Melting ice caps may not shut down ocean current, say researchers 

Posted: April 9, 2022 by oldbrew in modelling, Ocean dynamics, research, Temperature
Tags: ,

A portion of the Atlantic meridional overturning circulation [image credit: R. Curry, Woods Hole Oceanographic Institution @ Wikipedia]

Another supposed climate tipping point, popular with the alarm-loving media, floats away? A feature that’s “built into many models” was found not to work as advertised.
– – –
Most simulations of our climate’s future may be overly sensitive to Arctic ice melt as a cause of abrupt changes in ocean circulation, according to new research led by scientists at the University of Wisconsin–Madison.

Climate scientists count the Atlantic Meridional Overturning Circulation (or AMOC) among the biggest tipping points on the way to a planetary climate disaster, says

The Atlantic Ocean current acts like a conveyor belt carrying warm tropical surface water north and cooler, heavier deeper water south.

“We’ve been taught to picture it like a conveyor belt—even in middle school and high school now, it’s taught this way—that shuts down when freshwater comes in from ice melt,” says Feng He, an associate scientist at UW–Madison’s Center for Climatic Research.

However, building upon previous work, He says researchers are revising their understanding of the relationship between AMOC and freshwater from melting polar ice.

In the past, a stalled AMOC has accompanied abrupt climate events like the Bølling-Allerød warming, a 14,500-year-old, sharp global temperature hike. He successfully reproduced that event using a climate model he conducted in 2009 while a UW–Madison graduate student.

“That was a success, reproducing the abrupt warming about 14,700 years ago that is seen in the paleoclimate record,” says He, now. “But our accuracy didn’t continue past that abrupt change period.”

Instead, while Earth’s temperatures cooled after this abrupt warming before rising again to plateau at new highs for the last 10,000 years, the 2009 model couldn’t keep pace. The simulated warming over the northern regions of the planet didn’t match the increase in temperatures seen in geological archives of climate, like ice cores.

In a study published this week in the journal Nature Climate Change, He and Oregon State University paleoclimatologist Peter Clark describe a new model simulation that matches the warmth of the last 10,000 years.

And they did it by doing away with the trigger most scientists believe stalls or shuts down the AMOC.

Continued here.

  1. JB says:

    “our accuracy didn’t continue past that abrupt change period”
    That alone should have been a stopper for the model.
    “they did it by doing away with the trigger”
    Until something else doesn’t fit.

    “according to new research led by scientists”–MONKEYS–“at the University of Wisconsin–Madison”

  2. Philip Mulholland says:

    “The problem,” says He, “is with the geological climate data.”

    Wow, pesky geological data ruining a good climate crisis story.
    There is a clear need here for some serious data reanalysis.

  3. oldbrew says:

    Incredibly – or may be not – published another article on April 7th trumpeting AMOC circulation failure as one of 5 key climate tipping points. Never letting the debunking of an alarm set them back 🙄

    The world is ‘perilously close’ to irreversible climate change. 5 tipping points keep scientists up at night
    . . .
    Atlantic circulation stops

    The circulation of the Atlantic is at risk.

    The official name of this danger is Atlantic Thermohaline Circulation Collapse. If it were to happen, it could bring about an ice age in Europe and sea level rise in cities like Boston and New York.

    What’s known as the Atlantic Meridional Overturning Circulation (AMOC) keeps warmer water from the tropics flowing north along the coast of northern Europe to the Arctic, where it cools and sinks to the bottom of the ocean. That cooler water is then pulled back southward along the coast of North America as part of a circular pattern.

    This cycle keeps northern Europe several degrees warmer than it would otherwise be and brings colder water to the coast of North America.

    There is some indication the system has experienced a gradual weakening over the past few decades, and it may be critically unstable.

    Lenton’s research suggests that if global temperatures continue to rise, the AMOC could collapse in 50 to 250 years.

    The 2019 IPCC report suggested the AMOC will “very likely” weaken this century but has a less than 10% chance of collapsing.

    But just the loss of a constant river of warmer water flowing toward Europe could lower temperatures there, strengthen hurricanes and raise the sea level along the northeastern coast of North America.

