Driven by climate change, a crucial system of ocean currents is heading for a complete collapse
According to new calculations from the University of Copenhagen, important ocean currents that redistribute heat, cold, and precipitation between the tropics and northernmost parts of the Atlantic region will stop around 2060.
A recent study by researchers from the University of Copenhagen’s Niels Bohr Institute and Department of Mathematical Sciences predicts that if we continue to emit the same levels of greenhouse gases as we do today, the system of ocean currents that currently distributes cold and heat between the North Atlantic region and tropics will completely stop. Because the system is part of a larger, global system of ocean circulation, the collapse could cause severe disruption of weather patterns across the planet.
Using advanced statistical tools and ocean temperature data from the last 150 years, the researchers calculated that the ocean current, known as the Thermohaline Circulation or more specifically, the Atlantic Meridional Overturning Circulation (AMOC), will collapse between 2025 and 2095 with 95 percent certainty. This could result in major challenges, such as warming in the tropics, increased storminess in the North Atlantic region, and a cascading effect with unpredictable ramifications. The collapse is most likely to occur in 34 years, in 2057.
Professor Peter Ditlevsen from the Niels Bohr Institute said:
“Shutting down the AMOC can have dire consequences for Earth’s climate, for example, by changing how heat and precipitation are distributed globally. Our result underscores the importance of reducing global greenhouse gas emissions as soon as possible.
The calculations, just published in the renowned scientific journal, Nature Communications, contradict the message of the latest United Nations’ Intergovernmental Panel on Climate Change (IPCC) report, which, based on climate model simulations, considers an abrupt change in the thermohaline circulation unlikely during this century.
What is the Atlantic Meridional Overturning Circulation or Thermohaline Circulation?
The Atlantic Meridional Overturning Circulation (AMOC) is an ocean current system that plays a crucial role in redistributing heat from the tropics to the northernmost regions of the Atlantic, primarily to Western Europe. This system of currents helps to regulate the climate in the North Atlantic region, creating a relatively mild climate compared to other regions at similar latitudes.
The AMOC works by transforming surface water into deep, southbound ocean currents, creating room for additional surface water to move northward from equatorial regions. In this way, the AMOC helps to distribute heat, cold, and precipitation between the tropics and the northernmost parts of the Atlantic region. The circulation in the northernmost latitudes is particularly important for maintaining the relatively mild climate of the North Atlantic region.
The AMOC has been operating the way since the last ice age, when the circulation collapsed. There have been 25 abrupt climate changes between the present state of the AMOC and the collapsed state, which were associated with ice age climate. These are called the Dansgaard-Oeschger events, which were first observed in ice cores from the Greenlandic ice sheet. During these events, the climate changes were extreme, with 10-15 degree changes within a decade, while the current climate change is only 1.5 degrees warming over a century.
The collapse of the AMOC is predicted to occur between 2025 and 2095 with 95 percent certainty, according to recent calculations from the University of Copenhagen. This prediction is based on advanced statistical tools and ocean temperature data from the last 150 years, and it indicates that if greenhouse gas emissions continue at their current levels, the system of ocean currents that currently distributes cold and heat between the North Atlantic region and tropics will completely stop by 2060.
Early warning signals present
The researchers developed their prediction based on observations of early warning signals exhibited by unstable ocean currents. While these Early Warning Signals have been reported previously, it is only now that advanced statistical methods have made it possible to predict the timing of the collapse.
To analyze the strength of the Atlantic Meridional Overturning Circulation (AMOC), the researchers looked at sea surface temperatures in a specific area of the North Atlantic from 1870 to the present day. These sea surface temperatures act as “fingerprints” that indicate the AMOC’s strength, which has only been directly measured for the past 15 years.
Professor Susanne Ditlevsen of UCPH’s Department of Mathematical Sciences, explained:
“Using new and improved statistical tools, we’ve made calculations that provide a more robust estimate of when a collapse of the Thermohaline Circulation is most likely to occur, something we had not been able to do before.”
Image Credits
In-Article Image Credits
Pattern of thermohaline circulation also known as meridional overturning circulation via Wikimedia Commons with usage type - Creative Commons License. October 21, 2009Featured Image Credit
Pattern of thermohaline circulation also known as meridional overturning circulation via Wikimedia Commons with usage type - Creative Commons License. October 21, 2009
