# Climate change: Sea level rising faster in the Pacific? **URL:** \ **Category:** Factual Questions\ **Created:** [August 27, 2024, 9:43am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299 "2024-08-27T09:43:06Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [August 27, 2024, 9:43am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/1 "2024-08-27T09:43:06Z")
Reading this article this morning: > **[‘The ocean is overflowing’: UN chief issues global SOS as new reports warn...](https://www.cnn.com/2024/08/27/climate/rising-sea-levels-pacific-islands-climate-intl-hnk-scn/index.html)** > > A “worldwide catastrophe” is imperiling Pacific Islands and the world must respond to the unprecedented and devastating impacts of rising seas “before it is too late,” the United Nations chief has warned. I was struck by this line: > Sea surface temperatures in the Southwest Pacific have risen three times faster than the global average since 1980, [according](https://library.wmo.int/viewer/68995/download?file=1356_State-of-the-Climate-in-SWP-2023_en.pdf&type=pdf&navigator=1) to the World Meteorological Organization’s State of the Climate. > > And sea levels in the region have risen at almost twice the global average over the past 30 years, it found. OK, I get that the temperature of the ocean can vary from place to place, and that it may change at differing rates in different places. But if I’m understanding them correctly, they’re saying that the average sea level in SW Pacific ocean is increasing faster than in other places around the world. This claim is at odds with my understanding of how water and gravity work. I mean if you bump up the local sea level quickly and by a large amount, it will take time for that bulge of water to spread out and achieve an equilibrium level with the rest of the world’s oceans. That’s basically how a tsunami works: a thrust fault slips and creates a mound of water in the ocean over the course of several seconds, and within hours that mound of water has spread out and achieved equilibrium level again. But climate change is taking place over decades, and the sea level rise is very small compared to what happens in a tsunami, so I’m at a loss to understand how sea level increase in the SW Pacific could be higher, over the long term, than the sea level increase elsewhere in the world. It’s like starting with a reference level of water in a bathtub, pouring some extra water in the tub, and then having that extra water stay in a pile right where you poured it. Can someone 'splain? ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [August 27, 2024, 9:49am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/2 "2024-08-27T09:49:48Z")
The earth bulges a bit at the equator; the pacific ocean occupies a greater span of the equator than other oceans; this might have something to do with it. ---
**Author:** ![Tatterdemalion](https://avatars.discourse-cdn.com/v4/letter/t/43a26b/32.png) [@Tatterdemalion](https://boards.straightdope.com/u/Tatterdemalion)\ **Post date:** [August 27, 2024, 9:59am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/3 "2024-08-27T09:59:29Z")
Also water expands when heated. If the sea temperature is higher in a particular place, it will expand, giving a larger local sea level rise. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [August 27, 2024, 10:30am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/4 "2024-08-27T10:30:29Z")
> [@Tatterdemalion](#): > > Also water expands when heated. If the sea temperature is higher in a particular place, it will expand, giving a larger local sea level rise. That’s all fine and dandy, but gravity doesn’t like it when water is piled higher in one place than in some other. The SW Pacific warmed up faster than other parts of the ocean, and now it’s bulging upward more than those other (less-warmed-up) parts of the ocean. So what’s keeping this pile of water in the SW Pacific from spreading out across the rest of the oceans and getting all of them to a common level? ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [August 27, 2024, 11:03am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/5 "2024-08-27T11:03:16Z")
The earth’s gravity is not uniform. Sea level is _not_ flat and never has been. As you suggest, sea level follows local gravity. But local gravity _here_ is different from local gravity _there_. I gotta leave or I’d explain a lot more with cites. I suggest you start here: > **[Sea level](https://en.wikipedia.org/wiki/Sea_level)** > > Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A co... “Sea level” is far more complicated than “flat smooth sphere” ---
