Sea Level Isn't...Level

There's a reason it's correctly referred to as "MEAN sea level (MSL)."

What they're referring to are the HIGH and LOW tide maximums. Due to earth's rotation and moon's gravity, there'd be more water to pull up during high-tides and thus less water during the simultaneous low-tides.

...and, yes, I have been to Newfoundland, Greenland and Iceland.

"...What they're referring to are the HIGH and LOW tide maximums. ..."

They are actually referring to the gravitational pull of the ice when on land as opposed to the additional water in the ocean when it melts. The sea level both high and low tide would be lower around Greenland if all the ice were to melt off Greenland and flow into the ocean.

"...water to pull up during high-tides and thus less water during the simultaneous low-tides ...".

This doesn't seem right. Do you have any reference for this phenomena? SolarEagle has mentioned a similar phenomena in another thread, so there might be something to it.

So if the mean sea level has risen 1 ft in the last 100 years, shouldn't I be several meters underwater right now? ..you know being in the southern Hemisphere and all...

Supposedly we were approaching an ice age, and the Moon is moving away from the Earth, so maybe all these things are balancing each other out....

"30% more than the global average" would not be several meters, I swag! 1 foot 4 inches to your 1 foot/100 year rise.

Couldn't tell you - I never heard of it!

Our local beach is rocks both large and small, and the shape of the beach is often completely rearranged by stormy tides. So my naked eye is no use for that.

All the same, there is a narrow band of sand near the water's edge at low tide in the relative calm of summer, on which the caplin do spawn. I think about losing that in a sea level rise scenario, vs a drop in the mean sea level would expose a bit more of it.

But perhaps that sandy band also moves more than I think, and maybe it will always be around the low tide mark because of how particles settle as the tide goes out.... no matter what the MSL is.

OTOH I know the earth's crust may trend up or down in a given location - I don't mean with the tides, I mean what they call "subsidence" for example.

https://www.globenewswire.com/news-release/2019/07/16/1883668/0/en/It-s-Official-Louisiana-is-Sinking.html

Well don't you think that is something that should be considered in discussing sea level rise?

..."The semidiurnal amplitude of terrestrial tides can reach about 55 cm (22 in) at the equator which is important in GPS, VLBI, and SLR measurements.^[8][9] Also to make precise astronomical angular measurements requires knowledge of the Earth's rate of rotation (length of day, precession, and nutation), which is influenced by Earth tides (so-called pole tide). Terrestrial tides also need to be taken in account in the case of some particle physics experiments. ^[10] For instance, at the CERN or SLAC, the very large particle accelerators were designed while taking terrestrial tides into account for proper operation. Among the effects that need to be taken into account are circumference deformation for circular accelerators and particle beam energy. ^{[11] [12]"...}

^{https://en.wikipedia.org/wiki/Earth_tide}

".... Well don't you think that is something that should be considered in discussing sea level rise? ...."

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It should be considered for a scientific evaluation of sea level rise. Even in an informal discussion such as this, it would be silly to fail to consider it now that the topic has been raised.

Here is my cursory consideration: If terrestrial tides are well synchronized and in phase with marine tides (which seems likely as the perturbations are the same and the change propagates far below the speed of sound in the respective media) any change in sea level relative to the continental crust is likely to be inconsequential (foregoing significant plastic deformation or novel fracture or non-reciprocating slip.)

Terrestrial tides should be influencing the shape of the planet towards a prolate ellipsoid shape. If a typical point on the surface has a total change in distance from the center of a couple feet, this over a surface area representing a large portion of the Earth's surface. It is unlikely any seafloor trenches would be squeezed sufficiently to result in changes in volume of the sea that might be measured. However even if this were the case, the the rise and fall would already be accounted in measurements taken.

It seems the method of measurement has changed over the last 100 years, how can accuracy be assured? If they're using satellites today, what were they using 100 years ago? ....or are they not measuring it at all and just relying on models that account for estimated ice melt amounts contributing to sea level rise..? ...and then making measurements that agree...

Seems rather linear for something that varies as much as the weather does....

Seems the rate of rise is rather tame compared to the past...Global warming has been happening it seems for some time....

i suspect that you are correct that the accuracy of the satellites is probably much better than measurements taken using the shifting sands under our feet as a reference.

Satellites should be able to provide much more widespread measurement of land height, sea surface height and the height and area of ice surfaces above sea level. To that extent, ice above sea level that melts mostly go into the oceans or displace other fresh water reserves which in turn will end up contributing to sea level rise.

The charts you provided are interesting. It does appear that sea level rise was an order of magnitude more rapid several thousand years ago. I am a little curious about how sea level rise from that period is developed... you seem sufficiently at ease with its accuracy to use it as a comparison, in contrast with the more recent pre-satellite sea levels.

Just razzing you a little, no explanation needed for that. The sea level very likely was increasing more rapidly in the past. That doesn't mean it isn't increasing right now nor that isn't likely to be problematic.

Sea levels several thousand years ago were much lower. Also low lying coastal areas were not so densely populated and the populations that were around were not so dependent on vast commercial agriculture much in flood prone areas.

But even if sea levels had been as high, and population just as dense and food production at risk, ot wouldn't make the prospect of continued sea level rise desirable. There are many previous states the Earth experienced that would be terrible if conditions returned to that in the near future. Late Heavy Bombardment comes to mind.

My point is, merely because a certain metric was th same or worse than current or projected, isn't sufficient to establish that certain metric as acceptable, benign, minimally problematic nor rule it out as an existential threat.

