Directly measured mid-depth circulation in the northeastern North Atlantic Ocean

Abstract

The circulation of water masses in the northeastern North Atlantic Ocean has a strong influence on global climate owing to the northward transport of warm subtropical water to high latitudes. But the ocean circulation at depths below the reach of satellite observations is difficult to measure, and only recently have comprehensive, direct observations of whole ocean basins been possible. Here we present quantitative maps of the absolute velocities at two levels in the northeastern North Atlantic as obtained from acoustically tracked floats. We find that most of the mean flow transported northward by the Gulf Stream system at the thermocline level (about 600 m depth) remains within the subpolar region, and only relatively little enters the Rockall trough or the Nordic seas. Contrary to previous work, our data indicate that warm, saline water from the Mediterranean Sea reaches the high latitudes through a combination of narrow slope currents and mixing processes. At both depths under investigation, currents cross the Mid-Atlantic Ridge preferentially over deep gaps in the ridge, demonstrating that sea-floor topography can constrain even upper-ocean circulation patterns.

Nitrous oxide in the North Atlantic Ocean

“…LSW with low N 2 O concentrations is transported either along the eastern continental slope of America or across the Charlie-Gibbs-Fracture-Zone (Bower et al, 2002). It flows into the eastern subtropical basin at 500-2000 m (Rhein, 2000;Alvarez et al, 2004), and spreads north-and southwards (Bower et al, 2002;Rhein, 2000). In the western basin N 2 O concentrations and profiles are in agreement with profiles published by Yoshinari (1976), who also found maximum values in water masses with lower oxygen concentrations.…”

“…Hydrographic processes likely explain the shape of profiles, especially the advection of Labrador Sea Water (LSW) into the eastern basin. LSW with low N 2 O concentrations is transported either along the eastern continental slope of America or across the Charlie-Gibbs-Fracture-Zone (Bower et al, 2002). It flows into the eastern subtropical basin at 500-2000 m (Rhein, 2000;Alvarez et al, 2004), and spreads north-and southwards (Bower et al, 2002;Rhein, 2000).…”

Diversity, distribution and spatial structure of the cold-water coral fauna of the Azores (NE Atlantic)

“…Large-scale circulation is dominated by two eastward-flowing branches of the Gulf Stream: the cold North Atlantic Current (NAC) in the north, crossing the MAR between 45-48 • N (Bower et al, 2002), and the warm Azores Current (AzC) in the south, which crosses the MAR between 34-36 • N (Alves and Verdière, 1999). One additional eastward flow can be traced between the NAC and the AzC around 39-42 • N (Reverdin et al, 2003).…”

Directly measured currents and estimated transport pathways of Atlantic Water between 59.5°N and the Iceland–Faroes–Scotland Ridge

“…But some water will split off through the banks towards Scotland, and the remainder will curve west following the Iceland slope and the RR (Bower et al, 2002). Some of this recirculating water, which increases in strength with depth, may upon reaching the deeper gaps in , allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material for any purpose, even commercially, provided the original work is properly cited and states its license.…”