Sedimentary Records of Deep Water Export From the Arctic to the North Atlantic Ocean

The export of deep waters from the Arctic to the North Atlantic contributes to North Atlantic Deep Water, a critical component of thermohaline circulation. It is currently unclear whether this connection persisted through the last ice age, thus a well-defined record of Arctic deep water export will improve our understanding of paleoclimate. The budgets of ²³¹Pa and ²³⁰Th in sediment cores from the Arctic Ocean can be used to test the hypothesis of consistent deep water export. Because ²³¹Pa has a weaker particle affinity than ²³⁰Th, it has a longer residence time in the water column and can be affected by advection before scavenging and deposition in sediments. Ratios of ²³¹Pa/²³⁰Th below their production ratio have been observed in sediment cores collected in the central Arctic basin, indicating that ²³¹Pa has been transported away from this region of low particle flux. A lack of observations of high ratios elsewhere in the Arctic to balance these low ratios suggests that ²³¹Pa is being transported out of the Arctic basin to the North Atlantic. However, the existing spatial coverage of ²³¹Pa/²³⁰Th measurements in this region is sparse and generally confined to the 0°-180° meridian. We are investigating the budgets of ²³¹Pa and ²³⁰Th in Arctic sediments in an effort to find the “missing sink” of ²³¹Pa. We will present new measurements of these isotopes in cores collected along the basin margins, where ²³¹Pa may have been scavenged by higher particle concentrations, and within the Fram Strait and Greenland Sea, where deep water exits the Arctic.