Anthony commented yesterday on the question of atolls and sea level rise here, and I had previously written on the subject in my post “Floating Islands“. However, Anthony referenced a paper which was incorrectly linked by New Scientist. So I thought I’d provide some more information on the actual study, entitled “The dynamic response of reef islands to sea level rise: evidence from multi-decadal analysis of island change in the central pacific”, by Arthur Webb and Paul Kench.
One of the ironies of the new paper involves the atoll of Amatuku in the island nation of Tuvalu. Amatuku became the first poster child of “drowning atolls” due to an article in the July/August 2003 issue of Sierra Magazine, the magazine of the Sierra Club. The article was entitled “High Tide in Tuvalu”, with the sub-title “In the tropical Pacific, climate change threatens to create a real-life Atlantis.” Here’s a recent photo of “Atlantis”:
Figure 1. Photo taken in the South Pacific nation of Tuvalu (8°S, 179°E), showing Amatuku Atoll and the abandoned causeway. PHOTO SOURCE
In the Sierra Magazine article the author described the terrifying effects of “global warming” on Amatuku Atoll, site of the Tuvalu Maritime Training Institute:
To explain global warming in stark detail, all Tito Tapungao has to do is show a visitor around the grounds of his school. Dressed in his sailor’s pressed whites, the chief executive officer of the Tuvalu Maritime Training Institute points out a small brick cabin built by missionaries in 1903. Now, a century later, annual high tides rise halfway up the bedposts.
YIKES! Be very afraid. So what is the irony in the new study?
Well, I’ll get to that. But first, a bit of history. The Sierra Magazine article was what impelled me to write my 2004 paper (Word Doc) on Tuvalu. I read that article, and my urban legend detector started ringing like crazy. Consider: the missionaries’ cabin was likely built a metre or so above high tide. Add another half metre for the floor, and a half metre to get “halfway up the bedposts” … no way, I thought, that the sea level has risen two metres in Tuvalu.
Upon further investigation, I found out that the answer was already known, because geologists had studied (pdf) the area. They found the changes in the shape of Amatuku Atoll were a result of changing currents from major alterations made in the reef during World War Two. A channel was cut from the lagoon to Amatuku, and a causeway was constructed between Amatuku and nearby Malitefale Atoll. Fill to make the causeway came from “borrow pits”, holes dug in the reef flats to provide coral rubble for the construction. And some decades after the war, further borrow pits were dug to provide building materials for the Maritime Institute. The swimmers in the Fig. 1 are swimming in one of the old borrow pits. Here’s an aerial view of the changes:
Figure 2. Amatuku and Malitefale Atolls, Tuvalu, South Pacific. Amatuku is less than a kilometre long.
As you can see, the changes in the reef structure were quite extensive. All of these alterations in the reef changed the currents around the two atolls. And of course, as a result, the shape of the atolls changed. This change in shape is to be expected – after all, atolls are just piles of sand and rubble in the middle of a wild ocean. One of the results was the erosion (not from CO2, not from warming, not from sea level rise, but erosion from man-made changes in the reef) of the corner of the atoll where the missionaries’ cabin was located.
Over the years since I published my paper, I’ve taken a lot of heat for my claims. I’ve gotten plenty of irate emails from folks in Tuvalu and around the world, emails castigating me for suggesting that the rising sea levels won’t drown the atolls, emails impugning my ancestry, emails saying we’d soon see thousands of “climate refugees” from Tuvalu, emails proposing that I perform anatomically implausible acts of sexual auto-congress, and mostly emails saying that I was clearly wrong, that it was patently obvious that rising sea levels would inevitably drown the atolls, duh, so there.
OK, enough history. I got a pre-publication copy of the current paper under discussion from one of my secret underground (underwater?) sources, my thanks to WS. The abstract of the paper says (emphasis mine):
Abstract
Low-lying atoll islands are widely perceived to erode in response to measured and future sea level rise. Using historical aerial photography and satellite images this study presents the first quantitative analysis of physical changes in 27 atoll islands in the central Pacific over a 19 to 61 year period. This period of analysis corresponds with instrumental records that show a rate of sea level rise of 2.0 mm.y-1 in the Pacific.
