A recent research study highlights the essential significance of the blending of Atlantic and Arctic waters in maintaining the Atlantic Meridional Overturning Circulation (AMOC), which is critical for climate regulation on Earth.
A recent research study highlights the essential significance of the blending of Atlantic and Arctic waters in maintaining the Atlantic Meridional Overturning Circulation (AMOC), which is critical for climate regulation on Earth.
Scientists from the University of Southampton, the Indian Institute of Technology Bhubaneswar, the National Oceanography Centre, and Stockholm University examined ocean data collected from 1979 to 2021 to gain a deeper understanding of how the mixing of Atlantic and Arctic waters aids in sustaining the AMOC.
The AMOC operates like a vast ocean conveyor belt, transporting warm water from tropical regions northward and cold water southward, thereby regulating heat distribution across the globe. It plays a vital role in keeping Northern Europe, particularly the UK, significantly milder in comparison to other areas located at similar latitudes.
The findings, published in Nature Communications, revealed that the lower segment of the AMOC – the portion that consists of deep, cold, dense water flowing south in the Atlantic Ocean – comprises 72 percent Atlantic waters and 28 percent Arctic waters.
Dr. Dipanjan Dey, the leading author of the study and a postdoctoral researcher at the University of Southampton, explains, “When warm water reaches the cooler areas of the North Atlantic, it releases heat to the atmosphere, becomes denser, and sinks to great depths.”
He adds, “We discovered that while a portion of this dense water quickly returns south, a significant amount moves northward, where it combines with colder, fresher Arctic waters in places like the Denmark Strait, situated between Iceland and Greenland. This mixing process enhances water density even further before it flows southward, thereby reinforcing the strength of the AMOC.”
The researchers estimate that the blending of Atlantic and Arctic waters accounts for 33 percent of the conversion of warm, salty water into colder, fresher, and denser water, with the remaining 67 percent resulting from interactions between the ocean and the atmosphere.
This study challenges earlier viewpoints that concentrated primarily on heat loss in particular regions while overlooking the crucial process of Atlantic-Arctic water mixing.
Projections indicate that the AMOC may weaken as global temperatures rise due to climate change. A slower, shallower AMOC, reminiscent of conditions during the last Ice Age, has significant implications for global climate trends.
The new understanding of Atlantic and Arctic water mixing is vital for comprehending these phenomena.
Co-author Professor Robert Marsh from the University of Southampton explains: “As the surface of the ocean warms and becomes less salty, increased layering (stratification) impedes the essential mixing of Atlantic and Arctic waters. This diminished mixing reduces the AMOC’s strength by lowering the density and depth of its southward flow, which could lead to a broad slowdown of the circulation.”
“A reduction in the AMOC’s circulation would have severe repercussions, ranging from much cooler temperatures in Northern Europe to rising sea levels along the eastern seaboard of the United States. A significant weakening could engender abrupt and potentially irreversible changes to the climate of our planet.”
A diminished and shallower AMOC might also shorten the duration that carbon dioxide remains in the ocean before being released back into the atmosphere, possibly hastening climate change and its effects.
“To better anticipate future climate scenarios, climate models must accurately represent these water mixing processes,” states Dr. Dey. “Our research emphasizes the intricate connections between our climate and global ocean circulation patterns. It is crucial that we address global warming urgently to prevent reaching critical thresholds that could lead to a notable slowdown or even a collapse of circulation.”
