NASA sea level briefing 2015/08/26

Discussion in 'Environmental Discussion' started by bwilson4web, Aug 27, 2015.

  1. bwilson4web

    bwilson4web i3 and Prime

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    On Wednesday NASA had a briefing on sea level rise. I had no time to listen but this is the homepage for that briefing:
    As Seas Rise, NASA Zeros In: How Much? How Fast? | NASA

    . . . Residents of China's Yellow River delta are swamped by sea level rise of more than nine inches (25 centimeters) a year.
    . . .

    I know sea level rise is not uniform and even decreasing in areas of glacier rebound and faster where the land is subsiding but this is amazing.

    Bob Wilson
     
  2. austingreen

    austingreen Senior Member

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    They didn't change this did they?
    New Data Reveals Sea Level Is Rising Fastest in Louisiana | Field & Stream

    What is it sea level rise by 2100 is expected to be 0.3-1 meter. Yellow river delta and Mississippi river delta arre subsisting much faster. This should not surprise anyone. The chinses have controlled the yellow river and it no longer deposits silt where it used to which protected the land. On the 10th anniversary of Katrina you can see that effect on Louisiana.
     
  3. bwilson4web

    bwilson4web i3 and Prime

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    Nothing much has changed in that respect:
    http://tidesandcurrents.noaa.gov/sltrends/sltrends.html

    I'm amused by the 10 year anniversary, Katrina stories that I have been switching off. In those 10 years, global sea level increased ~32 mm, 3.2 cm, ~1.25 inches. This is about the space between the mouth and nose. What I find more interesting is the effect on sea facing glaciers.

    As the mean sea level rises, aside from undermining, the real issue is off-loading the weight and braking force at the bottom. Friction has a curious, non-linear behavior. The static coefficient is higher than the dynamic friction. Once motion starts, the drag force goes down, significantly. There is one mitigation.

    There is an annual swing of ~10 mm during the year ending ~3.2 mm higher at the peak sea level of each year. The floating and near-floating ice sees a larger annual sweep than the annual increase. The annual, sea-level peak appears between July 1 and Sept 1 but Arctic melt and Antarctic freeze has another three weeks:
    • Arctic sea ice melt had a surge this week
    • Antarctic sea ice freeze flattened out this week
    If we reach October 2015 without a major glacier event, then sea levels should follow the expected decline and the next risk will be five months later, March 2016, for the Antarctic melt season. Ice cracks both ways and Antarctica risks ice shelf break-ups.

    One mitigation, we've seen northern Greenland have a lot of melt-days this year but the Summit station has not reported wide-spread, surface melt. The old Arctic sea ice still abutts the northern Greenland glaciers.

    Bob Wilson
     
  4. austingreen

    austingreen Senior Member

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    Its amazing how things changed. Texas got a lot of the evacuees. Many still live here. Some blaimed climate change, but it was the levies and how they were not updated, and what they and other man made construction did to the wetlands. Sea level is higher today, but the wetlands are a little healthier even post bp spill, and the levies have been upgraded (although not enough for a cat 5).

    There are lots of nasty articles about some of that mitigation. Often the best mitigation is to let nature repair itself and create a new equilibrium. In many communities they are building expensive structures and moving more people in to be at risk. These major river deltas like the Mississippi and the yellow don't really like human interference. The land is going to subsist even if there was no global sea level change.

    Single years are variable. I think the mitigation in greanland is to put a protective cover on the ice in the hotter months. I don't think that is worthwhile. I say let it melt. Mitigate with a sea wall by new York as the corps of engineers suggested 50 years ago, and please stop proviging subsidized insurance to move more and more people and expensive property into the danger zone.

    Sea level rise is real. I don't think its catastrophic, but we seem to be doing dumb things. It may be much cheaper to move people than pretend we can stop the melt. Sea levels were much higher in the last two interglacials, and in this one man is accelerating the melt.
     
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  5. bwilson4web

    bwilson4web i3 and Prime

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    On a somewhat related idea:

    A stadial freeze, predicted due to a collapse of the North Atlantic Thermohaline Current would follow in the wake of large-scale melting and discharge of large parts of the Greenland ice sheet. With further rise in atmospheric CO2 this would constitute a transient stage in global warming.

    Source: How to make sense of 'alarming' sea level forecasts

    I have not studied the 'North Atlantic Thermohaline Current' but noticed from the Unisys sea surface temperature (SST) the summer cold spot southeast of Greenland which has been evident this 2015. Reports are the effect on the thermohaline current is from freshwater melt effect. Now I'm wondering if it is seasonal?

    Another puzzle to noodle out of the Unisys SST data. I've been more interested in the Pacific Northeast-Central, warm water blob because of the effect on our west coast cousins.

    Bob Wilson
     
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