Mississippi Delta marshes in a state of irreversible collapse, Tulane study shows

Tulane University

IMAGE
IMAGE: Salt marshes about 30 miles (50 km) southeast of New Orleans are vulnerable to drowning. view more  Credit: Photo by Torbjörn Törnqvist

Given the present-day rate of global sea-level rise, remaining marshes in the Mississippi Delta are likely to drown, according to a new Tulane University study.

A key finding of the study, published in Science Advances, is that coastal marshes experience tipping points, where a small increase in the rate of sea-level rise leads to widespread submergence.

The loss of 2,000 square miles (5,000 km2) of wetlands in coastal Louisiana over the past century is well documented, but it has been more challenging to predict the fate of the remaining 6,000 square miles (15,000 km2) of marshland.

The study used hundreds of sediment cores collected since the early 1990s to examine how marshes responded to a range of rates of sea-level rise during the past 8,500 years.

“Previous investigations have suggested that marshes can keep up with rates of sea-level rise as high as half an inch per year (10 mm/yr), but those studies were based on observations over very short time windows, typically a few decades or less,” said Torbjörn Törnqvist, lead author and Vokes Geology Professor in the Tulane Department of Earth and Environmental Sciences.

“We have taken a much longer view by examining marsh response more than 7,000 years ago, when global rates of sea-level rise were very rapid but within the range of what is expected later this century.”

The researchers found that in the Mississippi Delta most marshes drown in a few centuries once the rate of sea-level rise exceeds about one-tenth of an inch per year (3 mm/yr). When the rate exceeds a quarter of an inch per year (7.5 mm/yr), drowning occurs in about half a century.

“The scary thing is that the present-day rate of global sea-level rise, due to climate change, has already exceeded the initial tipping point for marsh drowning,” Törnqvist said. “And as things stand right now, the rate of sea-level rise will continue to accelerate and put us on track for marshes to disappear even faster in the future.”

While these findings indicate that the loss of remaining marshes in coastal Louisiana is probably inevitable, there are still meaningful actions that can be taken to prevent the worst possible outcomes. The most important one, Törnqvist said, is to drastically curb greenhouse gas emissions to prevent sea-level rise from ramping up to rates where marshes will drown within a matter of decades.

The other one is to implement major river diversions as quickly as possible, so at least small portions of the Mississippi Delta can survive for a longer time. However, the window of opportunity for these actions to be effective is rapidly closing, he said.

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Törnqvist conducted the research with Krista Jankowski and Juan González, who received their PhD degrees at Tulane under his supervision, and Yong-Xiang Li, a former postdoc in his group.

Justin Lawrence of the National Science Foundation, which provided funding for the study, added, “The effects of marsh loss are a serious public concern in coastal regions of the United States and elsewhere, and this study could lead to better management decisions that curtail those effects.”

Additional funding was provided by the National Institute for Climatic Change Research Coastal Center of the U.S. Department of Energy.

From EurekAlert!

109 thoughts on “Mississippi Delta marshes in a state of irreversible collapse, Tulane study shows

  1. They are worried about the predicted rate of sea level rise later this century but we do know that not one of the global warming predictions have come to pass since 1990. Why do they think the predictions now are any more feasible than the failures of the past? They certainly subscribe to the alarmism catechism where past failures are ignored and predictions are gospel.

    • The key word in studies like this is “Tipping Point” That means watch out, as most logic is superseded by emotion.

    • Where I live in Norway, the sea stood 80m higher than to-day in the stone age (7000 years ago)The main reason was the ice cover that was retreating from the last ice age, when the sea level was even higher. When these scientists predict a higher sea-level now, it makes me think that they expect a new ice age.
      It’s logical to think that when the land on the northern hemisphere is still rising after the ice-age, the more southern located part without previous ice cover, is sinking.

    • exactly…..

      “where a small increase in the rate of sea-level rise leads to widespread submergence.”

