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Icy contenders weigh in

Posted on 5 February 2013 by Jason Box

Guest post by Jason Box from

Dahl-Jensen et al. (2013)[i] suggest that the Greenland ice sheet was more stable than previously thought[ii], enduring ~6k years of temperatures 5-8 C above the most recent 1000 years during the Eemian interglacial 118-126k years before present, its loss at the time contributing an estimated 2 m (6.6 ft) of global sea level compared to a total of 4-8 m (13-26 ft)[iii], implying Antarctica was and will become the dominant source of sea level change. Consequently, environmental journalist Andrew Revkin writes: “The dramatic surface melting [in Greenland], while important to track and understand has little policy significance.”

Given the non-trivial complexity of the issue and that Greenland has been contributing more than 2:1 that of Antarctica to global sea level in the recent 19 years (1992-2010)[iv], let’s not consider Greenland of neglible policy relevance until that ratio is 1:1 if not reversed, say, 0.5:1. Greenland, currently the leading contender with surface melting dominating its mass budget[v], the positive feedback with surface melting and ice reflectivity doubling Greenland’s surface melt since year 2000[vi]. Professor Richard Alley weighs in again: “We have high confidence that warming will shrink Greenland, by enough to matter a lot to coastal planners.”

That’s not to say that Antarctica couldn’t take over from Greenland the position of number 1 global sea level contributor in the foreseeable future. Nor should one be surprised if it did, given that Antarctica contains a factor of 10 more ice than Greenland[vii],[viii].  And it is probable that the planetary energy imbalance[ix] caused by elevated greenhouse gasses, expressed primarily through massive oceanic heat uptake[x], is delivering enough erosive power to destabilize the 3.3 m of sea level[xi] in the marine-based West Antarctic ice sheet. Yet, for today, consider also that climate change if increasing Antarctic precipitation a few percent can tip its mass balance toward the positive, lessening its sea level contribution[xii] even while its glaciers retreat.

Irrespective of sea level forcing, through its ice mass budget Greenland plays an important role to North Atlantic climate through ocean thermohaline circulation, even being suggested as the Achilles heel of the global climate system[xiii]. I wouldn’t tell our European friends Greenland’s hardly policy-relevant when climate change offers higher amplitude extremes in precipitation if not also temperature, as North Atlantic climate shifts in partial response to changes in neighboring Greenland.

Key differences between the modern Anthropocene and the Eemian interglacial suggest anthropogenic climate change may drive a different cryosphere response than during the Eemian…

Today, greenhouse gas concentrations are rising beyond 120% to 250% of peak Eemian values[xiv],[xv], driving today’s global warming and the aformentioned ocean heat content uptake that contrasts from the Eemian when warming was driven by northern latitudes receiving 30-50 Watts per sq. meter more solar energy, a more regionally-forced climate change. Anthropocene climate is forced an estimated 4/5 by by elevated greenhouse gasses and black carbon aerosols[xvi], the latter rising recently in significance after being more completely bounded[xvii]. Anthropogenic warming is clearly overwhelming the modern orbital cooling[xviii] and the decrease in solar output since the late 1970s[xix].

Because the Greenland ice sheet surface undergoes much more seasonal melting than the surface of the Antarctic ice sheet, in Greenland decanting a factor of 2 increase of meltwater runoff annually since 2000[xx], anthropogenic sources of light absorbing impurities provide a mechanism to multiply the cryospheric albedo feedback in ways presumably not occurring during the Eemian. Today, the combination of a.) land clearing by humans using fire, b.) industrial soot from fossil fuel combustion, and perhaps c.) larger fires the a legacy of fire suppression are in contrast to Eemian wildfire, that (as far as we know) did not include human factors. All me to here plug Dark Snow Project[xxi] that is currently soliciting donations to crowdfund a field and laboratory campaign designed to assess the impact of increasing wildfire on darkening the Greenland ice sheet.

