- Tokyo Geographical Society
- 地学雑誌 (ISSN:0022135X)
- vol.107, no.2, pp.218-233, 1998-04-25 (Released:2009-11-12)
Since the ice core records from central Greenland revealed the presence and significance of millennial-scale large and abrupt climatic changes, widely known as Dansgaard-Oeschger [D-O] Cycles, it becomes the major objective of paleoclimatological researches to clarify their extent, nature, propagation mechanism, and driving force. Although the ultimate driving force is not yet understood, results of recent studies suggest 1) D-O Cycles are global phenomena, 2) they involve complicated interactions and feedback processes among the subsystems including atmosphere, cryosphere, hydrosphere, and biosphere, and 3) they seem tohave initiated from changes in atmospheric circulation.Catastrophic surges of Laurentide Ice Sheet called Heinrich Events are closely associated with D-O Cycles. Although Heinrich Events are likely to have been caused by free oscillationsof ice sheet growth and decay, they were probably not a cause of D-O Cycles but the events seem to have been phase-locked by D-O Cycles. Results of numerical modelling suggest the presence of multi-modes for global deepwater circulation. Switching among the modes is most likely caused by slight variation in hydrogical cycles which change the fresh water balance between Atlantic and Pacific.