Guest Essay by Kip Hansen — 23 February 2025 — 1600 words
This is not about California’s nutty politics – but it could have been.
This is about Vertical Land Motion (VLM hereafter). VLM is the movement of the surface of the land further from the center of the Earth (up, a rise or uplift) or closer to the center of the Earth (down, a fall or subsidence).
For many locations in North America, VLM is associated with Glacial Isostatic Rebound. Basically, as the massive weight of ice on the northern part of northern continents melted away, that portion of the continental that had been depressed by all that weight, had been rebounding, rising. At the same time, the southern part of that continental sheet , having been teeter-tottered or bulged upward during the Ice Age, is moving back down.
On the U.S. East coast, the land mass north of Boston, MA , which is approximately the hinge point, is uplifting and the land mass south of Boston is subsiding. On the U.S. west coast, parts of Alaska are uplifting and points south are subsiding, from the effects of Glacial Isostatic Rebounding.
Note that all the Relative Sea Level Rise arrows on the California coast are in the “0 to 1 feet per century” range – that is VLM + Absolute Sea Level. Absolute sea level is understood to be about 1.7 to 2.0 mm/yr – 7 to 8 inches per century.
California has a lot of VLM, both subsidence and uplift, and some of it pretty extreme. A recent study, that has measured VLM in California in several different ways, shows this map:
[click here for very hi-res image in new tab/window]
The most obvious feature is the serious major subsidence in the Central Valley – the dark blue blotch that runs diagonally across the state. The coastal areas are generally neutral and pale blue-ish, indicating either no movement or slightly subsiding. But, it is important to look at the scales. There are two scales given. The top scale if for large scale subsidence – darker blues through greens to lighter colors. This scale is for +/- 100 to 200 (or greater) mm/year.
The lower scale is in single digit mm/year, +/- 4. This lower scale of subsidence, 0 down to -4 mm/yr, is equivalent in magnitude to the rise in absolute sea level.
And, that is the important point. The coastal portion of the state of California is generally subsiding at a rate of 1 to 4 millimeters per year. At the same time, it is generally understood that absolute sea level, often called “global sea level”, is rising at about 2 to 3 mm/yr [when using global tide gauges for the calculation]. In effect then, Relative Sea Level Rise along much of the coast of California can be said to be ‘doubled’ by subsidence.
To be blunt, the Realtive (or Absolute) Sea Level Rise of 2 to 3 mm/yr is not an alarming or dangerous amount. In a century, 100 years, 3 mm/yr comes to 30 cm or 1 foot. Most areas have already seen that 1 foot of SLR over the previous century without disastrous effects. To counter-act that 1 foot , those 30 cms, of sea surface rise, a sea wall or dock curbing 16 inches (440 mm) high, made of two standard 8x8x16 inch concrete blocks (in the EU, 215mm x 215mmx440mm) suffices.
And if we double that amount of Relative Sea Level Rise, say to 6 mm/yr, half of that being subsidence, the total rise comes to 24 inches, 2 feet or 60 cm.
Now, 2 feet, that’s getting to be something to talk about for locales that have infrastructure built far too close to current sea level or too close to the sea level of the past, which is far more common. And for locales that have very little altitude above sea level altogether, such as low-lying lands, filled salt marshes turned into sea-level-plus-1-foot neighborhoods of houses with backyard docks on canals and other high-risk areas. Those low-lying areas are often spoken of as being “at risk from flooding by sea level rise and storm surge”. And they are, and they already were, even a century ago. They are more at risk today and will be even more at risk after another 100 years.
The reason they are at risk is their relative altitude above sea level. One foot, two feet, five feet, six feet – the same in meters – it doesn’t matter. Storm surge can be as high as 14 feet – over 4 meters. The surface of the sea will reliably rise about one foot – 30 cm – over the next century and to that must be added any local subsidence.
But what they are not at risk from is Climate Change. The best long-term studies of relative sea levels around the world show that sea level has had a long steady and slow rise since man has been actively measuring it.
