Why is sea level rise worse in some places?(nautil.us)
nautil.us
Why is sea level rise worse in some places?
https://nautil.us/why-is-sea-level-rise-worse-in-some-places-294325/
140 comments
> Most notably, I can't find an example in the NOAA data of the rate of sea level rise increasing due to industrialization. Anybody?
You can look at the graph on the NOAA site here and see the acceleration visually: https://www.climate.gov/news-features/understanding-climate/...
The notes to the left of the table say 1.4mm/yr for much of 20th Century to 3.6mm/yr now.
There is also evidence of acceleration of sea level rise just from satellite data, 0.08mm/y^2:
https://www.sciencedaily.com/releases/2018/02/180212150739.h...
You can look at the graph on the NOAA site here and see the acceleration visually: https://www.climate.gov/news-features/understanding-climate/...
The notes to the left of the table say 1.4mm/yr for much of 20th Century to 3.6mm/yr now.
There is also evidence of acceleration of sea level rise just from satellite data, 0.08mm/y^2:
https://www.sciencedaily.com/releases/2018/02/180212150739.h...
Back in 2006, our expectations were set when An Inconveient Truth contemplated what would happen if sea levels rose by six meters (in our lifetime). 3.6mm a year seems a bit meh in that context.
Something I see a lot is people looking at worst case predictions as if they were presented as the most likely predictions. A lot of the IPCC reports say things like “if we continue to increase emissions, this will happen” (a worst case scenario) and also “if we make moderate improvements, this will happen” (a slightly better scenario). Then people who don’t want to talk about climate change mitigation will highlight the worst case scenario and say “see they were wrong and hysterical!” even when the moderate prediction, which they will ignore, ended up being essentially totally accurate.
Well, I'll go a step further and say that 3.6mm/yr is not evidence of a crisis.
that's not a problem in the decade timeline but it is problematic over a century or two. it's especially problematic since it's accelerating and has a couple decades of inertia. the CO2 we release today will raise sea levels for the next 50 years or so.
>that's not a problem in the decade timeline but it is problematic over a century or two.
So after roughly 100 years, we can look forward to the terrible catastrophe of sea levels (in some places only, not in others) rising by.. just over a foot. A problem for many really flat coastal areas, sure, but hardly the picture of global coastal flooding much of the alarmism has put forward. And if that one-foot rise happens across a full century, there will be many measures that can be taken to counter it even if the rise itself is unstoppable.
I'm not arguing against human-caused climate change, but some of the hyperbole i've seen said with deep certainty goes well beyond the scope of known evidence, realized events or even many scientific assessments.
With such things, it's not hard to see why some people find good reasons for being skeptical of yet another worst-case prediction.
So after roughly 100 years, we can look forward to the terrible catastrophe of sea levels (in some places only, not in others) rising by.. just over a foot. A problem for many really flat coastal areas, sure, but hardly the picture of global coastal flooding much of the alarmism has put forward. And if that one-foot rise happens across a full century, there will be many measures that can be taken to counter it even if the rise itself is unstoppable.
I'm not arguing against human-caused climate change, but some of the hyperbole i've seen said with deep certainty goes well beyond the scope of known evidence, realized events or even many scientific assessments.
With such things, it's not hard to see why some people find good reasons for being skeptical of yet another worst-case prediction.
Isn't that relative sea level changes in places like Scandinavia - the sea isn't dropping, the land is rising?
https://en.wikipedia.org/wiki/Relative_sea_level
https://en.wikipedia.org/wiki/Relative_sea_level
Exactly.
Because the sensors are mounted on that very land.
So tectonic movement will certainly have an effect. And you can see remnants of earthquakes in some of the data.
Because the sensors are mounted on that very land.
So tectonic movement will certainly have an effect. And you can see remnants of earthquakes in some of the data.
In Scandinavia, isn't it glacial rebound rather than tectonic?
> 3. (geology) Of, relating to, or caused by large-scale movements of the Earth's (or a similar planet's) lithosphere
- https://en.wiktionary.org/wiki/tectonic
- https://en.wiktionary.org/wiki/tectonic
I expect the parent is referring to human-caused melting of glaciers as the root cause of that tectonic movement, rather than the expected natural motion of the tectonic plates.
It's the glaciers melting at the end of the last Ice Age that Scandinavia is still rising from.
https://en.wikipedia.org/wiki/Last_Glacial_Period#Weichselia...
> As a result of melting ice, the land has continued to rise yearly in Scandinavia, mostly in northern Sweden and Finland, where the land is rising at a rate of as much as 8–9 mm per year, or 1 m in 100 years. This is important for archaeologists, since a site that was coastal in the Nordic Stone Age now is inland and can be dated by its relative distance from the present shore.
https://en.wikipedia.org/wiki/Last_Glacial_Period#Weichselia...
> As a result of melting ice, the land has continued to rise yearly in Scandinavia, mostly in northern Sweden and Finland, where the land is rising at a rate of as much as 8–9 mm per year, or 1 m in 100 years. This is important for archaeologists, since a site that was coastal in the Nordic Stone Age now is inland and can be dated by its relative distance from the present shore.
Yeah, the sea must be "level" in some sense across the planet.
Don't know if local variations in gravity may have a measurable impact?
Don't know if local variations in gravity may have a measurable impact?
PDF of gravitational correction factors by geographical region for use in theoretical weighscale calibration (vs calibrating with actual test weights): https://hardyinst.custhelp.com/app/answers/detail/a_id/1588/...
The melting of glaciers themselves can have an impact on gravity, causing water levels to drop around them. https://www.theguardian.com/environment/ng-interactive/2018/...
The absolute value of gravity is (to oversimplify) the sea-level datum for current generation datums, like the delayed NGS (nominal year) 2022 datums.
They've (NGS) been flying absolute gravity measurement equipment in planes with precision GPS and lidar since ~2005 as part of the GRAV-D program.
Additionally, slight 'variations' (ie deviations from the expected circular/elliptical) in the orbits of GPS satellites can be used to infer slight variations in the gravity below.
Separately, the military likely has had all of this measured and modeled for decades as part of ballistic missile targeting, but remains mostly classified at useful resolutions.
The transitions from NGVD27 to NAVD88 to the work-in-progress 22 datum is exactly because the idea of a simple "universal" sea-level doesn't exist in the manor you would expect it to.
But even with the GRAV-D based datums, the actual observed water levels will occur at slightly different datum heights in different locations, for various geophysical reasons.
They've (NGS) been flying absolute gravity measurement equipment in planes with precision GPS and lidar since ~2005 as part of the GRAV-D program.
Additionally, slight 'variations' (ie deviations from the expected circular/elliptical) in the orbits of GPS satellites can be used to infer slight variations in the gravity below.
Separately, the military likely has had all of this measured and modeled for decades as part of ballistic missile targeting, but remains mostly classified at useful resolutions.
