Monitoring Ocean Currents for Environmental Changes

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Researchers have suggested that the Atlantic Meridional Overturning Circulation (AMOC), a major current that influences global weather patterns and temperatures, may be approaching a tipping point that would lead to its collapse.

The AMOC, which carries warm water north and cool water south, is currently in its weakest state in over a millennium due to increased freshwater entering the Atlantic and warming temperatures. The study, published in Science Advances, found that the introduction of freshwater over time would lead to a slow decrease before reaching a tipping point that would lead to a sudden collapse of the current’s flow. The study’s lead author, René Van Westen, stated that recovering the AMOC back to its present-day state would be difficult and irreversible on human time scales.

The Atlantic Ocean Current (AMOC) could cause significant climate change if it were to stop. David Thornalley, a professor of ocean and climate science at University College London, predicts that if the AMOC were to stop, it would result in cooling of several degrees across the northern hemisphere, shifting tropical rainfall belts, and changing rainfall patterns. He also suggests that European cities would not reach above freezing year-round, putting the continent into a localized Ice Age.

Amazon rain patterns will change, with less precipitation in early months. North America will experience slightly lower temperatures, with more precipitation in winter and less in summer. A collapse in AMOC would cause a southward shift in atmospheric circulation belts and strengthen some features, such as the westerly winds coming off the Atlantic to the UK. The inter-tropical convergence zone would shift south, causing southern subtropical areas to receive tropical rainfall and parts of the tropics to dry out, negatively impacting agriculture and water supplies.

The Atlantic Ocean Current (AMOC) is expected to tip over in the next century, according to a study by the University of California, Berkeley. The study found that the strength of the AMOC decreases with the addition of freshwater, with its strength expected to drop to 2 Sverdrups within a hundred years.

Salinity transport across a specific Atlantic latitude indicates the strength of the AMOC, reaching a minimum 25 years before the tipping point. Although a study suggests it could occur this century, the likelihood remains a topic of ongoing discussion. Professor of oceanography at the Massachusetts Institute of Technology, Rafael Ferrari, expressed uncertainty about the imminence of such a tipping point, citing a recent report by the Intergovernmental Panel on Climate Change, which concluded that a collapse before 2100 was unlikely. However, Thornalley noted that IPCC models often struggle to accurately simulate key ocean processes and may be biased to be too stable.

Climate change is more likely to cause a significant weakening of the Atlantic Current (AMOC), according to experts and the IPCC. Warming global temperatures lead to more sea ice melting and increased precipitation near the Arctic, putting more freshwater into the ocean. This prevents water from sinking and forms a colder, deep flow that transports water south.

While a warmer atmosphere may see more evaporation from the ocean, freshwater entering the oceans and ocean warming in places like the Arctic prevents water from sinking. Scientists agree that curbing greenhouse gas emissions would avoid further destabilization of the major current. Researchers suggest the AMOC may have collapsed during the last Ice Age, but it’s not enough to restore the pre-collapse freshwater budget once it transitions to a collapsed state.