Georg Hoffmann
Scientific
projects and interests
Missions and other activities
Cours de DEA/Cerege 2001
Short CV
1984-1990
study of physics at the Ruhr-Universität Bochum. Diploma thesis on quantum
field theory.
1991-1995 phd thesis at the Max-Planck Institut Hamburg
on water isotope modeling in GCMs
1996-1998 post-doc at the LSCE, since beginning of 1999
in a permanent research position at the LSCE
Scientific projects and interests
- Reconstructing climate variability
over the last millenium.
Ice cores offer a high resolution archive of a bunch of different chemical
and physical tracers that give access to local and far distant climate
parameters. I am particularly interested in the stable isotopes 18O
and Deuterium measured in sub-annual resolution as a local temperature
proxy. The second order quantity Deuterium excess, defined by W.Dansgaard
as the difference between the two stable water isotopes, allows even
estimates of the climate conditions at the evaporation site of the
corresponding precipitation. The ice cores I am dealing with are from
Central Greenland and, recently, from High Andean glaciers too.
- Isotopic cross links of the water
cycle with the carbon cycle. Ice cores bear information on the gaseous composition of the
atmosphere in the past. The isotopic composition of atmospheric oxygen is
influenced by the isotopic composition of the ocean via terrestrial and
marine plant productivity. Measurements of this quantity, d18OAtm, over the
last four glacial-interglacial cycles in the Vostok core from Central
Antarctica therefore give a quantitative hint on the biospheric activity.
Therefore we try to model the global "Dole effect", i.e. the
difference between the atmospheric 18O composition (reconstructed
from the Vostok core for example) and the marine 18O content
(reconstructed from benthic foraminifera in deep sea cores).
- Water isotope modeling with general
circulation models and simple Rayleigh models. The water isotopes are widely used as a paleo
thermometer. d series are reconstructed from very different archives such
as ice cores, sweet water lake sediments or speleothems in order to apply
usually a local spatial isotope/temperature relationship. GCMs offer a
unique possibility to verify this basic assumption and to calibrate more
precisely the isotopic paleo thermometer. They were also used to tag the
origin of the water vapour in order to estimate the influence of varying
path ways of water vapour to the site of condensation.
Publications
1)
Hoffmann, G., Cuntz, M., Werner, M., Jouzel, J. (2005). "A systematic comparison between
the IAEA/GNIP isotope network and Atmospheric General Circulation Models: How
much climate information is in the water isotopes?", in Isotopes in the
Water Cycle - Past, Present and Future of a Developing Science, Aggarwal,
Pradeep K.; Gat, Joel R.; Froehlich, Klaus F.O. (Eds.) 2006.
2) Masson-Delmotte, V., Raffalli-Delerce, Danis, P.A., Yiou, P.,
Stievenard, M., Guibal, F., Mestre, O., Bernard, V., Goosse, H., Hoffmann,
G., and Jouzel, J., 2005,
Changes in European precipitation seasonality and in drought frequencies
revealed by a four-century-long tree-ring isotopic record from Brittany,
western France: Climate Dynamics, v. 24, p. 57-69.
3) Schmidt, G., Hoffmann, G., Shindell, D.T., and Huang, S., 2005, Modelling
atmospheric stable water isotopes and the potential for constraining cloud
processes and stratosphere-troposphere water exchange: J. Geophys. Res., v.
110, p. doi:10.1029/2005JD005790
4) Sturm, K., Hoffmann, G., Langmann, B., and Stichler, W., 2005b, Simulations of
d18O in precipitation by the regional circulation model REMOiso.:
Hydrological Processes, v. 19, p. 3425-3444.
5) Vimeux, F., Gallaire, R., Bony, S., Hoffmann, G., Chiang, J.C., and Fuertes, R., 2005, What
are the climate controls on δD
in precipitation in the Zongo Valley (Bolivia)? Implications for the Illimani
ice core interpretation: EPSL, v. 240, p. 205-220.
