Study finds global sea levels rose up to 5 meters per century at the end of the last 5 ice ages

post-glacial_sea_level-incl-3-mm-yr-1-trendFrom the University of Southampton

 

Land-ice decay at the end of the last five ice-ages caused global sea-levels to rise at rates of up to 5.5 metres per century, according to a new study.

An international team of researchers developed a 500,000-year record of sea-level variability, to provide the first account of how quickly sea-level changed during the last five ice-age cycles.

The results, published in the latest issue of Nature Communications, also found that more than 100 smaller events of sea-level rise took place in between the five major events.

Dr Katharine Grant, from the Australian National University (ANU), Canberra, who led the study, says: “The really fast rates of sea-level rise typically seem to have happened at the end of periods with exceptionally large ice sheets, when there was two or more times more ice on the Earth than today.

“Time periods with less than twice the modern global ice volume show almost no indications of sea-level rise faster than about 2 metres per century. Those with close to the modern amount of ice on Earth, show rates of up to 1 to 1.5 metres per century.”

Co-author Professor Eelco Rohling, of both the University of Southampton and ANU, explains that the study also sheds light on the timescales of change. He says: “For the first time, we have data from a sufficiently large set of events to systematically study the timescale over which ice-sheet responses developed from initial change to maximum retreat.”

“This happened within 400 years for 68 per cent of all 120 cases considered, and within 1100 years for 95 per cent. In other words, once triggered, ice-sheet reduction (and therefore sea-level rise) kept accelerating relentlessly over periods of many centuries.”

Professor Rohling speculates that there may be an important lesson for our future: “Man-made warming spans 150 years already and studies have documented clear increases in mass-loss from the Antarctic and Greenland ice sheets. Once under way, this response may be irreversible for many centuries to come.”

The team reconstructed sea-levels using data from sediment cores from the Red Sea, an area that is very sensitive to sea-level changes because it’s only natural connection with the open (Indian) ocean is through the very shallow (137 metre) Bab-el-Mandab Strait. These sediment samples record wind-blown dust variations, which the team linked to a well-dated climate record from Chinese stalagmites. Due to a common process, both dust and stalagmite records show a pronounced change at the end of each ice age, which allowed the team to date the sea-level record in detail.

The researchers emphasise that their values for sea-level change are 500-year averages, so brief pulses of faster change cannot be excluded.

###

The study was funded primarily by Natural Environment Research Council (NERC) and the Australian Research Council (ARC).

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56 thoughts on “Study finds global sea levels rose up to 5 meters per century at the end of the last 5 ice ages

  1. Professor Rohling speculates that there may be an important lesson for our future: “Man-made warming spans 150 years already and studies have documented clear increases in mass-loss from the Antarctic and Greenland ice sheets. Once under way, this response may be irreversible for many centuries to come.”
    How does “man made warming” span 150 years ?
    What “mass loss” studies, please ?
    Things that make you go “Hmmmm …”

    • Has to be said. That is the entry fee to the game, if you write something that can be seen, even mildly to debunk “the icebergs are melting” shrieks.

    • When the seeming irreversibility of large-scale ice-age termination is baldly projected onto small-scale ice-mass variations during an interglacial, it makes you go “What???”

    • Yeah, the Professor has no business putting in unattributed assertions into papers. EACH of these statements should be accompanied by a footnote to its source.
      This is REALLY bad science to put stuff in as background/introductoory material without sourcing it. HIS PEER REVIEWERS SHOULD HAVE SLAMMED HIM FOR THAT.

  2. So now they are claiming that man made warming spans 150 years implying that the puny co2 emissions of the era were responsible for ending the little ice age ! And they wonder why people are sceptical.

