Ocean Stratification is Not Good News. Very Not Good.

September 28, 2020

Michael Mann in Newsweek:

As we continue to warm the planet through fossil fuel burning and other activities releasing carbon pollution, the surface and lower atmosphere is warming faster than the air aloft. That favors heavy colder air on top of lighter warmer air, and a less stable atmosphere. It means more turbulence and more energetic storms. And it’s part of the reason we expect more extreme weather events in a warmer world.

With the oceans, we have the opposite. The warm, lighter surface waters are warming faster than the cold deeper water, since heat penetrates slowly down into the depths of the ocean. Global warming is consequently tending to make the oceans more stable. Sea water density depends not just on temperature but saltiness (“salinity”) too. Fresh water is lighter than salty water, and the melting of ice is leading to the accumulation of fresh, light water at the surface, especially at higher latitudes. It’s a double whammy, with both heating and reduced salinity leading to a more stable ocean.

My colleagues and I have just published an article in the journal Nature Climate Changeshowing that the oceans are not only becoming more stable, but are doing so faster than was previously thought. Led by Guancheng Li of the Institute of Atmospheric Physics in China, our team (which also includes Lijing Cheng, Jiang Zhu, Kevin Trenberth and John P. Abraham) analyzed a quantitative measure of stability known as “stratification”. We found that the stratification of the world oceans is not only increasing, but is doing so at a greater rate than estimated in previous studies. Our study uses more comprehensive data and a more sophisticated method for estimating stratification changes, and we found a nearly 6 percent increase in the stratification of the upper 200 meters (~650 feet) of the world oceans over the past half century.

This seemingly technical finding has profound and troubling implications. The more stable the upper ocean, the less vertical mixing that takes place. This mixing is a primary means by which the ocean buries warming surface waters. So the surface warms up even faster. It’s what we call a “positive feedback”—a vicious cycle.

That’s bad for a number of reasons. As we currently watch the most active Atlantic hurricane season on record play out, a key underlying factor is the anomalous surface warmth of the tropical Atlantic. The increasingly intense and damaging hurricanes we’ve seen in recent years have fed off warmer surface waters. More stably stratified waters tend to inhibit the wind-driven mixing up of cold deeper waters that often serves as a sort of release-valve, shutting off the source of energy at the surface that intensifies these storms. A more stably stratified ocean potentially favors more intense, destructive hurricanes.

Warmer waters absorb less atmospheric carbon dioxide (just as warm soda loses its carbonation faster when you open the top.) Less ocean mixing also means that less of the atmospheric carbon dioxide gets buried beneath the ocean surface. So carbon pollution accumulates even faster in the atmosphere, causing yet more warming. Another “positive (i.e. bad) feedback” and another double whammy.

Finally, warmer upper ocean waters hold less dissolved oxygen. And less ocean mixing means less oxygen (and nutrients,) since oxygen and nutrients depleted by sea life are less likely to be replaced from rising, colder more oxygen-rich waters. That’s bad for marine productivity. It means the potentially interruption of food webs and fish populations that provide the main source of protein for more than three billion people.

Our findings also have important implications for how much additional warming we may see in the future. State-of-the-art climate models used today to predict future climate change tend to underestimate the stratification of the ocean. They consequently bury heat (and carbon) too easily beneath the ocean surface. For that reason, they are likely underestimating the impact that the increased stratification (and decreased mixing) found in our study is having on rising atmospheric carbon dioxide levels and surface warming.

Our study suggests that key positive feedbacks (amplifying factors) related to reduced ocean heat might lead to more rapid surface warming in the decades ahead than many of the models predict. Decreased ocean carbon burial resulting from the reduced upper ocean mixing, moreover, could cause atmospheric carbon dioxide concentrations to build up faster in the atmosphere. Our findings lend credence to a recent study arguing we cannot rule out “worst case” scenarios (that some dismiss as “exceedingly unlikely“) where carbon dioxide concentrations reach nearly triple pre-industrial levels—and the planet warms up by perhaps as much as 8F—by the end of this century.

