Major North Atlantic Ocean circulation system is weakening

By Brett Anderson, AccuWeather senior meteorologist

4/12/2018, 11:05:35 AM

Share this article:

New research just published in the journal Nature shows that the Atlantic Meridional Overturning Circulation (AMOC) has slowed down (weakened) since the mid-20th century and that it may have reached a new record low. Ocean observations go back to 1870.

What is the AMOC?

The AMOC is a large-scale system of ocean currents that circulates warm, salty water from the South Atlantic and tropics via the Gulf Stream to the colder North Atlantic. There, warm salty waters cool, release heat and eventually sink to the deep ocean and move south. The AMOC plays a key role in the Earth's climate and is a major component of the Global Conveyor Belt. (via NOAA).)

Image courtesy Wikipedia.

The international research team that conducted this study used computer model simulations to reconstruct changes in the AMOC over time. By comparing these simulations with recent direct ocean measurements, they were able to conclude that the AMOC slowed down by about 15 percent since the 1950s.

Why has it slowed down?

The research team noted that rising levels of atmospheric CO2 may be responsible for this change.

Impacts of this change

The waters along the NE U.S. shelf and Gulf of Maine have warmed 99 percent faster then the global oceans as a whole over the past 10 years.

The slowing of the AMOC is also having an impact on the distributions of fish and their prey, according to the NOAA Fisheries Service report.

The research team was able to find a characteristic sea surface temperature fingerprint for an AMOC slowdown, according to Vincent Saba, a research fishery biologist at NOAA's NE Fisheries Science Center and co-author of the study.

Key excerpts from the report.........

“That fingerprint consists of a pattern of cooling in the North Atlantic Ocean’s subpolar gyre and a warming in the Gulf Stream region due to reduced northward heat transport and an associated northward shift in the Gulf Stream,” Saba said. “In other words, there is warming along the Northeast U.S. Shelf and Gulf Stream region, and at the same time a cooling in the North Atlantic subpolar gyre.”

Continued warming is likely to further weaken the AMOC in the long term, through changes to the hydrological cycle, sea-ice loss, and accelerated melting of the Greenland Ice Sheet, all of which are causing the North Atlantic to become fresher and less dense. “If the AMOC continues to weaken,” Saba said, “ocean temperature along the Northeast U.S. Shelf is expected to continue its trend of warming faster than the global ocean, which will further impact fisheries and living marine resources in the region.”

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com

Comments

Comments that don't add to the conversation may be automatically or manually removed by Facebook or AccuWeather. Profanity, personal attacks, and spam will not be tolerated.

Global climate change

Increase in extreme precipitation events in the northeastern US over the past 22 years

Global climate change - August 10, 2018, 1:23:08 PM EDT

There has been a 53-percent increase in extreme precipitation events in the northeastern United States since 1996.
Ocean acidification likely to get worse as atmospheric CO2 steadily climbs

Global climate change - August 03, 2018, 12:59:28 PM EDT

Increasing global CO2 emissions are continuing to lower the pH of the oceans.
Flash flood risk has increased over the past 50 years in Australia

Global climate change - July 31, 2018, 2:20:30 PM EDT

New research has found that there has a been an increase in short, intense rain events over Australia during the past 50 years.
June 2018 ranked in the top five warmest on record

Global climate change - July 27, 2018, 2:32:55 PM EDT

June was another abnormally warm month globally.
Atlantic Ocean circulation slowdown is likely part of a longer-term cycle

Global climate change - July 25, 2018, 2:06:50 PM EDT

New research has determined that this slowdown of the AMOC is not caused by global warming but is part of a decades-long cycle that will have an impact on temperatures in the coming decades.
Annual winter maximum ice cover trend on the Great Lakes since the 1970s

Global climate change - July 18, 2018, 10:51:54 AM EDT

Data indicates that there has been a slight downward trend in the annual maximum extent of Great Lakes ice cover since the 1970s.
Future global warming may be double than what current climate models predict

Global climate change - July 10, 2018, 12:03:02 PM EDT

A new study concludes that global warming may eventually be twice as warm as what current climate model consensus indicates.
Air pollution from increased use of air conditioning may worsen in a warming world

Global climate change - July 06, 2018, 1:22:01 PM EDT

The increased use of air conditioning in a warming world may lead to a significant degradation of air quality in the eastern U.S. by mid-century.