Results show that 86% of islands remained stable (43%) or increased in area (43%) over the timeframe of analysis. Largest decadal rates of increase in island area range between 0.1 to 5.6 hectares. Only 14% of study islands exhibited a net reduction in island area. Despite small net changes in area, islands exhibited larger gross changes. This was expressed as changes in the planform configuration and position of islands on reef platforms. Modes of island change included: ocean shoreline displacement toward the lagoon; lagoon shoreline progradation; and, extension of the ends of elongate islands. Collectively these adjustments represent net lagoonward migration of islands in 65% of cases.
Results contradict existing paradigms of island response and have significant implications for the consideration of island stability under ongoing sea level rise in the central Pacific. First, islands are geomorphologically persistent features on atoll reef platforms and can increase in island area despite sea level change. Second; islands are dynamic landforms that undergo a range of physical adjustments in responses to changing boundary conditions, of which sea level is just one factor. Third, erosion of island shorelines must be reconsidered in the context of physical adjustments of the entire island shoreline as erosion may be balanced by progradation on other sectors of shorelines. Results indicate that the style and magnitude of geomorphic change will vary between islands. Therefore, Island nations must place a high priority on resolving the precise styles and rates of change that will occur over the next century and reconsider the implications for adaption.
Ahhh, vindication is sweet. The authors agreed totally with what I had written in 2004. Rising sea levels don’t destroy atolls, and their shape is always changing. Exactly what I had taken so much heat for saying.
In addition to the Abstract, the Conclusions of the paper are quite interesting. Here are some extracts (emphasis mine):
Conclusions
The future persistence of low-lying reef islands has been the subject of considerable international concern and scientific debate. Current rates of sea level rise are widely believed to have destabilised islands promoting widespread erosion and threatening the existence of atoll nations. This study presents analysis of the physical change in 27 atoll islands located in the central Pacific Ocean over the past 20 to 60 years, a period over which instrumental records indicate an increase in sea level of the order of 2.0 mm y-1.
The results show that island area has remained largely stable or increased over the timeframe of analysis. Forty-three percent of islands increased in area by more than 3% with the largest increases of 30% on Betio (Tarawa atoll) and 28.3% on Funamanu (Funafuti atoll [the main atoll in Tuvalu – w.]). There is no evidence of large scale reduction in island area despite the upward trend in sea level. Consequently, islands have predominantly been persistent or expanded in area on atoll rims for the past 20 to 60 years.
… Results of this study contradict widespread perceptions that all reef islands are eroding in response to recent sea level rise. Importantly, the results suggest that reef islands are geomorphically resilient landforms that thus far have predominantly remained static or grown in area over the last 20 – 60 years. Given this positive trend, reef islands may not disappear from atoll rims and other coral reefs in the near-future as speculated. However, islands will undergo continued geomorphic change. Based on the evidence presented in this study it can be expected that the pace of geomorphic change may increase with future accelerated sea level rise. Results do not suggest that erosion will not occur. Indeed, as found in 15% of the islands in this study, erosion may occur on some islands. Rather, island erosion should be considered as one of a spectrum of geomorphic changes that have been highlighted in this study and which also include: lagoon shoreline progradation; island migration on reef platforms; island expansion and island extension. The specific mode and magnitude of geomorphic change is likely to vary between islands. Therefore, island nations must better understand the pace and diversity of island morphological change and consider the implications of island persistence and morphodynamics for future adaptation.
Couldn’t say it better myself … and oh, yeah, what about the irony?
Well, Amatuku, the poster child of disappearing atolls, the threatened “real-life Atlantis”, home of the disappearing missionaries’ cabin, happened to be one of the atolls considered in the study. The authors found that despite the loss of the missionaries’ cabin, Amatuku increased in area by about 5% over the nineteen year period during which it was studied … ah, the irony, it burns.
The satellite data seems to have Tuvalu in higher trend area over the last couple of decades
http://www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/
See the ’92-’09 trend map below the graph. Tuvalu seems to be in area of 8-10mm/yr, though my old eyes aren’t great at differentiating the subtle variations hooker lipstick red they always use on these presentations.