The claims that melting land ice is a major contributor have not been shown to be true. Water from melting land adds to the absolute sea level rise that is caused by expansion of the sea water due to the gentle warming of the oceans as the world continues to come up and out of the Little Ice Age. By current rather vague calculations, melting land ice — glaciers, Greenland, Antarctica – may be adding up to 1 mm a year – few inches, 10 centimeters per century. The uncertainty stems from the absolute uncertainty of Antarctic ice mass: is it growing or declining, adding mass or losing mass? Even NASA, which measures Antarctic Ice Mass is not sure, it has two teams that find totally different answers, both answers derived from the same data sets.
To fight Climate Change the IPCC and the UN (and everyone else on the bandwagon) say we must decarbonize our societies, we must quit adding CO2 to the atmosphere regardless of cost.
Combating Climate Change may or may not be a good idea – I don’t think it is – but one thing it will not do is slow or stop sea level rise, not even the fraction of sea level rise actually caused by warming seas. Reducing CO2 emissions, atmospheric concentrations of GHGs or sequestering CO2 underground or in rocks certainly cannot change the portion of relative sea level rise caused by subsidence.
Spending tax payer’s money, or society’s wealth, to fight Climate Change will do nothing to prevent today’s or tomorrow’s problems stemming from rising seas. Those funds must be spent on adaption to and mitigation of any negative effects of rising seas.
Wild and alarming “predictions” of meters of Climate Change-driven sea level rise “by 2025” – in the next 30 years – are scientifically ludicrous as such a future is literally impossible.
It is however possible to drive very local Relative Sea Level changes by seemingly impossible amounts through human activities such as extracting water, pumping water out of aquifers below the surface, or pumping up huge volumes of oil, can cause substantial subsidence and conversely, forcing volumes of water or gases (such as in fracking) down into the Earth under pressure (causing uplift).
Bottom Lines:
1. The seas and oceans are rising, have been rising and will continue to rise until the planet again enters a period of cooling, similar to the Little Ice Age or a real full-blown ice age.
2. Current rates of sea level rise will not be changing much. If a locality is not currently at risk, it will not be at risk in the future – sea level rise is too slow.
3. Human infrastructure already at risk will continue to be at risk and that risk will increase in the future – slowly and steadily. Such localities should spend money and effort on adaption and mitigation.
4. Vertical Land Motion – up and down – are important factors for localities to consider when looking at risks from relative sea level rise. Nothing in the fight against Climate Change will effect VLM. Some of the VLM can be mitigated; such as ceasing to extract fresh water or oil close to the sea. Some of the VLM-caused Relative Sea Level Rise must be dealt with by adaptation – raising structures, building seawalls and otherwise protecting infrastructure.
5. Alarming projections of dangerously high near-future sea level rise are not possible, thus the dissemination of those projections must be seen as politically-motivated Climate Alarm propaganda.
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Author’s Comment:
There is nothing particularly new in this essay, except for the very interesting study on California VLM – look at the Central Valley. Some of that subsidence may be self-correcting as atmospheric rivers bring lots of new water to recharge the underlying aquifers. But those aquifers have been being pumped out at tremendous rates to irrigate fields, orchards and vineyards for a long time.
But, in general, coastal California has little to worry about – most seafront areas are backed by bluffs, huge remnant sand dunes in some places like Manhattan Beach, that rise rapidly, like most of Los Angeles.
There are areas around the edges of San Francisco Bay that are just filled wetlands right at sea level and then you have the Sacramento River Delta. The surface of the Sacramento River at Washington Lake in Sacramento, 87 miles across the Bay and upstream, is only 6 feet above San Francisco Bay. They are potentially in trouble now.
Rising Sea Level scares are just that – scares. It is far past time to begin to adapt and mitigate.
Thanks for reading.
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Fight government corruption first and resolution of most problems will follow.
I think the weight of all of the government corruption in California is responsible for a significant portion of their downwards VLM.
All the corruption in Commifornia is causing large amounts of treasure and property to exit the state to safe havens for the crooks; therefore they must be lightening! It only FEELS like lead weights crushing you; relief is nearly instantaneous crossing the border!
Excellent review, Kip. VLM made me think of “earth tides.” The planet is amazing.
I asked Grok3.