**Author:** ![Schnitte](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/schnitte/32/9033_2.png) [@Schnitte](https://boards.straightdope.com/u/Schnitte)\ **Post date:** [August 27, 2024, 11:07am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/6 "2024-08-27T11:07:11Z")
There’s a massive [gravity anomaly](https://en.wikipedia.org/wiki/Indian_Ocean_Geoid_Low) (Wiki) in the Indian Ocean that causes the water level there to be more than a hundred metres below the global mean. So yes, it’s not as if the sea level is uniform everywhere. ---
**Author:** ![Tatterdemalion](https://avatars.discourse-cdn.com/v4/letter/t/43a26b/32.png) [@Tatterdemalion](https://boards.straightdope.com/u/Tatterdemalion)\ **Post date:** [August 27, 2024, 11:16am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/7 "2024-08-27T11:16:56Z")
The fact that the ocean temerature is different in different places means that the local seal level will be different. This is in addition to the gravitational effects referred to above. Also, there are ocean currents. That means more water is piled up in some places than others. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [August 27, 2024, 11:28am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/8 "2024-08-27T11:28:54Z")
> [@LSLGuy](#): > > The earth’s gravity is not uniform. Sea level is _not_ flat and never has been. As you suggest, sea level follows local gravity. But local gravity _here_ is different from local gravity _there_. Yep, I get that gravity is not uniform, and sea “level” isn’t actually flat. The moon also causes tides, which change local sea level dramatically a couple of times a day. Plenty of other factors, too. But I’m not aware of any of those other factors changing. AFAIK, gravity and all its local anomalies around the world are much as they have been since we started measuring sea level, and the moon still orbits as always. > [@Tatterdemalion](#): > > The fact that the ocean temerature is different in different places means that the local seal level will be different. Suppose I fill my bathtub with cold water. I put a divider in the middle, and heat up the water on one side of the divider. The hot water has expanded, so now its level is taller than that of the cold water. I remove the divider. Hot water will flow out over the cold water because it’s sitting higher, and also because buoyancy-driven convection will cause cold water to push in under the warmer water and also allow the hot water to spread out even more. A new equilibrium water level will be established in the tub; the new level will everywhere be higher than the old level because the average temperature of the water in the tub is higher than it used to be. Even assuming local gravitational anomalies that mean the surface of the water isn’t (and wasn’t) a perfectly flat surface, we should still be able to define the original shape of the surface, whatever it was, and observe that the new shape is the same, except a little higher everywhere (as opposed to being much higher in some places and only a little higher in other places). Why would this same thing not be happening in the SW Pacific? ---
**Author:** ![Tatterdemalion](https://avatars.discourse-cdn.com/v4/letter/t/43a26b/32.png) [@Tatterdemalion](https://boards.straightdope.com/u/Tatterdemalion)\ **Post date:** [August 27, 2024, 11:49am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/9 "2024-08-27T11:49:08Z")
Because the earth is not a bathtub? The fact that there are ocean currents, means that there is more water in one place than in another. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [August 27, 2024, 12:13pm UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/10 "2024-08-27T12:13:59Z")
> [@Tatterdemalion](#): > > Because the earth is not a bathtub? How is the ocean different from the bathtub scenario I described? In both cases, there are differences in water height and/or density that drive the movement of water to achieve a new equilibrium water level. The movements of water in the bathtub that I described in my previous post are analogous to ocean currents. > [@Tatterdemalion](#): > > The fact that there are ocean currents, means that there is more water in one place than in another. Just as there have always been tides and gravitational anomalies, there have always been ocean currents. What’s special about the SW Pacific? ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [August 27, 2024, 7:14pm UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/11 "2024-08-27T19:14:56Z")
