Strong export of Antarctic Bottom Water east of the Kerguelen plateau

概要

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The primary paths for the transport of Antarctic Bottom Water to the global ocean are the deep western boundary currents east of the Antarctic Peninsula and the Kerguelen plateau. Previous ship-based studies found evidence of the Kerguelen deep western boundary current in the distribution of water properties and velocity, but no long-term measurements exist to define the mean flow. Here we use results from a coherent array of eight current-meter moorings to reveal a narrow and intense equatorward flow extending throughout the water column. Two-year mean velocities exceed 20 cm s^[-1] at depths ∼3500 m, the strongest mean deep western boundary current flow yet observed at similar depths. The mean equatorward transport of water colder than 0℃ is 12.3±1.2 x 10^[6] m3 s^[-1], partially compensated by poleward flow of 6.0 x 10^[6] m3 s^[-1] mostly across the eastern end of the array. Below 0.2℃, the net transport is 8.0 x 10^[6] m3 s^[-1], in comparison to 1.9 x 10^[6] m3 s^[-1] in the boundary current carrying dense water from the Weddell Sea into the Atlantic north of the Falkland Plateau. The results confirm that the Kerguelen deep western boundary current is a significant pathway of the deep overturning circulation.