) Lift CV off deck w winch and move aft with A-frame 13) When suspension line clears stern pay out slip line until load is transferred to CV 14) Remove slip line 15) Remove CV tag lines, A-frame all the way out while lowering CV into water. 6

7 IGPP/MPL - Synthetic Aperture Sonar for High Resolution Mapping and Change Detection Acquire about 24 hours of raw SIMRAD EM 120 hydrophone data in 3 km of ocean depth while the Revelle is being tracked by three geodetic-quality GPS receivers. Three types of experiments are planned. First we will acquire raw hydrophone data while the ship position is maintained within a 5-m diameter circle and at a constant heading. Depending on the sea state, this experiment will provide important information on the ping-to-ping correlation of the sonar echos. Decorrelation will be due to ping-to-ping variations in the footprint of seafloor being insonofied, fluctuations in sound speed, and errors in the determination of ship motion. The second experiment will be to drive a straight ship track over highly reflective seafloor with abundant point scatterers in order to construct a full-resolution SAS image. The third experiment will be to repeat this straight ship track to within 10 m of the reference trackline to investigate the possibility of InSAS. CWU - Atmospheric study (notes from Anne Johansen): (NSF-ATM ) 1) Personnel a) Jennifer Key, Grad. student, Research Assistant b) Anne Johansen, Assistant Professor 2) Equipment and Chemicals a) High volume aerosol collector, with 3 hp pump drawing 28 A at 115 VAC (these power requirements may need special attention) b) Sector sampling system (weather vane with data logger) c) Spectrometer with Liquid Waveguide Capillary Cell (LWCC) d) Chemicals: Ferrozine, hydroxylamine, formate buffer, MQ water (all non-hazardous) other potential equipment: e) Denuder sampling system (including a small pump) f) portable laminar flow hood (3 ft.) 3) Location for sampling equipment I will need a bit more time to study the deck plans before deciding on what is the best location. The front of deck 2 may work as well as the top deck (from past experience, I am hesitant to set up a pump directly on top of the pilot house). I will let you know as soon as I have a better idea. 7

8 4) Brief description of the work plan The high volume aerosol collector will be running continuously except for periods when collection substrates have to be changed and when the wind comes from out of sector (i.e., more than 60 degrees on either side of the ship's centerline, looking forward). Sampling intervals will vary between 4 and 10 hours depending on aerosol mass loadings and time of day. After sample retrieval at the end of each sample interval, extraction with formate buffer and subsequent complexation with ferrozine will allow for Fe(II) determination in the lab (preferentially in a laminar flow hood). Hydroxylamine will be added to one aliquot to determine the readily reducible Fe(III) employing the same ferrozine technique. The remainder of collection substrates will be stored in freezers for further analysis upon return from the cruise. The purpose of this part of the study is to determine the bioavailable iron fraction in atmospheric aerosol. We will potentially also be collecting gaseous S species, as they would help elucidate some aspect of iron speciation. This would involve periodically changing denuders, extracting them with MQ water and bottling and refrigerating this extract to be analyzed upon return from the cruise. Last modified CDC, NHK, RZ 8

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