The transitions from NGVD27 to NAVD88 to the work-in-progress 22 datum is exactly because the idea of a simple "universal" sea-level doesn't exist in the manor you would expect it to.
But even with the GRAV-D based datums, the actual observed water levels will occur at slightly different datum heights in different locations, for various geophysical reasons.
[deleted]
> East coast US seems to be going up about 3mm/year, or a foot per century. That's on top of 7 foot tides.
That's the average rise it you average all data going back to the 1950s.
Unfortunately, looking back to the 50s is only really useful if interested in how much sea levels have already risen. Otherwise it presents an unrealistically optimistic view, as the rate has accelerated since.
Per the article, the east coast (North Carolina) is currently experiencing an increase of about a third of an inch per year, which is an increase of one foot per 36 years, or close to a meter per century.
If current trends continue, this will accelerate, not decelerate.
That's the average rise it you average all data going back to the 1950s.
Unfortunately, looking back to the 50s is only really useful if interested in how much sea levels have already risen. Otherwise it presents an unrealistically optimistic view, as the rate has accelerated since.
Per the article, the east coast (North Carolina) is currently experiencing an increase of about a third of an inch per year, which is an increase of one foot per 36 years, or close to a meter per century.
If current trends continue, this will accelerate, not decelerate.
Your unit mixtures hurt my brain
What I wonder about is: rising wrt. what? Did they take into the account the possibly vertical movement of tectonic plates?
They do take that into account. They calculate that the ocean floor is sinking but then ADD that displacement to their reported measurement of "sea level", which is backwards. When the ocean floor sinks sea level goes down, but they report it as going up instead, using this justification:
https://sealevel.colorado.edu/index.php/presentation/what-gl...
currently some land surfaces are rising and some ocean bottoms are falling relative to the center of the Earth (the center of the reference frame of the satellite altimeter).
since the ocean basins are getting larger due to GIA, this will reduce by a very small amount the relative sea level rise that is seen along the coasts.
We apply a correction for GIA because we want our sea level time series to reflect purely oceanographic phenomena. In essence, we would like our GMSL time series to be a proxy for ocean water volume changes. This is what is needed for comparisons to global climate models, for example
This is nonsense, of course. Volume isn't measured in millimeters, that's a measurement of distance. GMSL when talking about satellites is defined as the average distance of the surface of the ocean from the center of the Earth, and the reason people care about it is because if it gets too high then things we care about end up flooded. Changing the definition of GMSL half way through from sea level to sea depth is the kind of slippyness that pervades this space.
https://sealevel.colorado.edu/index.php/presentation/what-gl...
currently some land surfaces are rising and some ocean bottoms are falling relative to the center of the Earth (the center of the reference frame of the satellite altimeter).
since the ocean basins are getting larger due to GIA, this will reduce by a very small amount the relative sea level rise that is seen along the coasts.
We apply a correction for GIA because we want our sea level time series to reflect purely oceanographic phenomena. In essence, we would like our GMSL time series to be a proxy for ocean water volume changes. This is what is needed for comparisons to global climate models, for example
This is nonsense, of course. Volume isn't measured in millimeters, that's a measurement of distance. GMSL when talking about satellites is defined as the average distance of the surface of the ocean from the center of the Earth, and the reason people care about it is because if it gets too high then things we care about end up flooded. Changing the definition of GMSL half way through from sea level to sea depth is the kind of slippyness that pervades this space.
I think the arctic region is affected by glacial rebound: the ground slowly recovers from past glacial compression.
Subsidence is a thing in Silicon Valley. San Jose has sunk some feet since the aquifer was drawn, fist for agriculture and now urbanization.
Subsidence is a thing in Silicon Valley. San Jose has sunk some feet since the aquifer was drawn, fist for agriculture and now urbanization.
There is only one reason the sea can rise currently due to weather and that is glaciers getting melted.
Another reason (but not due to weather) is that when land somewhere goes up, it will displace water everywhere else. And so, for example, if the land is still recovering from the ice age we should see ocean levels going up everywhere except for the pieces of land that are recovering from the weight of the glacier that is no longer there.
Mind that Arctic is not causing sea level rise. Any ice that is floating on water will not cause any water level change when it melts. (I know this is somewhat unintuitive but it comes directly from Archimedes principle)
So we are talking basically Antarctic ice and Greenland because these are by far the largest bodies of frozen water that are supported by land rather than floating on the ocean.
I think it should be pretty easy to observe how much of that water melted or slipped into the sea.
I also think that currently, coastal erosion is mostly caused by changing weather patterns. Basically this comes down to wind blowing in different directions, speed and variety and these changing patterns mean coasts are eroding in different places than before.
Another reason (but not due to weather) is that when land somewhere goes up, it will displace water everywhere else. And so, for example, if the land is still recovering from the ice age we should see ocean levels going up everywhere except for the pieces of land that are recovering from the weight of the glacier that is no longer there.
Mind that Arctic is not causing sea level rise. Any ice that is floating on water will not cause any water level change when it melts. (I know this is somewhat unintuitive but it comes directly from Archimedes principle)
So we are talking basically Antarctic ice and Greenland because these are by far the largest bodies of frozen water that are supported by land rather than floating on the ocean.
I think it should be pretty easy to observe how much of that water melted or slipped into the sea.
I also think that currently, coastal erosion is mostly caused by changing weather patterns. Basically this comes down to wind blowing in different directions, speed and variety and these changing patterns mean coasts are eroding in different places than before.
Also, warming oceans causes expansion which causes sea level rise.
https://www.jpl.nasa.gov/edu/learn/project/how-warming-water....
https://www.jpl.nasa.gov/edu/learn/project/how-warming-water....
Not true.
First of all, most of the temperature rise only happening close to the surface with average surface temperature rise being only about 1.5F or 1C since 1901.
This article says deep ocean water is projected to warm up by only 0.2C during next 50 years: https://www.openaccessgovernment.org/deep-ocean-warming-subt...
Furthermore, at around 4C which is what deep ocean water is close to (everything below 200m is essentially 4C), thermal expansion is almost nil. For colder water thermal expansion is actually negative.
4C is when water is at its densest. It is not an accident that all oceans are 4C, because 4C water sinks to the bottom and anything colder or hotter than 4C floats up. This remarkable property of water is what causes even shallow water to be fantastically stable in temperature -- a lake that has more than couple tens of meters in depth is likely to be 4C at the bottom throughout the year whether it is frosty winter or hot summer above it, unless some kind of powerful event is able to mix the water in the lake.
Now, the small temperature differences will definitely have outsize effects on water circulation, ocean currents, life and weather. But I doubt they will cause meaningful sea rise unless somebody can calculate otherwise?
First of all, most of the temperature rise only happening close to the surface with average surface temperature rise being only about 1.5F or 1C since 1901.
This article says deep ocean water is projected to warm up by only 0.2C during next 50 years: https://www.openaccessgovernment.org/deep-ocean-warming-subt...
