Gulf Stream is weakest in more than 1,000 years, study finds

This Tuesday, November 10, 2020, the satellite image made available by NOAA shows Tropical Storm Eta at 10:40 am EST in the Gulf of Mexico, Theta, on the right, and a tropical wave to the south that became in Tropical Storm Iota. An overheated world erased weather records in 2020, an extreme year of hurricanes, wildfires, heat waves, floods, droughts and melting ice, the United Nations weather agency reported Wednesday, December 2, 2020 (NOAA via AP ).

A group of scientists from Europe presented new research this week stating that the Gulf Stream is weaker now than it has been at any time in the last 1,000 years. The Gulf Stream is an Atlantic Ocean current that plays a largely hidden role in shaping weather patterns in the United States. Much has been researched and learned about the influential stream over the past 500 years, particularly due to the experience of one of America’s Founding Fathers, Benjamin Franklin.

But in recent decades, a change in the circulation of the Gulf Stream has weakened more than at any other time in the last millennium, according to a recently published study by scientists from Ireland, Britain and Germany. The weakening of the Gulf Stream, formally known as the Atlantic Southern Reversal Circulation (AMOC), can be attributed primarily to one catalyst, the researchers said: human-caused climate change.

The current of the Gulf Stream moves an enormous amount of water through the Atlantic Ocean. According to Stefan Rahmstorf, one of the study’s authors, it moves almost 20 million cubic meters of water per second, acting like a giant conveyor belt.

How strong is that current? “Almost a hundred times the flow of the Amazon,” he told the Potsdam Institute.

The location of the Gulf Stream in the 2016 Global Real-Time Ocean Forecast System (RTOFS) model. (Image via NOAA)

The main function of the Gulf Stream is to redistribute heat on Earth through the ocean current. The oceanic circulatory system plays a crucial role in many weather patterns around the world, particularly along the east coast of the United States.

Rahmstorf said his team’s research was pioneering in being able to combine earlier pieces of research to reconstruct a 1,600-year-old picture of AMOC’s evolution.

“The results of the study suggest that it has been relatively stable until the end of the 19th century,” he said. “With the end of the little ice age around 1850, ocean currents began to decline, with a second more drastic decline since the mid-20th century.”

An original 1768 mapping of the Gulf Stream by Timothy Folger and Benjamin Franklin. (Image via Library of Congress)

So what are the implications of this decline in ocean currents? AccuWeather senior meteorologist Bob Smerbeck said it could lead to sea level rise if water levels warm this year. However, Smerbeck added that it is difficult to know how warm the waters could get.

Previously, studies had shown that rising water temperatures and rising sea levels can lead to more extreme weather events, such as stronger tropical storms, a greater likelihood of extreme heat waves, or a decrease in summer rainfall. .

However, other researchers have also obtained contrasting data, suggesting that the Gulf Stream has not actually decreased in the past 30 years. Using a different data modeling system, researchers from the UK and Ireland assembled data from climate models that they said in a study published earlier this month showed “no overall decrease in AMOC.”

“Our results reinforce that adequately capturing changes in the deep circulation is key to detecting any AMOC decline related to anthropogenic climate change,” the authors write in their study, which was written just days before Rahmstorf’s team published their research on the subject.

Smerbeck, who has been a meteorologist at AccuWeather for nearly 25 years, urged caution in interpreting the claims of the new research.

“A possible repercussion discussed in article 1 [the first study mentioned above] on warming of the waters along the east coast due to a slowdown in AMOC could lead to a rise in sea level due to the thermal expansion of seawater. This seems plausible, “Smerbeck said. But he added that the amount of seawater would increase will depend on how warm the waters could get, and he wasn’t ready to speculate on that.

This undated engraving shows the scene from July 4, 1776, when the Declaration of Independence was passed by the Continental Congress in Philadelphia, Pennsylvania. The document, written by Thomas Jefferson, Benjamin Franklin, John Adams, Philip Livingston and Roger Sherman, announces the separation of 13 British North American colonies from Great Britain. The formal signing by 56 members of Congress began on August 2 (AP Photo)

How was the Gulf Stream as we know it today discovered? Well, the discovery was driven by the need for greater efficiency with the mail service and was inspired by the empiricism of the whalers.

In 1768, Benjamin Franklin was working in London as an assistant postmaster, according to The Smithsonian Magazine, responsible for overseeing the arrival of mail to and from the American colonies. His cousin, Timothy Folger, was working as a captain on a merchant ship at the same time.

One day Franklin asked Folger why his merchant ships reached the colonies so much faster than Franklin’s mail ships returned to England. Folger explained to his cousin that merchant captains followed the advice of whalers, who followed a “strong, warm current” to track and kill whales.

While Franklin said the post captains were too proud to take the advice of “ordinary American fishermen,” sailing against the current cost precious time, according to author Laura Bliss.

So Folger outlined a general stream location for Franklin, naming it “Gulph Stream.” However, Franklin’s postmen refused to follow the instructions.

A graph of the Gulf Stream, published in 1786 in Transactions of the American Philosophical Society. (Image via Library of Congress, Division of Geography and Maps)

But when Franklin shifted his allegiance to the burgeoning America during the Revolutionary War, he mapped out a more precise route from the AMOC and gave it to the French allies, giving them a key advantage in the battle of the European maritimers, according to The Smithsonian. The combination of Folger’s whaling knowledge and Franklin’s mapping would become crucial in later understanding the importance of the current, even if they were originally just trying to figure out how to deliver mail faster.

While knowledge of the AMOC can only go back a few hundred years, Smerbeck said that the dating of streams can be done in different ways. Direct measurements with deep-sea instruments only date back to 2004, he said, but other methods can help piece the puzzle, such as coral analysis and historical data from ship records.

“Tree rings can tell how wet or dry the nearby terrestrial climate was in the past, which may be related to sea surface temperatures,” Smerbeck explained. “Ice cores can say pretty much the same thing, as well as how hot or cold it was in the past,” he said. “Ocean sediments can show whether there were high or low periods of runoff from nearby rainfall on land, which could be related to how warm or cold sea surface temperatures were in the past.” Researchers have used all of these clues to inform their understanding, dating back more than a millennium, that they have developed of the Gulf Stream.

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