    • It’s well known that CO2 can do anything, and that includes going back in time. With Professor Rohling’s insight, it now seems obvious: the end of the LIA wasn’t natural, it was caused by the growth in sales of SUV’s in the late 20th century.
      A bit more seriously: it’s often claimed that climate change causes everything, particularly if it’s unpleasant. But one thing is clearly true: climate change causes many people to go mad. And that includes university professors.
      Here’s the real madness. Professor Rohling and co. are talking about what happens at the end of ice ages. When an ice age ends it’s obvious that the ice will continue to melt for hundreds and thousands of years. It’s what ice ages do. Last time I checked, the last ice age ended quite a long time ago. We’ve been very fortunate to live in a long interglacial period. So how can the melting at the end of the last ice age tell us anything about what will happen in the next few hundred years?
      Chris

  3. The paper is paywalled, so I haven’t been able to read it, but like all Rohling´’s previous studies this is based on salinity levels in the Red Sea, which in turn depend on the depth and width of the Bab el Mandeb strait. This is assumed to have remained unchanged for 500,000 years, though being in a very seismically active area and despite such stability being almost unheard of even in seismically quiscent areas.
    It should be noted that “twice the modern global ice volume” means a 70-80 meters lower seal-level, i. e. full ice-age conditions. The ice volume has as far as known never reached three times the modern global ice-volume.
    It is also unclear to me how they manage to reach such extreme precision in dating, which is difficult even within the range of radiocarbon dating.

    • In the Results section, they write:
      It is pertinent to briefly discuss the extent to which the Red Sea
      RSL record approximates global (eustatic) sea level (ESL). RSL
      reconstructions are, by definition, representative of sea-level
      changes at a particular geographic location. Any isostatic and
      tectonic effects on site elevation will result in deviations of the
      respective ‘uncorrected’ RSL signal from ESL. The Red Sea RSL
      record technically represents sea-level fluctuations at Hanish Sill
      (RSLHS), the hydraulically limiting ridge at the southern entrance
      to the Red Sea. Isostatic changes in Hanish Sill depth are
      implicitly accounted for in the hydraulic model used to convert
      Red Sea d18O to sea level, by scaling the model to the ESL glacial–
      interglacial range indicated by coral sea-level data29. Tectonic
      changes have been considered in the Red Sea RSL model and
      are supported by subsequent work, which concluded that
      vertical tectonic stability characterized the Hanish Sill region for
      at least the past 120 kyr.
      On your second question of timing/precision, they write in the Intro (and detail it in the Results):
      …(W)e address the above issues with a new chronology
      derived from a U/Th-dated speleothem d18O record, for a
      continuous, high-resolution record of Red Sea RSL4 over five
      complete glacial cycles (500 kyr). Our new approach relies on
      synchronizing a distal monsoon signal with both dust and sea level
      records; hence, it employs different criteria than the recent
      age model development for this record over the youngest 150 kyr
      (ref. 5). That approach, which correlated (proximal) source-water
      and sea-level-equivalent d18O records, achieved smaller
      uncertainties, but could not be extended to older ages
      (Supplementary Note 1). We link our new chronology over the
      older interval (150–500 kyr) to previous results for the last 150 kyr
      (ref. 5). By transferring a U/Th chronology to the entire 500 kyr
      Red Sea RSL record, and propagating quantifiable sources of
      uncertainty, we can investigate how the global glaciation state
      (total ice volume) affects potential maximum rates of sea-level
      rise. An additional (major) benefit is that it provides the first
      chronologically independent sea-level record for future
      investigations of ice-volume phasing relative to insolation
      (orbital) and polar climate forcing over multiple glacial cycles.
      Finally, we synchronize an Asian dust-flux signal with our new
      chronology; hence, our final dataset comprises records of sea-level
      change and Asian summer and winter monsoon intensity on the
      same timescale, spanning five complete glacial cycles. Although
      many hypotheses exist regarding connections between changes in
      ice volume and monsoon intensity, detailed understanding of
      this relationship is lacking. This is partly due to the fact that
      previous hypotheses relied on benthic d18O ice-volume proxies
      and/or poorly defined ice sheets in monsoon models. Our
      approach improves the capacity to distinguish the relative
      impacts of orbital forcing, ice volume and rates of ice-volume
      change on monsoon variability.

    • Are you SERIOUS? This guy does Red Sea studies and then projects land ice sheet extent from it?
      As someone a little north of there was heard to say one day, “OY VEY!”