Furthermore, at around 4C which is what deep ocean water is close to (everything below 200m is essentially 4C), thermal expansion is almost nil. For colder water thermal expansion is actually negative.
4C is when water is at its densest. It is not an accident that all oceans are 4C, because 4C water sinks to the bottom and anything colder or hotter than 4C floats up. This remarkable property of water is what causes even shallow water to be fantastically stable in temperature -- a lake that has more than couple tens of meters in depth is likely to be 4C at the bottom throughout the year whether it is frosty winter or hot summer above it, unless some kind of powerful event is able to mix the water in the lake.
Now, the small temperature differences will definitely have outsize effects on water circulation, ocean currents, life and weather. But I doubt they will cause meaningful sea rise unless somebody can calculate otherwise?
That’s mostly accurate, but the nuances are significant and lead to different conclusions. For example the hypolimnion may be much warmer than 4C in lakes in warmer areas. More importantly tropical ocean water is above 4C down to roughly 2km and not only is that depth expected to increase, but also the depth of warm water as you go north. https://en.wikipedia.org/wiki/Thermocline
The important thing to remember is even a 1 part in 1,000 decrease in density * 2km of depth = 2m of expansion. Ballpark estimates aren’t enough you really need fairly detailed simulations to get any significant accuracy. Actually doing such simulations shows meaningful sea level rise from thermal expansion at ~0.07 inches per year or roughly half the current rate of increase. This might not sound like much, but consider that volume of sand you need to replace to maintain beaches etc etc.
The important thing to remember is even a 1 part in 1,000 decrease in density * 2km of depth = 2m of expansion. Ballpark estimates aren’t enough you really need fairly detailed simulations to get any significant accuracy. Actually doing such simulations shows meaningful sea level rise from thermal expansion at ~0.07 inches per year or roughly half the current rate of increase. This might not sound like much, but consider that volume of sand you need to replace to maintain beaches etc etc.
> That’s mostly accurate
No, that is mostly inaccurate. Thermal expansion is small, but there is an awful lot of water. As you point out yourself, thermal expansion contributes about half the sea level rise. Oceans absorb energy just like the atmosphere does and this effect has been known for quite a while (e.g. https://www.nature.com/articles/330127a0 ).
No, that is mostly inaccurate. Thermal expansion is small, but there is an awful lot of water. As you point out yourself, thermal expansion contributes about half the sea level rise. Oceans absorb energy just like the atmosphere does and this effect has been known for quite a while (e.g. https://www.nature.com/articles/330127a0 ).
The average ocean surface temperature is about 20°C and the thermal expansion coefficient is 0.000207/°C (https://www.engineeringtoolbox.com/water-density-specific-we...). If I have my google-fu and math right, that's about 1cm/° for a 50m deep water column.
Thermal expansion of surface water is not negligible.
Thermal expansion of surface water is not negligible.
> But I doubt they will cause meaningful sea rise unless somebody can calculate otherwise?
Plenty of people have, in fact, calculated otherwise.
Roughly half of the current, ongoing sea level rise is from expansion of water. The effect is small, but there is a lot of water that is expanding.
Plenty of people have, in fact, calculated otherwise.
Roughly half of the current, ongoing sea level rise is from expansion of water. The effect is small, but there is a lot of water that is expanding.
[deleted]
Fascinating; thanks.
Question: How does the salinity and pressure of deep sea water affect that 4C point?
Question: How does the salinity and pressure of deep sea water affect that 4C point?
Not necessarily. The density of water peaks around 4ºC. So as oceans warm between 0º and 4º, they actually contract in volume.
Except water in oceans is at 4C (at least almost everything deeper than ca 200m). And in the vicinity of 4C the thermal expansion is very negligible. This graph should explain why: https://images.app.goo.gl/FXzvTkPvE9dYxoUA7
Which supports the broader point that thermal expansion of water does not contribute to rising sea levels.
Umm. I’m pretty sure if water that exists above the water line is melted into the water line, the overall water line will rise. You can directly observe this in a glass of ice that starts with no liquid water will melt into a glass of liquid water.
I could be wrong about this (it's been awhile since I took chemistry), but I think the ice has to be floating for the Archimedes principle to apply.
You can fill a glass of ice-water right up to the brim, and it won't spill over as the ice melts. But only if the ice is floating in the water. It's because the ice's mass pushes down on the liquid water, displacing a fixed amount relative to the weight of the ice.
You can fill a glass of ice-water right up to the brim, and it won't spill over as the ice melts. But only if the ice is floating in the water. It's because the ice's mass pushes down on the liquid water, displacing a fixed amount relative to the weight of the ice.
Ah. I missed the “floating” part. That makes sense.
This is untrue.
Ice is about 91% the density of water. If you have water at 0 height, and you put in water equivalent to +1 unit of height. If it's in liquid form, obviously height goes up by +1. If it's in ice form, there is +1.09 height worth of ice (because it expands when it freezes), but it only displaces water up to +1 unit of height in order to support its weight through buoyancy. The overall change in height is +1 unit regardless of whether it's liquid or ice
Ice is about 91% the density of water. If you have water at 0 height, and you put in water equivalent to +1 unit of height. If it's in liquid form, obviously height goes up by +1. If it's in ice form, there is +1.09 height worth of ice (because it expands when it freezes), but it only displaces water up to +1 unit of height in order to support its weight through buoyancy. The overall change in height is +1 unit regardless of whether it's liquid or ice
No, it's not just due to weather (you probably mean climate anyway). For example, ice melting in one place, say Antarctica, will affect sea levels elsewhere on the planet because of weaker gravitational forces where the ice used to be. Geoscience is complex and measuring changes on such a global scale is not "pretty easy", even if it's only sea level changes. It's nothing like a bathtub or elementary school physics.
Not to rant but this is one of those threads again. The majority of comments contain misinformation.
Not to rant but this is one of those threads again. The majority of comments contain misinformation.
We shouldn't be calling subsidence sea level rise. They are two distinct, measurable, phenomena that happen to have the same impact.
I don't think it was possible to measure them separately until we had good satellite data from the last two decades. If we're extending trends back to the beginning of the industrial revolution, they're going to be mixed.
Satellite data isn't that good unfortunately. Tide gauges say 1.5mm/year of rise, satellites say 3mm/yr, and they estimate satellite error to be +/- 0.5mm year, so the error bars are a significant fraction of the size of the overall change.
Also that assumes the scientists are completely accurate and don't make any mistakes. As recently as 5 years ago they discovered that the measured rise for almost all of the 90s was wrong and revised it by 3mm/year +- 1.7mm/year - the error was the same amount as the imputed level of rise!
This is no knock on the scientists, because measuring the height of a moving ocean from orbit to a level of accuracy that lets you see mm level changes is inevitably going to be very hard. But we should bear in mind that they're heavily biased towards wanting to believe the data is accurate. Their decade long inability to get the measurements correct didn't seem to have any impact on their confidence that they're currently getting it right, and why would it? Those who seize the data, seize the day.
