Friday, December 26, 2008

Beacon Valley

The last stop of our field season is Beacon Valley which is an E-W striking Valley of 900 to 1200 m elevation. In the east it is bounded by the Taylor Glacier, in the west it is constraint by mountain ridges (e.g. Mount Feather) which hold back the ice flows from the Antarctic Ice Sheet. Beacon Valley has two different types of ice. In its upper part buried glacial ice is overlain by a thin layer of sublimation till and soil. Further down towards the Taylor Glacier ice cement is the common type of ground ice. Debris covered glacier originating from nive's in Mullen and Friedman Valley flowing into Beacon Valley. The picture above shows a view from the helicopter above Mount Feather into Beacon Valley; it shows the flow of debris covered glacier from side valleys into Beacon Valleys and Taylor Glacier in the east. In Beacon Valley we have two camp sites one at the Taylor Glacier and one about 6 km further up Valley. The Taylor Glacier (below) creates a 20 m ice cliff and provides us with ice for melting drinking water.

In Beacon Valley surfaces are older than in Victoria Valley and rocks which have been scoured by wind for thousands of years form ventifacts (see below).

The wind also removes the fine sand from the surface leaving behing wind scoured smaller rocks which form desert pavement as shown in the picture below. This desert pavement protects the soil before further wind erosion.

Saturday, December 20, 2008

Victoria Valley

From Taylor Valley we moved to Victoria Valley which is further north at an elevation of 400m. Victoria Valley has two glacier at either end and there is evidence that it was covered by a very large lake about 10,000 years ago. We also have a climate station here and we will drill in the permafrost to investigate the nature of the ice in the ground.
It is much dryer in Victoria Valley than in Taylor Valley. Snow only occurs occasionally in polygon cracks and depressions. The polygonal pattern ground in Victoria Valley is very impressive. Some of the polygon shoulders are 1 to 1.5 m high.

In addition to taking long cores we also use a small rock drill to take samples from the upper 15 to 20 cm of the groundice. The picture below shows Ron and David opening a pit at the shoulder of a polygon from which they retrieve a small ground ice core (see second picture below). The ground ice here occurs in two different forms: as ice cemented sand and pure ice (light part). Ice cemented sand has only small fraction of ice and consits mostly of sand while the pure ice contains only little or no sediment.

The last days we have strong katabatic winds which generate on the Antarctic Ice Sheet. They warm up due to increasing atmospheric pressure from the Ice Sheet (3000 m elevation) to the valley at 400 elevation; temperature increases can be 10 to 20 degrees. The lenticular cloud in the picture below indicats the winds.