  4. “once triggered, ice-sheet reduction (and therefore sea-level rise) kept accelerating relentlessly over periods of many centuries.”
    Sounds more like Per Bak’s sand pile chaos than determinate based on some idea fanciful idea of a long-interglacial period of equilibrium.
    The self-organised sand pile system Per Bak introduced are:
    The system is open and dissipative, and its components are metastable.
    The system organises itself in a critical state with avalanches of change at all sizes via which dissipation manifests itself. These avalanches are regular but not periodic.
    The system is embedded in a single spatiotemporal fractal structure.
    A critically self-organised system might become catastrophically unstable if it were manipulated and forced into certain optimal states which take it out of its self-organised state.
    (From: http://jasss.soc.surrey.ac.uk/4/4/reviews/bak)

  5. “Professor Rohling speculates that there may be an important lesson for our future: “Man-made warming spans 150 years already and studies have documented clear increases in mass-loss from the Antarctic and Greenland ice sheets. Once under way, this response may be irreversible for many centuries to come.”
    The assumption of man-made global warming invalidates this “scientist’s” paper. There is not a single paper that conclusively shows that man has caused the temperature rise started with the end of the little ice age. I wonder if the good doctor thinks that mankind also ended the little ice age. With prayer perhaps?
    I also wonder why so many, many people buy into the Sagan-Hansen hypothesis that CO2 has a net warming effect that is large and measured. Piffle, I have seen no credible argument and data that shows CO2 to be anything but plant food.
    I also wonder why so many, many people think that an end to this present ice age and a return to a much warmer time would be bad. Is it just resistance to change? What would be bad about the relatively warm climate of Florida extending up into Canada? (other than a bunch of Yankees having to buy A/C for their homes) Don’t misunderstand me; I don’t think we are going to see a warming at all, but just wonder why people think that warm is bad.

    • Mark,
      I fully agree. A warming of a degree [C or F] is to be welcomed. Two, likewise.
      Longer growing seasons – to feed our 7.2 billion-plus population, which is still growing by about 80 million a year – a new Germany- or Iran-equivalent each year.
      A reduction in winter heating needs at the latitude of London (warmed by the gulf stream), and north of there. South of here, too, in big continents – Iran, say, gets plenty cold in winter, especially up I the mountains. I gather Montana does, too.
      There will be down sides – some pesky insect nuisances/killers extending north – Asian Gypsy Moth, Anopheles, some of the nastier hornets, and so on.
      But climate changes.
      It has always changed.
      Until the Sun goes Red Dwarf – billions of years from now, so certainly after my time – climate will continue to change.
      And my immediate fear – twenty-five years, or more, of falling temperatures.
      When we are ‘de-carbonizing’ our energy supply.
      In the UK, the Right Honourable Muppet Ed Miliband [two L’s? Don’t care] – if elected next year, will kill thousands of pensioners every year with his proposed de-carbonisation by 2030 policy/dream/nightmare. We will have windmills sprayed across the land.
      And. if there is no wind, the windmills won’t produce any power, and the little old ladies and gentlemen will freeze to death in their homes.
      Millipede will probably excuse this by saying they’re more likely to vote against Socialism, and – guess what – the UK r e a l l y needs a socialist state.It didn’t work too well for Russia, or China [although there they seems to still have A Communist Party calling the shots.
      Talking of which, Mao would probably have them all shot . . . .

  6. Sorry, but I must be missing something here.
    “Those (time periods) with close to the modern amount of ice on Earth, show rates of up to 1 to 1.5 metres per century.”
    Current estimates are that sea level is rising at around 3mm per year = 30cm per century. Or put another way, about one quarter of the rate identified at a time when mankind cannot possibly have had an influence on climate.
    Is that what they are saying?

    • Following on from your comment. It therefore means that to fall outside the bounds of ‘natural variability’ sea level would have to rise at more than 1.5 m/century or 15 mm/year. We can all relax. Thank goodness for this excellent paper.

  7. “Those with close to the modern amount of ice on Earth, show rates of up to 1 to 1.5 metres per century.”
    Soooo, with the modern warming the sea level rise is about 3 mm per year or .3 metres per century. That means that modern warming is creating a sea level rise rate of less than 25% of the usual amount.
    So even if humans were responsible for all the sea level rise it’s still around 25% of natural variability. Exactly what am I supposed to be worrying about?

