30 ms·

I'd be interested in an explanation as to why sea level would rise more some places than others. It seems to me it should raise pretty much the same everywhere

I'd be interested in an explanation as to why sea level would rise more some places than others. It seems to me it should raise pretty much the same everywhere because gravity.

Mikeb85 11y ago
I'd wager that gravity isn't 100% equal over the whole globe, the pull of the moon's gravity also isn't equal over the globe, and that the circulation of water across the world's oceans also isn't 100% (so there's different salinity, water pressure, various prevailing 'currents', temperature, etc...). Of course I don't study this, so I don't know the exact reasons, but I'm sure there is a reason...
- mturmon 11y ago
  Yes, it's all of that. Tides, temperature variations, ocean surface winds, and circulation all go in to changing sea surface height, at various time scales. It amounts to order of a couple of meters, peak-to-peak, in a weekly average. Sea surface height (SSH) has been measured from space with great accuracy, using radar altimetry, since 1992. We can now also measure sea surface temperature (SST), salinity (SSS), and surface winds. The winds are knowable because wind ruffles the water surface and this changes the radar scatter properties. Therefore, somewhat surprisingly, we know more about the ocean than the land. For more: https://en.wikipedia.org/wiki/Ocean_surface_topography; https://en.wikipedia.org/wiki/Ocean_surface_topography; the data is at http://podaac.jpl.nasa.gov/CoreMeasurements http://podaac.jpl.nasa.gov/CoreMeasurements
mkempe 11y ago
Apart from changes in sea level, sometimes the land is moving up, sometimes down. See for instance the still ongoing rebound of Scandinavia, taking place since the start of the current interglacial period (11,700 years). https://en.wikipedia.org/wiki/Post-glacial_rebound#Vertical_crustal_motion https://en.wikipedia.org/wiki/Post-glacial_rebound#Vertical_...
nusq 11y ago
Gravity is not the same around the Globe, there is something called the Geoid https://en.wikipedia.org/wiki/Geoid https://en.wikipedia.org/wiki/Geoid. Also, sea level is determined by a number of factors including astronomical and predictable, like moon, sun and other planets gravity influence, or random meteorological events like winds, low or high pressure systems and land mass configuration. All these contribute to the tide cycle and the sea level anywhere in the globle. For example, there are places in the world with huge tide amplitudes like 12 m or so and other with no tides at all (excluding meteorological events). The problem is the "mean sea level rise". The "mean sea level" is usually determined by and average of at least 19 years of measurements of the sea level, which is approximately the time it takes to complete a full moon cycle.
- dghughes 11y ago
  Tides in the Bay of Fundy here in the Maritimes Canada are 15m (50 feet). And in some places the water comes in so fast there is a mini-tidal wave the tidal bore.
- BurningFrog 11y ago
  None of this explains why a small change in ocean water volume would be distributed unevenly across the planet.
  - knowaveragejoe 11y ago
    The earth is huge(compared to us), so it's hard to grasp why it doesn't work as seemingly instantaneously as bowl of water, for example. Eventually, in a perfect vacuum, that would be the case.
  - papa_bear 11y ago
    Maybe not evenly, but proportionally?
  - chadzawistowski 11y ago
    Tradewinds?
  - 11y ago
lobster_johnson 11y ago
Mostly differences in the geoid [1]. The planet isn't perfectly round, and gravity varies quite a lot [2]. There are other factors, such as the cold/warm water cycle creating very slow currents that push water towards certain landmasses. But as I understand it, gravity is the main cause. [1] https://en.wikipedia.org/wiki/Geoid https://en.wikipedia.org/wiki/Geoid [2] http://e360.yale.edu/feature/the_secret_of_sea_level_rise_it_will_vary_greatly_by_region/2255/ http://e360.yale.edu/feature/the_secret_of_sea_level_rise_it...
nicwolff 11y ago
Article says: "Changing global trade winds have raised sea levels in the South Pacific about a foot over the past 30 years, faster than elsewhere. Scientists are studying whether those changing trade winds have anything to do with climate change."
dredmorbius 11y ago
Water temperature hasn't been mentioned -- though water famously expands as it freezes, at temperatures above about 4C, it undergoes normal thermal expansion. This means that warm equitorial waters show some of this effect as well. Winds and tides are other significant factors, both of which can vary strongly regionally and globally.
xlm1717 11y ago
>because [of] gravity
DrScump 11y ago
Before that, it needs to be asked if it is even rising sea level in the first place, as opposed to land subsidence. "It looks like Kwajalein is affected by a local subsidence induced by building construction (or some sea level “correction” in order to have it going up). The Majuro records, for sure, contradicts any (sic:"and") acceleration claim; even a general “rise”. http://wattsupwiththat.com/2013/07/31/the-marshall-islands-and-their-sea-level-changes/ http://wattsupwiththat.com/2013/07/31/the-marshall-islands-a...