I was using these graphic examples of past natural sea level changes to establish a naturally occurring pattern with which to compare present day projections...The second chart shows mankind existed and flourished during the sea level rise that was certainly more dramatic than anything projected for the future....Just putting things in general context...You seem to be suggesting we are locked in our present geographic locations, on the contrary people are quite mobile....The sort of displacement that you are hinting at, is only dramatic and traumatic when it occurs in a very short period of time, like hurricane Katrina caused...but spread over 100 years, it would not even be noticeable or statistically anomalous...

"... .The second chart shows mankind existed and flourished during the sea level rise that was certainly more dramatic than anything projected for the future..."

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This isn't an apples to apples comparison. The sea level then was much lower. The shoreline was much closer to the continental shelf at the time. Also, the majority of the population was not heavily reliant on commerical agriculture at that time, AFAIK. I suspect that you even though in terms of absolute vertical sea level rise, the predicted sea level change might not be as dramatic, in terms of number of people displaced (perhaps even in percentage of population displaced) and in terms of potential for disruption of food supply and fresh water supply to the population, the future could he fat more dramatic.

Or maybe it doesn't matter. Maybe ice melting en mass off the less dense continental crust and flowing to bear its weight over the more dense sea floor crust will squeeze the Yellowstone caldera like a pimple to induce another supervolcano eruption at Yellowstone, spewing sun blocking aerosols high in the atmosphere and establishing a strong global cooling trend. Self correction at its finest.

Hilariously put. Better than the space rock version.

Speculation your honor!

Pure speculation.

I call for order!

Not to speak of the changes in sea level directly associated with air pressures. Lows pull the sea level up and high pressure flattens the seas somewhat.

Any sensible measurement of sea level should include air pressure corrections. Do satellites measurements have the ability?

...and what about the satellites themselves? The orbit of a satellite in "circular orbit" will never be a perfect circle. That orbit will rise and fall (the distance from orbital center will change) due to the proximity and density of the portion of the Earth that is below the satellite at any given time/location.

Any satellite capable of measuring all the oceans must be in some form of polar orbit, and it is well known that the radius of the Earth is significantly greater near the equator than near the poles, so the height of the satellite above the surface of the Earth (Land or sea) will be constantly changing.

I would concur that atmospheric pressure and winds play a significantly larger role in sea levels than a few millimeter rise...

..."The average sea level during a year is 0 cmPGA and the average air pressure is 1013 hPa. Since the air pressure normally varies between 950 and 1050 hPa during a year, the expected variation in sea level due to air pressure is between +63 cm and -37 cm around mean sea level."....

That's 40 inches of variability from high to low pressures normally occurring during the year....

https://www.smhi.se/en/theme/air-pressure-and-sea-level-1.12266

The flooding in Venice this year is said to be caused primarily by prevailing winds...

Yes wind, which was also a main contributor in the last big flooding.

You seem to be the only one looking for a confrontation...

The man is a geophysicist from Harvard... I would hardly call it a fluff piece.

I suggest you check your fluffometer. Dingos, grumpy cats, and hair stylists turned journalists should be lined up toward the "max fluff" end of the readings - satellites and petri dishes should read near to the bottom.

Jerry Mitrovica is a geologist, but the article is by Daniel Grossman, a journalist. It's about climate change, a political bombshell. It was not peer reviewed by any scientist. You wanted an evaluation by someone grounded in physics, but you can't handle any disagreement from your own biased self.

So get yourself a directional gravometer and sail to Greenland. Start making measurements when 2000 km from the ice sheet. See if it goes up as you get closer to shore. When close to shore see how much change there is if you point it away from Greenland. An alternative is to get someone here to do the calculations. I'll be waiting for the answer (or your retraction).

The article is an interview. The journalist asked the questions. The expert answered, in his own words.

Fluff, on the contrary, is what happens when something scientific is paraphrased or worse, politicized by someone who doesn't really understand the subject, or passes off their uninformed opinions and ad hominem attacks as a well grounded 'evaluation'.

"Fluff, on the contrary, is what happens when something scientific is paraphrased or worse, politicized by someone who doesn't really understand the subject..."

Yep, you got it. Geologists don't work with gravity. There was no math involved. We don't know what he answered and whose opinions are written down. We don't have the transcripts.

On the contrary, geologists most certainly do work with gravity, we were doing gravity surveys as part of our undergraduate work. The tools today are far more accurate than they were then and there is a great deal more data available.

I have mixed emotions on this one. I agree that there can be a huge difference between what a scientist says, what the journalist thought the scientist said, and what ends up in the final article.

Unless the journalist is well versed in the jargon of the interviewee and his/her field of study, there is a high probability of less-than-complete understanding, and that misunderstanding will get passed on to the ultimate reader.

I've done no calculations on this topic, but I too find it difficult to believe that the vertical component of the gravitational attraction between an ice sheet and the surrounding land 2000 km away can have more than a miniscule effect on the distance of the land supporting that ice sheet from the Earth's center. There would be no vertical component if the curvature of the Earth's surface were ignored.

Perhaps I missed it, but I was surprised to see no mention of the lowering of the density of the sea water near the melting ice due to dilution of salt water with fresh water. Less dense water will clearly be lifted up by more dense sea water under and near it; ignoring all other effects, this should make the sea level rise whever the salt content has been lowered.

I decided to run some numbers to see the effect of the Greenland Ice sheet on the ocean level due to gravitational attraction. The ocean level defines a geoid, or a surface of equal gravitational potential, and it is always perpendicular to the force of gravitation.

https://web.viu.ca/earle/geol305/The%20Greenland%20Ice%20Sheet.pdf

The Greenland ice sheet has a volume of 2,900,000 km³, which works out as a mass of 2.9 x 10¹⁸ kg. The dimensions are 1100 km wide by 2400 km long by 2-3 km thick. The nearest ocean is approximately 600 km from the center of the ice sheet.

