Monday, December 19, 2011

Semiletov v Dmitrenko: The tale of the tape

Thanks to Mr. Revkin's intrepid reporting, we now know that there is a bit of a schism afflicting researchers looking at methane release from the East Siberian Arctic Shelf (ESAS). After reporting on the permafrost model presented by Dmitrenko at the recent AGU meeting (a model that suggests methane releases in the Arctic are not going to markedly accelerate with climate change), Revkin relates:
Semiletov is finally in touch with me (he'd gone on vacation right after AGU) and you'll hear more on his work soon. He's very critical of Dmitrenko. This kind of back-and-forthing is the process of science in action.
And indeed it is. And both of these authors have many peer-reviewed climate studies to their name. They are both respectable professionals, and only time will tell who has a better sense of what is happening on the ESAS. I was interested, though, in how they compared to one another in terms of their stature in this field, so I did a little research.

There is no completely reliable and objective way to gauge the impact of a particular researcher in their field, but a commonly used rule of thumb is to look at the number of times their publications have been cited. Once a scientist crosses the great divide of peer-reviewed publication that separates him or her from a Monckton or a Glenn Beck, the next test of relevance is whether or not their work is useful to others in the field; whether it is considered to be work that needs to be addressed or built upon. Science that doesn't stand the test of time gets superseded or just ignored.

Citations, then, are a way to assess, within the scientific community, what Samuel Johnson called the only objective measure of greatness "length and duration of esteem."

One quick example of how this works. Steig (2009) analyzed temperature trends in Antarctica. A "skeptic," Ryan O'Donnell, with assistance from Steig, turned his critique of Steig (2009) into something that successfully navigated peer review -- O'Donnell (2010). Climate Audit then triumphantly proclaimed "O'Donnell et al 2010 Refutes Steig et al 2009." Watts gloated similarly.

With both publications in print for more than a year, let's see how they're doing:

Improved methods for PCA-based reconstructions: case study using the Steig et al. 2009 Antarctic temperature reconstruction (O'Donnell et al, 2010). Cited by 2.
"Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year" (Steig et al, 2009). Cited by 163.
 So that's basically how it works. Better science tends to get more citations. So with that in mind, I searched Google Scholar for "Semiletov and methane," and "Dimitrenko and methane," and took the first five articles I could find:

Dimitrenko and methane
IA Dmitrenko, SA Kirillov, LB Tremblay… - Journal of Geophysical …, 2011 - 

None yet.

IA Dmitrenko, SA Kirillov, LB Tremblay… - Journal of Geophysical …, 2010 -

Cited by 8.

…, JA Hoelemann, I Dmitrenko… - SPECIAL PAPERS- …, 2007 -

Cited by 2.

C Schultz - Eos, Transactions American Geophysical Union, 2011 -

This is a summary of the first paper. I did it again! But there's nothing else to plug in here. No citations.

J Hoelemann, M Makhotin, C Wegner, I Dmitrenko… - 2008 -


Dmitrenko has a total of ten citations for these papers. I felt a little bad about this, so I looked into the matter some more, and found, based on his publications listed at the International Arctic Research Center, that he is more of a water-and-wind guy, and less of a permafrost-and-methane guy (nothing wrong with that). So I tried again with the publications listed here:

Dmitrenko, I, Kirillov S, Eicken H, Markova N. 2005. Wind-driven summer surface hydrography of the eastern Siberian Shelf. Geophysical Research Letters. 32:L14613.

Cited by 13.

Dmitrenko, I, Holemann J, Kirillov S, Berezovskaya S, Ivanova D, Eicken H, Kassens H. 2006. Sea ice impact on the periodical shallow water dynamics in the Laptev Sea (Siberian Arctic). Proceedings of the 16th IAHR International Symposium on Ice at Dunedin, New Zealand. :375-381.

Cited by 2.

Dmitrenko, I, Kirillov S, Ivanov VV, Woodgate R. 2008. Mesoscale Atlantic water eddy off the Laptev Sea continental slope carries the signature of upstream interaction. Journal of Geophysical Research. 113:C07005.

Cited by 5.

Dmitrenko, I, Tyshko K, Kirillov S, Hölemann J, Eicken H, Kassens H. 2005. Impact of flaw polynas on the hydrography of the Laptev Sea. Global and Planetary Change. 48:9-27.

Could not find with Google Scholar.

