Physical and biogeochemical transports structure in the North Atlantic subpolar gyre

Abstract

Physical (mass, heat, and salt) and biogeochemical (nutrients, oxygen, alkalinity, total inorganic carbon, and anthropogenic carbon) transports across the transoceanic World Ocean Circulation Experiment (WOCE) A25 section in the subpolar North Atlantic (4x line) obtained previously [Alvarez et al., 2002, 2003] are reanalyzed to describe their regional and vertical structure. The water mass distribution in the section is combined with the transport fields to provide the relative contribution from each water mass to the final transport values. The water mass circulation pattern across the section is discussed within the context of the basin-scale thermohaline circulation in the North Atlantic, Eastern North Atlantic Central, influenced Antarctic Intermediate, Mediterranean, and Subarctic Intermediate Waters flow northward with 10.3, 5.6, 1.7, and 2.9 Sv, respectively. The total flux of Lower Deep Water (LDW) across the section is 1 Sv northward. A portion of LDW flowing northward in the Iberian Basin recirculates southward within the eastern basin and about 0.7 Sv flow into the western North Atlantic. About 7 Sv of Labrador Seawater (LSW) from the Labrador Sea cross the 4x section within the North Atlantic Current, and 12 Sv of LSW from the Irminger Sea flow southward within the East Greenland Current. Denmark Strait Overflow Water flows over the western flank of the Irminger basin (1.5 Sv), and Iceland Scotland Overflow Water (ISOW) is mainly transported in the Charlie Gibbs Fracture Zone (6 Sv). ISOW remnants flow southward to the eastern basin, contributing to the eastern basin deep ventilation. LSW and the overflows transport CANT southward across the section. This southward CANT transport is overcome by the northward transport in upper layers; finally, CANT is injected into the subpolar gyre where it accumulates. Copyright 2004 by the American Geophysical Union.