The technique is to pick a point on the surface of the ocean far from Greenland which we can use as a reference. Moving closer to Greenland, calculate the vertical component (g=9.8 m/sec²) and the horizontal component (a=MG/r²) at each point, where M is the mass of the Ice Sheet in kg, r is the distance in meters, and G is the gravitational constant, 6.67 x 10^-11 m³/kg sec². The slope of the Geoid will be perpendicular to that vector, so the slope is equal to a/g. This is an approximation assuming the distance is small enough to assume the earth is flat.

To be more accurate, the curvature of the earth should be considered. If the angle subtended between the Ice Sheet is Θ, the vector 'a' will be downward by an angle Θ/2, and the true distance will be the chord distance, rd.

Chord distance, rd = (C/pi)*sin(Θ/2), where C is the circumference of the earth.

The direction of the attraction of the Ice Sheet, 'a', is downward by angle Θ/2. For the slope calculation, we can replace 'a' in the numerator by a*cos(Θ/2) and add a*sin(Θ/2) to the denominator:

slope=a*cos(Θ/2) / (g+a*sin(Θ/2))

With a curved earth correction, we can calculate the amount of "gravity bump" due to the Greenland Ice Sheet:

So it appears the maximum "gravity bump" on the closest shore is about 3 cm or about an inch, the amount the ocean level would drop if the ice were gone. It's hard to estimate how much the land would rebound. It seems like a good guess would be that the weight of ice would be replaced by an equivalent weight of rock and soil after some time. The thickness of the ice sheet is 2000 - 3000 meters, so if the average rock density is ~2.5, maybe a rebound of 800 - 1200 meters, eventually. There's no guess how long that would take. But the important factor for people in Greenland would obviously be the difference between land and sea levels.

The area of all the oceans is 362 million km². If the volume of the Greenland Ice Sheet, 2,900,000 km³, were melted, the average ocean level would rise by .008 km or 8 meters.

It seems that the "gravity bump" would be negligible compared with other changes if the Greenland Ice Sheet melted.

I was reading in one of the references that if the entire Greenland ice sheet melted that the remaining geological structure would be that of archipelagos , the land remaining would be represented by the rocky mountainous terrain and the interior would be ocean, so we would have to add that amount of ocean to the total ocean area...granted over time, perhaps hundreds if not thousands, of years, the interior would rebound and the land would surface again, but initially that would not be the case....

Although it doesn't seem likely that the entire ice sheet would melt in any time frame going out several thousand years, that I can see...and it is also possible that at some point this trend would reverse or remain in some equilibrium balance condition....and also that the warming air would also take up more moisture increasing cloud cover and albedo is possible...

"... The nearest ocean is approximately 600 km from the center of the ice sheet. ...."

This point mass approximation throws off your estimate.

To illustrate this, just consider 1/2 the mass you used at just 300 km, and then consider just 1/4 the mass you used at just 150 km.

Greenland is somewhat rectangular so these approximations aren't too far off, but the results calculated won't make sense as the closer fraction of the mass will be shown to have a greater pull than the whole mass if point mass approximation is used when the dimensions of the mass are significant compared to the separation.

This phenomena is also mentioned in the video on quick clay liquefaction....

https://cr4.globalspec.com/thread/131938/The-Importance-of-Salt-in-Quick-Clay-Landscapes

I watched (with considerable interest) that entire video, but don't remember any mention of gravitational attraction to anything other than the standard attraction to the Earth as a whole. AFAIK, there was no mention of attraction to nearby objects, much less to distant objects located roughly the same distance form the center of the Earth.

Can you specify...?

No I was talking about the isostatic rebounding of the Earth. but he does say the sea transgressed in front of the melting ice(1:00 - 2:00) whatever that means...and that these silt deposits left by the retreating glacier can be found up to 200 meters elevation, that's a bit of a rebound I would say....

..." to calculate the gravitational force between two objects with masses of m1 and m2 , the equation is: where G is the gravitational constant (6.67E-11 m3 s-2 kg-1), r is the distance between the two objects, and F is the magnitude of the force between the objects."...

So here's a calculator...

http://www.meracalculator.com/physics/classical/newtons-law-of-gravity.php

"Greenland is isostatically depressed by the Greenland ice sheet such that parts of the bedrock surface in the interior are below sea level."

https://nsidc.org/cryosphere/quickfacts/icesheets.html

Greenland actual size....

Antarctica on the other hand, much larger...

"These images using satellite-derived sea ice concentration data show average minimum and maximum sea ice during March and September for the Arctic and Antarctic from 1979 to 2000. Seasons are opposite between the Southern and Northern Hemispheres; the South reaches its summer minimum in February, while the North reaches its summer minimum in September. (March is shown for both hemispheres for consistency.) The black circles in the center of the Northern Hemisphere images are areas lacking data due to limitations in satellite coverage at the North Pole.

—Credit: National Snow and Ice Data Center, University of Colorado, Boulder, Colorado."

.."Sea ice differs between the Arctic and Antarctic, primarily because of their different geography. The Arctic is a semi-enclosed ocean, almost completely surrounded by land. As a result, the sea ice that forms in the Arctic is not as mobile as sea ice in the Antarctic. Although sea ice moves around the Arctic basin, it tends to stay in the cold Arctic waters. Floes are more prone to converge, or bump into each other, and pile up into thick ridges. These converging floes makes Arctic ice thicker. The presence of ridge ice and its longer life cycle leads to ice that stays frozen longer during the summer melt. So some Arctic sea ice remains through the summer and continues to grow the following autumn. Of the 15 million square kilometers (5.8 million square miles) of sea ice that exist during winter, on average, 7 million square kilometers (2.7 million square miles) remain at the end of the summer melt season."...