Richard Alley: “While Antarctica is relatively unknown, Greenland is relatively known and therefore useful to guide policy even if the ice sheet becomes second most important to sea level, and to provide guidance to Antarctic colleagues [in surface melt studies]”

In the end, what matters to our concerns about the rate of sea level rise is the sum total volume change of all land ice. As long as glaciers and ice caps (GICs) (excluding the ice sheets) remain significant contenders (GICs lost mass at a rate of 148 ± 30 Gt per year from January 2003 to December 2010)[xxii], Antarctica lost 40% less during this period than GICs, and Greenland lost more than the two combined, we should stay focused on understanding the dynamics of all crysopheric systems in relation to the serious perturbation imposed by human activity. The Eemian has its own limits of utility in informing humanity of the trajectory we’re on.

Works Cited

[i] Eemian interglacial reconstructed from a Greenland folded ice core, D. Dahl-Jensen, M.R. Albert, A. Aldahan, N. Azuma, D. Balslev-Clausen, M. Baumgartner, A. Berggren, M. Bigler, T. Binder, T. Blunier, J.C. Bourgeois, E.J. Brook, S.L. Buchardt, C. Buizert, E. Capron, J. Chappellaz, J. Chung, H.B. Clausen, I. Cvijanovic, S.M. Davies, P. Ditlevsen, O. Eicher, H. Fischer, D.A. Fisher, L.G. Fleet, G. Gfeller, V. Gkinis, S. Gogineni, K. Goto-Azuma, A. Grinsted, H. Gudlaugsdottir, M. Guillevic, S.B. Hansen, M. Hansson, M. Hirabayashi, S. Hong, S.D. Hur, P. Huybrechts, C.S. Hvidberg, Y. Iizuka, T. Jenk, S.J. Johnsen, T.R. Jones, J. Jouzel, N.B. Karlsson, K. Kawamura, K. Keegan, E. Kettner, S. Kipfstuhl, H.A. Kjær, M. Koutnik, T. Kuramoto, P. Köhler, T. Laepple, A. Landais, P.L. Langen, L.B. Larsen, D. Leuenberger, M. Leuenberger, C. Leuschen, J. Li, V. Lipenkov, P. Martinerie, O.J. Maselli, V. Masson-Delmotte, J.R. McConnell, H. Miller, O. Mini, A. Miyamoto, M. Montagnat-Rentier, R. Mulvaney, R. Muscheler, A.J. Orsi, J. Paden, C. Panton, F. Pattyn, J. Petit, K. Pol, T. Popp, G. Possnert, F. Prié, M. Prokopiou, A. Quiquet, S.O. Rasmussen, D. Raynaud, J. Ren, C. Reutenauer, C. Ritz, T. Röckmann, J.L. Rosen, M. Rubino, O. Rybak, D. Samyn, C.J. Sapart, A. Schilt, A.M.Z. Schmidt, J. Schwander, S. Schüpbach, I. Seierstad, J.P. Severinghaus, S. Sheldon, S.B. Simonsen, J. Sjolte, A.M. Solgaard, T. Sowers, P. Sperlich, H.C. Steen-Larsen, K. Steffen, J.P. Steffensen, D. Steinhage, T.F. Stocker, C. Stowasser, A.S. Sturevik, W.T. Sturges, A. Sveinbjörnsdottir, A. Svensson, J. Tison, J. Uetake, P. Vallelonga, R.S.W. van de Wal, G. van der Wel, B.H. Vaughn, B. Vinther, E. Waddington, A. Wegner, I. Weikusat, J.W.C. White, F. Wilhelms, M. Winstrup, E. Witrant, E.W. Wolff, C. Xiao, and J. Zheng, Nature, vol. 493, pp. 489-494, 2013.

[ii] Substantial contribution to sea-level rise during the last interglacial from the Greenland ice sheet, Kurt M. Cuffey* & Shawn J. Marshall, Nature 404, 591-594 (6 April 2000) | doi:10.1038/35007053

[iii] Kopp, R. E., Simons, F. J., Mitrovica, J. X., Maloof, A. C. & Oppenheimer, M. Probabilistic assessment of sea level during the last interglacial stage. Nature 462, 863–867 (2009). & Dutton, A. & Lambeck, K. Ice volume and sea level during the last interglacial. Science 337, 216–219 (2012).