In short, it’s unwise to be complacent given the accumulating scientific evidence that climate change and its impacts may well be in the upper end of the range that climate scientists currently project. There is ever-greater urgency when it comes to acting on climate. But there is agency as well. Our actions make a difference—something to keep in mind as we head into a presidential election whose climate implications are monumental.


Just as hot air rises, as is seen in the formation of towering clouds, hot water rises as well because it is less dense than cold water. If the hottest water is on top, vertical mixing in the oceans slows. Also, melting ice from various glaciers introduces fresh water into the upper layers of the oceans. Fresh water is less dense than salt water and so it tends to remain on the surface as well. Both elevated temperature and salinity cause greater ocean stratification and less ocean mixing.

“The ability of the oceans to bury heat from the atmosphere and mitigate global warming is made more difficult when the ocean becomes more stratified and there is less mixing,” said Mann. “Less downward mixing of warming waters means the ocean surface warms even faster, leading, for example, to more powerful hurricanes. Global climate models underestimate these trends.”

Mann and his team are not the first to investigate the impact of a warming climate on ocean stratification, but they are looking at the problem in a different way. The team has gone deeper into the ocean than previous research and they have a more sophisticated method of dealing with gaps in the data. They report their results today (Sept. 29) in Nature Climate Change.

“Other researchers filled in gaps in the data with long-term averages,” said Mann. “That tends to suppress any trends that are present. We used an ocean model to fill in the gaps, allowing the physics of the model to determine the most likely values of the missing data points.”

According to Mann, this is a more dynamic approach.

“Using the more sophisticated physics-based method, we find that ocean stability is increasing faster than we thought before and faster than models predict, with worrying potential consequences,” he said.

19 Responses to “Ocean Stratification is Not Good News. Very Not Good.”

  1. Anthony William O'brien Says:

    Have you read Peter D Ward’s “Under a Green Sky”. Let’s us know where this is heading, not pretty.

    • Oscar Bautista Says:

      Gee…thanks for the re-assuring words. NOT.

      Last I checked, there were some “re-assuring” words that Peter Ward’s scenario was very unlikely…Now I am not so sure.

  2. “In short, it’s unwise to be complacent given the accumulating scientific evidence that climate change and its impacts may well be in the upper end of the range that climate scientists currently project.”

    Unfortunately this under-estimation appears to have happened across the board -each scientist is noticing that the feedback in their area is worse than anticipated but if you put them together we shoot straight past the worst projections.

    None of the projections cover the Siberian Permafrost GHGs
    None of them anticipated the methane boiling out of the Arctic
    None of them account for all the rainforests vanishing
    None of them have a sudden acceleration of Glacier melt when we run out of Arctic Ocean Ice (probably by 2035 and very possibly before 2030 in Summer ..though not before 2022 -year round zero-ice follows shockingly fast though not immediately).

    I don’t think anyone has even attempted to predict what will happen to Ocean Currents when that happens but the Gulf Stream certainly won’t be the same.

    Greenland Ice will take the brunt but those currents are likely to take the ocean temperature spike straight to the Thwaites Glacier (unless they shut down or do something ‘weird’).

    The millimetres sea level rises we’re used to will be metres *very* abruptly: time enough to evacuate but maybe not time enough to build flood defences when Thwaites goes. the ‘other shoe’ I’m hoping not to hear about is the other side of Antarctica.

    No one should be talking about 2100 because it both vastly exaggerates our ability to predict and even more dangerously gives license for politicians to delay critically urgent action.