      Like the normal rate of sea level rise doesn’t

        • Yes, this right here. I was going to start by saying, the marshes are drowning, but not because of anything discussed in this article. And since sea level has steadfastly refused to accelerate its rise, and since temperatures have steadfastly refused to accelerate their rise (since the end of the Little Ice Age, for both), those can’t be it. What is going on, the marshes most likely have always subsided, just due to compaction of decaying organics, if nothing else, but the deltas used to flood just about annually, which would deposit another layer of silt, building the marshes back up again. But then us brilliant humans, thought we could outsmart the river, or whatever, channelized the river, built up huge dikes and levees and diversion channels and etc. until the river couldn’t flood anymore. Now the marshes don’t get built back up annually, yet they continue to subside. So, like the headline says, reconnect the Mississippi to its wetlands. There you go. Problem solved.

          • Exactly! Deltas rise with rising sea level! That’s how they came into being. When sealevel rises, the water moves upstream a little, slowing the river water which then causes it to drop its load of sediment early.

            I’m afraid that geology students have been getting loaded with climate science filler that has diluted scientific geological thinking. During glacial maxima when sealevel drops 400 feet or more, mass wasting (land slides) and wave action, breaks the delta up reducing it down to the new lowered sealevel. Things done to the Mississippi and its delta already have created the problems they are having. My assessment of what will happen to the proposed new, linearly thought out plans is unfortunately held up by mods so I cant link it.

          • Kids playing mud puddles learn at a very early age that deltas rise and fall but always manage to stay just above the water level if left to their own devices.

            Like nature, they go with the flow.

        • Careful, you can encourage very destructive erosion by channeling and redirecting to cut-off the area you wish to preserve. Increasing flow rate in one sector will cause sediment from upriver that would normally settle out to be transported farther out into the Gulf and also cause serious erosion cutting deeper into sediments under the more active channels.

          This will cause sloughing and channel pattern changes in the area you want to preserve, favoring movement of sediment and water sideways into the adjacent more active sector causing the river to to try to undo the “restorative” works.
          A very large river laden with silt and sand is not going to cooperate with a linearly thought out interference into its highly efficient energy, water and suspended materials distribution. It likes its own solutions.

          A best solution if you have to interfere, is to slow the flow a little in the river channel just before it divides up into distributaries of the delta. Then the river will rebuild the entire delta itself. Maybe get a bit of hydropower as a bonus, but not through dam construction blocking flow along the bottom.

          Where do I send my invoice?

    • I would just direct everyone to look at Australia’s failed Murray-Darling Scheme before they entertain the idea of river diversion.

    • Sometime in the past couple of years a Geological Survey study of the Louisiana Coast was published and a post on it was published here at WUWT. It reported both subsidence and uplift, which varies from place to place, all along the coast. The average subsidence was around 11mm per year, which is considerably more than any measurement of absolute seal level rise.

      I would gi ve a link but I don’t think I have ever been successful in finding previous WUWT articles through the WUWT search facility.

    • When the rate exceeds a quarter of an inch per year (7.5 mm/yr), drowning occurs in about half a century.

      If they knew how big an inch was it would lend some credibility !

      They seem to be working on a U.S. 30mm inch, not the European 25.4mm inch 😉

      Maybe they’d read that a foot was about 30cm and got a bit confused ??

      Of course this blatant incompetence flew past peer review by a fleet of PhD peers, full of “Science Advances”.

      I love these little indicators they can’t help leaving into flag their incompetence. Always useful in assessing a paper.

      • Isn’t an inch just a decifoot?

        Once again it was a cinch to glance at the headline and know “this schist comes from the EurekAlert! comrades”

      • The US National Institute of Standards and Technology is an agency of the US Department of Commerce and is the official body that sets standards of measurement in the US.

        The Appendices to NIST Handbook 44 – 2020 “Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices” set forth the official definitions of units.
        https://www.nist.gov/pml/weights-and-measures/publications/nist-handbooks/other-nist-handbooks/other-nist-handbooks-2-3
        Section 2.2.5 of Appendix B says:

        “From 1893 until 1959, the yard was defined as equal exactly to 3600/3937 meter. In 1959, a small change was made in the definition of the yard to resolve discrepancies both in this country and abroad. Since 1959, we define the yard as equal exactly to 0.9144 meter; the new yard is shorter than the old yard by exactly two parts in a million. At the same time, it was decided that any data expressed in feet derived from geodetic surveys within the United States would continue to bear the relationship as defined in 1893 (one foot equals 1200/3937 meter). We call this
        foot the U.S. Survey Foot, while the foot defined in 1959 is called the International Foot.”

