Gulf Stream current could collapse in 2025, plunging Earth into climate chaos

This is an old chestnut.  Prophecies of doom about the Gulf Stream have been going on for decades now.  The evident truth is that it cannot accurately be modelled

A vital ocean current system that helps regulate the Northern Hemisphere's climate could collapse anytime from 2025 and unleash climate chaos, a controversial new study warns. 

The Atlantic Meridional Overturning Circulation (AMOC), which includes the Gulf Stream, governs the climate by bringing warm, tropical waters north and cold water south.

But researchers now say the AMOC may be veering toward total breakdown between 2025 and 2095, causing temperatures to plummet, ocean ecosystems to collapse and storms to proliferate around the world. However, some scientists have cautioned that the new research comes with some big caveats.

The AMOC can exist in two stable states: a stronger, faster one that we rely upon today, and another that is much slower and weaker. Previous estimates predicted that the current would probably switch to its weaker mode sometime in the next century. 

But human-caused climate change may push the AMOC to a critical tipping point sooner rather than later, researchers predicted in a new study published Tuesday (July 25) in the journal Nature Communications. 

"The expected tipping point — given that we continue business as usual with greenhouse gas emissions — is much earlier than we expected," co-author Susanne Ditlevsen, a professor of statistics and stochastic models in biology at the University of Copenhagen, told Live Science. 

"It was not a result where we said: 'Oh, yeah, here we have it'. We were actually bewildered."

AMOC as a global conveyor belt 

Atlantic Ocean currents work like an endless global conveyor belt moving oxygen, nutrients, carbon and heat around the globe. Warmer southerly waters, which are saltier and denser, flow north to cool and sink below waters at higher latitudes, releasing heat into the atmosphere. 

Then, once it has sunk beneath the ocean, the water slowly drifts southward, heats up again, and the cycle repeats. But climate change is slowing this flow. Fresh water from melting ice sheets has made the water less dense and salty, and recent studies have shown that the current is at its weakest in more than 1,000 years. 

The region near Greenland where the southerly waters sink (known as the North Atlantic subpolar gyre) borders a patch that is hitting record low temperatures, while the surrounding seas climb to all-time highs, forming an ever-expanding 'blob' of cold water.

The last time the AMOC switched modes during the most recent ice age, the climate near Greenland increased by 18 to 27 degrees Fahrenheit (10 to 15 degrees Celsius) within a decade. If it were to turn off, temperatures in Europe and North America could drop by as much as 9 F (5 C) in the same amount of time.

Direct data on the AMOC's strength has only been recorded since 2004, so to analyze changes to the current over longer timescales, the researchers turned to surface temperature readings of the subpolar gyre between the years of 1870 and 2020, a system which they argue provides a 'fingerprint' for the strength of AMOC’s circulation. 

By feeding this information into a statistical model, the researchers gauged the diminishing strength and resilience of the ocean current by its growing year-on-year fluctuations. 

The model's results alarmed the researchers — yet they say that checking them only reinforced their findings: The window for the system's collapse could begin as early as 2025, and it grows more likely as the 21st century continues.


No comments:

Post a Comment

All comments containing Chinese characters will not be published as I do not understand them