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Swift
2010-Aug-18, 07:07 PM
From National Geographic (http://news.nationalgeographic.com/news/2010/08/100816-global-warming-antarctica-sea-ice-paradox-science-environment/)

Climate scientists have cracked the mystery of why Antarctic sea ice has managed to grow despite global warming—but the results suggest the trend may rapidly reverse, a new study says.

Satellite data show that, over the past 30 years, Arctic sea ice has declined while Antarctic sea ice has mysteriously expanded, according to study leader Jiping Liu, a research scientist at Georgia Tech in Atlanta.

"We've seen this paradox, but we don't know why—here we gave an explanation," Liu said.

The new analyses are based on climate models and sea-surface temperature and precipitation observations from 1950 to 2009. They show that, in the 20th century, ocean warming boosted precipitation in the upper atmosphere over the Antarctic region, which fell as snow.

More snow made the top layers of the ocean less salty and thus less dense. These layers became more stable, preventing warm, density-driven currents in the deep ocean from rising and melting sea ice.

The work is being published in the Proceedings of the National Academy of Sciences.

HenrikOlsen
2010-Aug-18, 10:03 PM
So, very simplified: the increase in Antarctic sea ice is yet another symptom of global warming, rather than an argument against it?

jlhredshift
2010-Aug-18, 10:20 PM
So, very simplified: the increase in Antarctic sea ice is yet another symptom of global warming, rather than an argument against it?

Yes, but I want to see the paper to see how they calculate the amount of precipitation needed to form the requisite halocline.

Ivan Viehoff
2010-Aug-19, 09:46 AM
I'm sure I've seen an explanation for this before, a year or two ago. Maybe it's the same explanation, and it has just taken time for it to progress from early research being discussed in public to a published paper. All I recall from the earlier one was reduced mixing of layers of water, I don't recall the mention of precipitation. Perhaps they had first identified the reduced mixing, reported on this, and now have published an explanation for it.

lomiller1
2010-Aug-19, 05:48 PM
So, very simplified: the increase in Antarctic sea ice is yet another symptom of global warming, rather than an argument against it?

It was never a good argument against global warming because direct measurement showed this area is warming (both air and water IIRC). This makes the implied argument that “there is more sea ice so the it must be cooling” moot, as we already knew it's not the case. The question of why it is happening is still of interest, but isn't needed to discount claims the region is cooling.

Ari Jokimaki
2010-Aug-20, 05:16 AM
I'm sure I've seen an explanation for this before, a year or two ago. Maybe it's the same explanation, and it has just taken time for it to progress from early research being discussed in public to a published paper. All I recall from the earlier one was reduced mixing of layers of water, I don't recall the mention of precipitation. Perhaps they had first identified the reduced mixing, reported on this, and now have published an explanation for it.

You probably saw it in this forum because I have previously linked to this paper on the same subject:

Increasing Antarctic Sea Ice under Warming Atmospheric and Oceanic Conditions - Zhang (2007) (http://journals.ametsoc.org/doi/abs/10.1175/JCLI4136.1) (full text is freely available in the linked abstract page)

The model shows that an increase in surface air temperature and downward longwave radiation results in an increase in the upper-ocean temperature and a decrease in sea ice growth, leading to a decrease in salt rejection from ice, in the upper-ocean salinity, and in the upper-ocean density. The reduced salt rejection and upper-ocean density and the enhanced thermohaline stratification tend to suppress convective overturning, leading to a decrease in the upward ocean heat transport and the ocean heat flux available to melt sea ice. The ice melting from ocean heat flux decreases faster than the ice growth does in the weakly stratified Southern Ocean, leading to an increase in the net ice production and hence an increase in ice mass.

Canis Lupus
2010-Aug-20, 05:28 AM
Another computer model result? I really must get into computer gaming. It appears to be the new reality.

Ara Pacis
2010-Aug-20, 05:49 AM
It was never a good argument against global warming because direct measurement showed this area is warming (both air and water IIRC). This makes the implied argument that “there is more sea ice so the it must be cooling” moot, as we already knew it's not the case. The question of why it is happening is still of interest, but isn't needed to discount claims the region is cooling.

Many people think of ice and water as a binary condition, without realizing there is a spectrum of temperature to be considered. They often fail to realize that ice can warm up and still be below the melting point.

Ari Jokimaki
2010-Aug-20, 10:10 AM
Another computer model result? I really must get into computer gaming. It appears to be the new reality.

Appeal to ridicule is a logical fallacy (http://en.wikipedia.org/wiki/Appeal_to_ridicule).

Moose
2010-Aug-20, 02:33 PM
Another computer model result? I really must get into computer gaming. It appears to be the new reality.

Canis Lupus, if you wish to dispute GW or AGW, you must do so in the ATM forum. Otherwise, please hold the snide comments.

William
2010-Aug-20, 02:51 PM
The Antarctic Ice Sheet has been cooling. Why?

Is that good news or bad news?

The average temperature on the ice sheet is roughly -40C. The average Antarctic ice sheet thickness is 1.5 kilometers. Air cools within increasing elevation.

