Diversion Of Gulf Stream Path Uncovered By Scientists In Late 2011

At a meeting with New England commercial fishermen last December, physical oceanographers Glen Gawarkiewicz and Al Plueddemann from the Woods Hole Oceanographic Institution (WHOI) were alerted by three fishermen about unusually high surface water temperatures and strong currents on the outer continental shelf south of New England.

“I promised them I would look into why that was happening,” Gawarkiewicz says.

The result of his investigation was a discovery that the Gulf Stream diverged well to the north of its normal path beginning in late October 2011, causing the warmer-than-usual ocean temperatures along the New England continental shelf.

The researchers’ findings, “Direct interaction between the Gulf Stream and the shelfbreak south of New England,” were published in the August 2012 issue of the journal Scientific Reports.

To begin to unravel the mystery, Gawarkiewicz and his colleagues assembled data from a variety of sources and recreated a record of the Gulf Stream path during the fall of 2011.

First, they tapped into data collected by a program called eMOLT, a non-profit collaboration of fishing industry, research, academic and government entities, run by James Manning of National Oceanic and Atmospheric Administration’s Northeast Fisheries Science Center. For more than a decade the program has recorded near-bottom ocean temperatures by distributing temperature probes to lobstermen.

Manning and scientists from WHOI, including Robert Todd and Magdalena Andres, analyzed a time series of temperatures from two eMOLT sites, OC01 and TA51, which were located over the outer continental shelf near the shelfbreak, and identified two events when temperatures suddenly increased by 6.2 and 6.7 degrees C, respectively, to highs of more than 18 degrees C.

“These are very dramatic events for the outer continental shelf, at least 2 degrees C warmer than we’ve seen since 2001,” says Gawarkiewicz. “Near-bottom temperatures of 18 degrees C on the outer shelf are extremely high for late autumn.” The maximum recorded temperature in December 2011 was the warmest bottom temperature recorded in 6 years of records at the OC01 site.

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