During 2011, Applied Ocean Physics & Engineering Department (AOPE) scientists, engineers, and research staff developed new instruments and vehicles, discovered ancient and modern shipwrecks on the sea floor, and investigated ocean processes from the abyss to the surf zone. Ongoing projects examine the fluid dynamics of propulsion of marine organisms, dynamics and sediment transport in the surf zone and estuaries, development and application of autonomous and remotely operated vehicles, ocean acoustics, and mixing in the ocean.
Recently tenured AOPE scientist Houshuo Jiang is working with postdoc Kakani Katija Young on the mechanisms of propulsion of copepods, krill and jellyfish by measuring the flow of water around the organisms at extremely high resolution. These researchers perform their measurements in the lab and in the ocean, to determine how the organisms propel themselves to obtain food and avoid predators. Jiang and Young are also investigating the hypothesis that swimming microorganisms are a major source of ocean mixing!
The REMUS group in AOPE were called upon to search for the Air France jet that crashed in the South Atlantic Ocean in 2009, after commercial efforts to locate the wreckage had failed. Led by Mike Purcell, the group deployed the REMUS 6000 submersible in the vicinity of the last known position of the aircraft, and used the advanced acoustic sensing systems and control mechanisms of the REMUS vehicle to locate, identify and survey the wreckage at approximately 3,900 meters (2.4 mi) depth.
AOPE’s researchers also use autonomous vehicles to investigate ancient shipwrecks. Brendan Foley’s group partnered with the Greek Ministry of Culture to carry out a maritime archaeological survey off Crete, Greece. They located 8 shipwrecks dating as far back as ~150 BC, and 3 ancient anchorages dating to as long ago as ~1100 BC.
AOPE scientists are studying how large-scale ocean currents like the Gulf Stream interact with smaller-scale eddies to produce mixing of different ocean water masses. They deployed fluorescent dye off the coast of North Carolina and tracked it with aircraft and oceanographic ships, including WHOI’s R/V Oceanus, simultaneously measuring the currents and winds in order to determine the mechanisms causing the spreading of the dye and thus the mixing processes at scales from 100 m to 10 km in the ocean.
Martha’s Vineyard has been the focus of intensive AOPE research efforts for more than a decade, and that tradition continued in 2011. Steve Elgar’s nearshore processes group investigated the recent breach that produced a new inlet between Katama Bay and the Atlantic Ocean, using pressure gauges and current meters to determine the tidal dynamics, and jet-ski surveys to measure rapid changes in the area bathymetry caused by sediment transport. Peter Traykovski and Rocky Geyer investigated the influence of the breach on sediment movements and the morphology of nearby Wasque shoals, where a small island emerged due to changes in the tidal currents and waves resulting from the Katama breach.
Jim Preisig’s signal processing and communications group used the Hawaiian archipelago as the field site for a test of new acoustic communication technology. Although sound can travel great distances in the ocean, precise communication is hampered by numerous sources of noise and distortion, particularly in shallow, energetic coastal environments. Preisig’s advanced coding and signal processing methods are overcoming these challenges, with particular significance to defense applications.
AOPE scientists also have longstanding interests in acoustics research. The acousticians in Tim Stanton’s group are investigating the acoustic backscatter signals (echoes) produced by fish, for the purpose of improved fisheries management. During 2011 they performed field studies in the Gulf of Maine in collaboration with the National Marine Fisheries Service. This research has the potential to greatly improve our ability to enumerate and manage fish stocks.
In related research, recently tenured scientist Andone Lavery is also studying acoustic backscatter in the Gulf of Maine, but the target of her investigations is the acoustic signal, or type of echoes, produced by pteropods—small plankton with calcium carbonate shells. These animals are particularly vulnerable to ocean acidification, so her research into acoustic methods to determine their abundance is particularly relevant as scientists try to determine the effect of increased atmospheric carbon dioxide on oceanic ecosystems.
—Rocky Geyer, Department Chair