Please select your home edition
Henri-Lloyd - For the Obsessed

Study finds no direct link between North Atlantic Ocean currents, sea level along New England Coast

by Woods Hole Oceanographic Institution 17 Jun 2019 12:43 UTC
Study finds no direct link between North Atlantic Ocean currents, sea level along New England Coast © Ethan Daniels, Shutterstock

A new study by the Woods Hole Oceanographic Institution (WHOI) clarifies what influence major currents in the North Atlantic have on sea level along the northeastern United States. The study, published June 13 in the journal Geophysical Research Letters, examined both the strength of the Atlantic Meridional Overturning Circulation (AMOC)—a conveyor belt of currents that move warmer waters north and cooler waters south in the Atlantic—and historical records of sea level in coastal New England.

"Scientists had previously noticed that if the AMOC is stronger in a given season or year, sea levels in the northeast U.S. go down. If the AMOC weakens, average sea levels rise considerably," says Chris Piecuch, a physical oceanographer at WHOI and lead author on the paper. "During the winter of 2009-2010, for example, we saw the AMOC weaken by 30 percent. At the same time, sea level in our region rose by six inches. That doesn't sound like a lot, but a half-foot of sea level rise, held for months, can have serious coastal impacts."

"But, it's been unclear whether those two things—coastal sea level and the AMOC—are linked by cause and effect," adds Piecuch. Although the study confirmed that AMOC intensity and sea level seem to change at the same time, it found that neither directly causes changes in the behavior of the other. Instead, both seem to be controlled simultaneously by variability in major weather patterns over the North Atlantic, such as the North Atlantic Oscillation (NAO).

"Changes in the NAO alter both AMOC and sea level separately," says Piecuch. "As the NAO changes, it affects the trade winds, which blow from the east across the tropical Atlantic. When the NAO is high, the trade winds are stronger than normal, which in turn strengthens AMOC. But at the same time, the westerly winds over New England are also stronger than usual. Together with unusually high air pressure on the northeast coast, this lowers the average sea level. It's wind and pressure that are driving both phenomena."

According to Piecuch, a study like this was not even possible until recently. For the past few decades, satellite imagery has given scientists a record of movement at the ocean's surface, but has been unable to detect currents below the surface. Starting in 2004, however, an international team of scientists began maintaining a chain of instruments that stretch across the Atlantic between Florida and Morocco. The instruments, which are collectively called the RAPID array, hold a variety of sensors that measure currents, salinity, and temperature. "RAPID doesn't resolve the details of every individual current along the way, but it does give us the sum total of the ocean's behavior, which is what the AMOC represents," Piecuch notes.

These findings are particularly important for residents along the northeast coast of the U.S., he adds. Existing climate models suggest sea levels will rise globally in the next century due to climate change, but that sea level rise on the New England coast will be greater than the global average. Scientists have traditionally assumed that the heighted future sea level rise in the northeast U.S. is inextricably tied to a weakening of the AMOC, which the climate models also predict. But, given the study's findings, that assumption might need to be revisited, Piecuch says. "The problem right now is that we only have about 13 years of AMOC data to work with. To get a better sense of how these two things relate to one another in the long term, we'll need to wait for a longer stretch of observational records to become available," he says.

Also collaborating on the study were Glen G. Gawarkiewicz and Jiayan Yang of WHOI; Sönke Dangendorf of Universität Siegen in Germany; and Christopher M. Little and Rui M. Ponte of Atmospheric and Environmental Research, Inc.

The work was supported by National Science Foundation awards OCE-1558966, OCE-1834739, and OCE-1805029; NASA contract NNH16CT01C; and the J. Lamar Worzel Assistant Scientist Fund and the Penzance Endowed Fund in Support of Assistant Scientists at the Woods Hole Oceanographic Institution.

This article has been provided by the courtesy of Woods Hole Oceanographic Institution.

Related Articles

Pakistan's 'Ocean of Water'
Interactions between Pacific and Indian Oceans influenced devastating monsoon The South Asian monsoon brings much-needed rain to the Indian subcontinent each summer. The monsoon typically lasts from mid-June to September. Posted on 3 Feb 2023
Palau's Rock Islands harbor heat-resistant corals
Finding could help reef managers to develop new defenses against ocean warming Ocean warming is driving an increase in the frequency and severity of marine heatwaves, causing untold damage to coral reefs. Posted on 24 Dec 2022
When will Antarctica's ice come crashing down?
Researchers challenge their own assumptions to improve sea-level rise predictions As increased warming in Antarctica causes glaciers to retreat and shed their increasingly-unstable shelves, towering walls of ice are left looming high above the sea. Posted on 20 Nov 2022
Can we use sound to build back reefs?
What does a healthy reef sound like? What does a healthy reef sound like? And can we use that knowledge to help save sick or endangered reefs? Posted on 13 Nov 2022
Five essential ocean-climate technologies
It's hard to overstate how profound the ocean's role is when it comes to climate change It's hard to overstate how profound the ocean's role is when it comes to climate change. It has absorbed more than 90 percent of the heat caused by greenhouse gasses since the Industrial Revolution. Posted on 13 Nov 2022
What happens to natural gas in the ocean?
Methane, the most abundant hydrocarbon in natural gas, is a potent greenhouse gas When news broke on September 26 that natural gas pipelines had ruptured under the Baltic Sea, the immediate-and appropriate-concern was the impact on the climate. Posted on 11 Oct 2022
How to study an underwater earthquake from shore
Lessons from a successful hybrid Sentry expedition A magnitude 6 earthquake along the Gofar Transform Fault in the eastern Pacific Ocean shook the seafloor in April 2020, just when a WHOI-based science team predicted. Posted on 31 Aug 2022
Seven ways you can be coral reef-safe
Lifestyle changes you can make to help corals in crisis Diving or snorkeling on a reef is your ticket to a dreamworld. Brilliant colors, fantastic shapes, and castle-like structures invite exploration, revealing bright flashes of fish and an infinite variety of life below the surface. Posted on 4 Jul 2022
World's largest kelp map launched
By Woods Hole Oceanographic Institution and collaborators Kelp forests provide myriad benefits to nature and people in oceans around the world. They form the backbone of the ecosystems in which they are found, providing habitat and food for thousands of species. Posted on 13 Apr 2022
Dissolving oil in a sunlit sea
Scientists working to understand a concept known as environmental fate The 2010 Deepwater Horizon oil spill was the largest marine oil spill in U.S. history. The disaster was caused by an explosion on the Deepwater Horizon oil rig, taking 11 lives and releasing nearly 210 million gallons of crude oil into the Gulf of Mexico. Posted on 20 Feb 2022
GJW Direct 2024 DinghyHenri-Lloyd - For the ObsessedCrewsaver 2021 Safetyline FOOTER