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The following is an archived discussion of a featured article nomination. Please do not modify it. Subsequent comments should be made on the article's talk page or in Wikipedia talk:Featured article candidates. No further edits should be made to this page.

The article was promoted by Sarastro1 via FACBot (talk) 20:30, 22 September 2017 [1].

Ice core

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Nominator(s): Mike Christie (talk - contribs - library) 16:26, 26 August 2017 (UTC)[reply]

This article is about one of the key tools of palaeoclimatology. Ice cores contain an extraordinary amount of information about past environments. I am not an expert on this topic, but have done a fair amount of reading and I think the article covers the ground fairly thoroughly, and is ready for FAC. Mike Christie (talk - contribs - library) 16:26, 26 August 2017 (UTC)[reply]

Image review

Thanks for the review. Mike Christie (talk - contribs - library) 16:57, 26 August 2017 (UTC)[reply]

Support on prose per my standard disclaimer. Well done. As always, feel free to revert my copyediting. These are my edits. - Dank (push to talk) 23:14, 26 August 2017 (UTC)[reply]

Support Comments by Pbsouthwood

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A fascinating read, and accessible to an ordinary engineer (can't speak for the general public). A little heavy going towards the end at a single sitting, but my eyes get tired after a while when nitpicking. I also spent a bit of time referring to linked material, and noticed a few places where extra links would be nice if available, otherwise some explanation would help. • • • Peter (Southwood) (talk): 12:18, 27 August 2017 (UTC)[reply]

Done. • • • Peter (Southwood) (talk): 19:45, 29 August 2017 (UTC)[reply]

Lead:

Structure of ice sheets and cores:

