Thursday, November 20, 2008

Dirty Ice

One goal of our project is to determine the impact of sedimentation on marine organisms along western McMurdo Sound. In a nutshell, large amounts of sediment are blown out of the Taylor Valley onto the sea ice at Explorers Cove; this sediment accumulates on the multi-year ice in the Cove, as seen in the aerial photo below. (Yes, that's what the ice at Explorers Cove looks like from 500 ft. up!)

This massive amount of sediment is ultimately deposited into the sea by various processes. Under certain conditions, we suspect that sediment is episodically dumped onto the seafloor, burying marine organisms in ways that may preserve them as fossils. The results of our studies should provide a better understanding of the fossil record in this region of Antarctica.

Wind-blown sediment accumulates around structures on the sea ice, particularly the various types of cracks that form. These cracks range in size from tiny thermal cracks (seen above) to more massive tide cracks. The sediment grains trapped by these cracks absorb sunlight and help melt the ice. Freeze/thaw cycles and solar radiation, compounded by the multi-year nature of the ice, lead to the beautiful, treacherous ice topologies that our shins, chins, and tailbones are now encountering.

Compare the smooth surface of first-year ice at our Bay-of-Sails camp site (above) to the ten-year-old ice at Explorers Cove.

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