The Sharp Rise of DELTA14C ca. 800 cal BC: Possible
Causes, Related Climatic Teleconnections and the Impact on Human
Environments
Bas van Geel, Johannes van der Plicht, M. R. Kilian,, E. R. Klaver,
J. H. M. Kouwenberg, H. Renssen, I. Reynaud-Farrera and H. T.
Waterbolk
In this study we report on accelerator mass spectrometry (AMS)
wiggle-match dating of selected macrofossils from organic deposits ca.
800 cal BC (ca. 2650 BP). Based on
paleological, archaeological and geological evidence, we found that the
sharp rise of atmospheric 14C between 850 and 760 cal BC
corresponds to the following related phenomena:
- In European raised bog deposits, the changing spectrum of peat
forming mosses and a sharp decline in decomposition of the peat indicate
a sudden change from relatively dry and warm to cool, moist climatic
conditions.
- As a consequence of climate change, there was a fast and
considerable rise of the groundwater table so that peat growth started
in areas that were already marginal from a hydrological point of view.
- The rise of the groundwater table in low-lying areas of the
Netherlands resulted in the abandonment of settlement sites.
- The contemporaneous earliest human colonization of newly emerged
salt marshes in the northern Netherlands (after loss of cultivated land)
may have been related to thermal contraction of ocean water, causing a
temporary stagnation in the relative sea-level rise.
Furthermore, there is evidence for synchronous climatic change in
Europe and on other continents (climatic teleconnections on both
hemispheres) ca. 2650 BP. We discuss reduced solar
activity and the related increase of cosmic rays as a cause for the
observed climatological phenomena and the contemporaneous rise in the
14C-content of the atmosphere. Cosmic rays may have been a factor in the
formation of clouds and precipitation, and in that way changes in solar
wind were amplified and the effects induced abrupt climate change.
[Radiocarbon Volume 40, Numbers 1-2, 1998]