    Our Civilization will be changed radically within 20 years whether we do it or suffer it. Some Billionaires and Centamillionaires are already assuming society is toast and thinking about how to weather the breakdown (primary concern being securing the loyalty of their security forces -I’ve read reports of experts being set to work on that).
    Other absurdly rich people literally think the Biblical “Rapture” is about to arrive ..Trump is listening to some of them )

    • grindupbaker Says:

      “None of them anticipated the methane boiling out of the Arctic” Provide your calculations.

    • grindupbaker Says:

      “when we run out of Arctic Ocean Ice (probably by 2035 and very possibly before 2030 in Summer ..though not before 2022 -year round zero-ice follows shockingly fast though not immediately)”. By “run out of Arctic Ocean Ice” you mean <5.8% by area for 24 hours in September, which is 1/213th of the spring/summer for Arctic Ocean, but it's effect is far less than 1/213th because there'e next to no sunshine at all. Here's some numbers to start you. Do some work for a change you lazy, selfish, worthless babbler.
      MAR 9.3
      APR 31.9
      MAY 52.3
      JUN 49.0
      JUL 26.3
      AUG 8.5
      SEP 3.6
      OCT 1.1
      For 24 hours in September then 3.6/30 = 0.12 is a fair approximation. How's that scale for importance against the numbers ?
      "year round zero-ice follows shockingly fast" is a pile of lazy, lying, stupid, un-studied, worthless drivel & it's going to be very difficult for me to forgive the ignorant Mister Think for that imbecilic gem that he just did. I do forgive though because he doesn't have malice (only ignorance) and doesn't have only his income in mind like the other 2 blokes have.

      • rhymeswithgoalie Says:

        The value of arctic sea ice varies greatly by the perspective. Heat transfer to the atmosphere is a growing problem. Thin sheets may reduce that somewhat, but then still has lower albedo than the thicker ice, and is no good to [charismatic] megafauna that relies on it. It’s the polar bears and walruses that “run out” of arctic ice, even if there’s a pretty patch of it on the satellite data.

        Ever-lower sea ice cover means shipping through the arctic is ramping up, though they might have more trouble in Iceberg Alley between Baffin Island and Greenland.

        And if you’re not concerned with the amount of ice in darker September, note that the amount of ice is dropping year-round, meaning more ocean is absorbing heat during the high summer.


    • grindupbaker Says:

      Well we know the disaster scenario from Eric Rignot so people browsing past here (thank goodness) don’t need to rely on your lazy, un-studied, un-quantified babbling. Eric thinks glacier discharge will increase to a massive 6-7x the present rate when the ice shelf & related buttressing of a glacier has gone so that’s (300 + 2,200) * 5.5 / 360 = 38 mm / year of sea level rise (SLR) when the ice shelves are all gone, which would be 7.6 metres of SLR over 200 years. During the Eemian Optimum at 126,000 to 122,000 years ago it was 7 metres of SLR over 300-700 years. However, Eric states 4.6 m over 100-200 years so he’s probably factored in a rate of ice shelf loss. The preceding is what’s available from a leading glaciologist, 30 years of expertise in the specialty. I assume that Eric’s 100 years, or much less than 200 years, is only if humans go hog wild.

    • grindupbaker Says:

      “No one should be talking about 2100” The natural cycles are ~30 years, varying but decades rather than years. Thus climate scientists (it’s a physical science) can’t project well on time scales of less than several decades. What you socio-politico-onlys with your blatantly-obvious zero interest in the actual physical science (your bone-idle selfish laziness) choose to be “talking about” is an entirely separate topic and your own business. Your stupid attempts to convert WG1 climate science into a 5th rate Gong Show of a pretense-only junk science is however quite sickening. Why not have a “political debate” about it, that’ll certainly educate everybody with high-quality information on which to base intelligent decisions. Furthermore to that sickening English weasel Sir Somebody with your “Pleeeeease call it climate change for the Americans, pleeeeease don’t call it global warming”, Winston Churchill would have stubbed his cigar out on your eye ball you sickening excuse for a English man.

