Turbulent mixing and its contribution to oxygen flux in the northwestern boundary current region of the Japan/East Sea, April-October 2015

<p>We investigate Marine Heat Waves and Marine Cold Spells (MHWs/MCSs) along the east coast of the Australian continent, a western boundary current region with exceedingly complex dynamics. We provide evidence that episodic MWHs/MCSs along the south-east of the Australian continent are driven by upstream variations in the position, but not necessarily the strength, of the East Australian Current, and that these variations are, in turn, controlled by small-scale (100s of kilometers) eddies that propagate into the region from the east. These eddies are able to alternately 'shut-off' and `turn-on' the poleward transport of warm water by the boundary current in a manner analogous to atmospheric blocking. Precursors to these `blocks' are detectable as much as 60 days prior to the onset of an event. We will discuss the implications of our results for the early prediction of MHW/MCS events.</p>

Download Full-text

Downwelling in Basins Subject to Buoyancy Loss

Journal of Physical Oceanography ◽

10.1175/jpo-d-11-0114.1 ◽

2012 ◽

Vol 42 (11) ◽

pp. 1817-1833 ◽

Cited By ~ 13

Author(s):

Claudia Cenedese

Keyword(s):

Boundary Layer ◽

Turbulent Mixing ◽

Large Scale ◽

Field Experiments ◽

Numerical Study ◽

Vertical Wall ◽

Boundary Current ◽

Boundary Currents ◽

Rossby Radius Of Deformation ◽

Buoyancy Loss

Abstract Recent observational, theoretical, and modeling studies all suggest that the upper part of the downwelling limb of the thermohaline circulation is concentrated in strong currents subject to buoyancy loss near lateral boundaries. This is fundamentally different from the traditional view that downwelling takes place in regions of deep convection. Even when resolving the buoyant boundary currents, coarse-resolution global circulation and climate models rely on parameterizations of poorly known turbulent mixing processes. In this study, the first direct measurements of downwelling occurring within a basin subject to buoyancy loss are obtained. Downwelling is observed near the basin’s vertical wall within the buoyant boundary current flowing cyclonically around the basin. Although the entire basin is cooled, large-scale mean downwelling is absent in the basin interior. Laboratory rotating experiments are conducted to explicitly resolve the turbulent mixing due to convective plumes and the baroclinic eddies generated by the boundary current, and to identify where downwelling takes place. Small vertical velocities can be measured more reliably in the laboratory than in many numerical calculations, whereas the measurement of these small vertical velocities is still a challenge for field experiments. Downwelling is observed near the vertical wall within a boundary layer with a thickness that scales with the baroclinic Rossby radius of deformation, consistent with the dynamical balance proposed by a previous numerical study. Hence, downwelling in the Labrador Sea and Lofoten Basin cyclonic boundary currents may be concentrated in a baroclinic Rossby radius of deformation thick boundary layer in regions with large eddy generation.

Download Full-text

Is a third scale of motion admissible in a boundary-current region?

The European Physical Journal Plus ◽

10.1140/epjp/i2017-11359-2 ◽

2017 ◽

Vol 132 (2) ◽

Author(s):

Fulvio Crisciani ◽

Fabio Cavallini ◽

Renzo Mosetti

Keyword(s):

Boundary Current ◽

Current Region

Download Full-text

Mixing and Transformation in a Deep Western Boundary Current: A Case Study

Journal of Physical Oceanography ◽

10.1175/jpo-d-20-0132.1 ◽

2021 ◽

Author(s):

Carl P. Spingys ◽

Alberto C. Naveira Garabato ◽

Sonya Legg ◽

Kurt L. Polzin ◽

E. Povl Abrahamsen ◽

...

Keyword(s):

