When we talk about ocean exploration we think of expeditions to study the ocean below the sea surface with deep diving submersibles and remotely operated vehicles (ROV). These continue the famous expeditions that started in the 1800s, most notably the 1873-1876 Challenger Expedition. When I walk into the lobby at GSO I often stop by the monitors to marvel at the variety of marine life these modern expeditions reveal to us. But there are other aspects of the deep ocean waiting to be explored, invisible to us but no less real. I’m thinking of how little we know about deep ocean currents and their role in shaping the ocean and world above.
In my January 15 blog, I describe several methods for measuring currents at depth from vessels underway. Some exist, others will require development before they can become operational. But already today we’ve seen how acoustic Doppler current profilers (ADCP) operating on merchant marine (MM) vessels, enable us to do what can’t be done any other way: the ability to resolve the structure of ocean currents, and to monitor their developments over time. While current meters on moorings give us excellent temporal coverage, this comes at great cost when maintained over long time. Further, a moored instrument gives us no spatial information. MM-based ADCPs address both shortcomings: they scan currents in detail, and most importantly, the regular service of these vessels provides open-ended coverage in time.
Our experience working with the MM has been overwhelmingly positive. Every time we have approached a vessel operator about installing instrumentation in the hull to measure currents, they have expressed a willingness to help. The merchant marine sees this as a form of public service, after all they have a presence on the high seas second to none. While they never charge us for the access, they impose one very strict requirement: we must not in any way interfere with their work or schedule. This means that the instrumentation must be extremely reliable and operate without personnel onboard and without the need for shipboard services while enroute. When you think about that it’s a pretty good deal!
Consider: scanning ocean currents with hull-mounted instruments 24 hours a day, 7 days a week, all year round, year after year, traversing the same route on a regular and sustained schedule. That’s an incredible return on investment. As the archive of data grows, it can be mined in many ways, to determine mean currents, eddy statistics and transports along the route and how they evolve over time. Several groups are doing this today, but they are largely limited to the top 1000 m. As I wrote before, we can do far better, the technologies exist for reaching much deeper. We just need to put our minds together to develop these. This will of course cost but look at it this way: these novel instruments operated in a partnership with the MM will give us an unmatched ability to explore the fourth dimension of the entire water column. I think the time is ripe to propose to the federal agencies that they initiate a call for proposals to develop these technologies. There is so much to be learned.