Article

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: 42.35). 05/2005; 434(7036):975-9. DOI: 10.1038/nature03421
Source: PubMed

ABSTRACT 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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    • "Este es el evento Holoceno que se manifiesta con más intensidad en el registro de Groenlandia . El impacto , duración y características de este evento tienen una expresión geográfica muy diferenciada [ Rohling y Palike , 2005 ] . En el contexto de la PI , este evento no siempre presenta una señal clara , y en la mayoría de las secuencias polínicas continentales no es evidente . "
    07/2015;
    • "In addition, two important issues should be kept in mind. Firstly, the 8.2 ka event was superimposed on a more general aridification/ cooling from 8600 to 7800 cal BP (Rohling and P€ alike, 2005). This is also visible in several of the Southwest Asian records. "
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    ABSTRACT: Climate change is often cited as a major factor in social change. The so-called 8.2 ka event was one of the most pronounced and abrupt Holocene cold and arid events. The 9.2 ka event was similar, albeit of a smaller magnitude. Both events affected the Northern Hemisphere climate and caused cooling and aridification in Southwest Asia. Yet, the impacts of the 8.2 and 9.2 ka events on early farming communities in this region are not well understood. Current hypotheses for an effect of the 8.2 ka event vary from large-scale site abandonment and migration (including the Neolithisation of Europe) to continuation of occupation and local adaptation, while impacts of the 9.2 ka have not previously been systematically studied. In this paper, we present a thorough assessment of available, quality-checked radiocarbon (14C) dates for sites from Southwest Asia covering the time interval between 9500 and 7500 cal BP, which we interpret in combination with archaeological evidence. In this way, the synchronicity between changes observed in the archaeological record and the rapid climate events is tested. It is shown that there is no evidence for a simultaneous and widespread collapse, large-scale site abandonment, or migration at the time of the events. However, there are indications for local adaptation. We conclude that early farming communities were resilient to the abrupt, severe climate changes at 9250 and 8200 cal BP.
    Quaternary Science Reviews 07/2015; in press. DOI:10.1016/j.quascirev.2015.06.022 · 4.57 Impact Factor
    • "The anomalies related to the 8 . 2 ka event in our re - cords extend over several hundred years , which is in accordance with data from many other records . It corroborates the hypothesis that the sudden climate changes related with the freshwater outburst were probably superimposed on a longer - term climatic trend ( Rohling and P€ alike , 2005 ) . "
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    ABSTRACT: The deep and surface water paleoceanographic evolution of the central Nordic Seas over the last 20 thousand years was reconstructed using various micropaleontological, isotopic and lithological proxy data. These show a high spatial and temporal complexity of the oceanic circulation when compared with other records from the region. During early deglaciation a collapse of ice sheets surrounding the Nordic Seas released large amounts of freshwater that affected both the surface and bottom water circulation and significantly contributed to Heinrich stadial 1. During the Younger Dryas, the central Nordic Seas were affected by a last major freshwater plume which probably originated from the Arctic Ocean. When major ice rafting had ceased around 11 ka subsurface temperatures started to rise. However, Atlantic Water advection and subsurface temperatures reached their maximum in the central Nordic Seas later than along the eastern continental margin. That spatio-temporal offset is explained by a gradual re- routing and westward expansion of the Atlantic Water flow during times when the Greenland Sea gyre system became more steadily established. In the Greenland Basin, the Holocene thermal maximum ended c. 5.5 ka, and time-coeveal with an increase in sea-ice export from the Arctic. In the Lofoten Basin the cooling occurred later, after 4 ka, and together with a weakening of the overturning processes. The Neoglacial cooling was reached c. 3 ka, together with low solar irradiance, expanding sea ice and a slight decrease in deep convection. At c. 2 ka subsurface temperatures began to rise again due to an increasing influence of Atlantic Waters.
    Quaternary Science Reviews 06/2015; 121:98-109. DOI:10.1016/j.quascirev.2015.05.013 · 4.57 Impact Factor
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