I spent some time looking at sea ice trends in the antarctic. The point is to verify whether the plots of Steig’s recent paper are within the bounds of reason. After all rising temperature in the antarctic west should lead to decreases in the cyclic sea ice. I used the NASA Team montly gridded sea ice data to which is presented in a 316 x 332 element grid for 30 years. Each sea pixel can of course contain ice values vs water at one time or another, I used only pixels which had at least 12 months of ice in them for the last 30 years.
After the gridded data was collected I fit a linear trend to each pixel to look at where ice is being gained and lost across the antarctic.
The green square represents the zero trend color value greener is ice growth, redder is loss over 30 years — As you can see the majority of the sea ice area in the antarctic has been expanding. The next graph below is the same as the one above with red and green separating the positive and negative ice growth rate to give a better visual cue.
Compare the above graph with the temperature reconstruction presented by Steig et. al.
West Antarctica warmed between 1957 and 2006 at a rate of 0.1760 deg C per decade (95% confidence interval).
Today, I’ll make my first statement of skepticism about Steig et. teams conclusion. It seemed logical before because the rest of the earth is warming, yet it seems to me they are claiming far too much warming for the ice trend. I just don’t believe the sea ice would continue to expand in a situation of strong average atmospheric temperature increases. Nearly all of the Antarctic sea ice vanishes in the summer months. What’s more, in areas of known well measured temp rise (the peninsula) ice has decreased as expected.
In the antarctic, new ice is formed at a rate determined by water and air temperature. If air temperature rises and sea ice is known to expand, that means we need a drop in sea temperature to more than compensate for the atmospheric rise in the same timeframe. If you drop sea temperature, we all know first hand what happens to the surrounding land (la Nina anyone). It just isn’t making sense to me right now.