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And so castles made of sand fall in the sea, eventually

Posted on 16 March 2011 by jlweiss

Guest post by Jeremy Weiss, lead author of Implications of Recent Sea Level Rise Science for Low-elevation Areas in Coastal Cities of the Conterminous U.S.A.

1967. Jimi Hendrix writes a melancholy poem, reverses guitar tracks, and records a classic hit. By all accounts, he isn’t thinking about rising sea levels.

For cities and towns along the coasts of the U.S.A. – our castles, if you will – we weren’t thinking of rising sea levels in 1967 either, much less the potential impacts from the creeping phenomenon.

Fewer than 50 years later, however, we are thinking about worsening prospects for erosion, temporary flooding, and permanent inundation in low-lying areas of numerous coastal municipalities. Impacts of higher sea levels for the lowest elevations in these areas may not arrive in 25 years or 50 years, but possibly in 90. Eventually.

We think about this now because our knowledge of global sea level rise as a result of human-caused climate change has grown rapidly in recent years. Independent estimates now indicate that global sea level could be 1 meter (3.3 feet) higher by 2100.

In a study recently published in Climatic Change, we delineated low-lying coastal areas of the conterminous U.S.A. that may confront impacts from rising sea levels. We found that an average of 9% of the land area in coastal cities and towns lies at or below 1 meter of elevation and is connected to the sea. For highly populated municipalities – those with more than 300,000 people – land area percentages at or below 1 meter are greater than the national average in New Orleans, Virginia Beach, VA, Miami, and Tampa, FL.

But is the amount that sea level rises over the next 90 years the only sea level issue to consider by century’s end? No, it’s not, and here’s why.

We’re currently on track to warm the planet by 8° Fahrenheit by 2100. That amount of warming will likely lock us into a rise in sea level over subsequent centuries of at least 4 to 6 meters, at rates up to 1 meter per century.

That’s because under this much warmth, parts of Greenland and Antarctica – the great polar ice sheets – will slowly melt and waste away like a block of ice on the sidewalk in the summertime. Eventually.

Consider it our commitment to higher sea levels in the year 2100.

In total, 180 coastal municipalities in the conterminous U.S.A. with populations over 50,000 have an average of 36% of their land area at or below 6 meters of elevation and connected to the sea. Twenty of those have populations greater than 300,000.

How rising seas impact coastal municipalities through erosion, temporary flooding, and permanent inundation will very much depend on which city or town you are in. On top of that, some municipalities will have a lot of area potentially impacted by higher sea levels whereas others will have relatively little. So, what they do to face rising seas in New York may not be the same as what they do in Miami or Los Angeles.

The national and international dimensions of and efforts to curb human-caused climate change are in stark contrast to the very local, and disproportionate, potential impacts of higher sea levels.

One of our most popular landscapes to live and recreate in – the coast – is looking squarely at major changes from rising seas by the end of this century and beyond. Eventually, we will find out if our castles are made of sand.


Update

Due to readerhip interest, here are the visual impacts of modeled sea level rise in other areas of the United States:

1.  Northeastern United States SLR Amounts (1 to 6 meters)

2.  Select US Urban areas

NOTE:  A follow-up post visualy detailing SLR impacts on other urban centers throughout the world is forthcoming.

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Comments

Comments 1 to 30:

  1. I think Jeremy Weiss underestimates SLR along the Atlantic and Gulf coasts this century by a factor of 2+ and that the situation confronting US coastal states is a lot more threatening than he thinks.

    After an admittedly crude analysis of the causes of SLR,, I concluded in a blog written last year (http://www.onlineopinion.com.au/view.asp?article=11179)
    that it could be expected to accelerate throughout this century, could probably rise by 0.9m. by 2050, by >2.5m. by 2100 and thereafter by about 2.8m per century.

    This assumes average global temperature rises by 5C by 2100 with larger polar amplification resulting in speedier melting of ice-sheet fringes and more rapid discharge from glaciers causing major embayments.

    Hansen (2011) predicts, (I suspect correctly) that by 2100 temperature is likely to have risen by as much as 6C. Were that to be realized, then all bets are off on SLR, other than it will be higher and faster.

