Study shows rapid sea level rise along Atlantic coast of North America in 18th century

Study found evidence for a period of enhanced pre-industrial sea-level rise of about 2-3 millimeters per year

University of York

The findings are based on sea level reconstructions derived from salt-marsh sediments from the Atlantic coast and from microscopic salt-marsh fossils. Credit: Prof Roland Gehrels, University of York

The findings are based on sea level reconstructions derived from salt-marsh sediments from the Atlantic coast and from microscopic salt-marsh fossils. Credit: Prof Roland Gehrels, University of York

The study, led by the University of York, found evidence for a period of enhanced pre-industrial sea-level rise of about two to three millimetres per year in three locations: Nova Scotia, Maine and Connecticut.

The researchers say that the large rises at these three locations were natural, and partly related to the North Atlantic Oscillation – a large-scale atmospheric pressure see-saw over the North Atlantic region – and to periods of enhanced ice melt in the Arctic.

The authors of the study say cities like New York and Boston will have to take into account this natural variability in planning for future sea level rise.

The findings are based on sea level reconstructions derived from salt-marsh sediments from the Atlantic coast and from microscopic salt-marsh fossils.

Previous studies have shown that, since the 1950s, rates of sea level rise along the Atlantic coast of North America were faster than the global average – leading to this region coming to be known as a sea level rise “hotspot.”

However, lead author Prof Roland Gehrels, from the University of York’s Department of Environment and Geography, said this earlier rapid episode of sea level rise in the 18th Century wasn’t known before.

“To find out what global warming is doing to sea levels today we need that base level from historical times.

“In the 20th Century we see rates of up to three or four millimetres per year, faster than in any century in at least the last 3000 years.

“In the 18th Century they were slightly slower, but still much quicker than you would expect for the Little Ice Age, partly because the Arctic was relatively warm during the 18th Century.

“It is pre-industrial so there are no anthropogenic forces – or human influences – at play, but in the 20th Century there may well have been.

“This means that those rapid episodes of sea level rise on the north east coast of North America in the 18th Century have a natural cause.”

Scientists say salt-marshes are good “archives” of sea levels as they contain several metres of sediment which contains data going back hundreds of years.

Prof Gehrels added: “The high rates in this “hotspot” could present significant coastal risks for large population centres if they are a persistent and recurring feature.

“The likely future sea level rise in places like New York City is expected to be considerably greater than the global average by the end of the 21st century.”

“Our findings suggest that enhanced rates of sea level rise along eastern North America are not only symptomatic of human activity, but might additionally arise from natural processes in the climate system.”

The findings are published in Geophysical Research Letters and involved collaboration with the University of Leeds; Durham University; Bangor University; the National Oceanography Centre, Liverpool; Woods Hole Oceanographic Institution, Massachusetts, USA; Old Dominion University, Virginia, USA; and the University of Siegen, Germany.

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From EurekAlert!

61 thoughts on “Study shows rapid sea level rise along Atlantic coast of North America in 18th century

  1. It will be interesting to see who dismisses this because it points toward natural variability as being a cause of sea level rise in certain locations.

    Regards,
    Bob

    • I sure don’t see it along the New Jersey shore, and haven’t noticed it at New York City. So where is the ocean rise?

    • There seems to be corroborating evidence demonstrated in the show about Oak Island, which is just off Nova Scotia. They’re digging up structures potentially built in the 1600’s, but far enough offshore that building them would have been beyond the technical capabilities of the time based on current sea levels.

      I’ll bet there might be other archeological evidence buried just off shore that would make it even harder to dismiss.

      • There is a large cache of treasure buried on Oak Island. Possibly by Blackbeard and his crew buried at the bottom of a deep well. It was famously booby trapped in at least six different ways to prevent digging down to the treasure.

      • What is really happening is post-glacial rebound. See https://spotlight.unavco.org/station-pages/chur/chur.html, which explains that Churchill Manitoba is rising at 1m per century (hence sea level is “dropping” at 1m per century) because not long ago Hudson Bay was under the huge weight of the Laurentide Ice Sheet. Note in Figure 12 on that page that Halifax was pushed up during the Ice Age – it is on a “peripheral fore-bulge” – but is now subsiding. Thus the mean sea level (relative to the land) is rising in Halifax at 33 cm per century, because Halifax land is dropping down at about 24 cm per century (there is probably some residual sea-level rise from the last Ice Age). That same site plots uplift and subsidence across the country.