        Conversion Charts are in Appendix C:

        I international mile where 1 in = 24.5 mm exactly is 1609.344 meteres exactly
        But,
        1 survey mile where 1 survey foot equals 1200/3937 meters exactly is 1609.347 meters.

        NIST would like to get rid of the survey foot, but it is embedded in lots of land records in the US.

  2. Current sea level rise is 3mm per year,which according to their study gives us a few centuries before the disappear. Haven’t we got anything better to spend money on than this nonsense ?

    • Pure crap anyway, Bob.

      Anybody stop to think how marshes form in the first place? How does the government create marshes? Is it the Army Corps of Engineers or was it the Civilian Conservation Corps during the New Deal? EurekAlert! is decrying the loss of that legacy and the need to build all-new marshes as the ocean expands at a dizzying pace of 3 millimeters per year.

      The big scandal nobody talks about is how incompetent the Doggerland government was at maintaining their marsh lands.

  3. “The scary thing is…

    Stuff like this gets into print. As with all various climate alarms:

    the window of opportunity for these actions to be effective is rapidly closing

    • I think we are supposed to care and get emotional like they are on the subject …. only it just comes off as joke to most of us.

  4. “And as things stand right now, the rate of sea-level rise will continue to accelerate and put us on track for marshes to disappear even faster in the future.”

    The Grand Isle tide gauge
    https://www.psmsl.org/data/obtaining/stations/526.php
    does not indicate acceleration. Plot the annual data in Excel and ask for the 2nd order polynomial with the equations and if there’s any acceleration at all, it’s negative. y = -0.0124x² or -0.0248mm/yr²

    Dave Burtan’s web page says
    https://www.sealevel.info/MSL_graph.php?id=grand+isle
    says -0.0266 ±0.0431 mm/yr²

    But the rate of sea level rise is a whopping 9 mm/yr but then anyone who pays attention to this stuff knows that most of that is land subsidence.

    …there are still meaningful actions that can be taken to prevent the worst possible outcomes. The most important one, Törnqvist said, is to drastically curb greenhouse gas emissions…

    Which of course will do absolutely nothing with respect to sea level rise. Sea level has been rising at more or less the same rate since it was first recorded early in the 19th century.

    • The public has no clue that enormous blocks of land can subside, and I’m not sure that they want to know. Knowing this might disrupt the narrative.

    • PSMSL.org also provides GPS elevation gauge data under “other data.” The GPS gauge for Grand Isle shows subsidence at a rate of 6.69 mm/yr while the tide gauge shows a rise rate of just over 8 mm/yr. The net, actual sea level rise, is about 1.3 mm/yr. World wide, tide gauge minus elevation shows an actual sea level rise rate of about 1.6 mm/yr, not 3 mm/yr. The 3 number comes from satellite measurements which are “adjusted” by NOAA, and we know how that works.

  5. “The scary thing is”. Poor snowflakes being scared yet again – they’d better put their heads under the cover.

  6. “……. there are still meaningful actions that can be taken to prevent the worst possible outcomes. The most important one, Törnqvist said, is to drastically curb greenhouse gas emissions to prevent sea-level rise from ramping up to rates where marshes will drown within a matter of decades.”

    OK dude. There should be some kind of statute against humans making other humans embarrassed to be human.

    • I came to Louisiana as a biologist with a few years of marsh and geological background and got put in my place within a few years. I studied the 1970s floods which started the Atchafalaya delta emergence and may still have mud from there starting with difficult to imagine amounts of sediments and nutrients they transported. Lots of scientists inside and outside fail to appreciate the enormous complexity and difficulties of “managing correctly” a major delta. There are some good scientists there who will examine this, but too many think they absolutely know the restoration answers. Tipping points occur, but the delta is so enormous it will take more than a few. Louisiana coast is the nation’s largest estuary, but its axis is mostly horizontal unlike the Chesapeake which usually gets the credit.

