Monday, February 11, 2013

Question Place

Ok, looks like life is moving in a more blog-friendly way.  So I'll hang out the shingle again for your questions, suggestions, comments.

In the mean time, I'll note a few additions and losses.  Among the losses is that the blogger widget for showing the 10 most recent comments is broken.  You can still subscribe to the comments.  My notes about sites which seem to be inactive, but which have material you can still read and is worth reading, are now a 'page' -- one of the tabs near the top of the page, so a loss and an addition. 

Also added to the tabs near the top are "The Simplest Climate Model", and "What is Climate?", which collect in one place, finally, the several posts I've made on each topic.  There'll be more.


Anonymous said...

Hi! Someone posted a link to at Tamino's place, and since one of your papers was cited, I was wondering if you could comment:

Basically, I want to know what the "consensus" view of pre-1979 Antarctic sea ice is. I reviewed several AR5 WGI chapters, and commented several times that they had omitted any discussion of the subject, and pointed at the couple of papers I could find (sadly, I hadn't seen the TAR figure, or that would have made a good citation): but random papers based on whaling records, spotty satellite data, and other somewhat unreliable proxies can be dangerous to rely on without real knowledge of the subject material.

So, um, could you do a post on pre-satellite Antarctic sea ice? I'd be really interested!


Anonymous said...

Ack. Recaptcha may have eaten my comment.

Basically, I was hoping you might be willing to do a post on pre-satellite Antarctic sea ice - I noticed that you were cited in, but I don't know of any assessments post-TAR that have addressed the question...



Robert Grumbine said...

That's third AR, and, unfortunately, my contribution to the sea ice record is in the more recent span. If I remember correctly, for 3AR, it is 1997-(then)present (2001).

The pre-1979 Antarctic sea ice record is more than a little problematic. As you say, whaling records and unreliable proxies. The one microwave satellite prior to 1979 is the ESMR from 1973-1976. That doesn't extend the record much, but, given the tremendous decline in Antarctic ice extent shown in the 3rd AR's curve for 1973-76, it's an important period.

Much of what you're seeing there is a decision about what to do regarding the giant Antarctic polynya ESMR saw. If you believe ESMR, there was a huge area of open water in the eastern Weddell Sea, which, correspondingly, means great reduction in the extent of Antarctic ice, on the whole, from the 3AR curve. The 3rd AR curve, as it is, is based on disbelieving ESMR. There are reasons to do so. But, then again, there are reasons to believe it. If you credit the ESMR record, there's no great decline in ice extent in the 1970s.

This puts me in mind of an experiment I had in mind to do on the blog. So, more to come.

Going before 1973 in the Antarctic gets very difficult indeed. Few people went down there for any reason. Among the few types are the whaling and the sealing ships. But such captains had reason to fake their records -- so that competitors wouldn't know where they were getting their catches if they stole the log books. So, what, exactly, is in the books is a question as well.

What would be very, very nice is a proxy of some sort (snow fall rates on the continent?) that correlated well with Antarctic ice extent. As far as I know, nothing with good time resolution has been found. Sodium and/or chlorine levels in Antarctic ice cap is connected to the sea ice extent, more or less. But that's a more or less, and time resolution is poor.

n.b.: Sodium and/or chlorine show up in Antarctic ice cores. It's from small salt water droplets evaporating from breaking waves, and the tiny salt crystals being blown to the continent. If the ice edge is farther away, more of the time, then you get fewer such crystals. On the other hand, if it's windier, you get more wave breaking and more salt crystals also. So a dual signal, which makes life more difficult for figuring what's really going on. Not impossible, since there are other markers in the ice cores, some of which are not affected by ice extent -- such as dust. (The dust comes from continents, far outside the sea ice pack. So it's a purer signal of how windy it is.)

Anonymous said...

Thanks! I appreciate the insight regarding TAR vs. ESMR, and I look forward to the "experiment" you have in mind!


Robert Grumbine said...

You actually don't need quotes around experiment. It's going to be some real experimenting. At least real as one gets with satellite data :-)

Steve Bloom said...

And how about that Arctic sea ice just now, Bob? In the first year of the "Maslowski window" a (near-) complete loss still seems unlikely, but prospects for it happening by 2016 appear very good indeed (as determined by my non-scientist finger in the wind). The cracking is pretty amazing.

What do you think?

Robert Grumbine said...

Well, I was unhappy with Wieslaw that he never published in the professional literature the basis for the infamous 'as early as 2013' comment. Then again, way, way too much has been made of the 2013 aspect -- and ignoring the fact that this was the extreme early end of the range he was mentioning.

I still don't know that I'd go for as early as 2016, but the estimate I created a while back (2035, 7 year standard deviation) is looking increasingly like an extreme upper bound. I knew at the time that I was making an upper bound guess. But it's getting plausible that this could be wrong by ... a lot more than I was thinking.

The cracking that's being observed ... well, it's hard to say how to take it. Some years ago a friend was having back trouble. This lead, naturally, to an MRI scan of her back. It showed that several of her disks were drying out/getting thinner/.... On the one hand, she _was_ having back trouble. On the other hand, the surgeon noted that this (dry/thinning disks) is an issue that has only become apparent now that we had ways of observing it prior to surgery (the enhanced MRIs). The mechanics of sea ice ... well, we have a lot to learn about them. But among the several ways of viewing it are some which suggest that the natural state of the Arctic ice pack is to develop cracks when strong storms hit it. Only recently have we had satellites that could look closely enough to see the cracking on large scale.