– Local Time 22:13 –
As we headed into our second week of our tropical voyage, both Scripps and WHOI teams knew that a lot of hard work was on the horizon. Due to several unexpected detours to the original travel plan, the ship is running roughly 4-5 days behind schedule. But like any experienced scientist or engineer knows, one must adapt to variability and even more importantly look for new solutions to the existing problems.
That being said, all personnel on the ship have been dialed into making the most of daylight (and sometimes hours into darkness) to ensure that the projects at hand will be completed, new equipment will be deployed, past gear will be recovered, and all data will be properly logged.
Following arrival to WHOI’s NTAS 17 drop site coordinates (approximately 15 Degrees N, 51 Degrees W), it was time for everyone to get their game face on. Roughly 4600 lbs of buoy, state of the art weather instruments, 5 miles of cable and rope, and a 9,000 lb anchor made of stacked locomotive wheels all had to be attached flawlessly and sent over the side of the ship for its yearlong vacation in the Atlantic Ocean.
This WHOI surface buoy is equipped for meteorological and oceanographic measurements to further evaluate air-sea interaction processes that relate to climate variability. NTAS, or Northwest Tropical Atlantic Station is one of three surface buoy sites that provide the sea-level and subsurface weather driven data to Woods Hole for further analysis. Dominant forces acting upon the buoy in this particular location are the Atlantic trade winds, convergence of waves along the equator, and heat exchange between the ocean’s surface and the earth’s atmosphere.
The operation was extensive but with Ben playing QB everyone was able to successfully play their role and do their job to ensure execution of the task without any injury to the crew nor the buoy. As the huge mass was very carefully craned over the port side of the main deck, I had the job of tag lining the canopy of the structure as it was slowly meandered off the side of the ship. It was pretty cool (and little nerve racking) to be given a significant role during arguably the most critical point in the operation. Once Ben pulled the release clamp to slam dunk the buoy into the water, my tag line was connected to the overhaul ball, or better known as the “headache” ball, that had to be immediately pulled away from the top instruments to ensure nothing was hit.
The NTAS buoy’s canopy houses instruments that measure elements like wind speed and direction, precipitation levels, barometric pressure, relative humidity and temperature, as well as short and longwave solar radiation. All instruments provide data with “near real time” telemetry back to Woods Hole, MA at an hourly rate. Regular sample rate data is storred on a central logger within the buoys chamber and is evaluated once the buoy is recovered. Wave height and direction as well as subsurface currents are broadcasted on a near real time scale also.
In addition, the scientific project composed by Scripps called the MOVE project, or Meridional Overturning Variability Experiment, was the other major theme of this voyage. It is controlled by a set of subsurface moorings that monitor the mass, heat energy, and freshwater transports ranging the entire water column of the Deep Western Boundary Current of the Atlantic Ocean. Anchored to the sea floor, the cable is stabilized by articulated sections of glass balls where the top element sits roughly 30 meters below the surface. A cable is the backbone of the mooring spanning its entire length, serving as a means of inductive communication between all instruments. It primarily logs the oxygen rich deep water flowing down from the arctic amidst its role in the atlantic circulation which turns into the gulf stream heading back north as warm water.
Equipped with microcats measuring salinity, conductivity, and depth, the mooring can reverse engineer a mass value of water moving between the two sites as a function of density at various depths. This mass flow rate of water is measured in Sverdrups (Sv), where one Sverdrup = 1,000,000 cubic meters per second. The cable also houses a controller with a modem for logging data and can serve as a relay station for acoustic communication as well. During this leg of the trip, it was deemed that the boat would not have enough time to recover one previously deployed mooring, so it was decided that we would hover over the site to acoustically retrieve the data.
Similar to using the Deck Box when talking to acoustic releases, we can hang a transducer over the side of the ship and can send specific frequency commands to the modem to retrieve the data accumulated over the last two years. This was crucial considering the ongoing time crunch to fit in as much significant work as possible, for it is unclear when the next available time to physically retrieve the mooring would be.
The crew has put in some serious work days the past week to make up some time. It has been a grind for the majority of time spent off the deck was consumed primarily of eating and sleeping. It’s been a fun grind though because every op has been successful and once we finish each one it is apparent how much teamwork is required to put a piece of science in the ocean that’s consumed countless hours of preparation and building. These instruments have traveled thousands of miles on land and then a few thousand more on water to their chosen deployment sites. Once they are finally in the water it is a great thing to see and feel.
– Cam
