Graph of the Day: September ice melt Bad, But July and August were the Real Story

September 19, 2011

As I noted in a recent post, Arctic Sea ice has not been cooperating with denialist’s insistence on a “recovery”.

Real Climate had a nice post earlier in September, before we had the minimum number. Dirk Notz wrote -

A rainy summer might be one reason for an apparent lack of public attention with respect to the ongoing sea-ice loss. Another reason, however, is possibly the fact that we scientists have failed to make sufficiently clear that a major loss of sea ice during the early summer months is climatologically more important than a record minimum in September. This importance of sea-ice evolution during the early summer months is directly related to the role of sea ice as an efficient cooling machine: Because of its high albedo (reflectivity), sea ice reflects most of the incoming sunlight and helps to keep the Arctic cold throughout summer. The relative importance of this cooling is largest when days are long and the input of solar radiation is at its maximum, which happens at the beginning of summer.

If, like this year, sea-ice extent becomes very low already at that time, solar radiation is efficiently absorbed throughout all summer by the unusually large areas of open water within the Arctic Ocean. Hence, rather than being reflected by the sea ice that used to cover these areas, the solar radiation warms the ocean there and thus provides a heat source that can efficiently melt the remaining sea ice from below. In turn, additional areas of open water are formed that lead to even more absorption of solar radiation. This feedback loop, which is often referred to as the ice-albedo feedback, also delays the formation of new sea ice in autumn because of the accompanying surplus in oceanic heat storage.

Measurements from ice buoys show that indeed melting at the bottom of the sea ice has increased significantly in recent years. While field experiments that were carried out in the 20th century showed unambiguously that surface melting used to be the dominant mechanism for the thinning of Arctic sea ice, now in larger and larger areas melting at the underside of the ice is almost equally important. Such melting from below is particularly efficient since the temperature at the ice-ocean interface is fixed by the phase equilibrium that must be maintained there. Hence, any heat provided by the ocean to this interface will lead to thinning of the ice in summer and to slower ice growth in winter. At the surface, the ice temperature is not fixed as long as the ice isn’t melting, and heat input from the atmosphere can in part be compensated for by a change in surface temperature and an accompanying change in outgoing long-wave radiation at the ice surface.

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8 Responses to “Graph of the Day: September ice melt Bad, But July and August were the Real Story”

  1. mrsircharles Says:

    Yeah. Climate change deniers want to sell us a 3 or 4 day rise in arctic sea ice coverage as a “recovery”. That’s ridiculous at the least.

    Here the graph for arctic sea ice volume => http://farm6.static.flickr.com/5100/5722990097_d378795bf8_z.jpg

    “Recovery” my arse!

    • daveburton Says:

      No, Charles, what is ridiculous is:

      1. Alarmists deliberately and repeatedly misunderstanding what Steven Goddard actually meant and said, even after I explained it to y’all. I’ll try again:

      Back in June, the 2011 sea ice level was frequently at or near record daily lows for the date, but in July it recovered to well above 2007 levels. That’s the “recovery” that Goddard was talking about. Now (two months later) Arctic ice extent is ~360,000 sq-km above 2007 levels (according to NSIDC), or ~550,000 sq-km above 2007 levels (DMI), or ~300,000 sq-km above 2007 levels (Breman), or ~1,200,000 sq-m above 2007 levels (NORSEX). And,

      2. Alarmists citing synthetic, model-generated, pseudo-data for Arctic sea ice volume (where no real data actually exists), as if it were actual measurements, like sea ice extent. And,

      3. Alarmists making excited press releases about impending catastrophe when a 1 day fluctuation in Arctic sea ice coverage leads to a statistically insignificant “record low” excursion according to just one of the several major sea ice extent reports, and confirmed by none of the others.

      4. Alarmists harping on Arctic sea ice, which fluctuates considerably due to wind and weather, pretending each of its downward fluctuations are due to climate, and largely ignoring sea ice elsewhere, which is less affected by mere wind shifts, and shows no sign of significant decline.

      • BlueRock Says:

        > …Arctic sea ice volume (where no real data actually exists)…

        Another ‘mistake’ from our busy little denier.

        * “Satellite radar altimetry (Giles 2008) and satellite laser altimetry (Kwok 2009) find that Arctic sea ice has been thinning, even in 2008 and 2009 when sea ice extent showed a slight recovery from the 2007 minimum.” http://www.skepticalscience.com/Has-Arctic-sea-ice-recovered-intermediate.htm

        > …sea ice elsewhere … shows no sign of significant decline.

        It’s almost as if this denier doesn’t have a clue or is lying:

        * Accelerated Antarctic ice loss from satellite gravity measurements, 2009. http://www.nature.com/ngeo/journal/v1/n2/abs/ngeo102.html

        • greenman3610 Says:

          submarine and satellite measurements of ice thickness over 5 decades –
          Kwok and Rothrock 2009
          “Within the data release area (DRA) of declassified submarine sonar measurements (covering 􏰓38% of the Arctic Ocean), the overall mean winter thickness of 3.64 m in 1980 can be compared to a 1.89 m mean during the last winter of the ICESat record— an astonishing decrease of 1.75 m in thickness. Between 1975 and 2000, the steepest rate of decrease is 􏰑0.08 m/yr in 1990 compared to a slightly higher winter/summer rate of 􏰑0.10/􏰑0.20 m/yr in the five-year ICESat record (2003– 2008). Prior to 1997, ice extent in the DRA was >90% during the summer minimum. This can be contrasted to the gradual decrease in the early 2000s followed by an abrupt drop to <55% during the record setting minimum in 2007. This combined analysis shows a long-term trend of sea ice thinning over submarine and ICESat records that span five decades."

          http://rkwok.jpl.nasa.gov/publications/Kwok.2009.GRL.pdf


  2. The trend is simply down

    its an observation that can easily be seen. Until there is a significant recovery back to pre 2007 levels- anything that suggests otherwise is denial- lets move on- an accept that the arctic is warming.

  3. otter17 Says:

    The potential change in northern hemisphere weather patterns due to sea ice loss is what seems to pique the interest of people I talk to.

    We shall see what happens over the years. I remember the winter of 2007/2008 quite well; it was weird in my neck of the woods.


  4. […] of arctic ice cover (what’s left of it). You can see his excellent posts here and here. The short version of the arctic sea ice story […]


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