    An estimate of 1m rise by 2100 seems very optimistic. There is no reason for confidence that major emitters of CO2 will curb their total emissions until there is irrefutable evidence of the harm caused by them. By then it will be too late. As an interim measure governments would be wise to plan on much higher SLR and an increased likelihood of them being accompanied by storm surges.
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  2. This article does seem to only consider the scenario of the Greenland and Antarctic ice sheets melting in place - it doesn't mention the possibility of rapid break-up of parts of those ice sheets, with rapid sea level rise (SLR) as a result.

    Is this just scientific reticence at work again? I think it probably is - while there are some papers that predict much higher SLR by 2100, they're still, as yet, in the minority.

    Unfortunately, as Agnostic points out, Hansen (who is predicting SLR of up to 5m by 2100) has a bad habit of calling it correctly.

    One thing seems clear, though - the sort of SLR that is discussed in this article is probably going to be the minimum we'll have to deal with this century...
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  3. Gentlemen:

    If you take a closer read of the post, you'll see that predicting the amount of SLR is not the intent of the research the post delineates. Instead, Weiss et al take published consensus estimates of expected SLR by 2100 (which admittedly do not reflect the non-linearities in ice sheet losses discussed in Hansen 2011) and factor those values into a high-rez dataset (electronic vector map) to visually demonstrate that SLR impact in the areas modeled.

    The idea is that, in order to most properly reflect the impact of future SLR, a picture is of greater value as a teaching tool than a table of numbers.

    What Weiss et al do not do is to predict by how much SLR will be, or when said SLR values will arrive. But note that the map in the post above shows 6 meter inundation areas that would be fully compliant with the potentialities discussed in Hansen 2011.

    An extremely valuable study in that context.

    Hope that helps,

    The Yooper
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  4. Very true, Daniel, didn't mean to imply that I thought that was the case. I think impact studies such as this are vitally important. I guess I should have just stuck to my final point: that science is increasingly saying these are likely to be the minimum impacts we see this century.
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  5. @ Bern (4)

    Spot-on. We should be so lucky as to only experience 1 meter of SLR by 2100.

    Takeaway
    Seize every chance possible over the next few years to unload low-lying real estate near the sea. Once more robust data comes in to clarify the true scope of SLR with a more defined timeframe the market for affected properties will collapse.

    The Yooper
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  6. Daniel @ 5: I guess that's another one of those tipping points - although in this case, it will be a socio-economic one, when society at large starts to fully appreciate the implications of climate change.
    A quick google search reveals a news article claiming Australia stands to lose at least $150 billion worth of real estate value as a result of 0.9m of rise (number supposedly sourced from the insurance industry - and they note it's not covered by insurance!). That'd pay for the replacement of a whole lotta coal-fired power stations...
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    Moderator Response: [DB] Check out the maps of Australia I include on the next post on this subject (see next comment response for teaser info).
  7. Daniel @ 3

    Thank you for reminding us that Dr Weiss study is on imp[act.

    Odd then that the impact on the New England States, particularly the New York/Jersey City conurbation, is not shown. In my article I showed that a 2.5m SLR would have the most dire effects, crippling NY and causing such dislocation as to make much of the city non-functionable and unliveable.

    Then there are the effects on cities such as Boston, Baltimore, DC. At 2.5m SLR they do not bear thinking about and if Hansen is right (he usually is), socio-economic destruction is inevitable. Further, there is no defence against SLR. No map, no discussion. Pity.
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    Moderator Response: [DB] See the update section in the post at top. I'll have another post coming out in about a day similarly addressing other parts of the world. It will also include larger-scale renditions of sea level rise impacts on the cities you mention.

    Edit: Post available here.

  8. Hi all,

    This is something of a repost. Sorry if the previous one contravened the guidelines.

    Looking at the graphs on Hansen 2011, linked by Daniel@4, page 6, it seems that there is a clear relationship between temperature, levels of greenhouse gases and sea level in the geological record.

    The fact that sea level rises with ocean temperature may well have been an important mechanism of the self-regulation of the biosphere's temperature.

    A rise in sea level applies a greater amount of pressure on the submerged deposits of methane clathrates and other methane hydrates dissolved within the water column.

    If the current warming proceeds too rapidly, the temperature may increase far more quickly than the corresponding increase in pressure, which will perhaps lead to a dangerous erosion of the clathrate stability zone.

    So, and I do not claim this is an expert view, merely a subject for discussion, it may just be that the rise in sea levels is currently dangerously slow. Dangerous because it could lead to a potentially catastrophic release of methane - CH4.
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  9. Daniel Bailey in #5: "Seize every chance possible over the next few years to unload low-lying real estate near the sea."

