Imagine the water circulation system of a swimming pool. Water is drawn into filters around the pool’s edge, stripped of debris, and then the cleaned water is pumped back into the pool, restarting the cycle. If the filtration system got shut off the water would quickly fill with dead bugs and leaves, grow stagnant, and create an environment ripe for algae and mosquitos. Tens of thousands of swimming pools abandoned during the U.S. housing crises created a public health hazard and helped mosquito-borne diseases like West Nile and Zika spread like wildfire across the southern states.
Now imagine turning off the pool filter for the ocean.
The Atlantic meridional overturning circulation (AMOC) is the “pool filter system” for the Atlantic and an integral part of the world’s ocean system, the Thermohaline circulation. Cold, saline-heavy water sinks in the North Atlantic, which pulls warmer seawater from off the coast of Africa, transferring heat to Western Europe and nutrients to marine life, and captures carbon dioxide from the atmosphere as a side benefit. However, fresh water from the rapidly melting glaciers in Greenland is diluting the saltwater of the North Atlantic, disrupting the cycle. Scientists have long worried about a slowdown in this critical system and a report published in the journal Nature presented data on how the Atlantic current has weakened by as much as 15 percent since the mid-20th century. If the AMOC continues to weaken it will certainly have a global impact.
What are the potential scenarios? The mild climate of western Europe could cool by 5° to 10° C, sea levels could rise faster and higher along the Eastern Seaboard of North America, rainfall volumes from monsoons in India and Asia could decrease, food sources for key species like plankton could evaporate, the severity and occurrence of Atlantic storms might increase, and an ice age could possibly be kicked off in the Northern Hemisphere—though not as swift or dramatic as depicted in the disaster movie, The Day After Tomorrow. The significant shift in temperature would impact the climate, agriculture, fishing regions when large fish leave to find new food sources, and create waves of climate refugees, possibly destabilizing countries. We had a preview of this when over a million Syrian refugees flooded into Europe.
While this is a forecast, meaning it is a potential outcome, scientists have looked to the past to determine these future scenarios. According to paleoclimate markers compiled from sedimentary core samples, the last time AMOC was this weak was 1,600 years ago at the end of the “little ice age” when a warming climate melted glacial ice and caused the slowdown in the AMOC, destabilizing the climate. That was when the world’s population was approximately 400 million; now we are closing in on 9 billion. Looking further back scientists have begun drawing correlations between a 50 percent slowdown of the AMOC and ice ages in the Northern Hemisphere. Current conditions mirror these previous occurrences.
What can we do to stop this from happening? Very little. Even if the world stepped up to achieve the goals of The Paris Agreement and attempt to keep the global average temperature from increasing by 2°C, which is extremely unlikely as we have kept up business as usual, glacial ice melt may have already passed a tipping point and will continue to flood into the North Atlantic despite our best 11th hour efforts. While some extreme measures have been introduced to stop glaciers from disappearing, including wrapping them in white blankets, it may be too little too late. In any event, extreme fluctuations in the climate typically occur every 1,500 years, so we are already overdue, but this would be the first ice age triggered by mankind.
We may not be able to stop the glaciers from melting, but increasing global temperatures might pave a way into a different outcome than the earth’s prior rapid climate change events (but will probably make it worse). However, we can’t just sit on the sidelines, deny that it is happening, and not try to do anything. We should take this moment to mitigate the worst case scenario projections by reducing our greenhouse gas emissions, reducing our impact on the climate, and protect the environment for future generations. Although our planet earth will continue, she is our only home in the universe that we have found so far, we will need to adapt to a radically different climate for decades, or centuries, to come. Otherwise we will perish alongside so many other species that have faced the same fate. We may be the problem, but we can also be the solution.
Image credit: YaleEnriornment360