²¹⁰Pb scavenging in the North Atlantic and North Pacific Oceans

The radionuclide ²¹⁰Pb shows significant geographic variations in the extent of its removal from the open ocean water column. This "texture of scavenging" is defined by mapping: (1) the integrated deficiency of ²¹⁰Pb in the water column, relative to its supply from the atmosphere and from in situ decay of dissolved ²²⁶Ra, and (2) inventories of excess ²¹⁰Pb in deep-sea sediments. The ratio of ²¹⁰Pb deficiency to its supply, termed the scavenging effectiveness, is ∼ 20% in the North Equatorial Pacific and ∼ 50% in the North Atlantic. This variation is related to the combined effects of uptake of ²¹⁰Pb onto sinking particles and lateral transport of ²¹⁰Pb to areas of more intense removal. Sediment inventories of excess ²¹⁰Pb, normalized to the ²¹⁰Pb deficiency in the overlying water column, permit evaluation of the relative importance of these effects. In the North Equatorial Pacific virtually all of the ²¹⁰Pb removed from the water column is present in the underlying sediments but in the mid-latitude North Atlantic, the sediments comprise only about 50% of the ²¹⁰Pb removed. The deficiencies of ²¹⁰Pb in the mid-latitude North Atlantic sediments south of 50°N are qualitatively offset by surpluses in high-latitude sediments north of 50°N. Higher primary productivity and new production in the surface waters of the high-latitude North Atlantic and North Equatorial Pacific, relative to the oligotrophic central North Atlantic, may account for the greater fluxes of ²¹⁰Pb to bottom sediments in those areas.