AMOC Shutdown — New Climate Change Scare

Greenland glaciers seen from the air, freshwater melt pouring into the ocean. Greenland summer campaign 3 (20769799409) by NASA GSFC (PD).

Yet another scientific paper raises the alarm over a possible shutdown of the Gulf Stream, but it is an empty threat.

The Gulf Stream is a river of warmer water coursing through the North Atlantic from the Caribbean to Scandinavia, warming northern Europe along the way.

Compare Yellowknife, Canada (62°27′ North latitude) with Stockholm, Sweden (59°19′ North latitude). Though both cities are at nearly the same latitude (within about 3° of one another), their temperatures are significantly different. Stockholm, at 46.2°F (7.9°C) annual average temperature, is appreciably warmer than Yellowknife, at 24.3°F (–4.3°C). The record low temperatures are even more telling. Stockholm has a record low of −18.8°F (−28.2°C), while Yellowknife has a record low of −60.2°F (−51.2°C). The Gulf Stream contributes to these temperature differences as well as the difference in population: Stockholm (2,415,000) and Yellowknife (20,000).

Recent tweet on X regarding the so-called “AMOC shutdown” alarm.

The Gulf Stream is part of a larger, natural, climate regulation system called the Atlantic meridional overturning circulation (AMOC), or thermohaline (temperature-salinity) circulation.

Scare terms like “shutdown,” “tipping point,” and “collapse” have been used in a February 9, 2024 article in Science Advances.

This shutdown is not very likely. The only time the Gulf Stream is known to have shut down was during the Younger Dryas “Big Freeze”—10,900–9,600 BC.

Let’s take a look at what caused that shutdown and compare it to the current “threat.”

AMOC Shutdown — 10,900 BC

This may have been what the Lake Agassiz spill may have looked like in the early stages before the full breach. Greenlandic melt water stream (7638364560) by Thomas Neumann, NASA GSFC (CC BY 2.0 Deed).

The best hypothesis, so far, for how the Younger Dryas happened involves a temporary body of water called Lake Aggasiz in central Canada. Sea levels had already risen by about 40 meters since the depths of the last glacial maximum. Some of the melted glacial water had collected within a depression in the huge glacial sheet which covered Canada and parts of these United States—a territory far larger than that of Greenland.

Then, about 10,900 BC, that water breached the wall of ice which had kept it collected in the temporary lake. The spill likely accelerated as flowing water eroded the ice wall.

A University of Alberta scientific estimate claims that a total of 21,000 cubic kilometers of water spilled out of central Canada in as little as 9 months.

This massive spill of cold, fresh water created a cap on the thermohaline circulation, effectively shutting it down.

Freshwater is lighter than saline water at the same temperature. And, because the glaciers on North America and northern Europe continued to melt, albeit at a slower pace (Fairbanks, 1989), that freshwater cap persisted for 1,300 years.

Temperatures plummeted, returning the planet to glacial conditions. The transition was abrupt. And the end of the “Big Freeze” was equally abrupt, warming in some locations as much as +10°C in as little as 10 years. (For one possible cause of that abrupt ending, see the evidence in “Atlantis Date: How 3 Events in Science Correlate to Plato’s Island Subsidence.”)

Atlantis Date: How 3 Events in Science Correlate to Plato’s Island Subsidence

Wimpy Modern ‘Threat’

Grid-like chart showing the proportion of current Greenland melt (red square in lower right corner) compared to the Lake Agassiz spill 12,900 years ago. Chart overlays posterized image of scientists in the field on Greenland (NASA, PD). In other words, the current freshwater spill is only a tiny fraction of that required to shut down the Gulf Stream. Click on the image for a close-up view.

According to NASA, Greenland has been losing about 269 Gt per year of water (that’s giga-tons, or 269 billion tons).

With a little bit of math, we see that the yearly flow from Greenland is a little bit less than 1% of the Lake Agassiz spill rate. That’s pretty wimpy. To Americans, that’s like 1 penny compared to a full dollar.

And there are no locations on Greenland where a huge lake, like Agassiz, could form to create a larger pulse at some future date.

Analysis of the Younger Dryas Spill

When the Lake Agassiz spill happened, 10,900 BC, the water emptied into the North Atlantic raising sea level by a small amount. If all that water had been added to the North Atlantic in an instant, it would have raised the ocean between North America and Europe by about 0.395 meter, before moving on to level out the oceans of the entire planet. But the water was added over an extended period of months, giving that freshwater cap time to spread over all the oceans of the world, eventually raising sea level worldwide by 0.054 meter, in addition to the regular flow from glacial melt.

When we compare the Lake Agassiz spill to the current flow of the Gulf Stream, we discover that the spill which triggered the Younger Dryas was itself pretty wimpy. At 30 million cubic meters per second of flow (0.03 cubic kilometers per second), the Gulf Stream moves 710,058 cubic kilometers in the same 9 months of the Lake Agassiz spill. The Gulf Stream is nearly 34 times the flow of that ancient spill. Of course, we do not know what the Gulf Stream rate of flow was just before that spill, so our comparison is across nearly 13,000 years of time.

Petermann Glacier in northwest Greenland, ESA24895115 by ESA Copernicus Sentinel-2 (CC BY-SA 3.0 IGO Deed).

Claiming that the current Greenland spill will be able to shut down the Gulf Stream is like claiming that a temperature rise of +3°C will cause the world to burst into flames, but warming alarmist memes are full of such hyperbolic imagery. Neither one of these factors is close to the required threshold. For a Gulf Stream shutdown, we need more than 100 times the current flow. For Earth bursting into flames, we likely need an increase of +600°C—not +3°C.

Even so, it does not look like Greenland’s spill of cold, fresh water is going to be doing any shutting down of the Gulf Stream, just like raising global temperature by a few degrees is not going to see the world burst into flames, no matter how many plastic globes Bill Nye torches.

References

Brown, Michael. (2021:0805). “Massive ancient lake across Prairies emptied quickly enough to set off an ice age, study suggests.” Retrieved on 2024:0211 from https://ualberta.ca/folio/2021/08/massive-ancient-lake-across-prairies-emptied-quickly-enough-to-set-off-an-ice-age-study-suggests.html

Conversion-Website. (ND). “Cubic kilometers to tons (water).” Retrieved on 2024:0211 from http://conversion-website.com/volume/cubic-kilometer-to-ton-water.html

Fairbanks, R. (1989:12). “A 17,000-year glacio-eustatic sea level record: influence of glacial melting rates on the Younger Dryas event and deep-ocean circulation.” Nature, Vol. 342, 7 December 1989.

NASA. (ND). “Ice Sheets.” Retrieved on 2024:0211 from  https://climate.nasa.gov/vital-signs/ice-sheets/

van Westen, René M.; Kliphuis, Michael; Dijkstra, Henk A. (2024). “Physics-based early warning signal shows that AMOC is on tipping course.” Science Advances, 10, eadk1189 (2024) 9 February 2024.