Guest post by David Middleton
Featured image borrowed from USGS.
As promised, here is the sequel to “Five Pacific islands vanish from sight as sea levels rise.” The thoroughly ridiculous New Scientist article is based on this paper:
Simon Albert, Javier X Leon, Alistair R Grinham, John A Church, Badin R Gibbes and Colin D Woodroffe. Interactions between sea-level rise and wave exposure on reef island dynamics in the Solomon Islands. , ,
Apart from some obligatory babbling about IPCC sea level rise projections, the paper is actually very good.
At least eleven islands across the northern Solomon Islands have either totally disappeared over recent decades or are currently experiencing severe erosion. However, islands in the more sheltered Roviana area of the southern Solomon Islands did not experience significant coastal recession.
[…]
To date, the responses of the islands of Melanesia to sea-level rise have been poorly studied, a recent review of island change studies in the Pacific indicated ‘little evidence of heightened erosion or reduction in island size‘ (McLean and Kench 2015). These islands were located across the Central Pacific in areas with 1–5 mm yr−1 sea-level rise where net accretion occurred on most islands and only small (<1 ha) islands were actively eroding (McLean and Kench 2015).
[…]
Relative sea-level rise can also be the result of tectonics, the Solomon Islands are in a particularly tectonically active part of the globe with the convergence of the Pacific Plate, Solomon Arc block and Australian Plate causing localised crustal deformations (Tregoning et al 1998) manifesting as either island subsidence or uplift (Taylor et al 2008). Whilst the Isabel study site is considered to be in a more tectonically benign area, without active volcanoes, the Roviana site experienced an 8.1 megathrust earthquake in 2007 which led to the reef islands of Roviana subsiding by up to 60 cm (Taylor et al 2008). Island subsidence can compound sea-level rise rates and make these tectonically active islands particularly vulnerable under accelerated sea-level rise scenarios. However, the apparent resilience of islands in Roviana to subsidence, despite observed increases in coral cover on adjacent reefs attributed to deeper water (Saunders et al 2015), and only 1 (±1.4) mm yr−1 of vertical tectonic uplift measured in Honiara since 2008 (Jia et al 2015), suggests subsidence is not the primary driver of coastal erosion observed in this study.
The rapidly eroding islands identified in Choiseul and Isabel are all exposed to northerly swell and wind events that at times can be severe (Smithers and Hoeke 2014), with twenty-fold higher wave energy at Isabel compared to Roviana (figure 5). The largest net erosion since 1947 occurred on Sogomou, Hetaheta and Kale Islands on Isabel, causing erosive displacement in a south-south-westerly direction.
Albert et al., 2016 clearly demonstrate that this quote from the New Scientist article is a lie:
Going, going, gone. Five of the Solomon Islands have been swallowed whole by rising sea levels, offering a glimpse into the future of other low-lying nations.
The islands, to the extent that they were islands were exposed to intense erosional forces for decades, if not centuries. They eroded away. Sedimentary geology depends on lots of things eroding away. Without erosion, there wouldn’t be much in the way of clastic deposition (like sandstone).
If “five of the Solomon Islands [had] been swallowed whole by rising sea levels, it would be impossible for “islands in the more sheltered Roviana area of the southern Solomon Islands” to “not experience significant coastal recession.” Secular sea level rise doesn’t care about shelter, waves and storms do. However, Albert et al., 2016 assert that sea level in the Solomon Islands is rising at 7 mm/yr and that this is likely to accelerate. Dr. Albert Parker has previously demonstrated that the 7 mm/yr claim is “cherry picking,” based on tide gauge records from Honiara, Guadalcanal.
The 7 mm/yr claim is based on the time 1994-2014 time frame. This rate is more or less corroborated by the satellite data (1993-2016). The tide gauge data date back to 1974. Since the sunken Solomon Islands began sinking in 1947 (or earlier) and a fair bit of the sinking took place between 1947 and 1960, I decided to look for a sea level reconstruction for that period. I searched NOAA’s paleoclimate database While I didn’t find a reconstruction for the Solomon Islands, I did find one from the west coast of Australia (Zinke et al., 2014).
While Fremantle is a long way from Guadalcanal and technically in a different ocean, the patterns of sea level change since 1993 are very similar.