      A few notes. Diversions have some logic behind them but have their own problems and are a fraction of the transport–[Snedden, G. A.,, et al., 2007. Sediment discharge into a subsiding Louisiana deltaic estuary through a Mississippi River diversion. Estuarine and Coastal Shelf Science. 71:181-193.] The Nita Crevasse (1890) carried a third of the discharge of the entire river, twice the normal discharge of Niagara Falls. [Okerson, in Steinmayer, R. A. 1939. Bottom sediments of Lake Pontchartrain, Louisiana. Bulletin of the American Association of Petroleum Geologists. 23(1):1-23. ]

      Fig. 3 showing their “Distribution of the 355 boreholes across the MD that were used for the paleo-marsh analysis” is well up from the active delta [“Nevertheless, since the shoreline must have migrated landward at a relatively rapid pace during the early Holocene, we cannot rule out the possibility that our study areas were sufficiently far seaward from the river mouth to experience a temporary period of reduced sediment supply”], an area early on realized as important and where the structure of particular interest is located. A good well written discussion by Barnett, J. F., Jr. 2017. BEYOND CONTROL. The Mississippi River’s New Channel to the Gulf of Mexico. Univ. Press Miss. 292 pp.

      Open access https://advances.sciencemag.org/content/6/21/eaaz5512

      • My understanding is that left to its own devices, the water that now flows through the Mississippi River past Baton Rouge and New Orleans to the Gulf of Mexico, would flow down the Atchafalaya River and deposit its load of sediment in the marshes near its mouth, 70 miles west of New Orleans. One of the major projects of the US Army Corps of Engineers has been to maintain that flow of water.

        It is beautifully discussed and described by Author John McPhee in the New Yorker Magaxine in a 1987 article “Atachafalaya” https://www.newyorker.com/magazine/1987/02/23/atchafalaya and is collected with a lot of related material in his book: “Control of Nature” https://www.amazon.com/Control-Nature-John-McPhee/dp/0374128901/

        A big part of the problem of the marshes in southern Louisiana is that they are being deprived of this sediment. That would nourish them and raise their level.

        • Exactly. In the 70’s we were taught at University that the US Army Corp of Engineers was causing all Mississippi sediments to be deposited far out to sea on the shelf edge at the tip of the “birdfoot” delta. This has been depriving the rest of the delta to receive these sediments. Since all these deltaic deposits are slowly compacting, they are naturally sinking. Without a steady sediment supply on top, all the Mississippi delta is destined to sink below sea level. This has absolutely nothing to do with climate change and everything to do with geology.

  7. When I was a kid they told us about how much Louisiana has grown due to sediment deposited from the Mississippi. I was told that upstream people needed to be better stewards of the river to prevent runoff.

    Damn global warming! With COVID and global warming it’s like a Mosh one two punch o’roo.

  8. “the present-day rate of global sea-level rise, due to climate change, has already exceeded the initial tipping point for marsh drowning,”

    So many things wrong with this. Global sea-level rise is as useful a concept as global temperature is on the moon. Sea level is a relationship between the land and the water and is 100% local. In some places it is rising, in some places it is falling, and in some places it isn’t changing at all. Global measurements are irrelevant.

    The implication of the quote is that humans are causing sea levels, globally, to rise. Sheer unprintable hubris.

    “past the tipping point…” What a tired old saw. These people shriek and foam at the mouth about false prophecies over and over and over. There is almost certainly no substance to this one, anymore than all the rest.

  9. There have been increased UFO sightings as aliens are worrying about what we are doing to the planet.

  10. Apparently dredging hundreds of deep straight channels through the marshes, like the one seen in the picture accompanying the article, doesn’t affect them at all. Nor do the massive changes to the annual flow of the river that created the marshes from all the channelizing and stabilization done to make it more useful for barge traffic.

    They have clearly nailed the real problem: I drive a car that runs on gasoline.

    • Don’t forget about the river that feeds the whole system. It’s more-or-less locked in its current path with berms and levees. I wonder how much silt would be added to the marshes if the river was set free? Of course, there are several cities, towns, farms along the way that would probably not fare well. It’s like everything else today. There are choices to be made.

    • It is the same government that sanctioned the building of the levees along the Mississippi River, greatly reducing natural sedimentation of the marshland, that is exaggerating the climate problem so they can fix it.