  • does not become denser with additional pressure - Why, then, is there a crystal structure change at about 1500m?
    I've cut this, since I can't find an unequivocal statement that it is the case; the pages I was using to source this discuss the thinning but never explicitly say that it doesn't get denser. I think it's probably WP:OR to make the statement, and it's probably technically not true since there must, as you say, be at least a slight difference for there to be a crystal structure change. When brittle ice relaxes there is no significant visible change in its volume, so the density can't change by more than a tiny fraction; the point I was trying to make was that the major changes in density are with the transition from snow to firn to ice. Mike Christie (talk - contribs - library) 11:14, 27 August 2017 (UTC)[reply]
    OK, Not a problem.• • • Peter (Southwood) (talk): 15:40, 27 August 2017 (UTC)[reply]
  • ... slowly flow outwards, thinning as they do so How is the rate of flow distributed over depth? I assume there is some variation.
    Yes; there's a simplified diagram in Alley that shows the fastest flow at the top; this is because the top layers do the most thinning so they must be flowing faster. The details are apparently quite complex, and Alley glosses over them; I think I have more details in another source but I felt this was too much detail for this article. Perhaps ice sheet could cover it in more detail. Mike Christie (talk - contribs - library) 11:15, 27 August 2017 (UTC)[reply]
    I have added a see also link to Ice-sheet dynamics, which doesn't say much at present, but it is where the information should be. Done. • • • Peter (Southwood) (talk): 15:25, 27 August 2017 (UTC)[reply]
    Agreed; that's a helpful link -- thanks. Mike Christie (talk - contribs - library) 15:51, 27 August 2017 (UTC)[reply]
  • An ice core is a vertical column through an ice sheet which provides a sample of each layer of ice, - It was a bit of a surprise to see this in the penultimate paragraph of this section. Basically this is the definition. I would have expected to see it at one of the first statements about ice cores, possibly even in its own section, possibly the first section. Is an ice core always vertical? Perhaps all the information about ice sheets should be grouped together, and a separate section or subsection on what a core is.
    I see your point, but I'm not sure what the best thing to do about it would be. The reason for that section's structure is that an ice core, and the reasons for retrieving one, aren't comprehensible without knowing about ice sheets and how they are formed. The sentence explaining what an ice core is naturally come after the description of ice sheets, not before. I was hoping that the lead would serve to give the background necessary for this section to seem reasonable. Would it work to move this sentence, edited somewhat, up to start the section? And ice cores are not always perfectly vertical, though they are generally meant to be so; the current EastGRIP core deviated substantially from vertical over this summer and effort was spent to return it to vertical. Mike Christie (talk - contribs - library) 15:49, 27 August 2017 (UTC)[reply]
    That could work. Lets try it.• • • Peter (Southwood) (talk): 19:33, 27 August 2017 (UTC)[reply]
    OK, done. How does that look? Mike Christie (talk - contribs - library) 20:41, 27 August 2017 (UTC)[reply]
    It works well for me. On rereading I think that the 3rd from last paragraph of this section (starting "Cores are often drilled...") would be better as the last paragraph, as this keeps all the physical information about the ice sheet together. If you don't think so, no problem. • • • Peter (Southwood) (talk): 10:25, 28 August 2017 (UTC)[reply]
    Agreed; done. Mike Christie (talk - contribs - library) 09:38, 29 August 2017 (UTC)[reply]
  • I have been trying to find out exactly which phase the cubic ice below 1500m represents. Do you have access to the relevant pages of Alley? The phase diagram in Ice and associated descriptions is not helping me.
    I've wondered about that too, but have not seen an answer in the refs so far. Alley has no more information than I put in the article, but he cites this paper, which has further refs. Let me know if you think there should more about this in the article. Mike Christie (talk - contribs - library) 15:58, 27 August 2017 (UTC)[reply]
    I read the article linked above. It makes no mention of cubic crystal ice, just type II air clathrates which occur in a depth zone around 1500m, where apparently they are relatively stable and presumably have a lower energy state than hexagonal ice (Ice Ih) with bubbles. The clathrate has a cubic structure and higher compression resistance than gas bubbles in ice at higher pressures, so the bubbles and hex ice reform at greater depths. The brittle zone is where the clathrates are, and when they decay after decompression. the ice may develop microscopic cracks. Apparently the clathrate structure is slow to form and decay. The article on Nitrogen clathrate has some of this background.• • • Peter (Southwood) (talk): 19:33, 27 August 2017 (UTC)[reply]
    Perhaps mention in this section that the clathrate zone reverts to hex ice again at greater depths, then when one gets to the section on brittle ice it would be clearer. • • • Peter (Southwood) (talk): 10:25, 28 August 2017 (UTC)[reply]
    The paper linked above doesn't say that, as far as I can see; it talks about hexagonal inclusions. I got the impression that the structure of the ice below the brittle zone wasn't well understood, so I've avoided being specific. Did you have a particular part of that paper in mind as giving additional details? Mike Christie (talk - contribs - library) 09:38, 29 August 2017 (UTC)[reply]
    Since I wrote this I've read Uchida et al. (1994), now cited in the article, which makes things clearer. I think the text I added to the brittle zone section may address this. Mike Christie (talk - contribs - library) 10:15, 29 August 2017 (UTC)[reply]

Coring:

Core processing:

  • When samples are analyzed, an outer layer may be removed to reduce the risk of contamination of the ice during drilling and handling By the time the samples are analysed any contamination during drilling has already occurred. It is no longer a risk.
    Good point; fixed. Mike Christie (talk - contribs - library) 15:49, 27 August 2017 (UTC)[reply]

Brittle ice:

  • The brittle ice ceases eventually, does not look right. How does brittle ice cease? The word relax is used later in the section, and makes more sense, but how does it relax? is it a matter of gas diffusing out of bubbles through the solid ice until internal pressure balances with ambient? If so, an amusing parallel to decompression sickness, one of my interests. If not, does the core expand to reduce internal gas pressure stress? What happens to deep cores with cubic structure? do they transform back to hexagonal? do the clathrate gases form bubbles again?
    Yes, I think the parallel is definitely there, though I'm not clear on the internal crystal mechanics. For "cease", take a look at the diagram at the bottom of page 21, here; it shows that the brittle ice zone is restricted to a certain range of depths, so from the point of view of the drillers, as time goes by, they encounter brittle ice after a way, and then after some more drilling it ceases, and the ice is no longer brittle. Can you suggest clearer wording? How about "As drilling continues to greater depths, the brittle ice zone eventually passed, and the core becomes stable again"? Mike Christie (talk - contribs - library) 16:03, 27 August 2017 (UTC)[reply]
    Looks much clearer, something like that. • • • Peter (Southwood) (talk): 19:33, 27 August 2017 (UTC)[reply]
    Done. Mike Christie (talk - contribs - library) 20:41, 27 August 2017 (UTC)[reply]
    Better.
    The first paragraph of this section suggests that the bubbles are responsible for the brittleness, but I understand correctly, the brittle ice zone is where the clathrates are, and this zone actually has less bubble volume than the less brittle zones above and below it. • • • Peter (Southwood) (talk): 10:25, 28 August 2017 (UTC)[reply]
    Your comment prompted me to dig a little more, and I finally found a paper that unequivocally explains it. I added a few words to the brittle ice zone section; essentially they showed that the brittle ice zone ends when the clathrates begin. The brittle ice zone is the range of depths where the bubbles still exist, and pressure in the bubbles is great enough to crack the ice. Apparently clathrates are extremely stable, so even though Alley says somewhere that they will slowly break down, and bubbles will reappear, the process is too slow to make the ice brittle, while drilling at least. Mike Christie (talk - contribs - library) 10:03, 29 August 2017 (UTC)[reply]

Dating:

  • corrected for the presence of 14C produced directly in the ice by cosmic rays, - Is there anywhere to link to that explains how the 14C is produced?
    I've linked 14C to carbon-14, which talks about atmospheric production of 14C; the mechanism is the same. I could add a footnote if this isn't clear enough to the reader. Mike Christie (talk - contribs - library) 16:08, 27 August 2017 (UTC)[reply]
    A link should be sufficient. The article is not about isotope formation, but it is something I wanted to look up at the time, so we have a sample of at least one for whom it will be useful. • • • Peter (Southwood) (talk): 19:33, 27 August 2017 (UTC)[reply]

Greenland deep cores:

  • North GRIP -> NorthGRIP for consistency?
    Yes, done. Mike Christie (talk - contribs - library) 16:11, 27 August 2017 (UTC)[reply]
  • Is there a Wikilink available for Greenland Ice Sheet Program (GISP)
    It's linked -- it's actually "Project", not "Program", though I have made this mistake myself at least once and there may still be an errant version in there somewhere. It's linked in the lead and again near the end. Mike Christie (talk - contribs - library) 16:11, 27 August 2017 (UTC)[reply]
  • Ref Langway 2008 only has 57 pages, (numbered to 47) in the linked pdf. Page ref in sources is to pages 101 to 117, which may be is correct for original publication, but is confusing. I don't know what the recommended work-around would be. Content claiming Langway (2008), pp. 27–28. as ref (116) is supported on spot check.
    Bleah. That's a situation I've not run into before. Ealdgyth, you're an expert on this sort of thing; what's a good way to handle that? Mike Christie (talk - contribs - library) 16:15, 27 August 2017 (UTC)[reply]
    Maybe the source can be cited as originally published in journal XXX, pages n to m, accessed via YYY website. Not sure of the syntax. • • • Peter (Southwood) (talk): 10:37, 28 August 2017 (UTC)[reply]
    • Langway, Chester C. (2008). "The history of early polar ice cores" (PDF). Cold Regions Science and Technology. 52 (2): 101–117 – via US Army Engineering Corps: Cold Regions Research and Engineering Laboratory.?
      After some more thought I decided WP:SAYWHEREYOUGOTIT applies here, and I've reworked it to point directly to the CRREL report abstract, since that's what I'm actually citing. Mike Christie (talk - contribs - library) 10:15, 29 August 2017 (UTC)[reply]
    Looks like a reasonable solution. • • • Peter (Southwood) (talk): 18:50, 29 August 2017 (UTC)[reply]