    I've often found myself wishing I could think of a way to 'invest' in the continuation of global warming... and encourage 'skeptics' to invest in its supposed non-existence.

    With those who deny the possibility of fossil fuel depletion you can invest in the alternative energy sources which must eventually replace them... though picking which alternatives will do so is still a gamble.

    For GW I suppose one could buy real estate along the 'future coastline', but again that would be a gamble in determining exactly where that will end up.

    Anyway, the underlying point is that I think we've arrived at a world where denial of reality is status quo for large sections of the population. One way of changing that would be if clinging to such irrational beliefs hurt them financially in a directly visible way. Currently the 'scam artists' get away with it because they can always divert blame elsewhere or change their stories as the situation changes. Make falling for these scams a direct hit on the pocketbook and they could no longer continue ad infinitum as they do now.
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  10. Idunno,
    I have seen several posters recently suggest sea level rise would stabilize the gas clathrates. The addition of 2 or 3 meters of water would only add a small amount of pressure. The temperature change is much more important in their stability. We are currently changing the temperature in a big way.

    I am 52 years old. Even a house in the Florida Keys (very low land near Miami) would be unlikely to be inundated in my lifetime. Decision makers like Dick Cheney, who is older and in poor health, do not care if Miami is inundated in 40 or 50 years. My students were excited about Inconvienent Truth and sea level rise when it first came out. When they realized that the projected 20 foot sea level rise would not occur for 100-250 years many said "my grandchildren can deal with it".
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  11. Hi Michael,

    My understanding of the physics of dissolved gases and frozen chemicals such as methane clathrates at pressure is limited to say the least. I have done the PADI divemaster course, but that doesn't make me any kind of an expert.

    I do have a gut feeling that the temperature rise is already so great that the sea level rise would have to be in the range of 20 to 30 metres of water for the "clathrate stability zone" in the East Siberian shelf, and other locations, to be truly stable.

    This should perhaps be a worry to your students, to you and to Dick Cheney.

    As you are doubtless aware, the floating Arctic sea ice is disappearing. As this goes, the extra heat within the Arctic ocean will increasingly begin to melt the sea bed - which is composed of methane clathrates.

    Melt one litre of frozen water (aka ice) at surface and you get one litre of liquid water.

    Melt one litre of frozen water (aka methane clathrate) at the sea bed and you get only 0.8litre of liquid water. You also get 168 litres of methane.

    For "litre" replace "cubic kilometre" and you're dealing with the right units.

    If any of your students might be able to persuade me that I shouldn't be scared witless by this, I would really like to hear from them.

    Methane-lake level rise may precede sea level rise. Additionally, methane in sufficient concentrations is both poisonous and explosive.
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  12. I would like to add a warning on the utilization of those map. Sea rise is not uniform around the globe. In many place isostatic rebound is of the same order of magnitude as the sea rise rate. This means that some place will not see any increase, some will see decrease and some will see much larger increase.

    For example, New Orleans is expected to drop by 5 m before then end of century. In addition, if atmospheric or oceanic circulation is somewhat modified, rapid change in see level can be expected. Recently, there was also a suggestion that modification in weight distribution of ice could also leads to large scale sea level modification.
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    Moderator Response:

    [DB] That just guarantees that this will happen, then (red is 1 meter SLR, tan is the next 5):

  13. Time to by future beach from properties en Bâton Rouge.
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  14. Unfortunately, the idea of buying future coastline property doesn't work. Once the melt accelerates enough to cause the current coastline to indefensible, sea level rise is likely to be a multi-century process, with a "new" coastline every decade or so.
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  15. Any new coastline also likely won't have sandy beaches for a long time... unless we haul in the sand or the inland area was sandy to begin with. Beach decay has been a growing issue for many years now, but it is nothing compared to what will happen in the upcoming decades.

    Here's a thought for GW investing... look for high elevation points near the coast and buy those up. Eventually ugly rocky hill by the beach becomes your own private island. :]

    Just make sure the elevation is high enough that it'll remain above water for a long time.
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  16. Creation of people = growing almost exponentially.

    Creation of new real estate (at all, let alone that above future SLR) = slim to none (outside of new volcanic islands).

    Instead of the mantra "Go West, young man" the new mantra shall be "Buy High (ground), young man".

    Savvy investors, take note.