6) Hoffmann, G.,
M. Cuntz, C. Weber, P. Ciais, P. Friedlingstein, M. Heimann, J. Jouzel, J.
Kaduk, E. Maier-Reimer, K. Six, and U. Seibt, A model of the Earth's
Dole effect,
Global
Biogeochemical Cycles, 18 (GB1008): doi:10.1029GB002059. 2004
7) Zakharov, V., Imasu, R., Gribanov,
K.G., Hoffmann, G., Jouzel, J. (2004).
"Latitudinal Distribution of Deuterium Ratio in the Atmospheric Water
Vapor Retrieved from IMG/ADEOS Data." Geophysical
Research Letters, 31(2), doi:10.1029/2004GL019433.
8) Roche, D., Paillard, D., Ganipolski,
A., Hoffmann, G. (2004).
"Oceanic oxygen 18 at present-day and LGM: equilibrium simulations with a
coupled climate model of intermediate complexity.", EPSL 218, 317-330.
9) Schotterer, U., Grosjean, M.,
Stichler, W., Ginot, P., Kull, C., Bonnaveira, H., Francou, B., Gäggeler, H.W.,
Gallaire, R., Hoffmann, G., Poyaud, B., Ramirez, E., Schwikowski, M., Taupin, J.D. (2003).
"Glaciers and Climate in the Andes between Equator and 30°S: What is
recorded under extreme environmental conditions?" , Climatic Change, 59, 157-175.
10) Ramirez, E., G. Hoffmann, J.D. Turpin, B. Francou, P. Ribstein, N. Caillon, A.
Landais, J.R. Petit, B. Poyaud, U. Schotterer, and M. Stievenard, A new Andean deep
ice core from the Illimani (6350 m), Bolivia, EPSL, 6674, 1-14, 2003.
Text in PDF
11) Masson-Delmotte, V., M. Delmotte, V.I. Morgan, D. Etheridge, T. van Ommen,
S. Tartarin, and G. Hoffmann, Recent Southern Indian Ocean climate variability inferred from a Law
Dome ice core: new insights for the interpretation of coastal Antarctic
isotopic records, Climate Dynamics, 21, 153-166, 2003.
Text in PDF
12) Hoffmann, G., E. Ramirez,
J.D. Taupin, B. Francou, P. Ribstein, R. Delmas, H. Dürr, R. Gallaire, J.
Simôes, U. Schotterer, M. Stievenard, and M. Werner, Coherent isotope history
of Andean ice cores over the last century, Geophysical Research Letters, 30
(4), 10.1029/2002GL014870, 2003b.
Text in PDF
13) Hoffmann, G.,
Taking the Pulse of the tropical water cycle, Science, 301, 776-777, 2003.
Text in PDF
14) Cuntz, M., P. Ciais, G. Hoffmann, C.E. Allison, R. Francey, W. Knorr, P.P. Tans, J.W.C.
White, and I. Levin, A comprehensive global 3D model of d18O in Atmospheric CO2
2. Mapping the atmospheric signal, Journal of Geophysical Research, 108 (D17),
4528, doi:10.1029/2002JD003154, 2003a.
Text in PDF
15) Cuntz, M., P. Ciais, G. Hoffmann, and W. Knorr, A comprehensive global 3D model of
d18O in Atmospheric CO2 1.
Evaluation of surface fluxes, Journal of Geophysical Research, 108 (D17), 4527,
doi:10.1029/2002JD003153, 2003b
Text in PDF
16) Masson-Delmotte, V.; Raffalli-Delerce;
Danis, P.A.; Yiou, P.; Stievenard, M.; Guibal, F.; Mestre, O.; Bernard, V.;
Goosse, H.; Hoffmann, G.
(2003). "Changes in European seasonality and in drought frequencies by a
four-century-long tree-ring isotopic record from Brittany, western
France." Climate Dynamics, doi10.1007/s00382-004-0458-1.
