The mid-depth waters off the east coast of the United States are becoming more salty

The mid-depth waters off the east coast of the United States are becoming more salty

Fishermen from the Commercial Fisheries Research Foundation / WHOI Shelf Research Fleet are preparing to collect data using an instrument that measures temperature and salinity. This work gives rise to WHOI-led study showing an increase in hot water intrusion along the Mid-Atlantic Gulf. (From L to R: Sean Daly, Victor Garcia, Jay Winchenbach). Credit: Jim Violet

A new study led by the Woods Hole Oceanographic Institution (WHOI) shows a significant increase in the frequency of warm saltwater intrusion from the deep ocean to the continental shelf along the Mid-Atlantic Gulf, which stretches from the Gulf of Maine to Cape Hatteras, North Carolina. Using data collected from NOAA’s National Marine Fisheries Service Ecosystem Monitoring program, as well as data collected from the fishing industry, the results of the study show that marine exchange processes have changed greatly over the last 20 years in this region.

The results of the study were described in a recent paper published in Journal of Geophysical Research: Oceans.

“I think the reason the paper is so important is because it quantifies an ocean process that is changing, potentially as a direct result of ocean warming and more layering,” said Glen Gawarkiewicz, senior researcher at WHOI and paper correspondent . “These results may also have major off-the-shelf ecosystem implications. Given the increasing frequency of salt intrusion in mid-depth along the Mid-Atlantic Bight, it will be necessary to address this process properly in numerical simulations to account for salt budgets for the continental shelf and the slope “

An intrusion occurs when warm, salty seawater moves toward the edge of the continental shelf and “penetrates” on cold, fresh continental shelf water. What scientists like Gawarkiewicz note in this study is that multiple intrusions move into the middle of the depths and reach up to 60 miles on shore, carrying the warm offshore water over great distances.

“Water in this region is becoming smaller like the Arctic and more like the tropical Atlantic,” Gawarkiewicz said.

Gawarkiewicz and his collaborators reviewed more than 20,000 profiles collected by research and fishing vessels over the past three decades. Despite the salinity profiles scattered in space and time, the data showed signs of several maximum salt intrusions in the middle of the depth, which increased sharply since 1998. A 2003 paper showed how the intrusions took place about 10% of the time. , and this new study finds it occurs 18% of the time. The team investigates a possible relationship to the annual rate of formation of hot nuclei, which are vortices that form and break off from a ocean current, such as the Gulf Stream.

“There is more and more evidence that conditions are changing rapidly across the entire ecosystem, with offshore waters affecting the shelf more frequently and on very different time scales than we have seen before,” said Paula Fratanoni, head of Oceans and Climate Branch at the Northeast Fisheries Science Center within the National Marine Fisheries Service, and paper co-author. “It is imperative that we work to better understand these processes and any potential impact they may have on critical shelf habitats.”

These results are important not only for physical oceanography and climatological research, but for the commercial fishing industry as well.

“This is a great opportunity for dialogue with the fishing community that helps them recognize these intrusions in the middle of depth when logging a profile. Then they can use it to decide where to fish and focus the bulk of it. Their work, “Gawarkiewicz said. “Future work is needed to determine how the increasing frequencies of this important process can affect the heat and salt balances of the continental shelf as well as wider impacts on continental shelf ecosystem. This study is valuable in quantifying processes that can accelerate this ecosystem adaptation, especially when addressing things like food insecurity. ”

Tropical fish … north? How ocean physics changes water temperature and salinity

More information:
G. Gawarkiewicz et al., Increasing frequency of maximum penetration of salinity in the middle of the depth of the Mid-Atlantic Gulf, Journal of Geophysical Research: Oceans (2022). DOI: 10.1029 / 2021JC018233

Citation: Mid-depth waters off the east coast of the United States become more salty (2022, July 7) Retrieved July 18, 2022 from .html

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