Abrupt millennial-scale climate change

Three key questions we will address here are what was the geographic extent of the millennial-scale climate events how fast and how much warming occurred and what was the cause of these rapid climate changes It is more difficult to determine short-term climatic events in Antarctic ice because accumulation rates are slower, but it has been addressed by extremely detailed sampling of ice 8D and the 

The5 0-H20of the GISP2 ice core from Greenland as a function of age before the present (BP). Numbered intervals correspond to interstadial excursions called Dansgaard-Oeschger (D/O) events. The data show that most D/O events were associated with greater CH4 concentration. Redrawn from Kennett et al. (2003). 

The mean oxidation time of CH4 in the atmosphere is about 10 y and the atmospheric mixing time between the northern and southern hemispheres is about 1 y thus the methane changes observed in 

An equally remarkable result of millennial-scale climate change research is that D/0 events also occur in locations of the Northern Hemisphere that are far removed from Greenland. Thus, whatever triggered these events brought about a climate effect with a global reach. This observation was pointed out in dramatic fashion by a 

Contemporaneous D/0 signals are shown in Fig. 7.22 for sediment cores from the Santa Barbara Basin (SBB), the Cariaco Basin (CB) in Venezuela, the Bermuda Rise (BR), and the GISP2 ice core. Planktonic foraminiferan 8 0 indicates surface water temperature change in SBB and BR the color reflectance change of the CB sediments is controlled by the oxidation state of the overl5dng waters. There are many locations where Y/D events have been well documented (Broecker, 2004) and many others with the full suite of D/0 events. 

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Bard E. (2002) Climate shock abrupt changes over millennial time scales. Phys. Today 55, 32-38. 

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