  8. No data as to whether the sea level changes were to do with land movement.
    The latest satellite data shows 1.5mm/a to a negative rise, ie., a sea level fall.

  9. In 70 centuries SL rose 110 meters, but that was 70 centuries ago as well. Since then not so much, bouncing around 2-4 meters up and down. Now that we are at .3 meters a century SLR, it is a crisis as only the Anthropocene can be perceived as. Send more money get more scary stories.

    • Tony, there is convincing evidence that the Holocene high stand during the Early Holocene Warm Period may have been as much a 1.5 meters above the present level. The uncertainty is considerable due to potential confounding factors but sea level present is in reality lower than it was 8,000 to 7,000 years ago. Data from Texas, Micronesia, Australia, Brazil and other locations supports this. There is also evidence from the Seychelles IIRC. This period corresponds with clear climate shifts in western North America that saw in a much drier period with the sagebrush high-desert community of the northern Great Basin pushing as far west as Mount Jefferson in Oregon.
      On another note, your article was quite interesting. One point that should be considered is that if the loss of Lyonesse was in truth a folk memory, then the element of the myth that attributes the loss to treachery due sabotage of an engineered system to drain Lyoness and maintain the land – similar to the Netherlands – may well be worth a thought too.

  10. Actual changes could e quite recent, consider Dunwich (I think I have that right) a drowned village off the coast of Norfolk, the Goodwin Sands (previously Goodwin Farms) and Rye, Winchelsea and Camber Sands.
    We don’t really need to consider whether or not “Tenterden Steeple” is the cause of the Goodwin Sands, but Rye and Winchelsea were thriving ports until quite recently – see Captain Blood! Rye was, I think, one of the Cinque Ports, which makes its retreat from the sea since Napoleonic times.

    • Actually you have it backwards. Old Winchelsea , Dunwich and New Romney were all major ports until the 13th century when affected by the great storms that marked the end of the Mediaeval warm period and the onset of a period of savage cooling. The great storms of the winter 1286/1287 swept old Winchelsea away, changed the course of the Rother leaving New Romney a mile inland and finding its new outlet at Rye marking its rise as a new port. This happened in the same time frame as the decline of the Greenland settlements.
      Rye remains a port to this day with Rastrum Wharf being recently renovated and handling coastal vessels up to 220 ft in length. It is also a major yachting centre.

      • Not disagreeing with the rest of your comments but the period of savage cooling was short lived. There were long parts of the 14th century that were as warm as the MWP and it could be thought of as an extension of it.
        The 15th century seems to have been the first sustained dip into the LIA .
        However, turbulence did characterise much of the period in contrast it seems to the relatively settled MWP.
        tonyb

  11. Reblogged this on gottadobetterthanthis and commented:
    Remarkable data.
    It is interesting to see the author of the paper keep up the alarmism despite statements like this:
    “Time periods with less than twice the modern global ice volume show almost no indications of sea-level rise faster than about 2 metres per century. Those with close to the modern amount of ice on Earth, show rates of up to 1 to 1.5 metres per century.”
    Co-author Professor Eelco Rohling, of both the University of Southampton and ANU, explains that the study also sheds light on the timescales of change. He says: “For the first time, we have data from a sufficiently large set of events to systematically study the timescale over which ice-sheet responses developed from initial change to maximum retreat.”
    “This happened within 400 years for 68 per cent of all 120 cases considered, and within 1100 years for 95 per cent. In other words, once triggered, ice-sheet reduction (and therefore sea-level rise) kept accelerating relentlessly over periods of many centuries.”
    ————————————-
    That sounds to me like it is outside the bounds of reasonable expectations to think that our current world configuration could lead to a circumstance of over one meter rise per century. It certainly seems to me that people are smart enough to deal with that. Plus there is the fact that sea level change rates are constant or declining while we’ve taken good measurements.
    Mostly, there is nothing happening on earth in the industrial age that has not happened many times before, before humans could possibly had anything to do with it.