    “You’re not transporting as much water, so it gets backed up along the East Coast,” Dutton said.
    – – –
    ‘perilously close’ as in ‘could collapse in 50 to 250 years’ – ‘research suggests’ 🥱

  4. Johna says:

    Only the younger dryas showed this naïve inference playing out. However it was on the opposite end of the cycle where with the massive and unimaginable NA ice sheet melt diluted the salt water causing the temperature to plunge back down, but once it recovered the temperature shot back up. No other recorded ice age cycle shows this. Some interglacials have realised temperatures far higher than we have now – real lions roamed in Westminster to boot. *snip*. Or, the ideology of people who are clearly stupid and unfit to be our leaders. Boris Johnston is one such example and I believe Joseph Biden is another – there are more.

    [mod – a bit too angry there]

  5. […] Melting ice caps may not shut down ocean current, say researchers  — Tallbloke’s Talkshop […]

  6. oldbrew says:

    Spot the obvious non-sequitur…

    APRIL 11, 2022
    Researchers reveal variations in Arctic amplification effect during past millennium
    by Chinese Academy of Sciences

    The recent amplified warming in the Arctic during the last decades has received much attention. But how Arctic amplification (AA) has varied on longer time scales and what drives these variations remain unclear.

    Recently, a study has provided a new perspective on the AA effect during the past millennium based on the best available paleoclimate data and novel data assimilation methods.
    . . .
    The millennial AA index series revealed that AA exhibited strong variations over a broad range of time scales, which can be explained, to a large part, by the phase of the Atlantic Multi-decadal Oscillation (AMO) and recent anthropogenic greenhouse gas forcing.
    – – –
    How can ‘recent anthropogenic greenhouse gas forcing’ explain millennial climate patterns? Maybe they hope to deflect criticism from alarmists by saying that, but they’ve pointed out that Arctic amplification is nothing new so can’t per se be attributed to humans.

  7. johnm33 says:

    Whether you see it or not the Arctic is changing, this is due to ever increasing penetration of Atlantic/gulf stream waters. Previously these were blocked by thick ice over Barents acting like a baffle and by a far more coherent ice pack over the deeper ocean. With the thick ice breaking down over Barents more GS waters have entered both over that shelf and more seasonally through Fram and along that shelfs slope at depth. More water entering means more leaves this alters the dynamic so dependent on where the measures are taken it may seem, to honest observers, that both increased and diminshed flows are occuring in the amoc.
    For instance an increased flow of fresher arctic water not being up to speed with earths rotation holds tight to the north American coast as it’s pushed south, where it meets the gulf stream flowing north tight to the same coast, for the same reasons. They mix and both resist being pushed from the coast, so slowing the northward movement of some gulf stream measures. But they are pushed away from the coast by the arrival of more water from the same two directions and consequently move more slowly away from the coast. Does this slow down mean they become warmer due to more insolation i don’t know.
    What is happening is that as more Atl. waters penetrate the arctic they are establishing currents, and the ice no longer presents the immovable presence it once did and niether do the once still Arctic ocean waters. It seems that with every tidal cycle another push on the ‘flywheel’ takes place and residual currents build in both Fram and Nares straits exiting the arctic. So it looks to me that the present situation is one where the exagerated outflows [past equilibrium] are compensated by exagerated inflows in a slowly accelerating ‘livening’ of the Arctic, and my guess if nothing stops it is that the whole ocean/basin will be incorporated into the planets ocean circulation, there will be no resistance left in the arctic, currents will speed up, there may be seasonal ice in the arctic away from incoming atlantic waters, but as far east as the NSI the arctic will enjoy a slightly cooler version of western europes weather. No slowdown of amoc probably the reverse.

  8. Johna says:

    Ref johnm33; Its al seams very plausible. So can you explain what your informed guess is with respect to CO2. E.G. is it to prop up the UN IPCC scare, or the opposite i.e. part of the natural phase of the interglacial where peak heat dilutes the sea to cause the relatively rapid decent into the next ice age – like what happened in the Younger Dryas event (which was not CO2 driven)?? I say this as our energy systems are now in crisis with very serious war and ordinary people are very angry in being forced to pay the cost of the political derived CO2 scare. And if these politicians are not stopped by the people the mass murder the politicians will cause by purposefully invoking WW3?

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