Thursday, September 3, 2015

Peak Sea Level - 5

The Sea Level Changes
I. Background

Today let's discuss the impact of sea level fall (SLF) on the ice shelves and ice sheets of Antarctica and Greenland.

In a previous post I disagreed with Mitrovica and Gomez about that (Peak Sea Level - 3).

They had indicated that SLF around Antarctica will slow the rate of glacial ice sheet flow into the sea, so, today I offer more evidence and argument for my assertion, because of my respect for them.

II. Dr. Rignot I Presume

The NASA scientists have done a lot of work on the unknowns of Antarctica, which in this post specifically focuses on the nature of the ice shelves which are known to be holding back the ice sheets.

The video in today's post is a presentation by Dr. Rignot detailing how ice sheet glaciers speed up as much as 8 times faster when their ice shelf collapses.

That is because when the ice shelf disconnects from the ice sheet it has been connected to, it offers no further buttress to the flow of the ice streams or glaciers of the ice sheet which it had previously been slowing down.

III. Nature of Stresses On The Ice Shelf

In the video below, Dr. Rignot mentions the stress of tides on the ice shelf, which floats
Fig. 1 High Tide
on the top of seawater, pushed up and pulled down as the tides ebb and flow.

If you have ever bent a thin piece of sheet metal back and forth in an attempt to have it break at a certain line, you know that as you bend it back and forth, it heats up, then becomes more pliable as the heat increases as you bend it back and forth faster, and then the metal continues to weaken until it eventually breaks along the bend line.

Fig. 2 Low Tide
The ice shelf has similar stresses on it as warm water tides underneath push up at high tide to cause one type of stress (Fig. 1).

Then gravity pulls down as the tide lowers, causing an opposite stress (Fig. 2) during "ice-flex" which eventually, usually after years of that stress, causes some of it to break off (the ice shelf growing further and further into the warming ocean and becoming thinner, adds to ice shelf's demise).
Fig. 3 Sea Level Fall

Like Greenland's Jakobshavn glacier did earlier this year (The Evolution of Models - 11).

When SLF takes place (Fig. 3), slowly the degree of upward pressure from the high tide diminishes as the sea level drops, until eventually the situation becomes like a permanent low tide, because the ice shelf becomes more or less above the high tide mark.

(Note that Fig. 1, Fig. 2, and Fig. 3 are exaggerated for effect.)

IV. The Result of Ice Shelf Loss

Where this is going is a contemplation of sea level change (SLC), which, in the scientific news media literature, generally speaking, is only contemplated as sea level rise (SLR):
Over the past two decades, the massive platforms of floating ice [ice shelves] that dot the coast of Antarctica have been thinning and doing so at an increasing rate, likely at least in part because of global warming. Scientists are worried about its implications for significant sea level rise.

The ice shelves—some of which are larger than California and tens to hundreds of yards thick—are the linchpins of the Antarctic ice sheet system, holding back the millions of cubic miles of ice contained in the glaciers that flow into them, like doorstops. As the ice sheets thin, the massive rivers of ice behind them can surge forward into the sea.
(Scientific American, emphasis added). I would argue that it is clear that SLF is not going to slow down glacial flow to the sea.

My view is that it will accelerate it.

Which means that the East Coast of the United States, as well as sea ports in most locations around the globe, are an endangered species now.

You get my drift (Greenland & Antarctica Invade The United States, 2, 3, The 1% May Face The Wrath of Sea Level Rise First, Why The Military Can't Defend Against The Invasion, Weekend Rebel Science Excursion - 44, Why Sea Level Rise May Be The Greatest Threat To Civilization, 2, 3, 4, 5).

V. Conclusion

It is incumbent on Dr. Mitrovica and/or Dr. Gomez to clarify or rescind their statement that SLF would slow down ice sheet loss and re-stabilize the ice sheet once again.

At least they should clarify to some degree (Gomez said it would only slow it down, not stop it).

They should interface with glaciologists so they can improve the glaciologists' lack of understanding of the physics of ice-sheet-mass gravity, and the glaciologists can likewise improve Mitrovica's and Gomez's understanding of more recent research (concerning ice shelf collapse on ice sheet flow).

As shown by Dr. Rignot in the video below.

The previous post in this series is here.

A discussion about ice shelves vs. ice sheets:

15:29 when the ice shelf "Larsen A" collapsed the entire glacier's flow speed toward the sea increased ...
18:50 "Larsen B" ice shelf collapse caused the same thing ... the entire glacier's flow accelerated toward the sea ...
19:30 when the ice shelf goes away so does the restraint on the glacier, and they then move faster, 8 times faster, toward the sea
27:15 the East Antarctica Totten Glacier basin contains about as much ice as all of Western Antarctica, and it is destabilizing
30:30 the condition of the ice shelf controls what happens to the ice sheet



    5 Trillion Tons of Ice Lost Since 2002


    1. Tom,

      Interesting link, written by an astronomer (cross discipline can be helpful, e.g. Dr. Mitrovica & his gravity SLF explanations).

      Imagine the scientific panic should "ice sheet glaciers speed up as much as 8 times faster when their ice shelf collapses" (Dr. Rignot).

      The key danger zones are Totten @ E. Antarctica, Thwaites in W. Antarctica, and NEGIS & Jakobshavn in Greenland.

      13 years @ 5 trillion = 2.6 * 8 = 20.8 trillion tons per year or (270.4 trillion tons over a span of 13 yrs.).

  2. That's a LOT of ice melting into water eventually. Is there a way to calculate it to sea level rise on the east and west coasts of USA? 7 - 10 meters sound about right?


    1. Tom,

      That brought up something Dredd hasn't done yet.

      Take an SLR number at the other end (e.g. 10 m in the yr. 2100) then calculate backwards until now, then give the SLR value today.

  3. Randy & Tom,

    Thinking outside the box again in the


    Tom, the "10,7,5,3,2 oscillating" model shows numbers close to your low end of 7m.

    It reaches that number circa 2100 (you did not give an ending date for when to reach the 7-10 meters).

    That "10,7,5,3,2 oscillating" model's graphs and data show a ~6m SLR @ east coast by 2100 (The Evolution of Models - 12).

    I am working on a new type of SLC that indicates where ice has melted, based on the Mitrovica / Gomez "fingerprint" a la what was discussed in The Evolution of Models - 13.

    The hundreds of tide gages used by Mitrovica have been around for a hundred years or more in some cases.

    The "golden gages" (The Evolution of Models - 13) fingerprint data can be put into this new SLC model I am designing and it will tell how much ice has melted or calved into the sea at each relevant ice sheet (Greenland, Antarctica) and/or the non-polar glacial ice areas (e.g. southeast Alaska).

    Once that is coded and working well, I will add the projection algorithms (binary prophets) which will predict their readings in the future.

    That will test the efficacy of the model because it can be tested daily by comparing it to the tidal gages.

    The bottom line on that is that as the data are entered daily, from the real-time global gages, the model will educate itself accordingly and change the projections / predictions as needed in real-time.

    Have a good weekend anyway. ;)