17) Jouzel, J., F. Vimeux, N. Caillon, G. Delaygue, G. Hoffmann, V. Masson, and F. Parrenin, Temperature
Reconstructions from Antarctic Ice Cores, Journal of Geophysical Research, 108
(D12), 4361, doi:10.1029/2002JD002677,2003.
Text in PDF
18) Jouzel, J., G. Hoffmann, F. Parrenin, and C. Waelbroeck, Atmospheric oxygen 18 and sea-level
changes, Quaternary Science
Reviews, 21 (1-3), 307-314, 2002.
Text in PDF
19) Cuntz M., P. Ciais, and G. Hoffmann, Modelling the continental effect of oxygen isotopes
over Eurasia, Tellus B, 54 (5), 895-911, 2002
Text in PDF
20) Hoffmann, G., J.
Jouzel, and S. Johnsen, The Deuterium Excess Record from Central Greenland over
the Last Millennium: Hints of a North Atlantic Signal during the Little Ice
Age, Journal of Geophysical Research, 106 (D13), 14,265-14,274, 2001.
Text in PDF
21) Hoffmann, G., V.
Masson, and J. Jouzel, Stable Water Isotopes in Atmospheric General Circulation
Models, Hydrological Processes, 14, 1385-1406, 2000.
Text in PDF
22) Johnsen, S., H.B. Clausen, K.M. Cuffey, G. Hoffmann, J. Schwander, and T. Creyts, Diffusion of
stable isotopes in polar firn and ice: the isotope effect in firn diffusion, in
Physics of Ice Records, edited by T. Hondoh, pp. 121-140, Hokkaido University
Press, Sapporo, 2000.
23) Jouzel, J., G. Hoffmann, R.D. Koster, and V. Masson, Water isotopes in precipitation:
Data/model comparison for present-day and past climates, Quaternary Science
Review, 2000 (19), 363-379, 2000.
Text in PDF
24) Werner, M., U. Mikolayewicz, M. Heimann, and G. Hoffmann, Borehole versus Isotope Temperatures on
Greenland:
Seasonality does matter, GRL, 27 (5), 723-726, 2000.
Text in PDF
25) Werner, M., U. Mikolajewics, G. Hoffmann, and M. Heimann, Possible changes of d18O in
precipitation caused by a meltwater event in the North Atlantic, J. Geophys.
Res., 105 (D8), 10,161-10,167, 2000.
26) Werner, M., M. Heimann, and G. Hoffmann, Isotopic Composition and Origin of Polar
Precipitation in Present and Glacial Climate Simulations, Tellus A, 1999.
27) Kjellstroem, E., J. Feichter, and G. Hoffmann, Transport of SF6 and 14CO2 in the
atmospheric general circulation model ECHAM4, Tellus, 52B, 1-18, 1998.
28) Hoffmann, G., M.
Werner, and M. Heimann, The Water Isotope Module of the ECHAM Atmospheric
General Circulation Model - A study on Time Scales from Days to Several Years,
Journal of Geophysical Research, 103, 16,871-16,896, 1998.
Text in PDF
29) Hoffmann, G., and
M. Heimann, Water isotope modeling in the Asian monsoon region, Quat. Int., 37,
115-128, 1997.
30) Jouzel, J., R.B. Alley, K.M. Cuffey, W. Dansgaard, P. Grootes, G.
Hoffmann, S.J. Jonsen,
R.D. Koster, D. Peel, C.A. Shuman, M. Stievenard, M. Stuiver, and J.W.C. White,
Validity of the temperature reconstruction from water isotopes in ice cores, J.
Geophys. Res., 102, 26471--26487, 1997.
Text in PDF
Other
articles and publications
1)
Hoffmann, G.,
2005, Peaks in Climate Research: Nature, v. 438, p. 157.
2)
Hoffmann,
G. and J. Beer
(2004). "Holocene Climate Variability and Climate Forcing." PAGES
Newsletter 12 (3):
18-19.