    The Yooper
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  17. Sea level has been rising steadily at 2mm/year historically. Has there been a verifiable increase in that rate recently?
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    Moderator Response: [DB] This thread is about the impacts of SLR. For an answer to your question, please see the sea-level-rise-predictions thread where that is discussed. Pertinent for thought is comment number 6. Thanks!
  18. #12 Yvan Dutil at 01:34 AM on 18 March, 2011
    "In many place isostatic rebound is of the same order of magnitude as the sea rise rate. This means that some place will not see any increase, some will see decrease and some will see much larger increase."

    So what is the pupose of the paper.

    Without taking into account the local isostatic rebound it is not of much value for local planning.

    So that leaves the goal of the paper as educational/motivational?
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  19. #16 Daniel Bailey "Creation of new real estate (at all, let alone that above future SLR) = slim to none (outside of new volcanic islands)."

    That statement contradicts both historical record for both coral atolls and large cities. It also contradicts the historical record for places like Bangladesh.

    Look at the outlines of past shoreline maps of San Francisco, Boston, New York or virtually any other city and you will see that even though the global sea level has been rising for the last 100+ years, that the vast majority of cities have expanded in size area, with large portions of sea becoming land. Whether delta areas (such as Bangladesh) are increasing or decreasing in area depends upon the balance of land subsidence vs. land generation from the deposition of silt carried to the delta by rivers.
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  20. Charlie A - "That statement contradicts both historical record for both coral atolls"

    Errr, no. The ocean is littered with drowned coral atolls.
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  21. Yvan : does it mean that New Orleans is expected to drop by 5-1 = 4 meters whatever we do against GW and SLR ?
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  22. #20 Rob Painting "The ocean is littered with drowned coral atolls".

    A simple observation about the longevity of coral atolls is their existence as islands, long after the volcanoes upon which they started have submerged.

    Are you unfamiliar with the depth of coral/limestone at the typical atoll?

    The coral atolls that have not managed to remain at sea level are generally cases such as the far northwestern Hawaiian Islands (aka Emperor Seamounts), where geological processes such as tectonic plate drift have, over 10's of millions of years, moved the the most northwesterly atolls into colder water, past the Darwin Point, where the reef can no longer keep up with erosion (and sea level changes). Kure Reef, the worlds most northly atoll at 28.5N is approaching that point.
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  23. Tuvulu is often mentioned as being in danger of drowning in the rising seas.

    What do the actual observations about Tuvulu tell us?

    Pacific islands 'growing not shrinking' due to climate change

    Far from drowning, some Pacific islands have grown as sea rises, study says
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  24. Charlie A:
    "The highest elevation is 4.5 metres (15 ft) above sea level" (from wikipedia).

    Given that we're talking about a likely minimum sea level rise of ~1m by the end of the century (some estimates are 5m+), I don't think we can be complacent about the fate of low-lying islands.

    With ultimate sea level rise likely to be at least 6 metres (but it may be as high as 25m, if the East Antarctic Ice Sheet stays frozen, 75m+ if it thaws), then there will be a lot more places than Tuvalu having trouble keeping their heads above water.

    The other thing to consider is that sea level rise is expected to accelerate - particularly due to ice sheet dynamics - so you aint seen nothin' yet, so to speak.

    It's a bit like me saying on midsummer's day that it's going to be cold here in 6 months, and you coming back three days later saying "hey, it's not any colder than it was the other day, what were you talking about?"
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  25. My posting to this thread was prompted by a comment by Daniel Bailey saying "Creation of new real estate (at all, let alone that above future SLR) = slim to none (outside of new volcanic islands)."

    If I have in error mistaken a Skeptical Science author with an uninformed poster, my apologies, but I assume that Daniel Bailey the author of the above comment is also the author of the recent Skeptical Science post Sea level rise: coming to a place near you.

    Hoping to assist in the understanding and knowledge of Skeptical Scientist's experts, I mentioned cases where his statement was inaccurate --- the very relevant to this article case of the expansion of shoreline areas in virtually every modern city; and the case of coral atolls.

    The peer reviewed paper on recent increase in land area of Tuvulu can be found at Webb & Kench 2010:
    The dynamic response of reef islands to sea-level rise: Evidence from multi-decadal
    analysis of island change in the Central Pacific


    Many islands had data only for 1984 to 2003. Others for 60 years, but the overwhelming majority had added land area, with the overall increase of all islands studied being 7% of the total area.