  2. “Our findings suggest that enhanced rates of sea level rise along eastern North America are not only symptomatic of human activity, but might additionally arise from natural processes in the climate system.”

    They got that reversed. It would be more accurate to say “The rates of sea level rise along eastern North America are not only symptomatic of natural processes in the climate system, but might additionally arise from human activity.”

    • Exactly right, Paul.

      It’s that null hypothesis thingy.
      .
      .
      .
      Oh look! Over there! Climate Science® has stood the null hypothesis on it’s head.

      Now let’s see how many plates Climate Scientists® can keep spinning on those flexible sticks at the same time. Climate Science® is starting to become as entertaining as The Ed Sullivan Show.

      • I always have to remind people that if you see a “might” or “may”, there is the (often) unstated “might not” or “may not” to consider as well. Can’t have one without the other.

    • Most people believe that the bureaucrats do the bidding of the politicians but in reality it is the other way around. The Bureaucrats instruct the puppet politicians on what to say. It why the scientists invented teleprompters.

      Once Chuckie and Nancy and Bernie have regulated your individual liberty , including freedom of movement and stripped you of all your discretionary income, they are going to go right to work on installing that Global Thermostat in Washington DC which will control all that melting ice and stop the oceans from rising.

      Just like Barack Obama promised in his 2008 acceptance speech. He didn’t really mean the oceans would stop rising on his say so, although he was testing the waters. He just got so busy with national health insurance, driving up co-pays and deductibles and adding thousands of dollars to premium prices, for you and me, that he ran out of time for that whole rising tides problem.

  3. “Previous studies have shown that, since the 1950s, rates of sea level rise along the Atlantic coast of North America were faster than the global average – leading to this region coming to be known as a sea level rise “hotspot.””

    Actually no, but most of the Atlantic coast of North America is sinking, leading to a more rapid relative sea level rise.

    • I’d like to know how sea level rise could possibly be different between one part of the planet and another. That wet stuff is all connected, right? Tectonics, land subsidence, tides, etc…. How does one accurately measure a “global” rise of 3 mm? Just curious.

      • In the actual science that studies sea level changes – stratigraphy – there currently is no global sea level change. Sea level is at still stand – regional factors are overshadowing any eustatic changes by orders of magnitude.

      • PeteT
        “I’d like to know how sea level rise could possibly be different between one part of the planet and another. ”
        From NOAA’s website: Just as the surface of the Earth is not flat, the surface of the ocean is also not flat—in other words, the sea surface is not changing at the same rate globally. Sea level rise at specific locations may be more or less than the global average due to many local factors: subsidence, upstream flood control, erosion, regional ocean currents, variations in land height, and whether the land is still rebounding from the compressive weight of Ice Age glaciers.

        “How does one accurately measure a “global” rise of 3 mm? Just curious
        Tides stations and satellites.

  4. We need different terms to replace the hopelessly tainted “sea level rise.” This study shows “apparent relative local sea level rise” at best. What if an offshore sand bank disappeared and allowed more tidal salt water intrusion? What if a river changed course cutting new channels reducing fresh water injection? Glacial rebound? Lots of new species were being introduced changing the ecosystem and thus the hydrology. So many variables with large error bars.

  5. Earth crust thickness in the N. Atlantic is highly variable. In the coastal areas wher crust is thinner post-glacial uplift would be greater and vice versa.
    “About 7% of the ocean crust is 7 km thick and is interpreted to have been affected by excess magmatism. Thin crust probably reflects reduced melt production from relatively cold or refractory mantle at scales of up to hundreds of kilometers along the spreading axis. By far the most prominent thick crust anomaly is associated with Iceland and adjacent areas, which accounts for 57% of total crustal volume in excess of 7 km. Much smaller anomalies include the Azores (8%), Cape Verde Islands (6%), Canary Islands (5%), Madeira (<4%), and New England–Great Meteor Seamount chain (2%), all of which appear to be associated with hot spots."
    free access here: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2010GC003402
    …………..
    However, OT and of more immediate concern
    "Researchers at Peking University's School of Life Sciences and the Institut Pasteur of Shanghai, discovered the virus has evolved into two major lineages – dubbed ‘L’ and ‘S’ types.
    The older ‘S-type’ appears to be milder and less infectious, while the ‘L-type’ which emerged later, spreads quickly and currently accounts for around 70 per cent of cases.
    Genetic analysis of a man in the US who tested positive on January 21, also showed it is possible to be infected with both types. ….. 'It is usually the case that when RNA viruses first cross species barriers into humans they aren’t particularly well adapted to their new host – us!
    Thus, they usually undergo some changes allowing them to adapt and become better able to replicate within, and spread from human-to-human.' said Dr Griffin." – Daily Telegraph

  6. So there were rapid sea-level rises before the Industrial Revolution started. And consequently, there must have been times when the sea level dropped off again. And all this without humans influence. I just ask myself if Greta and her kin were asked if they are OK with this? Earth is an evolving system. And it will be until our sun swells to its giant phase and sterilizes this rock again.