The Fremantle reconstruction exhibits no secular trend from 1795 to 2009…
If we overlay the data from Table 1 in Albert et al., 2016 onto the Zinke et al., 2014 sea level reconstruction, we can see that the sunken islands of Guadalcanal were sinking without the assistance of a secular rise in sea level…
The instrumental data may exhibit a higher dynamic range of amplitude than the reconstructed data; however sea level hasn’t been doing anything differently over the past 20 years than it was doing over the prior 200 years…
Proxy data always have lower resolution than instrumental data. The Earth is a big low-pass filter and whenever you apply a low-pass filter, you attenuate amplitude. Disregard of this very basic bit of signal processing theory is the foundation of most hockey sticks.
References
Albert,S., J. X. Leon, A. R. Grinham, J. A. Church, B. R. Gibbes and C. D. Woodroffe (2016), Interactions between sea-level rise and wave exposure on reef island dynamics in the Solomon Islands, Environmental Research Letters 11:054011.
Holgate, Simon J. , Andrew Matthews, Philip L. Woodworth, Lesley J. Rickards, Mark E. Tamisiea, Elizabeth Bradshaw, Peter R. Foden, Kathleen M. Gordon, Svetlana Jevrejeva, and Jeff Pugh (2013) New Data Systems and Products at the Permanent Service for Mean Sea Level. Journal of Coastal Research: Volume 29, Issue 3: pp. 493 – 504. doi:10.2112/JCOASTRES-D-12-00175.1. Permanent Service for Mean Sea Level (PSMSL), 2016, “Tide Gauge Data”, Retrieved 09 May 2016 from http://www.psmsl.org/data/obtaining/. Via NOAA
Nerem, R. S., D. Chambers, C. Choe, and G. T. Mitchum. “Estimating Mean Sea Level Change from the TOPEX and Jason Altimeter Missions.” Marine Geodesy 33, no. 1 supp 1 (2010): 435.
Zinke, J., A. Rountrey, M. Feng, S.P. Xie, D. Dissard, K. Rankenburg, J. Lough, and M.T. McCulloch. 2014. Corals record long-term Leeuwin Current variability including Ningaloo Niño/Niña since 1795. Nature Communications, 5, 3607. doi: 10.1038/ncomms4607
I though they pegged most of it to erosion already…..
http://cdn.iopscience.com/images/1748-9326/11/5/054011/Full/erlaa21eff7_lr.jpg
Published 6 May 2016
Interactions between sea-level rise and wave exposure on reef island dynamics in the Solomon Islands
Low-lying reef islands in the Solomon Islands provide a valuable window into the future impacts of global sea-level rise. Sea-level rise has been predicted to cause widespread erosion and inundation of low-lying atolls in the central Pacific. However, the limited research on reef islands in the western Pacific indicates the majority of shoreline changes and inundation to date result from extreme events, seawalls and inappropriate development rather than sea-level rise alone………
http://iopscience.iop.org/article/10.1088/1748-9326/11/5/054011
They did. That’s why I posted this…
Interesting but extremely unrelated picture at the Lead In to the post. Not sure what that particular image has to do with the Solomon Islands. It is from the USGS page and shows the erosion caused to Hackberry Beach in response to Hurricane Rita. Of course during the time between the upper image (June 2001) and the lower image (Sept 2005) the area had seen numerous tropical storms
2001 TS Allison
2002 TS Bertha
2002 TS Fay
2002 TS Hanna
2002 H Isadore
2002 H Lili
2003 TS Bill
2004 H Ivan (A cat 5 that subsided to a TS by the time it struch Lousiana)
2004 TS Matthew
2005 H Cindy
2005 H Katrina (2 weeks before and a source of major flooding)
2005 H Rita
Of course with an area seeing 11 storms and 2 major hurricanes in 5 years some erosion will have occurred.
@Bryan A,
The Featured Image has nothing to to with the Solomon Island. It is a before and after photo of storm-driven coastal erosion.
Was one of these islands the one which collapsed into the water at the end of the Son of Kong movie? (Probably not as that island sank in 1933, before CAGW was a problem.)
A large number of climate alarmist claims remind me of the old Saturday Night Live Emily Littella routine “Never mind”.
The eroded small islands were to the north of the big islands. That exposes them to wave action from the many typhoons generally tracking east to west north of the Solomons. Same kind of long fetch big swells that cause surf to get up in Hawaii.
i would swear that China took all that material and made new islands in the South China Sea.