Personally, I’ve never been overly confident in these satellites’ ability to do what they claim. Here’s a bit from a comment I posted to the previous Tuvalu thread.
“For those still inclined to accept the plots of sea level rise that are bandied about I suggest spending some time reviewing this document
http://www.osdpd.noaa.gov/ml/ocean/J2_handbook_v1-3_no_rev.pdf
It’s the OSTM/Jason-2 Products Handbook and it contains the best info on how they measure and calculate SSH and MSL that I’ve come across. Actually they appear to be doing a lot better than I would have thought before I studied it, at least if you’re willing to accept all their claims. Even then, they’re talking about first cut accuracy of 11.2 cm with final product accuracy of 3.4 cm after long term averaging and numerous correction factors applied. These values of course exclude significant wave height, which is a chaotic factor they admit they don’t really have a good handle on and adds an uncertainty in the range of 0.9 to 0.5 meters, and these accuracies are specs which may or may not be met.
The magnitude and multitude of the corrections and calculations necessary to produce the end product data makes what they are doing a most impressive technical and engineering achievement, but even if they can meet all their design goals, the end result will be a very good map which still may well be only a fair representation of the real territory.
I would also note that these details are for the latest Jason-2 satellite, which is a step up from the Jason-1 unit, which was itself an even larger step up from the original Topex/Poseidon units.”
Of course, if we do accept the satellite data, a question comes to mind. If sea level rise is supposed to be driven by melting sea ice, why is the long term trend map dominated by a high trend area where melting ice wouldn’t seem to a possible contributor?
We need a similar study on flood plains such as the one Bangladesh is built on. This land is also in active and dynamic equilibrium with the ocean and will not simply sink as sea levels rise.
Another question I had when I first came across the long term sea level trend map I referenced above was, what phenomenon could possibly account for the patterns of globular high positive trend areas interspersed with or surrounded by areas highly negative trend? I’ve posted this a couple times, but no one has ever jumped in with a guess.
Sinking?… just the AGW argument
A good point has been made and made and made and made that should be expanded upon and additional factors reunderstood. Active coral growth exceeeds the rate of sea rise by a significant multiplier. In Maine we don’t have coral so I’ve decided it is possible to compensate for sea rise with my wheel barrow! 1 mm = 0.039370079. OR 5/127 3mm= 15/127 inch about 15 cubic yards per acre stays even to the highest estimate. A truck and a half. Everyone that has been on a Pacific atoll or even a Caribbean atoll, even a sand or rock beach is aware that the beach storm berm is higher than the mean sea level.
Depending on the storm wave size, WAY higher. On Suvarov the storm berm on the windward side of the motu was at least twelve feet higher than mean sea level and there were chunks of coral reef the size of small cars. Bermuda what you walk on is all coral…sand dunes. It is a long way down below sea level to volcanic rock. This response to sea level change or sinking islands was taught in high school geology classes. reference Principles of Geology ,Third edition , Guilluly, Waters and Woodford W.H. Freeman & Company, SanFrancisco, 1968, PP 358,360 Reference to Darwin’s trheory of subsidence, drilling on Eniwetok demonstrated over 4,000 feet of reef “sunk”. Glacial control Hypothesis of Dailey 1942. COME on! Lets rediscover the golden age of independant thinking and honest investigation.
I visit Galveston island several times a summer and have observed that barrier islands move. That should be obvious to anyone that visits one frequently.
Storms cut into the ocean side of the island and deposit the sand on the landward side. I have always said I would not invest in a beach house for that and other reasons. If you are close enough to the ocean to walk out your back door in a few years you will have to pick up your house and move it. No sea level change needed.
After the last storm many beach houses which weren’t destroyed by the storm were within X feet of the ocean and had to be moved or destroyed. You can’t have a house within X feet of the high tide line by law.
Where there are restaurants and commercial real estate they haul in huge boulders and lash them together with mesh to postpone the problem. Seawall boulevard has been there for a long time because the natives understand.
The Tuvaluans could learn from them.
My nomination for blogger’s quote of the week goes to Tom H.
Where the hell is Seth Borenstein??
Who’d of thunk, God is an engineer. Humble pie anyone!