Dmitrenko, I, Polyakov IV, Kirillov S, Timokhov L, Simmons HL, Ivanov VV, Walsh D. 2006. Seasonal Variability of Atlantic Water on the Continental Slope of the Laptev Sea during 2002-2004. Earth and Planetary Science Letters. 244:735-743.

Cited by 11.

A total of 31 citations, or an average of six per publication (possibly depressed a bit by my inability to find citations for the fourth paper.)

Semiletov and methane
SA Zimov, YV Voropaev, IP Semiletov, SP Davidov… - Science, 1997 - 

Cited by 116. 

[PDF] from Shakhova, I Semiletov, A Salyuk, V Yusupov… - Science, 2010 -

Cited by 55.

N Shakhova, I Semiletov… - Geophysical Research Letters, 2005 -

Cited by 36.

…, I Semiletov - Journal of Marine Systems, 2007 - Elsevier

Cited by 19.

N Shakhova, I Semiletov, A Salyuk… - Geophysical Research …, 2008 -

Cited by 11.

Total citations: 227.

Semiletov's least cited paper is cited almost as many times (11) as Dmitrenko's most cited (13). He has more than seven times as many citations. Also, interestingly, he's clearly something of a specialist in this area; finding five papers about Arctic methane by Semiletov was no trouble at all. Dmitrenko has expertise in the relevant fields of hydrology and the Arctic, but he seems to be something of a methane newbie; only the first paper, which Revkin references, from October 2011, is about methane emissions.

Dmitrenko is a serious scientist; his work should be and will be judged on its merits. Nothing against him. But taking a quick look at their respective records, Dmitrenko is a strange choice for a debunker of Semiletov's concerns. First, basic weight-class stuff:

1. Dmitrenko's top papers have been cited a few dozen times; Semiletov has hundreds of citations.

On methane:

2. Semiletov has been studying methane emissions from waterlogged permafrost for at least 15 years; Dmitrenko published his first paper on the subject three months ago.

On the type of studies:

3. Dmitrenko's is a permafrost modelling study; Semiletov recently returned with direct observations from the ESAS.

Final verdict: ADVANTAGE SEMILETOV for greater experience, and longer record, more respect from peers, and recent direct observations of the phenomenon in question. I award bonus points because the established methane researcher, with a longer record and more citations, would be the one we would expect would be downplaying recent changes and be disposed to assert continuity in the face of excitable newcomers to the field. If the old man is worried, well, it puts me in mind of the old joke shirt:


  1. Thanks for the research effort on this important issue.

  2. Nice blog and nice post. I've made much the same (but much less detailed) observations over at Skeptical Science (on our Author discussion forum).

    We are in the process of preparing a post on this overall issue to hopefully coincide with the publication of Semiletov & Shakhova's latest article.

  3. I'm normally an admirer of this blog but this is rather silly.

    Dmitrenko and his seven co-authors do not argue that "a model that suggests methane releases in the Arctic are not going to markedly accelerate with climate change" but rather that the observed methane emissions observed over the East Siberian Shelf are more likely to be the result of long-lasting warming and sea-level change since the last glacial maximum rather than a response to recent global warming. Which is not quite the same thing at all.

  4. No, Andy, having just finished the paper I can assure that they do argue that first point. Heck, it's right there in the abstract:

    "The CH4 supersaturation, recently reported from the eastern Siberian shelf, is believed to be the result of the degradation of subsea permafrost that is due to the long‐lasting warming initiated by permafrost submergence about 8000 years ago rather than from those triggered by recent Arctic climate changes. A significant degradation of subsea permafrost is expected to be detectable at the beginning of the next millennium. Until that time, the simulated permafrost table shows a deepening down to ∼70 m below the seafloor that is considered to be important for the stability of the subsea permafrost and the permafrost‐related gas hydrate stability zone."

    I'd say there's something less than marked about not much happening for the next thousand years.

    The citation-count analysis probably has an apples/oranges problem, but it does seem significant that Dmitrenko is pretty fresh to the field. OTOH he did have co-authors who may have more.

    But the main thing is the paper itself. It provides a pretty thin basis for rejecting the possibility of a problem.

    There are number of points to make in that regard, but just two for now:

    The poster and the Independent article were about recent observations (the last two years). The paper's data ended in 2009.

