Dark Snow Project: Ice Sheets, Microbes, and Melt

April 24, 2014

Ablation zone extent on the Greenland ice sheet: July 8 (left) and July 12 (right). On July 8, ~40% of the ice sheet was melting. Four days later, ~97% of the ice sheet surface had thawed. Credit: Nicolo E. DiGirolamo, SSAI/NASA GSFC, and Jesse Allen, NASA Earth Observatory

The Dark Snow Project is making plans for an expanded presence on the Greenland Ice Sheet this summer. Details are online at Dark Snow Project’s website. We have expanded our alliance with several universities, more scientists, and a diverse team of climate communicators.
For the team to maximize our effectiveness, we need support from everyone who can possibly help – donations page here.

Joseph Cook at Dark Snow Blog:

Greenland contains the largest continuous mass of ice in the northern hemisphere; an area over 2 million km2. The frequency of Greenland surface melting has increased, likely as a result of human-induced climate warming, with the melt-area covering almost the entire ice sheet surface in 2012 (Ngheim et al. 2012; Box et al, 2013; Tedesco et al. 2013).

Although its fair to say that higher temperatures mean more melt, the response of earth’s glaciers and ice sheets to climate warming is complex, also depending upon a range of feedbacks (e.g. Box et al, 2012). For example, when ice melts, liquid water runs over its surface, sometimes collecting in pools and lakes. Liquid water is a more effective absorber of sunlight than snow or ice, so the overall reflectivity (also called albedo, Greek for ‘whiteness’) of the ice decreases. The result is faster ice melt. Melting promotes more melting.

Box et al’s (2012) image of albedo anomaly in summer 2012. Darker blue means greater darkening compared to average albedo.

Not only melt water that reduces  Greenland ice sheet albedo. A variety of aerosol ‘impurities’ further reduce surface albedo. These include black carbon (BC) derived from incomplete combustion of fossil fuels, other industrial activity, biomass burning, and wildfire. Black carbon can be transported across the hemisphere through the atmosphere and deposited on ice, and currently the impacts remain uncertain (Hodson, 2014). Dark Snow field science is examining this question in detail based on 2013 field measurements and planned measurements for June-August, 2014.

Black Carbon – produced during the incomplete combustion of fossil fuels (photo, wikimedia commons)

The presence of microbes on the ice surface also alter albedo and can therefore influence melt rates (Yallop et al, 2012). They do so by growing and adding dark biomass to the ice, causing mineral fragments to aggregate and resist removal (flushing) by melt water, and by producing dark humic substances and pigments. There may even be a relationship between microbial activity and BC. Yet, it is not yet known whether microbes metabolise BC and reduce its impact, or cause it to “stick” to the ice surface and prevent its removal by flushing (Hodson, 2014).

Many microbes on the Greenland ice sheet inhabit ‘cryoconite’ holes; cylindrical tubes ‘drilled’ into the bright ice surface ice by dark cryoconite debris. The debris is a loose bonding of minerals encased in microbial biomass (e.g. Gribbon, 1979; Cook et al, 2010). Cryoconite holes on the Greenland ice sheet likely provide favourable conditions for photosynthesis by: 1.) maintaining light intensities that are high but not harmful because ultraviolet radiation is not transmitted by water; 2.) providing nutrients in melt water flowing in through the hole walls; and 3.) providing relatively long term (years) storage of microbes. This also promotes proliferation of bacteria and “grazers” that feed upon other microbes. These factors make cryoconite holes active and biodiverse ice sheet habitats (Hodson et al, 2008).

Cryoconite holes – generally considered to be the most biodiverse microbial habitats on glacier surfaces (photo, J. Cook)

Despite being the most studied biological entity on the surface of the Greenland ice sheet, cryoconite holes remain poorly understood in terms of their biological community dynamics, thermodynamics, evolution and impact on albedo. Further, the characteristics of the holes themselves, and the microbes inhabiting them, have been shown to vary depending upon location on the ice sheet (Stibal et al, 2012), and these spatial patterns probably also evolve over time. Edwards et al (2014) recently found microbial communities to be extremely dynamic in response to environmental change, while Irvine-Fynn and Edwards (2014) showed that hydrological and glaciological processes might also influence microbial activity. Cryoconite holes will provide research foci for some members of the field team in summer 2014. For further information on cryoconite, see: herehere; and here.

by Joseph Cook and Jason Box

References:

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

Box, J.E., Cappelen, J., Chen, C., Decker, D., Fettweis, X., Mote, T., Tedesco, M., van de Wal, R.S.W., Wahr, J. 2013. Greenland ice sheet. Arctic Report Card. http://www.arctic.noaa.gov/reportcard/greenland_ice_sheet.html

Cook, J., Hodson, A., Telling, J., Anesio, A., Irvine-Fynn, T, Bellas, C. 2010. The mass-area relationship within cryoconite holes and its implications for primary production. Annals of Glaciology, 51 (56): 106-110

