Prepared by Brendan Carter

We are pleased to report that we are making our way south out of the Mexican EEZ and doing station work as we go.n We were briefly faced with the difficult decision between waiting on station and abandoning the work in the Mexican EEZ.n Some offshore islands make the Mexican EEZ more than twice as thick as the default 200 nautical mile (nm) limit along our track.n This meant that going south to accomplish work outside of the EEZ while we waited was not a good solution, and also that an unusually large amount of station work (~15%of leg 1) would have been lost if we had given up on the EEZ. Ultimately, we spent nearly a day and a half waiting on station.n We are now slightly behind our ambitious schedule, but relieved to be able to fill in these important measurements of the oxygen deficient zone (ODZ) off Mexico.

Measuring the ODZ is critical for the GO-SHIP goal of monitoring the ocean’s response to climate change. It has been hypothesized that the ocean will lose oxygen over time and ODZs will expand under global warming, consistent with “many but not all” simulations of Earth’s future climate. A portion of our cruise track has been recently identified as a region where the impacts of climate change on interior oxygen may already be detectable. Deploying instruments to monitor this region and testing this hypothesis with another decade of high-quality GO-SHIP measurements were key objectives for this project.n Several of our instruments and personnel were sent with us specifically in order to capture the unique biogeochemistry in the ODZs.

We have (preliminary) data! This is a section of dissolved O2 concentrations as measured by the CTD-rosette sensor package. Black dots are where we have collected seawater for discrete measurements. The blue band at the top is well-ventilated surface water. About one hundred meters below are the (deep red) very low oxygen waters of the ODZ.

Path and station work

As noted in the report 0, we initially transited from San Diego to our test station in US waters, and from there headed to the first station offshore Cabo San Lucas at 22.69°N and 110°W. That first station had an intended depth of 2500 meters. We waited there for clearance, moving offshore after business hours in Mexico City to take care of ship functions (e.g. making freshwater from seawater).nWe quickly began station work after receiving clearance, though we stayed on station for some hours to troubleshoot the CTD-rosette sensor package (see below). We then moved onshore to collect measurements at a 220 m depth station at 22.87°N and 110°W. Since then, we have been moving south along the 110°W meridian. We made the brief northward trip instead of starting at our northernmost station to save a few hours that would otherwise have been spent waiting on station for samplers to finish collecting seawater from the CTD-rosette. After turning south, we had one more nearshore station in 1250 m of water at 22.78°N. Our fourth station was at 22.5°N. Since occupying this station we’ve been transiting south for 0.5° (30 nm) between each station, as we intend to continue to do for most of the P18 line. We deployed floats on stations 15 and 19 and one drifter on station 13. We are currently on station 20 at 14.5°N.

This first float we deployed is specially designed to collect data from the ODZs with a gas tension device. The device will be calibrated using measurements of stable gases being made by Co-Chief Annie Bourbonnais.

Profiles of temperature, salinity, beam transmittance, and oxygen were collected at every station. Profiles of fluorescence and backscatter were also collected at the earlier stations. More than 2000 seawater samples have been collected by our analysts for discrete analyses on the boat and back on land. Data from discrete shipboard analyses are beginning to trickle in to our central repository from our shipboard analysts.nWe expect the floodgates will open soon as our analysts catch up from the abrupt change of pace from prolonged waiting to nearly constantly working.

Troubleshooting

Unfortunately, the ban on research activities in the Mexican EEZ prevented us from more thoroughly testing the CTD-rosette package while we waited.nWe therefore spent some additional time on the first station resolving problems with the electronics that manifested on our first cast below 1300 m. Less than a day of troubleshooting time was required for this and all subsequent package troubleshooting, and the delay allowed time for a bongo tow for coastal organisms and micro-plastics sampling. After many sensors, cables, and parts were replaced by our experts on board, and after some clean-up of the winch electronics by our shipboard electronics technicians’ we now seem to have a functional package to at least 3500 m depth.