    • The cyclic collapse, retreat, and build up of the Lake Agassiz syste, with its episodic releases would have been quite dramatic. The releases were likely spectacular as the Larentide ice sheet retreated. That was truly a period of catasrophic Climate Change, no human CO2 required.

      • Maybe it all happened with the speed of the ongoing ‘collapse’ of the WAIS – ie nothing that you would notice in a human lifetime.

  12. One of the great mysteries to me is the Laurentide Ice Sheet. I still havent seen any description of how quickly it disappeared. It seems to have gone very quickly though. This study appears to show that something somewhere melted very quickly.
    So, can anyone explain to me, how the sun, which burns at a steady rate, was able to permit this massive ice sheet to build up to a level that it pressed down and created the Great Lakes? I think that the average temp in July in Chicago gets up to around 27C, how could there be a massive ice sheet there only 12 thousand years ago?
    And what changed to cause it to melt?
    Why are we worrying about a change of 0.1C per decade or whatever it is, when the changes at the end of the last Ice Age were swift, vast civilisation threatening events? Who is to say it wont happen again very soon? Shouldnt we be trying to find out what happened, rather than worry about our CO2 output which cant go on rising anyway because we are running out of fossil fuels?

    • Milankovitch cycles for starters. Also Internal non-linear climate dynamics likely move the system between mini-states within the inter-glacial (no external forcing required). Also the large freshwater melt pulses through the Mississippi and then finally a quite large series of releases through the St Lawrence changed Atlantic Ocean heat transfer circulations (temporarily shutting down the AMOC and Gulf Stream warm water supply to Northern Europe and UK-Ireland. It was, on a millenial, century, and and decadal time scales quite chaotic.

    • Dave: Good questions! One thing to remember is the thickness of the ice sheet, often said to be a mile. So the top of the ice sheet would be over a mile above sea level, and the air temperatures at that high surface would be far colder than they would be at the land surface.
      Also, once there, the glacier is reflecting far more of the sun’s energy back into space than land and vegetation would.
      So what changed? The most commonly given explanation is, as Joel just said, Milankovitch cycles. Earth’s orbit changed so that there was more intense spring/summer sunlight there to melt the glaciers more, with various feedbacks amplifying the effect.
      There could be various other factors in play as well. The ice core data shows a significant increase in dust before each warming cycle. This would have the effect of lowering the albedo of the glaciers, so they would absorb more sunlight.
      One idea that is starting to get attention is the slow depression of the earth’s crust during glacial periods causing the elevation of the glacial surface to get warm enough to start to melt (and the flip side is that the slow rebound of interglacials gets the land high enough that snow does not melt in the summer, allowing glaciers to start.

      • Curt,
        these Milankovitch cycles seem like an unproved theory. Is there a model that shows how they work and can they predict the next Ice Age? I think not, and to me this theory is of little use, either in prediction or explanation for what happened.
        Whether I am right or not about this to me isn’t important. What I do think that we need to do is find out what really caused that ice sheet to build up, and what caused it to melt, be that Milankovitch cycles or something else. It seems to me that whatever happened is a climate change elephant, certainly compared to the man made CO2 climate change.

    • “It seems to have gone very quickly though. This study appears to show that something somewhere melted very quickly.”
      It actually took about 10,000 years, from 18,000 BP to 8,000 BP. Not so very fast really.
      MWP-1A “Meltwater Pulse IA” was quite abrupt, with something like 15 meters of sea-level rise in about 300 years. However it is not known where the water came from. Both Antarctica, the Laurentid Ice and the Barents Sea ice have been suggested.

  13. If you go over to the Guardian climate section comments you will often find ignorant people who inform sceptics “but sea level is rising”. When I used to comment there I often told them sea level has been rising for thousands of years.
    On a side note since there is global ice thermal meltdown you have to wonder why the rate of sea level rise has not accelerated. It’s actually worse than it seems. LOL.