Please summarize the concept of “earth tides” in two or three sentences and give the typical amplitude and period at, say, mid-latitude locations.
Answer:
“Earth tides refer to the subtle, periodic deformations of the Earth’s solid surface caused by the gravitational pull of the Moon and, to a lesser extent, the Sun, similar to how ocean tides work but affecting the planet’s crust instead. These tides cause the ground to rise and fall slightly, typically by about 10 to 40 centimeters (100 to 400 millimeters) in amplitude at mid-latitude locations, with the primary periods being semidiurnal (about 12 hours) and diurnal (about 24 hours), depending on the lunar and solar cycles.”
I make no claims as to whether Grok got this completely right or not. Most likely OK.
Dave ==> Gonna have to think about that — 400mm is almost 16 inches….every 12 hours?
More here.
https://en.wikipedia.org/wiki/Earth_tide
David ==> Interesting — wonder why/how these affect the uplift/subsidence measurements in the study quoted? I have not seen Earth Tides appear in CGPS records, location every six minutes…..
My guess is that it all gets lost in the averaging of GPS vertical land position references related to ocean tide gauges.
Not sure though.
Remember that the ocean tides will follow the earth rides keeping the shoreline unchanged.
Most modern buildings won’t last 100 years, much less 200. When they are ready to be replaced, tear them down and instead or rebuilding on the same spot, rebuild a bit further inland.
Problem solved.
When nature moves, the smart thing to do is to get out of the way.
Mark ==> Now, don’t get all reasonable … we must rebuild everything exactly where it was already destroyed by the forces of Nature! We can’t let Nature win.
Seriously, much of the problem is that we want water-front infrastructure to be at the waterfront. We like our oceanfront homes, we like the Miami-style dock-on-a-canal in my backyard. Marinas and docks and warehouses more or less must be close to sea level.
It is silly for us to complain when necessary location has natural drawbacks.
We just have to adapt to new conditions.
My house is at an elevation of 2,240 feet. The Pacific Ocean is 180 miles west. That is about as close as I want to be to an oceanfront home. 🤠
After the big quake hits, it will be oceanfront. (Cue Peter Fonda riding the tsunami on a surfboard.)
There’s another cause for VLM that is common for Northern California and points northward.
As the Pacific plate pushes inland, it causes the edge of the North American plate to bulge upward.
When the accumulated stress gets too high, the edge of the North American plate snaps back to a flatter position. This can drop the shoreline several feet in a matter of minutes.
MarkW ==> Can you an historical instance of “drop the shoreline several feet in a matter of minutes”? A quick look at sea levels at Astoria, OR since 1925 does show a shift like that. Not saying it doesn’t happen, we’ve had earthquakes galore, but can’t remember a big shift in recent memory.
Apparently, the tectonic shift that caused the 2011 tsunami in Japan lifted the seabed 10 meters upward instantaneously:
https://www.nationalgeographic.com/science/article/111201-japan-earthquake-tectonics-earth-tsunami-science
As well as shifting the planet’s axis and shortened the length of days:
https://www.iflscience.com/in-2011-a-magnitude-9-0-earthquake-shifted-the-planet-s-axis-and-shortened-earth-s-days-67887
I didn’t feel a thing. A few feet in a matter of minutes seems plausible.
Raising the sea bed 10 meters would have slowed the Earth’s rotation.
There must have been an even larger movement of land somewhere else in order to speed up the Earth’s rotation.
(In this case larger includes the amount of land that moved, not just how much that land moved.)
“Raising the sea bed 10 meters would have slowed the Earth’s rotation”
Or maybe not. It might depend on where the displaced mass came from. The Earths total mass didn’t change – just its distribution.
Slowing or speeding might equally result. Or, if resulting in unbalance relative to the axis of rotation, a wobble. Who knows?
The up-down action occurs at convergent plate boundaries such as Washington State and the Cascadian Subduction Zone. See:
https://pubs.usgs.gov/publication/pp1707
Transform boundaries – plates slipping past each other – do not have this action.
