MARGO Project Last Glacial Maximum SST Reconstructions ----------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program ----------------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: MARGO Project Last Glacial Maximum SST Reconstructions LAST UPDATE: 3/2010 (Original receipt by WDC Paleo) CONTRIBUTOR: C. Waelbroeck IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2010-021 WDC PALEO CONTRIBUTION SERIES CITATION: MARGO Project Members. 2010. MARGO Project Last Glacial Maximum SST Reconstructions. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2010-021. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: MARGO Project Members. 2009. Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum. Nature Geoscience, Vol. 2, pp. 127-132, February 2009. DOI: 10.1038/NGEO411 ABSTRACT: Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations. The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s. Since that time, several shortcomings of that earlier effort have become apparent. Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project. We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present. GEOGRAPHIC REGION: Global PERIOD OF RECORD: Last Glacial Maximum, 23 - 19 KYrBP DESCRIPTION: An updated synthesis of sea surface temperature reconstructions at the Last Glacial Maximum (23 - 19 KYrBP), from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project. Microfossil and geochemical reconstructions of SST are included, plus assessments of the reliability of individual records. These data are also archived at PANGEA: http://doi.pangaea.de/10.1594/PANGAEA.733406 MARGO Project Members: C. Waelbroeck, A. Paul, M. Kucera, A. Rosell-Melé, M. Weinelt, R. Schneider, A.C. Mix, A. Abelmann, L. Armand, E. Bard, S. Barker, T.T. Barrows, H. Benway, I. Cacho, M.-T. Chen, E. Cortijo, X. Crosta, A. de Vernal, T. Dokken, J. Duprat, H. Elderfield, F. Eynaud, R. Gersonde, A. Hayes, M. Henry, C. Hillaire-Marcel, C.-C. Huang, E. Jansen, S. Juggins, N. Kallel, T. Kiefer, M. Kienast, L. Labeyrie, H. Leclaire, L. Londeix, S. Mangin, J. Matthiessen, F. Marret, M. Meland, A.E. Morey, S. Mulitza, U. Pflaumann, N.G. Pisias, T. Radi, A. Rochon, E.J. Rohling, L. Sbaffi, C. Schäfer-Neth, S. Solignac, H. Spero, K. Tachikawa, and J.-L. Turon. NGS-2008-09-00905 Supplementay Information Definition of the quality flags used in the computation of the mean reliability index. 1. Quality flag for number of samples, qnum qnum = 1 when the number of samples within the LGM interval is > 4 = 2 when the number of samples within the LGM interval is 2 to 4 = 3 when there is only 1 sample within the LGM interval 2. SST reconstruction reliability flag, qrel 2.a. Planktonic foraminifera abundances qrel = 1 when the maximum difference in SST estimates among the 4 techniques < 2°C = 2 when the maximum difference in SST estimates among the 4 techniques is 2 to 4°C = 3 when the maximum difference in SST estimates among the 4 techniques > 4°C or when samples are dominated by only one species (relative abundance > 95%) 2.b. Diatoms and radiolarians abundances The full definition is given in 1. It can be summarized as follows. For Imbrie and Kipp2 derived SST estimates based on diatom and radiolarian assemblages three quality levels have been defined using the communality value obtained for the downcore samples. qrel = 1 communality >0.8. For diatom estimates only: SST difference between radiolarian and diatom based estimate <1.5°C = 2 communality = 0.7 to 0.8. For diatom estimates only: SST difference between radiolarian and diatom based estimate <1.5°C = 3 communality <0.7. For diatom estimates only: SST difference between radiolarian and diatom based estimate > 1.5°C For Modern Analog Technique3 derived estimates of SST and sea ice extent based on the diatom record three quality levels have been defined taking into account the dissimilarity index. qrel = 1 dissimilarity < 0.1 = 2 dissimilarity = 0.1 to 0.2 = 3 dissimilarity = 0.2 to 0.25 Samples with dissimilarity values above 0.25 indicate no-analog situations and have been discarded. 