I'd be interested in an explanation as to why sea level would rise more some places than others. It seems to me it should raise pretty much the same everywhere because gravity.

Mikeb85 11y ago

I'd wager that gravity isn't 100% equal over the whole globe, the pull of the moon's gravity also isn't equal over the globe, and that the circulation of water across the world's oceans also isn't 100% (so there's different salinity, water pressure, various prevailing 'currents', temperature, etc...). Of course I don't study this, so I don't know the exact reasons, but I'm sure there is a reason...

mturmon 11y ago
Yes, it's all of that. Tides, temperature variations, ocean surface winds, and circulation all go in to changing sea surface height, at various time scales. It amounts to order of a couple of meters, peak-to-peak, in a weekly average. Sea surface height (SSH) has been measured from space with great accuracy, using radar altimetry, since 1992. We can now also measure sea surface temperature (SST), salinity (SSS), and surface winds. The winds are knowable because wind ruffles the water surface and this changes the radar scatter properties. Therefore, somewhat surprisingly, we know more about the ocean than the land. For more: https://en.wikipedia.org/wiki/Ocean_surface_topography; https://en.wikipedia.org/wiki/Ocean_surface_topography; the data is at http://podaac.jpl.nasa.gov/CoreMeasurements http://podaac.jpl.nasa.gov/CoreMeasurements

mkempe 11y ago

Apart from changes in sea level, sometimes the land is moving up, sometimes down. See for instance the still ongoing rebound of Scandinavia, taking place since the start of the current interglacial period (11,700 years). https://en.wikipedia.org/wiki/Post-glacial_rebound#Vertical_crustal_motion https://en.wikipedia.org/wiki/Post-glacial_rebound#Vertical_...

nusq 11y ago

Gravity is not the same around the Globe, there is something called the Geoid https://en.wikipedia.org/wiki/Geoid https://en.wikipedia.org/wiki/Geoid. Also, sea level is determined by a number of factors including astronomical and predictable, like moon, sun and other planets gravity influence, or random meteorological events like winds, low or high pressure systems and land mass configuration. All these contribute to the tide cycle and the sea level anywhere in the globle. For example, there are places in the world with huge tide amplitudes like 12 m or so and other with no tides at all (excluding meteorological events). The problem is the "mean sea level rise". The "mean sea level" is usually determined by and average of at least 19 years of measurements of the sea level, which is approximately the time it takes to complete a full moon cycle.

dghughes 11y ago
Tides in the Bay of Fundy here in the Maritimes Canada are 15m (50 feet). And in some places the water comes in so fast there is a mini-tidal wave the tidal bore.
BurningFrog 11y ago
None of this explains why a small change in ocean water volume would be distributed unevenly across the planet.
- knowaveragejoe 11y ago
  The earth is huge(compared to us), so it's hard to grasp why it doesn't work as seemingly instantaneously as bowl of water, for example. Eventually, in a perfect vacuum, that would be the case.
- papa_bear 11y ago
  Maybe not evenly, but proportionally?
- chadzawistowski 11y ago
  Tradewinds?
- 11y ago

lobster_johnson 11y ago

Mostly differences in the geoid [1]. The planet isn't perfectly round, and gravity varies quite a lot [2]. There are other factors, such as the cold/warm water cycle creating very slow currents that push water towards certain landmasses. But as I understand it, gravity is the main cause. [1] https://en.wikipedia.org/wiki/Geoid https://en.wikipedia.org/wiki/Geoid [2] http://e360.yale.edu/feature/the_secret_of_sea_level_rise_it_will_vary_greatly_by_region/2255/ http://e360.yale.edu/feature/the_secret_of_sea_level_rise_it...

nicwolff 11y ago

Article says: "Changing global trade winds have raised sea levels in the South Pacific about a foot over the past 30 years, faster than elsewhere. Scientists are studying whether those changing trade winds have anything to do with climate change."

dredmorbius 11y ago

Water temperature hasn't been mentioned -- though water famously expands as it freezes, at temperatures above about 4C, it undergoes normal thermal expansion. This means that warm equitorial waters show some of this effect as well. Winds and tides are other significant factors, both of which can vary strongly regionally and globally.

xlm1717 11y ago

>because [of] gravity

DrScump 11y ago

Before that, it needs to be asked if it is even rising sea level in the first place, as opposed to land subsidence. "It looks like Kwajalein is affected by a local subsidence induced by building construction (or some sea level “correction” in order to have it going up). The Majuro records, for sure, contradicts any (sic:"and") acceleration claim; even a general “rise”. http://wattsupwiththat.com/2013/07/31/the-marshall-islands-and-their-sea-level-changes/ http://wattsupwiththat.com/2013/07/31/the-marshall-islands-a...