  3. redskylite Says:

    Peter Ward’s book was set at a time more than 200 million years ago, when a cataclysmic event known as the Permian extinction destroyed more than 90 percent of all species and nearly 97 percent of all living things.

    It’s worth taking note of the distinguished paleontologist’s account, (lest the world’s life today—ourselves included—face the same dire fate that has overwhelmed our planet several times before.) but we are not facing quite the same circumstances as that era, a lot depends on our future actions, and stopping the upward rise of greenhouse gases.

    If we want reassurance regarding our future, then we need to take consolidated urgent action as a united globe.

    Sentinels of ocean acidification impacts survived Earth’s last mass extinction.

    “Current rates of carbon release are at least an order of magnitude higher than we have seen for the past 66 million years.”


    • rhymeswithgoalie Says:

      If we want reassurance regarding our future, then we need to take consolidated urgent action as a united globe.

      There’s way too much lag in the system for sufficient human motivation.

      • redskylite Says:

        Wonder what the time period of something negative occuring, caused by climate change, does motivate the general public. Certainly not 150,000 years and we didn’t get concerned with the change of century, and computer code compliance until the last few years of the 20th century.


        “This cataclysmic melting will not occur in our lifetimes; the full effects would likely not be seen for roughly 150,000 years, Andrew Shepherd, a climatologist from the University of Leeds in the United Kingdom, who was not involved in the study, told the Daily Mail. ”


        • grindupbaker Says:

          It’s an issue all right. I stand firmly in favour of stating the WG1 climate science as clearly as it is known (and to my understanding) and not lying, exaggerating, mis-informing, stating baseless opinion (unless saying that it’s baseless when you do it) in pursuance of the perceived common good. For one thing, apart from the ethics issue, the opposing team of coal/oil shills have the money to hire some competent scientists so you’ll (I don’t mean you) likely just worsen the social situation when the stream of “They said 10 years ago that we’s all be……..by now and nothing like that happened) so it isn’t only ethically bankrupt but it’s not even a winning social strategy. You all know there are persons on the social team opposing coal/oil shills who concoct lies, exaggeration, disinformation, mis-leading with intent & accidental/ignorant misinformation for their diverse personal reasons, just as the coal/oil shills do. A climate scientist “Kevin Trenberth” just says “Really, this is most unhelpful”. That bloke’s as dry as sandpaper.

        • grindupbaker Says:

          You finally got me laughing again after 20 years with Millenium Bug & cheered me up. Only a computer programmer of mind-bogglingly lazy or incompetent brain (or a scam artist) would incorporate dates that have anything at all to do with calendar dates. My computer programs for commercial applications (so include dates) I wrote with dates that work within +/- 90 years (+/- 32,767 days) of the date stored in the computer. Probably because I came from scientific/mathematical start 1968 with IBM-360/44 oil/gas exploration scientific computer rather than that weird “commercial” version IBM had that did decimal arithmetic (a binary computer doing decimal arithmetic). I realized at the time it was likely a scam that I was too thick, not cunning enough, to think of. You deliberately write these crappy programs that’ll screw up at the switch 1999—>2000 (because there’s absolutely no valid reason why you should write them to screw up like that) and then 1998 you send a warning & proposal “Your system needs an upgrade for the new Millenium. Attached our proposal which gets us $400 / hour for our Junior Staff to plod through for 2 years & make these most banal straightforward fixes to what was totally botched the 1st time” except you leave out the high profit & underlying-reason parts. I’m probably exaggerating the extent to which pre-meditation played a role, but it was an absolute disgrace whatever.

          • rhymeswithgoalie Says:

            Only a computer programmer of mind-bogglingly lazy or incompetent brain (or a scam artist) would incorporate dates that have anything at all to do with calendar dates.

            The big problem was the legacy input fields that only allowed 2 digits for years. It doesn’t help to have an internal representation that can handle larger spans if the input is restricted.

