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A new round of Antarctic ice alarm

March 28, 2015

The alarm of a catastrophic meltdown of the Antarctic cycles up and down every year or two.  A journal article says the rate of melt is increasing, the popular press picks up on it and breathlessly warns about huge sea level rises sinking coastal cities around the world. We are told that x number of gigatonnes of ice per year are being dumped off the continent and wreaking their havoc on the world.   Then another study says “not so fast,” the mass losses aren’t that great after all.  Or, some crazy old skeptics ruin all the fun by recklessly bringing some logic to the discussion.

Today we have “Volume loss from Antarctic ice shelves is accelerating” (Paolo, et. al., Science, 2015).  The abstract warns us

“Overall, average ice-shelf volume change accelerated from negligible loss at 25 ± 64 km3 per year for 1994-2003 to rapid loss of 310 ± 74 km3 per year for 2003-2012.”

310 km3 per year (roughly the same as 310 gigatonnes per year) is pretty high compared to most other estimates. So you will probably see many references to this number because the bigger and scarier the more the press likes it.  But for the more sober minded, consider the following comparison of ice loss estimates from “Ice sheet mass balance and climate change” (Hanna, et. al., Nature, 2013)

Various estimates of ice mass change in the antarctic

Various estimates of ice mass change in the Antarctic

How does the recent Science paper compare?  If we place it on estimate plots from Hanna’s paper it would look like this..

Ice sheet mass balance and climate change - Hanna - Nature - 2013 v4

The Paolo Nature paper is an outlier.  But lets take them at their word.  They say that the Antarctic, on average, shed about 300 more Gigatonnes of ice per year during the 2003 to 2012 period than during the 1994 to 2003 period.  Where did all this ice go?  In to the oceans, of course.  That is why we have the great sea level rise scare.

So it follows that the sea level should have been rising faster during the 2003 to 2012 period than during the 1994 to 2003 year period.  How much faster?  Well, every gigatonne of water dumped into the oceans raises the sea level by about 2.78 microns. So 300 gigatonnes of extra water per year would raise the sea levels about an extra 840 microns a year, or about an extra 0.84 mm per year.  We are told that satellite data indicates that the global sea level is rising about 3 mm per year.  0.84 mm per year is a significant fraction of 3 mm per year, so such a rate increase should really stand out in the sea level rise data..

Well, here is some of that satellite sea level rise data…

This slideshow requires JavaScript.

This discussion has been about ice that is moving from the land to the sea and raising the sea level.  But let’s take a quick moment to look at the sea ice that surrounds Antarctica.  While this ice does not contribute to changes in the sea level, it does say something about the conditions in that area.

seaice_anomaly_antarctic - Cryosphere Today 150328

Do you see a trend?  I see a trend.  And I know there are variety of “just-so stories” to explain away this trend, but I am unconvinced.

Conclusion

Between 1994 and 2003 the average sea level rise rate was 3.77 mm/yr, according to satellite data (University of Colorado).  If the Antarctic were depositing an average of about 300 more gigatonnes of water in the ocean per year in the following years (2003 to 2012), then the average sea level rise rage from 2003 to 2012 should have increased by about 0.84 m/yr, to 4.61 mm/yr.

Instead, the average sea level rise rate from 2003 to 2012 dropped to 2.66 mm/yr.

The claim of a huge rise in ice loss from the Antarctic over this period is quite implausible.

9 comments

  1. You are so stupid you can’t even do basic arithmetic. Just like most AGW-deniers. Which explains so much.


    • Mr. Anon,

      Please show me where my math is wrong.

      As for my math skills, I have a Master’s degree in Physics, am a working scientist, published in some pretty prestigious journals including Nature and Applied Physics Letters and have thousands of citations.

      How about you?

      See…
      https://climatesanity.wordpress.com/about/

      best regards,
      Tom Moriarty


    • Nice sentence, “Just like most AGW-deniers.”

      If you can’t love them, then “like” is fine with me.


  2. I think what is missing in this whole picture is the evidence of the assumption that melting ice leads to sea level rise. That is based on a simplistic assumption that the surface water is all that there is, so melting ice has nowhere else to go.

    I’ve searched for papers proving correlation between ice-melt and sea level rise, thermal expansion taken into account, and i can’t find any. The ‘room’ that is found in the sea level rise data to allow the ice to melt into it could easily be absorbed by errors/uncertainty. This correlation: ice melt= sea level rise is the underlying assumption behind all the modelling panic and is unproved.

    So, Given that the basic assumption may be false – it is quite possible that Ice is melting (as measured by GRACE etc) in large amounts. The water simply has somewhere else to go.

    My bet is: The ancient idea of the ‘great fountains of the deep’ is a mythologised explanation of a connection between surface seas and inner seas (of whatever form they take).

    One common error that scientists make is they base their volume calculations (etc) on newtonian physics. The earth bends spacetime quite significantly (as is seen in glacial melt when sea levels drop after the melt as the sea is drawn towards the mass of the melted glacier less). The volume of the earth is much larger than can be calculated from its diameter. As we go down the gravity well (towards the trenches, for example), space is even more stretched (the curvature of spacetime is greater). The mathematics describing liquid exchange between the sea floor and the mantle and sub-crust water deposits is more far complex than it appears.

    http://physics.stackexchange.com/questions/36349/how-much-does-the-curvature-of-space-change-the-volume-of-earth-by


  3. Did you account for the offsetting ice increases in East Antarctica?
    Note the paper just says ice-shelf loss.


  4. Also, is it possible that this is sea ice that is being lost?


  5. Antarctic ice shelves is the floating ice around Antarctica (as seen in the first sentence of the abstract). So there is no correlated sea level rise expected! And the calculations in this blog entry therefore make no sense.


    • Mr. Anonymous,

      Thank you for the comment.

      The expectation is that as the floating ice around Antarctica breaks off and melts, it will be replaced by new ice moving off from the land. If fact the first sentences of the abstract say…

      “The floating ice shelves surrounding the Antarctic Ice Sheet restrain the grounded ice-sheet flow. Thinning of an ice shelf reduces this effect, leading to an increase in ice discharge to the ocean”

      It is kind of like a conveyor belt. Thus we are in fact talking about water being added to the ocean. You may be confusing this situation with the Arctic ice, which is not ice that is moving from the land to the ocean.

      ClimateSanity


  6. Reblogged this on Canadian Climate Guy.



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