..."The Antarctic is almost a geographic opposite of the Arctic, because Antarctica is a land mass surrounded by an ocean. The open ocean allows the forming sea ice to move more freely, resulting in higher drift speeds. However, Antarctic sea ice forms ridges much less often than sea ice in the Arctic. Also, because there is no land boundary to the north, the sea ice is free to float northward into warmer waters where it eventually melts. As a result, almost all of the sea ice that forms during the Antarctic winter melts during the summer. During the winter, up to 18 million square kilometers (6.9 million square miles) of ocean is covered by sea ice, but by the end of summer, only about 3 million square kilometers (1.1 million square miles) of sea ice remain."...

https://nsidc.org/cryosphere/seaice/characteristics/difference.html

"No I was talking about the isostatic rebounding of the Earth. but he does say the sea transgressed in front of the melting ice(1:00 - 2:00) whatever that means...and that these silt deposits left by the retreating glacier can be found up to 200 meters elevation, that's a bit of a rebound I would say...."

Oops, sorry! I misunderstood. Isostatic rebounding clearly will occur, but I suspect the rebound would be at least a couple of orders of magnitude less than 200 meters.

The sea transgressed! I didn't realize that the sea had morals... Surely Neptune will punish the sea!

Those silt deposits sound a lot like glacial moraines, which can occur at several thousand meters above sea level.

It seems that if the sea level is rising from ice melt, that the weight would also be increasing, and this then further depressing the sea bed floor resulting in less height increase than projected from the volume of measured ice melt....

https://en.wikipedia.org/wiki/Isostasy

..."The formation of ice sheets can cause Earth's surface to sink. Conversely, isostatic post-glacial rebound is observed in areas once covered by ice sheets that have now melted, such as around the Baltic Sea and Hudson Bay. As the ice retreats, the load on the lithosphere and asthenosphere is reduced and they rebound back towards their equilibrium levels. In this way, it is possible to find former sea cliffs and associated wave-cut platforms hundreds of metres above present-day sea level. The rebound movements are so slow that the uplift caused by the ending of the last glacial period is still continuing.

In addition to the vertical movement of the land and sea, isostatic adjustment of the Earth also involves horizontal movements. It can cause changes in Earth's gravitational field and rotation rate, polar wander, and earthquakes."...

...."Eustasy is another cause of relative sea level change quite different from isostatic causes. The term eustasy or eustatic refers to changes in the volume of water in the oceans, usually due to global climate change. When Earth's climate cools, a greater proportion of water is stored on land masses in the form of glaciers, snow, etc. This results in falling global sea levels (relative to a stable land mass). The refilling of ocean basins by glacial meltwater at the end of ice ages is an example of eustatic sea level rise.

A second significant cause of eustatic sea level rise is thermal expansion of sea water when Earth's mean temperature increases. Current estimates of global eustatic rise from tide gauge records and satellite altimetry is about +3 mm/a (see 2007 IPCC report). Global sea level is also affected by vertical crustal movements, changes in Earth's rotation rate, large-scale changes in continental margins and changes in the spreading rate of the ocean floor.

When the term relative is used in context with sea level change, the implication is that both eustasy and isostasy are at work, or that the author does not know which cause to invoke.

Post-glacial rebound can also be a cause of rising sea levels. When the sea floor rises, which it continues to do in parts of the northern hemisphere, water is displaced and has to go elsewhere."...

The Atlantic Ocean is also currently expanding at the rate of about 1" a year...geologically...

https://www.quora.com/Is-the-Atlantic-ocean-expanding-If-so-why

...and then there's the sediment to consider, there are many sources of sediment that accumulate on the Ocean floors...

..." There are four basic types of sediment of the sea floor: 1.) "Terrigenous" describes the sediment derived from the materials eroded by rain, rivers, glaciers and that which is blown into the ocean by the wind, such as volcanic ash. 2.) Biogenous material is the sediment made up of the hard parts of sea animals that accumulate on the bottom of the ocean. 3.) Hydrogenous sediment is the dissolved material that precipitates in the ocean when oceanic conditions change, and 4.) cosmogenous sediment comes from extraterrestrial sources. "...

https://en.wikipedia.org/wiki/Seabed

I found a recent paper that looks at Newfoundland. Bearing in mind that the island was covered by glaciers from the last ice age until only about 10,000 years ago, there is plenty of visible evidence of those past changes which has not had time to be worn away by other processes. The paper indicates that crustal rebound is a very significant factor for future sea level, with highly variable effects depending on the local geology.

I believe this is distinct from the effect described in the paper, where the rebound as far away as Greenland is expected to have have an effect, but it is the same basic principle.

http://nlhfrp.ca/wp-content/uploads/2015/01/Past-and-Future-Sea-Level-Change-in-NL...pdf

"Local sea level has also varied over the last 10 000 years because of the last glaciation, where the weight of glacial ice depressed the Earth’s crust beneath it. These changes are by no means uniform over the province (Liverman,1994), with complex patterns of sea-level rise and fall (with sea levels either 10s of metres above or below present from 10 000 to 3000 years ago). Sea-level changes over the last 3000 years were smaller, and resulted from continued crustal rebound.
The approximate rate of local sea-level change over this period is estimated, based on a review of available literature. For a given area then, the suggested sea-level change over the next 50 to 100 years is estimated by summing the estimates of global sea-level change and local sea-level change. "

So if the sea floor is going down as the weight is increased and the surrounding land structures are rising, then sea level rise is mostly a myth...of course the geological structure will cause variances in how much actual movement will occur both with the sea floor and the surrounding land, this together with tectonic and other forces causing local conflicting or cumulative forces resulting in more or less actual observable change to relative shoreline historical perspective...So maybe instead of sea level rise we should call it sea level deepening....In any case not really noticeable to the casual observer...

