Sea level rate of change

Discussion in 'Environmental Discussion' started by bwilson4web, Jun 24, 2012.

  1. tochatihu

    tochatihu Senior Member

    Joined:
    Apr 10, 2004
    5,620
    1,197
    0
    Location:
    Kunming Yunnan China
    Vehicle:
    2001 Prius
    I understand there are three ways for geology to affect seal level. Post-glacial isostatic rebound, local land subsidence (often from local fluid withdrawal), and water being pulled differently by gravity from ice or rock. This is not a clear explanation of the third, but it is a thing and different from the other two.

    Just one among many studies of isostatic rebound, with nice images:

    www.ngs.noaa.gov/CORS/Articles/2006GL027081.pdf

    Land subsidence would occur at smallest scales. Perhaps there is a general review of that topic? Otherwise it would be many site-by-site studies.

    If there are examples of published climate studies ignoring geological effects on 'net' sea level, we could have a look. Actually we've done similar before but I have to search archives for that.
     
  2. tochatihu

    tochatihu Senior Member

    Joined:
    Apr 10, 2004
    5,620
    1,197
    0
    Location:
    Kunming Yunnan China
    Vehicle:
    2001 Prius
  3. tochatihu

    tochatihu Senior Member

    Joined:
    Apr 10, 2004
    5,620
    1,197
    0
    Location:
    Kunming Yunnan China
    Vehicle:
    2001 Prius
    I remember that we discussed a particular study that chose 50 (out of many more) US tidal gauges to look for trends. Did not show up by searching here. Maybe remembering wrong, or maybe someone can post a link?
     
  4. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    18,707
    8,099
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Subsidence and upwelling are well known phenomena that have lead to 'cherry picking' tide records. So it is important to understand that some coastal flooding, like around Lake Charles, also includes subsidence. Houston has a similar problem.

    Bob Wilson
     
  5. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    18,707
    8,099
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    There was a NASA aerial study of an interference instrument to measure wide area subsidence. To the best of my knowledge no one has proposed that mission. Meanwhile, the Jason series have covered the sea level, world wide but I think we need the land studies too. That way smarter decisions can be made about how to mitigate the problems. Some area will have to go but others might respond to well designed solutions.

    Bob Wilson
     
    #45 bwilson4web, May 26, 2017
    Last edited: May 26, 2017
  6. Trollbait

    Trollbait It's a D&D thing

    Joined:
    Feb 7, 2006
    9,663
    3,026
    0
    Location:
    eastern Pennsylvania
    Vehicle:
    Other Non-Hybrid
    Only a warming denier would claim as such.
     
  7. mojo

    mojo Senior Member

    Joined:
    Sep 28, 2006
    4,519
    387
    0
    Location:
    San Francisco
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    Because apparently only deniers have the ability to be honest.
    Take subsidence ,measure sea level rise ,then adjust that figure by dishonestly ADDING to that figure accounting for isostatic rebound(which has nothing to do with rising sea levels either) .
    Pure BS.
     
  8. bwilson4web

    bwilson4web i3 and Prime

    Joined:
    Nov 25, 2005
    18,707
    8,099
    0
    Location:
    Huntsville AL with 2014 BMW i3-REx
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Source: CU Sea Level Research Group | University of Colorado
    [​IMG]
    Since 1993, measurements from the TOPEX and Jason series of satellite radar altimeters have allowed estimates of global mean sea level. These measurements are continuously monitored against a network of tide gauges. When seasonal variations are subtracted, they allow estimation of the global mean sea level rate. As new data, models and corrections become available, we continuously revise these estimates (about every two months) to improve their quality.

    An accurate technical description of tide metrics: Tide Gauge Sea Level | CU Sea Level Research Group

    [​IMG]

    . . . Although the global network of tide gauges comprises of a poorly distributed sea level measurement system, it offers the only source of historical, precise, long-term sea level data. Major conclusions from tide gauge data have been that global sea level has risen approximately 10-25 cm during the past century.

    Bob Wilson
     
  9. tochatihu

    tochatihu Senior Member

    Joined:
    Apr 10, 2004
    5,620
    1,197
    0
    Location:
    Kunming Yunnan China
    Vehicle:
    2001 Prius
    http://www.nature.com/ncomms/2014/140414/ncomms4635/abs/ncomms4635.html

    From 2014, how to detect accelerations in trend, possibly already in BobW collection.

    They used only a few sites with long records and corrected for isostatic rebound. AFAIK all serious studies do so; they are reviewed prior to publication. OTOH one could pick a Norway site for example and not correct for isostatic rebound, and obtain opposite result. Might find an affinity website interested in featuring that.
     
  10. tochatihu

    tochatihu Senior Member

    Joined:
    Apr 10, 2004
    5,620
    1,197
    0
    Location:
    Kunming Yunnan China
    Vehicle:
    2001 Prius
  11. mojo

    mojo Senior Member

    Joined:
    Sep 28, 2006
    4,519
    387
    0
    Location:
    San Francisco
    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    Its amazing how a satellite can accurately measure a fraction of a millimeter increase ,in a body of water with 30 meter waves.
    Its beyond amazing ,its unbelievable.
     
  12. fuzzy1

    fuzzy1 Senior Member

    Joined:
    Feb 26, 2009
    9,819
    3,421
    90
    Location:
    Western Washington
    Vehicle:
    2012 Prius
    Model:
    Three
    Averaging over thousands of kilometers of ocean surface, and over long time periods, easily takes care of large transient
    waves.

    Signal processing techniques are indeed amazing. We can detect millivolts of DC shifts or tíny other AC signals superimposed on large AC signals, though not with a single data point. Thousands or millions or billions of data points must be processed and averaged.
     
    #52 fuzzy1, Jun 30, 2017
    Last edited: Jun 30, 2017
  13. RobH

    RobH Senior Member

    Joined:
    Sep 18, 2006
    1,951
    526
    56
    Location:
    Sunnyvale, California
    Vehicle:
    2006 Prius
    Millimeters, inches... Sea level has been 400 feet lower, and there's about 200 feet worth of ice on Antarctica/Greenland.
     
  14. tochatihu

    tochatihu Senior Member

    Joined:
    Apr 10, 2004
    5,620
    1,197
    0
    Location:
    Kunming Yunnan China
    Vehicle:
    2001 Prius
    ice cores from both polar regions show rapid +T at end of glacial periods and slower -T descending into glaciations. Using the sea-level equivalents of stored ice stated just above, we can calculate average +SLR during the melting times of 18 mm/year. During glaciation, sea level falls at 3 mm/year.

    When the most recent glaciation was melting fast, +SLR was 17 mm/year according to coral records and similar. So there is concordance between these two separate lines of evidence.

    Now there is much less ice to melt. Have suggested before than such rapid melt rates would not be sustainable throughout loss of the 60 meters (sea-level equivalent) of remaining ice. This does not exclude possibility that a few of those meters could 'come off' quickly. If there are some fragile bits here and there. Any century of more than 1 meter of SLR (10 mm/year) would require substantial rapid changes in how humans use coastal areas.

    For context, sea levels were rising 1 to 2 mm/year until the most recent (warmer) decades. Now. 3 to 3.5 mm/year.

    +++
    Have linked above to some recent publications about SLR. Nature Communications bundled up several others:
    Sea level rise research in Nature Communications
     
Loading...