4. When do we get to see a Glacier?

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The title is from the 2002 voyage and was one of the Naturalist, Jane's, favourite 'silly questions'. The other is, while seated in a zodiac: "How high above sea level are we?" The only response to this is: "Put your head in the water so you can taste it, and then follow it in"!
Anyway, back to the glaciers. A much better question would, of course, be: "When do we not see a glacier?", because they are indeed almost everywhere. The hills and valleys slope down to the sea and there are snow-covered cliffs of one to one hundred meters all around us. Although not on the scale of the 40km wide Lambert Glacier that feeds the Amery Ice Shelf, we have to call this glacial ice because it contains those cracks and grottoes that are so intensely blue. This is a sign that the ice is old and compressed by the weight of snow and ice above it and is slowly flowing to the sea. But why is it so blue?
Apparently, as the pressure increases the air bubbles are compressed and forced into the crystal lattice of the ice. But it doesn't take much pressure because those of us who climbed the hill at Paradise Bay in 2002 would have noticed that the snow was blue at the bottom of a 30cm foot print. So, as I struggled up, I remember wondering if the blue colour was due, or partly due, to, ozone. After all, if you compressed two volumes of oxygen and one volume of water vapour - dry because it is below freezing - you could get one volume of hydrogen peroxide, which freezes at -0.4 degrees centigrade, and one volume of ozone. So you'd finish up with about one third the volume that you started with. But where would the energy come from to initiate this reaction? Almost certainly from sunlight, although the atmosphere does filter out the more energetic wavelengths. Certainly, hydrogen peroxide has been found in ice cores so it is presumably a remnant of this reaction. But, as far as I know, ozone has not been found so perhaps it reacts with water vapour to give more hydrogen peroxide and oxygen if the pressure is high, or two molecules of ozone give three molecules of oxygen if the pressure is reduced. So, could some of the blue colour in the ice come from ozone? It seems possible to me as I've made ozone in the lab by subjecting oxygen to pressure and an electric discharge and it looks blue just like my foot prints! But there's no doubt that the compressed ice and water vapour absorb more of the red wavelengths of the visible spectrum so that the compressed snow just looks blue. And yet, if the blue colour is just due to the absorption of the red wavelengths, why does the deep blue colour sometimes occur in discrete horizontal layers? One would have thought that the pressure would increase fairly uniformly with height in a vertical ice cliff. So perhaps when those horizontal layers were laid down the sun was shining and the pressure was just right for ozone and hydrogen peroxide formation........
At last I'm at the top and stand there panting just happy that there is still some oxygen available for me! And I try to absorb one of the great treasures of Antarctica: those intense and varied blue hues that can be seen in almost every ice cliff and iceberg - wherever I look.

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Photos

4.1 A Glacial Foot
The end of this glacier was at least 30 metres high and contained a deep blue grotto.

4.2 An Iceberg with a Chasm
The chasm in this iceberg went right through.

4.3 At the edge of newly formed pack ice
Tabular icebergs can also be seen in the distance.

4.4 The Foot of another Glacier
Some passengers from the Polar Pioneer can be seen in the foreground.

4.5 A Tabular Iceberg near Brown Bluff
Discrete horizontal blue layers can be seen in this iceberg.