Also that assumes the scientists are completely accurate and don't make any mistakes. As recently as 5 years ago they discovered that the measured rise for almost all of the 90s was wrong and revised it by 3mm/year +- 1.7mm/year - the error was the same amount as the imputed level of rise!
This is no knock on the scientists, because measuring the height of a moving ocean from orbit to a level of accuracy that lets you see mm level changes is inevitably going to be very hard. But we should bear in mind that they're heavily biased towards wanting to believe the data is accurate. Their decade long inability to get the measurements correct didn't seem to have any impact on their confidence that they're currently getting it right, and why would it? Those who seize the data, seize the day.
> Also that assumes the scientists are completely accurate and don't make any mistakes. As recently as 5 years ago they discovered that the measured rise for almost all of the 90s was wrong and revised it by 3mm/year +- 1.7mm/year - the error was the same amount as the imputed level of rise!
Citation for this? There are always improvements to our understanding of past data, but you seem to be implying that the uncertainty exceeds the signal. That's simply not the case [1].
[1] — https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6... pp.1291-1292
Citation for this? There are always improvements to our understanding of past data, but you seem to be implying that the uncertainty exceeds the signal. That's simply not the case [1].
[1] — https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6... pp.1291-1292
Ablain, "Uncertainty in Satellite estimate of Global Mean Sea Level
changes, trend and acceleration", p4
They have shown that there was a drift in the GMSL record over the period 1993-1998. This drift is caused by an erroneous on-board calibration correction on TOPEX altimeter side-A (noted TOPEX-A). TOPEX-A was operated from launch in October 1992 to the end of January 1999. Then TOPEX side-B altimeter (noted TOPEX-B) took over in February 1999 (Beckley et al., 2017). The impact on the GMSL changes is -1.0 mm/yr between January 1993 and July 1995, 120 and +3.0 mm/yr between August 1995 and February 1999, with an uncertainty of ±1.7 mm/yr (within a 90%CL, (Ablain, 2017)).
They have shown that there was a drift in the GMSL record over the period 1993-1998. This drift is caused by an erroneous on-board calibration correction on TOPEX altimeter side-A (noted TOPEX-A). TOPEX-A was operated from launch in October 1992 to the end of January 1999. Then TOPEX side-B altimeter (noted TOPEX-B) took over in February 1999 (Beckley et al., 2017). The impact on the GMSL changes is -1.0 mm/yr between January 1993 and July 1995, 120 and +3.0 mm/yr between August 1995 and February 1999, with an uncertainty of ±1.7 mm/yr (within a 90%CL, (Ablain, 2017)).
Figure 1 from that paper didn't convince you that it was a minor issue? Their correction is about 7% of the 1993-2018 signal, and it resolves the discrepancy with respect to other estimates, including non-satellite ones. Nobody relies on estimates from a single satellite alone.
https://essd.copernicus.org/articles/11/1189/2019/essd-11-11...
https://essd.copernicus.org/articles/11/1189/2019/essd-11-11...
The thread is at max depth, so I'll reply here:
As you quoted from the paper:
> The six main groups that provide satellite-altimetry-based GMSL estimates ...
1) You're restricting your attention to groups producing satellite-derived estimates.
2) Several of those groups, e.g. CSIRO, are using data assimilation to combine satellite estimates with gauges [1].
3) There are multiple satellites, often overlapping in time, often of totally different design/orbit/etc... [2]
4) Up to the most recent IPCC report (AR6), assessments were based on tide gauges alone [3]. For many of the reasons that you bring up. Hence "Nobody relies on estimates from a single satellite alone." Reconstruction of historical sea level is a huge scientific discipline and you would benefit from doing some more reading before beating a dead horse. The estimated uncertainty is large for a reason, but it does not encapsulate any scenarios where the observed change has been insignificant. If you think otherwise, I'd be happy to take your money for 2100 options on coastal real estate in about 90% of the world's coastline.
[1] — https://research.csiro.au/slrwavescoast/sea-level/measuremen... and https://link.springer.com/article/10.1007/s10712-011-9119-1
[2] — https://research.csiro.au/slrwavescoast/sea-level/measuremen...
[3] — https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6... p.1287
As you quoted from the paper:
> The six main groups that provide satellite-altimetry-based GMSL estimates ...
1) You're restricting your attention to groups producing satellite-derived estimates.
2) Several of those groups, e.g. CSIRO, are using data assimilation to combine satellite estimates with gauges [1].
3) There are multiple satellites, often overlapping in time, often of totally different design/orbit/etc... [2]
4) Up to the most recent IPCC report (AR6), assessments were based on tide gauges alone [3]. For many of the reasons that you bring up. Hence "Nobody relies on estimates from a single satellite alone." Reconstruction of historical sea level is a huge scientific discipline and you would benefit from doing some more reading before beating a dead horse. The estimated uncertainty is large for a reason, but it does not encapsulate any scenarios where the observed change has been insignificant. If you think otherwise, I'd be happy to take your money for 2100 options on coastal real estate in about 90% of the world's coastline.
[1] — https://research.csiro.au/slrwavescoast/sea-level/measuremen... and https://link.springer.com/article/10.1007/s10712-011-9119-1
[2] — https://research.csiro.au/slrwavescoast/sea-level/measuremen...
[3] — https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6... p.1287
We've gone from:
- Uncertainty exceeding signal in satellite data is "simply not the case"
to
- OK maybe it was the case but it doesn't matter and nobody relies on one satellite anyway
to
- OK maybe some groups relied on one satellite but this is flogging a dead horse everyone already knows about
That's a big distance in a short thread! Also, note that you said "nobody relies" and now you're arguing "not everyone relies", which is different.
I won't be alive in 2100 but if you've got some nice seafront property you'd like to sell me below market price I'd definitely consider it. Maybe in Tuvalu? (see other post).
- Uncertainty exceeding signal in satellite data is "simply not the case"
to
- OK maybe it was the case but it doesn't matter and nobody relies on one satellite anyway
to
- OK maybe some groups relied on one satellite but this is flogging a dead horse everyone already knows about
That's a big distance in a short thread! Also, note that you said "nobody relies" and now you're arguing "not everyone relies", which is different.
I won't be alive in 2100 but if you've got some nice seafront property you'd like to sell me below market price I'd definitely consider it. Maybe in Tuvalu? (see other post).
> We've gone from: - Uncertainty exceeding signal in satellite data is "simply not the case" ...
Not sure I can help someone who willfully misreads my comments! Give chapter 9 of the AR6 a read and then we can talk.
Not sure I can help someone who willfully misreads my comments! Give chapter 9 of the AR6 a read and then we can talk.
>> Nobody relies on estimates from a single satellite alone.
