Atlantic is headed for a tipping point − once melting glaciers shut down Gulf Stream, we would see extreme climate change within decades, study shows

Subject: Geography

Section: Climatology

Atlantic Meridional Overturning Circulation (AMOC):

The AMOC is essential for distributing heat from the tropics to northern latitudes.
Observations since 2004 indicate that the AMOC has slowed down to potentially its weakest in nearly a thousand years, with studies warning that it could reach a tipping point leading to irreversible decline due to global warming and melting glaciers and ice sheets.
Recent research utilizing advanced climate models simulated the impact of freshwater flow on the AMOC until it reached this tipping point.
The study concluded that the AMOC could completely cease within a century after reaching this critical juncture, leading to a significant drop in average temperatures across North America, Asia, and Europe, alongside severe global consequences.
Moreover, the study identified a physics-based early warning signal that could alert the world when the AMOC is approaching its tipping point, offering a valuable tool for monitoring and potentially mitigating this grave threat.

The ocean’s conveyor belt:

Ocean currents are propelled by a combination of wind, tides, and differences in water density.
In the Atlantic, warm, salty water from the equator moves towards Greenland, passing through the Caribbean Sea and the Gulf of Mexico, then along the US East Coast before crossing the Atlantic.
This flow, part of the Gulf Stream, is essential for transporting heat to Europe.
As the water cools on its northward journey, it becomes denser and begins to sink upon reaching Greenland. This sinking motion draws more water from the Atlantic, perpetuating a cycle akin to a conveyor belt.
However, an influx of fresh water from melting glaciers and the Greenland ice sheet can disrupt this process by diluting the ocean’s salinity.
Reduced salinity prevents the water from sinking, which in turn weakens the oceanic conveyor belt.
This diminished conveyor belt then transports less heat northward and allows less dense water to reach Greenland, further weakening the system. If the conveyor belt reaches a critical tipping point, it can shut down rapidly, disrupting this vital oceanic circulation.

What happens to the climate at the tipping point?

The findings of the research revealed that upon reaching the tipping point, the conveyor belt could halt within a century, significantly reducing heat transport to the north and prompting sudden climate changes.

The result: Dangerous cold in the North

When the Gulf Stream’s circulation halts, regions dependent on it for warmth, particularly North America and Europe, experience significant cooling by a few degrees.
The experiment revealed that Europe, heavily influenced by the Gulf Stream, could see temperature drops more than 5 degrees Fahrenheit (3 degrees Celsius) per decade, much faster than the current global warming rate of about 0.36 F (0.2 C) per decade.
Specifically, parts of Norway could see temperature decreases exceeding 36 F (20 C), whereas some Southern Hemisphere areas might warm by a few degrees.
The cessation of the conveyor belt would also disrupt sea levels and precipitation patterns, potentially pushing ecosystems like the Amazon rainforest, which is sensitive to reduced rainfall, toward their tipping points.
Such transitions could transform forests into grassland, releasing carbon into the atmosphere and eliminating a crucial carbon sink, thereby exacerbating climate change.
Historically, the Atlantic circulation has significantly slowed during glacial periods as melting ice sheets introduced fresh water into the ocean, leading to major climate oscillations.

Consequences:

The potential abrupt halt of the Atlantic conveyor belt would have dire consequences, including significant changes in temperature, sea levels, and precipitation patterns, which would profoundly impact human society.
These climate shifts would be irreversible on human timescales.

Source: DTE