...except that the average density of rock is between 2.5 and 3 times that of sea water, so for equal areas of land and water, the lifting of the land would only be roughly 1/3 of the increased height of the water. But of course the oceans cover about 70% of the Earth's surface, so on average, the land area is very roughly 1/3 of the ocean area. Thus 3X the density and 1/3 of the area multiply to give the rising land roughly the same mass as the rising sea.

A very interesting coincidence, to have two counteracting 1:3 ratios. This would seem to confirm your personal observation that the shoreline hasn't changed much. As you indicated, local (on several different scales) geology will affect every shoreline, so there will probably be some that move inland, and some that move seaward, and some that essentially remain unchanged, apparently like yours.

According to the above, melting ice will indeed raise the sea level in absolute terms (distance from the center of the Earth), but in the geologic time frame at least, the average sea level relative to the land will change little. I presume that the lifting of the land will be a slower process than the melting of the ice, to there may be a period during which the sea is higher. I have no idea how rapidly the "rafts" will float higher; that period could be a few weeks to a few tens of millennia.

I get the impression that, over millennia, plate tectonics will have a greater effect on local sea levels than melting or freezing ice.

Ice sheets and glaciers only cover around 10% of the land surface area. ...and remember the gravity from those ice sheets and glaciers is drawing the sea level up in the vicinity.

So while the change in sea level in places going from ice covered to not may stay more constant or show decreasing sea level, everywhere not covered in ice currently will experience a greater increase in sea level.

One further exacerbating factor is that continental crust is typically leas dense (and thicker) than sea floor crust.

..."everywhere not covered in ice currently will experience a greater increase in sea level."...

I don't think this is an accurate statement....sea level is a relative term, and is used to measure altitude...You could say, sea water volume increase from melting ice sheets is causing changes in some coastline geography...but it is more of a local phenomena than a general one, because in some cases it is causing apparent recession and in some places, probably most, no change at all....

If you would read the comment for comprehension and consider context, instead of just picking out the part that suggests sea level will increase (and railing against it), you would see that this comment is talking about the effects in relation to rebound of the crust and where that is likely to occur.

If the average temperature of the oceans increases and the net amount of ice supported by the Earth's crust is reduced, there should be an increase in volume, no?

How do you arrive at the conclusion that most places will see no increase in sea level at all?

Previously you were arguing that previous sea level increase corresponded with a time that humans flourished, if you believe it will be a positive effect, why also chose to support this other highly improbably idea that either sea temperatures are not increasing on average and net ice supported by crust (vice floating in an ocean) is not decreasing, or that even with an increase in volume, some offset will make it as if there was no increase at all?

I try to keep a neutral stance and remain open to ideas I don't ascribe to at the moment, your post is definitely making that more challenging.

My thinking is that the added weight of water to the sea will cause a subsequent rise in the surrounding land masses...generally speaking...If you increase the sea water volume and elevate the surrounding land mass, the relative sea level could remain the same, depending on local geographic densities and mass...

Your proposal only makes sense if the continental landmass and the submerged continental shelf were floating independently on the liquid magma layer, they are not. Even if a fault line lies between two crustal plates at a beach, the forces between these two plates will mean vertical motion will only happen in the brief tectonic jolts of an earthquake.

Geologic motion happens at a timescale many orders of magnitude greater than any body of water.

I would think the gravitation deformation caused by the Moon would accelerate the process, a few mm's a year should be possible...

"... the added weight of water to the sea will cause a subsequent rise in the surrounding land masses.. ..."

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Okay, I see where you are coming from. I didn't understand your reasoning and it seemed like you were just shouting down anything that suggested sea level rise. My bad.

I agree that there will be rebound in the crust and some slight depression in the sea floor. There is an initial elastic rebound that is rapid, but the remainder of the rebound is very slow,, taking tens of thousands of years as I understand it.

Also, the rebound occurs where weight of water previously depress the crust. Those areas may indeed shoot up, but this doesn't mean the places people live will.

From this map, it looks like most of the populated world is pretty close to maintaining current elevation with the exceptions of most of the US is descending slowly, the Mediterranean is descending a little more slowly, and part of Great Britain and most of Scandinavia is shooting up.

Well most of the US is in the green, which means it's rising relative to sea level...Up around the Canadian border it looks static with some spots sinking relative to sea level...

..."But the rebound of the Earth is not the only complicating factor when we try to measure how much sea level is rising. When meltwater is added to the oceans, sea level doesn’t rise by the same amount everywhere; in some places it rises by more than the average amount, and in others it rises by less. The reason for this variation is gravity.

Now, the distribution of mass throughout the Earth is not uniform, so the pull of gravity is not the same everywhere. Therefore, the geoid, or sea surface, doesn’t follow the outline of a perfect sphere; it bulges downwards where the interior of the Earth is very dense, and it bulges upwards where there is a large mass on the surface of the Earth, such as an ice sheet (Figure 4)."...

http://www.antarcticglaciers.org/glaciers-and-climate/sea-level-rise-2/recovering-from-an-ice-age/

It seems the crustal levels are falling around the coastal regions...

https://earthscience.stackexchange.com/questions/4728/why-is-relative-sea-level-falling-in-hudson-bay/6685

You might be a little color blind. Maybe your screen colors are misleading.

Luckily there is no need to rely on the color comparison. This is after all a standard contour map with the zero line emphasized.

See the darker lines with values? Find the lines with a zero value. There is one encircling South America. There is one encircling Canada. Stuff on one side of those lines is moving up, on the other side moving down. Find the next darker line. That value will (except for very rare special circumstances) indicate the direction of the gradient.

