Ocean Current System – That Influences Weather Patterns Globally – Seems To Be Approaching a Tipping Point

North Atlantic Ocean Currents

North Atlantic Ocean Currents. Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio

The AMOC, a system of ocean currents influencing weather patterns globally and responsible for the mild European climate shows signs of stability loss.

The Atlantic Meridional Overturning Circulation (AMOC) may have been losing stability in the course of the last century, a new study by Niklas Boers, published in Nature Climate Change suggests. The finding is worrying as well as a surprise. The AMOC, to which also the Gulf stream belongs, is responsible for the relatively mild temperatures in Europe and influences weather systems worldwide. A collapse of this ocean current system, which has so far not been considered likely under the current levels of global warming will therefore have severe consequences on global and especially European weather and climate. The study is part of the European TiPES project, coordinated by the University of Copenhagen, Denmark, and the Potsdam Institute for Climate Impact Research, Germany.

Tipping the AMOC

The AMOC is the key circulation system of the Atlantic Ocean. It moves heat from the Tropical region to the Northern hemisphere by transporting warm water masses northward at the ocean surface, and returning as a cool current southward at the bottom of the ocean.

Model simulations and data from so-called paleoclimate proxy records suggest that the AMOC can be in two distinct modes: A strong mode, which is currently attained – and an alternative, substantially weaker mode of operation. This bi-stability implies that abrupt transitions between the two circulation modes are in principle possible.

Signs of Instability in Ocean Current System

Signs of instability in ocean current system. Credit: TiPES/HP

At its weakest

Because the AMOC redistributes heat, it influences weather patterns globally. A collapse from the currently attained strong circulation mode would therefore – among other impacts – cool Europe substantially as well as strongly impact the tropical monsoon systems.

It has been shown previously that the AMOC is currently at its weakest in more than 1000 years. However, so far it has remained unclear whether the observed weakening only corresponds to a change in the mean circulation state, or whether it is associated with an actual loss of dynamical stability.

“The difference is crucial. Because the loss of dynamical stability would imply that the AMOC has approached its critical threshold beyond which an abrupt and potentially irreversible transition to the weak mode could occur,” says Niklas Boers, author of the study.

Fingerprints of a collapse

Long-term observational data of the strength of the AMOC does unfortunately not exist. But the AMOC leaves so-called fingerprints in sea-surface temperature and salinity patterns of the Atlantic Ocean. It is a detailed analysis of these fingerprints that now suggests that the AMOC weakening during the last century is indeed likely to be associated with a loss of stability, and thus with the approaching of a critical threshold beyond which the circulation system could collapse.

The finding is not only worrying but also quite surprising as an abrupt transition of the AMOC has so far been expected to occur at global warming levels much higher than the current 1,2 degrees Celsius.

“Most evidence suggests that the recent AMOC weakening is caused directly by the warming of the northern Atlantic ocean. But according to our understanding, this would be unlikely to lead to an abrupt state transition. Stability loss that could result in such a transition would be expected following the inflow of substantial amounts of freshwater into the North Atlantic in response to the melting of the Greenland ice sheet, melting Arctic sea ice and an overall enhanced precipitation and river runoff,” Boers explains.

Freshwater inflow and especially Greenland meltwater runoff has indeed accelerated in the last decades. However, although a first sign of regional destabilization of the Greenland Icesheet has been detected, recent Greenland runoff should not be sufficient for destabilizing the AMOC.

To understand this in-depth we need to find ways to improve the representation of the AMOC and polar ice sheets in comprehensive Earth system models and to better constrain their projections. I hope that the results presented here will help with that!” Boers concludes.

Reference: “Observation-based early-warning signals for a collapse of the Atlantic Meridional Overturning Circulation” by Niklas Boers, 5 August 2021, Nature Climate Change.
DOI: 10.1038/s41558-021-01097-4

The TiPES project is an EU Horizon 2020 interdisciplinary climate science project on tipping points in the Earth system. 18 partner institutions work together in more than 10 countries. The TiPES project has received funding from the European Horizon 2020 research and innovation program, grant agreement number 820970.

10 Comments on "Ocean Current System – That Influences Weather Patterns Globally – Seems To Be Approaching a Tipping Point"

  1. Clyde Spencer | August 5, 2021 at 9:34 am | Reply

    “Tipping Point” is another misnomer like “greenhouse effect” and “ocean acidification” that carries more emotional value than actual information. Call it what it is — a possible “loss of dynamical stability” or “an abrupt and potentially irreversible transition to the weak mode.” However, short of our sun becoming a supernova, it is improbable that any physical changes are truly “irreversible.” Earth even recovered from major bolide impacts.

    Mark Twain — ‘I have been on the verge of being an angel all my life, but it’s never happened yet.’

    So it is with so-called tipping points!

  2. The insanity. The globe is warming, but the AMOC might stop because of the warming and we are back in an Ice Age. Likely we will be entering a cooling phase as the warm surface waters won’t move as much north and more storms as the difference between Arctic Air and Tropical Air temps becomes more extreme and a strengthening of the Jet Stream. And life will go on like it was 1770, and we will realize that a few degrees warmer is a good thing even if it’s a short time. It was much warmer 8,000 years ago and started a cooling trend about 4,200 years ago. And the sea levels were 2m higher than today. Perhaps one day “the science” won’t be so political and we can have a serious discussion without the insanity.

