# Ice cores and ozone holes **URL:** \ **Category:** Factual Questions\ **Created:** [May 20, 2007, 6:02pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831 "2007-05-20T18:02:41Z")\ **Posts on this page:** 19\ **Page:** 1
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 20, 2007, 6:02pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/1 "2007-05-20T18:02:41Z")
My search-fu appears to be somewhat lacking… Do the results from ice cores around the world correllate with regard to atmospheric bubbles? E.g. do the ice cores from (say) the Himalayas correllate with those from Greenland and the Antarctic? What do the Antarctic cores say about the Antarctic ozone hole? Likewise Arctic ones? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [May 20, 2007, 6:39pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/2 "2007-05-20T18:39:31Z")
Glaciers, as in the Himalayas, are “rivers of ice”" that move downslope and melt at their terminal end. Hence glacial ice is usually not all that old (although the glacier itself may have existed for a long time). To get an extended climate record you need ice that has been in one place for a very long time, as in the ice caps of Greenland and Antarctica. Atmospheric bubbles in ice cores are used to look at past levels of gases such as carbon dioxide in the atmosphere, not the “ozone hole,” which concerns mainly the uppermost levels of the atmosphere. The ozone hole is only a few decades old so long ice cores wouldn’t be necessary to study it in any case. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 20, 2007, 6:53pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/3 "2007-05-20T18:53:49Z")
> [@](#): > > The ozone hole is only a few decades old so long ice cores wouldn’t be necessary to study it in any case. I think the idea is to test the hypothesis that ozone holes are a cyclic natural phenomenon. If there were evidence of an ozone hole ten thousand years ago, for instance, that would imply that they’re not strictly anthropogenic. And even though ice cores don’t sample the atmosphere at ozone height, it’s still conceivable that they might carry some indicator of surface UV levels, which would in turn be an indicator for the thickness of the ozone layer. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [May 20, 2007, 7:08pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/4 "2007-05-20T19:08:06Z")
[QUOTE=Chronos] I think the idea is to test the hypothesis that ozone holes are a cyclic natural phenomenon. If there were evidence of an ozone hole ten thousand years ago, for instance, that would imply that they’re not strictly anthropogenic. And even though ice cores don’t sample the atmosphere at ozone height, it’s still conceivable that they might carry some indicator of surface UV levels, which would in turn be an indicator for the thickness of the ozone layer. [/QUOTE] Are you aware of any such studies, or hypotheses, or are you just speculating? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 20, 2007, 7:12pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/5 "2007-05-20T19:12:08Z")
I don’t know whether it’s ever been addressed in the scientific literature, but I have seen the speculation in the popular press. Unfortunately, I can’t recall any specific instances. Regardless of the source, though, it’s a testable scientific hypothesis. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [May 20, 2007, 7:16pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/6 "2007-05-20T19:16:08Z")
[QUOTE=Chronos] Regardless of the source, though, it’s a testable scientific hypothesis. [/QUOTE] What kind of signature, specifically, would you expect to find in ice cores regarding past UV levels? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [May 20, 2007, 8:38pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/7 "2007-05-20T20:38:59Z")
> [@](#): > > What kind of signature, specifically, would you expect to find in ice cores regarding past UV levels? Specifically, I don’t know if there are any, or what they would be if there were. I said it was a testable hypothesis, not an _easily_ testable hypothesis. If nothing else, we could test it by ceasing all production of halogen compounds, waiting a few millenia, and seeing if the hole is still around (which would still be easy, compared with, say, testing the String Model). ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 20, 2007, 8:39pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/8 "2007-05-20T20:39:06Z")
[QUOTE=Colibri] The ozone hole is only a few decades old so long ice cores wouldn’t be necessary to study it in any case. [/QUOTE] Don’t you mean, ‘we have only known about it for a few decades’? Anyway, the questions were mostly seperate. What concerns me for the first question is that we have several widely seperated areas with long-standing ice - I thought there was such in the Himalayas as well as the glaciers, but colour me educated - so if we’re looking at data from one source, we should be able to corroborate it with the other sources. I’m remembering that with dendrochronology they can date wood pretty accurately by looking at the tree rings and thinking that something similar might be doable with ice cores. If we can’t corroborate (as in not technically possible rather than the data does not corroborate) - or haven’t - then surely ice core data should be classed as unreliable? But my search-fu is lacking on this. Are we drawing all sorts of conclusions from unverified data? Secondly, with regard to the ozone holes, it might be one reason why the ice cores do not corroborate, but if there were a consistent and logical mismatch, then we could deduce when and where the ozone hole was. But perhaps there are insufficient ice core sample locations? ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [May 20, 2007, 9:15pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/9 "2007-05-20T21:15:30Z")
[QUOTE=Quartz] Don’t you mean, ‘we have only known about it for a few decades’? [/QUOTE] No. We know it didn’t exist a few decades ago. ---
**Author:** ![scotandrsn](https://avatars.discourse-cdn.com/v4/letter/s/a4c791/32.png) [@scotandrsn](https://boards.straightdope.com/u/scotandrsn)\ **Post date:** [May 20, 2007, 9:16pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/10 "2007-05-20T21:16:34Z")
One could presume that the fact that the majority of the scientific community regards ice core data as reliable evidence indicated that the correlation has already been proven solid, and not presume that they make a habit of wild speculations. But then again, I’m not impressed with the academic rigor of a lot of science in other areas I see in the last decade or so, so evidence is always welcome. [This article from the American Chemical Society](http://pubs.acs.org/hotartcl/est/99/apr/learn.html) from nearly a decade ago seems to give a fairly simple yet detailed overview of the methodology and interpretation of ice cores. maybe you can use it to inform yourself enough to decide if the data correlates to your liking. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 20, 2007, 9:41pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/11 "2007-05-20T21:41:09Z")