      • Nah… It was the Scarlet Pimpernel wot dunnit.

        Leave Annie and Sandy (arf! arf!) out of it or Daddy Warbucks will have your hide.

        Wait up… we’re not talking about the same Anne here, are we?

  7. Dr. Curt Larson studied coastal peat bogs in the mid-Atlantic States and found that relative sea level has been rising at an average of about 1.6 mm/yr, with large changes up and down along the way, for the past 6,000 years.

  8. so they are taking cores..deposited by the ocean..in a salt marsh….that’s dry now

    uh huh…..

    • Without reading the paper, I would guess that they looked the surfaces of many places to see when they were last inundated and salt water incursion into the water table – then did a reconstruction of data that was all over the place.

      • Seeing as how this paper comes from the University of York could we say that the findings are a bit of a shambles? If so will we see blood on the Ouse?

  9. “Our findings suggest that enhanced rates of sea level rise along eastern North America are not only symptomatic of human activity…”

    Uhh no, your findings didn’t suggest that at all. Repeating dogma is how religion works, not science.

    • What the paper actully says is , “Our findings suggest that enhanced rates of sea‐level rise along eastern North America are not necessarily symptomatic of anthropogenic forcing, as was argued in past work (Sallenger et al., 2012), but might arise from other forcing mechanisms in the coupled climate system.”

      • Gee, you mean that Eureka Alert misquoted the original paper?
        Now why would they do that?

  10. It seems to me that glacial rebound must tend to decrease the radius of the planet. If you take your finger away from a balloon that you have been pressing the radius of the balloon shrinks.

    • Presumably “if you take your finger away from a balloon” the radius at your finger-dent increases a lot, while the radius everywhere else decreases a small amount.
      One could imagine an ice-age globe with very very low oceans, and very very high icefields. Average sea level radius would be lower, but average global radius would probably not change too much.

  11. Why is it that alarmists do not understand interglacials? Small temperature perturbations do not mean that melting should slow or stop. Take an ice cube out of your freezer and set it on the counter at 50F, then turn the thermostat down to 40F. Does the ice cube continue to melt?

    After the nonsense I have witnessed over the past 40 years, I am convinced that all climatologists should first be required to get a geology degree. They do not have the needed perspective to properly view interglacials.

  12. zzzz indeed … All based on what that hand-cranked auger shows? Someone’s risking some kind of repetitive strain injury there. Makes my back ache just looking at the picture. What if it is the layer below the swamp that is moving?
    There are 42 tide gauges in my corner of the planet (Queensland). They all show slightly different values and trends, even ones in the same tide race. None are necessarily wrong. Coastal topography changes, El Nino/La Nina effects. The tectonic plate is moving north by east at about 70mm a year. If it keeps going it will close the flow-through between the Pacific and Atlantic, and that will result in some significant change.

    • Yes, they should try using a sonic core rig. Much better samples in soft sediments and they would be finished in a fraction of the time taken to do hand-auger holes.

  13. Give me a break SLR at the Battery tide gauge in NYC is 2.87mm per year since 1869 according to NOAA.

  14. I have not yet studied this particular paper in detail, so this comment might apply only to many other papers on sea level change.
    An important variable often overlooked is the thickness of the sand as it varies over time. At a given location like a tide gauge or a drill hole for sampling, the sediment or sand has had sideways movement as well as movement perpendicular to the coastline, so the regional stock of sand is re-distributed, sometimes massively in big storms. Its thickness varies from site to site even for sites a few metres to kilometres apart. Therefore, the link between sand top surface height and sea top surface height and tide meter height is complex and probably incapable of historical reconstruction to the desired accuracy.

  15. I have to go back and find the studies but there was one from the University of Prince Edward Island (Canada) from the 1950’s I looked up when the Toronto Star newspaper did a big enviro-piece 6 months or so ago on this suppossed catastrophic sea level rise.

    It said that the coastal areas from north of New York City to New Brunswick – P.E.I were subsiding 2-4 mm per year from the effects of the release of the weight of the glaciers from the interior. Nopefully backsoon with the references, unless someone else beats me to them.