Done for now.• • • Peter (Southwood) (talk): 12:18, 27 August 2017 (UTC)[reply]

Pbsouthwood: Barring a couple of queries above, and the source query to Ealdgyth, I think I've responded to everything now. Thanks for the review. Mike Christie (talk - contribs - library) 16:15, 27 August 2017 (UTC)[reply]
Mike Christie, Two more minor suggestions above. They do not affect my support.• • • Peter (Southwood) (talk): 10:30, 28 August 2017 (UTC)[reply]
Thanks for the support; I'll work on those two points this evening. Mike Christie (talk - contribs - library) 10:37, 28 August 2017 (UTC)[reply]
All points now responded to. Mike Christie (talk - contribs - library) 10:15, 29 August 2017 (UTC)[reply]

Criteria list:

  • well-written: By my standards, yes. I leave details of spelling and grammar to others. Comprehensibility and use of appropriate terminology look good to me
  • comprehensive: I have not noticed any major deficits, but I am not an expert in the field.
  • well-researched: Those citations I have checked are good.
  • neutral: No sign of a problem.
  • stable: No recent conflicts.
  • appropriate structure: Simple and logical. Seems appropriate.
  • length: Not too short, not too long.
  • media: Relevant and appropriate. Copyright etc checked by someone else.

Support on this basis • • • Peter (Southwood) (talk): 13:02, 28 August 2017 (UTC)[reply]

Source checks (content supported, no copyright infringement):

  • Ref 102, Langway (2008), pp. 5–6. checks out.
  • Ref 117, Langway (2008), pp. 27–28. checks out.
  • Ref 107, Langway (2008), p. 23. checks out
  • Ref 34, Souney et al. (2014), pp. 16–19. checks out on 3 pre-selected items
  • Ref 37, Souney et al. (2014), pp. 20–21. checks out on 4 out of 5 pre-selected items, Ref 38 may support the other, but was not available to check
  • Ref 36, Sedlacek, Cheryl (December 2004) checks out.
  • Refs 46, An extremely brief reversal of the geomagnetic field, climate variability and a super volcano and 47, Blunier et al. (2007), p. 325., check out on 1 pre-selected item.
  • Ref 38, Uchida et al. (1994), p. 302. Checks out

Support on this basis • • • Peter (Southwood) (talk): 13:02, 28 August 2017 (UTC)[reply]

Comments by RockMagnetist

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I'm not sure if I will have time to review the entire article, but I would like to weigh in on Criterion 1(a). A high standard of writing is expected in FA articles, but I see a lot of the sort of problems that Tony's article warns about. Examples:

  • The only ice sheets are in Antarctica and Greenland, so the statement is inaccurate. How about: An ice core is a core sample from a glacier. Common coring sites include Antarctica, Greenland, and high mountains.
    Changed to "An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier": I think it's better to keep the distinction between glacier and ice sheet, since the sources don't use the terms interchangeably. I dropped the reference to Antarctica and Greenland; it's not important enough to mention in the first sentence of the lead. Mike Christie (talk - contribs - library) 19:38, 2 September 2017 (UTC)[reply]
  • First paragraph, last sentence is a bit wordy. How about: Cores are drilled with hand augers (for shallow holes) or powered drills; they can reach depths of over two miles and contain ice up to 800,000 years old.
    Done -- your wording is much better. Mike Christie (talk - contribs - library) 19:38, 2 September 2017 (UTC)[reply]
  • Next paragraph: plenty of unnecessary words (generally, it should be obvious we're talking about ice): Both the physical properties of the ice itself and of material trapped in the ice it can be used to reconstruct information about the climate over the age range of the core. The ratio of oxygen and hydrogen isotopes in the ice provides information about ancient temperatures; and the air trapped in tiny bubbles in the ice can be analyzed to determine the level of atmospheric gases such as carbon dioxide ... Since heat flow in a large ice sheet is very slow, the borehole temperature is another indicator of temperature in the past. and these sources of information These data can be combined to find the in the best fitting climate model that best fits all the available data.
  • I think the paragraph should be split at "Impurities": Impurities in ice cores may depend on location. ; for example, c Coastal areas are more likely to include material of marine origin, such as sea salt ions. Greenland ice cores contain layers of wind-blown dust that correlate with cold, dry periods in the past, when cold deserts were scoured by wind. Radioactive elements, either of natural origin or created by nuclear testing, can be used to date the layers of ice in the cores. Some volcanic events which that were sufficiently powerful to have distributed send material around the globe leave left a signature in the ice which can be detected many different cores, allowing synchronization of the that can be used to synchronize their time scales between two different locations.

