Ocean currents slow down due to climate change

Well, new research reveals that Earth’s major ocean currents are slowing down, and while the consequences won’t be as immediate or dramatic as in Hollywood fiction, there are real-world impacts to global weather patterns and levels of weather. sea.

“It has been predicted, basically, for decades that this circulation would weaken in response to global warming. And now we have the strongest evidence that this is already happening,” said Stefan Rahmstorf of the University of Potsdam, who contributed to this research.

The Atlantic South Circulation Circulation (AMOC) transports water through the planet’s oceans, including the Atlantic, Pacific and Indian Oceans. The region contributing to the slowdown is the North Atlantic, according to the research.

“The idea (of this movie), which is actually correct, is that if this tipping circulation of the Atlantic breaks down completely, this will lead to severe cooling around the North Atlantic, especially in Europe, in the kind of coastal areas (of) Britain and Scandinavia. But that’s only true if the capsize completely collapses, “Rahmstorf said.

South Atlantic Ocean Circulation Map
In this part of the ocean, Greenland’s ice sheets are melting, contributing both to rising sea levels and slowing circulation.

“This indicates that the slowdown is probably not a natural change, but the result of human influence. The AMOC has a profound influence on global climate, and particularly in North America and Europe, so this evidence of continued weakening New evidence for the interpretation of future regional and global climate projections is critical new evidence for circulation, “said Andrew Meijers, deputy scientific director for polar oceans at the British Antarctic Survey.

Thaw in Greenland and heavy rains over the North Atlantic induced by climate change have affected the salinity and density of the waters, Rahmstorf explained.

“Both surface warming and increased water cycling, increased rainfall and melting ice are a consequence of global warming” in parts of the North Atlantic Ocean, he said.

As warm water currents move north, they generally return south as it gets colder and heavier. The addition of fresh water from the melting ice slows down this turn due to reduced salinity.

Deviations of the current sea surface temperature from normal indicate the cold puddle in parts of the North Atlantic Ocean.  The arrows show the overall Atlantic Southern Roll-Over Circulation.
“This weakening also leads to cold in the North Atlantic, but it is confined to the ocean. This cold drop, as we call it, is over the ocean and does not touch land areas,” Rahmstorf said. Current estimates show that this weakening is moderate, about 15% weaker compared to normal, and are based on data analyzed up to 1,600 years ago.
This color-coded map shows a progression of changing global surface temperature anomalies.  Normal temperatures are the average over the 30-year reference period from 1951 to 1980. Higher-than-normal temperatures are shown in red and lower-than-normal temperatures are shown in blue.  The image represents the five-year global temperature anomalies from 2016 to 2020. The scale is in degrees Celsius.

East Coast of the US To See Higher Sea Levels

One of the main impacts of the slowdown in ocean circulation is on sea levels, especially those on the east coast of the United States.

“The flow from the surface to the north of the AMOC leads to a deflection of the water masses to the right, away from the east coast of the US. This is due to the rotation of the Earth that deflects moving objects , like currents, to the right in the northern hemisphere and to the left in the southern hemisphere. As the current slows, this effect weakens and more water can accumulate on the east coast of the US. leading to a further rise in sea level, “said Levke Caesar, one of the report’s authors.

Sea level rise is already occurring due to factors such as melting ice sheets and warming oceans. According to the National Oceanic and Atmospheric Administration (NOAA), water levels have risen 8 to 9 inches on average in the last 140 years.

The rate at which these waters are rising has also increased in recent years.

“The rate of global sea level rise more than doubled from 1.4 mm per year for most of the 20th century to 3.6 mm per year between 2006 and 2015,” said NOAA.

A further slowdown in global ocean circulation, especially along the crucial Gulf Stream current off the east coast of the US, could combine with already accelerated sea level rise to make major Northeast cities are even more vulnerable to flooding.

Hotter heat waves, stronger hurricanes

Global weather patterns are critically related to ocean circulations and their transport of heat and nutrients around the planet.
An increase in heat waves in Europe and stronger hurricanes closer to the coast of the United States because warmer water moves closer to shore may be related to ocean circulation, Rahmstorf said.

“The seven warmest years in the world have occurred since 2014, and 10 of the warmest years have occurred since 2005,” NOAA said. Heat waves are already more and more frequent.

The ocean and currents also play a role in absorbing carbon dioxide, the most dominant greenhouse gas, from the atmosphere. The changing currents could decrease the amount of carbon that is removed from the atmosphere, according to NASA.

In addition to the people affected, the marine biology population is also at risk.

Marine organisms “are highly dependent on these ocean currents, which basically set the conditions for the entire ecosystem in terms of nutrient supply, temperature and salinity conditions,” Rahmstorf said.

When asked if the AMOC could slow further or even stop, Rahmstorf said that climate models suggest that currents will slow by between 34% and 45% by 2100.

“Despite a lot of research in the last decade on this, it is very difficult to quantitatively pinpoint how far this tipping point is. But the kind of model simulations that I am aware of suggest that if you weaken this circulation by about half, they are entering into a critical state. And then this could very well … happen by the end of the century, “Rahmstorf said.

“We should (strive to) stay well away from that tipping point because the consequences if circulation were to completely collapse would be really dramatic.”

Hollywood has shown us this possible worst-case scenario for climate change. And while the consequences depicted in “The Day After Tomorrow” are highly unlikely, they illustrate how the runaway impacts of climate change could occur if we don’t listen to warnings from climate scientists.


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