Diatom Ice

It's the afternoon of November 13th. I'm back in McMurdo and very happy to finally post blogs I wrote last week. This is one is from November 3rd.

So, I noticed when we first started shooting off the air cannon to conduct the seismic survey, some of the ice that came up with the sea water and air bubbles looked it was formed from root beer. Here’s a more scientific description: irregularly shaped chunks of translucent ice ranging in size from approximately three to eight inches in length with mottled internal yellowish brown coloring. I know from the scientists here with ANDIRLL that the coloring is colonies of diatoms. Diatoms are plants that are about the size of the head of a pin and are made of silica (a sand-like substance). Most of the diatom ice slides back into the hole with the receding sea water when the air gun ceases firing. Hopefully, the diatoms go on living and no harm done.

One morning when we arrived at the survey line to begin our day, I noticed a chunk of diatom ice on the surface of the area of the last hole we shot from the afternoon before. It had sat out in the bright sunshine all night. Instead of the usual brownish color I’ve become used to, it was a lovely shade of green. I took a photo of it lying on the aqua colored sea ice with the toes of my “bunny boots” (seriously, that’s what these boots are called-why, I don’t know!) to prove to everyone that Antarctica isn’t only shades of white.

Here’s a science question for you; why was it green now and not still brownish? Why is that important? To test my hypothesis of why that happened, I collected some other pieces of brown diatom ice and left them out in the sun by the last hole of the day. My prediction was that they would be green the next day. My prediction was correct. When we came back the next morning they were green. For comparison I collected another piece of brown diatom ice and photographed them next to each other. The brown ice is the piece on the left.

So, what’s happening with the diatom ice? And why is it important?