    I need to read the prior papers relating to the model used, but to all appearances it doesn't allow for abrupt processes similar to those that resulted in the recent huge reassessment of land permafrost loss. In this regard, note Semiletov et al.'s observations of "pingo-like" formations on the ESAS. Something quite uneven is happening there. The two order of magnitude increase in the diameter of the methane plumes also contradicts a smooth degrdation of the permafrost. If the paper is right and all of this is a consequence of cumulative Holocene warming, I'd say that means we're in even worse trouble.

  5. Anyone done a back of the envelope calculation on the temperature rise expected over the next year assuming methane emissions are 4 orders of magnitude higher than that cited for 2009? It appears to me that abrupt climate change has discernably been underway for the last 2 years...I think that the situation is extremely perilous...Kind of hoping for no winter in Ottawa this year to kick the public and government in the teeth for climate change denial...knock them out of the sandbox...

  6. The information about publications by Dmitrenko is simply wrong. Since 2000 he has published 31 papers with a total of 320 citations (from Web of Science). The details follow:
    1. Recent changes in shelf hydrography in the Siberian Arctic: Potential for subsea permafrost instability, Dmitrenko et al. J GEOPHYSICAL RES, 116, C10027, 2011, Cited: 0
    2. Properties of the Atlantic derived halocline waters over the Laptev Sea continental margin: Evidence from 2002 to 2009, Dmitrenko et al. J GEOPHYSICAL RES, 116, 2011, Cited: 0
    3. Sea ice production and water mass modification in the eastern Laptev Sea
    Author(s): Krumpen; Hoelemann; Willmes; Dmitrenko et al., J GEOPHYSICAL RES, 116, C05014, 2011, Cited: 0
    4. Title: Interannual Variability of Pacific Summer Waters in the Arctic Ocean
    Makhotin; Dmitrenko, DOKLADY EARTH SCIENCES, 438, 1, 730-732, 2011, Cited: 0
    5. Fate of Early 2000s Arctic Warm Water Pulse, Polyakov; Alexeev; Ashik; Dmitrenko et al. BUL AMER METEOROLOGICAL SOC, 92, 5, 561-566, 2011,Cited: 0
    6. Arctic Ocean Warming Contributes to Reduced Polar Ice Cap, Polyakov; Timokhov Alexeev; Dmitrenko et al., J PHYSICAL OCEANOGR, 40, 12, 2743-2756, 2010, Cited: 11
    7. Wind-driven diversion of summer river runoff preconditions the Laptev Sea coastal polynya hydrography: Evidence from summer-to-winter hydrographic records of 2007-2009, Dmitrenko et al., CONTINENTAL SHELF RES, 30, 15, 1656-1664, 2010, Cited: 2.
    8. Impact of the Arctic Ocean Atlantic water layer on Siberian shelf hydrography, Dmitrenko et al., J GEOPHYSICAL RES, 115, C08010, 2010, Cited: 9
    9. A tracer study of the Arctic Ocean's liquid freshwater export variability
    Jhoan,Tremblay; Newton; Dmitrenko et al J GEOPHYSICAL RES, 115, C07015, 2010, Cited: 5
    10. Observations of supercooling and frazil ice formation in the Laptev Sea coastal polynya, Dmitrenko et al., J GEOPHYSICAL RES, 115, C05015, 2010, Cited: 5
    11. Sea-ice production over the Laptev Sea shelf inferred from historical summer-to-winter hydrographic observations of 1960s-1990s, Dmitrenko et al., GEOPHYSICAL RES LETTERS, 36, L13605 2009, Cited: 5
    12. Seasonal modification of the Arctic Ocean intermediate water layer off the eastern Laptev Sea continental shelf break, Dmitrenko et al., J GEOPHYSICAL RES, 114, C06010, 2009, Cited: 5
    13. Exchange of Laptev Sea and Arctic Ocean halocline waters in response to atmospheric forcing, Bauch; Dmitrenko et al., J GEOPHYSICAL RES, 114, C05008,2009, Cited: 7
    14. Barents Sea upstream events impact the properties of Atlantic water inflow into the Arctic Ocean: Evidence from 2005 to 2006 downstream observations, Dmitrenko et al., DEEP-SEA RES PART I, 56, 4, 513-527, 2009, Cited: 2
    15. Seasonal variability in Atlantic Water off Spitsbergen, Ivanov; Polyakov; Dmitrenko et al., DEEP-SEA RES PART I, 56, 1, 1-14, 2009, Cited: 4
    16. Eurasian Arctic shelf hydrography: Exchange and residence time of southern Laptev Sea waters, Bauch; Dmitrenko et al., CONTINENTAL SHELF RES, 29, 15, 1815-1820, 2009, Cited: 2
    17. Mesoscale Atlantic water eddy off the Laptev Sea continental slope carries the signature of upstream interaction, Dmitrenko et al., J GEOPHYSICAL RES, 113, C7, C07005, 2008, Cited: 4
    18. Toward a warmer Arctic Ocean: Spreading of the early 21st century Atlantic Water warm anomaly along the Eurasian Basin margins, Dmitrenko et al., J GEOPHYSICAL RES, 113, C5, C05023, 2008, Cited: 26
    19. The long-term and interannual variability of summer fresh water storage over the eastern Siberian shelf: Implication for climatic change, Dmitrenko et al., J GEOPHYSICAL RES, 113, C3, C03007, DOI: 10.1029/2007JC004304, 2008, Cited: 25
    20. Effects of atmospheric vorticity on the seasonal hydrographic cycle over the eastern Siberian shelf, Dmitrenko et al. GEOPHYSICAL RES LETTERS, 35, 3, 2008, Cited: 5