Yes they did. From the paper I just cited:
The six main groups that provide satellite-altimetry-based GMSL estimates (AVISO/CNES, SL_cci/ESA, University of Colorado, CSIRO, NASA/GSFC, NOAA) use 1 Hz altimetry measurements from the T/P, Jason-1, Jason-2 and Jason-3 missions from 1993 to 2018 (1993–2015 for SL_cci/ESA). The differences among the GMSL estimates from several groups arise from data editing, from differences in the geophysical corrections and from differences in the used method to spatially average individual measurements during the orbital cycles
The apparently independent time series are actually computed from the same raw data sources, as there isn't an abundance of redundant satellites measuring sea level.
But isn't this goalpost shifting? At first you said I was wrong that uncertainty has been the same size as the measurements in the past, citing the IPCC as proof which of course doesn't mention any of this, saying only that they have high confidence in these numbers (the IPCC is not trustworthy). Then it became that the error isn't big enough for you, and nobody relied on a single satellite. Now I show that they did indeed rely on a single satellite.
The core issue here remains the same: how do they know they're getting it right now? A calibration error so large it invalidated their entire time-series lasted for the entire lifetime of the TOPEX-1 mission, and it then took 20 years for the problem to actually be detected and corrected for. They've only been measuring sea level with satellites for 30 years, and the discrepancy between tide gauges and satellites has never been properly reconciled even though they theoretically measure the same thing.
Yes they did. From the paper I just cited:
The six main groups that provide satellite-altimetry-based GMSL estimates (AVISO/CNES, SL_cci/ESA, University of Colorado, CSIRO, NASA/GSFC, NOAA) use 1 Hz altimetry measurements from the T/P, Jason-1, Jason-2 and Jason-3 missions from 1993 to 2018 (1993–2015 for SL_cci/ESA). The differences among the GMSL estimates from several groups arise from data editing, from differences in the geophysical corrections and from differences in the used method to spatially average individual measurements during the orbital cycles
The apparently independent time series are actually computed from the same raw data sources, as there isn't an abundance of redundant satellites measuring sea level.
But isn't this goalpost shifting? At first you said I was wrong that uncertainty has been the same size as the measurements in the past, citing the IPCC as proof which of course doesn't mention any of this, saying only that they have high confidence in these numbers (the IPCC is not trustworthy). Then it became that the error isn't big enough for you, and nobody relied on a single satellite. Now I show that they did indeed rely on a single satellite.
The core issue here remains the same: how do they know they're getting it right now? A calibration error so large it invalidated their entire time-series lasted for the entire lifetime of the TOPEX-1 mission, and it then took 20 years for the problem to actually be detected and corrected for. They've only been measuring sea level with satellites for 30 years, and the discrepancy between tide gauges and satellites has never been properly reconciled even though they theoretically measure the same thing.
revelio(2)
There are other factors, too. I remember reading about sea level change as a result of Greenland's ice melting. The sea level around Greenland is actually predicted to go down. One reason is that the ice is pushing the land down, and that effect will reverse as the ice melts. The other surprising reason is that the ice is massive enough to have a noticeable gravitational effect on the surrounding water.
https://www.theguardian.com/environment/ng-interactive/2018/...
https://www.theguardian.com/environment/ng-interactive/2018/...
Fun random factoid, big parts of Europe are still slowly rising because the weight of ice compressed a lot of it.
On the other side, a lot of land is sinking because the soil is drying out due to years of droughts and water mismanagement (farmers like to keep the water table lower. I live in NL where we have the water management infrastructure to tweak the water table)
On the other side, a lot of land is sinking because the soil is drying out due to years of droughts and water mismanagement (farmers like to keep the water table lower. I live in NL where we have the water management infrastructure to tweak the water table)
Same thing happened in Vermont with some of the evidence for it being whale skeletons found in fields hundreds of miles from the ocean:
https://en.wikipedia.org/wiki/Charlotte_whale
> On the other side, a lot of land is sinking because the soil is drying out due to years of droughts and water mismanagement...
Shockingly fast, too, in some spots.
https://www.nytimes.com/2021/05/25/us/corcoran-california-si...
"Over the past 14 years, the town has sunk as much as 11.5 feet in some places..."
Shockingly fast, too, in some spots.
https://www.nytimes.com/2021/05/25/us/corcoran-california-si...
"Over the past 14 years, the town has sunk as much as 11.5 feet in some places..."
Post glacial rebound:
https://en.wikipedia.org/wiki/Post-glacial_rebound
https://en.wikipedia.org/wiki/Post-glacial_rebound
When the soil is drying out, it will start to float. Im from Boskoop in NL, we have that problem with peat soil (veen grond). This is also irreversible, when peat soil gets dried it will not become wet again.
This is literally two of the three things the article talks about.
Seems we are missing "Land level rise" and "Land level fall". Those will be more patchy and local than sea level.
That's exactly what TFA is explaining.
Yeah, and that's good locally, but globally we see a rise overall.
It's wild how locally variable the sea level surface is. I worked on a study that incorporated local sea levels into a bath-tub style sea level rise model that that also incorporated storm surge using ADCIRC modeling, and we tried to account for local land subsidence and uplift rates... anyways.
If you look at the "NOAA Tides and Currents" data, and go to Maryland, and click two points across the Chesapeake bay from each other. Go to More Data > Datum, you can see just across a 20 mile stretch of bay, Bishops Head MD MHHW (Mean Higher High Water, when there are two daily high tides, this is the elevation of the higher of the two) is 2.06 Feet over the vertical datum, while 20 miles away at Solomons Island MD it's a half foot lower, 1.48 Ft.
If you look at the "NOAA Tides and Currents" data, and go to Maryland, and click two points across the Chesapeake bay from each other. Go to More Data > Datum, you can see just across a 20 mile stretch of bay, Bishops Head MD MHHW (Mean Higher High Water, when there are two daily high tides, this is the elevation of the higher of the two) is 2.06 Feet over the vertical datum, while 20 miles away at Solomons Island MD it's a half foot lower, 1.48 Ft.
On a smaller body of water is that mostly wind?
[deleted]
Seeing a lot of people talk about how the density of water is going to change with a temperature change. I don't really think that's true. Liquid water density is pretty darn inelastic and almost fully incompressible. It's one of the reasons hydraulics works. Ice on the other hand has a pretty different density.
Water density table - https://www.usgs.gov/special-topics/water-science-school/sci...
If the temperature of the ocean changed by 10°F that would result in a .1% change in overall volume. Obviously that does make a difference because the ocean is so big, but it's a lot less consequential than ice, which is above the water, melting into the water and ice.
Water density table - https://www.usgs.gov/special-topics/water-science-school/sci...
If the temperature of the ocean changed by 10°F that would result in a .1% change in overall volume. Obviously that does make a difference because the ocean is so big, but it's a lot less consequential than ice, which is above the water, melting into the water and ice.
But if the ice is floating, it should displace the same volume of water that it will melt into.
It's amazing how many people don't understand this. It displaces the same amount of water whether it is frozen and floating or melted. Easily tested by filling a glass with water and adding an ice cube and then drawing a line at the water level and letting the ice melt. The water level will be the same.