  16. I remain skeptical that anyone can estimate sea level or temperature rise or fall from two hundred years ago to any real accuracy with any technology we possess.

    • Wight Mann, I don’t think they can estimate sea level & temperature changes TODAY accurately, let alone 200 years ago. By that I mean regionally or globally averaged changes, not the diurnal ones we are familiar with.

  17. In the late 70’s I did some environmental work. Apparent sea level increases at the time were believed to be due to beach erosion caused by man building sea walls.

    Seawalls have been built for thousands of years. A 7,000-year-old structure intended to protect settlements as sea levels rose in the Mediterranean . Its under water today.

    Sea levels have been increasing the entire holocene. Don’t worry, the next glacial period (due anytime in the next 5000 years) will reverse that, and sea levels will drop over 20 meters or more

  18. “Our findings suggest that enhanced rates of sea level rise along eastern North America are not only symptomatic of human activity, but might additionally arise from natural processes in the climate system.”
    ==============
    Define “climate system”.
    Then we’ll work into the geology…..

  19. 2 to 3 MILLIMETERS per year!!!!!!!!!!!!!!!!!!!!!!

    Who thinks this is real?

    Maybe those 20 somethings with their entitlement and participation PhDs.

  20. I recall reading that the distance between North America and Africa is slowly decreasing. Could that have anything to do with the sea level rise?

  21. Call me flippant, but really, can’t these people find more meaningful employment – you know, produce stuff or service that makes someone a wee bit better-off? Who cares about 3mm rates of sea level rise? And if you do care then what are you going to do about it? Sea level rises and falls. Zzzzzzzzzzzz

  22. As the actual Arctic is a floating piece of ice rather than land, as I understand it, any change to the Arctic’s ice mass would not in any way, affect the sea-level, according to Archimedes of Syracuse (Archimedes’ Principle).
    Based on the researchers’ claim, it seems that we would have to assume that the authors were referring to something more than the actual Arctic, like maybe all land and ice within the Arctic Circle as being the Arctic(?).

  23. The NOAA website makes no sense. It says:
    Sea level rise at specific locations may be more or less than the global average due to many local factors: subsidence, upstream flood control, erosion, regional ocean currents, variations in land height, and whether the land is still rebounding from the compressive weight of Ice Age glaciers.

    How does local subsidence cause ocean levels to rise? They can’t, unless it’s on a massive scale, either tectonic or orogenic. Instead of heeding their own words of caution, the measurements are incorrectly reported by NOAA, hoping no-one will notice. They never state that the datum has moved. Instead of reporting that the apparent change in sea levels is due to subsidence, they imply that the land datum is fixed and the relative movements are all due to sea level rise. NOAA won’t admit that islands on coral atolls in the South Pacific are sinking into the South Pacific, not the other way round. They are sinking is exactly as Darwin said they would. However, the myth must be maintained by NOAA at all costs.

    What has upstream flood control got to do with sea levels? If the gauges are in river mouths, they should not be using this data for global studies. That should only be used for shipping.

    How does one make sense of the statement that “variation in land height affect tide levels”? In the words of Fermi, it’s not even wrong.

    If “the land is still rebounding from the compressive weight of Ice Age glaciers”, then it should be reported as such, not as a change in sea levels. But they don’t.

  24. “The researchers say that the large rises at these three locations were natural, and partly related to the North Atlantic Oscillation – a large-scale atmospheric pressure see-saw over the North Atlantic region – and to periods of enhanced ice melt in the Arctic.”

    That has to be negative NAO, but they don’t say which decades of the 18th century.

    • There were studies on this I haven’t found time to retrace yet. The coastal area from just north of New York City is descending 1-4mm /year if my memory is right. This has been known since the 1950’s. The largest change downward is at the northern end at New Brunswick- Prince Edward Island. The coastal area was pushed up as the inland areas were depressed from the weight of the 1-2 miles of glacial ice that covered the interior.

      The simple way to visualize this process (for teachers of geology) is to make a circle with your thumb and index finger. put a small piece of paper over the “hole”, and lightly press down the paper over the middle of the hole. paper outside the hole tilts up as the center depresses. Release the pressure on the center, and as it rises the outside of the paper falls again.

      It only looks like sea level rise, if you don’t take into account the possibility that the land may be depressing.

  25. I am confused? Why is this article characterizing a period of 2 to 3 mm annual sea level rise as exceptional?
    Isn’t that precisely the long-term average of sea level rise?

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