Yes, vertical displacement is one of the consequences of convergent plate margins but is also not uncommon on continental crust transform boundaries – San Andreas fault zone, for example. One of the results of the SA fault motion is the emergent topography (uplift) along most of the California coast (not to mention the B&R extension). All those picturesque uplifted terraces that define the California Coastal views (Pacific Palisades, Palos Verdes, etc.) make the CA coastline a poor area to investigate VLM unless the underlying longer-term geological processes are considered.
MarkW ==> It is possible to see the 1906 Great San Francisco Earthquake in the sea level trends graph at NOAA’s Tides and Currents here: (It is the SOLID line,not the dashed line)
I’ve read that one of the reasons why the sea walls failed during the Fukushima earthquake was because the land that the sea wall was sitting on dropped by a meter or two before the tsunami struck.
I’ve read that one of the reasons why the sea walls failed during the Fukushima earthquake was because the land that the sea wall was sitting on dropped by a meter or two before the tsunami struck.
Further north …..the Oregon-Washington area is where the pacific plate is pushing below the N, American plate and the N. American plate is sticking to the Pacific ….until it slips….then big tidal wave and earthquake,
Hi AG,
I may be mistaken, but I think the relative motion of the Pacific plate is to the Northwest relative to the NA plate. There is a subduction zone in Southern Alaska.
There are three smaller plates, Juan de Fuca is one, that are subducting under the NA plate (Easterly motion relative to the NA plate), and a corresponding spreading zone between the Juan de Fuca and Pacific plates West of the subduction zone along the OR, WA, and BC coast. These are the ones we worry about as causes of “the big one” in Cascadia. I believe historically they happen about every 300 years or so. There was significant vertical displacement for those events. The 2001 Nisqually event shook Seattle a bit, magnitude 6.8. Some of the old masonry buildings near Pioneer Square collapsed. Out in the Eastern ‘burbs, it shook hard enough for me, and opened cracks in parking lots and roads. Big enough but not “the big one”.
There’s an interesting triple junction at the N end of the San Andreas where it intersects the Juan de Fuca or the Gorda plate, near Mendocino, Cali.
I don’t get it. At the beginning of the article you state “Absolute sea level is understood to be about 1.7 to 2.0 mm/yr – 7 to 8 inches per century”. Then a couple of paragraphs later you say “To be blunt, the Absolute Sea Level Rise of 2 to 3 mm/yr is not an alarming or dangerous amount. In a century, 100 years, 3 mm/yr comes to 30 cm or 1 foot”. Which is it?
NOAA publishes in fairly obscure ways absolute slr is 1.7mm/year +/- .2mm with 95% confidence based on 150 year record. Which one is it or are these just opinions?
Please excuse my exasperation.
Even that 1.7mm is beyond the measurement capability. It’s a wild guess.
Jeff ==> Yes, but it is our best wild guess…..
It’s not a wild guess. That is why this subject is exasperating. The measurements are actually etched in stone at The Battery in New York, San Francisco station 9414290 and many other sites and has been continuously monitored for over 150 years. There are lots of guesses, models and opinions around AGW, Sea level rise is not one of them. 1.7mm is the average of the 150+ year sum which is easily measured with a yard stick. Lets respect what little data we have.
“absolute slr is 1.7mm/year +/- .2mm with 95% confidence” is a quote, albeit from memory. It used to be a prominent graph on NOAA’s website and reposted in Wikipedia. Then it was reduced to fine print in a foot note. Now I can’t find it at all. Flush the politicians out of NOAA. Make American Science Great Again. MASGA!
Tide gauges have sub-millimeter accuracy? Average sea level rise is as useful as averge global temperature.
Jeff, you’re right. 0.1 of a millimeter is about four thousandths of an inch – a thick human hair.
Ah, the miracle of averaging – combined with extreme gullibility.
Making American science simply science would be enough.
Citizen ==> Sloppy writing, I’m afraid. The second instance should read “To be blunt, the Relative Sea Level Rise of 2 to 3 mm/yr….” (I’ve corrected the text above….)
NOAA’s tide gauge-based average global SLR is pegged at 1.7/1.8 mm/yr. They will also happily quote the satellite-based 3.4/3.6 mm/yr for the same metric.
You’ll have to read my full SEA LEVEL: Rise and Fall series for all the gory details.