    Abstract – 23 February 2011
    Sea-level acceleration based on US tide gauges and extensions of previous global-gauge analyses
    It is essential that investigations continue to address why this worldwide-temperature increase has not produced acceleration of global sea level over the past 100 years, and indeed why global sea level has possibly decelerated for at least the last 80 years.
    http://www.jcronline.org/doi/abs/10.2112/JCOASTRES-D-10-00157.1
    ==================
    Abstract – July 2013
    Twentieth-Century Global-Mean Sea Level Rise: Is the Whole Greater than the Sum of the Parts?
    ………..The reconstructions account for the observation that the rate of GMSLR was not much larger during the last 50 years than during the twentieth century as a whole, despite the increasing anthropogenic forcing. Semiempirical methods for projecting GMSLR depend on the existence of a relationship between global climate change and the rate of GMSLR, but the implication of the authors’ closure of the budget is that such a relationship is weak or absent during the twentieth century.
    American Meteorological Society – Volume 26, Issue 13
    http://dx.doi.org/10.1175/JCLI-D-12-00319.1
    ==================
    Abstract – January 2014
    Global sea level trend during 1993–2012
    [Highlights
    GMSL started decelerated rising since 2004 with rising rate 1.8 ± 0.9 mm/yr in 2012.
    Deceleration is due to slowdown of ocean thermal expansion during last decade.
    • Recent ENSO events introduce large uncertainty of long-term trend estimation.]
    … It is found that the GMSL rises with the rate of 3.2 ± 0.4 mm/yr during 1993–2003 and started decelerating since 2004 to a rate of 1.8 ± 0.9 mm/yr in 2012. This deceleration is mainly due to the slowdown of ocean thermal expansion in the Pacific during the last decade, as a part of the Pacific decadal-scale variability, while the land-ice melting is accelerating the rise of the global ocean mass-equivalent sea level….
    http://www.sciencedirect.com/science/article/pii/S0921818113002397

  14. Since they have estimated sea levels for 500,000 years including four ice ages, why didn’t they show their data for the periods of fast declining rates? I would like to know when we can expect the next ice age to begin.

  15. sea level goes up… sea level goes down.
    wow… lets alert all the soft rockers someone is finally reading their research papers.

  16. I am checking the rate of sea level rise after the last five Ice ages and I estimate that at the estimated sea level rise professed by Dr Grant at 5.5 meters per century(18 feet) the sea level would have taken 5,500 years to reach Nineveh in Iraq when that city was established as the capital of the Assyrian Empire. Nineveh is now 1000 feet above today,s sea level. By extension of that argument the sea level would have taken 93800 years to rise to the top of Mount Ararat in Turkey. Mount Ararat is 16900 feet above sea level today. I wont bother to calculate how much time sea level would have taken to reach the Top of Mount Everest for I think you get the picture. The Ice ages as well as Isostacy have to be carefully examined in the light of what we know today. Unfortunately we know just as much today as we did when Darwin first observed what he termed “Raised Beaches” That simple error in deduction has lead us astray. The result is the Ice age and Glacial or Post Glacial Rebound or Isostacy. It is all figmented by the likes of Jameison and Agassiz and has to be debunked along with rising sea levels. We have to discard these outdated figments of imagination and get to the reality of what is really occuring otherwise we just keep adding more mythology to an original mistaken Darwinian concept. Richard Guy https://xbraille.wix.com/receding-seas

  17. False premisses. Landrise speed higher in areas where the ice melting started later. Landrise speed higher initially and then slowing down. BUT due to tectonical plates the landsinking makes areas south of a place where the landrise speed slowed down to zero and/or in areas on same tectonic plate south of that line in Northern Hemisphere. In southern Hemisphere there are diverge effects on places mentioned (estimated sealevels).
    The actual change close in time of the ice melting was a change in sealevels which at same time in northern parts of a tectonic plate could be up to 54 meters (fifty four) all factors analysed and in south of same tectonic plate up to 43 meters landsinking. That’s due to Archimedes principle. One of the best example of the total effect for a rather short distance – less than 400 kilometers apart – was found while studying English channel comparing that with Lake Vaettern (middle of south Sweden) landrise in north – landsinking in south.
    Northern shore of Lake Vaettern was 12 m above the southern shore and 43 m below Vaetterns current beach line Source: Johansson Inger E, Waterways towards Lake Roxen in older Ages, C-essay History Linköping University 1993 figures origin: Håkansson Lars, Ahl Thorsten; SNV PM740 NLU Rapport 88 , Uppsala 1976, page12 ff (SNV= Swedish Environmental Protection Agency)