Boundary Layer ◽

Turbulent Mixing ◽

Deep Ocean ◽

Western Boundary Current ◽

Mixing Efficiency ◽

Western Boundary ◽

Boundary Current ◽

Mixing Rate ◽

Deep Western Boundary Current ◽

Density Space

AbstractWater-mass transformation by turbulent mixing is a key part of the deep-ocean overturning, as it drives the upwelling of dense waters formed at high latitudes. Here, we quantify this transformation and its underpinning processes in a small Southern Ocean basin: the Orkney Deep. Observations reveal a focussing of the transport in density space as a deep western boundary current (DWBC) flows through the region, associated with lightening and densification of the current’s denser and lighter layers, respectively. These transformations are driven by vigorous turbulent mixing. Comparing this transformation with measurements of the rate of turbulent kinetic energy dissipation indicates that, within the DWBC, turbulence operates with a high mixing efficiency, characterized by a dissipation ratio of 0.6 to 1 that exceeds the common value of 0.2. This result is corroborated by estimates of the dissipation ratio from microstructure observations. The causes of the transformation are unravelled through a decomposition into contributions dependent on the gradients in density space of the: dianeutral mixing rate, isoneutral area, and stratification. The transformation is found to be primarily driven by strong turbulence acting on an abrupt transition from the weakly-stratified bottom boundary layer to well-stratified off-boundary waters. The reduced boundary-layer stratification is generated by a downslope Ekman flow associated with the DWBC’s flow along sloping topography, and is further regulated by submesoscale instabilities acting to re-stratify near-boundary waters. Our results provide observational evidence endorsing the importance of near-boundary mixing processes to deep-ocean overturning, and highlight the role of DWBCs as hot spots of dianeutral upwelling.

Download Full-text

Turbulent Mixing induced by Cold Water Intrusion over the Southwestern East Sea

Journal of Coastal Research ◽

10.2112/si85-096.1 ◽

2018 ◽

Vol 85 ◽

pp. 476-480

Author(s):

Seongbong Seo ◽

Young-Gyu Park ◽

Chanhyung Jeon ◽

Hong Sik Min ◽

Dong Guk Kim ◽

...

Keyword(s):

Turbulent Mixing ◽

Cold Water ◽

East Sea ◽

Water Intrusion

Download Full-text

On the Role of Turbulent Mixing Produced by Vertical Shear Between the Brazil Current and the Intermediate Western Boundary Current

Journal of Geophysical Research Oceans ◽

10.1029/2019jc015338 ◽

2020 ◽

Vol 125 (1) ◽

Cited By ~ 2

Author(s):

Cauê Z. Lazaneo ◽

Dante C. Napolitano ◽

Ilson C. A. Silveira ◽

Amit Tandon ◽

Daniel G. MacDonald ◽

...

Keyword(s):

Turbulent Mixing ◽

Western Boundary Current ◽

Vertical Shear ◽

Western Boundary ◽

Boundary Current ◽

Brazil Current

Download Full-text

Characterising primary productivity measurements across a dynamic western boundary current region

Deep Sea Research Part I Oceanographic Research Papers ◽

10.1016/j.dsr.2015.02.010 ◽

2015 ◽

Vol 100 ◽

pp. 105-116 ◽

Cited By ~ 7

Author(s):

Jason D. Everett ◽

Martina A. Doblin

Keyword(s):

Primary Productivity ◽

Western Boundary Current ◽

Western Boundary ◽

Boundary Current ◽

Current Region ◽

Productivity Measurements

Download Full-text

A Quality Control Procedure for Climatological Studies Using Argo Data in the North Pacific Western Boundary Current Region

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-15-0140.1 ◽

2016 ◽

Vol 33 (12) ◽

pp. 2717-2733 ◽

Cited By ~ 1

Author(s):

Wenjing Jia ◽

Dong Wang ◽

Nadia Pinardi ◽

Simona Simoncelli ◽

Andrea Storto ◽

...

Keyword(s):

Quality Control ◽

North Pacific ◽

Western Boundary Current ◽

Western Boundary ◽

Control Procedure ◽

Boundary Current ◽

The North ◽

Current Region ◽

The Impact ◽

The North Pacific

AbstractA quality control (QC) procedure is developed to estimate monthly mean climatologies from the large Argo dataset (2005–12) over the North Pacific western boundary current region. In addition to the individual QC procedure, which checks for instrumental, transmission, and gross errors, the paper describes and shows the impact of climatological checks (collective QC) on the quality of both processed profiles and resultant climatological distributions. Objective analysis (OA) is applied progressively to produce the gridded climatological fields. The method uses horizontal regional climatological averages defined in five regime-oriented subregions in the Kuroshio area and the Japan Sea. Performing the QC procedure on specific coherent subregions produces improved profiling data and climatological fields because more details about the local hydrodynamics are taken into consideration. Nonrepresentative data and random noises are more effectively rejected by this method, which has value both in defining a climatological mean and identifying outlier data. Assessing with both profiling and coordinated datasets, the agreement is reasonably good (particularly for those areas with abundant observations), but the results (although already smoothed) can capture more detailed or mesoscale features for further regional studies. The method described has the potential to meet future challenges in processing accumulating Argo observations in the coming decades.

Download Full-text