Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO)
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ARTICLE IN PRESS Quaternary Science Reviews 24 (2005) 813–819 Multiproxy approach for the reconstruction of the glacial ocean surface (MARGO) Michal Kuceraa,Ã, Antoni Rosell-Mele´ b, RalphSchneider c, Claire Waelbroeckd, Mara Weinelte aDepartment of Geology, Royal Holloway University of London, Egham TW20 0EX, UK bICREA and Institute of Environmental Science and Technology, Universitat Auto`noma de Barcelona, 08193 Bellaterra, Catalonia, Spain cDe´partement de Ge´ologie et Oce´anographie, UMR5805-EPOC, CNRS/Universite´ de Bordeaux1, 33405 Talence Cedex, France dLaboratoire des Sciences du Climat et de l’ Environnement, Laboratoire mixte CNRS-CEA, F-91198 Gif sur Yvette, France eInstitute for Geosciences, University of Kiel, Olshausen Strasse 40, D-24098 Kiel, Germany Received 19 July 2004; accepted 23 July 2004 The oceans and the atmosphere are the two main regional records rarely extending beyond the 19th reservoirs of greenhouse gases and latent heat on Earth. century. Yet, it is only withtheaid of climate records These reservoirs interact through the ocean surface, and spanning thousands of years and encompassing drama- the dynamics of this interaction is a major determinant tically different climatic states of the planet that one can of global climate. Accurate reconstructions of the truly understand the dynamics of the ocean–atmosphere physical state of the global ocean are therefore critical interface and perform meaningful and useful tests of to the understanding of past climate changes. This is in global climate models. Information on the state of the turn required to assess the significance of instrumentally planet in the past, and the amplitude, frequency and observed climate variability, and for the forcing and mechanisms of its changes is of paramount importance validation of global circulation models, which are used to our society, as it is used to inform and guide long- to predict future climate change. term environmental policies and planning and to predict Systematic instrumental measurements of sea surface impact of climate change on land, our habitat. properties exist for only a few decades, withthelongest Any effort to provide past climate records of sufficient extent and time range will have to resort to the use of indirect information: proxies based on biological, ÃCorresponding author. Tel.: +44-1784-443586; fax: +44-1784- 471780. chemical and physical signals preserved in ancient E-mail address: [email protected] (M. Kucera). geological materials. In open-ocean settings, the organic 0277-3791/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2004.07.017 ARTICLE IN PRESS 814 M. Kucera et al. / Quaternary Science Reviews 24 (2005) 813–819 and mineral remains of marine microplankton in deep- proxy data and transfer function techniques, and place sea sediments provide the most comprehensive source of them into a common framework for a multi-proxy suchproxies ( Mix et al., 2001; Henderson, 2002). global glacial ocean reconstruction. However, prior to Unfortunately, it is scientifically and technically not this global synthesis, huge efforts have been put by possible at present to aim to reconstruct a continuous the MARGO working group members into the assembly record in space and time of past climate variation. of new regional or proxy-specific SST reconstructions Instead, a discrete and distinct time interval is needed to which are reported in this volume or in recently focus researchefforts of thescientific community. To be published studies, like the GLAMAP reconstruction useful for validation of climate models, this time interval (Sarnthein et al., 2003; and references therein) and the ought to represent a period of climate markedly TEMPUS compilation (Rosell-Mele´ et al., 1998, 2004). different from that of today, yet not too distant from The contributions presented in this issue form the first the present so that the basic assumptions and para- phase of MARGO: (i) compilation of quality-assessed meters of the climate models need not be modified. and harmonised proxy-specific calibration datasets Withrespect to past ocean surface conditions, parti- and LGM reconstructions, (ii) documentation of in- cularly since the pioneering effort of the CLIMAP group dividual proxies and techniques and (iii) an outline of (climate long-range investigation, mapping, and predic- possible methods of the presentation of the final tion; CLIMAP, 1976, 1981) which started 30 years ago, synthesis. the time of the last glacial maximum (LGM) has served A selection of 8 papers out of 13 herein provides a as common target for climate modelling experiments and series of compilations for different SST proxies (Fig. 1), palaeoenvironmental proxy