Abstract
The Last Interglacial (LIG) represents an invaluable case study to investigate the response of components of the Earth system to global warming. However, the scarcity of absolute age constraints in most archives leads to extensive use of various stratigraphic alignments to different reference chronologies. This feature sets limitations to the accuracy of the stratigraphic assignment of the climatic sequence of events across the globe during the LIG. Here, we review the strengths and limitations of the methods that are commonly used to date or develop chronologies in various climatic archives for the time span (∼140–100 ka) encompassing the penultimate deglaciation, the LIG and the glacial inception. Climatic hypotheses underlying record alignment strategies and the interpretation of tracers are explicitly described. Quantitative estimates of the associated absolute and relative age uncertainties are provided.Recommendations are subsequently formulated on how best to define absolute and relative chronologies. Future climato-stratigraphic alignments should provide (1) a clear statement of climate hypotheses involved, (2) a detailed understanding of environmental parameters controlling selected tracers and (3) a careful evaluation of the synchronicity of aligned paleoclimatic records. We underscore the need to (1) systematically report quantitative estimates of relative and absolute age uncertainties, (2) assess the coherence of chronologies when comparing different records, and (3) integrate these uncertainties in paleoclimatic interpretations and comparisons with climate simulations.Finally, we provide a sequence of major climatic events with associated age uncertainties for the period 140–105 ka, which should serve as a new benchmark to disentangle mechanisms of the Earth system's response to orbital forcing and evaluate transient climate simulations.
Highlights
Based on eustatic sea level variations, the Last Interglacial covers approximately the time interval between 129 and 116 thousand of years (Dutton and Lambeck, 2012; Masson-Delmotte et al, 2013)
Despite the fact that some NEEM ice core sections are disturbed and folded after the LIG, a chronological climatic sequence back to 128.5 ka has been obtained based on the match to NGRIP and EDML d18Oatm and CH4 on the EDML1 timescale, which is by construction coherent with the EDC3 timescale (Capron et al, 2010; NEEM community members, 2013)
Based on the À403‰ threshold value used in EPICA Dome C (EDC) ice dD to define an interglacial (EPICA Community members, 2004), the timing and duration of the LIG remains largely unchanged in AICC2012 (116.3e132.5 ka) compared to EDC3 (115.6e132.4 ka)
Summary
Based on eustatic sea level variations, the Last Interglacial (hereafter LIG) covers approximately the time interval between 129 and 116 thousand of years (hereafter ka) (Dutton and Lambeck, 2012; Masson-Delmotte et al, 2013). The benthic foraminifera d18O record of the penultimate glacial-interglacial transition from North Atlantic sediment core MD95-2042 is ~6 ka younger when aligned onto the LR04 benthic d18O stack than when its sea surface temperature (SST) is aligned onto the Italian Corchia cave calcite d18O (Drysdale et al, 2009) Alignment strategies such as transferring marine sediment cores onto ice core and speleothem chronologies rely on specific climatic assumptions that are not always clearly stated or robust. We review strengths and limitations of existing absolute constraints, and synchronisation or alignment strategies used in marine (corals, sediments) and terrestrial (speleothems, ice cores, lake and peat sediments) archives (see Fig. 2 and Table S1 for site locations), and provide recommendations on how to best derive LIG chronologies in climatic archives. We propose a sequence of major climatic events with related age uncertainties across the penultimate deglaciation, the LIG period and the last glacial inception (section 9)
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