After bringing up a lot of these point on the comment section of the cNET article, I got the author to change the story. It now claims that CAGW caused more wind and waves. The goal posts shifted to keep us (evil westerners) on the hook for these islands disappearing.
Fortunately they reappeared when the tide went back out.
I’m so old.
How old are you, Baz?
I’m old enough to remember when New Scientist was a respected journal.
We REALLY ought to start referring to this rag as ‘No Scientist’ (with thanks to a contributor here a few days ago). It might catch on.
No Scientist and Notional Geographic.
I call it Gnat Geo. Thought some years ago of having a website of that name, for the posting of all the nonsense in Nat Geo.
I’m pretty old but I don’t remember New Scientist as anything but a popular science mag like Discover. I remember when Scientific American was respectable and damn tough reading for a layman and I would think even for a scientist reading articles outside their field of study. I would read articles several times, looking up terms and doing research just to understand what they were talking about. No internet in those days either! First I gave up on Discover about 30 yrs. ago. It seemed to start leaning ever more toward entertaining. Then I gave up on Scientific American probably 10 or so years ago. Neither Scientific nor very interesting anymore. Finally quit New Scientist a couple years ago when the pop science stuff wasn’t enough to make up for them endlessly flogging AGW. In fact, New Scientist made me a skeptic! They went so far out on so many limbs favouring AGW that they made it obvious there was something wrong with the theory.
Me too, gave up on all three popular “science” magazines around those dates.
Now use Google Scholar. Now almost half of papers can be accessed in full, by clicking on “All n versions”. Sometimes you get the author’s pre-publication version, and sometimes a copy in one of the repositories, such as Researchgate.
To get up to date quickly in an unfamiliar field, I look for a review paper.
Enter the following in Google Scholar and right click on ‘All 12 versions’ to get a review paper:
“Pallé SUNSHINE, CLOUDS AND COSMIC RAYS”
The following produced 18 full-text versions of anothe Pallé paper: “Changes in Earth’s reflectance over the past two decades”
On page 1300, we find something never found in popular magazines
“The decrease in Earth’s reflectance from 1984 to 2000 suggested by ISCCP data in Fig. 3 corresponds to a change in … of some –0.02, which translates into a decrease of the Bond albedo by 0.02 …and an additional SW absorption, R, of 6.8 W/m2 … C/4, where C … 1368 W/m2 is the solar constant). This is climatologically very significant. For example, the latest IPCC report (10) argues for a 2.4 W/m2 increase in CO 2 longwave forcing since 1850. Our observational ES data extend from 1999 to 2003 and indicate a clear reversal of the ISCCP-derived reflectance trend starting in 1999 up through 2003. The increasing trend in reflectance corresponds to approximately 5 W/m2, bringing the mean reflectance anomaly back to its 1980s values.”
Note: Some text replaced by “…” did not copy. Please refer to PDF.
When warmists dismiss the effect of GCRs on cloud formation and albedo, they may be referring to Pallé’s earlier work which did not find any association.
The moral is this: It’s a lot of work to be an informed skeptic.
The alternative is to follow the propaganda on either side or to remain confused by both sides.
Attributed to Edward Teller: “Scientific American is neither scientific nor American.”
I jumped ship from Scientific American in the early ’80s, when they were publishing absurd articles criticizing the Strategic Defense Initiative, in which I was working at the time. I knew the articles were bunk, but company policy and classification restrictions prevented me from commenting.
A similar degradation has afflicted Popular Science, which I had been reading since 1959. Now it has become a trendy gadget and flashy science trick magazine. No technical art whatsoever; just artist’s concepts. I call it “Popular Seance.”
I enjoyed the Science News until they changed the name to SN.
Incidentally, they published an article called Solar Fizzle on Nov 2, 2013. Because of that article, I got involved in the study of the Sun. Because of the nonsense that they were publishing, it was my last subscription. NOW, age has a way with making people smart. Science 80 taught me a whole lot. Science 90 didn’t.
In Northern Michigan we have small sand islands that move every year. It’s a big day in early spring when we go down to the shoreline to see where the creeks have moved, the sandbars have moved, and how some of the small islands are different shapes and sizes. That all this happens is one of the more amusing aspects of Climate Change. Before Al Gore we never knew that CO2 had the power to move several hundred million yards of sand over a winter, we just assumed it was some other force, like Gnomes, or maybe even aliens.
