21 November, 2003
Sea Ice School
Due to its location and weather, Antarctica’s surrounding ocean water freezes. This ice, which is very different from glaciers, is called sea ice. Throughout the year the amount of sea ice waxes and wanes. When the sea ice is at its maximum, the continent nearly doubles in size compared to its minimum. About what time of year would the sea ice be at its maximum? (Hint: Remember, we’re in the southern hemisphere!)
Besides temperature, other things affect the structure and stability of the sea ice including: tidal pulls, ocean currents, icebergs, and pressure from moving glaciers. Humans can also impact sea ice stability. How might we have affected the sea ice? These activities put cracks in the ice. Too much pressure and the crack increases, resulting in open water. As winter progresses, cracks in the ice begin to “heal”, or refreeze. This new layer of ice is much softer and therefore not as stable. The healing cracks, often covered by blown in snow, result in an invisible danger to humans. Many a people have fallen into the ocean when driving over or crossing a healing crack. Therefore, anyone working on the sea ice, or on/near the frozen lakes of the dry valleys must attend sea ice school. The goal is to teach us the locations that are prone to problems and give us the skills necessary to determine if it is safe to cross.
Sea ice that is less than 30 inches in depth is cause for concern. When the sea ice depth is less than 30 inches, you can only safely travel 1/3 the distance of your vehicle’s track/footprint. If the thin ice spans a distance that is larger than 1/3 of your vehicle's track, you need to find an alternative route.
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