            BTW, many forms are again being created with 2-digit year inputs, but with the accelerating obsolescence of tech, nobody expects current interfaces to be viable in 80 years.

  4. Brent Jensen-Schmidt Says:

    The next IPCC report is going to be vicious. A little bird told me.

  5. grindupbaker Says:

    I’ll explain a simple physical science thing about that in case anybody browses here who’s interested in the physical science apart from the problem thing. “The ability of the oceans to bury heat from the atmosphere and mitigate global warming” (said Mann) is a cartoon with incorrect science that’s definitely good enough for the public. The “bury heat” which the climate scientists use is the wrong end for affecting the surface (close to a biological analog there). When heat goes into the ocean, below the well-mixed 90 m layer, it warms the ocean but cannot affect the surface. What affects the surface is simply == the volume of stuff == being shoved into the ocean, any stuff at any temperature, for the decades / centuries time scale. It must be matched by an equal volume being shoved to the surface and the average ocean temperature is 3.5 degrees but average surface-air temperature is 15 degrees and that difference of 11.5 degrees combined with the massive thermal capacity of water compared with air makes the water that sank there from Antarctica the last 3,300 years (one complete cycle) have significant cooling capability for centuries to come when some of it gets shoved up. It’s “cold” being shoved up, not “bury heat from the atmosphere”. This is why “pause” or “hiatus” reduced surface warming happened between the 1997/98 & 2015/16 El Ninos when the wind speeded up 30% (1 m/s) and caused more up-welling. Of course, I know that the deep ocean doesn’t mix at the surface but that’s the under-pinning, cold moving up to a greater or lesser extent (the arse end of warm water being mixed down if you’re British).

  6. grindupbaker Says:

    Much unnecessary, un-quantified babbling about latent heat of Arctic Ocean sea ice is occurring in comments sections of Web Logs & videos, such as “when we lose the Arctic ice, sauna conditions expected”. Utterly-worthless, lazy drivel. It’s unnecessary because the actual amounts, in degrees, are easily calculated and most basic information is provided in the June 2019 paper from the analysis of CERES data. This following is for latitude 75N which is the centre of the Arctic Ocean area so it’s a good-enough average. It’s relative to 1979 AD per the June 2019 paper so you’d need to find the slight warming over 6 months spring/summer in the 1970s and earlier and add it on to the degrees below. The 1st below is reality when the Arctic Ocean has no sea ice in late March each year and the 2nd below is hypothetical lesser warming if late March sea ice were exactly as it was in 1979 but it was a perfectly crystal-clear ice that sunlight went through 100% with no reflection so when you view it from space you see only ocean dark water everywhere whenever it’s visible in a cloud-free sky because you can’t see the crystal-clear sea ice on top. In this hypothetical (impossible) situation it turns out that 85% of the surplus heat is used to melt ALL of the 1979-volume sea ice and only the 15% surplus heat left warms the ocean. So the 1st result below (the real one) minus the 2nd result below (the hypothetical one with the warming reduced by the latent heat of melting the 1979-volume 35,000 km**3 of sea ice ) equals the ice latent heat difference.
    1) An Arctic Ocean with no sea ice (later this century)
    March September at latitude 75N
    22nd 22nd
    -1.8 5.1 Average Arctic Ocean Sea surface temperature (SST)
    -1.8 4.5 10 m depth Arctic Ocean temperature
    -1.8 3.9 20 m depth Arctic Ocean temperature
    2) An Arctic Ocean with a hypothetical (impossible) situation which has 1979 AD 1.9 m thick sea ice but it’s crystal clear ice so the ocean below heats just like open water with no ice on it would heat.
    March September at latitude 75N
    22nd 22nd
    -1.8 -0.8 Average Arctic Ocean Sea surface temperature (SST)
    -1.8 -0.9 10 m depth Arctic Ocean temperature
    -1.8 -0.9 20 m depth Arctic Ocean temperature
    So with the 35,000 km**3 of ice on the Arctic Ocean on March 22nd (average 1.9 m thick) per PIOMAS plots and using crystal clear sea ice to absorb almost all solar radiation into the ocean below then 85% of that spring/summer solar radiation is used to melt the ice and only 15% heats the ocean.
    Conclusion: Starting at the 1979 AD Arctic Ocean sea ice and ending when there’s no Arctic Ocean sea ice in late March the extra surface temperature just for ice latent heat is +5.9 degrees, overall surface heating is +6.9 degrees.
    If the above is done starting at 2016 unstead of 1979 then the extra surface temperature just for ice latent heat is +3.1 degrees, much lower than the +5.9 degrees because, of course, there’s been 48% ice volume loss from 1979 to 2016.
    My own calculations for whenever there was full Arctic Ocean sea ice cover all year (perhaps ~1720 after Maunder Minimum in “Little Ice Age” but whatever) to 1979 AD indicates enough heat to have reduced average sea ice thickness by 0.62 m but I’m not claiming much accuracy on that. If I am accurate there then add:
    +2.1 surface temperature (SST)
    +1.9 10 m depth temperature
    +1.6 20 m depth temperature
    to all 6 of the September 22nd temperatures above
    These are very simple calculations and accurate within 0.5 degrees based on factors other than air currents. However, air currents anomaly is a huge factor that only a professional atmospheric physicist being paid full time could do with worthwhile accuracy and certainly not me as a hobby. So, they might not match reality because I presently know of 2 reasons only, both potentially quite large, but I don’t yet know enough to calculate future quantities like I did above for the solar radiation absorbed & loss of sea ice latent heat. They are:
    1) Warm air from south might increase or decrease (it’s presently 66 in spring/summer and 164 in autumn/winter). There are conflicting reasons why the 66 and 164 might increase or decrease, or any combination:
    a) The only reason warm air goes there is that polar is cooler than equator (it’s going down hill, same thing that the thermohaline circulation (THC) surface current is doing)) so it should decrease.
    b) The Coriolis Effect formula form is Accelerationeast> = f (Velocity (south—->north, latitude) and that formula is highly exponential so the 66 and 164 might increase by decreasing the heat drop to 37N-60N and decreasing the heat drop overall while increasing the heat drop.
    The factor is 0.34 degrees change per 1 unit change of 66 in spring/summer, and 0.40 degrees change per 1 unit change of 164 in autumn/winter.

  7. grindupbaker Says:

    “decreasing the heat drop to 37N-60N….” to the end S.B.
    decreasing the heat drop to 37N-65N and increasing the heat drop 65N-90N (that would be Wonky Jet Stream Arctic intrusions overwhelming the overall reduction of heat from the tropics for the 65N-90N region) while decreasing the heat drop 37N-90N overall.
    The factor is 0.34 degrees change per 1 unit change of 66 in spring/summer, and 0.40 degrees change per 1 unit change of 164 in autumn/winter.
    2) Warm water from south might increase or decrease or might mix more into the shallow part (it’s started doing that).
    Also, warm air & water from south will be getting warmer at the regular ocean surface global warming rate of +0.19 degrees / decade and +0.11 degrees / decade average to 700 m depth.
    193 units (w/m**2) holds a surface air temperature of 0 degrees with a typical lapse rate, so quite accurate for spring/summer, but autumn/winter has far too much heat for it’s temperature so it must be that all that warm air arriving high up & radiating some to space without it affecting the near surface which is causing that. For autumn/winter the heat is 164 for warm air + 12 for sunlight absorbed + 19 for latent heat = 195 w/m**2 average but S.B. 156 for -14 degrees (I estimate) with a typical lapse rate so I infer that 39 of the 164 of warm air from the tropics radiates to space from higher temperatures at higher altitudes (a lot of thermal inversion over a winter Arctic) without warming the surface.

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