Gnomic force is a scientific fact. Five centuries ago there was a 97% consensus of the existence of isolated instances of gnomic action. It is very possible that the sand islands you refer to have been moved by gnomic action in response to climate change. This hypothesis, however, requires additional research.
… and funding.
A long-time visitor to Cape Cod, MA, I see islands disappearing and appearing all the time. A reporter missing an island that was there for a couple of years may have a news worth reporting. Reappearing or gaining height is usually “not newsworthy.”
This is exactly the reality described by journalist Richard Orange, regarding his experiences compiling a report on the situation in the Bay of Bengal. Recommended: http://www.spectator.co.uk/2010/02/story-of-a-sinking-land/
Imagine how dumb the world would be, if we approached all matters with this simple minded “five islands lost to rising seas” idiocy.
For example, here in the UK, I note with interest that this year 3 teams have been selected for relegation from the Premier League.
An alarming fact, when it is considered that the League only contains 20 teams.
We can’t afford to lose any teams from the Premier League, never mind three at once.
At the current rate of relegation of teams, within seven years there will be no Premier League left.
Or have I failed to account for some critical aspect of this system?
(satire)
Fremantle, not Freemantle.
http://www.applefritter.com/files/images/HomerSimpson.png
I think it is a reasonable paper. But, as often, they don’t look very far.
1. historical : Evidence for coral island formation during rising
sea level in the central Pacific Ocean
Paul S. Kench1, Susan D. Owen1, en Murray R. Ford1, Geophysical letters.
2. look at the opposite : http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11206600
You read Dutch : http://www.kleurrijkewiskunde.nl/blog/koraal-eilanden-ontstaan-ook-tijdens-zeespiegelstijging/
There’s a headline! Entire country appears out of the sea! We’ll call it the Netherlands!
Or The Low Countries
Where is Nick to tell us this is not true.
The guy has 0 integrity, he sees the nonsense claims and says nothing. No wonder science is a mess with people like this
Better yet, where are Simon Albert, Javier X Leon, Alistair R Grinham, John A Church, Badin R Gibbes and Colin D Woodroffe (authors of the paper) to tell the world that the headline and article in New Scientist has grossly exaggerated and obfuscated their science?
That was a rhetorical question. The real answer likely lies close to: they love the publicity and the future grants that they will now receive regardless of accuracy.
Church is on a research mission, although along with many other of CSIRO researchers he’s been told he’s going to be fired.
I still have the question as to how the paper can conclude that the loss and/or reduction of those eleven islands was due to an interaction between sea level rise and high wave energy.
As you point out, the sea-level rise between 1994-2014 is unusually high for this area (due mostly to the El Nino, La Nina cycles.) However, the paper doesn’t compare 1994 to 2014. It compares five years — 1947, 1962, 2002, 2011, & 2014. Most of the land lost occurred between 1962 and 2002 — although land seems to be lost on the eleven islands throughout this period. There is a generic graph which covers this entire period, but the year to year variation is much greater than the decade to decade variation. It is not clear (to me) which years are meant to indicate the years of the study.
For me, the paper overreaches on their conclusions (albeit it is a far less overreach than the press reports which were based on the study.) I’m not sure how they conclude that the erosion is a synergistic interaction between sea level rise and high wave energy.
Lorcabonda says: For me, the paper overreaches on their conclusions (albeit it is a far less overreach than the press reports which were based on the study.)
I am not at all comfortable with the facile dismissal of tectonics in this very active region.
McCaffrey, R, Slip partitioning at convergent plate boundaries in S.E. Asia, in Tectonic Evolution of Southeast Asia, R. Hall & D.J. Blundell, eds. Geological Society Special Publication, 108, London 1996.
See pages 13 & 14 for Solomons and New Hebrides.
In my opinion, the authors should have had a tectonics specialist on their team.
Robert McCaffrey is now at Portland State University.
http://web.pdx.edu/~mccaf/pubs.html
Even though there is significant tectonic plate movement in the region, I think it is probably justifiable to say that the land area reduction is not due directly to tectonic motion. The islands which did not change area were the ones closest to the tectonic plate, whereas the ones that were reduced are the oldest islands, furthest from the tectonic plates.
That is not to say that the local ocean currents did not shift due to the tectonic activity only that the plate movements did not directly affect the land area.