> [@Machine\_Elf](#): > > How is the ocean different from the bathtub scenario I described? In both cases, there are differences in water height and/or density that drive the movement of water to achieve a new equilibrium water level. The movements of water in the bathtub that I described in my previous post are analogous to ocean currents. The Earth’s atmosphere and hydrosphere are not equilibrium systems and never come to a homogenous stable condition like your bathtub analogy. Warmer water will be less dense, and will therefore occupy more volume for the same mass, and thus will contribute to greater rise in mean sea level. There are other contributors but this is the driving cause of increase in mean sea level in the South Pacific. The tropical and subtropical South Pacific islands of Melanesia, Micronesia, and Polynesia are also uniquely vulnerable to sea level change as they are low laying, with small water tables that are often only segregated from seawater by osmotic pressure, so they are doubly threatened by sea level rise both consuming living and agricultural spaces as well as compromising freshwater reservoirs. Stranger ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [August 30, 2024, 11:02am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/12 "2024-08-30T11:02:15Z")
Your bathtub doesn’t have trillions of gallons of water in it, and isn’t constantly in an uneven state of heating, and the Americas are still dividing the Pacific and Indian Ocean. ---
**Author:** ![md-2000](https://avatars.discourse-cdn.com/v4/letter/m/9d8465/32.png) [@md-2000](https://boards.straightdope.com/u/md-2000)\ **Post date:** [August 30, 2024, 12:21pm UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/13 "2024-08-30T12:21:41Z")
I vaguely recall a trivia bit that the Pacific sea level is 14 feet higher than the Atlantic/Caribbean at the Panama canal. Also, cause for alarm, there are a lot more inhabited small low-lying islands in the Pacific, so more affected - also meaning that things like storm surges are more impactful. And as mentioned, these islands close to the equator in warm water are more likely to encounter tropical storms. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [August 31, 2024, 4:35am UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/14 "2024-08-31T04:35:16Z")
Also, some southern or not-so-southern pacific coastal cities have some of the highest subsidence rates on earth. They’re high enough that sea level rise will compound _subsidence_ rather than the other way around. I couldn’t find any math on how the _South Pacific_ per se could retain a lot of its sea level rise from warming water. But one of the links I found did mention that high waves that distribute sea level change toward the east coast of the US could take _years_ to hit it even though they start in the Atlantic. This is new information to me, since I had assumed that water would redistribute itself, in the absence of active factors like gravity anomalies or currents, at the rate of the waves that I had _imagined_ in my mind, namely, around as fast as a walking pace at the very minimum, and would thus only take a year or so at the very most to travel around the world, with no one spot in the ocean being permanently higher via thermal expansion. But if the waves that redistribute this water _do_ move very slowly, then it makes logical sense that the south pacific could have a permanent sea level rise compared to the rest of the globe. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [August 31, 2024, 2:37pm UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/15 "2024-08-31T14:37:30Z")
> [@Machine\_Elf](#): > > > [@Tatterdemalion](#): > > > > Because the earth is not a bathtub? > > How is the ocean different from the bathtub scenario I described? In both cases, there are differences in water height and/or density that drive the movement of water to achieve a new equilibrium water level. The movements of water in the bathtub that I described in my previous post are analogous to ocean currents. > > The oceans aren’t contained in a simple container with a divider in the middle. There are more constraints on the passage of water between the oceans in addition to all the local variations in each ocean. > > > [@Tatterdemalion](#): > > > > The fact that there are ocean currents, means that there is more water in one place than in another. > > Just as there have always been tides and gravitational anomalies, there have always been ocean currents. What’s special about the SW Pacific? There have always been difference in sea level around the world. The volume of liquid water in the oceans is increasing and it’s not going to be distributed equally. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [August 31, 2024, 6:11pm UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/16 "2024-08-31T18:11:47Z")
Another thing I couldn’t find exact details on is how much the outsized increase is due to being on the opposite side of the retreating Greenland ice sheet, which releases water around it due to lowered regional gravity. Not knowing any better, my simplistic math tells me it’s plausible that this could account for some of the millimeters but I can’t find anything firm from my searches. Plus it’s probably a measurable factor since articles are reporting it as a factor. ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [August 31, 2024, 7:45pm UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/17 "2024-08-31T19:45:56Z")