Of course, if the ice is on land and melting into the ocean, that's different.
Of course, if the ice is on land and melting into the ocean, that's different.
Oh hey, what about the difference in density between fresh water and salt water?
https://nsidc.org/news-analyses/news-stories/melting-floatin...
https://nsidc.org/news-analyses/news-stories/melting-floatin...
Kind of a nitpick but glaciers are made of less dense fresh water compared to the salt water of the ocean. So melting glaciers will slightly increase sea levels.
> If we look at the global picture, there are two major reasons why sea levels are rising. One is that the ocean is warming, and it needs more space and expands.
My understanding is that water expands quite a bit less in the range between 32°F and 212°F than it does when it freezes.
It seems like floating ice melting and decreasing in volume 9% is notably more significant than the volume increase from a couple degree temperature increase. There also certainly way more liquid water than solid to contend with.
I'd be curious to know the effect of melting ice decreasing the volume versus the temperature rising increasing the volume.
My understanding is that water expands quite a bit less in the range between 32°F and 212°F than it does when it freezes.
It seems like floating ice melting and decreasing in volume 9% is notably more significant than the volume increase from a couple degree temperature increase. There also certainly way more liquid water than solid to contend with.
I'd be curious to know the effect of melting ice decreasing the volume versus the temperature rising increasing the volume.
Archimedes would like a word. There are some small effects due mostly to salinity differences, but sea ice isn't a major contributor because it is already floating and thus displacing an equivalent volume of water:
https://en.wikipedia.org/wiki/Sea_level_rise#cite_ref-113
https://en.wikipedia.org/wiki/Sea_level_rise#cite_ref-113
Sea ice also reflects light. Remove the ice and the water beneath heats up.
That's part of the runaway effect we are freaked out about.
That's part of the runaway effect we are freaked out about.
I have two related questions:
1. Global temperature is rising. Any water that used to be above 4°C (or the equivalent for salt water) now takes more volume. But what about water that's below 4°C? Wouldn't that water compress? What portion of the ocean is colder than 4°C? I'd imagine all of the Arctic zone and near Antarctica is, which is an awful lot of water to offset the tropical water. An even more nuanced perspective would be to look at the actual temperature distribution and use it to weight the dV/dT of water at different temperatures.
2. Global temperature is rising. Ice is melting into water. This is new mass entering the ocean. Why can't the sea bed, which is under more pressure due to extra mass, expand? The sea bed isn't a steel utensil, it's sand and rocks. And it's constantly shifting. And it's composition is different in different regions.
Has anyone done a detailed computer simulation of the whole earth's geology under rising temperatures? There might be feedback loops that might amplify or negate some effects so it's quite important to account for all variables. And obviously there's a lot of variables to account for.
(It's sometimes scary how little we know about our own planet. I'm not talking about the things in my comment because I'm sure it's just my ignorance.)
1. Global temperature is rising. Any water that used to be above 4°C (or the equivalent for salt water) now takes more volume. But what about water that's below 4°C? Wouldn't that water compress? What portion of the ocean is colder than 4°C? I'd imagine all of the Arctic zone and near Antarctica is, which is an awful lot of water to offset the tropical water. An even more nuanced perspective would be to look at the actual temperature distribution and use it to weight the dV/dT of water at different temperatures.
2. Global temperature is rising. Ice is melting into water. This is new mass entering the ocean. Why can't the sea bed, which is under more pressure due to extra mass, expand? The sea bed isn't a steel utensil, it's sand and rocks. And it's constantly shifting. And it's composition is different in different regions.
Has anyone done a detailed computer simulation of the whole earth's geology under rising temperatures? There might be feedback loops that might amplify or negate some effects so it's quite important to account for all variables. And obviously there's a lot of variables to account for.
(It's sometimes scary how little we know about our own planet. I'm not talking about the things in my comment because I'm sure it's just my ignorance.)
> 1. Global temperature is rising. Any water that used to be above 4°C (or the equivalent for salt water) now takes more volume. But what about water that's below 4°C? Wouldn't that water compress?
It might marginally, but the amount of water compressed will be a lot smaller than the amount of water "uncompressed", both due to the larger range of temperatures above 4°C (below is only a bit, and then ice) and due to the fact that the densest water is at the bottom, meaning that it's easier for everything else to heat up.
> 2. Global temperature is rising. Ice is melting into water. This is new mass entering the ocean. Why can't the sea bed, which is under more pressure due to extra mass, expand?
Expand where? It can't just rise since there is gravity, and the pressure above increases with more water. It can't go down because there is already other stuff there.
It might marginally, but the amount of water compressed will be a lot smaller than the amount of water "uncompressed", both due to the larger range of temperatures above 4°C (below is only a bit, and then ice) and due to the fact that the densest water is at the bottom, meaning that it's easier for everything else to heat up.
> 2. Global temperature is rising. Ice is melting into water. This is new mass entering the ocean. Why can't the sea bed, which is under more pressure due to extra mass, expand?
Expand where? It can't just rise since there is gravity, and the pressure above increases with more water. It can't go down because there is already other stuff there.
In regard to that last point, I hadn't thought of it but there is something called post-glacial rebound, it would make sense that the increased weight on the seabed would deform it, and potentially even cause bulging of land without ocean on top, potentially negating the sea level rise effect to varying degrees worldwide.
>Expand where?
Think of the ocean bed as a trampoline. Obviously much more rigid, but that's the image in my head.
>It can't go down because there is already other stuff there.
Why not? Rocks and sand can be compressed with sufficient pressure.
Think of the ocean bed as a trampoline. Obviously much more rigid, but that's the image in my head.
>It can't go down because there is already other stuff there.
Why not? Rocks and sand can be compressed with sufficient pressure.
> Wouldn't that water compress?
You say it because of the extra volume on top of it?
If that's the case, not because of heating. The volume increases, the water still weights the same.
You say it because of the extra volume on top of it?
If that's the case, not because of heating. The volume increases, the water still weights the same.
No, water is most dense at 4°C. If you take water at 2°C and increase its temperature by a degree, it will _compress_, not expand. But if you take water at 10°C and heat it by a degree it will expand. My question is what percentage of the expansion is offset by the compression.
(Note that the 4°C number is only for pure water.)
> water still weights the same
Weight has nothing to do with my first point. It's the increase in volume that spills into land.
(Note that the 4°C number is only for pure water.)
> water still weights the same
Weight has nothing to do with my first point. It's the increase in volume that spills into land.
Yeah, my comment was stupidly about how some other phenomenon doesn't exist.
But well, water being water, I imagine this doesn't happen at pressure; just for surface water. Is that the case?
But well, water being water, I imagine this doesn't happen at pressure; just for surface water. Is that the case?
Reminder that Ice takes up more volume than water.
I know, did I say otherwise anywhere?
the key point is that there is very little water below 4 Celsius because it would rise into warmer water and heat up.
