Is there a 230Th deficit in Arctic sediments?

In most of the global ocean, the radionuclide thorium-230 is removed from the water column by adsorption onto particles and deposition in seafloor sediments, at a rate approximately in balance with its local production by the decay of uranium dissolved in seawater, allowing its use in assessing rates of marine processes. However, several previous studies have suggested that the flux of 230Th to the sediments of the Central Arctic is far too small to balance its production in the overlying water column. If this is so, 230Th produced in the low particle-flux Central Arctic basins would be deposited elsewhere, either by boundary scavenging at the margins or by export from the Arctic to lower latitudes. In order to evaluate this possibility, we compare the expected 230Th production and measured inventories for five sites in the Western Arctic, combining previously published 230Th data with reported AMS radiocarbon dates, and find no evidence for a substantial deficit of 230Th in these sediments. Instead, we find evidence for near balance in the 230Th budget during both the Holocene and late glacial periods. These intervals are separated by a brief deglacial period of apparently higher sedimentation rates and 230Th deposition. During the Holocene, the average sedimentary inventory of 230Th at these sites is largely within 30% of the water column production, in good agreement with observations and model results from other ocean basins.