TY - JOUR

T1 - Observations of a diapycnal shortcut to adiabatic upwelling of Antarctic Circumpolar Deep Water

AU - Silvester, J.M.

AU - Lenn, Y.D.

AU - Polton, J.A.

AU - Rippeth, T.P.

AU - Maqueda, M.M.

N1 - Natural Environment Research Council (NERC); (Grant NE/K500938/1); (Grant NE/HO16007/1)

PY - 2014/11/25

Y1 - 2014/11/25

N2 - In the Southern Ocean, small-scale turbulence causes diapycnal mixing which influences important water mass transformations, in turn impacting large-scale ocean transports such as the Meridional Overturning Circulation (MOC), a key controller of Earth's climate. We present direct observations of mixing over the Antarctic continental slope between water masses that are part of the Southern Ocean MOC. A 12 h time series of microstructure turbulence measurements, hydrography, and velocity observations off Elephant Island, north of the Antarctic Peninsula, reveals two concurrent bursts of elevated dissipation of O(10−6) W kg−1, resulting in heat fluxes ∼10 times higher than basin-integrated Drake Passage estimates. This occurs across the boundary between adjacent adiabatic upwelling and downwelling overturning cells. Ray tracing to nearby topography shows mixing between 300 and 400 m is consistent with the breaking of locally generated internal tidal waves. Since similar conditions extend to much of the Antarctic continental slope where these water masses outcrop, diapycnal mixing may contribute significantly to upwelling.

AB - In the Southern Ocean, small-scale turbulence causes diapycnal mixing which influences important water mass transformations, in turn impacting large-scale ocean transports such as the Meridional Overturning Circulation (MOC), a key controller of Earth's climate. We present direct observations of mixing over the Antarctic continental slope between water masses that are part of the Southern Ocean MOC. A 12 h time series of microstructure turbulence measurements, hydrography, and velocity observations off Elephant Island, north of the Antarctic Peninsula, reveals two concurrent bursts of elevated dissipation of O(10−6) W kg−1, resulting in heat fluxes ∼10 times higher than basin-integrated Drake Passage estimates. This occurs across the boundary between adjacent adiabatic upwelling and downwelling overturning cells. Ray tracing to nearby topography shows mixing between 300 and 400 m is consistent with the breaking of locally generated internal tidal waves. Since similar conditions extend to much of the Antarctic continental slope where these water masses outcrop, diapycnal mixing may contribute significantly to upwelling.

U2 - 10.1002/2014GL061538

DO - 10.1002/2014GL061538

M3 - Article

VL - 41

SP - 7950

EP - 7956

JO - Geophysical Research Letters

JF - Geophysical Research Letters

SN - 0094-8276

IS - 22

ER -