> [@Machine\_Elf](#): > > But I’m not aware of any of those other factors changing. AFAIK, gravity and all its local anomalies around the world are much as they have been since we started measuring sea level, and the moon still orbits as always. Sea level can vary ocean to ocean- but not by a lot. But a centimeter change is quite a large change, even tho that sort of small sea level difference would not be remarked on. [https://sealevel.nasa.gov/faq/9/are-sea-levels-rising-the-same-all-over-the-world-as-if-were-filling-a-giant-bathtub/#:~:text=Level%20Change%20Portal-,Are%20sea%20levels%20rising%20the%20same%20all%20over%20the%20world,%2C%20heating%2C%20evaporation%20and%20precipitation](https://sealevel.nasa.gov/faq/9/are-sea-levels-rising-the-same-all-over-the-world-as-if-were-filling-a-giant-bathtub/#:~:text=Level%20Change%20Portal-,Are%20sea%20levels%20rising%20the%20same%20all%20over%20the%20world,%2C%20heating%2C%20evaporation%20and%20precipitation). _No. [Sea level rise is uneven](https://sealevel.nasa.gov/news/24/), the two main reasons being ocean dynamics and Earth’s uneven gravity field._ _First, ocean dynamics is the redistribution of mass due to currents driven by wind, heating, evaporation and precipitation. For example, during La Niña events, sea level goes down because some rain that usually occurs over the ocean shifts to land, and the same phenomenon produces low latitude currents that redistribute seawater. Regional climate cycles, like El Niño and La Niña, and longer-term effects, like the Pacific Decadal Oscillation, change ocean circulation, which changes sea level._ _A [visualization](http://sealevel.nasa.gov/resources/69/grace-global-gravity-animation) of Earth’s gravity field using Gravity Recovery and Climate Experiment (GRACE) data. Gravity is determined by mass; Earth’s mass is not distributed equally, and it also changes over time. Credit: NASA/JPL/University of Texas Center for Space Research_ _Second, because the distribution of Earth’s mass is uneven, [Earth’s gravity is also uneven](https://earthobservatory.nasa.gov/features/GRACE/page3.php). Therefore, the ocean’s surface isn’t actually a perfect sphere or ellipsoid; it is a bumpy surface. As the land-based ice sheets of Greenland and Antarctica continue to unload their mass (lose ice) from far above sea level and far from the tropics, that mass reaches the sea in the form of meltwater that is then redistributed along Earth’s gravity field._ At Panama the difference is striking due to unusual currents and tides- > **[Panama Tides](https://www.usni.org/magazines/proceedings/1926/april/panama-tides)** > > The difference in tides on ---
**Author:** ![sunacres](https://avatars.discourse-cdn.com/v4/letter/s/4491bb/32.png) [@sunacres](https://boards.straightdope.com/u/sunacres)\ **Post date:** [September 2, 2024, 5:15pm UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/18 "2024-09-02T17:15:23Z")
I was under the same impression as the OP and found this thread very frustrating to read as no one seemed to quite understand the question, even the NASA site is confusing, until I finally got to this graphic, which blows my mind: [![](https://sealevel.nasa.gov/internal_resources/443) ](https://sealevel.nasa.gov/internal_resources/443) That’s the change in sea level _between 1992 and 2019_ - blue is falling, red is rising! I’m starting to see that sea level is something like a very complex standing wave that persists over very long time spans. Smack my gob. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [September 2, 2024, 5:37pm UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/19 "2024-09-02T17:37:25Z")
Here is the page that image comes which describes the contributing factors to regional sea level change: > **[NASA Sea Level Change Portal: Overview](https://sealevel.nasa.gov/understanding-sea-level/regional-sea-level/overview)** > > Visit NASA's portal for an in-depth look at the science behind sea level change. Stranger ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [September 2, 2024, 7:08pm UTC](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299/20 "2024-09-02T19:08:34Z")
Great cites both of you; thank you. I’ll just point out since it’s hard to read that the total height range on that color map is ~30cm or very very roughly 1 foot. They’re measuring something very very big to a very very fine tolerance considering its overall size. [Next page](https://boards.straightdope.com/t/climate-change-sea-level-rising-faster-in-the-pacific/1006299.md?page=2)