0.5C cooling or 0.5C warming of the Antarctic ice sheet. Is that a concern?

http://en.wikipedia.org/wiki/Climate_of_Antarctica



In a paper published in the journal Nature in 2002, Doran et al. reported overall cooling over Antarctica. This study concludes there has been "a net cooling on the Antarctic continent between 1966 and 2000, particularly during summer and autumn."[2]

Chapman and Walsh, (2007) in the paper published by Journal of Climate collected temperature in and around Antarctica from 460 locations including 19 manned surface observation stations located on the continent, 73 automated weather stations, and the 2° latitude by 2° longitude gridded sea surface temperature time series. They found little change in temperature over Antarctica in last 50 years (apart from the Peninsula). From the beginning of record until about 1965 they find slight warming, since 1965 slight cooling: "Trends computed using these analyses show considerable sensitivity to start and end dates with starting dates before 1965 producing overall warming and starting dates from 1966 to 1982 producing net cooling rates over the region."[5]

Monaghan et al. (2008) in the paper published by Journal of Geophysical Research, similarly finds that "prior to 1965 the continent-wide annual trends (through 2002) are slightly positive, but after 1965 they are mainly negative (despite warming over the Antarctic Peninsula)."[4]

HenrikOlsen
2010-Aug-21, 12:24 AM
It was never a good argument against global warming because direct measurement showed this area is warming (both air and water IIRC). This makes the implied argument that “there is more sea ice so the it must be cooling” moot, as we already knew it's not the case. The question of why it is happening is still of interest, but isn't needed to discount claims the region is cooling.
"Never a good argument" didn't prevent William from just using something like it to argue against GW.
Even with a deliberate elision of "sea".

Solfe
2010-Aug-21, 04:48 AM
I take in a great deal of what I consider to pop-culture science; no scientific papers, no journals, etc. Just the plain old news stand coverage of many different scientific topics. Global warming as a topic is very important and therefore ever-present. This has almost nothing to GW other than GW seems to be THE topic that receives what I consider to be a detrimental treatment by authors consistently. I feel that I am completely missing out on GW discussions and facts, due to silly mistakes made by authors.

My objection to this author and many others is typified by this quote:

"We've seen this paradox, but we don't know why—here we gave an explanation," Liu said.

I know Dr. Liu is trying to be engaging and interesting, I know there were 10 sentences before and 10 after this one that we don't see. I am sure it is accurate to that Dr. Liu actually said otherwise it wouldn't have been in quotes. But can this statement be logically broken down easily and does this statement lend anything to the article? My contention is it is a very off the cuff thing to say and needs to be framed in a better way if used.

As I read and reread that one sentence, it comes across as "This situation is absurd and no one knows why, so let me just throw something out there, stop reading here", instead of the friendly and colloquial way the speaker meant. Liu is a researcher with a message that he/she feels needs to be heard, so he/she has chosen a voice that is friendly. A voice that the author eliminated by poor choices. After this quote, there is no warmth, no details, no facts about the speaker.

Also, the author has not used the speakers personal title, described their demeanor, given any setting information or used any gender queues in the article. I looked up Liu and discover he or she is a PhD. I had to dig through an Apache server test page given as a reference in the article to find out who Liu was, I didn't care to search far enough to determine if Liu is male or female. Obviously, if the author gave a dead link to the subject's internet page, they were not thinking of the subject speaker at all; why use a quote that is clearly humanizing and friendly if it isn't going to be incorporated into the piece?

I seriously think the author of the article though that "paradox" was a cool, science-y sounding word and that would be a great warm up for the reader before relaying the great scientific content of the article. You can be warm and hard hitting at the same time with a good plan; but if you don't plan on doing both, don't introduce one then switch to the other.

I wish this was the only place I saw this type of mistake being made, but it seems to be rather common.

end of rant...

God. I hope someone else is bothered by this sort of thing, and that it isn't some insanity particular to me.

Solfe

Ari Jokimaki
2010-Aug-21, 05:34 AM
Since William brought up the temperatures of Antarctic, I just point out that the cooling William suggests is going on is a result of cherry-picking the existing scientific literature. Worst example of this is the quote from Monaghan et al. (2008) (full text here (http://polarmet.osu.edu/PolarMet/PMGFulldocs/monaghan_bromwich_jgr_2008.pdf)) in William's post. This was what William presented:

Monaghan et al. (2008) in the paper published by Journal of Geophysical Research, similarly finds that "prior to 1965 the continent-wide annual trends (through 2002) are slightly positive, but after 1965 they are mainly negative (despite warming over the Antarctic Peninsula)."[4]

However, when consulting the Monaghan et al. paper, we see that this quote is from Monaghan et al. introduction where they describe earlier research on this subject. This particular quote in full is:

The finding of increasingly negative trends in the most recent decades is corroborated by Chapman and Walsh [2007]; they perform a gridded objective analysis of Antarctic near-surface temperatures and note that prior to 1965 the continent-wide annual trends (through 2002) are slightly positive, but after 1965 they are mainly negative (despite warming over the Antarctic Peninsula).

So it wasn't Monaghan et al. finding the quote was about. In fact, when Monaghan et al. own results are consulted, we see that they found recent warming from Antarctic, this is from their abstract:

The subtle shift toward warming during the past 15 years raises the question of whether the recent trends are linked more closely to anthropogenic influences or multidecadal variability.

The latest research on Antarctic temperatures finds warming (above mentioned Monaghan et al., 2008; Steig et al., 2009 (http://www.mitosyfraudes.org/Calen/Steig_et_al_Nature_Antarctica_Temps_1-22-09.pdf); Gillett et al., 2008 (http://www.cccma.ec.gc.ca/papers/ngillett/PDFS/ngeo338.pdf)). In addition to that, Antarctic ice sheet has been observed to lose mass at an accelerating rate (Velicogna, 2009 (http://thingsbreak.files.wordpress.com/2009/10/increasing-rates-of-ice-mass-loss-from-the-greenland-and-antarctic-ice-sheets-revealed-by-grace.pdf); Chen et al., 2009 (http://www.nature.com/ngeo/journal/v2/n12/full/ngeo694.html)).