The Atlantic Meridional Overturning Circulation (AMOC) may face weakening due to freshwater influx from Greenland’s snowmelt. However, cutting-edge climate models indicate this slowdown is likely to be gradual and reversible if global warming is curbed.

AMOC is a critical ocean current system that conveys warm, salty water from the tropics to the North Atlantic. There, it cools, sinks, and circulates back southward along the ocean floor. The influx of fresh meltwater from Greenland’s ice sheet appears to be mixing with denser seawater, slowing its downward flow.

<p>Recent estimates indicate Greenland is losing approximately <a href="https://www.nature.com/articles/s41586-023-06863-2">30 million tons of ice</a>. Some experts express concerns that AMOC could undergo a sudden and irreversible collapse, potentially plunging Europe into near-Arctic conditions. One <a href="https://iopscience.iop.org/article/10.1088/1748-9326/adfa3b">study</a> suggests that AMOC might cross a crucial tipping point within decades.</p>
<p>However, modeling by <a href="https://research-portal.uu.nl/en/persons/oliver-mehling/">Oliver Mehring</a> and colleagues at Utrecht University revealed that while AMOC may weaken steadily under ongoing global warming, it is unlikely to reach a point of no return solely due to Greenland’s snowmelt.</p>
<p>“The prevailing notion that melting from the Greenland ice sheet could trigger an irreversible AMOC collapse is a significant oversimplification,” stated Mehring. “The snowmelt from Greenland alone is insufficient to push AMOC past its tipping point.”</p>

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<p>It is believed that atmospheric warming not only accelerates Greenland's melting but also directly undermines the AMOC by preventing brine in the North Atlantic from cooling adequately. This warming allows the ocean to hold more freshwater, which ultimately leads to increased rainfall, diluting saltwater, and reducing ocean mixing. This combination of warming and freshwater influx diminishes the sinking action crucial to AMOC.</p>

<p>While most predictive models of future climate change concentrate on atmospheric warming's impact on AMOC, <a href="https://research-portal.uu.nl/en/persons/oliver-mehling/">Mehring</a> and his team found that atmospheric warming could weaken AMOC by a staggering 60% by 2300. If the volume of Greenlandic snowmelt were to increase, the AMOC's strength could diminish by an additional 20%.</p>

<p>Nonetheless, their research indicates that if atmospheric CO2 levels were to decrease by 1% annually starting in 2250, AMOC could fully recover by around 2400. Although these models are not designed to predict the exact timeline or extent of AMOC changes, they imply that increased freshwater input from Greenland won't lead the AMOC over the tipping point.</p>

<p>A reduction of 80% in AMOC could still lead to crop failures in Western Europe, ice formation in the North Sea, and disruption of tropical monsoon patterns. Fortunately, the study indicates that such declines would be gradual, predictable, and reversible if humanity ceases fossil fuel combustion. As <a href="https://www.bas.ac.uk/profile/lsim/">Louise Sim</a> from the British Antarctic Survey commented, "While scenarios of AMOC crashing are conceivable, they are unlikely to occur. Instead, AMOC shows a strong linear relationship with cumulative CO2 emissions."</p>

<p>Despite these findings, the possibility of a tipping point cannot be completely dismissed. Previous research conducted by <a href="https://www.uu.nl/staff/RMvanWesten">René van Westen</a> and colleagues at Utrecht University, using a different model, suggested that significant melting from Greenland could lead to AMOC's irreversible collapse. However, this model applied meltwater at a constant rate rather than simulating the gradual increases observed in reality.</p>

<p>“Other climate models have predicted crossings of the tipping point under 21st-century climate change, illustrating that results can be model-dependent,” van Westen remarked.</p>

<p>In addition to Greenland’s melting, several other climate changes pose risks to the AMOC. For instance, freshwater from Antarctic snowmelt could disrupt global circulation dynamics, of which AMOC is a vital component. However, the impacts remain uncertain; depending on the timing of Antarctic melt, it could also help sustain the AMOC.</p>

<p>This new study does not eliminate the risk of an AMOC tipping point but contributes valuable insights to the ongoing climate discussion, highlighted <a href="https://scholar.google.com/citations?user=Cn7wuysAAAAJ&amp;hl=en">Jonathan Baker</a> from the UK’s Met Office.</p>

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