  11. Almost as an afterthought, they mention the real culprit: “there are still meaningful actions that can be taken to prevent the worst possible outcomes. . . . The other one is to implement major river diversions as quickly as possible . . .”

    The Mississippi levees keep sediment within the river channel and allow the previously deposited marsh sediment outside the channel to do what sediment has always done – consolidate. When working as environmental consultant/auditor on the Deepwater Horizon oil spill in 2010 and 2011, I was initially stationed at Grand Isle, LA. From there I visited the beaches, several barrier islands, and surrounding marshes. Then I was stationed in Venice, LA, about as far south as you can drive on the Mississippi River delta where I visited the marshes and on several occasions went further down the river to Southeast pass and other points. Later on as the spill cleanup progressed, I moved on to sites in MS, AR, and FL. This was a very educational experience for me.

    • When there is natural sediment deposit in the delta, sea level is irrelevant. Most of the sediment is still on the river bottom and the levies are raised to match. When the Mississippi finally jumps it’s bank and takes over the Atchafalaya river there will be a new delta to the west.

  12. Excerpted comment:

    “The scary thing is that the present-day rate of global sea-level rise, due to climate change, has already exceeded the initial tipping point for marsh drowning,” Törnqvist said.

    If Mississippi Delta marshes are not “rising” ……. then they will likely be “subsiding”. 😊

    Forming – Destroying the Wetlands

    The foundation for the coastal marshes was formed from Mississippi River Basin sediments that were carried and deposited by the river. For over 7,000 years the river flooded, depositing these sediments and building land,

    Each deltaic cycle began when a distributary, with a shorter, steeper route to the Gulf of Mexico, gradually captured the Mississippi River. As the river abandoned its old route, the fresh supply of sediment to the old lobe diminished and the area experienced compaction, subsidence and erosion. https://www2.southeastern.edu/orgs/oilspill/wetlands.html

    • I’ve been to the Mississippi Delta marshes, and, indeed, they are subsiding. The whole delta is slipping into the sea. The main cause is commercialism, whereby important shipping interests despaired of the task of keeping the river shoals clear in the important New Orleans area, and prevailed upon the Corp of Engineers to divert the valuable silt back out to the Gulf via the Atchafalaya diversion of the Mississippi River. This is one of the old river channels, and likely the locals in what was to become New Orleans noted the delta subsiding back when it was last active.
      The Corp also ruined the Kissimmee River in Florida. We never learn.

      • “I’ve been to the Mississippi Delta marshes, and, indeed, they are subsiding.” How did you measure it? Are they growing or diminishing?

        • How to measure it?
          Many scientific articles going back 100 years have explained it.
          “Everything floats, Georgie…” — Pennywise

        • “The Sea is rising!” Locals on the islands near the mouth of the Chesapeake Bay have been decrying climate change foe years, convinced that rising water levels, flooding their hundreds years old life style, were cause by Global Warming.
          Not so. Silt, washed down from the Appalachians and SE Pennsylvania, had been feeding a delta system at the mouth of the bay. Modified farming and drainage control have all but stopped the supply of sediment to these delta, which like New Orleans, are slowly SUBSIDING (settling downward) into the delta. Why the actual bayous and island are not physically moving towards deeper water is unclear.

          • Why the actual bayous and island are not physically moving towards deeper water is unclear.

            Maybe an uptick of major storms in the Bay area may get them moving.

            A few major rainfalls on the eastern face of the Appalachians or a few major hurricanes making “shore” on the east or southeast shore.

  13. Don’t worry, there will be more nesting sites for endangered species like Flying Polar Bears and the Abseiling Walrus. <:o)

  14. The scary thing is that these dishonest “academics” are paid by somebody, possibly American taxpayers.
    Australia has two well-known tide gauges, at Fremantle and Fort Denison, about 3,000 miles apart. Each has been operating for more than 120 years and each shows that the gentle natural rise in sea level has been less in the most recent six decades than in the previous six decades.

    • Maybe that’s because of the change from the 30mm inch to metric units in 1974? Now it’s down to 25.4?

