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Would an ice have formed if the Arctic Ocean was not enclosed?

  1. Oct 19, 2009 #1
    This is hypothetical question, but it does go the ability of polar ice caps to form and survive. Years ago I read about a computer simulations of a planet with a single circular continent centered on the north pole extending to the 30th N parallel. The continent was entirely flat with an altitude 500m.The rest of the planet was ocean. The simulation assumed an otherwise entirely earth-like planet based on 1990 data. I think the article was in Scientific American but I don't remember the title or author(s). I've not found anything like this on the web.

    The simulation showed a fairly small north polar summer ice cap, extending only to 85 N and a huge but thin winter ice/snow cap from just a centimeter to about 1-2 meters thick varying according to expected precipitation, latitude and time of day. It extended almost to the coast. However, the floating southern ice cap was huge all year around, ranging to about 40 S in winter to 50 S in summer. (I remember the numbers because I tried to do my own simulation).

    I was surprised that the simulation showed such a large ice cap could form in an open ocean with no land to act as a source or "seed'. I would have thought that currents would have broken it up.

    The article (as I recall) suggested that the summer Arctic ice pack would be more stable and larger if it were not surrounded by continents. A look at the actual ice pack from daily satellite data (the cryosphere today.com) shows that shrinkage is greatest in the West Arctic (toward the Bering Strait) where the ocean is in minimal contact with the Pacific, and least in East Arctic where there is greater contact with the Atlantic. However, the eastern Arctic ice pack is also closer to the pole.

    We can't change geography, but I wonder if a floating ice pack would have formed in the Southern Hemisphere if Antarctica did not exist?
     
    Last edited: Oct 20, 2009
  2. jcsd
  3. Oct 20, 2009 #2

    Xnn

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    30 Degrees north lattitude is someplace like Austin Texas.
    However, that's at only 150m elevation.

    Anyhow, Antarctica is very differant than the Arctic since it's at something like 7,500 foot elevation and much colder. My impression is that the reason the southern hemisphere sea ice maximum extent is currently so much larger than the north is because there is much more cold air generated by the Antarctic continent.

    Of course currents, both atmospheric and ocean can transport heat from the tropics to the poles or cold from the polar regions. My understanding is that ocean currents are not modeled very well by most climate models. Some of the older models assumed the oceans were just simple slabs. So, a 1990 era climate model might not have included much for ocean currents.

    If that were the case, then sea ice may be able to form at around 45 degree latitude.
    Of course, the limit for sea ice is also dependant on greenhouse gas concentrations. If I recall correctly, during the last glacial maximum, permanent sea ice formed as far south as Long Island and Spain (40 degree North). However, right now, it's looking iffy for summer sea ice to exist at the North pole in another 30 years.
     
  4. Oct 20, 2009 #3
    That is partially correct. Because the continent is covered with ice year round, this sets up conditions over SH winter for ozone depletion in the spring. Ozone is a potent GHG that absorbs both long and short wave radiation.
     
  5. Oct 21, 2009 #4
    The simplistic base model I described of a single supercontinent centered on the north pole serves to set up a series of modifications which can be evaluated in terms of their effect on the simulation. So instead of a smooth circumferential coastline at 30 N, one substitutes a sinusoidal coastline so that the coast may vary from, say, 20 N to 40N. The effect of the modification on a severe monsoonal continental climate is then evaluated. One then evaluates the effect of, say, topographical changes to replace the flat landscape, etc. The basic idea is to evaluate the effects of the configuration of land/water surfaces on climate in a systematic way while holding basic climactic factors constant (like atmospheric CO2).

    The usual thinking has been that a continental climate will lend itself to the formation of large thick ice caps (Greenland, Antarctica), while a marine climate will not. Antarctica extends to about 70 S on average. What if instead it extended to 30 S; a single huge supercontinent in the Southern Hemisphere? The simulations indicated that the permanent ice cap would shrink drastically or (in my simulation) disappear entirely, all other things being equal. The reason would be sharp reduction of marine influences in the continental interior. The result is a tendency toward extreme seasonal effects on temperature and precipitation; very hot summers up to high latitudes and very cold but very dry winters. Strong monsoons would allow summer rains to penetrate into the interior (mostly convection storms) maybe up to 45 S but the high latitudes would be extreme deserts. Any lasting ice/snow could only occur on higher mountains. Any low altitude snow/ice might not survive the summer even at the pole.

    Now suppose instead that there is no continent at all. Instead of Antarctica, there is no land at all south of, say, latitude 60 S. Given the present and recent history of the Earth (ice age glacial advances and current recession), would a floating southern ice cap exist or would the ocean be entirely ice free? Would a floating ice cap have formed even at the height of the ice age 20000 years ago?
     
    Last edited: Oct 21, 2009
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