That's the first two (three?) paragraphs. My suggestions are just a start; with more time, I think they could be further improved. Glancing over the rest of the article, I see similar problems, particularly unnecessary repetition of information. I'll do more if I can find time, but I hope this helps. RockMagnetist(talk) 17:40, 2 September 2017 (UTC)[reply]

Thanks for the review; this is very helpful -- it's hard to see the problems in one's own prose. I've made the edits you suggested, with a couple of minor differences. The main one is that I kept "combined to find the climate model that best fits all the available data" rather than changing it to "combined in the best fitting climate model", because I want to retain the sense that the data comes first and that model is constructed to fit the data. I'll go through the rest of the article for wordiness, and I'll see if I can find similar simplifications and improvements.
If you have time to do a more thorough review, both for content and prose, I'd really appreciate it -- I'm not a subject matter expert, and it would be good to get more input from someone with more expertise. Mike Christie (talk - contribs - library) 19:38, 2 September 2017 (UTC)[reply]
I think your take on the climate model is better. I started to edit the first section, but got into an edit conflict with you, so I'll wait for you to have a crack at it. RockMagnetist(talk) 19:54, 2 September 2017 (UTC)[reply]
OK, I'm done for now -- I found more to fix at the start of the article, which I'd like to think is because the prose gets better, but may be just because I started to glaze over trying to critique my own prose. It's all yours. Mike Christie (talk - contribs - library) 20:36, 2 September 2017 (UTC)[reply]
Taking the helm now. One question, though - I notice you said "ice sheet or glacier", but according to the lead of glacier, an ice sheet is just a form of glacier. I'd like to change "ice sheet" to "glacier" through most of the article. Any objections? RockMagnetist(talk) 22:05, 2 September 2017 (UTC)[reply]
I think that would be confusing, but I'll do some looking through sources and report back. As far as I'm aware (with a layman's understanding of the sources I've read) the term "ice sheet" is only used for Greenland and the Antarctic; "glacier" seems to be used to refer specifically to a stream of ice. For example, the Jakobshavn Glacier in Greenland is a moving stream of ice attached to the Greenland ice sheet. The distinction is not used much in this article, but it seems to be real. I'll see if I can find support for one position or the other. Mike Christie (talk - contribs - library) 22:12, 2 September 2017 (UTC)[reply]
Googling for "glossary glaciology" finds this, which unambiguously states that glaciers and ice sheets are different. There's also this, which doesn't define "ice sheet" but defines "glacier" in a way that would seem to exclude ice sheets. Mike Christie (talk - contribs - library) 22:19, 2 September 2017 (UTC)[reply]
Both of those could be read a different way, but I also found a book titled Dynamics of ice sheets and glaciers. Maybe there isn't a consistent terminology. However, most of the material in this article can equally well apply to glaciers or ice sheets, so maybe we need to come up with a compact way of referring to both at once. RockMagnetist(talk) 22:31, 2 September 2017 (UTC)[reply]
  • On a different subject, the citations are fine from a stylistic point of view, but would be easier to use if there were links to the sources using {{sfn}} or {{harvnb}}. That could easily be implemented using global search and replace. Or a more compact presentation could be achieved with {{rp}}. RockMagnetist(talk) 22:39, 2 September 2017 (UTC)[reply]
    I've never worked with either of those styles, and the few times I've edited an article with them I haven't found them intuitive to work with; probably a combination of laziness and inertia on my part. They also don't play well with VE, which is my preferred editor. I've no objection to you or anyone else changing the citations to another style, but it's not something I would do myself. Mike Christie (talk - contribs - library) 11:29, 3 September 2017 (UTC)[reply]
  • In the section on coring, one thing is a little puzzling. You mention electromechanical drills in the first paragraph, and then there is no further mention until you are comparing them with thermal drills. I presume most of paragraphs 2-5 are referring to electromechanical drills - is that true? RockMagnetist(talk) 23:16, 2 September 2017 (UTC)[reply]
    Also, the concept of a string of drill pipe was a little unclear. At first I pictured something that was snaking around the core. RockMagnetist(talk) 23:26, 2 September 2017 (UTC)[reply]
    Not all the material in those paragraphs is relevant only to EM drills; cuttings aren't an issue for thermal drills, but drilling fluids are required for deep boreholes regardless of the drill type. You can have a cable-suspended thermal drill or use wireline technology on a thermal drill, in theory; I don't know of an example, which I think is because thermal drills are rarer. The best reference I have (Talalay 2016) is specifically about mechanical ice drilling -- I think the paucity of references on thermal ice drilling is because it is used less, particularly for deep cores. For drill string I added a link; does that help? Mike Christie (talk - contribs - library) 11:29, 3 September 2017 (UTC)[reply]

