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Changing ocean currents driving extreme winter weather in US: Researchers



One researcher said the study was inspired by the cold weather in Texas in February. (Representative)


A conveyor belt of water runs throughout the Earth’s ocean. Its churning is driven by differences in water temperature and salinity, and weather patterns around the world are governed by its activity.

A pair of researchers studied the Atlantic portion of this worldwide conveyor belt called the Atlantic Meridional Overturning Circulation, or AMOC, and found that winter weather in the US is critically dependent on this conveyor belt-like system. As the AMOC slows due to climate change, the US will experience extreme cold weather.

The study, published in the journal ‘Communications Earth and Environment’, was led by Jianjun Yin, an associate professor in the University of Arizona Department of Geosciences, and co-author Ming Zhao, a geophysical physicist at the National Oceanic and Atmospheric Administration. Fluid Dynamics Laboratory.

AMOC works like this: warm water moves north into the upper Atlantic Ocean and releases heat into the atmosphere at higher latitudes. As the water cools, it becomes denser, causing it to sink into the deep ocean where it flows south.

“This circulation carries a huge amount of heat northward into the ocean,” Yin said. “The magnitude is on the order of 1 petawatt, or 10 to 15 power watts. Right now, the energy consumption by the entire world is about 20 terawatts, or 10 to 12 power watts. Therefore, 1 petawatt is enough to run about 50 civilizations.”

But as the climate warms, so does the ocean surface. At the same time, the Greenland ice sheet experiences melting, which flushes more freshwater into the ocean. Water heating and refreshing can both reduce the density of surface water and prevent water sinking, which slows AMOC. If the AMOC slows down, so does the heat transport to the north.

This is important because the equator receives more energy from the sun than the poles. Both the atmosphere and oceans perform the function of transporting energy from low latitudes to high latitudes. If the ocean cannot transport as much heat to the north, the atmosphere must instead transport more heat through more extreme weather processes at mid-latitudes. When the atmosphere moves heat north, cold air is displaced from the poles and pushed to lower latitudes, reaching south as far as the southern border of the Americas.

“Think of it as two highways connecting two big cities,” Yin said. “If one stops, the other gets more traffic. In the atmosphere, traffic is diurnal weather. Therefore, if ocean heat transport slows or stops, the weather becomes more extreme.”

Yin said the study was inspired by the extremely cold weather Texas experienced in February.

“In Houston, daily temperatures dropped to 40 degrees Fahrenheit above normal,” Yin said.

“It’s the typical range of summer/winter temperature differences. It made Texas feel like the Arctic. This type of extreme winter has happened several times in the US in recent years, so the scientific community is trying to understand the mechanism behind it.” Working. Extreme Events.”

The crisis in Texas caused widespread and devastating power outages, and the National Oceanic and Atmospheric Administration estimated the socioeconomic damage totaled $20 billion. Yin was curious about the role of the ocean in the phenomenon of extreme weather.

Yin and Zhao used a state-of-the-art, high-resolution global climate model to measure the impact of the AMOC on the extreme cold climates of the US.

He ran the model twice, first considering today’s environment with a working AMOC. They then adjusted the model by inputting enough freshwater in the high-latitude North Atlantic to turn off the AMOC. The gap revealed the role of the AMOC in extremely cold climates. They found that without the AMOC and its northward heat transport, extreme cold winter weather intensifies in the US.

According to recent observational studies, the AMOC has weakened over the past decades. Climate models predict that it will weaken further in response to an increase in greenhouse gases in the atmosphere.

“But there is uncertainty about the magnitude of the weakening, because at this point, we don’t know how much of the Greenland ice sheet will melt,” Yin said. “How much it melts depends on greenhouse gas emissions.”

Yin said the researchers didn’t even take into account the effects of human-caused global warming in their model, but it remains an area of ‚Äč‚Äčinterest for the future.

“We basically turn off the AMOC (in the model) to look at the response to extreme weather. Next, we want to factor in greenhouse gases and the combined effects of AMOC slowdown and global warming in extreme cold weather.” want to see,” concluded Yin.

(Except for the title, this story has not been edited by NDTV staff and is published from a syndicated feed.)


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