Submitted by Anonymous on Wed, 12/22/2010 - 05:57
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Oden Antarctic Expedition 2010

Greetings People of the Oden Antarctic Expedition 2010, My name is Justin W from Mr. Peneston's 9th grade class. Following your blogs, i have a question about the melting of the top ice layers and snow layers stacked on top of the ice possibly causing rising water levels. As the ice melts, water builds up during the "summer" if Antarctic has a summer season. then when the freezing period comes, the water freezes over. but my question is, as the water re-freezes, and makes heavier ice, would that, and with the snow layers on top of the ice layers, could that cause water underneath the ice layers to rise, and have that freeze over. Would the rising water and freezing of it cause the ice layers to get gradually bigger and bigger?

Wed, 01/05/2011 - 14:47

Anne Marie Wotkyns

Hi Justin,
Your question is a good one and relates very well to some important physical principles. First, sea ice, regardless of how much there is or how thick it is, is already in buoyancy equilibrium with the sea water. You probably remember the neat experiment of adding ice and water to a drinking glass until the glass is filled to the brim. As the ice melts the glass never overflows. So the same quantity of frozen sea water in the sea ice is the same quantity when the ice melts. You raised an interesting point about the snow on sea ice. The snow is coming from water in the atmosphere, and so when it accumulates and then eventually melts in the summer it does raise (just a tiny tiny bit) sea level.
However, when we lose glacial ice from off the continent, like when the ice shelves collapse, that does raise sea level when it melts, because that ice was never in the water to begin with.
So, the annual freezing and melting of sea ice around Antarctica will never significantly change sea level. Only the melting of the continental ice can do that. But changes in the thickness and extent of sea ice (how far out from the continent it forms) does have a very important role in climate. This would be a great topic for you to research and explore.
Thanks for the question,
Blake Weissling