Are the Qattara Depression project and similar proposals too small in impact or more expensive than building better flood management, or why aren't we doing those?
Much too small. Using Wikipedia's figures: volume of Qattara Depression = 1,213 cubic kilometres, volume of Greenland ice sheet = 2,850,000 cubic kilometres. And the project is only useful as a long-term power source if the contents evaporate leaving space for renewed inflow, i.e. it only sequesters a fraction of its volume.
Making Qattara a bay of the Mediterranean would be great as a way to bring life and human habitation to the desert.
It's incredibly expensive though.
Scott Alexander estimated it would "reverse one year worth of global-warming induced sea-level rise" here: https://slatestarcodex.com/2016/04/15/links-416-they-cant-li...
It's incredibly expensive though.
Scott Alexander estimated it would "reverse one year worth of global-warming induced sea-level rise" here: https://slatestarcodex.com/2016/04/15/links-416-they-cant-li...
There are 360 million square kilometers of ocean. Of course sea level rise increases the surface area a bit but if you assume 1 mm (1 millionth of a kilometer) goes straight up then each mm of sealevel is 360 cubic kilometers of water.
We are depleting our aquifers at a rate of about 280 km^3 per year. US is down over 1000 km^3 since ~1900. I'm not sure how much of that ends up in the ocean, but reducing that number and taking it negative would go a long way toward slowing sea level rise.
We are depleting our aquifers at a rate of about 280 km^3 per year. US is down over 1000 km^3 since ~1900. I'm not sure how much of that ends up in the ocean, but reducing that number and taking it negative would go a long way toward slowing sea level rise.
The comment above says filling Qattara takes 1,213 cubic kilometres, which would mean about 3mm lower sea level. Which would be a real change, but also quite small in the bigger picture.
I guess depleting aquifers can lower land levels in those areas. I hear Jakarta has sunk 4 meters from that effect. But it's a separate thing from rising sea levels.
I guess depleting aquifers can lower land levels in those areas. I hear Jakarta has sunk 4 meters from that effect. But it's a separate thing from rising sea levels.
I was thinking more of the fact that if it’s not below ground it’s above ground, so most of that water has been evaporated and deposited into the ocean.
> One is that the ocean is warming, and it needs more space and expands.
That doesn’t sound right. I think it is common knowledge that water expands as it freezes (hence, burst pipes), not when it warms up.
That doesn’t sound right. I think it is common knowledge that water expands as it freezes (hence, burst pipes), not when it warms up.
Water density is almost fully inelastic w/rt temperature. At 60°F the density is 0.99907 g/cm^3, at 100°F the density is 0.99318 g/cm^3. I think that's something like a .5-1% change in density. Pipes bursting is purely because of the drastic density change from ice crystallization.
https://www.usgs.gov/special-topics/water-science-school/sci...
https://www.usgs.gov/special-topics/water-science-school/sci...
No expert, but here's what I found, because I was curious too.
Ice in water doesn't change the waters height. If you put an ice cube in a cup, the water will be the same height after the ice has melted [1], since the "excess" is lifted out of the water. For some numbers, in 2020, it looks like total sea ice peaked at 18,785 km3, with the oceans volume being 130,000,000, so 0.014% [2].
The thermal expansion of water, as liquid form, is going to be much more important [3].
Related, every time I try to look into climate numbers, I get the sense that there's a gap between grade school explanations and research papers. There's not much between. Asking ChatGPT just reinforces this view. It treats me like a kid, or wraps unsolicited disclaimers/summaries around everything.
1. https://physics.stackexchange.com/questions/110645/why-does-...
2. https://arctic.noaa.gov/Report-Card/Report-Card-2020/ArtMID/...
3 https://physics.stackexchange.com/questions/506759/how-much-...
Ice in water doesn't change the waters height. If you put an ice cube in a cup, the water will be the same height after the ice has melted [1], since the "excess" is lifted out of the water. For some numbers, in 2020, it looks like total sea ice peaked at 18,785 km3, with the oceans volume being 130,000,000, so 0.014% [2].
The thermal expansion of water, as liquid form, is going to be much more important [3].
Related, every time I try to look into climate numbers, I get the sense that there's a gap between grade school explanations and research papers. There's not much between. Asking ChatGPT just reinforces this view. It treats me like a kid, or wraps unsolicited disclaimers/summaries around everything.
1. https://physics.stackexchange.com/questions/110645/why-does-...
2. https://arctic.noaa.gov/Report-Card/Report-Card-2020/ArtMID/...
3 https://physics.stackexchange.com/questions/506759/how-much-...
The thermal expansion coefficient of water:
https://www.engineeringtoolbox.com/water-density-specific-we...
Water is at its most dense around 4 degrees C. As the temperature increases from there it gets less dense.
That's just a quirk of ice, that it's lower density than water. Liquid water still does what most (all?) liquids do wrt temperature changes.
Because in the long term the world does not act like a glass of water: there are currents and gravity.
[deleted]
The affect of sea level rise on the Bay of Fundy is going to be... interesting.
(Largest tides on the planet. The bay acts as a kind of resonant organ pipe amplifying the tides on the Atlantic Ocean.)
Hey; if they can handle 52ft tides, they can handle anything.
Hey; if they can handle 52ft tides, they can handle anything.
I just looked up The Bay of Fundy on Google maps, having not heard of it before. I'm interested, can you explain what about this particular bay will make it interesting?
Highest tidal range on the planet.
https://en.wikipedia.org/wiki/Bay_of_Fundy
https://en.wikipedia.org/wiki/Bay_of_Fundy
Yes, and it is always COLD. (Newly engaged I took my fiancée to a beach west of Saint John and decided to go for a swim. I mean, I should have known better, I grew up there. It was a shallow slope, so by the time it was deep enough to dive in, I couldn’t feel my ankles. It was a short swim. It’s not like I was going to wimp out and turn back in front of my sweetie. Ah, the pride of youth.)
Re the tides: when Charles ame Diana visited NB in 1983, they disembarked at high tide in the Saint John harbour. The gangplank was at about 45 degrees, slopes down to the dock. A few hours later, it was 45 degrees down to the royal yacht. Some of the sailors, many of whom had long experience, having served in the falklands, among other places, had never seen anything like it.
Re the tides: when Charles ame Diana visited NB in 1983, they disembarked at high tide in the Saint John harbour. The gangplank was at about 45 degrees, slopes down to the dock. A few hours later, it was 45 degrees down to the royal yacht. Some of the sailors, many of whom had long experience, having served in the falklands, among other places, had never seen anything like it.
Interestingly there can be similarly large tides in the UK, the Severn Estuary has a range of around 50' too.
True, true. But imagine those tides in a slightly larger bay: 52km wide at the entrance (compared with ~14km for Severn), mostly linear (48km near its neck, compared with ~2km) and over 155km long.
The amount of water that comes in an out twice a day is, well, nuts. Yes, that's the technical term.
