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Recent studies have found that the AMOC is approaching a collapse sooner than expected, prompting concerns over unstable weather patterns, rising in sea levels, and critically, national security threats.
When we think of climate change, we usually think about increased heat and the resulting melting ice sheets.
In recent times, it has been made clear that the Earth’s very dynamics are being shifted tremendously by the actions of humans, and this time it involves the Atlantic Meridional Overturning Circulation (AMOC).
Think of the AMOC as a giant ocean conveyor belt beginning of the coast of the Eastern US coast, where warm, salty water is carried north into the North Atlantic. As it travels, it releases heat into the atmosphere, which prevailing winds then carry towards Western Europe, which explains why it has milder winters than places like Canada at similar latitudes.
The water continues north into the Nordic Seas, where it cools in contact with frigid Arctic air. Thus, as it loses heat, it becomes denser, and combined with its salinity, begins to sink. From there, it doesn’t stop. It flows southward along the ocean floor as a deep, cold current moving at depths of about 1,200 to 4,000 meters. Eventually, it gradually warms, rises back to the surface and the cycle begins again.
However, experts have repeatedly warned that the rising global temperatures are heating ocean surfaces, and melting record volume of Arctic ice, primarily in Greenland. This causes all that melted ice water to come flooding into the North Atlantic with warm, fresh water, and a double-edged sword.
The melted ice water is no longer cold or salty enough to become dense and sink, causing the gravity-driven current to lose its momentum. As the current slows, it carries less salt from the south to the north, creating a feedback look that further destabilised the system. This is where two recent studies come into play.
What do the new studies tell us?
The first study published on 8th April sought to examine the health of the AMOC, particularly its western boundary, near North America and the Caribbean. By analysing data from deep-sea monitoring stations spanning from Florida to Canada, they discovered something alarming.
Over the last 20 years, the strength of deep-sea currents in the region has been steadily and consistently declining, and this was happening at every location they measured. What’s more is that the observed decline in these western currents is more significant than what current climate models have been predicting for the overall AMOC.
Just a week after this study was published, a second followed. This time, researchers took on a different angle, using mathematical models to project the future trajectory of the AMOC. Their method involved looking at where current models are getting the present-day ocean wrong and correcting them using real-world data.
They revealed a far more severe outlook: while earlier models projected a 32% weakening of the AMOC, the corrected model indicated a far dramatic steeper decline of 51%.
Putting both studies together, one thing is made clear; if the AMOC continues to weaken, it will end up collapsing much earlier than previously estimated.