One concerning issue has resulted from the new aft winch wire having come from the manufacturer pre-lubricated, contrary to the expectations of the ship personnel when they placed the order.nThe wire began to extrude the lubricant during the casts, and did so increasingly as the package got deeper and the wire tension increased. This resulted in gooey blue lubricant cakes forming up on the block (pulley) that the winch wire spools over. This lubricant then began to slough off onto the deck and, until we developed means to prevent this, onto the rosette frame. It is not believed that this lubricant has affected the package in a meaningful way yet, though there is concern over whether it could and whether we would know if it had. The ship’s crew has gone to lengths to keep this lubricant from affecting the CTD rosette package since it emerged as an issue. Looking forward, it seems most of the lubricant on the first ~3000 m of cable has already been removed since the caking has significantly abated on recent casts. However, we fear this problem will return as we begin doing deeper casts.

*A quick update on this before I send this out.n We’ve switched to the forward winch since the aft winch began spooling out in an uncontrolled fashion during a recovery on station 18. Everyone is safe, the rosette package is intact, and we’re now close to finishing a successful cast on the forward winch. There will probably be more on this in the next weekly update, so stay tuned.

A storm dodged?

We’ve been watching the track of Hurricane Otto as it bee-lined for us from the Atlantic. Luckily, it seems to have slowed considerably, and weakened into an extra-tropical depression on its way over.

Summary

We’re pleased to be doing work again, and I look forward to providing updates on the measurements as we continue south along the P18 section.nWe have some concerns for our schedule and some work to do optimizing our CTD/rosette/winch setup. However, it is refreshing to be facing these more-typical oceanographic hurdles instead of waiting on station 1.

Annie, Mike, Brian, Josh, and Sean, working together to deploy the APL/UW Gasfloat by crane over the Mexican ODZ. Photo credit: Christian Lewis.

Timeline of issues affecting the P18 schedule

• • 1. 1. The #2 main propulsion diesel generator (MPDG) had mechanical damage where the rotor had touched the windings = rewinding the generator which took 30 days and10/04/2016 Scheduled completion of dry dock repair period is delayed from 10/16/2016 to 10/20/2016:
       2. Two significant items were discovered during the drydocking which caused the delays:
       3. The thrust collars where the z-drives insert into the ship were worn and out of round. These required machining of the hull and fabrication of the new collars.

• • 10/07/2016 Leg 1 of the P18 GO-SHIP project is delayed by 5 days in light of the shifting schedule. Leg 2 is delayed by 4 days.

• • 10/20/2016 Brown completes the dry dock repair period. Many repairs were completed. Notable repairs for GO-SHIP work include:
    1. 1. Overhaul of both Markey winches.
       2. Replacement of the aft winch wire with new 0.322” wire. Forward wire is gently used.

• • 10/22/2016 Brown completes sea trials (1 of 5) in the San Francisco Bay. This trial is considered a success.

• • 10/24/2016 A previously unsolved intermittent issue with the GE propulsion motor drive cabinets (automation that runs the propulsion motors) re-surfaces on the transit from San Francisco to San Diego.

• • 10/26/2016 A second sea trial (2 of 5) is conducted with the goal of resolving the drive cabinet issue that resurfaced on the transit, but work done on the sea trial does not identify the cause.

• • ~10/27/2016 An issue is communicated regarding the aft winch’s ability to spool.

• • ~10/28/2016 A Markey representative identifies a wiring error on the aft winch. Fixing it resolves the winch issue.

• • 11/01/2016 A third (3 of 5) sea trial is scheduled for Monday 11/07 with representatives from the company that creates the drive cabinets on board.

• • 11/04/2016 Overtightened screws on an engine part (the aluminum rocker arm baseplate) are reported to have caused damage.nThis damage was first apparent at the end of the second sea trial and manifested with oil leaking onto the engine. The report comes near the end of the business day, so no parts are scheduled to be ordered on 11/07. That evening the cruise is delayed to 11/09 or 11/10 on a TBD basis.n

• • 11/07/2016 Sea trials (3 of 5) are conducted and the drive cabinet issue is identified, a fix is made, and the issue is declared resolved.nReplacement parts are ordered for the damaged engine part (first business day since discovery). The expected sailing date is of 11/09 is ruled out at 1000.

