THE SHARP RISE OF DELTA-C-14 CA. 800 CAL BC - POSSIBLE CAUSES, RELATED CLIMATIC TELECONNECTIONS AND THE IMPACT ON HUMAN ENVIRONMENTS

In this study we report on accelerator mass spectrometry (AMS) wiggle- match dating of selected macrofossils from organic deposits ca. 800 ca l BC (ca. 2650 sp). Eased on paleological, archaeological and geologic al evidence, we found that the sharp rise of atmospheric C-14 between 850 and 760 cal Be corresponds to the following related phenomena: 1. In European raised bog deposits, the changing spectrum of peat forming mosses and a sharp decline in decomposition of the peat indicate a su dden change from relatively dry and warm to cool, moist climatic condi tions. 2. As a consequence of climate change, there was a fast and con siderable rise of the groundwater table so that pest growth started in areas that were already marginal from a hydrological point of view. 3 . The rise of the groundwater table in low-lying areas of the Netherla nds resulted in the abandonment of settlement sites. 4. The contempora neous earliest human colonization of newly emerged salt marshes in the northern Netherlands (after loss of cultivated land) may have been re lated to thermal contraction of ocean water, causing a temporary stagn ation in the relative sea-level rise. Furthermore, there is evidence f or synchronous climatic change in Europe and on other continents (clim atic teleconnections on both hemispheres) ca. 2650 BP. We discuss redu ced solar activity and the related increase of cosmic rays as a cause for the observed climatological phenomena and the contemporaneous rise in the C-14-content of the atmosphere. Cosmic rays may have been a fa ctor in the formation of clouds and precipitation, and in that way cha nges in solar wind were amplified and the effects induced abrupt clima te change.