  7. 21. Variations in characteristics of the Barents branch of the Atlantic water in the Nansen basin under the influence of atmospheric circulation over the Barents sea, Rozhkova; Dmitrenko et al., DOKLADY EARTH SCIENCES, 418, 1, 149-154, 2008, Cited: 1
    22. Arctic ocean freshwater changes over the past 100 years and their causes, Polyakov; Alexeev; Belchansky; Dmitrenko et al. J CLIMATE, 21, 2, 364-384, 2008, Cited: 22
    23. Seasonal variability of Atlantic water on the continental slope of the Laptev Sea during 2002-2004, Dmitrenko et al., EARTH AND PLANETARY SCIENCE LETTERS, 244, 3-4, 735-743, 2006, Cited: 11
    24. One more step toward a warmer Arctic, Polyakov; Beszczynska; Carmack; Dmitrenko et al.; GEOPHYSICAL RES LETTERS, 32, 17, L17605, 2005, Cited: 85
    25. Impact of flaw polynyas on the hydrography of the Laptev Sea, Dmitrenko et al., Source: GLOBAL AND PLANETARY CHANGE, 48, 1-3, 9-27, 2005, Cited: 15
    26. Seasonal variations in Arctic sediment dynamics - evidence from 1-year records in the Laptev Sea (Siberian Arctic), Wegner; Holemann; Dmitrenko et al. GLOBAL AND PLANETARY CHANGE, 48, 1-3, 126-140, 2005, Cited: 9
    27. Zonation of the Laptev Sea landfast ice cover and its importance in a frozen estuary
    Eicken; Dmitrenko et al.,GLOBAL AND PLANETARY CHANGE, 48, 1-3, 55-83, 2005, Cited: 14
    28. Wind-driven summer surface hydrography of the eastern Siberian shelf
    Dmitrenko et al., GEOPHYSICAL RES LETTERS, 32, 14, L14613, 2005, Cited: 12
    29. Suspended particulate matter on the Laptev Sea shelf (Siberian Arctic) during ice-free conditions, Wegner; Holemann; Dmitrenko et al., ESTUARINE COASTAL AND SHELF SCIENCE, 57, 1-2, 55-64, 2003, Cited: 14
    30. Arctic Ocean variability derived from historical observations, Poyakov; Walsh; Dmitrenko et al., GEOPHYSICAL RES LETTERS, 30, 6, 1298, 2003, Cited: 15
    31. The Laptev Sea flaw polynya, Russian Arctic: effects on the mesoscale hydrography
    Dmitrenko et al., ANNALS OF GLACIOLOGY, 33, 373-376, 2001, Cited: 5

  8. Steve:

    I should have been more clear. The Dmitrenko et al paper does indeed predict increasing degradation of submarine permafrost as a result of climate change but they argue that this will become significant over many centuries rather than a few decades.

    Further, their paper focuses only on marine sources for increased methane emissions, so it is not fair to say that they claim "methane releases in the Arctic are not going to markedly accelerate with climate change" since they do not discuss the probable and very important contribution of terrestrial permafrost to increased methane and carbon dioxide emissions as a result of climate change.