• • 11/09/2016 Delays getting the part order completed and a longer estimated delivery timeframe pushes back the sailing date to 11/12/2016 at 1700.

• • 11/11/2016 Parts arrive and CAT technicians work alongside engineers to get the parts installed quickly. The departure time is pushed up 2 hours to 1500. The ship is deemed ready to go in the late evening.

• • 11/12/2016 Departed San Diego at 1500. Fuel redistribution operations result in loss of fuel from a small holding tank. The vessel stops for 1-3 hours while this tank is being refilled. Separately, high temperatures are noted in two areas of the engine. Engineers work to identify the cause of the elevated temperatures.

• • 11/13/2016 Troubleshooting for elevated engine temperatures is ongoing until 1700.nEngine RPM are slowed to 660 during troubleshooting, but speed over ground remains consistent at ~11.5 kts. At 1700, ~250 km from San Diego, it is announced that the troubleshooting has been unable to identify the root cause. Given the inability to operate the engine safely at full capacity, the Brown is turned around to return to San Diego for shore-side diagnosis and repairs by engineers working alongside Wärtsilä representatives (the company that makes the engine).nTurnaround at ~28° 36′ N.Contacts at the Mexican Department of State are informed of the change of plan on the same day (separate from the extension request).

• • 11/14/2016 We return to San Diego making good time.The transit is halted at 31° 46.07′ N 117° 6.31’W for an impromptu test cast to ~1300 m. The Markey winch requires 1 adjustment at ~200 m wire out, but the winch otherwise is not a major concern.

    Contacts at the Mexican Department of State are provided a translated formal request for an extension.

• • 11/15/2016 A potential engine fix (a replaced pump) is identified and implemented.nA sea trial (4 of 5) is planned for 11/16/2016.

• • 11/16/2016 The sea trial (4 of 5) is conducted, and the potential engine fix is determined to have not resolved the elevated temperature issue. A representative from Wärtsilä is scheduled to join the ship on 11/17/2016 for troubleshooting.A second test cast is conducted at 32° 37.64′ N 117° 26.55′ W in ~280 m of water.

• • 11/17/2016 Sea trial (5 of 5) is conducted with the Wärtsilä rep on board. An oil pump is determined to have been in a bypass mode, restricting oil flow. The mode is switched and engine temperatures remain stable for several hours of travel at ~12.5 kts. Confirmation of this diagnosis is planned for 11/18/2016. Scientists that returned home are recalled with ~36 hours notice to return to the vessel.

• • 11/18/2016 Two of four Offices have reported approval for an extension of Mexican clearance by the end of the business day. The Mexican offices close for a 3 day weekend without hearing from the remaining 2 offices.

• • 11/19/2016 The Brown departs San Diego for P18 for the second time, conducting 4 tests casts in 1300 m depth at the edge of US waters. Only the first cast goes below 200 m, with the subsequent 3 casts being used to troubleshoot a CTD pumpThe Brown departs for the first P18 station at ~2000.

• • 11/22/2016 We arrive at ~10:00 and begin waiting on station.

• • 11/23/2016 Mexican clearance is granted at 20:00 and we begin CTD work.Station 1: Communications errors require swapping CTD units, and the CTD cast is repeated.

    The winch wire is caked in bluish grease after the first deep cast. This grease gathers in formations on the block and periodically plops onto the deck and into the water. Some gets on the package (primarily the frame and the outside of the bottles), though the sensors and the Niskin bottles are not known to be affected.

• • 11/24/2016 to present. Station work continues while the CTD-rosette team troubleshoots (increasingly less frequent) transmission errors between the package and the rosette. These errors appear to have been eliminated by station 11, though the current package no longer has the FLBB attached due to the lower power supply (available amperage) on the CTD unit currently being employed. The CTD-rosette package experts are formulating a longer term plan to restore this sensor to our package now that the short term issues have been solved.