In the case of North America, everything north (Canada) of that line is ascending, and everything south (USA) is descending.

Rest assured that there is no ridge holding exactly at zero rise and zero fall with both sides either falling or rising together....i.e. nature is not going to set things up to fool anyone looking at a contour line

Then the crustal level of the ocean is falling as well....?

Yes. As expected with water moving off the continental crust and moving into the ocean supported by the sea floor crust, the sea floor crust should be depressed slightly under the increased load.

The granite under the Scottish city of Aberdeen bends and flexes when the tide comes in and goes out, according to a hypersensitive instrument installed at the University in that town.

The net difference in elevation between the Pacific side of the Panama canal, and the Atlantic side, is about 8 inches (~ 20 cm). So no, the net sea level is not equally level, from North Pole to south Pole.

This is significantly due to salt water being insufficiently viscous for seawater to maintain a consistent average level equal at both ends of said canal. As the planet rotates from west to east, the Pacific Coast (pushes) sea water around the southern tip of South America too slowly to keep the net elevation of the Atlantic side as high as the net elevation of the Pacific side. Even though the water levels are connected, Fluid water can not quite keep up with western side of south American land mass, due to the Earth's rotation. That elevation difference is continually evident via the Panama Canal. Plans to deepen (and widen) said canal are to hande wider and deeper ship drafts, and not to handle sea level rises. Since it took six years to do the 2011-2018 ''widenning'' of the Canal, the Panama Canal Authority would be making plans to raise the height, and/or further lower the the bottom, of the locks even more... Is that actually happenning?... The Panama Canal is an intrinsically big ''gage'' to track net Sea Level changes. What is it ''telling'' us so far?...

MR. Guest, there are numerous misconceptions presented as fact in your comment

"... due to salt water being insufficiently viscous for seawater to maintain a consistent average level equal at both ends.."

How would viscosity being too low lead to a failure to communicate average level between connected bodies of water? No need to answer, because it wouldn't. Excessive viscosity might, but that isn't the case here either.

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"... As the planet rotates from west to east, the Pacific Coast (pushes) sea water around the southern tip of South America too slowly to keep the net elevation of the Atlantic side as high as the net elevation of the Pacific side. ..."

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Again, how exactly?

If you move a paddle in a still (Earth surface reference) body of water with typical paddling speed from west to east, it would be truly strange to see water building up on the west face of the paddle and depleted on the east face.

Moreover, in an Earth surface reference South America is not acting like a paddle traveling from west to east. It is fairly immobile, only moving very slowly but from east to west actually. If on the other hand you are using some inertial frame of reference, why? What ethereal force do you imagine is trying to keep the water from turning with the planet that would create the pushing your describe even if it were in the correct direction?

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"... the Panama Canal Authority would be making plans to raise the height, and/or further lower the the bottom, of the locks even more ..."

Okay, slightly different this time...Why exactly?

You wouldn't need to raise the height of the locks. The locks are there to raise and lower the ships, increasing sea level just makes that feat a little smaller.

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"... What is it ''telling'' us so far?..."

Well, not much, but to its credit, that at least means it isn't spreading disinformation.

It isn't telling us much because it isn't actually

".... an intrinsically big ''gage'' to track net Sea Level changes. ..."

and respectably, to my knowledge it has never claimed to be such.

If the earth did not rotate essentially from west to east, then, relative to the Earth, how else would the Sun rise in the east, and set in the west?...

The problem is not with your claim about the direction of rotation.

The problems are with your statements related to fluid dynamics, mostly.

If you have to visualise the Pacific Coast as a (paddle), then give it fair credit for being several thousand miles long...

".... give it fair credit for being several thousand miles long...."

Are you suggesting the problem is one of scale?!? Perhaps you could elucidate as to the minimum scale necessary for a paddle so that it would begin showing the odd phenomena you describe of water piling up on the front of the paddle as it is moved back through still water.

Do you really mean to say that the several-thousand-mile-long length of the Pacific Coast can not be viewed as as the same several-thousand-mile-long breadth of a ''paddle''?...

Nope.

Whatever length paddle you have, when you force it broadside (as is typical) through still water, the water does not pile up on the side your are moving away from nor become depleted on the side toward which you are moving.

Your inability to understand this simple concept is beginning to be concerning. Are you experiencing any other symptoms? Pins and needles? Dizziness? Trouble seeing out of one or both eyes? And odd smells, such as that of burning hair? Are you having trouble speaking? Is it more difficult to use one of your hands?

You can lead a horse to water, but you can't make it WANT to drink when it gets there...

I think your paddle analogy has some modest merit but your description of why the Pacific Ocean is nominally higher than the Atlantic Ocean, at the Panama Canal is circumspect. I suspect the global West to East prevailing winds blow the Pacific Ocean water higher. These prevailing winds are partly manifestations of the Earth's rotation.

Sorry, I meant this to be a reponse to Post #81.

Go to the equivalent of a Flat-bottomed sink, run enough water to cover the botton to a depth of, say, a quarter-inch thick, get a standard flat sponge, and slowly wipe the bottom, while maintaining contact with only one edge of the sink.The water in front of the sponge will temporarily rise, slightly, and the water level in back of it will lower, slightly, until the sponge stops being moved.

Ideally, if the sink was an endless sink around the entire earth, and the sponge was moved a constant rate, forever, the elevation difference would also remain, unchanged, forever, other variables held constant

If the fluid is changed to a significantly more viscous maple syrip, then the speed of the sponge was the same as with the water, the elevation difference would be greater, because of the greater viscosity. (I.e.: the maple syrip could not ''get out of its' own way'' as fast as could sea water)

But, sea water is much less viscous than maple syrip, and its' resultant elevation difference is ''watery'' enough to come into a constant, stable, but unbalanced equilibrium, much more quickly, and would remain equal, until the speed of the sponge is changed. (i.e.: /\y_front(v) - /\y_back(v) = a constant elevation difference)

Herein, the net causes have been extremely simplified.

