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MARGO
The acronym MARGO is short for "Multiproxy Approach for the
Reconstruction of the Glacial Ocean surface". It stands in for an
international community effort of more than 50 scientists, who pursued
the goal to reconstruct the sea-surface temperature at the Last Glacial
Maximum with the best methods that are available today: methods
that are based on species composition of micro fossils, and
geochemical methods.
The "official" MARGO Website is here: http://margo.pangaea.de/
Example for a global map based on MARGO
This map shows the
reconstructed LGM sea-surface temperature anomaly, computed as the
difference between the Last Glacial Maximum (LGM, between 19,000 and
23,000 years before present) and present day, in units of °C for
the
Northern Hemisphere winter season (January-February-March). Negative
anomalies (blue) denote regions that according to the MARGO
reconstruction were colder than today, positive anomalies (yellow)
point to regions that might have been warmer than today. The squares
mark the geographic locations of the sediment cores that were
investigated by the MARGO project using a variety of methods for
temperature reconstruction. Dark grey areas in the ocean stand in for
those regions to which no anomaly could be assigned because the nearest
data points were too far (more than 2000 km) away. For illustration,
contour lines on land (height contours with a 500 m interval) indicate
the extent of the continental ice
sheets. The grid lines are 30° of longitude and latitude apart. For
the
map an equal-area Hammer projection was chosen.
MARGO achievements
As compared to CLIMAP:
Better geographic coverage
- 696 individual reconstructions of sea-surface temperature help to
fill in gaps
- Especially in northern North Atlantic Ocean and tropical oceans,
less in subtropical areas of the Pacific
Better temporal definition
- 19 to 23,000 years BP (after EPILOG)
- CLIMAP: 16 to 26,000 years BP
Combines results of six proxies
- Four based on microfossil species composition (planktonic
foraminifera, diatoms, dinoflagellates and radiolaria)
- Two geochemical (alkenones with 37 C atoms produced by
unicellular algae/coccolithophores – in slightly different composition
in relation to changes in temperature, magnesium and calcium found
planktic foraminiferal shells)
- More statistically robust
MARGO results regarding the glacial ocean
Broad agreement with CLIMAP but…
- The Nordic Seas were ice-free during summer:
- This confirms an earlier result by the GLAMAP2000 project.
- Strong longitudinal and latitudinal gradients:
- As in CLIMAP,
the largest cooling (-10°C) occurred in the mid-latitude North Atlantic
Ocean and extended into the western Mediterranean (-6°C).
- But the cooling was generally larger in the
eastern parts of the oceans
than in the western parts.
- The cooling was particularly expressed along
the coast of Africa, for example, in the coastal
upwelling area off today's Nambia and South Africa.
- Tropical cooling:
- The tropics (between 15°S and 15°N) cooled on
average by (1.7±1)°C.
- Generally, the cooling was larger in the Atlantic than in
Pacific and Indian Oceans.
- There was even an 1-3°C cooling in western Pacific warm
pool.
- The east-west temperature differences were less pronounced
in the tropical Pacifc and Indian Oceans than in the tropical Atlantic
Ocean.
- Southern Ocean cooling:
- A 2-6°C cooling in the Southern Ocean
indicates a northward migration of the Polar Front.
- Regional warming:
- In the Pacific Ocean, the subtropical gyres
were possibly warmer by 1-2°C.
There were a number of
important projects that preceded MARGO
at the national (German) as well as at the international level:
- CLIMAP
- GLAMAP2000:
Glacial Atlantic Mapping and Prediction (initiated by M. Sarnthein)
- EPILOG
(initiated by E. Bard, P. U.
Clark and A. C.
Mix)
Most of the MARGO work was organized in international Workshops:
- EPILOG workshop at the HANSE Institut for Advanced Studies
in Delmenhorst, Germany (3 to 6. May 1999)
- First MARGO workshop, also at the HANSE Institut
for Advanced Studies in Delmenhorst, Germany (1 to 6
September 2002)
- Second MARGO workshop in Castellet near Barcelona, Spain (15
to 17 September 2003)
- MARGO "writing workshop" at the PAGES project office in
Bern, Switzerland (8 to 10 October 2007)
Second MARGO workshop in
Castellet near Barcelona, Spain
Bibliography (preliminary)
- MARGO Project Members* (2009) Constraints on the magnitude
and patterns of ocean cooling at the Last Glacial Maximum. Nature Geoscience, doi:10.1038/ngeo411
(published online: 18 January 2009),
*) Waelbroeck C, Paul A, Kucera M,
Rosell-Melé A, Weinelt M, Schneider R, Mix AC, Abelmann A,
Armand L,
Bard E, Barker S, Barrows TT, Benway H, Cacho I, Chen MT, Cortijo E,
Crosta X, de Vernal A, Dokken T, Duprat J, Elderfield H, Eynaud F,
Gersonde G, Hayes A, Henry M, Hillaire-Marcel C, Huang CC, Jansen E,
Juggins S, Kallel N, Kiefer T, Kienast M, Labeyrie L, Leclaire H,
Londeix L, Mangin S, Matthiessen J, Marret F, Meland M, Morey AE,
Mulitza S, Pflaumann U, Pisias NG, Radi T, Rochon A, Rohling EJ, Sbaffi
L, Schäfer-Neth C, Solignac S, Spero H, Tachikawa K, Turon JL
- Kucera M, Rosell-Melé
A, Schneider R, Waelbroeck C, Weinelt M (2005) Multiproxy
approach for the reconstruction of the glacial ocean surface (MARGO),
Quaternary Science Reviews 24, 813-819, doi:10.1016/j.quascirev.2004.07.017
- Please see also the other papers in this Special Volume.
- Mix AC, Schneider R, and Bard E (2001) EPILOG –
discussion and reply, IGBP Newsletter 44, 26-27.
- Schneider R, Bard, E and Mix AC (2000) Environmental
Processes of the Ice Age: Land, Ocean, Glaciers. PAGES Newsletter,
June, 2000
- Schneider R, Bard E, and Mix AC (2000) Last Ice Age
global ocean and land surface temperatures: The EPILOG initiative, IGBP
Newsletter 43, 4-7