Polar Radar for Ice Sheet Measurements
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Special Report: More Questions And Answers
Do you stay on the ship when you come into various stations, or is there space for you to stay at Davis?
Timing of the major resupply varies from station to station but generally the same pattern applies at each station from year to year. At Davis for example we prefer to do the resupply in the spring time - this is when the fast ice near the station is very strong and consistent and as this ship has the strength to break through the sea ice here and get to within a few kilometres of the station. At Davis the ship is ‘parked’ firm up against the fast ice and vehicles can drive right up to the side of the ship and take on or deliver cargo using the ship’s crane.
The ice alongside the ship at this time of the year is about 1.7metres thick usually with a layer of about 25cm of snow on top. This is strong enough to land quite a large plane on, for example a C130 Hercules!!! It is certainly strong enough to drive large vehicles on - skidders and loaders and bulldozers and big trucks - there is absolutely no danger walking on it. The only parts which can be dangerous are immediately next to and toward the back of the ship - the engines keep working and the propeller at the back keeps circulating the water so it does not freeze up against the stern and stop the propellers and rudder from working - because then we would be in trouble. The other danger area is where the fast ice is up against the shore or an island. This is where the tide cracks are and the ice may not be very strong. Tide cracks? Just because the ocean surface is frozen doesn’t mean we don’t have tides. The whole ice sheet in fact rises and falls in the same tidal pattern as anywhere else in the world’s oceans. It is where the rising and falling of the sea ice next to the fixed land mass causes the edge to break and split.
At Mawson the situation is very different - they have an excellent harbour and provided the sea ice has ‘broken out’ the ship can go right into the harbour and the cargo only has to travel about 200metres to the station - barges are used to carry the cargo from the ship to the shore where cranes lift the cargo onto trucks on the shore. But at Mawson the sea ice generally does not break out till the latter part of January or toward mid February - in the late summer - so that is when resupply takes place. At Casey it is a bit like Mawson but the harbour access is not as good but resupply is still best undertaken in the summer when the sea ice has broken out. At Macquarie Island there is no ice problem and resupply is traditionally carried out in the late spring or early summer - it is also a watercraft exercise.
The third element is the deployment and recovery of summer people. This is largely dictated by decisions very early on as to how long people need to be at stations to do their work and which part of the season is the best for it. For example people who might need to take ice core samples from lakes need to be there before the ice on the lakes gets too soft or melts - their trip might thus be a short one at the beginning of the season. For people doing a major study of glaciers they might not be able to get to the location till mid season but will remain till the very end. People studying penguins might need to be there just before the start of the breeding season but remain till the time the chicks have been born and have become healthy juveniles.
Well, that it for now. I look forward to more questions so I can share this experience with you all.
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