Notice in your example this time the fluid builds up INFRONT of the sponge/paddle/continent. That was a major problem with your original explanation and it remains a problem for explaining how water on the 'back' (Pacific side) would be higher than on the front (Atlantic side).

Remember the motion is from West to East meaning the front of the sponge/paddle/continent is the Eastern side, so your description would have that as higher, but it is not

I don't believe anyone is questioning the direction of rotation of the Earth. Some of us, including yours truly, are questioning which forces contribute to the inequalities of absolute and relative sea levels, especially with regard to the Panama Canal.

One of these forces is due to Coriolis effects, both directly on flowing water (eg. the Humboldt current) and on the atmosphere above it.

I posted this before seeing post #50...

I am not questioning the details of the forces acting on the sea level.

What I am saying is that the elevation-difference between the Paciic, and the Atlantic, ends of the Panama Canal is a directly measurable result of the net (i.e.: sum-total-of-all) forces acting on the net sea levels at those Canal ends...

"I am not questioning the details of the forces acting on the sea level."

That's NOT what your post #33 indicates:

"This is significantly due to salt water being insufficiently viscous for seawater to maintain a consistent average level equal at both ends of said canal. As the planet rotates from west to east, the Pacific Coast (pushes) sea water around the southern tip of South America too slowly to keep the net elevation of the Atlantic side as high as the net elevation of the Pacific side."

In fact, unless I am greatly mistaken, if the viscosity of seawater were higher, it would flow more slowly, and thus result in a greater difference in levels between the two ends of the canal.

Your last paragraph is clearly correct. The causes of that difference in elevation are highly debatable.

The primary Alaska-California current in the North Pacific flows clockwise, until turning directly West, away from Guatemala.

The Primary Chile-Peru current in the South Pacific flows counter-clockwise, until also turning directly west, away from Columbia.

Sandwiched in between those two westerly flows is an easterly counter-current directed straight towards Panama.

So, my ''paddle'' turns out to be only a few hundred miles wide.

So, yes, DKWarner, your Post #51 is correct

Thanks! So all three major flows are towards the west coat of Panama. This would logically raise the level of the water on the west side of Panama.

I suspect that the Gulf of Mexico isolates the east side of Panama from the flows along the east coasts of N & S America, to some degree.

...and a hearty thank you!

This is a contributing factor to the difference in level...

...and exactly how much percentage does salinity raise (or lower) the sea level?...

... and why?...

Sea water with different salinity has a different density. So for the same (but less extreme) reason that a millimeter of mercury can be equivalent to a little over 1/2 an inch of water in a manometer, higher salinity (higher density) sea water in a connected system will tend to have a lower level than lower salinity sea water in that connected system.

Differences in salinity drive some of the largest oceanic currents.

To.calculate close to the exact difference in level would take some information I don't have readily available and time I am not interested in spending. I do have the info and time to point you in the right direction if interested.

The map shows around a 2.6 ppt difference (with absolute values either side of the typical for seawater value of 34.5 ppt). Which is significant, especially considering the depths involved.

For every 1000 units of depth a column of water with 2.6 ppt less salinity than in a column to which it is connected will be 2.6 units higher in static equilibrium.

Would not the relative "driving" salinity-related (force?) be governed by the net-relative-salinity-percentage-difference, and not just the net-total salinity of the sea water?

Yes, of course. I didn't mean to imply otherwise.

...and, just exactly how does a relative-salinity-difference actually cause even a small ocean current?...

One example is the high salinity of the Gulfstream current after it has taken its northern route and been depleted of a significant amount of water through evaporation. The high salinity of the Gulfstream relative to the surrounding waters causes it to sink, driving it down forming the current that will traverse the Atlantic from that to the nothern point a great distance south before surfacing again.

At least that's my understanding.

There is a name for it, so it should be easy to research further; thermohaline circulation.

...but how does the (relatively warm?) (seawater?) gulfstream (acquire) enough of such a saline component as to be able to (impose?) a downward current on an otherwise horizontally stable seawater current?...

It has been losing heat all the way up to evaporation, convection, conduction and radiation.

...but those are not due primarily to the saline-content of the sea water...

"... are not due primarily to the saline-content of the sea water...."

Um, sure. Heat loss to the environment is not driven by salinity in a significant way in ocean currents AFAIK. What exactly if your point? Why would you expect that or perceive that I was suggesting or intending to convey that?

On a different note, since 'saline', as a noun, means a solution of salt in water, the phrase 'saline content' is best reserved for significantly nonhomogeneous substances wherein saline might be a distinct constituent of the substance not found essentially throughout but in discrete non-it areas; such as for describing sea ice having some saline inclusions or describing a mist or fog coming on shore.

IMHO, sea water being a saline solution does not benefit from a description of 'saline content', any more that an orange might benefit from a description of its 'citrus content'.

Thermohaline circulation, also referred to the ocean conveyor belt, goes up the asian coast of the Paciic Ocean, turns clockwise down the middle of the northern Pacific Ocean, and goes nowhere near the Panama Canal...

As such, how does it contribute at all to sea levels adjacent to the Pacific end of the Panama Canal?...

It seems a lot more temperature-, wind-, and tide-driven than saline-driven...

There is a strong pattern in your comments , at least on this topic, in which you call into question some general process as it relates to a specific event, then when clarification is provided about the general phenomena, you ask more specifically about an example provided in that clarification. Then in what seems like you are attempting to spring some sort of 'gotcha-trap', you ask about how one the example given illustrating the general process could possibly be involved with the original specific event being discussed.