      • Walter Sobchak (above at 10:25 am) says NIST conversion now is 1 inch = 24.5 mm, not 25.4 mm. That’s news to me; my memory (same as yours) is still stuck at 25.4 mm, and I refuse to change. But this reminds me that I have a folding measuring stick (from my father-in-law) with metric and English inches on one side, and Japanese inches on the other, which nearly caused me to make a measurement error as I was previously unaware of Japanese inches.

        • Possibly of interest with regard precision. This video I found very informative and entertaining. He is a true enthusiast about precision and metrology. As am I.

          It discusses the foot/meter history you are debating, and much more about the root of precision.

          https://www.youtube.com/watch?v=gNRnrn5DE58

          He has one unfortunate trait: his articulation is not good. He swallows his words. Normally it is hard for me to listen to someone who speaks so clumsily, but the information was so good, I got past it.

          I would love to possess a surface plate just to have one to inspire all my non-machine-shop pursuits. I would place a vase with tulips on it. Nothing else.

  15. Perhaps Jim Steele could explain to them about how things should be examined at the local level as opposed to trying to use some global context. But then I would think they are not capable of listening and learning.

    • One thing about science, when he government mandates certain thought to get grants, everything else gets tossed out. We’re going to be a couple of decades digging out from a generation of brain washing about and rewarding the global warming scam with grant money. Truman was right. Science is no longer about science. It’s about promoting specific political agendas and supporting government bureaucracies.

      • Ike also warned about this.
        We hear about his ‘Military-Industrial Complex’ warning, but in the same speech he also warned about Big (government funded) Science.

  16. All river deltas around the world are sedimentary built on deep cut canyons. ALL. The ‘drowning’ of ALL river canyons started in earnest 20,000 years ago when the seas rose 11,000 cm in 7,000 years straight. So how did the any of the river deltas manage to keep up? For Pete’s sake, did any of these ‘scientists’ do the thing that underpins all science, and that is to think, independently?
    The BBC ran an article on the Mekong Delta and for an 11 min video ‘Climate Change’ was mentioned 17 times and problems caused by upstream dams was mentioned once and in passing and absolutely nothing about the huge increase in water extraction from nothing 30 years ago to 2.5 million litres a day now.
    https://www.youtube.com/watch?v=5fdFTGEhkxs
    The Displaced: Climate change in Vietnam ‘destroying family life’ – BBC News

    Someone said to me recently: ‘We have to do something about climate change because it’s all over the news all the time”

    • Someone said to me recently: ‘We have to do something about climate change because it’s all over the news all the time”

      Easy solution. Turn off the news.

  17. Lack of natural sediment flow because the River has been bermed and levied is a choice that was made to allow the current river to be tamed for flood control and navigation. Delta subsidence is the real culprit here with regards to sea level rise. Jakarta in Indonesia is sinking even faster because of pumping out fresh water from an underneath aquifer. What if one was to pump down large volumes of fresh water from the river into the delta aquifer rocks and under New Orleans and area…would that slow down the land subsidence? Probably cost a lot of monies, but New Orleans is sinking, and I don’t know how to swim.

  18. A progressive process with caveats. The typical unqualified monotonic function: one step forward, two steps backward.

  19. Total mismanagement of Mississippi marshes has been documented since at least the 1970s as far as I am aware. It’s not sea level rise that’s killing the marshes. It’s development, dredging, refusing to allow the marsh to expand naturally where is can, pollution, diversion of fresh water. All the money in the world to fight global warming is not going to save those marshes.

  20. From the above article: “The most important one, Törnqvist said, is to drastically curb greenhouse gas emissions to prevent sea-level rise from ramping up to rates where marshes will drown within a matter of decades.”

    I believe executing the scientific method would first require obtaining overwhelming evidence that greenhouse gas emissions are a substantial factor causing the observed rise rate of global sea-level. To the best of my knowledge, this has not been done. And the Earth is, after all, in the historically-early, warming stage of a interglacial cycle within the current Ice Age.

    Without this simple start, all the rest is speculation and folly.

  21. Over decades and centuries, a marsh is free to pack up the household and move upstream when the downstream domicile becomes unsuitable. The nature of nature is not static. Who wants to tell them?

    • Nonsense Heyseuss, those marshes were exactly the same for 4.5 billion years until we came along and started burning fossil fuels. It’s just like the coral that had been happy for 200 million years of perfectly stable climate, now on the brink due to massive fractional degree warming of the ocean, obviously caused exclusively by our CO2 emissions.