Dave Wendt says:
June 3, 2010 at 7:45 pm
I cannot answer that, but I first got confused when I discovered that there are different mean sea levels all over. The reason is twofold I found out.
Most variable is the air pressure – it pushes down in the sea and moves water away to lower pressure areas.
The second is currents where tides are constrained. For example the high tide NW of Australia is particularly high I understand because there are a great many reefs blocking the water. That causes it to ‘back up’ behind the reefs.\
If and how those two, and presumably other, phenomena actually change trends I have no idea however, but it does tell me it is not immediately obvious.
Willis, just a question. Now that the mechanism for the island growth has been proven with observation, is it possible to re-shape atolls in such a way that facilitates maximum growth?
While most of us think of coral reefs with visual imagery one of my most striking and persistent memories of my first dive on a coral reef is auditory: the curious and pervasive crunch crunch crunch of parrot fish standing on their heads bobbing up and down munching on the coral with their buck teeth, an occasional plume of sand erupting from their digestive tracts. A marvel to behold. In those days (1973) the doom du jour for the great barrier reef was the Crown of Thorns Starfish which was undergoing a population boom. The climate meme of the day was the coming ice age.
To paraphrase from Blazing Saddles “The end is n*Bong, Bong*r. No dag blast it I said the end is n*Bong, Bong*r.”
Excellent detective work again Willis! I just keep being more impressed with your work every time I read your posts.
And it just keeps getting worse for all the AGW scary stories.
Maybe I missed it… but how exactly could anyone even measure sea level rise against these dynamic islands?
“And he said unto them, He that hath ears to hear, let him hear.”
Willis, it is screaming at you.
This also is a grievous evil– exactly as a man is born, so will he die. So what is the advantage to him who toils for the wind?
Furthermore, I have seen under the sun that in the place of justice there is wickedness and in the place of righteousness there is evil.
Willis I have a task for you or some other number cruncher (probably done before). Has any one calculated the displacement volume of sedimentation carried to the sea by the world’s great rivers? If we can get them to quit worrying about melting ice causing the seas to rise and worry about soil erosion instead maybe we can put the energy toward something beneficial. This of course overlooks wind borne sedimentation.
The myth presented by the AGW crowd is that coastlines should be in stasis. In fact, one of the basic tenants of modern environmentalism is that the world would be in stasis, a perfect balance between all systems, if it was not for humanity screwing up the natural order of things.
The reality is that, in the real world, stasis equals death! We can not have life without change! It is a prerequisite. Even non living systems like coastlines, continents, rivers and mountains are dynamic. The world is always changing and will continue to do so until it is cold and dead. Modern environmentalism, and all of its evil offspring (like AGW), is the antithesis of life. At its very core, the philosophy of modern environmentalism is fatally flawed and should be scrapped! It is the only rational thing to do.
I am not “…for change”. like Bill Clinton. It is just the way things are. Environmentalists have to stop trying to prevent it.
I guesss Nils Axel Morner really is the best scientist around for this type of information. He has been telling everyone the same thing for years!!
Dave Wendt says:
June 3, 2010 at 7:45 pm (Edit)
Just like water in a bucket if you shake it a bit, the water in any tidal basin “sloshes” around in the basin. In some basins at some time, this can lead to unusually high or low tides. This affects places like Funafuti, the capital of Tuvalu. The water inside the Tuvalu lagoon sloshes back and forth, and if it coincides with a high tide, the screams of “global warming” can be heard on the next atoll.
The same thing happens in the Pacific Ocean itself, where at any time some areas will be higher and some will be lower. The study of this variation across the surface of the oceans is fairly new, since we don’t have even one small tidal cycle (18.6 years) of satellite data. There is also a longer tidal cycle, which is fifty some years, can’t remember exactly. So while at present Tuvalu’s tidal level is higher than average, over time it will even out.
Ian H says:
June 3, 2010 at 7:33 pm
This has also been studied by several groups, who found that the area of Bangladesh is also increasing. Here’s the report of one study.
What Willis has suggested (June 3, 2010 at 10:08 pm) are what I tend to think of as very low-frequency standing waves, or seiches. My feeling, however, is that these can’t be the cause, even with very long periods, because they aren’t static features. Here are a few other WAG’s that might apply:
(1) underwater hot spots creating lower density water,
(2) high gravity regions under the ocean floor,
(3) vertical motion due to thermohaline circulation.
