Two steps forward, one step back
By the way: How accurate are these satellite estimates of ice thickness?
Update: Related comment thread at Small Dead Animals here.
This particular transect is full of backwards drift – so it feels like climbing up a ‘down’ escalator. We’ve all chosen to be here and nobody’s complaining, but things are tough at the moment. Each day we aim to work our way north, inch by inch, trying to push as far north as possible. At the end of a 10 hour sledging day we put up the tent and have our supper but the cold is all consuming and refuses to go away. I lie in my sleeping bag and close my eyes but it’s so bitterly cold that I’m always half-awake, shivering. All I can think of is that while I’m lying here we’re constantly drifting southwards. All that effort, day-in, day-out, but when we stop to rest we’re being carried back the way we’ve come and it’s completely beyond our control. It’s soul destroying.Questions: Are they still constantly measuring the ice thickness, like they said they were going to do? And if so, how useful is that data, if the ice is constantly moving around?
By the way: How accurate are these satellite estimates of ice thickness?
And in recent years the overflying satellites have themselves used a neat trick to estimate thickness by measuring the height of that portion of the ice which sticks above the water.
As nine-tenths of the ice lies below the water line, a simple calculation will provide a good grasp of the likely thickness.
But none of these approaches is perfect. It is impractical to do direct measurements everywhere; and the broader satellite method depends on there being cracks in the ice to see the water surface, and in any case relies on a number of assumptions, including the density of the ice.
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3 comments:
an amusing thread over at SDA on this topic
http://tinyurl.com/d4onwq
They don't have to measure anything. If they return they will solemnly declare that AGW is destroying the polar ice caps. blah blah blah
how useful is that data, if the ice is constantly moving around?
Well assuming our explorers are honest brokers then we draw a line from the edge of the ice to the pole and measure the ice thickness plus the distance from the pole. Next year repeat the exercise. Of course two years is weather, only a long trend is climate so they actually have to repeat this every year for say 30+ years. I'm not even sure this is long enough given the fact that twentieth century periods of fall (ie pre 1970s) and rise (ie. post 1970s) were of similarly length. Perhaps they need to repeat this for 60+ years.
On the other hand we will be able to determine whether this is politically motivated by the press coverage that accompanies their return. If the papers claim that a trend can be detected from a one point graph we will know it's not science.
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