INTCAL98

The focus of this paper is the conversion of radiocarbon ages to calibrated (cal) ages for the interval 24,00-0 cal BP (Before Present, 0 cal BP = AD 1950), based upon a sample set of dendrochronologically dated tree rings, uranium-thorium dated corals, and varve-counted marine sediment. The 14C age-cal age information, produced by many laboratories, is converted to 14C profiles and calibration curves, for the atmosphere as well as the oceans. We discuss offsets in measured 14C ages and the errors therein, regional 14C age diferences, tree-coral 14C age comparisons and the time dependence of marine reservoir ages, and evaluate decadal vs. single-year 14C results. Changes in oceanic deepwater circulation, especialy for the 16,00-1,00 cal BP interval, are reflected in the Delta14C values of INTCAL98.

Methane and microbiological processes in the Barents Sea

Biogeochemical cycle of methane in the Barents Sea was studied using isotope geochemistry to determine rates of microbial methane oxidation. It was established that microbiological processes (glucose consumption, 14CO2 assimilation, sulfate reduction, and slow methane oxidation) in oxidized surface and weakly reduced sediments are marked by only insignificant change in SO4 concentration and absence of notable increase of total alkalinity and N/NH4 downward sediment cores. Microbial methane productivity was 0.111x10**6 mol/day. Taking into account volume of the water column, microbial methane consumption therein can be as much as 1.8x10**6 mol/day.