3)
Hoffmann,
G., Modelling the
Water Isotope Signal in the Quaternary, PAGES Newsletter, 10 (2), 12-13, 2002.
4)
Schmidt,
G., G. Hoffmann,
and D. Thresher, Isotopic tracers in coupled models: A new paleo-tool., PAGES
Newsletter, 7, 10-11, 2001.
5)
Hoffmann,
G., M. Stievenard,
J. Jouzel, J.W.C. White, and S.J. Johnsen, The deuterium excess record from
central Greenland: Modelling and observations, in International Symposium on
Isotope Techniques in the Study of Past and Current Environmental Changes in
the Hydrosphere and the Atmosphere, pp. 591--602, IAEA, Vienna, Austria, 1998.
6)
Jouzel,
J., R.D. Koster, G. Hoffmann, and A. Armengaud, Model Evaluation of the Water Isotope-Climate
Relationship used in Reconstructing Paleotemperatures, in Isotope Techniques
in the Study of Environmental Change, edited by IAEA, pp. 485--502, IAEA, Vienna,
1998.
7)
Werner,
M., M. Heimann, and G. Hoffmann, Stable Water Isotopes In Greenland Ice Cores - ECHAM4 model
simulations versus field measurements, in Isotope Techniques In The Study of
Environmental Change,
edited by IAEA, pp. 603--612, IAEA, Vienna, 1998
8)
Jouzel,
J., R.D. Koster, G. Hoffmann, and A. Armengaud, Model evaluations of the water isotope/climate
relationships used in reconstructing paleotemperatures, in International
Symposium on Applications of Isotope Techniques in Studying Past and Current
Environmental Changes in the Hydrosphere and the Atmosphere, edited by IAEA, IAEA, Vienna, 1997
9)
Hoffmann,
G., and M. Heimann,
Water tracers in the ECHAM GCM, in Isotope techniques in the study of the
past and current environmental changes in the hydrosphere and the atmosphere, pp. 3-14, IAEA, Vienna, 1993
10)
Hoffmann,
G., Wasserisotope
im allgemeinen Zirkulationsmodell ECHAM,
Doktorarbeit, Universität Hamburg, Hamburg, 1995.
11)
Hoffmann, G.,
Das f4
Modell auf dem Gitter, Diplomarbeit, Ruhr-Universiät Bochum, 1989.
Submitted/in prep. Papers
1) LeGrande, A.N., Schmidt, G., Shindell,
D.T., Field, C., Miller, R.L., Faluvegi, G., Koch, D., and Hoffmann, G., 2006, Consitent simulations of multiple
proxy responses to an abrupt climate change event; PNAS - Proceedings of the
National Academy of Sciences of the United States of America, in press.
2) Hoffmann, G., and Vimeux, F., 2006, Deuterium Excess in
Antarctica: A Review, in
Knight, P.S., ed., Glacier Science and Environmental Change, Blackwell
Publishing
3) Hoffmann, G., Cuntz, M., Weber, C., Ciais, P.,
Friedlingstein, P., Heimann, M., Jouzel, J., Kaduk, J., Maier-Reimer, E., Six,
K. (2006). "What drives the Dole effect? A paleo study on the link between
marine sediment and Antarctic ice core records during the Pleistocene.",
in prep.
4) Hoffmann, G., Werner, M., Jouzel, J. (2006).
"Modern temperature-isotope analogue proven valid for the Vostok area.”,
in prep.
5) Jomelli, V., Hoffmann, G., Naveau, P., Brunstein, D., Grancher, D.,
Favier, V., and Rabatel, A., 2006, Evidence of Niña-like conditions during the
Little Ice Age in the tropical Andes: Nature, submitted
Reports
1.)
"Modélisation méso-échelle du climat sud-americain"
by
Etienne Berthier, Manuscript in french language of a Diploma Thesis
Full Text Postscript
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