The paper has an uncited chart to indicate the net ocean currents (based on ten year periods) which show little change in each of these two regions. The Roviana area experiences small, northwesterly currents whereas the Santa Isabel islands experiences ~10x the Roviana current in the southwesterly direction.
But this area of the ocean is one where the sea rises during La Niña and falls during El Niño. That sort of ocean oscillation should act as a “storm surge”, similar to shoreline effects during a hurricane. That’s why the sea level changes so much in that area. The current should show a shift in magnitude and direction as the Pacific Ocean goes though its natural cycles.
The paper references a report in Nature Geosciences (Barnard, et al 21Sep2015) which claims a similar conclusion, “We find that observed coastal erosion across the Pacific varies most closely with El Niño/Southern Oscillation, with a smaller influence from the Southern Annular Mode and the Pacific North American pattern.”
http://hdl.handle.net/102.100.100/22137?index=1
This link provides all the data you need. CSIRO have an on going project for all the islands including the Solomon’s.
Most of the files are restricted for use by the priesthood and their acolytes.
It seems that the paper is good science, although the obligatory obeisance to the gods of climate change is annoying. The press releases however are only loosely related to the paper and pimp a conclusion that they paper does not reach.
It seems that the main problem is not bad scientists doing bad science. It is the politically motivated journal gatekeepers and the awful scientific press releases and science journalists who continue to push this wheelbarrow as hard as they can and who seem immune to reason.
Ian writes, “It seems that the main problem is not bad scientists doing bad science. It is the politically motivated journal gatekeepers and the awful scientific press releases and science journalists who continue to push this wheelbarrow as hard as they can and who seem immune to reason.”
For me, that’s always been the worst part, although some scientists are complicit in providing quotes for biased articles. Nine times out of ten, when you see an article which sounds too incredible to be true, when you read the report it is based on, you see the difference.
It’s a nasty, smelly little ecosystem of shady pseudo scientists, attention whore enviro- journalists and political truth bending opportunists.
A better source of data is the ‘pacific sea level monitoring project’ site.http://www.bom.gov.au/pacific/projects/pslm/index.shtml
I don’t see much of a trend here… http://www.bom.gov.au/ntc/IDO70061/IDO70061SLI.shtml
Process (not content) comment:
As a non-scientist WUWT reader for 5+ years, I’ve learned to love the cycles of “warmest publication/claim & WUWT factual take-down” (observation: latency of WUWT responses seems to have gotten much shorter over the past 12-18 months).
Personal favorite: warmest claim polar bears are endangered and populations are rapidly collapsing; WUWT factual response: no evidence exists to show anybody ever really inventoried polar bears, but best expert guess is population may have doubled since 1950’s. The undisputed factual gap (nobody actually counted the bears) was stunning.
It continues to astound me that any scientist would pump out this simple-minded junk. Climate science seems to have crawled back into the dark ages and angels once more dance on heads of pins…
Civilisation is two steps forward and one step back. We seem to be living in a one step back world right now.
The angel/pin question appears to be a canard: https://en.wikipedia.org/wiki/How_many_angels_can_dance_on_the_head_of_a_pin%3F
“The need for rationality as complementary to faith was raised as an important point for Catholic theology” and I think most WUWT readers would agree that rationality is an essential counterbalance to climate Faith.
Now, take that analysis one step further. Polar bear studies provide us with a perfect example of how to achieve conservation goals. The problem with polar bears had been over-hunting with modern weapons and over-hunting of their food source — most people remember the furor over harvesting seal pup fur.
The recovery of seal populations and the legitimate hunting restrictions is what saved polar bears. And these are the same primary dangers for almost all species. It doesn’t help to target the fifth or sixth greatest danger without addressing the primary ones. That’s what climate science has become — the excuse. See how many articles you find which say that report that we are in the midst of the sixth great extinction, so we must address climate change.
The logic is backwards. They skip the step of identifying the causes of extinction to address them.
The aspect of your statement dealing with seal hunting is nonsense. Seal populations always ran in the hundreds of thousands. The fur hunt hardly dented their numbers.
Lorcanbonda:
Nor has there been ‘unrestricted hunting’ of polar bears for over a half century. The areas where polar bears were hunted have been restricted for quite some time.
Plus the fact that polar bears get fat eating nesting snow geese sure helped their populations as the snow geese recovered from hunter sought ‘waterfowl conservation’ heavily based in habitat restoration.
