Centennial-scale climate cooling with a sudden cold event around 8.200 years ago. Nature 434: 975-979

Southampton Oceanography Centre, Southampton SO14 3ZH, UK.
Nature (Impact Factor: 41.46). 05/2005; 434(7036):975-9. DOI: 10.1038/nature03421
Source: PubMed


The extent of climate variability during the current interglacial period, the Holocene, is still debated. Temperature records derived from central Greenland ice cores show one significant temperature anomaly between 8,200 and 8,100 years ago, which is often attributed to a meltwater outflow into the North Atlantic Ocean and a slowdown of North Atlantic Deep Water formation--this anomaly provides an opportunity to study such processes with relevance to present-day freshening of the North Atlantic. Anomalies in climate proxy records from locations around the globe are often correlated with this sharp event in Greenland. But the anomalies in many of these records span 400 to 600 years, start from about 8,600 years ago and form part of a repeating pattern within the Holocene. More sudden climate changes around 8,200 years ago appear superimposed on this longer-term cooling. The compounded nature of the signals implies that far-field climate anomalies around 8,200 years ago cannot be used in a straightforward manner to assess the impact of a slowdown of North Atlantic Deep Water formation, and the geographical extent of the rapid cooling event 8,200 years ago remains to be determined.

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    • "Within the same time interval, increased abundance of G. bulloides, higher δ 13 C G. bulloides values, and positive shifts in marine algal biomarkers (Figs. 6, 7, 8b) suggest enhanced productivity in the water column. The associated lower SSTs at ~8.2 ka (Fig. 8a) add evidence to an abrupt SST minimum related to the cold B8.2 ka^ event (Rohling and Pälike 2005; Marino et al. 2009; Rohling et al. 2015). 8.0–7.7 ka (interruption of sapropelic deposition) The recorded interruption of S1 at ~8.0 ka in the south Limnos Basin M4-G core features cooler conditions in the water column as indicated by alkenone-based SSTs (minimum at 7.8 ka; Fig. 8a), and the shift of δO 18 G. bulloides records toward larger values (Fig. 8c); the latter could also be related to freshwater inflow. "
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    ABSTRACT: Combined micropaleontological and geochemical analyses of the high-sedimentation gravity core M-4G provided new centennial-scale paleoceanographic data for sapropel S1 deposition in the NE Aegean Sea during the Holocene Climatic Optimum. Sapropel layer S1a (10.2–8.0 ka) was deposited in dysoxic to oxic bottom waters characterized by a high abundance of benthic foraminiferal species tolerating surface sediment and/or pore water oxygen depletion (e.g., Chilostomella mediterranensis, Globobulimina affinis), and the presence of Uvigerina mediterranea, which thrives in oxic mesotrophic-eutrophic environments. Preservation of organic matter (OM) is inferred based on high organic carbon as well as loliolide and isololiolide contents, while the biomarker record and the abundances of eutrophic planktonic foraminifera document enhanced productivity. High inputs of terrigenous OM are attributed to north Aegean borderland riverine inputs. Both alkenone-based sea surface temperatures (SSTs) and δO18G. bulloides records indicate cooling at 8.2 ka (S1a) and ~7.8 ka (S1 interruption). Sapropelic layer S1b (7.7–6.4 ka) is characterized by rather oxic conditions; abundances of foraminiferal species tolerant to oxygen depletion are very low compared with the U. mediterranea rise. Strongly fluctuating SSTs demonstrate repeated cooling and associated dense water formation, with a major event at 7.4 ka followed by cold spells at 7.0, 6.8, and 6.5 ka. The prominent rise of the carbon preference index within the S1b layer indicates the delivery of less degraded terrestrial OM. The increase of algal biomarkers, labile OM-feeding foraminifera and eutrophic planktonic species pinpoints an enhanced in situ marine productivity, promoted by more efficient vertical convection due to repeated cold events. The associated contributions of labile marine OM along with fresher terrestrial OM inputs after ~7.7 ka imply sources alternative/additional to the north Aegean riverine borderland sources for the influx of organic matter in the south Limnos Basin, plausibly related to the inflow of highly productive Marmara/Black Sea waters.
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    • "A potential cause is related to the complex interplay of regional monsoon systems (African, Indian and Siberian) in response to longterm centennial cooling between ca. 8600 and 8000 years BP, ultimately linked to solar forcing (Rohling and Pälike 2005), later intensified by the large magnitude 8·2k event via climate system feedbacks stemming from the North Atlantic Ocean (Alley and Ágústdóttir 2005;Barber et al. 1999;Born and Levermann 2010;Clark et al. 2001;Overpeck and Cole 2006). "

    No preview · Article · Jan 2016 · Environmental Archaeology
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    • "According to Richard Tipping et al. (2012) the old paradigm of slow, gradual change (Lamb 1977; 1995) has been replaced by one in which change can be described as abrupt, occurring over short timescales of centuries or less, separated by comparatively long periods of quasi-stasis (Mayewski et al. 2004). The 8.2ka years event was part of a climatic cooling period from c. 8600 to 8000 calBP (Rohling, Pälike 2005; Thomas et al. 2007; Walker et al. 2012) that interrupted the long-term trend of rising early- Holocene temperatures. The event lasted approx. "
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    ABSTRACT: At 8200 calBP, the beginning of the Atlantic period, there was a drastic change from warm and humid climatic conditions to cold conditions. The abrupt cooling at 8200 calBP has been documented in different parts of Europe. In western, and some parts of southern, Europe, this event was a trigger for new forms of economy and migrations of groups of Neolithic farmers. This paper considers the different ways in which ceramic traditions developed in eastern Europe in the steppe, steppe-forest and forest zones as a result of the rapid climate changes at about 8200 calBP.
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