[iv]A Reconciled Estimate of Ice-Sheet Mass Balance, Andrew Shepherd, Erik R. Ivins, Geruo A, Valentina R. Barletta, Mike J. Bentley,Srinivas Bettadpur, Kate H. Briggs, David H. Bromwich, René Forsberg, Natalia Galin,Martin Horwath, Stan Jacobs, Ian Joughin, Matt A. King, Jan T. M. Lenaerts, Jilu Li,Stefan R. M. Ligtenberg, Adrian Luckman, Scott B. Luthcke, Malcolm McMillan, Rakia Meister,Glenn Milne, Jeremie Mouginot, Alan Muir, Julien P. Nicolas, John Paden, Antony J. Payne,Hamish Pritchard, Eric Rignot, Helmut Rott, Louise Sandberg Sørensen, Ted A. Scambos,Bernd Scheuchl, Ernst J. O. Schrama, Ben Smith, Aud V. Sundal, Jan H. van Angelen,Willem J. van de Berg, Michiel R. van den Broeke, David G. Vaughan, Isabella Velicogna,John Wahr, Pippa L. Whitehouse, Duncan J. Wingham, Donghui Yi, Duncan Young, H. Jay Zwally, , Science, 338 (6111) 1183-1189, DOI: 10.1126/science.1228102,

[v] Partitioning recent Greenland mass loss, van den Broeke, M. R., J. Bamber, J. Ettema, E. Rignot, E. Schrama, W. J. van de Berg, E. van Meijgaard, I. Velicogna and B. Wouters, 2009: Science, 326, 984-986.

[vi]  Greenland ice sheet albedo feedback: thermodynamics and atmospheric drivers, Box, J. E., Fettweis, X., Stroeve, J. C., Tedesco, M., Hall, D. K., and Steffen, K., The Cryosphere, 6, 821-839, doi:10.5194/tc-6-821-2012, 2012. open access

[vii] BEDMAP: A new ice thickness and subglacial topographic model of Antarctica, Lythe, M.B., D.G. Vaughan, and the BEDMAP Group, 2001:  J. Geophys. Res., 106(B6), 11335–11351.

[viii] A new ice thickness and bedrock data set for the Greenland ice sheet, 1, Measurement, data reduction, and errors, Bamber, J. L., R. L. Layberry, S. P. Gogineni, J. Geophys. Res., 106(D24), 33773-33780, 2001.

[ix] Earth’s Energy Imbalance and Implications, James Hansen, Makiko Sato, Pushker Kharecha, Karina Von Schuckmann, Atmospheric Chemistry and Physics (2011), Volume: 11, Issue: 24, Pages: 39

[x] Global ocean heat content 1955–2008 in light of recently revealed instrumentation problems, Levitus, S., J. I. Antonov, T. P. Boyer, R. A. Locarnini, H. E. Garcia, and A. V. Mishonov, 2009:, Geophys. Res. Lett., 36, L07608, doi:10.1029/2008GL037155.

[xi] Reassessment of the Potential Sea-Level Rise from a Collapse of the West Antarctic Ice Sheet, Jonathan L. Bamber, Riccardo E. M. Riva, Bert L. A. Vermeersen, Anne M. LeBrocq, Science 15 May 2009: Vol. 324 no. 5929 pp. 901-903 DOI: 10.1126/science.1169335

[xii] Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise, Curt H. Davis, Yonghong Li, Joseph R. McConnell, Markus M. Frey, Edward Hanna, SCIENCE, 308, 24 JUNE 2005

[xiii] Thermohaline Circulation, the Achilles Heel of Our Climate System: Will Man-Made CO2 Upset the Current Balance? Wallace S. Broecker, SCIENCE, 278, 28 NOVEMBER 1997

[xiv] Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change ,Solomon, S., D. Qin, M. Manning, Z. Chen, M,. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.), IPCC (Intergovernmental Panel on Climate Change), 2007. Cambridge University Press, Cambridge United Kingdom and New York, NY, USA, 996 pp.

[xv] Recent Greenhouse Gas Concentrations, Blasing, T.J., DOI: 10.3334/CDIAC/atg.032

[xvi] Climate Change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change ,Solomon, S., D. Qin, M. Manning, Z. Chen, M,. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.), IPCC (Intergovernmental Panel on Climate Change), 2007. Cambridge University Press, Cambridge United Kingdom and New York, NY, USA, 996 pp.