Claims that
are greatly overwrought and based on misinformation, terrible poorly conducted research, and just plain fallacy alarmism.
As Willis has pointed out; where are the bodies of the extinct/endangered creatures?
The greatest danger, worldwide, to the vast majority of ‘endangered animals’ is loss of habitat.
Many animals suffer from even the slightest human interference; e.g. golden eagles, condors.
Most African animals prosper under the safari hunt operations, but suffer greatly when the safari operations are eliminated and humans poach animals, wood for fires, and plow/irrigate land for crops.
So often the endangerment of an animal is left at the ‘loss of habitat’ description with zero information on exactly what that means. An intentional misrepresentation as the ‘animals are humans’ eco-bananas groups use that misrepresentation to prey upon millions of misinformed animal lovers.
The press announcements of the above article by the eco-bananas crackpots, as ‘habitat loss’ brings up the specter of rare animals disappearing with the islands.
Meanwhile the same groups ignore the massive flying animal kills, including endangered species, by wind and solar farms.
The Earth has actively changed since it became a planetoid. When the Earth ceases changing rapidly will not be a pleasant time for Earthbound creatures.
No wind eroding.
No rain eroding.
No seas eroding/building land.
No storms cooling and spreading heat…
The (Canadian) Inuit had claimed for years that the “science” was wrong.
Polar bear numbers had been reduced by over hunting and when hunting was banned their populations increased rapidly. Eventually their numbers will be controlled by limits on the food supply.
Readers should not be surprised if a decade from now, polar bear numbers have fallen because of intense cold.
I have no evidence to make such a prediction but have come to expect the opposite to happen when politically inspired predictions become the consensus.
Your Fremantle sea level reconstruction graph seems to show the Solomons [superimposed] as rising out of the sea recently.
Fremantle sea levels are possibly a poor choice as there was a lot of fuss 8 years ago about these levels as parts of the West Australian coast were controversial due to land subsidence problems in a large area there?
Plus they are too far away.
Fremantle is not subject to the same tectonics as the Solomons.
It’s the closest reconstruction in the NOAA database and it’s a fairly good match over the satellite record.
The sunken islands are north of main island chain, the area least affected by tectonics in the Solomons.
No it doesn’t seem “to show the Solomons [superimposed] as rising out of the sea recentlly.” The island area data start in 1947. The Fremantle reconstruction data start in 1795.
The Fremantle sea level reconstruction is derived from corals, using isotope geochemistry. It is the closest reconstruction in the NOAA database and it is a fairly good match to the Solomon Islands over the satellite era (1993-2016).
Word of advice to the “experts”
Any land that disappears with a 6″ rise in sea level isn’t an island, it’s a sandbank.
I’ve published a similar analysis but using data from Samoa as a proxy. It is at:
http://www.climatedata.info/discussions/blogger/index.php?id=8349355752109785634
Ron, thanks for this. I have saved to Pocket. The example for the Bay of Bengal is especially relevant because it’s a favourite target for propagandists.
Counter headline: ‘Global warming confined to five islands in the Solomons’.
I am confused. According to http://www.fremantlewesternaustralia.com.au/fremantle-history.htm, Fremantle Western Australia was not founded until 1829. Yet tide gauge readings are shown going back to 1795. Can someone please explain?
Fremantle is a reconstruction from proxy data (corals and scerlosponges).
Why is it that scary climate research pronouncements (by the media or the researchers themselves) end up in the same pile standard school text book “genetic traits” do?
http://udel.edu/~mcdonald/mythintro.html
Speaking of Western Australia some nice pics of coastal erosion due to TCs in the TC capital of Oz
http://www.bom.gov.au/cyclone/history/wa/onslow.shtml
and that’s in a very old and stable continent
Erosion is another disallowed word in the Climate Cultural Revolution.
The discussion has covered “real” sea level rise, erosion, and tectonic adjustment. There is generally no discussion of the fact that the “sea level” is actually hydrostatic conformance to the “geoid,” which is a constant-potential surface of the Earth’s gravitational field. The geoid is not a simple surface, being described by harmonic components in latitude and longitude. These components change over time as the internal structure of the Earth changes. (For example, this affects the ephemeris of low-altitude satellites.)
In other words, perceptions of sea level increase or decrease may also be a result of geoid changes having nothing to do with the total mass of seawater present in the oceans.