Wednesday, May 9, 2012

4016.txt

date: Tue, 18 Jul 2006 14:57:38 +0100
from: Tim Osborn <t.osbornatXYZxyz.ac.uk>
subject: Re: Law Dome figure
to: Jonathan Overpeck <jtoatXYZxyzrizona.edu>, Ricardo Villalba <ricardoatXYZxyz.cricyt.edu.ar>, Keith Briffa <k.briffaatXYZxyz.ac.uk>, Valerie Masson-Delmotte <Valerie.MassonatXYZxyz.fr>, Eystein Jansen <eystein.jansenatXYZxyz.uib.no>

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Hi all,

(1) Jones/Mann showed (and Mann/Jones used in their reconstruction)
an isotope record from Law Dome that is probably O18 (they say
"oxygen isotopes"). This has a "cold" present-day and "warm" MWP
(indeed relatively "warm" throughout the 1000-1750 period). The
review comments from sceptics wanted us to show this for obvious
reasons. But its interpretation is ambiguous and I think (though I'm
not certain) that it has been used to indicate atmospheric
circulation changes rather than temperature changes by some authors
(Souney et al., JGR, 2002).

(2) Goosse et al. showed Deuterium excess as an indicator of Southern
Ocean SST (rather than local temperature). Goosse et al. also showed
a composite of 4 Antarctic ice core records (3 deuterium, 1
O18). Neither of these comes up to the 20th century making plotting
on the same scale as observed temperature rather tricky!

(3) Dahl-Jensen showed the temperatures obtained by inverting the
borehole temperature profiles. This has a colder MWP relative to the
recent period, which shows strong recent warming.

I have data from (1) and now from (3) too, but not from (2) though I
could ask Hugues Goosse for (2). Anyway, (1) and (2) aren't
calibrated reconstructions like the others in the Southern Hemisphere
figure, so plotting them would alter the nature of the figure.

But if we show only (3) then we will be accused of (cherry-)picking
that (and not showing (1) as used by Mann/Jones) because it showed
what we wanted/expected.

Can I, therefore, leave the SH figure unchanged and can we just
discuss the Law Dome ambiguities in the text?