[xvii] Bounding the role of black carbon in the climate system: A scientific assessment, T. C. Bond, S. J. Doherty, D. W. Fahey, P. M. Forster, T. Berntsen, B. J. DeAngelo, M. G. Flanner, S. Ghan, B. Kärcher, D. Koch, S. Kinne, Y. Kondo, P. K. Quinn, M. C. Sarofim, M. G. Schultz, M. Schulz, C. Venkataraman, H. Zhang, S. Zhang, N. Bellouin, S. K. Guttikunda, P. K. Hopke, M. Z. Jacobson, J. W. Kaiser, Z. Klimont, U. Lohmann, J. P. Schwarz, D. Shindell, T. Storelvmo, S. G. Warren and C. S. Zender, Accepted manuscript online: 15 JAN 2013 07:30AM EST | DOI: 10.1002/jgrd.50171

[xviii] Modeling the Climatic Response to Orbital Variations, J Imbrie, J Z Imbrie (1980). Science 207(4434): 943–953. doi:10.1126/science.207.4434.943.

[xx] after Estimating Greenland ice sheet surface mass balance contribution to future sea level rise using the regional atmospheric climate model MAR Fettweis, Xavier; Franco, Bruno; Tedesco, M.; van Angelen, J.; Lenaerts, J.; van den Broeke, M.; Gallée, H. in Cryosphere Discussions (The) (2012), 6

[xxii] Recent contributions of glaciers and ice caps to sea level rise, Thomas Jacob, John Wahr, W. Tad Pfeffer & Sean Swenson, Nature 482, 514–518 (23 February 2012) doi:10.1038/nature10847

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Comments 1 to 11:

  1. I donated to even before the research article on the importance weighting between Greenland and Antarctica melting became known: it's important to know if humanity can buy some time by reducing industrial soot and combatting wildfires more fiercly.

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  2. Jason and collaborators,

    Best of luck with this.  I hope that you are successful in raising the funds and bringing this the "Dark snow project"  to fruition.

    The findings of Dahl-Jensen et al. (2013) just do not make sense.  Greenland is probably going to warm more than 5-8 C and the recent response to less warming than that is indicative of the fact that the ice sheet is indeed sensitive to warming.  So I agree that the Eemian is probably not a good proxy of how thigs will unravel during the Anthropocene.  Do you intend to respond to Dahl-Jensen et al.?

    PS:  I had the good fortune to attend the special showing of "Chasing Ice" at the AGU, the movie and the panel discussion that followed were brilliant.

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  3. Albatross, the findings from Dahl-Jensen need to be considered in context, with that context being that other ice sheets such as the West Antarctic Ice Sheet (WAIS) and the East Antarctic Ice Sheet (EAIS) also are sensitive to warming.  My takeaway from Dahl-Jensen:

    The NEEM community members group examined a Greenland Ice Sheet (GIS) core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago).  What they found was that surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 ± 4°C above the mean of the past millennium. 

    Coupled with the determined thinning of the GIS at that point, they were able to quantify the SLR contribution of the GIS during the Eemian to be no more than 2 meters, with a greatest likelihood centered at about 1 meter Sea Level Rise (SLR).

    The challenge presented by the NEEM study is this:  the Eemian SLR is generally thought to be 6–8 meters above that of the 20th Century.  If the GIS contributed only a quarter of that (at best), then where did the remainder come from?

    And that is where the contributions from the WAIS and the EAIS come into context.  For those sheets needed to have been significant contributing players in order to "close the Eemian SLR balance."

    My two cents.  Glad Jason wrote this, so I can now deep-six the article I had started on.

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  4. Slightly off topic but I really don't know who else to turn to...


    Steven Goodard posted (Feb 5) 2 sets of time series and came up with 30,000 km2 above average of global sea ice interesting part of the data series is the title goes to 2008 but the inputs have 34 measurements in 2013. 

    I am inclined to believe his findings about as far as I trust Goodard to be his real name. Jason (or anyone) please comment on this suspiciously false factoid. 

