NASA’s Salinity Processes in the Upper Ocean Regional Study has been out to sea for two weeks studying ocean salinity. They deployed a vast array of monitoring devices, which they will use to model the ocean and calibrate NASA’s Aquarius Satellite. Read our previous coverage of the mission here. The Environmental Monitor checked in with SPURS’ Chief Scientist Ray Schmitt, an oceanographer at the Woods Hole Oceanographic Institution, to see how the voyage has been going.
EM: How was the departure to the surface salinity maximum? Did scooting by Hurricane Michael and Hurricane Leslie go as planned?
RS: It looked like both storms could be a problem for us. Pounding against high seas and strong winds is tough on everybody and the gear and consumes a lot of fuel as well. The Captain chose to put on extra speed to get ahead of Leslie’s projected track northward. Fortunately it slowed down and we were able to pass to the north of it. That afforded us some new sampling opportunities: the profiling floats we are deploying are equipped to make ambient noise measurements, which can be used to estimate wind speed and rain rate. We had planned to deploy some on the way to the SPURS site, so we dropped two in the projected path of Leslie. It appears our marksmanship was excellent.
It actually does not rain a lot in the SPURS area, so those floats may have a more interesting signal.
Michael moved to the north before we reached our area; he would have been right in the way if he had not moved. This past week we had Nadine pass to our south, then west and north as it looped around our area. It’s an unusually long-lived storm and some forecasts say it may come back toward us on the weekend. We are feeling its swell which occasionally makes the ride uncomfortable, but we are not feeling its winds. In general we have had very light winds.
EM: What does the daily routine look like for the crew on the Knorr now that you are in the area of study?
RS: We had about a one-week steam to get on site, then spent most of time deploying the various instruments. During this period, each instrument team would be called upon in turn to get their gear in the water. The large WHOI flux mooring was an all-day affair, the deployment of floats and surface drifters just a brief stop.
We completed nearly all the gear deployments yesterday and have now started on a regular schedule of CTD casts and microstructure profiling near our moorings. We are steaming between the moorings and doing Under-Way CTD casts.
EM: The SPURS team is deploying a huge amount of monitoring and sampling instruments. How much preparation, onboard the ship, does it take to ready for instrument deployments?
RS: Most of the preparation occurred many months ago ashore. The WHOI Flux Mooring was by far the biggest challenge on the ship, spools of wire and rope had to be craned into position, lots of gear had to be shackled together or bolted to the wire in the proper sequence. Also, we had to do a very careful bottom survey using our multibeam to get the right depths.
Most of the other gear just required a final check out of the electronics, loading the mission program and the like. Some of the gliders required fine tuning of the ballast, which we were able to do using a small boat. There are always plenty of volunteers for a boat trip in this fine weather.
EM: What has been the most difficult instrument to deploy ?
RS: The WHOI Flux Mooring. It started after breakfast with deployment of the large discus buoy with all its delicate instruments. It’s quite heavy, the ship is rolling and you keep a lot of lines on it connected to air-tuggers to maintain control. The boat then steams away from it, dragging it along and adding all the gear that it has to support.
This takes a long time, as sections of chain, instruments, wire rope with instruments attached in the right places are all added to the mooring. Toward the end you are streaming out synthetic line, then glass spheres, releases and finally the 10,000 lb anchor. Deploying a mooring is a carefully choreographed ballet of physics. It’s a marvelous thing to watch. Just before dinner the tension on the line pulls the anchor off the stern with a huge splash, at just the right spot that you picked out from the bottom survey. It takes an hour for the anchor to reach the bottom then you range on the releases acoustically to see how well you hit your target.
EM: All those instruments surely generate a large amount of data. What does it take to manage all that information?
RS: For SPURS NASA’s Jet Propulsion Laboratory in Pasadena is handling the data management and archiving.
EM: What has the ocean salinity data shown, if anything?
RS: I was quite surprised by how high the surface salinities are. We are used to looking at climatological atlases which portray the salinity maximum here as 37.3 parts per thousand. When we got on site we found that they were nearly 37.8 ppt! This is much higher than I expected.
EM: What’s it like knowing that you can’t simply pop back out to sea to fix a mistake?
RS: Every group carries lots of spares. We are certainly fixing our mistakes out here while we can. The ship has some machining and welding capabilities. Once we leave, there will certainly be gear failures; the ocean is a harsh environment. But we learn from our failures and build more robust instruments for the next time.
EM: How much longer will the SPURS mission be at sea? Is there anything in particular you will take away from this expedition besides a mountain of data?
RS: We have another 20 days to go before we reach the Azores.
In addition to taking home a lot of data, I certainly will have gained a few pounds; the food aboard ship is excellent and plentiful, and I seem to have twice the appetite I have at home. I’ll also have made some new friends; you get to know people really well spending so much time with them in the confined space of a research ship. And there is some personal growth as well, this project is sufficiently large that my obligation to manage the enterprise precludes getting too involved in the details of instruments and sampling the way I used to. I just have to step back and let these wonderfully clever young people make the most of their opportunities.