  18. What is the fractal dimension of all the sea level rise episodes? (Gradient of nlog frequency over nlog magnitude)

  19. Excellent so a mile of ice over half the northern hemisphere gives us 5.5 meters a 100 years! so the few percent of that ice that we have now IF it melted would give a few percent of 5.5 meters, ormaybe 10 mm every 100 years?? from melt, Im good with that!!

  20. The beginning of global warming:
    150 years ago was 1864 –
    On Sept. 2, 1864 Union General William T. Sherman captured Atlanta and days later burned much of the city.
    Who knew?

  21. Just discussing this with a friend at Southampton Uni. Where did the opening diagram come from as I can’t seem to see it in the report for which I have the following link: http://www.nature.com/…/ncomms4635/full/ncomms4635.html

  22. Hey, I thought 5 meters of sea level rise would be a huge problem to our coastal cities. Now I understand it happens all the time! Thanks, folks!

  23. Interesting and very actual topic, indeed. We are really risking our lives by not paying attention to what we are doing to our planet…. In addition to that, I have also studied another topic, linked to this one: all the recent wars led by humans are also responsible for the climate change and global warming process. You can find more about that here: http://www.1ocean-1system.de/Chapter_e.pdf

  24. Shall we do a little basic math here?
    “An international team of researchers developed a 500,000-year record of sea-level variability…”
    ““This happened within 400 years for 68 per cent of all 120 cases considered, and within 1100 years for 95 per cent.”
    500,000 divided by 120 events equals ~4,166 years per event, on average. That is NOT very long in between RISES.
    And THEN the time for the changes to take place was 10% of the interval till the NEXT sea level RISE? 68% of the time? And then there was the 95% which happened within 1100 years which is 26% of the whole interval between sea level RISES.
    Why did I capitalize “RISE” and “RISES”? Because one has to consider that between many of the rises were also sea level FALLS.
    With rises AND falls, it sounds like much of – if not MOST OF – the time that sea level is either rising or falling, but not both. If the sea level fall times are roughly equal to the sea level rise times (they may be longer), then we have a situation on our planet where about 50% of the time or more is spent in rising or falling sea levels, meaning only about half the time (if that) the sea levels are static. Perhaps less static durations – depending on how long the sea level falls took.
    And don’t forget, that if 95% occur within 1100 years, 5% take LONGER.
    All of this makes me become very skeptical of this paper.

  25. There is information worth investigating from archaeology. From memory:
    – submerged areas off the east coast of the US, noted in the book “Across Atlantic Ice” whose theory is that North America was first populated by people from central west coast of Europe who travelled along the edge of the ice as an ice age faded. (They think that people came from Asia along the west coast a few thousand years later, and via Siberia and Alaska also later – some debate about when the combination of a land bridge and an ice-free corridor south actually existed at the same time.) On either coast the archaeological challenge is cost of looking underwater.
    – reports from the west coast of BC of changes in spear points as cessation of sea level change greatly affected fresh exposing of rocks.
    – investigation now going on to check suspicion that there are rock structures now underwater off the coast of Haida Gwai/Queen Charlotte Islands, of type known to have been created by tribal people to enhance/harvest marine life at river mouths. Sonar data captured last summer is now being analyzed.
    But caution is needed to distinguish sea level rise from ground collapse as a cause, the latter happened to an area of Lake Cowichan in the 1940s – caused by an earthquake, a double shock to a tribal group whose village was on the shore.
    I don’t know if the village now submerged under Esquimalt Lagoon east of Victoria BC was due to ground collapse or sea level rise, a few thousand years ago IIRC.
    (As with many other civilizations, west coast tribal groups located near the water, in their case especially to be near the sea life they harvested, and like many others for water as means of transportation using water craft (in those two cases canoes formed by hacking out the centre of cedar logs were common). But as around the world, defensibility was a factor, so settlements may have been seasonal.)

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