    • You are misinformed. No past warming period has been anywhere near as abrupt as what we are causing currently. Your comparison is misinformed misinformation.

      • Clyde Spencer | August 5, 2021 at 2:57 pm | Reply

        “No past warming period has been anywhere near as abrupt as what we are causing currently.”

        That is a claim commonly made by alarmists; however, you have no way of knowing that with certainty. The farther one goes back in time, the lower the resolution of both the time and the temperatures derived from geologic proxies. Time acts like a low-pass filter, if you know what that is. Basically, a low-pass filter removes the high-frequency Fourier components of a signal, and the ‘spikes’ are removed.

        There are some who think that the end of the last major glaciation took place over a period of of a few hundred years, perhaps only decades. We will probably never know because we cannot measure either the time or temperatures with sufficient resolutions to be certain.

        Certainly the Meltwater Pulse 1A was much more dramatic than what we are currently experiencing, or have experienced for the last 7,000 year!

  3. Khan Noonien Singh | August 5, 2021 at 10:23 am | Reply

    The poles are shifting. Terrestrial geomagnetic field reversals DO have a measurable effect on Earth’s climate. The ast major shift happened 42,000 years ago (known as the Laschamps Excursion). Scientists have found that geomagnetic field minima ~42 ka, in combination with Grand Solar Minima, caused substantial changes in atmospheric ozone concentration and circulation, driving synchronous global climate shifts that caused major environmental changes, extinction events, and transformations in the archaeological record. To simplify, global warming is a mechanism directly attributed to and relative to the shifting of the earths poles. Global chemistry-climate modeling and detailed radiocarbon dating of paleoenvironmental records show this to be the case.

  4. The amount of FEAR mongering by the media never ceases to amaze. Europe might get colder? In the light of global “warming”, isn’t that a good thing? Even if the Earth warms up more, that just means Siberia, Greenland, Northern Canada and Alaska will become prime real estate. Move North, Miss Tessmacher!

    The irony is despite 100+ years of carbon dioxide “pollution” (for goodness sake, our own bodies make it and need it to function), human contributions to carbon dioxide levels are about 0.04% of the total. It’s amazing such a small change could destroy the planet! It’s even more amazing to think we used to have a giant planet of jungles and dinosaurs with far more carbon dioxide and life went on. The pandemic proves that fear motivates change and so it doesn’t matter whether life will be affected as much as predicted or not. What really matters is what companies get richer and who gets/stays in power.

    If humans were really serious about reducing our footprint, we’d consider laws limiting how many children people could have to get the overall world population down to something less polluting, like say 2 Billion people instead of 8 Billion. But it seems companies and governments would prefer to give up meat, gasoline vehicles, world travel and maybe even electricity rather than have a two child maximum rule or something sane.

    When your economic system is based on constant unending GROWTH, reducing world population doesn’t fit into it even if ultimately destroys the planet. Maybe the economic system is the problem. How do you think increasing use of robots as workers will fit into that model? We’re headed for an entirely different world disaster that is based on a made up system. Automation should make our lives better, but in reality it only makes the owners’ lives better. Everyone else can look for a new job or starve. No Jetsons future for this planet!

  5. Clyde Spencer | August 5, 2021 at 8:34 pm | Reply

    A couple of questions to ask are, 1) What would we want to accomplish with geoengineering? (e.g. Optimize conditions for life?); 2) What would the optimal average global temperature be given the goal?

    Keep in mind that after the demise of the dinosaurs, the abundance, variety, and size of mammals increased, at a time when it was much warmer. Currently, David Attenborough claims that 50% of all species of life live in the 1% of the land we call Tropics!

    • 1&2) roll back atmospheric composition bit by bit to about 1950s levels. It’s still a little high from industrial revolution output, but doable.

      There are other issues beyond heat & msl. Too much heat for too long will cause scarring in the form of desertification, which may blow any remaining topsoil away and require its own geoengineering to reverse. It may also burn out the tropics depending on location and model. Also, in lower latitudes where arable land can still be worked, crop leaves may grow larger to handle heat dissipation, which in turn requires more fertilizer and wear & tear on equipment. And then of course there’s a bunch of cranky people in the heat who fight over aquifers and foothills to feed themselves.

      My position on this is that the old saying, “if you can’t stand the heat, then get out of the kitchen” completely ignores that I have a vent hood and air conditioning in my kitchen to handle just that. I don’t stand around and debate the merits of being in a 100F room and how it may help keep food warm when I set it on the counter after cooking, or that profusely sweating over the stove is just great and that I need to talk myself into thinking it’s just great.

      • Clyde Spencer | August 7, 2021 at 7:41 am | Reply

        “… roll back atmospheric composition bit by bit to about 1950s levels.”

        You really think that is doable without rolling back the global population to 1950s levels?

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