TY - JOUR

T1 - Turbulent mixing in the seasonally-stratified western Irish Sea: a Thorpe Scale perspective

AU - Stansfield, K.L.

AU - Palmer, M.R.

AU - Rippeth, T.P.

AU - Simpson, J.H.

PY - 2013/11/19

Y1 - 2013/11/19

N2 - Abstract. The seasonal thermocline in shelf-seas represents an important biogeophysical barrier to the vertical flux of nutrients into the photic zone. Episodic weakening of this barrier plays an important role in sustaining the sub-surface chlorophyll maximum in summer and hence impacts the carbon draw-down in the seasonally-stratified zones of the shelf seas. Here we present estimates of the rate of turbulent kinetic energy dissipation inferred from microstructure shear probes and compare them with dissipation rates inferred from a standard conductivity-temperature-depth instrument and from a fast thermistor (Thorpe Scale methodology) at a site in the seasonally-stratified Irish Sea. All methods show strong dissipation rates in response to tidal stresses near the bed (order 10−2 Wm−3) with qualitatively similar temporal and spatial patterns. In the interior of the water column, however, only the microstructure shear probe estimates resolve the mixing in the region of the thermocline.

AB - Abstract. The seasonal thermocline in shelf-seas represents an important biogeophysical barrier to the vertical flux of nutrients into the photic zone. Episodic weakening of this barrier plays an important role in sustaining the sub-surface chlorophyll maximum in summer and hence impacts the carbon draw-down in the seasonally-stratified zones of the shelf seas. Here we present estimates of the rate of turbulent kinetic energy dissipation inferred from microstructure shear probes and compare them with dissipation rates inferred from a standard conductivity-temperature-depth instrument and from a fast thermistor (Thorpe Scale methodology) at a site in the seasonally-stratified Irish Sea. All methods show strong dissipation rates in response to tidal stresses near the bed (order 10−2 Wm−3) with qualitatively similar temporal and spatial patterns. In the interior of the water column, however, only the microstructure shear probe estimates resolve the mixing in the region of the thermocline.

U2 - 10.5194/osd-10-2141-2013

DO - 10.5194/osd-10-2141-2013

M3 - Article

VL - 10

SP - 2141

EP - 2155

JO - Ocean Science

JF - Ocean Science

SN - 1812-0784

IS - 6

ER -