Not sure if any of them apply, though.
/dr.bill
Willis Eschenbach says:
June 3, 2010 at 10:08 pm
Dave Wendt says:
June 3, 2010 at 7:45 pm (Edit)
Another question I had when I first came across the long term sea level trend map I referenced above was, what phenomenon could possibly account for the patterns of globular high positive trend areas interspersed with or surrounded by areas highly negative trend? I’ve posted this a couple times, but no one has ever jumped in with a guess.
Just like water in a bucket if you shake it a bit, the water in any tidal basin “sloshes” around in the basin. In some basins at some time, this can lead to unusually high or low tides. This affects places like Funafuti, the capital of Tuvalu. The water inside the Tuvalu lagoon sloshes back and forth, and if it coincides with a high tide, the screams of “global warming” can be heard on the next atoll.
The same thing happens in the Pacific Ocean itself, where at any time some areas will be higher and some will be lower. The study of this variation across the surface of the oceans is fairly new, since we don’t have even one small tidal cycle (18.6 years) of satellite data. There is also a longer tidal cycle, which is fifty some years, can’t remember exactly. So while at present Tuvalu’s tidal level is higher than average, over time it will even out.”
Supposedly tidal variations and other systemic and random variations are corrected out in generating the sea surface anomaly and the map I referenced is of cumulative trends over nearly two decades. The globular patterns I asked about would seem to suggest that, even after removing natural variabilities, differences of SSH of about a foot and a half over relatively short distances have persisted for years. The only thing I can think of that could generate the pattern of variance shown on the map would be a similarly convoluted pattern of gravity anomalies, but that doesn’t seem even remotely reasonable to me. I have no real theory about this, only a question which has intrigued me for a while.
As I indicated in my previous comment I am not at all convinced that these satellite projections are actually reflective of the reality of the ocean’s surfaces, but if they are, the fact that these atolls have still demonstrated the ability to expand in area in the face of an above average trend of increase would suggest to me that the coral’s capacity to generate new material may be even more robust than we suppose.
JER0ME says:
June 3, 2010 at 9:33 pm
I cannot answer that, but I first got confused when I discovered that there are different mean sea levels all over. The reason is twofold I found out.
Most variable is the air pressure – it pushes down in the sea and moves water away to lower pressure areas.
The second is currents where tides are constrained. For example the high tide NW of Australia is particularly high I understand because there are a great many reefs blocking the water. That causes it to ‘back up’ behind the reefs.\
If and how those two, and presumably other, phenomena actually change trends I have no idea however, but it does tell me it is not immediately obvious.
Actually the absolute height of the ocean surface varies over 200 meters. The “geoid”, an idealized representation of the oceans varies +/- 120 meters based mostly on gravitational variability. Changes due to tides, winds, waves, storm surges,air pressure, etc. only amplify that range, meaning that at any given moment the absolute difference may approach 300 meters, maybe more.
Good post Willis, I am genuinely concerned about the abuse that you have suffered over the years, still you are not alone, many great men have suffered.
If he were alive today Galileo would surely attest to that.
I studied geology so I always thought the ‘sinking’ island scary tale was a bit (a lot) far fetched.
This abuse though……….I thought the alarmists now claimed that it is the realists who are the nasty ones……..and all the time it was the alarmists lying about how ‘nice’ they are……deary, deary me.
Keep on sticking it to ’em Willis.
From some of the replies I’ve gotten, I’m not sure I’ve been entirely clear what I’m asking about. The map in question is on this page from AVISO below the graph of MSL
http://www.aviso.oceanobs.com/en/news/ocean-indicators/mean-sea-level/
The phenomenon I’m enquiring about occurs in bands at lat 30-50 in both northern and southern hemispheres, the largest running from the Horn of Africa to south of Australia. In the North it’s evident east of Japan and in the north Atlantic. It may be an artifact of some flaw in the satellite system, which would probably be my Occam’s razor choice if pushed.
The underwater government meeting stunt that proved to be so popular worldwide should be made into a regular tourist attraction. That’s the only honest use for it.