    As Petrenko and others pointed out (Science September 3rd 2010) there is very poor support in the literature for a recent increase in subsea methane emissions. It could well be the case that Semiletov and Shakhova have new, unpublished evidence that demonstrates a sudden increase in emissions from the ESS. If this new evidence is reliable, then clearly Dmitrenko et al will have to go back to the drawing board. If not, then it looks like The Independent will have jumped the (clathrate) gun.

  9. Sure, Andy. Unfortunately most people seem to interpret many centuries (actual "early next millennium," IMO even more unconcerning) as requiring no action at all.

    You know, scientists have to work with the models and data they have, so I'm in no sense blaming Dmitrenko or colleagues for anything here. I'm simply looking at the arc followed by the science regarding land permafrost and seriously questioning the likelhood that the seabed stuff will melt more or less evenly down to a 70-meter depth before anything major happens. I'm sure the model does say something like that, indeed if it neglects abrupt processes it would have to. But how can we model something we have observed only anecdotally? So the science is behind the curve again, unfortunately. BTW, when we talk about the cryosphere it's not just the land permafrost evaluation that was wrong, it was ice sheets, sea ice and Arctic ocean warming as well. Did I miss something? Anyway, that track record makes me truly not sanguine about the undersea permafrost.

    Point taken about the need to be clear that we're just discussing the undersea stuff, but note that those sources have a much larger emissions potential than the land ones.

    Anyway, the NSF also recognized the need for real data, and two years ago added Samantha Joye and Ira Leifer to the team. The pub(s) forthcoming in the spring will reflect their work, as I understand it. I have to say that with them involved and with the pub(s) doubtless in prep right now, it would have been a little weird for Semiletov et al. to show up at the AGU FM and go entirely off the reservation.

  10. Well done! Thanks. Used this information with link in my post yesterday,

  11. "The information about publications by Dmitrenko is simply wrong. Since 2000 he has published 31 papers with a total of 320 citations (from Web of Science)."

    Take another look at the post. I wasn't looking for all the papers, just the first five I came across about methane. My citation total is from those five papers, not everything they ever published.

    That said, I love what you did with the Web of Science! I'm going straight there the next time I want to do a comparison like this.

  12. "You know, scientists have to work with the models and data they have, so I'm in no sense blaming Dmitrenko or colleagues for anything here."

    ME EITHER. This is more or less a lighthearted effort to give a little context to the implicit match-up presented by Revkin.

    "I'm simply looking at the arc followed by the science regarding land permafrost and seriously questioning the likelhood that the seabed stuff will melt more or less evenly down to a 70-meter depth before anything major happens."

    I have the same uneasiness. Like, does anyone remember what happened with the sea ice/glacier ice/land permafrost?

    Warm water carries a lot of energy; water currents are difficult to predict.

  13. Worth remembering -- we're adding rapid warming on top of the last warm peak in the glacial cycle:

    The Arctic shelf is currently undergoing dramatic thermal changes caused by the continued warming associated with Holocene sea level rise. During this transgression, comparatively warm waters have flooded over cold permafrost areas of the Arctic Shelf. A thermal pulse of more than 10°C is still propagating down into the submerged sediment and may be decomposing gas hydrate as well as permafrost. A search for gas venting on the Arctic seafloor focused on pingo-like-features (PLFs) on the Beaufort Sea Shelf because they may be a direct consequence of gas hydrate decomposition at depth. Vibracores collected from eight PLFs had systematically elevated methane concentrations. ROV observations revealed streams of methane-rich gas bubbles coming from the crests of PLFs. We offer a scenario of how PLFs may be growing offshore as a result of gas pressure associated with gas hydrate decomposition.

    Received 23 August 2006; accepted 20 November 2006; published 5 January 2007.

    Citation: Paull, C. K., W. Ussler III, S. R. Dallimore, S. M. Blasco, T. D. Lorenson, H. Melling, B. E. Medioli, F. M. Nixon, and F. A. McLaughlin (2007), Origin of pingo-like features on the Beaufort Sea shelf and their possible relationship to decomposing methane gas hydrates, Geophys. Res. Lett., 34, L01603, doi:10.1029/2006GL027977.

  14. While I understand the argument being put forth here it is a risky one. There are scientists who move from field to field and occasionally make major contributions. Just because someone hasn't knocked a triple in a given sub-field is not reason to dismiss that person's work in said sub-field.

    More interesting would be to discuss Dmitrenko's model and its shortcomings.

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