Showing papers by "Grant M. Raisbeck published in 2001"

Presence of the solar de Vries cycle (~205 years) during the last ice age

Abstract: Certain characteristic periodicities in the Δ14C record from tree rings, such as the well-known 11-yr Schwabe cycle, are known to be of solar origin. The origin of longer-period cycles, such as the 205-yr de Vries cycle, in the Δ14C record was less certain, and it was possible to attribute it either to solar or climatic variability. Here, we demonstrate that the de Vries cycle is present in 10Be data from the GRIP ice core during the last ice age (25 to 50 kyr BP). Analysis of the amplitude of variation of this cycle shows it to be modulated by the geomagnetic field, indicating that the de Vries cycle is indeed of solar, rather than climatic, origin.

Distribution and behavior of anthropogenic 129I in water masses ventilating the North Atlantic Ocean

Abstract: Iodine 129 is released by reprocessing plants in northwestern Europe in quantities greatly exceeding its natural inventory and other anthropogenic sources. Data are presented from nine profiles of 129I in the Greenland and Norwegian Seas and northern North Atlantic Ocean, collected during the Intergovernmental Oceanographic Commission's Baseline Survey of Contaminants in the North Atlantic Ocean. Anthropogenic 129I is evident throughout the data set. The distribution of 129I in the major water masses sampled provides an excellent illustration of the unique source function of 129I, which results in stronger labeling of the northern-source overflow waters and the Deep Western Boundary Current of the North Atlantic Ocean than for many other tracers. Box models are used to explore the behavior and transport of 129I. These preliminary model simulations agree well with available measurements, pointing the way to future quantitative applications of this tracer.