Global climate change
Atlantic Ocean circulation slowdown is likely part of a longer-term cycle
By Brett Anderson, AccuWeather senior meteorologist
7/25/2018, 2:06:50 PM
Recent studies have shown that the Atlantic Meridional Overturning Circulation (AMOC) has steadily slowed over the past decade.
Image courtesy NOAA.
New research from the University of Washington and the Ocean University of China has determined that this slowdown 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.
The Atlantic Meridional Overturning Circulation, or AMOC, is a conveyor belt that brings surface water northward in the Atlantic; from there, the heavier salty water sinks and returns at depth from the Labrador and Nordic seas, near the North Pole, all the way south to the Southern Ocean, according to the University of Washington News report.
The research team found that through direct measurements the AMOC has declined 10 times more than expected since 2004.
Below are some excerpts from the UW News report.....
“Many have focused on the fact that it’s declining very rapidly, and that if the trend continues it will go past a tipping point, bringing a catastrophe such as an ice age. It turns out that none of that is going to happen in the near future. The fast response may instead be part of a natural cycle and there are signs that the decline is already ending," said co-author Ka-Kit Tung, a UW professor of applied mathematics with an adjunct appointment in atmospheric sciences.
The AMOC's speed has a key role in the amount of surface warming. If the current slows down, then it stores less heat and the Earth will experience a high rate of temperature increase than what we have seen since 2000.
When the current is faster, more of the warm, salty tropical water travels to the North Atlantic. Over years this causes more glaciers to melt, and eventually the freshwater makes the surface water lighter and less likely to sink, slowing the current.
When the AMOC is in a slow phase, the North Atlantic becomes cooler, icemelt slows, and eventually the freshwater melt source dries up and the heavier saltier water can plunge down again, which speeds up the whole circulation.
From 1975 to 1998 the AMOC was in a slow phase, which allowed excess heat to accumulate in the atmosphere. The AMOC shifted to a fast stage at the start of this century, which allowed excess heat to remain trapped in the deep oceans.
In conclusion, the study argues that the AMOC is not collapsing as some earlier studies have suggested, but is currently transitioning from a fast phase to a slower one.
This study was published in the journal Nature.
The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or AccuWeather.com
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
Global climate change - February 20, 2019, 9:24:53 AM EST
More energy is getting shifted to help fuel more thunderstorms, which is leading to less energy being available for much larger, summertime extratropical storms.
Global climate change - February 13, 2019, 12:58:22 PM EST
Many U.S. cities may have climates more like those that are currently hundreds of miles to the south by the end of the century.
Global climate change - February 06, 2019, 9:02:22 AM EST
Warming of the tropical oceans due to climate change may cause a substantial increase in the frequency of extreme rainstorms by the end of this century.
Climate change unlikely to have much influence on the occurrence of extreme Northeast U.S. snowstorms
Global climate change - January 29, 2019, 11:29:39 AM EST
Climate change likely to reduce number of moderate nor'easters, but not extreme nor'easters.
Global climate change - January 23, 2019, 1:42:03 PM EST
New research from the Ohio State University has determined that the Greenland ice sheet is melting at a quicker rate than scientists previously thought.
Global climate change - January 16, 2019, 1:55:15 PM EST
Warming of the oceans is accelerating