From	Jonathan T. Overpeck	Date	Mon, 10 Jan 2005 17:20:06 -0700
To	Valerie Masson-Delmotte
CC	Keith Briffa, Eystein Jansen, trond.dokken@bjerknes.uib.no, Ricardo Villalba
Subject	Re: Glaciers Ch 6
V - well said. Eystein and I will be working on your Holo section - more tomorrow. thx, Peck >2 comments > >- the various NH T reconstr use polar records : to my knowledge only >use of melt index that itself does not calibrate properly in Mann's >reconstruction. I sent you Keith winter d18O from Vinther 2003 which >provides a reconstruction of NAO changes (I think this is the more >detailed calibration study for Greenland isotopes). >On a decadal time scale calibration studies for Antarctica (Vostok >and Law Dome, inland vs coastal sites) using available instr records >(50 years) show correct decadal scale temperature signals. Even at >places with subannual resolution like Law Dome I think that you >cannot use the isotopes on a yearly basis but only decadal scale. > >- tropical glaciers : works conducted here on Andean ice cores >together with modelling of isotopes in a GCM all showed a consistent >decadal variability on the 20th century, most of which interpreted >to be related to precip change (see for instance Hoffmann et al, >Science, "Taking the pulse of the tropical water cycle", Science, >2003). For more ancient past periods it is thought that part of the >signal is due to T (and vertical lapse rate change), part to >precip.I would not like to cosign any text claiming for a T >reconstruction based on Andean ice cores. > > >Keith Briffa wrote: > >>I agree with suggestion - there is the problem of the isotopic >>analyses from tropical (and to some extent polar) ice cores still . >>I am not happy simply to show these in a Figure relating to the >>large-scale temperature changes - because we are not sure of the >>extent to which they can be interpreted as such . The various NH >>reconstructions use some polar isotope records but looking at plots >>of the tropical records throws up some strange behavior over the >>last 2000 years . I am not happy to write about these as Valerie >>and Olga are better qualified and because I would like to see more >>formal calibration against even short temperature records . I have >>therefore , not as yet explicitly said anything about these >>tropical records. I will sendthe latest text and latest draft >>FIgure 1 later today >> >>At 10:03 09/01/2005, Jansen@geo.uib.no wrote: >> >>>Dear Olga, >>>My suggestion would be, and I believe this is echoed by Peck, is >>>that the box >>>we produce comes in the overall Holocene sub-chapter, thus to avoid >>>repetition. The figure should mainly give syntheses of the glacier extent >>>variations through the Holocene, if possible, or a fraction of it >>>if data only >>>exists e.g. for the last few millennia, for those regions where there is a >>>reliable data set. Then with text explaining what we think drove these >>>variations. I think it should be a box in Ch6, and could also include the >>>recent trends I have just talked with Atle and he is able to contribute >>>curves for Scandinavia and the Alps into a figure before the end of the week >>>(in a couple of days). He feels putting something together for North America >>>and perhaps New Zealand is feasible, but he cannot do this before the ZOD >>>deadline. Perhaps you might be able? If we get something for the >>>tropics from >>>Lonnie and Ellen and what you have, I will be able to put this together in a >>>figure for the box via assistance here. We can in such a figure leave space >>>open for curves we anticipate including for the First Draft. >>>It might be a good idea to in this figure also include the recent, >>>instrumental evidence for the same regions, akin to what will be in Ch4, and >>>of course, in the next iteration come back to possible joint Ch4 >>>and 6 figure. >>> >>>How does this sound? >>> >>>Cheers, >>>Eystein >> >> >>-- >>Professor Keith Briffa, >>Climatic Research Unit >>University of East Anglia >>Norwich, NR4 7TJ, U.K. >> >>Phone: +44-1603-593909 >>Fax: +44-1603-507784 >> >>http://www.cru.uea.ac.uk/cru/people/briffa/ > > > > >Attachment converted: Macintosh HD:masson 5.vcf (TEXT/ttxt) (000C2383) -- Jonathan T. Overpeck Director, Institute for the Study of Planet Earth Professor, Department of Geosciences Professor, Department of Atmospheric Sciences Mail and Fedex Address: Institute for the Study of Planet Earth 715 N. Park Ave. 2nd Floor University of Arizona Tucson, AZ 85721 direct tel: +1 520 622-9065 fax: +1 520 792-8795 http://www.geo.arizona.edu/ http://www.ispe.arizona.edu/