A conveyor belt of ocean water that loops the planet and regulates global temperatures could be heading for a tipping point

Preface. The conveyor belt (AMOC: Atlantic meridional overturning circulatin) may be slowing down. If it stops, floods, increased sea level rise, and disturbed weather systems.

The recent IPCC report on climate change in oceans projects that, while the AMOC will weaken substantially during this century, a collapse by 2100 is unlikely. However, at our current rate of carbon output, its models give even odds of a shutdown by 2300.

Though of course the IPCC model could be wrong and a tipping point reached sooner than that. We just don’t know. Maybe more data over time will help with better predictions. If the conveyor does stop Europe could become as much as 10 degrees F cooler and the monsoon cycles vital to Asian and South American crops disrupted. Floods, droughts, and hurricanes would increase, sea levels rise along the U.S. East coast along with heat waves. Marine ecosystems will be harmed, and if the conveyer shut down affects the jet stream, cause more heatwaves and cold snaps in North America and Europe.

But the IPCC model assumes we’ll be burning fossil fuels at our current rate until 2400, while many geologists and other scientists believe we are within 5 to 20 years of peak fossil fuel production. Fossils will decline rapidly after peak because we’ve already gotten the easy, close, and shallow deposits, and any lowering of the standard of living and less affordable oil triggers social unrest, and eventually war as shortages grow greater, causing production to decline for other than geological reasons.

I’ve excerpted perhaps a third of the article, for details go to the original source.

Alice Friedemann www.energyskeptic.com  author of “When Trucks Stop Running: Energy and the Future of Transportation”, 2015, Springer, Barriers to Making Algal Biofuels, and “Crunch! Whole Grain Artisan Chips and Crackers”. Podcasts: Derrick Jensen, Practical Prepping, KunstlerCast 253, KunstlerCast278, Peak Prosperity , XX2 report

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Katz, C. 2019. Why is an ocean current critical to world weather losing steam? Scientists search the Arctic for answers. National Geographic.

Fram Strait and the waters to the south, in the Greenland, Norwegian, and Irminger seas, make up the control room of a global “conveyor belt” of currents that stretches the length of the planet. Only in this region and one other, in the Antarctic, does water at the sea surface become heavy enough—dense with cold and salt—to sink all the way to the seafloor and race downhill along the deepening ocean bottom. That sinking powers the conveyor, known as the Atlantic meridional overturning circulation, or AMOC—which in turn regulates temperatures and weather around the world.

A new report warns that the AMOC is one of nine critical climate systems that greenhouse-gas-fueled warming is actively pushing toward a tipping point. Crossing that threshold in one of these systems could trigger rapid and irreversible changes that drive other systems over the edge—leading to a global tipping cascade with catastrophic consequences for the planet. The analysis, released last week in Nature by an international group of leading climate scientists, says the tipping point risks are greater than most of us realize.

The AMOC conveyor belt may already be showing signs of sputtering as a result. A network of ocean probes across the mid-Atlantic, between the Bahamas and Africa, has recorded a 15 percent drop in the current’s flow over the past decade. A recent modeling study suggests that the slowdown began a half-century ago as planet-warming carbon emissions started to soar. The IPCC, projects that the conveyor will weaken as much as a third by 2100 if emissions continue at their present rate. An enfeebled AMOC could trigger a host of changes, including floods, increased sea level rise, and disturbed weather systems.

Waters east of Greenland are getting not only warmer but also less salty. These melting Greenland glaciers, melting sea ice in the Arctic, and rivers swollen by increased precipitation in Siberia have all contributed to a large flush of fresh water into the Fram Strait—a 60 percent increase over the first half of this decade.

Whether those forces are the cause of the conveyor’s current sluggishness isn’t certain. But at some point, if the water here gets too fresh, or too warm, or especially both, it will become too light to sink, say de Steur and other ocean scientists—jamming the works of one of the most fundamental forces in the global climate system. Temperatures in the polar water flowing into the Fram Strait have climbed nearly 1 degree F over the past 17 years, while the Atlantic water has warmed nearly half a degree. If the trend continues, it could dampen deepwater formation and throttle the conveyor belt’s engine just like freshening will.

Other key components of Earth’s climate works that may be heading toward a tipping point include summer sea ice, which models predict will disappear as early as 2036, permafrost, now rapidly thawing across wide swaths of the Arctic, the vast Greenland ice sheet, the Amazon rain forest, and more.

So far there’s been no change in the deepwater formation. But the warming and freshening she has observed here on past voyages are worrisome, and if things continue as they are, at some point it’s going to have an impact.

Historical climate models find that the conveyor belt has slowed significantly in recent decades. And paleoclimate evidence shows the AMOC is currently the weakest it’s been in at least a millennium. The system has been slowing for at least 50 years—in line with the rise in humans’ carbon output.

The recent IPCC report on climate change in oceans projects that, while the AMOC will weaken substantially during this century, a collapse by 2100 is unlikely. However, at our current rate of carbon output, its models give even odds of a shutdown by 2300.

An abrupt brake on the current around 950,000 years ago sent the planet into a long series of ice ages. More recently, Europe was plunged into a 2,000-year cold spell known as the Younger Dryas around 13,000 years ago, after the current sharply weakened. Although it’s not certain what caused those conveyor breakdowns, melting ice sheets are believed to have played a major role.

Even short of a shutdown, the effects of weakening ocean circulation would be felt around the globe. Because the Gulf Stream warms Northern Europe by as much as 10 degrees F, a drop in the heat flowing north would make European winters colder.

The changes in the ocean’s heat uptake and transport would make the South Atlantic hotter, shifting the bulk of the planet’s heat southward and disrupting monsoon cycles vital to Asian and South American crops, according to the IPCC.

Floods and droughts would increase on both sides of the Atlantic, along with more frequent hurricanes along the southeastern United States and Gulf of Mexico. A backed-up Gulf Stream could raise sea levels along the U.S. East Coast, driving more warm water—and possibly steamier temperatures—ashore.

Marine ecosystems and fisheries would suffer. On top of that, muddled ocean circulation could knock the already wobbly jet stream further off kilter, triggering more summer heatwaves and winter cold snaps across North America and Europe.

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