The point I am making in this essay is that it really doesn’t matter which figure you use…whatever the real physical-world rate of sea level rise is, between1.5 to 4 mm/yr, it is slow and not dangerous — it just has to be accepted and dealt with.
Kip, I have read all your stuff on SLR and appreciate it.
Why are the houses on Millionaires Island in Miami still being bought? The whole bunch are at best only 1 foot above sea level.
ferd ==> The millionaires don’t care — they are in the “live for today and don’t worry about tomorrow” mode. That’s Miami’s Vice.
Nice post, Kip!
Far more worrisome to residents of the Eastern Pacific coastal region than sea level rise should be the ongoing major tectonic activity throughout the area! The Pacific coast, from Baja to Alaska, is undergoing constant movement as the North American Plate rides up over,and rotates counterclockwise in relation to, the Farallon, Juan de Fuca, and Pacific plates! The movement of the Sierra Nevada/Klamath crustal block to the northwest has already rotated the state of Oregon into it’s current position, while compressing the state of Washington at the Yakima Fold and Thrust Belt. Further movement along the San Andreas and Walker Lane fault zones continues at roughly the same order of magnitude as VLM, and is far more concerning; major seismic motion could destroy coastal cities like LA, SF, Portland, and Seattle with tremors OR tsunamis!
If only more children received a proper education; then they would be worried about real problems like pollution, war, and global poverty; and could stop fearing a beneficial, trace gas that is the basis for Life on Earth!
Abo Man ==> well, you’ve got that right. The problem is propaganda instead of facts in the schools….especially on these controversial ideas. The teachers themselves were taught misguided concepts (falsehoods) in Uni and teach them to your kids.
Kip,
Crustal shortening in Wash. is currently estimated to be as much as 5.0mm/yr; NW motion of the Sierra Nevada/Klamath block is ~10mm/yr! Many of the rocks in the Cascades were formed as oceanic crust at various depths; they now are exposed at elevations of 2,000 to 3,000 meters, giving a total vertical displacement of 10Km or more!
Worry about SLR is scary campfire story!
Measuring the tiny changes in sea level is NOT simple. Interpreting the increase as land lost turns out to also be incorrect, as I am certain Kip Hansen knows.
Even WITH the putative sea level rise and land subsidence, since 1980, there is a net gain of over 15,000 km2 of land at the coast lines of the world (https://www-nature-com.libproxy.wustl.edu/articles/nclimate3111.pdf).
This is a simple, accurate measurement using Landsat and other imaging satellites.
The net gain is largely due to erosion, at which water is very effective. Even Bangladesh, the poster child for inundation, has gained over 1000 km2 in the same period (measured by Bangladeshi scientists). These results are in the refereed science literature since 2015. National Geographic even had a lead article on the topic, including the Pacific and Indian Ocean islands supposedly sinking beneath the waves (http://dx.doi.org/10.1016/j.ancene.2021.100282). Those islands are naturally nourishing themselves and remain stable, EXCEPT where they are being strangled by human sea walls, groins and such. That fact signifies that the journal Anthropocene is appropriately named in at least ONE instance.
whsmith ==> Yes, I do know. And have written here and elsewhere extensively on the issue. If you are not familiar with it, I have a Sea Level Rise series here, written over a period of years, which starts here.
So many “journalists” working today have been trained to push popular (and sometimes, mandated) narratives instead of a broad overview of facts and viewpoints meant to inform the reader.
Dealing with shorelines is an ongoing learning process for engineers, city planners, state legislatures, etc. We don’t like seeing our favorite beaches washed away or our shoreline barrier island communities cut off from the mainland. we just don’t know how to deal with it. My suggestion has been to abandon such areas to Nature. Not a favored viewpoint along the New Jersey shore!
Duck Assist tells me:
“Once land has subsided due to groundwater extraction, it often does not rise back to its original level, as the compaction of sediments can be permanent. Even if groundwater levels recover, the land surface may continue to subside for years due to ongoing dewatering of fine-grained layers. “
John ==> Yes, both can happen. Some “lens” aquifers recharge and lift the land, as I understand it. Others just empty out, the sediments and soil compact and there is no uplift even when water gets back down to that level. All depends on the mostly-unkown details.
