Watts Up With That? Antarctic Sea Ice Complete Video by Jeff Id , reposted here by invitation. The video animation Jeff put together is well worth watching, see it below the “read more” line. – Anthony Figure 1 - Wilkins Ice Shelf - A map of the Antarctic Peninsula with the location of the the Wilkins Ice Sheet, which is on the southern portion of the peninsula. Credit: British Antarctic Survey Antarctic temperatures and sea ice are becoming quite a hobby. It should make for some interesting discussion around the campfire this summer – not really. It takes my computer about 15 hours to calculate this movie and it took all day to figure out how to make the movie work. Actually it takes a minute then wait, then a minute and wait again. I finally got a reasonable quality video at 15 frames per second, one frame per day from 1978 – 2009. Before you watch the video Figure 1 is a map of the Wilkins ice shelf which apparently is about to melt every hot January summer at the south pole. The melting of the Wilkins ice shelf has happened over and over prompting numerous articles like the following. Wilkins Ice Shelf About to Break Off and Alter the Map of Antarctica Vast Antarctic Ice Shelf on Verge of Collapse The headlines are truly endless and will continue this year as well. Here is a video which is particularly pertinent in it’s discussion and the fact that it ends with a discussion of climate science by Hillary Clinton. I recommend it to everyone before watching the video below. Wilkins Ice Shelf Collapse Video Below is a plot of the sea ice area anomaly in the antarctic calculated from the NSIDC NasaTeam algorithm data. It shows an upward trend in sea ice extent over the last 30 years. I’ve pointed out here many times that the trends do in fact exist if the even if the statistical certainty created by typical high frequency climate activity can create a trend of the same magnitude. This is an important differentiation which certain ‘over the top’ scientists in AGW crowd tend to blur. Statistical certainty of a trend does not always mean the trend does or does not exist, a trend is a trend to the certainty of the measurement error (different than certainty created from other noise). Some global warming bloggers like to blur that distinction. The interpretation of a trend’s meaning does change with the statistical certainty of the trend. In the case of Antarctic sea ice growth I have seen one example demonstrating the trend is statistically significant despite climate noise. However the point of ice shrinking or growing is to interpret the consequences of a trend with regards to global warming. When interpreting the consequences of ice growth or shrinkage in my opinion the arbitrary significance threshold and linear trend has little meaning. The annual variance of the sea ice is shown in Figure 3. Below is a link to a video file of the Antarctic sea ice trends for 30 years. Figure 4 – Antarctic Sea Ice Video – Click to play What’s really interesting about the video is the clockwise rotation of the ice which becomes especially visible during maximum extent. Another interesting point is the peninsula acts as a shelter to the ice on its leeward side. The Wilkins shelf get’s blasted by air and water currents every year from the south in this image, once we understand that combined with in the CNN video (link above) the reason the ice bridge exists is obviously due to protection from ocean and air currents by a small island (look at the angle of the ice bridge in the CNN video compared to current flow). The Island has protected this very small piece of ice from cracking for some time probably because the amazing circularity of the Antarctic continent doesn’t experience very large current changes. I’ve watched the above video a dozen or so times (wouldn’t you after a day’s work) I noticed that there does appear to be a change in weather patterns in more recent years as the upward flow below the peninsula cuts away at the maximum ice extent on the West side of the image. The same is true for the East side of the image. I had the advantage of doing a trend by pixel plot previously which led me to look for the effect. The plot done by myself in a previous post using a slightly older version of the same data is shown in Figure 5. The loss of ice on the West and East sides of the Antarctic is visible as blue pixels at the extreme edges of the range. Its difficult to imagine after watching this video that this ice shelf hasn’t collapsed (or whatever it’s called) and re-formed in the last several hundred years, more than once. Remember the ice from the shelf forms on land and flows out to sea. Either way, considering the natural variation of Antarctic sea ice, can we really say the current Antarctic ice trend or the change of an ice shelf in such a tiny area has a powerful meaning for the future of Earth? If you missed the Arctic version of the video the link is here: Arctic Ice VideoNew Antarctic Sea Ice Video – shows cycles and ice growth
Thursday, July 2, 2009
Figure 2
Figure 3
The huge annual variation dwarfs any apparent trend with the signal dropping to near zero every year. The thermal inertia of the ice creates a smooth cyclical process allows us to make pretty anomaly plots like Figure 2 but trend wise there isn’t much to say. So I guess I’m fired from my budding climatology career again. The reason they have little meaning becomes apparent in the wildly dynamic sea ice video presented below.
Now consider that each pixel of the Antarctic ice data is 25 km and in the video of the Wilkins ice shelf, the crack is 40miles long – that is about 2.6 pixels in the Figure 4 video.
Figrure 5 – Antarctic sea ice trend by pixel
Thursday, 2 July 2009
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