The answer is, of course, it isn't to a meaningful degree, but you already know this.

The ocean conveyor belt probably doesn't have much effect on the difference in sea level of the different sides of the Panama canal. Then again, no one was making that claim here.

The path went something like this:.

I said, differences in salinity likely play a large role.

You queried about how salinity could possibly have any effect.

I explained that salinity differences were also density differences and attempting to show that salinity differences were significant to ocean dynamics, gave an example of the ocean conveyor belt being a large eff at at least partially driven by salinity differences.

You seemed in incredulous and wanted an explanation of how the warm gulf stream could sink.

I provided my ideas on how that was possible.

...

This brings us to your comment previous to this; the one to which I am responding, in which yiou disput a claim that was never made. No one is saying thermohaline circulation is responsible for the sea level mismatch across the panama canal. Thermohaline circulation was used as an example of how significant effects of variations in salinity can be. It was an example to help you get away from your outright dismissal of the effects of salinity differences as having too little effect to be able to cause variations in sea level.

I realize I came down hard on your comment early in this discussion when you likened South America to a paddle being pushed (either the wrong direction for rotation or having water build up on the wrong side for said motion) through the ocean and an lack of viscosity being the reason for the difference in sea level. In all fairness, that comment deserved every bit of what was said and more.

Here's the thing., I was coming down hard on your comment, not on you. It wasn't about you, until you insisted repeatedly in making it about you. All you have yo do to free yourself from it is just that:. admit it is wrong, that you no longer ascribe to the flawed perspective and move on.

The more you invest in setting 'gotcha-traps' and seeking revenge for someone daring to point out the folly of that comment, the more you become vested in that comment....the more you become exactly as absurd and wrong as the comment.

Let it go

The ''salt'' in salt water was originally grains of sand. Sand typically has densities from 112 pcf, to 125 pcf, all over the entire ocean. Being an amount about twice as dense aa sea water of about 63.5 pcf. Thus, (sea salt) will necessarily ''fall'' to the ocean bottom. unless the ocean current is strong enough to push it along more horizontally, than vertically.

The ocean curent is not primariy being pushed along by by salinity conentration diffences, but is drivem primarily by polar thermal drops, and mixed by surface winds and tides, and various cross-currenrts.

WRONG! Salt (sodium chloride) is totally soluble in water. There are many kinds of sand, none of which are soluble in water.

In order for the salt in sea water to form crystals, the vast majority of the water must be removed, as is commonly done by sunlight evaporation in the many places where salt is harvested from seawater.

The salt in seawater is in solution; the higher the salt concentration, the higher the density of that solution. Higher density always causes a more dense solution to sink under a less dense solution, and that sinking solution must continue sinking until it reaches the bottom or a region of even more dense solution. At that point it will spread out and/or flow elsewhere. Clearly differential density is not the only source of forces causing flow, but it definitely does contribute.

".... The ''salt'' in salt water was originally grains of sand. ...."

Where are you getting this garbage? Seriously, did you just think it sounded good and so that it must be true, or did you know it wasn't true and either thought no one else would notice or you actually get some pleasure out of being utterly wrong in a public forum?

Table salt might look a little like beach sand, but that is where the similarity ends. Sand is mostly silicon dioxide and salt is mostly sodium chloride. Notice not even any shared elements.

Furthermore, salt does not fall out if not stirred. If it did, then holding tanks would be an effective way to desalinate.

Please stop with your absurd assertions. The things you are saying are cringe worthy.

Pouring a little table salt into enough water will dissolve the salt grains into Na⁺ and Cl^- ions, not salt grains...

Is that supposed to be a correction? Of what exactly? Where did anyone write 'salt grains'?

How does that statement pertain to the thread at all? You aren't making sense.

If the NaCL dissolves in the water, then what but sand grains can be left, undisolved, in the water?...

"what but sand grains can be left, undisolved,[sic] in the water?..."

LOTS of things, including a whole lot of byproducts from human activity, mostly plastic, and billions of organisms, from plankton to fish, whales, sea lions, etc.

On the other hand, depending on your interpretation of "in the water", the things I mentioned and your sand grains aren't IN the water, although they are partially or completely surrounded by the water.

If you ask a scientist to determine the contents of a properly collected sample of seawater, he/she won't find any grains of sand. He/she WILL find lots of other things, mostly ions of many elements and compounds, even including gold.

"... then what but sand grains can be left, undisolved, in the water?..."

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Turbidity is one answer. Another could be TSS (Total Suspended Solids).

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You asked a question. I provided an answer. You may or may not agree. Your question was not ignored. You may not think the answer acceptable, but the answer is at least there for you to evaluate and critique if you chose.

See how that worked? Perhaps you could return the favor and answer my question, instead of flatly ignoring it and asking another of your own.

My previous question still stands:

'What is your point?'

Total Suspended Solids are the organic contents of untreated water, in a Water treatment facility, that are beginning to break down and starting to decay...

Ocean turbidity is due to organic matter continuing to decay...

TSS is not limited to just water treatment plants.

Additionally TSS and turbidity are completely legitimate answers to the question you posed of what else is left undissolved.

I don't agree with your attempt to limit TSS and turbidity to only organic material, but really, who cares if it is organic in this instance? Your question did not specify such.

Now, once again, I will point out that you have you continue to ask these ancillary questions and then proceed with what has the feeling of an attempt (much lacking) to critique the answers you receive, yet, you have failed to answer th most basic and pertinent question in return.

....and that question is:. 'what is your point?'

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My suspicion that this is a reaction to the irrationality and counterfactual nature of your early comment being pointed out, seems warranted.

''Organics'' do not have ''grains'' ...

Once again, what is your point?