RE: Professor Julia Slingo OBE, Chief Scientist, Met Office, recently provided the report 'Possibility and Impact of Rapid Climate Change in the Arctic' to the Environmental Audit Committee and answered questions from the Committee on Wednesday 14 March 2012. In the responses, the Met Office referred to an earlier presentation by Prof Peter Wadhams, founding member of the Arctic Methane Emergency Group (AMEG).
The following comments are based on the uncorrected transcript, as at:
http://www.publications.parliament.uk/pa/cm201012/cmselect/cmenvaud/uc1739-iv/uc173901.htm
Prof Slingo starts out by saying that the projection of an ice-free summer in 2015, as earlier presented by Prof Peter Wadhams, is actually more credible than the modelling done by the Met Office. This remark may have been a slip of the tongue. Prof Slingo continues to rule out such a date and also rejects PIOMAS data showing an Arctic sea ice volume decline by 75% (from over 17,000 cubic kilometers before 1980 to around 4,000 cubic kilometers now). When asked to elaborate, Prof Slingo says: “
We don’t know what the thickness of ice is across the whole Arctic with any confidence”, and “
We know there is some thinning but it is not as dramatic as those numbers would suggest.” Prof Slingo also says that the observational estimates of sea ice volume are “
still very uncertain”.
It is not good scientific practice to use uncertainty - even if it was there - as the basis for ruling something out. Moreover, Prof Wadhams’ conclusion is supported by years of direct observations of the decline of sea ice volume from submarines, taking away much uncertainty, while Prof Slingo doesn’t add any convincing evidence to the contrary.
When asked about the possibility of an immediate collapse of ice cover, Prof Slingo gives no credence to that possibility and rules it out altogether “
on the basis of the extent of ice”.
Prof Slingo here ignores a point raised earlier by herself, i.e. that, apart from melting, strong winds can also influence sea ice extent, as happened in 2007 when much ice was driven across the Arctic Ocean. The fact that this occurred can only lead us to conclude that this could happen again. In fact, the thinner the sea ice gets, the more likely this is to occur. Furthermore, it is accepted science that global warming will increase the intensity of extreme weather events, so more heavy winds and more intense storms can be expected to increasingly break up the remaining ice in future, driving the smaller parts more easily out of the Arctic Ocean. Much of the sea ice loss already occurs due to sea ice moving along the edges of Greenland into the Atlantic Ocean.
In conclusion, Prof Slingo has not provided reasons to ignore the observed trend as presented by Prof Wadhams. Furthermore, Prof Slingo has not provided reasons to ignore the possibility of further feedbacks such as large releases of methane from hydrates speeding up sea ice decline.
On methane hydrates, Prof Slingo suggests that there was “
a lack of clarity in thinking about how that heating at the upper level of the ocean can get down, and how rapidly it can get down into the deeper layers of the ocean”. However, as Prof Slingo earlier brought up herself, strong winds can cause mixing of the vertical water column, bringing heat down to the bottom of the seabed, especially so in the shallow waters of the East Siberian Arctic Shelf (ESAS). A recent paper shows that “
data obtained in the ESAS during the drilling expedition of 2011 showed no frozen sediments at all within the 53 m long drilling core” (
Dr. Natalia Shakhova et al. in:
EGU General Assembly 2012).
Prof Slingo says that “
where there is methane coming out of the continental shelf there it is not reaching the surface either, because again the methane is oxidised during its passage through the sea water and none of those plumes made it to the surface. So there is a general consensus that only a small fraction of methane, when it is released through this gradual process of warming of the continental shelf, actually reaches the surface.”
In fact, methane in the shallow waters of the ESAS will rise to the surface without much oxidation, while this situation can only be expected to get worse in case of large releases.
Prof Slingo ends with some comments on geo-engineering that show she appears to be rather uninformed on this issue as well.
These responses were to have provided science-based responses to AMEG's earlier presentation, as well as to elaborate on the report submitted by the Met Office; however, the Met Office's oral and written responses were inaccurate and out of date with current scientific understanding and the rapidly changing situation in the Arctic. AMEG urges the Environmental Audit Committee to consider a new meeting with AMEG so that these issues can be further discussed.
Signatories
Peter Wadhams, Professor of Ocean Physics, University of Cambridge
Member of Arctic Methane Emergency Group
John Nissen, MA (Cantab) Natural Sciences
Chair of Arctic Methane Emergency Group
Sam Carana, editor of Arctic-news.blogspot.com
Member of Arctic Methane Emergency Group
Readers are invited to comment and, if applicable, have their names added as signatories.
References
Kwok, R., and D. A. Rothrock (2009), Decline in Arctic sea ice thickness from submarine and ICESat records: 1958- 2008, Geophys. Res. Lett., 36, L15501.
Maslowsky, W., J. Haynes, R. Osinski, W Shaw (2011). The importance of oceanic forcing on Arctic sea ice melting. European Geophysical Union congress paper XY556. See also Proceedings, State of the Arctic 2010, NSIDC.
Perovich, D.K., J.A. Richter-Menge, K.F. Jones, and B. Light (2008). Sunlight, water, ice: Extreme Arctic sea ice melt during the summer of 2007. Geophysical Research Letters 35: L11501. doi:10.1029/2008GL034007.
Rothrock, D.A., Y. Yu, and G.A. Maykut. (1999). Thinning of the Arctic sea-ice cover. Geophysical Research Letters 26: 3469–3472.
Rothrock, D.A., J. Zhang, and Y. Yu. (2003). The arctic ice thickness anomaly of the 1990s: A consistent view from observations and models. Journal of Geophysical Research 108: 3083. doi:10.1029/2001JC001208.
Wadhams, P. (1990). Evidence for thinning of the Arctic ice cover north of Greenland. Nature 345: 795–797.
Wadhams, P., and N.R. Davis. (2000). Further evidence of ice thinning in the Arctic Ocean. Geophysical Research Letters 27: 3973–3975.
Wadhams, P., and N.R. Davis (2001). Arctic sea-ice morphological characteristics in summer 1996. Annals of Glaciology 33: 165–170.
Wadhams, P., N Hughes and J Rodrigues (2011). Arctic sea ice thickness characteristics in winter 2004 and 2007 from submarine sonar transects. J. Geophys. Res., 116, C00E02.
Shakhova, N. and I. Semiletov (2012). Methane release from the East-Siberian Arctic Shelf and its connection with permafrost and hydrate destabilization: First results and potential future development. Geophys. Res., Vol. 14, EGU2012-3877-1.