      • I like your take. To generalize a little, are all alarmists marsh dwellers? I don’t really know, but I am forming an opinion ..

  22. Big problem with the delta is all the flood control on the river – no longer deposits silt, building up the delta. Not saying flood control is bad. But like all things it does have consequences both good and bad.

  23. These agenda-driven pseudoscience studies make their lies by telling partial stories. Telling just half-truths in order to deceive a naive public, leaving out important information that alters the conclusion that would otherwise be drawn. It’s all pretty standard fare for the pseudoscience behind the climate scam.

    By far the biggest factor is Delta subsidence under consolidation of long-ago deposited silts and clays, and with diversions and channels dredged, the marshes are without a steady resupply of fresh sediments.

  24. As a Tulane engineering graduate, I receive the TULANE magazine. The team headed by Prof. Tornqvist continues to publish alarmist papers claiming the disappearance of the Mississippi delta as a result of climate change. https://issuu.com/tulaneuniversity/docs/tulane_september-2017/8 (page 17).
    Two letters of mine refuting this were published in the TULANE magazine. In the first I reminded the professor than 1897 issue of the NATIONAL GEOGRAPHIC vol.8, #12, page 353 https://archive.org/details/nationalgeograph81897nati/page/352/mode/2up contained the observation that: “It is a fact well known to the people living in the delta of the Mississippi that large tracts of land were long ago abandoned in consequence of overflow by Gulf waters due to sinking of the lands.”

    This fact has not sunk in over a hundred years later.

    https://issuu.com/tulaneuniversity/docs/tulane_december_2015 (page 4)
    https://issuu.com/tulaneuniversity/docs/tulane_december-2017 (page 4)

  25. The scary thing, the key finding of this sharticle is that the inch is about to pass a staggering 30mm tipping point.

  26. The world’s land area INCREASED in the last 30 years. Anthropogenic sea level rise since the beginning of time is estimated at 2 inches in a consensus of current literature.

  27. If the delta is “in a state of irreversible collapse” then there is nothing to be done and we can all stop worrying about it. Move on…it’s irreversible.

    Meanwhile, adapt any new construction to take this into account.

    Jeez, it this really so hard?

  28. Of course, we must always remember that the satellite dataset has the fiddle factor of 0.3mm per year added to “account for changes to ocean basin size”. Adjustments are only allowed in one direction. Why not say we should take off 1mm per year to account for thermal expansion coming out of the LIA, and another 1mm for the changes to glaciers since LIA. The data is no longer what the name of the data says it is. The ACTUAL sea level rather than the ADJUSTED sea level is what is useful to people.

  29. These statistical ‘What-If’ pseudo scientists are very busy getting paid to demolish the reputation of science.

  30. The study is nonsense, because it completely disregards the well-known issues with the Mississippi Delta due to the way the river has been managed in recent years. Attributing issues such as subsidence of marshes to climate change and comparing the current situation with conditions from 7000 years ago while disregarding man-made conditions is disingenuous, to be kind.

  31. I will nominate this post for the 2020 Crock of Schist award. It is well known and proved that most of the relative sea level rise in the Miss. delta is because of thermal subsidence, a result of crustal cooling under this passive margin – a tectonic process. Crustal subsidence in the delta is much more rapid than the change in absolute sea level.

    As has been documented and analyzed at WUWT numerous times, the world-wide change in the elevation of sea level relative to the earth geoid, called eustatic sea level, is less than +2 MM per year as determined by tide gauges with long-term records.

    Something is missing in this report because any geo professor or grad student knows this, or, at least that once was the case.

  32. In addition to sediment diversion, (in upstream dams and at the modern outlet) oil, gas and salt withdrawls have also contributed to subsidence. Straightening channels helps promote tidal scour as well. So the Mississippi delta has multiple strikes against it.

    The Mississippi river has spent the Holocene moving across the landscape like a loose firehose, spraying sediment from one place to the next. Where it deposits sediments, the land advances, when the depocenter moves elsewhere, the sediment continues to compact, leading to saltwater intrusion and interdistributary bays.

