Ice-rafted debris in the Southern Ocean : potential uses and limitations of ²³⁰Th-normalized fluxes

Abstract

We measured IRD fluxes from 22-5 ka BP in two sediment cores from the Scotia Sea using two different methods. The first, commonly used method, uses the linear sedimentation rate (LSR), dry bulk density, and weight percent of IRD in the sample. The second uses ²³⁰ThTh normalization, which has been proposed as an improved way to determine sediment fluxes in sites with significant lateral redistribution. We found that IRD fluxes calculated using the LSR produced a chronology in closer agreement with prior studies than those calculated using ²³⁰ThTh normalization. Based on the differences in records between the two cores, we conclude that IRD flux records more likely provide information about local ice sheet dynamics than about ice sheet behavior as a whole. IRD flux records may be influenced by differences in local sediment focusing, currents, and distance from the ice sheet.