(Summer ferry crossings between Digby Neck and Saint John are 2.5 hours, 3.0 hours in the winter (slower due to rougher water), but I do know people who took ~12 one February: the water was so rough they hugged as close to the shores of NB and NS as they dared, just to make things a little calmer. There have also been cases of transport trailers falling over in the hold. Yes, they were lashed down.)
(I once spent a terrible several hours sprawled on a lounge chair staring out the window on the opposite side of the boat: For seven seconds I could see nothing but sea, the ship swung, and for seven more, nothing but sky. Repeat. Ad nauseam. The swings took about a second. When I finally did get up to head to the heads to unload that nausea, let's just say planning was involved in every step.)
(Another trip, I also spent an uncomfortable few minutes on the observation deck bow-ward of that lounge, because young and dumb: It was fall, I was heading back to Uni, it was cold (duh), I was wearing a hoodie and shorts, and I'd stepped out for fresh air. Got talking to American tourists in long slacks and sweaters. Felt expansive and loquacious, kept them out there as long as I could. They finally excused themselves on account of the cold, very polite, and I turned to and leaned upon the bow rail until I felt enough time had gone by that I could return to the lounge. Man, it was cold. Ah, youth. :->)
The amount of water that comes in an out twice a day is, well, nuts. Yes, that's the technical term.
(Summer ferry crossings between Digby Neck and Saint John are 2.5 hours, 3.0 hours in the winter (slower due to rougher water), but I do know people who took ~12 one February: the water was so rough they hugged as close to the shores of NB and NS as they dared, just to make things a little calmer. There have also been cases of transport trailers falling over in the hold. Yes, they were lashed down.)
(I once spent a terrible several hours sprawled on a lounge chair staring out the window on the opposite side of the boat: For seven seconds I could see nothing but sea, the ship swung, and for seven more, nothing but sky. Repeat. Ad nauseam. The swings took about a second. When I finally did get up to head to the heads to unload that nausea, let's just say planning was involved in every step.)
(Another trip, I also spent an uncomfortable few minutes on the observation deck bow-ward of that lounge, because young and dumb: It was fall, I was heading back to Uni, it was cold (duh), I was wearing a hoodie and shorts, and I'd stepped out for fresh air. Got talking to American tourists in long slacks and sweaters. Felt expansive and loquacious, kept them out there as long as I could. They finally excused themselves on account of the cold, very polite, and I turned to and leaned upon the bow rail until I felt enough time had gone by that I could return to the lounge. Man, it was cold. Ah, youth. :->)
Yes. I've seen its tides in person. It's almost unreal. Boats go from sitting on their sides on dry land to floating in 3+m of water and back every tidal cycle.
At first I was thinking that that doesn't sound all that unusual; here near Antwerp, Belgium we also have tides high enough that small boats can go from sitting dry to floating clear. But then I looked it up and it turns out that the tidal range in the Bay of Fundy is about 16 metres (52 feet)! That really is a lot, and much more than the about 5.5 metres we have here.
There's even a waterfall that reverses direction based on the tides!
Reversing Falls: https://en.wikipedia.org/wiki/Reversing_Falls
Also mentioned by Tom Scott: https://www.youtube.com/watch?v=nCrTsWtPVIY
Also mentioned by Tom Scott: https://www.youtube.com/watch?v=nCrTsWtPVIY
Tom Scott at the Bay of Fundy: https://www.youtube.com/watch?v=nCrTsWtPVIY
This article only briefly touches on what I think is the most interesting aspect of sea level rise: gravitational adjustment. Even though I never worked seriously on sea level research, it was by far my favorite course in graduate school. For anyone who would like to learn more, I highly recommend listening to Jerry Mitrovica expound on the subject [1]. I guarantee that you will learn a few things that will stick with you.
In my experience, the first order adjustment effects are not widely known even among physical oceanographers. I remember describing it to a preeminent expert on El Nino, and him being incredulous that local sea level fall near the source of meltwater could be the first-order effect beyond accounting for rebound. "The first-order response is a Kelvin wave — you've surely been misinformed."
[1] - One example lecture: https://www.youtube.com/watch?v=s_rGksRoG9A
[2] - Another, shorter summary talk https://www.youtube.com/watch?v=yj7JIxU9Af4
In my experience, the first order adjustment effects are not widely known even among physical oceanographers. I remember describing it to a preeminent expert on El Nino, and him being incredulous that local sea level fall near the source of meltwater could be the first-order effect beyond accounting for rebound. "The first-order response is a Kelvin wave — you've surely been misinformed."
[1] - One example lecture: https://www.youtube.com/watch?v=s_rGksRoG9A
[2] - Another, shorter summary talk https://www.youtube.com/watch?v=yj7JIxU9Af4
Great, now we need to raise taxes to stop tectonic plates.
The Netherlands is also sinking so you get a double whammy.
Because overall it has not risen at all?
It's risen ~97mm since 1993. The rate of increase in that rise has been increasing steadily since ~1993. The consistency of our data has also been much better since then (previously it was only the highly noisy coastal tide gauge data).
Fun fact: the slowest its been in the last century was when we did a crap-ton of dam projects in the 50s-70s, still rose, but very little.
Fun fact: the slowest its been in the last century was when we did a crap-ton of dam projects in the 50s-70s, still rose, but very little.
For that to be true there would be plenty of places where it's falling. Are there?
there absolutely are, a google away https://tidesandcurrents.noaa.gov/sltrends/
But they are generally rising, just not more than compared with pre-industrial era.
But they are generally rising, just not more than compared with pre-industrial era.
I mean, "plenty" isn't really true based on that link.
A best you could say "a few, in areas that are losing glaciers, which is expected due to basic physics"
A best you could say "a few, in areas that are losing glaciers, which is expected due to basic physics"
That map clearly shows that only a few locations are experiencing a fall, so neither "plenty" nor summing to zero as claimed. But I'm interested to learn more about the evidence that the pre-industrial trend was the same, since my inexpert googling suggests otherwise, eg "Exceptionally stable preindustrial sea level inferred from the western Mediterranean Sea"
https://www.science.org/doi/10.1126/sciadv.abm6185
https://www.science.org/doi/10.1126/sciadv.abm6185
Last I looked at the data, sea levels in Key West had risen by around one foot in the last hundred years.
https://tidesandcurrents.noaa.gov/sltrends/
Sea levels have been monitored for over 100 years... because of commerce.
East coast US seems to be going up about 3mm/year, or a foot per century. That's on top of 7 foot tides.
West coast US is very steady, barely moving at all.
The sea level is dropping in Alaska by 10mm/year. Dropping in Scandinavia also.
Some cities show rising sea levels, but really the cities are sinking due to collapsing aquifers; New Orleans and Bangkok. And measurements made on river deltas are always going to be wild due to silt and all.
Most notably, I can't find an example in the NOAA data of the rate of sea level rise increasing due to industrialization. Anybody?