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  5. There may be another factor that will accelerate the melting of Greenland.  When the floating ice is gone, hurricanes, such as the one in Aug 2012 will be able to sidle up close to the coast of Greenland.  Such low pressure areas induce katabatic winds down the slopes of Greenland.  Downflowing wind heats up 9.80C per km fall.  This heat is lost to the ice and at the same time, the hurricane is pumping energy up into the atmosphere from the ever more open arctic ocean.  A Walker cell??  Gaia may have another little surprise in store for us.  By the way, is it known if the Arctic ocean was ice free, even in September during the Eemian?

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  6. YubeDude @4, if you look at the figures you will find the claim is legitimate, sort of.  On 2013.0867 (ie, February 2nd), the global Sea Ice Area anomaly is 0.0004967 million square kilometers.  Of course, on Feb 1st, it was -0.075174 million square kilometers; while on February 4th it was -0.0718191 million square kilometers.  In fact, he has managed to pick out the only two days (February 3rd was 0.0194787 million square kilometers) with a positive global anomaly since April of last year.  The desperation of the cherry pick shows the paucity of evidence in support of denier views.

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  7. YubeDude, what is Goddard trying to claim?  That sea ice is recovering?  (Actually, it is re-covering in the Arctic, ha ha ha)  He'd do better to cherry-pick days 89-115 of the Arctic sea ice area, when, gasp!, the 10-year linear trend is positive!  (ignore the beast getting ready to walk in the door at day 158.  Keep combing over it, Steve!  There will be little rhetorically valuable gems from time to time -- just show em quick and sell em hard.

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  8. Tom @6 and DSL @7

    Goddard is saying that curently global sea ice area is above average by 30,000 km2. If I was inclined I would spin this to show that NH-SI is gaining rapidly as well as show that SH-SI is not being lost as fast usual...both would discount AGW trends; that is if I was so inclined.

    Now obviously anything above an average would be of considerable interest but he is only looking at area and not volume/thickness or the multi year quality of SI. He is also, by making it a global SI metirc, equating SH-SI with NH-SI as though they had equal input into the system. 

    One part of what Tom mentioned that has me wondering is how the SI area can fluctuate so wildly on a day to day basis? 

    Sorry to wander away from the  topic but I really didn't  know where else to ask for  some input on Goddard's Gish.

    Why does they new posting box not redline spelling errors?? me I need the editor help.

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  9. At climate desk live another Jason Box report Humans Have Already Set in Motion 69 Feet of Sea Level Rise he shows there is a relationship between sea level rise and CO2 levels see graph at 189sec . I first came across this in a different guise in David Archers book the Long Thaw and paper, Fig3.

    That relationship is also shown in much more detail for the last 500,000 years by Foster & Rohling   in the "Relationship between sea level and climate forcing by CO2 on geological timescales" , graph here.

    Having seen that graph 21m (69ft) looks optimistic. There appears good reason to think a lot of ice could melt. With the amount of CO2 we have put into the atmosphere the situation now is a very different regime to that in that in the Eemian. Dahl & Jensen's better news of stability may no longer apply.

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  10. Sorry - I forgot to point out that the abstract from Foster and Rohling draw the conclusion of a 9 m rise for current CO2 levels.  I haven't worked out yet how that squares with the graph.

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  11. mdenison,

    I don't know the source of this 69ft of SLR claim in 189sec of the video. The Foster & Rogling graph is not readable to me. It looks like they did linear extrapolation of SL vs CO2 trend from last glacial maximum, which is meaningless IMO.

    Alley et al 2005 in their Fig1 provide a little different picture. And different numbers are exptrapolated when Richard Alley does "the absolute stupidest thing" with this figure from about 0:45 to 1:30 of this video, it looks roughly 10-12m of SLR covering 10% of the current population.

    So those "absolute stupidest thing"numbers are uncertain, especially given the uncertainty of the CO2 levels for which we have to go back some 30Ma.

    I don't understand how Jason got it fixed at 21m. But the bottom line is, as you can carefullt read in Alley et al 2005, this process will take some 2 milenia. Meanwhile a lot of things can happen and CO2 may go back down. And even if not, the 10% population/infrastructure is not the "end of the world" disaster. It is possible for homo sapiens to adapt to that.

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