The Gulf Stream is on the brink of collapse: what are the consequences

Such a collapse would have a disastrous impact on global weather systems. A new analysis of the Atlantic Meridional Overturning Circulation revealed that it would suffer "an almost complete loss of stability."

One of the most important ocean current systems for regulating climate in the Northern Hemisphere could be on the brink of total collapse due to climate change. The revelation comes from a new analysis of the Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream and is responsible for moderating much of the world's climate, which would have suffered "an almost complete loss of stability over the last century." Author of the study is Niklas Boers, a researcher at the Potsdam Institute for Climate Impact Research in Germany.

The Collapse of the Gulf Stream and its Consequences

Currents function as a conveyor belt that carries warm, salty water northward from the tropics and cold water southward along the sea floor. This giant "ribbon" had already shown itself to be at its weakest point, but now it may have reached total collapse. Such a collapse would have a disastrous impact on global weather systems, leading to rising sea levels in the Atlantic, increased cooling and more powerful storms across the Northern Hemisphere. According to the U.K. Meteorological Office it would also bring a severe disruption of rain essential for growing crops in Africa, South America and India.

For Niklas Boers, "the results support the assessment that the AMOC decline is not just a fluctuation or linear response to rising temperatures, but probably means that we are approaching a critical threshold beyond which the circulation system could collapse." Data from past analyses show that the AMOC can exist in two stable states: a stronger, faster state that humans currently rely on and another that is much slower and weaker. According to Boers, the existence of the two states implies that "abrupt transitions between the two circulation modes are possible in principle."

This means that the current could weaken to a tipping point, moving from the stronger to the weaker state that could rapidly transform the climate across the Northern Hemisphere leading it to become much less temperate than it is today. The new study is attempting to understand whether the recent weakening of the AMOC means it will simply circulate a little slower, but in a way that humans can control through reduced carbon emissions, or whether it is about to transform into a permanently weaker form that could not be reversed for hundreds of years.

The density of the ocean's water depends largely on its temperature and salinity. Currently, the saltier southern part of the current becomes colder - and therefore denser - as it approaches the northern part. The additional density contributed by the salt allows the southern water to sink below the less salty northern water, consequently pushing it southward in an infinite global conveyor. Now, warmer temperatures and increased freshwater inflow caused by melting glaciers have made the water warmer and less salty, and the current is becoming less dense and less able to sink. It is this very condition that could threaten to halt the entire flow of the AMOC and create a devastating and irreversible change in global climate systems.

With respect to climate change, researchers at Anglia Ruskin University in Cambridge have instead analyzed which place has the greatest potential to withstand the crisis caused by global warming and have identified New Zealand as the best place to survive an apocalypse.

Stefania Bernardini