The primary goal of this project was to investigate an important process by which waters from the deep ocean get into the continental shelf south of New England. This process has been known about for roughly one hundred years but before this project there had not been a dedicated study to map one of these salty intrusions onto the continental shelf. These intrusions occur primarily during the summer, and normally are at a depth of about 100 feet. Typical thickness is about 60 feet.

The observational strategy was to conduct two research cruises, one pilot and one primary, lasting one and two weeks respectively. We planned to use state of the art equipment including multiple Autonomous Underwater Vehicles and sensors that measure the intensity of turbulence around the intrusion.

A novel element of this project was the extremely close interactions with the Commercial Fisheries Research Foundation of Rhode Island, and by extension, the commercial fishing community in Rhode Island. We were in close contact with the Foundation during the first cruise, and they provided daily reports on our cruise to the fleet in Rhode Island. During the second cruise, a staff member from the Foundation came along and provided detailed daily reports and photos of the science activities. At the end of the project a brochure detailing the research results were sent out to 300 recipients following Foundation activities.

The COVID pandemic delayed the cruises. In the interim, a study using data collected by fishing vessels associated with the Foundation was completed. It showed that there was a 70% increase in frequency of these intrusions for the time period 2015-2019 versus pre-2000. In addition the intrusions penetrated further onshore and were more salty. A second study found that these intrusions were frequently associated with the presence of a large Gulf Stream ring near the edge of the continental shelf.

The first research cruise was conducted in June, 2021. The initial challenge was to locate a salty intrusion given that they are subsurface features and not visible from satellites. We identified an intrusion on the first day. We then proceeded to make sections across the intrusion using both Autonomous Underwater Vehicles as well as ship-borne sensors. We established the alongshelf scale of the intrusion, which was an element of these intrusions which was poorly known previously. We also measured velocities in the deep ocean showing strong northward motion that likely contributed to the formation of the intrusion. Two important novel contributions were the use of sensor driven sampling of the northern edge of the intrusion using vehicle autonomy (like a self-driving car) and detailed turbulence measurements that will allow us to infer mixing rates around the intrusion. A manuscript has been submitted describing the mapping of the intrusion and has received initial favorable reviews. A talk on the turbulence measurements was given at a national meeting.

The second cruise occurred in September 2022. Again, we identified an intrusion on the first day. This was a shorter cruise than the first due to the postponements due to COVID. We again mapped an intrusion and found it to be much saltier than the average values from the study using historical data. A key difference in this intrusion relative to the first was that the second was moving onshore at a speed of half a knot. This strong of an onshore velocity (with the tides removed) is unusual and has important ecological significance.

The results from the observations and the historical studies have been very widely spread throughout the commercial fishing community in the northeast. Results have been presented at the National Cooperative Research meeting in October 2023, at Lund Fisheries in Cape May NJ in June 2023 and June 2024, in Oceanographic Updates presented twice a year at the Commercial Fisheries Research Foundation, at the Cape Cod Commercial Fishermen's Alliance, at a Summit to discuss research contributing to the stock assessment for Longfin Squid in April 2024, and in various other meetings with the commercial fishing industry. Data from this project contributed to an earlier stock assessment for shortfin squid. Several members of the team on this project participate in weekly informal meetings with both NOAA scientists and members of the commercial fishing industry as part of the informal "Squid Squad". Lessons learned from this project thus are directly benefitting the fishing industry and contributing to both adaptability and sustainability during a time of rapid change in the ocean.

This project also led to a number of media stories about both science-fishing industry interactions as well as ocean warming. Media outlets included the Boston Globe, the Washington Post, National Public Radio, the local Fox TV station in Boston, and a major newspaper in Toronto.

The project was successful in terms of both basic science and engaging the commercial fishing industry,.

Last Modified: 01/22/2025
Modified by: Glen G Gawarkiewicz