2.c. Dinoflagellate cysts abundances The full definition is given in 4. It can be summarized as follows. qrel = 1 distance between sample and best analog < 37 = 2 distance between sample and best analog = 37 to 74 = 3 distance between sample and best analog > 74 2.d. Alkenones unsaturation ratio qrel = 3 for core depths shallower than 100m, or sites with present day annual mean SST higher than 28.5°C, or colder than 4°C = 2 for core depths shallower than 1000m, or Mediterranean Sea sites, or sites with present day annual mean SST higher than 27.5°C = 1 in other cases 2.e. Planktonic foraminifera Mg/Ca qrel = 1 for near-surface dwelling species (G. ruber, G. sacculifer, N. pachyderma s.) AND core depth shallower than 3000m in Atlantic or shallower than 2000m elsewhere = 2 for non-near surface dwelling species OR core depth larger than 3000m in Atlantic or larger than 2000m elsewhere = 3 for non-near surface dwelling species AND core depth larger than 3000m in Atlantic or larger than 2000m elsewhere DATA: Supplementary data tables S1 through S9, archived in text and Excel format. Data files archived at WDC Paleo and PANGEA: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/margo2009/ http://doi.pangaea.de/10.1594/PANGAEA.733406 Table S1. Comparison of MARGO and PMIP2 mean annual SST anomalies (modern - LGM) for key regions. Table S2. Comparison of MARGO and PMIP2 mean northern hemisphere winter SST anomalies (modern - LGM) for Southern Ocean key regions. Table S3. Diatoms-based LGM SST anomalies. The file header contains a description of the columns content. All SST proxies in the MARGO compilation have been calibrated to pre-1998 long-term average SST (ref.7) and the LGM SST anomalies are here calculated as the differences between WOA98 climatology (ref.5) and the reconstructed values. Table S4. Radiolarians-based LGM SST anomalies. As in Table S1. Table S5. Dinocysts-based LGM SST anomalies. As in Table S1. Table S6. Foraminifera-based LGM SST anomalies. As in Table S1. Table S7. Alkenone-based LGM SST anomalies. As in Table S1. Table S8. Mg/Ca-based LGM SST anomalies. As in Table S1. Table S9. 5°x5° block weighted mean values. The file header contains a description of the columns content. By convention (International Hydrographic Bureau 1953), the meridian of Cape Agulhas (20°E) was taken as the boundary between the Atlantic and Indian Oceans, the meridian of the southern cape of Tasmania (147°E) was taken as the boundary between the Indian and Pacific Oceans and the meridian of Cape Horn (68°W) was taken as the boundary between the Pacific and Indian Oceans. The Nordic Seas and Arctic Ocean were included in the Atlantic Ocean. Supplementary figures, archived in PDF format. Fig. S1. Map of reconstructed minimum LGM SST anomalies. Anomalies are computed as LGM - WOA985 values. (a) Northern hemisphere summer (July-August-September). (b) Northern hemisphere winter (January-February-March). (c) Annual mean. Symbols show the location and proxy-type of the original available data (see Fig. 1). Note the uneven spacing of the diverging colour scheme 6 and isotherms. Fig. S2. Map of reconstructed maximum LGM SST anomalies. (a), (b), (c) As in Figure S1. Fig. S3. Comparison of MARGO and PMIP2 mean annual SST anomalies (modern - LGM). Fig. S4. Comparison of MARGO and PMIP2 mean northern hemisphere winter SST anomalies (modern - LGM). Fig. S5. Comparison of MARGO and PMIP2 mean northern hemisphere summer SST anomalies (modern - LGM). References. 1. Gersonde, R., Crosta, X., Abelmann, A. & Armand, L. K. Sea surface temperature and sea ice distribution of the last glacial Southern Ocean – A circum-Antarctic view based on siliceous microfossil records. Quat. Sci. Rev. 24, 869-896 (2005). 2. Imbrie, J. & Kipp, N. G. in The late Cenozoic glacial ages (ed. Turekian, K. K., pp. 71– 181, Yale Univ. Press, New Haven, Conn., 1971). 3. Prell, W. L. The stability of low-latitude sea-surface temperatures: An evaluation of the CLIMAP reconstruction with emphasis on the positive SST anomalies, Rep. TR025, U.S. Dep. of Energy, Washington, D. C. (1985). 4. de Vernal, A. et al. Reconstruction of sea-surface conditions at middle to high latitudes of the Northern Hemisphere during the Last Glacial Maximum (LGM) based on dinoflagellate cyst assemblages. Quat. Sci. Rev. 24, 897-924 (2005). 5. Conkright, M. et al. NODC Internal Report at khttp://iridl.ldeo.columbia.edu/SOURCES/.NOAA/.NODC/.WOA98/l (NODC, Silver Springs, Maryland, 1998). 6. Light, A. & Bartlein, P. J. The end of the rainbow? Color schemes for improved data graphics. EOS, Transactions of the American Geophysical Union 85, 385 and 391 (2004). 7. Kucera, M., Rosell-Melé, A., Schneider, R., Waelbroeck, C. & Weinelt, M. Multiproxy approach for the reconstruction of the glacial ocean surface (MARGO). Quat. Sci. Rev. 24, 813-819 (2005).