    The volcanic substrate is many hundreds or thousands of meters below the surface and this "creation of new real estate" is definitely NOT volcanic in origin.

    ======================================

    Bern, it is more like you, in the middle of summer, forecasting a horrible freeze and snow in 6 months time. I agree, pointing back to the horrible freeze and snow that we had survived 6 months prior.

    There is a rate of rise for which coral atolls can adapt. The current rate of rise is well within that rate. Three times that rate, 10mm/yr or 1 meter per century is approaching that limit in some areas. In other areas the limit is as much as 10cm per YEAR.
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  26. CharlieA - Are you unfamiliar with the depth of coral/limestone at the typical atoll?

    Yes, and no doubt so will you, seeing as many of them have not been drilled to the underlying basalt base. The ones that have can indeed be many hundred of meters thick, only the top 10-15 meters being the result of Holocene growth.

    The coral atolls that have not managed to remain at sea level are generally cases such as the far northwestern Hawaiian Islands

    Yes, as they migrated into cooler waters. But many reefs "drowned" during the Cretaceous period when they bleached as the atolls were transported into hot tropical waters. And the point you should be taking away from this is that ocean acidification and coral bleaching are going to seriously diminish the ability of coral reefs to keep pace with sea level rise.
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  27. The peer reviewed paper on recent increase in land area of Tuvulu can be found at Webb & Kench 2010

    Yes, familiar with the paper. I have no reason to doubt the results of their survey. Seems reasonable to me, we have only seen small rises in sea level thus far. A 2mm average rise in that Pacific region over the last 60 years (although this is higher in recent times) is not enough to inundate the solid reef foundations which formed during a regional sea level highstand there 4-2000 years ago. That's expected to happen mid to late 21st century. Once local high tide overtops the reef flats, the coral rubble and sediments will be subject to wave attack and erosion. See Dickinson 2009.

    There is a rate of rise for which coral atolls can adapt.

    Which is variable depending on the ambient conditions. Even before the advent of the industrial revolution many coral reefs drowned when we would have expected them to cope with sea level rise going on at the time. There is, for example, a vast relict reef off the Great Barrier Reef complex. Why did it drown during the Holocene?. We don't yet know. And of course, many reefs back-stepped during the Holocene too.

    Given all the harm humans are inflicting upon coral reefs, it's unreasonable to expect them to grow to match sea level rise, especially as studies trickle in showing that reef growth is declining around the world.
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  28. #27 Rob Painting. I agree with the above post. It makes the basic point I was trying to make, that there is indeed creation of new real estate going on in many areas.

    This sequence of several back and forth comments all go back to comment #16 by Skeptical Scientist author Dan Baily, where he stated that "Creation of new real estate (at all, let alone that above future SLR) = slim to none (outside of new volcanic islands)." and my response in #19 that said his statement was contrary to the historical record for coral atolls, the historical growth in seashore land area in urban areas, and the historical growth of some deltas.

    I didn't think that was a particularly controversial statement, although it drew an immediate contrary response from you.

    Unless you want to challenge that portion of my assertion that is most relevant to this article ... which is that almost all urban areas have added real estate over the last 100 or 200 years, even as the sea level continued to rise; then this exchange has reached its end.
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  29. CharlieA - "It makes the basic point I was trying to make, that there is indeed creation of new real estate going on in many areas"

    OK. Point taken.
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  30. Apologies for being away: Had to deal with this crazy thing called life, the universe & everything.

    Charlie A, I'm sorry if you have taken exception to my phraseology. I apologize for a lack of clarity in my thoughts. While indeed in the historical, paleo, record coral atolls have managed (with mixed success) to survive periods of sea level variability, for the majority of those periods the rates of change will be exceeded by those to come.

    For your observation about land reclaimed from the sea or created out of whole cloth: point taken. I would submit that the areas reclaimed have been quite small in comparison to the existing land surface, however. And that rates of people creation have vastly exceeded those of land area creation.

    I would also point out that reclamation of areas/land creation is an expensive proposition in an era of stable sea levels; given 1-5+ meters SLR projected to possibly occur over the next 100 years it would seem likely that efforts will shift to protecting as much as possible of what exists via sea walls and tide surge barriers. Given a 5 meter SLR and a 5 meter storm surge, how much can be protected before the cost of protection becomes economically unviable?

    Napoleon once faced such as onslaught...and fared non-too-well.

    The Yooper
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