PROTOACTINIUM-231 AND TH-230 ABUNDANCES AND HIGH SCAVENGING RATES IN THE WESTERN ARCTIC-OCEAN

The Canadian Basin of the Arctic Ocean, largely ice covered and isolat ed from deep contact with the more dynamic Eurasian Basin by the Lomon osov Ridge, has historically been considered an area of low productivi ty and particle flux and sluggish circulation. High-sensitivity mass-s pectrometric measurements of the naturally occurring radionuclides pro tactinium-231 and thorium-230 in the deep Canada Basin and on the adja cent shelf indicate high particle fluxes and scavenging rates in this region. The thorium-232 data suggest that offshore advection of partic ulate material from the shelves contributes to scavenging of reactive materials in areas of permanent ice cover.