Global climate change and you: eMOLT tells a tale of warmth

First published in Landings, April, 2013.

In December, 2011, several offshore lobstermen who were participants in the Environmental Monitors on Lobster Traps (eMOLT) ocean temperature monitoring program mentioned to Woods Hole oceanographers that they were seeing unusually high sea surface temperatures and strong currents moving in an odd direction along the outer continental shelf south of New England.

NOAA oceanographer Jim Manning, who coordinates the eMOLT program, and his colleagues at the Woods Hole Oceanographic Institute decided to take a look. Drawing on data received from lobstermen and from current drifters built by students at Cape Fear Community College in Wilmington, North Carolina, as well as other observational data, Manning and others set about studying what was happening far from land.

An eMOLT temperature tag. NEFSC photo.

An eMOLT temperature tag. NEFSC photo.

This was just the latest result of a long-standing collaboration between Manning and Gulf of Maine lobstermen. Through the eMOLT program, lobstermen throughout the region have attached low-cost temperature sensors to their lobster traps for the past twelve years. The equipment provides researchers such as Manning with a treasure trove of data on bottom temperature. Lobstermen have occasionally measured bottom salinity and current velocity as well. To date, the eMOLT database contains 5 million hourly records of temperature and 80,000 hourly records of salinity.

In addition, simple current drifters have been used to calculate surface currents throughout the Gulf of Maine and further offshore. The current drifters initially were built by students at Southern Maine Community College; today the drifters are being built by students at many other schools around the region. Each drifter uses GPS to communicate its position via satellite. Data provided by the drifters have given scientists insights on how the currents can transport and disperse particles around the Gulf and beyond.

Drifters set at the mouth of Buzzard’s Bay, for example, showed what can happen to lobster larvae in the bay. According to Manning and his colleagues at the Massachusetts Division of Marine Fisheries, the drifters indicated that stronger currents ten miles out (where greater numbers of female lobsters have migrated recently) may be dragging lobster larvae away from the bay. In the Great South Channel off Cape Cod, drifters tend to sail about for weeks, constrained by the currents. Like the drifters, tiny zooplankton are also kept in place. One type of zooplankton, copepods, is the preferred food of North Atlantic right whales, thus in the early summer many of those endangered whales can be found congregating in the Channel.

Curious about what was happening at the outer reaches of the Gulf of Maine, Manning and his fellow scientists speculated that data from eMOLT sensors at two deep water sites would give insight into temperature changes at depth. He asked lobstermen Rob Connelly and Marc Palombo to deploy their traps at two sites located near the shelf break, where the shelf begins a sharp drop toward the undersea abyssal plain.

When the data from the traps and drifters were analyzed, the scientists concluded that the warm water near the bottom of the outer continental shelf resulted from a direct interaction between the nearby Gulf Stream and the seafloor. In late October of 2011, the Gulf Stream made an unexpected jump to the northeast. Then in December, the stream’s meanders brought a second surge of warm water onto the continental shelf. All this happened just before the unusually warm 2011-2012 winter season in New England. Glen Gawarkiewicz was the lead author on the resulting scientific paper which was published in August, 2012, in the on-line scientific journal, Nature’s Scientific Reports.

Low-cost current drifters built by students provide scientists information about the Gulf of Maine. Photo courtesy of NEFSC.

Low-cost current drifters built by students provide scientists information about the Gulf of Maine. Photo courtesy of NEFSC.

Manning is always improving the eMOLT program. One new feature is a real-time bottom temperature sensor that wirelessly transmits data to a shipboard system as it is hauled on deck. His colleague Vitalii Sheremet has introduced a low-cost bottom-current meter that uses a simple tilt meter encased in buoyant PVC pipe. Several lobstermen have also mounted underwater GoPro cameras to their lobster traps to record what happens to a trap when it reaches the bottom. One trap set by John Melquist of Matinicus Island shows lobsters entering the trap within seconds of it landing on the seafloor (http://vimeo.com/46193979).

Manning understands the value of paying attention to what lobstermen see when they are out fishing. “Our philosophy is that local fishermen already spend their days at sea, have the biggest stake in preserving our coastal marine resources, and are the most knowledgeable of the local waters. Their interest, curiosity, and enthusiasm are sincere,” he said.