Coordinator notes: Looking through, I see we have a source spot check, but I don't see a check for source formatting/reliability. If I haven't missed it, one can be requested at the usual place. Also, RockMagnetist, do you have anything further to add? Sarastro1 (talk) 21:27, 13 September 2017 (UTC)[reply]

Source review

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Source review - spotchecks not done

Some of the above inconsistencies result from my starting to add harvnb but not completing the task. I'll try to get to it tomorrow. RockMagnetist(talk) 04:19, 14 September 2017 (UTC)[reply]
Nikki, I think everything is now addressed. Thanks for the review. Mike Christie (talk - contribs - library) 01:47, 15 September 2017 (UTC)[reply]
Comments by Jo-Jo Eumerus:
Number of broken harv citations. Done
  • File:EPICA delta D plot.svg: Source file needs to explain how it was created, since the source URL has no images. Section is pertinent.
Seems like there is good ALT text for everything. Jo-Jo Eumerus (talk, contributions) 15:42, 14 September 2017 (UTC)[reply]
Some file sources ought to not be in bare URL form.
I fixed a couple of sources; can you point me at anything else that needs fixing? Mike Christie (talk - contribs - library) 01:45, 15 September 2017 (UTC)[reply]

@Jo-Jo Eumerus: I think I've responded to all your points above. Thanks for the review. Mike Christie (talk - contribs - library) 01:45, 15 September 2017 (UTC)[reply]

@Jo-Jo Eumerus: I've responded again -- can you let me know what remains to be fixed? Thanks. Mike Christie (talk - contribs - library) 15:38, 17 September 2017 (UTC)[reply]

Coordinator query: I think we are just about there, but I just want to check if Nikki and Jo-Jo Eumerus are happy with the sourcing and images side of things. Sarastro1 (talk) 21:14, 21 September 2017 (UTC)[reply]

Fine by me. Nikkimaria (talk) 00:16, 22 September 2017 (UTC)[reply]
Passable (as in wiktionary:passable, that is). Jo-Jo Eumerus (talk, contributions) 14:48, 22 September 2017 (UTC)[reply]
The above discussion is preserved as an archive. Please do not modify it. No further edits should be made to this page.
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