reconstructions. The LGM including Mg/Ca ratios of planktonic foraminifera interval, around 21,000 years ago, represents the nearest (Barker et al., 2005; Meland et al., 2005) and various of a series of past climatic extremes characterising the transfer function approaches based on census counts of waxing and waning of Quaternary ice ages and as such assemblages of planktonic foraminifera (Barrows and serves as an excellent testing ground for assessment of Juggins, 2005; Chen et al., 2005; Hayes et al., 2005; sensitivity of the Earth’s climatic system. Since the Kucera et al., 2005), diatoms and radiolaria (Gersonde CLIMAP project conclusions were published, a large et al., 2005) as well as dinoflagellate cysts (de Vernal et amount of new sediment material has been recovered, its al. 2005). Moreover, a new Holocene oxygen isotope age determined using ever-improving dating techniques, data synthesis based on planktonic foraminifera is and its palaeoclimatic significance assessed withan ever- presented (Waelbroeck et al., 2005) and a stimulating expanding battery of proxies. Yet, a global synthesis of contribution by Morey et al. (2005) discusses the this material is still lacking. In 1999, an international distribution of planktonic foraminifer assemblages in initiative was launched by the scientific community, with surface sediments as a function of multiple environ- the aim to facilitate a new synthesis of the last ice age mental variables rather than exclusively related to SST. Earth’s surface. The environmental processes of the ice The series of papers addressing glacial surface ocean age: land, ocean, glaciers (EPILOG) initiative com- conditions is followed by a study describing the menced by the IMAGES-PAGES program (the interna- termination of the last glacial period in the Pacific tional marine past global changes study-past global (Kiefer and Kienast, 2005) and this MARGO special changes; core project of the international geosphere- issue ends withtwo contributions dealing withtheissues biosphere programme) provided an updated review of the of mapping techniques for sparsely and non-homoge- progress in palaeoclimatic reconstructions since CLI- neously distributed proxy data (Scha¨ fer-Nethet al., MAP. It summarised the salient points and obstacles in 2005) as well as their comparison with results from the way of a new synthesis, and set a series of benchmarks climate model experiments (Paul and Scha¨ fer-Neth, to allow a precise definition of the LGM chronozone 2005). (Mix et al., 2001). This preface briefly summarises the recommendations Following EPILOG, and withtheabove advance- and common standards agreed at two MARGO work- ments in mind, the MARGO working group was shops which form the innovative guidelines for the new launched in September 2002, when 33 scientists from compilations presented herein, and which will serve as 13 countries met at the Hanse Institute for Advanced the internationally agreed base for the overall multi- Studies in Delmenhorst, Germany, to initiate the proxy synthesis of the last glacial SST reconstruction. ‘‘multiproxy approach for the reconstruction of the For further information on the MARGO guidelines, glacial ocean surface’’ (MARGO). MARGO acts as an their application to the new compilations and the open international project involving data gathering, individual data sets the reader is referred to the sharing and harmonisation, with the aim of producing a MARGO website (http://www.pangaea.de/projects/ new synthesis of sea-surface temperature (SST) and sea- MARGO) and to the individual articles in this volume. ice extent of the glacial ocean. The overall MARGO These guidelines evolved from the major aims of objective is to collate and harmonise all the available MARGO, as formulated at the first meeting in 2002. ARTICLE IN PRESS M. Kucera et al. / Quaternary Science Reviews 24 (2005) 813–819 815 Distribution of MARGO Last Glacial Maximum SST proxy records Diatoms Radiolaria Dinoflagellates Mg/Ca k Foraminifera U37 Fig. 1. The location of proxy records of LGM SST included in the MARGO reconstructions. The alkenone data are from Rosell-Mele´ et al. (2004). All other proxy data are presented in this volume. Compilation of new calibration datasets using con- Oxygen isotopes give a first approximation of the sistent criteria for sample quality, and assignment and surface density of the ocean as the oxygen isotopic definition of modern SST values to eachcalibration composition of planktonic foraminifera is a function sample. of salinity and temperature; Compilation of new LGM SST reconstructions for An increasing number of ocean circulation numerical eachproxy, based on thenew calibrations, providing models compute the isotopic composition of calcite age quality assessment for eachsample using harmo- explicitly (e.g.,