Two Comments on Antarctic Ice Accumulation

Jo Nova blogs on a study that claims the Antarctic continent is accumulating ice mass at a rapid rate. I have made two comments. One is opposing someone who claims that Antarctica is actually losing ice. The other is that the claimed rate of ice accumulation does not make sense against known data on sea levels.

Manicbeancounter

April 17, 2013 at 6:27 am · Reply

John Brooks says

I’m also interested that the mass of antarctic land ice follows solar irradiance. This makes perfect sense. However I can’t see why the effective of an increase in the greenhouse effect wouldn’t have exactly the same result.

Maybe you should look at the period covered by the graph John. There is an 800 year correlation of mass of antarctic land ice with solar irradiance, with the biggest movements in both prior to 1800. Insofar as the greenhouse effect is significant, it is nearly all after 1945.

And for some reason, I’ve got the idea in my head that antarctic land ice is decreasing.

Sure enough from the Carbon Brief link, this quote

Measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite since 2002 have shown that the mass of the Antarctic ice sheet is decreasing at an average rate of 100 cubic kilometres every year – the size of a small UK city.

(emphasis mine)
The size of a city is usually measured in area, not volume. The ancient City of York, for instance, has an area of 272 square kilometres (105 square miles) and a population of 125,000. Or maybe they mean the volume of the buildings in a city? A famous building in New York is the Empire State Building. Not only is it quite tall it also has quite a large volume. Around 1,040,000 cubic metres or 0.001 cubic kilometres in fact. So does the Carbon Brief claim that a small UK city have a volume of buildings equivalent to 100,000 Empire state buildings? Or each average person in a small UK city occupies a building volume greater than Buckingham Palace?
Alternatively, does John Brooks quote a source that does not have a clue about basic maths?

Manicbeancounter

April 17, 2013 at 8:01 am · Reply

I think this paper does not stack up. I worked as a management accountant in industry for 25 years. One thing I learnt early on when estimating or forecasting was to sense-check the estimates. No matter how good your assumptions are, when estimating or extrapolating well beyond the data trend (where there is potential for error), the best check on the data is by reconciling with other data.
From the above

“The SMB of the grounded AIS is approximately 2100 Gt yr−1, with a large interannual variability. Those changes can be as large as 300 Gt yr−1 and represent approximately 6% of the 1989–2009 average (Van den Broeke et al., 2011).”

A gigatonne of ice is equivalent to a cubic kilometre of water. If the land ice volume is increasing, the water must come from somewhere. Nearly all of that water needs to come from the oceans.
Now for some basic maths. A gigatonne is a billion tonnes. As water has a relative density of 1.0, a tonne of water (1,000 litres) is a cubic metre. Therefore a gigatonne of water is a cubic kilometre (1000^3 = 1,000,000,000 = one billion).
A further factor to consider is the area of the oceans. According to my Times Concise Atlas, the total area of the oceans and seas (excluding the enclosed waters like the Dead Sea and Lake Baykal) is 325,000,000km^2. A cubic kilometre of water added to an enclosed sea of one million square kilometres, would raise the sea level by just 1mm (1000mm x 1000m = 1,000,000mm in a kilometre). So 325km^3 = 325Gt-1 of new ice accumulation above sea level in Antarctica would reduce sea levels by 1mm, or 2100GT-1 by 6.5mm.
Some of the ice accumulation will be on ice shelves, so the impact of 2100GT-1 extra ice per annum extra ice might be to reduce sea levels by just 5mm per annum. Also sea levels might be rising by a little less than the 3.2mm a year that official figures claim, but there is no evidence that sea levels are falling. Further, any net ice melt elsewhere (mostly Greenland) is only adding 1mm to sea level rise. So the rest must be mostly due to thermal expansion of the oceans. I think that the evidence for the oceans heating is very weak and of insignificant amounts. Even Kevin Trenberth in his wildest flights of fantasy would not claim the missing heat (from the air surface temperatures) adds more than 1-2mm to sea level rise.
What this study does show is that by honestly looking at data in different ways, it is possible to reach widely different conclusions. It is only by fitting the data to predetermined conclusions (and suppressing anything outside the consensus) that consistency of results can be achieved.

My scepticism on global warming stems from a belief that scientific evidence is strengthened by being corroborated from independent sources. Honest and independent data analysis means that wildly different conclusions can be reached. Comparing and contrasting these independent sources leads me to believe that the public face of the global warming climate change consensus massively exaggerates the problem.

Kevin Marshall

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6 Comments

  1. Bob

     /  17/04/2013

    Surface Mass Balance is the amount of new snow, it is not the same as Total Mass Balance. Nova has misled you.

    Reply
    • manicbeancounter

       /  18/04/2013

      Could you explain (or point me in the direction of) how changes in Surface Mass Balance can differ from Total Mass Balance. At the fringes of Antarctica I can appreciate that there will be some melt. So whilst the total new snow, continent wide, might be increasing, the Total Mass of snow/ice might be stable or decreasing as, for example old snow/ice diminishes on, say, the warming Antarctic Peninsula. Like with sea levels and ice melt, I like to be able to reconcile the numbers.

      Reply
  2. Bob

     /  18/04/2013

    And sorry to disappoint. The Zwally “paper” is actually just a presentation, not peer reviewed published in a journal.

    A recent peer reviewed paper (that included Zwally) found Antarctica was losing mass.

    http://www.sciencemag.org/content/338/6111/1183.abstract

    Reply
  3. Kirk Shaw

     /  14/05/2013

    During cold-climate intervals, known as glacial epochs or ice ages, sea level falls because of a shift in the global hydrologic cycle: water is evaporated from the oceans and stored on the continents as large ice sheets and expanded ice caps, ice fields, and mountain glaciers. Global sea level was about 125 meters below today’s sea level at the last glacial maximum about 20,000 years ago (Fairbanks, 1989). As the climate warmed, sea level rose because the melting North American, Eurasian, South American, Greenland, and Antarctic ice sheets returned their stored water to the world’s oceans. During the warmest intervals, called interglacial epochs, sea level is at its highest. Today we are living in the most recent interglacial, an interval that started about 10,000 years ago and is called the Holocene Epoch by geologists.

    Reply

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