Cheers

Tim

At 02:41 18/07/2006, Jonathan Overpeck wrote:
>Hi Tim, Ricardo and Keith - Valerie just reminded me that she sent
>this to us all (minus Tim) back in June. There is plenty below for
>discussion in the text, and the Law Dome borehole data can be
>obtained at the site below (http://www.nbi.ku.dk/side95613.htm).
>This is the record that should be added to the SH figure.
>
>Thanks, Peck
>
>>X-Sieve: CMU Sieve 2.2
>>Date: Wed, 28 Jun 2006 12:44:50 +0200
>>From: Val�rie Masson-Delmotte <Valerie.MassonatXYZxyz.fr>
>>Reply-To: Valerie.MassonatXYZxyz.fr
>>Organization: LSCE
>>To: Jonathan Overpeck <jtoatXYZxyzrizona.edu>,
>> Ricardo Villalba <ricardoatXYZxyz.cricyt.edu.ar>,
>> Keith Briffa <k.briffaatXYZxyz.ac.uk>
>>Subject: (pas de sujet)
>>
>>Dear Ricardo and Peck,
>>
>>Here are the references for the Law Dome temperature discussion :
>>
>>* stack of Antarctic ice cores and Law Dome deuterium excess
>>profile (showing large changes in moisture source)
>>
>>Title: *A late medieval warm period in the Southern Ocean as a
>>delayed response to external forcing?*
>>Author(s): *Goosse H*
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=Goosse+H&curr_doc=1/3&Form=FullRecordPage&doc=1/3>,
>>*Masson-Delmotte V*
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=Masson-Delmotte+V&curr_doc=1/3&Form=FullRecordPage&doc=1/3>,
>>Renssen H
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=Renssen+H&curr_doc=1/3&Form=FullRecordPage&doc=1/3>,
>>Delmotte M
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=Delmotte+M&curr_doc=1/3&Form=FullRecordPage&doc=1/3>,
>>Fichefet T
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=Fichefet+T&curr_doc=1/3&Form=FullRecordPage&doc=1/3>,
>>Morgan V
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=Morgan+V&curr_doc=1/3&Form=FullRecordPage&doc=1/3>,
>>van Ommen T
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=van+Ommen+T&curr_doc=1/3&Form=FullRecordPage&doc=1/3>,
>>Khim BK
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=Khim+BK&curr_doc=1/3&Form=FullRecordPage&doc=1/3>,
>>Stenni B
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=Stenni+B&curr_doc=1/3&Form=FullRecordPage&doc=1/3>
>>Source: GEOPHYSICAL RESEARCH LETTERS 31 (6): Art. No. L06203 MAR 17 2004
>>Document Type: Article
>>Language: English
>>Abstract: On the basis of long simulations performed with a
>>three-dimensional climate model, we propose an interhemispheric
>>climate lag mechanism, involving the long-term memory of deepwater
>>masses. Warm anomalies, formed in the North Atlantic when warm
>>conditions prevail at surface, are transported by the deep ocean
>>circulation towards the Southern Ocean. There, the heat is released
>>because of large scale upwelling, maintaining warm conditions and
>>inducing a lagged response of about 150 years compared to the
>>Northern Hemisphere. Model results and observations covering the
>>first half of the second millenium suggest a delay between the
>>temperature evolution in the Northern Hemisphere and in the
>>Southern Ocean. The mechanism described here provides a reasonable
>>hypothesis to explain such an interhemipsheric lag.
>>KeyWords Plus: CLIMATE-CHANGE; ICE CORE; LAW DOME; TEMPERATURES;
>>ANTARCTICA; PALEOCLIMATE; CIRCULATION; MILLENNIUM; RECORDS; SIGNAL
>>
>>* borehole temperature profile from Law Dome :
>>Title: *Monte Carlo inverse modelling of the Law Dome (Antarctica)
>>temperature profile*
>>Author(s): *DahlJensen D*
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=DahlJensen+D&curr_doc=4/15&Form=FullRecordPage&doc=4/15>,
>>Morgan VI
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=Morgan+VI&curr_doc=4/15&Form=FullRecordPage&doc=4/15>,
>>Elcheikh A
>><http://wos.isiknowledge.com/CIW.cgi?SID=X1EEf29O7CO3d9dPA24&Func=OneClickSearch&field=AU&val=Elcheikh+A&curr_doc=4/15&Form=FullRecordPage&doc=4/15>
>>Source: ANNALS OF GLACIOLOGY, VOL 29, 1999 ANNALS OF GLACIOLOGY 29:
>>145-150 1999
>>Document Type: Article
>>Language: English
>>
>>Abstract: The temperature profile in the 1200 m deep Dome Summit
>>South (DSS) borehole near the summit of Law Dome, Antarctica, was
>>measured in 1996, 3 years after the termination of the deep drilling.
>>
>>The temperature profile contains information on past surface
>>temperature over the last 4 ka. This temperature history is
>>determined by the use of a Monte Carlo inverse method in which no
>>constraints are placed on the unknown temperature history and no
>>solution is assumed to be unique. The temperature history is
>>obtained from a selection of equally well-fitting solutions by a
>>statistical treatment.
>>
>>The results show that solutions covering the last 4 ka have a
>>well-developed central value, a most likely temperature history.
>>The temperature record has two well-developed minima at: AD 1250
>>and 1850. From 1850 to the present, temperatures have gradually
>>increased by 0.7 K. The reconstructed temperatures are compared
>>with the stable oxygen isotope (delta(18)O) from the DSS ice core.
>>
>>=> The inversed temperature data are available on the GFY web site at :
>>http://www.nbi.ku.dk/side95613.htm, go to "Dye 3, GRIP, Law Dome
>>temperature reconstructed from borehole measurements"
>>
>>* Regarding the calibration issue there are several publications :
>>- seasonal calibration between 18O and T :
>>
>>[van Ommen and Morgan, 1997a]
>><http://staff.acecrc.org.au/%7Etas/home/reprints/1997%20-%20JGR%20-%20van%20Ommen%20-%20delT.pdf>
>>
>>Tas D. van Ommen and Vin Morgan. Calibrating the ice core
>>paleothermometer using seasonality. J. Geophys. Res.,
>>102(D8):9351-9357, 1997, [AAD Cat. Ref. 7488].
>>
>>[van Ommen and Morgan, 1997b]
>><http://staff.acecrc.org.au/%7Etas/home/reprints/1997%20-%20JGR%20-%20van%20Ommen%20-%20delTcorr.pdf>
>>
>>Tas D. van Ommen and Vin Morgan. Correction to "Calibrating the ice
>>core paleothermometer using seasonality". J. Geophys. Res.,
>>102(D25):30,165, 1997, [AAD Cat. Ref. 8236].
>>
>>- decadal calibration from a high resolution ice core (using
>>deuterium excess)
>>
>>*Recent southern Indian Ocean climate variability inferred from a
>>Law Dome ice core: new insights for the interpretation of coastal
>>Antarctic isotopic records*
>>V. Masson-Delmotte ^A1 , M. Delmotte ^A1 A4 , V. Morgan ^A2 , D.
>>Etheridge ^A3 , T. van Ommen ^A2 , S. Tartarin ^A1 , G. Hoffmann
>>
>>Stable isotopes in water have been measured along a very high
>>accumulation ice core from Law Dome on the east Antarctic coast.
>>These enable a detailed comparison of the isotopic records over
>>sixty years (1934-1992) with local (Antarctic station data) and
>>remote meteorological observations (atmospheric reanalyses and
>>sea-surface temperature estimates) on a seasonal to inter-annual
>>time scale. Using both observations and isotopic atmospheric
>>general circulation model (GCM) results, we quantify the
>>relationships between stable isotopes (d ^18 O, dD and deuterium
>>excess; /d/ = dD -8 � d ^18 O) with site and source temperature at
>>seasonal and decadal time scales, showing the large imprint of
>>source conditions on Law Dome isotopes. These calibrations provide
>>new insights for the quantitative interpretation of temporal
>>isotopic fluctuations from coastal Antarctic ice cores. An abrupt
>>change in the local meridional atmospheric circulation is clearly
>>identified from Law Dome deuterium excess during the 1970s and
>>analysed using GCM simulations.
>>
>>
>>
>>Val�rie.
>
>
>--
>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/

Dr Timothy J Osborn, Academic Fellow
Climatic Research Unit
School of Environmental Sciences, University of East Anglia
Norwich NR4 7TJ, UK

e-mail: t.osbornatXYZxyz.ac.uk
phone: +44 1603 592089
fax: +44 1603 507784
web: http://www.cru.uea.ac.uk/~timo/
sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm

**Norwich -- City for Science:
**Hosting the BA Festival 2-9 September 2006

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