Edwards, A., Mur, L. A.J., Girdwood, S. E., Anesio, A. M., Stibal, M., Rassner, S. M.E., Hell, K., Pachebat, J. A., Post, B., Bussell, J. S., Cameron, S. J.S., Griffith, G. W., Hodson, A. J. and Sattler, B. (2014), Coupled cryoconite ecosystem structure–function relationships are revealed by comparing bacterial communities in alpine and Arctic glaciers. FEMS Microbiology Ecology. doi: 10.1111/1574-6941.12283

Gribbon, P.W. 1979. Cryoconite holes on Sermikaysak, West Greenland. Journal of Glaciology, 22: 177-181

Hodson, A., Anesio, A.M., Tranter, M., Fountain, A., Osborn, M., Priscu, J., Laybourn-Parry, J., Sattler, B. 2008. Glacial Ecosystems. Ecological monographs, 78 (1): 41-67

Hodson, A. 2014. Understanding the dynamics of black carbon and associated contaminants in glacial systems.WIREs Water 2014, 1:141–149. doi: 10.1002/wat2.1016

Irvine-Fynn, T.D.L., and A, Edwards. 2014. A frozen asset: The potential of flow cytometry in constraining the glacial biome. Cytometry Part A 85 (1), 3-7

Nghiem, S. V., D. K. Hall, T. L. Mote, M. Tedesco, M. R. Albert, K. Keegan, C. A. Shuman, N. E. DiGirolamo, and G. Neumann (2012), The extreme melt across the Greenland ice sheet in 2012, Geophys. Res. Lett., 39, L20502, doi:10.1029/2012GL053611.

Stibal, M., Telling, J., Cook, J., Mak, K.M., Hodson, A., Anesio, A.M. 2012. Environmental controls on microbial abundance on the Greenland ice sheet: a multivariate analysis approach. Microbial Ecology, 63: 74-84.

Tedesco, M., X. Fettweis, T. Mote, J. Wahr, P. Alexander, J.E. Box, B. and Wouters. 2013. Evidence and analysis of 2012 Greenland records from spaceborne observations, a regional climate model and reanalysis data, The Cryosphere, 7, 615-630, doi:10.5194/tc-7-615-2013.

Yallop, M.L., Anesio, A.J., Perkins, R.G., Cook, J., Telling, J., Fagan, D., MacFarlane, J., Stibal, M., Barker, G., Bellas, C., Hodson, A., Tranter, M., Wadham, J., Roberts, N.W. 2012. Photophysiology and albedo-changing potential of the ice-algal community on the surface of the Greenland ice sheet. ISME Journal, 6: 2302 – 2313

9 Responses to “Dark Snow Project: Ice Sheets, Microbes, and Melt”

  1. omnologos Says:

    I have added a rather small contribution myself – hopefully will be able to do more in the following years, there is a big project coming up for me too 😉 – marginally related to global warming ;-D

  2. jpcowdrey Says:

    Minor correction, peter; albedo is derived from Latin, not Greek.

  3. Gingerbaker Says:

    Um, can we just take it as granted that Greenland is melting really fast?

    At what point can we say “Yup, we know what we need to know, and now what we really need to do – what we really need to focus our energies on – is how to build and deploy new renewable energy infrastructure?

    There are a heck of a lot of very well educated intelligent people who are basically doing an impersonation of the eccentric disheveled entomologist with kooky hair and myopia cataloging insect morphology in a dusty basement in a backwater university. I know you guys love doing this kind of stuff…..

    But we have gotten now to the part of the movie “The Day after Tomorrow” where Dennis Quaid stops taking measurements and starts yelling at the Vice President, surely?

  4. indy222 Says:

    Every month I read a new paper on a new positive feedback, or a worsening of known positive feedbacks. The slippery slope is gaining momentum to a very very grim future. This trend is genuinely frightening.
    I call on the many good and dedicated scientists of the IPCC to create a new group, call it the PCC and leave the government officials OFF the list! We need to get media coverage not just from a few stand-up scientists willing to be “alarmists”, but essentially the entire brain-trust of the IPCC, and tell the world bluntly that it’s not just time to think seriously about lowering the carbon emission rate to some extent, or institute a small fee-and-dividend, but to slam on the brakes, recession-be-damned, and jolt-start the transition to renewables, and promise all politicians that we the people will consider the next election a single-issue election: vote in a stiff fee-and-dividend, with stiff sanctions on other carbon-pollution nations if they don’t follow along quickly, or we don’t care how much money you get from industry lobbyists – you’re getting retired and then you’ll be no use to any of them.


  5. […] 2014/04/24: PSinclair: Dark Snow Project: Ice Sheets, Microbes, and Melt […]


  6. […] 2014/04/24: PSinclair: Dark Snow Project: Ice Sheets, Microbes, and Melt […]


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