When winter winds began rattling the storm windows last autumn, Andrey Shcherbina and Glen Gawarkiewicz shook the mothballs out of their cold-weather exposure suits and dusted off their sea boots. For the second consecutive winter, the two physical oceanographers at Woods Hole Oceanographic Institution (WHOI) and their small team braved rowdy seas to study how winter storms affect the shallow current flowing south through our coastal back yard—parallel to Cape Cod’s extended forearm, from Provincetown to Chatham.
Andrey and Glen aren’t the only ones interested in how the coastal current changes in winter. Ted Ligenza, a Chatham hook fisherman, also wants to know. The cod he chases with his longlines have an affinity for well-mixed winter water. Ted monitored the results of our experiment last winter—in particular, how offshore water temperatures changed from surface to seafloor—by watching our project’s website. Shellfish farmers and state health officials are also keenly interested, because the coastal current controls the movement of dangerous red tide algae around the Cape.
Like the atmosphere with its ever-moving high- and low-pressure systems, the oceans have the equivalent of “undersea weather.” The oceans have masses of relatively colder or saltier water that are denser and sink, or warmer or fresher waters that are more buoyant and rise. These masses continually move and interact to produce a highly energetic environment. Many factors influence the undersea weather. Cold winter air cools the sea surface; precipitation adds fresh water; tides and winds mix things up. Winter storms may do all three, but not many scientists have measured it directly because winter oceanography can be both difficult and costly, involving large ships, long cruises, and big fuel bills.
Our mission is to reveal how the Outer Cape water masses’ temperature, salinity, and currents change during the winter. Funded by the WHOI Coastal Ocean Institute and the Woods Hole Sea Grant program, we used a combination of inexpensive, lightweight moored instruments and a sophisticated autonomous swimming vehicle called the REMUS (Remote Environmental Monitoring UnitS). Both were deployed from small, fast boats—when the weather allowed.