    The rate of sea level rise does have an impact, but it has been minor in the Holocene Mississippi delta. That’s why they can’t see the known highstands in their record.

  33. Based on this article, the study is flawed since it fails to address the loss of land in the Chandeleur Islands. When the mouth of the Mississippi River shifted to the present course, the sediment inflow stopped. The result, the islands began to sink and shrink. The present outlet has had sediment loss due to restricting flood waters to the mouth of the river rather than letting the river banks be flooded over. The Mississippi River mouth should be located near Morgan City. The Corps of Engineering controls the water flow through to the Atchafalaya River. A new delta has now formed in the Atchafalaya Bay. The present river course is kept open because of the river traffic and keeping open the Port of New Orleans. River sediment is important to the life of the coastal marshlands of Louisiana. Cut it off, the natural compaction leads to the land sinking. This is an ongoing process since the Mississippi River was formed.

  34. The Chandeleur Islands were deposited by the Saint Bernard lobe of the Holocene delta. This lobe was active during the 1500 to 3000 BP time range. That is supposedly missing from their record.

    Take away the hype and their open-source article tells an interesting story of the last stages of the Holocene transgression, where the basal peats they dated show the transgression of the rising sea followed by delta progradation. The low rate of sea level rise they record is a measure of how much the sediment compensated for modest sea level increases. All of their sediments younger than 6000 years are listed as terrestrial or indeterminant.

    With an estimated precision in the +/- 0.5 meter range for ASL it really doesn’t add that much to the debate. Their accuarcy on sea level is biased, since some compaction will take place, regardless of their attempts to minimize. They should have considered the data as two separate sets based on geography, and included sediment density or % water.

  35. “The Mississippi between Cairo and New Orleans was twelve hundred and fifteen miles long one hundred and seventy-six years ago… Its length is only nine hundred and seventy-three miles at present.

    Now, if I wanted to be one of those ponderous scientific people, and “let on” to prove what had occurred in the remote past by what had occurred in a given time in the recent past… what an opportunity is here! Geology never had such a chance, nor such exact data to argue from! …

    In the space of one hundred and seventy-six years the Lower Mississippi has shortened itself two hundred and forty-two miles. That is an average of a trifle over one mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the Old Oolitic Silurian Period, just a million years ago next November, the Lower Mississippi River was upwards of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing-rod. And by the same token any person can see that seven hundred and forty-two years from now the lower Mississippi will be only a mile and three-quarters long…

    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.”

    Mark Twain, Life on the Mississippi

  36. The scary thing is that the present-day rate of global sea-level rise, due to climate change, has already exceeded the initial tipping point for marsh drowning

    Never mind their dubious conclusion that Mississippi marshes are suddenly more susceptible to a lower rate of sea level rise than earlier studies showed, they apparently can’t tell the difference between sea level rise and land subsidence. Land subsidence in the Mississippi Delta is twice the rate of sea level rise. So the biggest “problem” here, if there is any at all, is land subsidence, not sea level rise. See NOAA tide gauges around the delta here:

    https://tidesandcurrents.noaa.gov/sltrends/sltrends.html

  37. Sea level rising same as it has for thousands of years.
    Another bunch of twits being paid on taxpayer funding to lie about CO2.

  38. It’s funny that they try to claim they’ve adjusted for sediment compaction and subsidince, when their sea level curve is still typical for subsidince at a rapid depocenter.

    This latest study has three radiocarbon dates from the last 500 years. 146 years, 202 years and 342 years. The elevation of “sea level” at these three dates, at those sites, are -280, -300 and -350 mm below sea level ” respectively. Not clear how they estimate .35 – .36 mm/year subsidence rates for these three dates, but just using age and depth of the holocene surface below “sea level”, I calculate almost 2 mm per year for the last date, and 1mm per year for the earliest. The slight increase in subsidence since the little ice age could be real, or could just indicate the lack of sediment at that site, at that time.

    A “state of irreversible collapse? NOT. Katrina dumped multiple centimeters of sediment on the city of New Orleans in one event. Sure, dumping water and sediment into the city may not make economic sense, and the city will probably sink beneath sea level and remain dry due to levees and pumps. But elsewhere in south LA, flooding is how the land is built.

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