Kip
what does this mean to California?
One Of the Most Active Volcanoes In the World Is About to Blow
Henry ==> Probably nothing. According to MSN “any eruption won’t be explosive but will instead ooze out lava and form new seafloor. This means there is no threat of a possible tsunami to the nearby coast.”
There is a YouTube from 2024 of research about it, 3 and a half minutes. Important work if one is an oceanic volcanologist, but otherwise, only interesting.
It is, however, a prime example of misleading scary headlines — the article beneath the headline, however, is not alarmist — only the headline.
hope everything will be all right
According to the article, that volcano hos erupted something like 4 times since the turn of the century.
Nobody noticed those eruptions. Nobody will notice this one either.
If the sea mount ever gets to within 100 feet of the surface, the Coast Guard will probably adjust the shipping routes to make sure ships don’t get too close.
> The surface of the sea will reliably rise about one foot – 30 cm – over the next century and to that must be added any local subsidence
A Cascadia event could toss that addition out the window. Heck, just the right plate movement conditions could harken the return of Lake Corcoran. Sure, a century is but a blink of geologic time but the Western US is statistically overdue.
Giving Cat ==> Should the other volcanic giants of the Cascades (particularly Mount St. Helens) sound off, all bets are off….However, the historic Lake Corcoran, in California’s Central Valley, is unlikely to return due to events that far north, I wouldn’t think. If we are talking a major tectonic event, well, then I wouldn’t be willing to speculate.
Lake Tulare returned with just a little more rain….(1942, 1969, 1983, 1997, 1998, and 2023).
Most American’s are not well educated in the geology of the West. Yellowstone, California, the Cascades, etc. Willfully, blissfully ignorant.
> Most American’s are not well educated in the geology of the West. Yellowstone, California, the Cascades, etc. Willfully, blissfully ignorant.
Indeed while it is also obvious we both are willfully, gloriously, assertively immersed in the grandeur that is the Western US.
Woodland-Davis-Elk_Grove-Roseville is effectively at sea level without tides. It wouldn’t take much.
Giving Cat ==> Yes, The Sacramento River at Sacramento is only 6 feet, 2meters, above the surface level of San Francisco Bay. That’s very little drop for water to flow downhill. Other Central Valley locales are disturbing low in altitude.
As a kid, working on my uncle’s cattle ranch in the San Joaquin delta, I would often see freighters passing by on their way to the Port of Stockton. U.S. Mail was delivered by boat to a little pier, but I was not allowed to fish from it!
Nice map:
https://en-us.topographic-map.com/map-p5f3/Sacramento/?center=38.55676%2C-122.00317&zoom=7
Still freaks me out to be driving farm roads in Yolo County and seeing ocean going container ships cruising by.
I’ve read where land in California’s central valley has subsided up to 18 feet due to ground water extraction to support agriculture. And most of that agricultural output leaves the state if not the country. Feeding people is BIG business and accounts for a good share of California’s economy. Some Southern counties in CA are putting recycled sewage water back into the aquifer. It should be a requirement of all sewage treatment plants.
mleskovar ==> Down-pumping water has become a popular thing — but I have not seen anything that really support the practice — no signs of resulting uplift. Maybe it really does recharge aquifers — in a sense — but not sure it has a real world effect that makes it sensible.
However, replacing other fresh water sources with treated water from treatment plants — such as golf course watering, municipal parks, ball fields, road verges, etc makes a lot of sense.
Ever since the Earth cooled enough for rain to make it all the way to the surface, land has been eroding into the sea.
That dirt being deposited in the ocean raises the sea level. However, the land getting lighter causes the continents to rise. Of course, the two affects operate on vastly different time scales.
Rain probably started to fall shortly before the land became cool enough for liquid water to exist in contact with the land. Convection would lift the air, until it because cool enough for water to condense. Rain fell but evaporated before it could hit the ground.
MarkW ==> Yes, sedimentation must, reasonably, cause some rise in sea surface levels — but I have never seen a calculation or even a guess-timate of by how much. Remember, it is a volume problem — continents are moving around, widening or narrowing sea basins, sea floors lift and fall, a lot going on.
