Comments on: Icebergs are hotspots for life

By: Daniel J. Andrews

Daniel J. Andrews — Wed, 20 May 2009 04:17:16 +0000

Thanks Ed Y. I figured something like that happened. No biggie. It was mainly a drive-by comment as I usually only discuss climate on climate blogs where real experts will comment on things too (learn a lot that way). I’m a biologist not a climatologist so I’m sure a real climatologist would have worded things differently (caveat emptor, in other words).
I got sucked into the climate thing while doing my graduate work in the Arctic and I spent several years doing a crash course in climatology as it relates to ecology.
btw, I see you had lunch with Sir David Attenborough. I am supremely overwhelmingly jealous. He also fueled my love for the natural world from way back and I owe him more than I can ever say.
-dan (ex-pat brit canuck)

By: Ed Yong

Ed Yong — Tue, 19 May 2009 11:24:47 +0000

Daniel – the spam filter didn’t like the multiple links in the original comment. I’ve restored it now. Thanks for chipping in.

By: Daniel J. Andrews

Daniel J. Andrews — Tue, 19 May 2009 05:31:05 +0000

Ed S…I posted a reply a couple of days but since it had links in it, it is being held up. I pointed out, among other things, that ice extent around Antarctica is not at historic highs. Google Cryosphere Today. Your statement may have been true in 2004-2007, but not now.
In addition, the Steig et al paper published in Nature this past January on Antarctic warming also addresses some of your points. If you don’t have subscription access to Nature, check realclimate where they have two posts on this paper…since they’re climatologists I’m sure you’ll find them more reliable than Joe/Jane blogger.
The link between warmer air holding more moisture and precipitating out as snow when the air hits hits land and increasing snow volume/ice extent is discussed either in those posts or the comments (or perhaps the paper itself…can’t remember now but I’m sure you’ll be able to find it as this is quite a common discussion topic, having been known for well over a hundred years).

By: Ed Snack

Ed Snack — Tue, 19 May 2009 01:54:03 +0000

Uh, Deltoid, ho ho ho, you be quoting Tim Lambert as an authority ? True, extent doesn’t (necessarily) equal mass, but you have signally failed to demonstrate the opposite, or that there is more precipitation and hence more ice. The original statement is just “knee jerking”.

By: Brian Schmidt

Brian Schmidt — Tue, 19 May 2009 00:26:59 +0000

Ed Snack: No. Extent doesn't equal mass. Even if it did, more precip could increase mass and still have more melting and bergs. Here for more: http://scienceblogs.com/deltoid/2009/05/the_australians_war_on_science_38.php

By: Daniel J. Andrews

Daniel J. Andrews — Mon, 18 May 2009 03:02:38 +0000

Apparently the ice area around Antarctica is not at historical highs although the trend in sea ice coverage is upwards. See official sea ice area graph here:
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/current.area.south.jpg
For the year 2008 it seems the ice extent was close to the 4th or 5th lowest amount since 1979 (but this may or may not be relevant as I explain below). The years 2004-2007 though did have some historical highs.
From the authors of a paper in Nature about Antarctic warming…
…”while sea ice in Antarctica has been increasing on average, there have been significant declines off the West Antarctic coast for the last 25 years, and probably longer”
If you don’t have a subscription to Nature you can get a summary (by the authors) here:
http://www.realclimate.org/index.php/archives/2009/01/state-of-antarctica-red-or-blue/
And an update here:
http://www.realclimate.org/index.php/archives/2009/02/antarctic-warming-is-robust/
As you can see from the papers increase in ice extent is not necessarily incompatible with warming and increased melting. Warmer air holds more moisture which results in more snowfall which can increase ice coverage if accumulation is faster than melting. It still may be melting faster than ever but if precipitation is heavier than before the ice sheet will grow. That means you can have more ice melting into the oceans at the same time the ice is increasing.
So (increased) ice melting around Antarctica is not incompatible with a greater ice extent, which is not incompatible with global warming, and thus the statement is indeed factual.
Ice extent around Antarctica being at historical highs is currently NOT a factual statement. Two years ago it would have been…but not now. And as pointed out, even if it was currently factual it would not contradict the warming trend measured.
—-
Sometimes there is confusion over “historical sea ice extent” when people refer to different measurements. Are they referring to sea ice extent or sea ice thickness? Or perhaps seasonal ice or perennial ice? On what part of the continent? Eastern, western, interior, perimeter?
For example, in the Arctic there was much ado last year about how great an area was covered by sea ice. That was seasonal ice though and was much thinner. Its extent is based on the temperature and weather from that particular year, and not from any long term trends. A cold year will give you more seasonal ice. A warm year will give you less seasonal ice. Just as a few cold years and greater ice extent is not indicative of global cooling neither is a few warm years and less sea ice indicative of global warming. That is weather, not climate.
The much more important measurement is the amount of perennial ice (thick ice) because the variations seen in that ice reflect longer term trends. Arctic perennial ice has been declining for decades. That is climate, not weather.
Naturally the Arctic is ocean surrounded by land and the Antarctic is land surrounded by ocean so the two poles will react differently to changing climate. One may lose its ice, one may gain, or eventually both may lose but the southern pole may lag by decades or centuries. We live in interesting times.

By: Ed Snack

Ed Snack — Mon, 18 May 2009 00:00:31 +0000

You are aware, aren’t you, that the ice extent around Antarctica is at historical highs ? I mean, before making a statement like “As the ice around Antarctica melts in the face of global warming…” wouldn’t it be simple to check if that is a factual statemen ? Yes, some shelves around the Antarctic peninsula have broken up, but that represents a tiny minority of Antarctic ice.

By: Lilian Nattel

Lilian Nattel — Sun, 17 May 2009 23:30:35 +0000

That’s so interesting–and also a little hopeful.