[QUOTE=Colibri] No. We know it didn’t exist a few decades ago. [/QUOTE] [Cite.](http://www.antarctica.ac.uk/Key_Topics/The_Ozone_Hole/) But that doesn’t mean that there weren’t earlier holes. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [May 20, 2007, 9:43pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/12 "2007-05-20T21:43:54Z")
[QUOTE=Quartz] But that doesn’t mean that there weren’t earlier holes. [/QUOTE] What is your hypothesis for why they would have existed? What mechanism do you propose? ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 20, 2007, 9:48pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/13 "2007-05-20T21:48:48Z")
[QUOTE=scotandrsn] [This article from the American Chemical Society](http://pubs.acs.org/hotartcl/est/99/apr/learn.html) from nearly a decade ago seems to give a fairly simple yet detailed overview of the methodology and interpretation of ice cores. [/QUOTE] Now, that’s good stuff. Thank you. So, we have only three survey sites in Antarctica. > [@ACS](#): > > Greenland cores do not date back as far as those from the Antarctic high plateau, although recent drillings date to the last interglacial, the Eemian (135,000-115,000 years ago). However, because of greater snow accumulation and less compression of the ice, the climatic history of the Northern hemisphere ice sheets is preserved with a years-to-decades resolution in contrast to the century-to-millennial scale resolution of the Antarctic cores… Greenland also receives considerably more dust than Antarctica. This actually answers my first question: it’s not actually possible to directly correllate the ice cores from Greenland and Antarctica, but indirect correllation can be done. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 20, 2007, 9:51pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/14 "2007-05-20T21:51:06Z")
[QUOTE=Colibri] What is your hypothesis for why they would have existed? What mechanism do you propose? [/QUOTE] I have no hypothesis that they did or did not exist. I’m simply asking the question. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [May 20, 2007, 10:12pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/15 "2007-05-20T22:12:33Z")
[QUOTE=Quartz] I have no hypothesis that they did or did not exist. I’m simply asking the question. [/QUOTE] Ice cores have shown that [solar flares](http://space.newscientist.com/article/dn11456-solar-superflare-shredded-earths-ozone.html) caused ozone depletion in 1859. However, this is a completely different mechanism than that involved in the creation of the present ozone hole. The cause of modern ozone depletion is pretty well understood at this point to be chlorofluorocarbons, which are human-produced. Naturally occuring sources of chlorine, such as volcanoes and oceans, produce it in a form that is easily washed out of the atmosphere, in contrast to CFCs, which persist. Unless it can be established that there was some natural source of CFCs in the past, earlier episodes of ozone depletion would have little relevance to this one. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 20, 2007, 10:21pm UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/16 "2007-05-20T22:21:03Z")
[QUOTE=Colibri] Ice cores have shown that [solar flares](http://space.newscientist.com/article/dn11456-solar-superflare-shredded-earths-ozone.html) caused ozone depletion in 1859. [/quote] And that’s #2. I wonder if ice cores show other, earlier depletions? ---
**Author:** ![scotandrsn](https://avatars.discourse-cdn.com/v4/letter/s/a4c791/32.png) [@scotandrsn](https://boards.straightdope.com/u/scotandrsn)\ **Post date:** [May 21, 2007, 12:08am UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/17 "2007-05-21T00:08:02Z")
[QUOTE=Quartz] Now, that’s good stuff. Thank you. So, we have only three survey sites in Antarctica. This actually answers my first question: it’s not actually possible to directly correllate the ice cores from Greenland and Antarctica, but indirect correllation can be done. [/QUOTE] However, ice cores are not the only climatological record we have. [This article](http://www.sciam.com/article.cfm?articleID=00020983-B238-1384-B23883414B7F0000) about a core from a couple of years ago mentions the fact that the marine sediment record matches fairly well with ice core records. It also mentions some other interesting information. > [@](#): > > Analysis of this core shows that current atmospheric concentrations of CO2–380 parts per million (ppm)–are 27 percent higher than the highest levels found in the last 650,000 years. > > The ice core data also shows that CO2 and methane levels have been remarkably stable in Antarctica–varying between 300 ppm and 180 ppm–over that entire period and that shifts in levels of these gases took at least 800 years, compared to the roughly 100 years in which humans have increased atmospheric CO2 levels to their present high. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [May 21, 2007, 1:28am UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/18 "2007-05-21T01:28:52Z")
[QUOTE=Quartz] What concerns me for the first question is that we have several widely seperated areas with long-standing ice - I thought there was such in the Himalayas as well as the glaciers, but colour me educated - so if we’re looking at data from one source, we should be able to corroborate it with the other sources. I’m remembering that with dendrochronology they can date wood pretty accurately by looking at the tree rings and thinking that something similar might be doable with ice cores. If we can’t corroborate (as in not technically possible rather than the data does not corroborate) - or haven’t - then surely ice core data should be classed as unreliable? But my search-fu is lacking on this. Are we drawing all sorts of conclusions from unverified data? [/QUOTE] When you talk about corroborating the data, are you talking about the dating of the layers? As I understand it, that can be corroborated with dates of known volcanic eruptions - ash residues of the right composition are found in the layers we would expect to find it if our assessment of the age is correct. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [May 21, 2007, 6:50am UTC](https://boards.straightdope.com/t/ice-cores-and-ozone-holes/404831/19 "2007-05-21T06:50:04Z")
[QUOTE=Mangetout] When you talk about corroborating the data, are you talking about the dating of the layers? As I understand it, that can be corroborated with dates of known volcanic eruptions - ash residues of the right composition are found in the layers we would expect to find it if our assessment of the age is correct. [/QUOTE] The excellent link **scotandrsn** supplied shows that this cannot be done to the same degree of accuracy.