“The best long-term studies of relative sea levels around the world show that sea level has had a long steady and slow rise since man has been actively measuring it.” That is sort of true. The longest tide gauge record is probably the gauge at The Battery on the southern end of Manhattan Island. It is mounted on bed rock and has been recording, but for a hiatus during the Civil War, since around 1850 and shows a very steady relative sea level rise of about 3 mm/yr of which about half is from the land settling perhaps from the teeter totter effect you describe from the glacial age ice sheet that once was to its north. Another bedrock-mounted gauge has been operating at Pier 9N in Philadelphia since 1900 and shows the same. However, Larson et. al. of the USGS estimated sea level rise in coastal areas of the Chesapeake Bay from peat bogs and river sediments concluding that sea level has been rising at 1 – 3 mm/yr for the past 6,000 years, i.e., since the end of the very rapid relative sea level rise that occurred during the ending of the last glacial age. The fear mongers arguing that all us coastal-livers are going to drown by 2100 are simply ignorant of the facts, probably willfully so since they are so easy to find.
Denis – Pier 9N in Philly is located in alluvial deposits of the Delaware River that overlie coastal plain sediments. There isn’t any bedrock exposed in the immediate area. Probably lots of compaction and consolidation of sediment has occurred at this site over the last two centuries
Peter and Denis ==> Snay et al. 2013 found VLM at Philadelphia to be about 1 mm/yr. Nearly all waterfront structures subside because they are built on the waterfront. Filled marsh, riverside mud, foundations undercut by rising and falling tides. Eventide gauges mounted piers on wooden pilings subside because the pilings themselves shorten over time.
Denis ==> The Chesapeake region has another problem — subsidence caused by the settling of the subsoils/rocks due to a meteor strike thousands of years ago. I have written about it somewhere….
California uses sea level predictions derived from a sea level risk analysis. The analysis promulgated a table which shows there is a 17% chance that sea level rise will be 0.6′ (~7 inches) for the La Jolla area by 2030. This despite saying in the analysis that historical sea level rise has averaged 2,04 mm/yr. over the last century. By year 2100, there is a 17% chance of a 3.6′ rise.
What part of the La Jolla area will relative sea level rise by 0.6′ by 2030??? The Rose Canyon (which appears to be part of the Newport-Inglewood fault) runs between between downtown La Jolla and La Jolla Shores, so those two areas could have different rates of relative sea level rise.
FWIW, 0.6′ in 5 years sounds unlikely.
Greg ==> You have discovered the idiocy in these projections….there remains less than 5 years to 2030. To get 7 additional inches at La Jolla — 178 mm — requires sea level to rise at a rate of over 35 mm/yr.
The “chance” of that is ZERO.
Note that “chance” or “probability” is not real — ever. This is a physical process. It has causes for effects.
Especially since the SLR from ~1970 to present at La Jolla Cove can’t be over 1′ (if that) according to my eyeballs.
There is an underwater canyon between La Jolla Cove and La Jolla Shores – the Scripps Institute pier is at the north end of La Jolla Shores. For the old fogey’s who remember SeaLab, that was less than a mile offshore from the Scripps pier.
Very nice,Kip.
Mean Sea Level in Sydney Harbour and at Hobart has remained the same,e since 1880. This is due to the extreme lumpiness of water in other locations! https://researchonline.jcu.edu.au/38366/1/38366%20Parker%202015.pdf
ntesdorf ==> The Sydney record is a bit of a controversy, which is why Parker wrote the paper.
But Alex-Nils Morner agrees with Parker.
Just a couple of examples of how the ground beneath our feet rises and falls – marine fossils are found at altitudes of over 6000 m. Relative sea level dropped by at least 6000 m.
On the other hand, oil has been found at a vertical depth of over 9000 m. Relative sea level has risen by 9000 m or so.
All in all, relative sea levels have demonstrably varied by about 15000 m – at least.
What’s the point of worrying about the thickness of a human hair (around 0.1 mm) in 15,000,000 mm? Unless you’re a doomsayer of the “climate scientist” variety, of course!