The Final Countdown
It’s the second weekend out here on the Tasman Sea for the TTIDE leg 3 crew aboard the R/V
Revelle. Today we are pushing hard to finish recovering all four remaining moorings still in the water. If the team can make all that happen before darkness falls tonight that will keep the TTIDE project ahead of schedule and give the scientists extra time to conduct “yoyo” and “towyo” operations – filling important gaps in our view of the internal wave energy pulsing across the Tasman Sea. There are only a few days left until the R/V Revelle steams “back to the barn” and for all aboard it’s starting to feel a bit like the final countdown.
Dawn broke gray and chilly but the howling westerly wind and the short, steep windswell it generated has mercifully laid down. It was a great way to start the recovery of TTIDE “M4”, a 2300 metre tall mooring designed to capture the energy of internal waves breaking in the shallowing waters of the continental slope using two highly specialised McLane profilers.
The McLane profilers are “wire-crawlers”, programable robots that climb and descend the mooring line over and over and over again, one million metres worth of travel in every one of their large internal lithium battery packs. These profilers come jammed with an array of instruments that
measure pressure, temperature, salinity, and most importantly current velocity at a finer scale and across a longer vertical reach than any other tool in our oceanographic toolbox.
The McLane data are invaluable, they are costly acquire, and each profiler runs on hardware and software that takes great skill and experience to operate. The McLane profiler, often abbreviated as “MP” in casual conversation on the back deck, is the star of the show and everybody quietly anticipates the outcome each time one of these yellow beasts breaks the surface of the sea under the tug of our winches. Did the wire-crawler survive the pressures of the deep and what data will it hold for the TTIDE team?
Science, caught fresh from the sea
The MP’s have indeed brought a data harvest, fresh from the sea. As moorings have been brought onboard the attached instruments are cleaned and logged before TTIDE team members get busy up forward in the analytical labs extracting the data onto a dizzying collection of hard drives.
Time is always short aboard ship but TTIDE scientists have started to look at the new MP data in the past 24 hours, building the initial analyses of what an underwater robot has learned from crawling a mooring wire for many months deep under the surface of the Tasman Sea. This first look at the MP data shows the clear fingerprints of the daily tide, lunar cycle, and the passing of swirling mesoscale eddies as they swept over the slope 20 kilometres or so off St Helens, Tasmania.
When the TTIDE scientists finally return home* they will bring all the fresh science they have caught into their data kitchen and cook up a better understanding of our earth, climate, and ocean.
Thomas Moore, for the TTIDE team
* “home” means many things for the diverse TTIDE team, made up of experts from the University of Minnesota – Duluth, the University of Alaska – Fairbanks, Oregon State University, the University of Washington, and the Scripps Institution of Oceanography.