In recent years, scientists have raised alarms about the potential collapse of key ocean currents in the Atlantic, with significant consequences for global climate and weather patterns. The Atlantic Meridional Overturning Circulation (AMOC), a vital ocean current system, has been slowing down due to rising temperatures and climate change. However, a new study published in Science Advances offers a glimmer of hope, suggesting that an unexpected back-up system in the Arctic could help maintain the AMOC’s stability. Researchers, including Marius Årthun from the University of Bergen, have identified a process occurring in the Barents Sea, an Arctic region, that could counterbalance the loss of dense water formation in the Nordic Seas. This breakthrough could postpone, or even mitigate, the potential collapse of these critical ocean currents that regulate Europe’s climate.
What Is the Atlantic Meridional Overturning Circulation (AMOC)?
The Atlantic Meridional Overturning Circulation (AMOC) is a key ocean current system that functions like a giant conveyor belt, circulating warm and cold waters across the Atlantic Ocean. Cold, salty waters sink near Greenland, travel south along the ocean floor, and then rise near Antarctica before heading back north. This continuous movement is crucial for regulating temperatures, especially in Europe. Without the AMOC, Europe could experience dramatic temperature drops, particularly during winter months, and rising sea levels could significantly affect the U.S. East Coast. However, rising temperatures and melting ice have been slowing the circulation, posing a serious threat to the AMOC’s integrity.
The Link Between Climate Change and the AMOC’s Weakening
Recent observations indicate that the AMOC has been slowing down in the last few decades. A key factor contributing to this weakening is the reduction in dense water formation, which occurs when cold, salty water sinks to the ocean floor. Under normal conditions, surface waters lose heat as they travel through the North Atlantic, causing them to sink and flow southward. However, climate change has disrupted this process. As global temperatures rise, surface waters in the Nordic Seas, including the Greenland, Norwegian, and Iceland Seas, are no longer cooling as efficiently. Additionally, the influx of fresh meltwater from the Greenland Ice Sheet is diluting the salt content of surface waters, preventing them from becoming dense enough to sink.
This slowdown in dense water formation in the Nordic Seas has raised concerns that the AMOC could collapse entirely, leading to drastic changes in the climate. Yet, the latest research presents a surprising development: a newly discovered back-up system in the Arctic may provide a lifeline for the AMOC.
The Discovery of the Arctic Back-Up System
Marius Årthun and his colleagues, in a recent study, discovered that the Barents Sea — located between Scandinavia and Svalbard — is undergoing a transformation that could help sustain the AMOC. As sea ice retreats further north, Atlantic waters are spreading into the Arctic Ocean, raising the temperature and altering the water composition. This process, known as Atlantification, refers to the warming and ice-free transition of the Arctic Ocean. By increasing the area over which dense waters can form, the Barents Sea is compensating for the loss of dense water formation in the Nordic Seas.
“Atlantification refers to the transition of the Arctic Ocean from a cold, ice-covered state to a warm, more ice-free state,” Årthun explained. “We find that this decrease [in dense water formation] in the Nordic Seas has been compensated for by more dense water formation in the Barents Sea and north of Svalbard.” This shift in the Arctic could be pivotal in helping sustain the AMOC for the foreseeable future.
How the Arctic’s Role Could Help AMOC Resilience
The scientists propose that this “back-up” system in the Arctic could offer resilience to the AMOC, potentially reducing the likelihood of a catastrophic collapse. As Atlantic waters invade the Arctic and melt sea ice, they create new areas for dense water formation. This process is crucial, as the Barents Sea and northern Svalbard are increasingly able to produce dense water due to the retreat of the sea ice edge. “These two regions have experienced a retreating sea ice edge, hence increasing the area over which dense waters can be produced,” Årthun noted.
The research offers new hope that the Arctic, although warming at an alarming rate, may play an unexpected role in counteracting the effects of climate change on the AMOC. “There are processes that add resilience to the AMOC, perhaps making a serious weakening or collapse less likely,” Årthun said, emphasizing that this back-up system could act as a buffer against the worst-case scenarios.
