Since this years sea ice failed to be a record min (how careless of it) there is a sense of furtive scurrying around looking for something else; and DSB is looking at record thin instead: Sea ice in the Arctic Ocean has melted to its lowest volume in recorded history, according to new measurements they say on 7th october. Interesting.
Volume implies measuring thickness. But while measuring area from satellite isn’t too hard (people have been doing it routinely for years, and there are problems, especially when its wet, ahem, but still no-one is too worried), measuring thickness is much harder. Here is some stuff; note that it suffers badly from over-PR-ing in its abstract: though only about measurements it feels obliged to vapour on about prediction. What you can’t get from just that abstract is that measuring the thickness via altimetry is rather imprecise, especialy when the ice is thin: something like 0.5m accuracy at best. You can also try to “measure” thickness via microwave emission and guessing the ice temperature and estimating heat flow and modelling and hence guessing thickness; this is also imprecise. Or you can measure it by sonar from submarines; this doesn’t give you enough coverage; or drilling holes; this is even worse.
No matter. Lets follow the DSB trail, to http://dsc.discovery.com/news/2008/10/07/arctic-sea-ice.html?dcitc=w01-101-ae-0003. The headline is “Arctic Ice Thinner Than Ever Despite Cold Winter” but the text is “the ice may be thinner than ever.” And that leads you to http://dsc.discovery.com/news/2008/08/27/arctic-sea-ice.html . And that, in its turn, says f*ck all about ice thickness.
Backing up one, we have Walt Meier of National Snow and Ice Data Center in Colorado and colleagues say the overall ice volume in the Arctic Ocean is at least as low as 2007, they say, and may even have dwindled more by as far as 10 percent. but no link to a source or any data. And The latest measurements are preliminary, though they seem to confirm Zwally’s suspicions. However he stressed that scientists will have a better handle on the situation later this year, once the data are in from the ICE Sat satellite, which is currently taking readings of ice thickness from orbit.
Hmmm.
Walt Meier’s home page leads to http://nsidc.org/data/seaice/ which doesn’t mention thickness.
Ah well. Its quite likely the ice was thin this year: first year ice usually is, and there was a lot of first year ice about. But don’t believe the “measurement” tag, unless people are prepared to point oyu towards the actual measurements.
