The evolving structure of an upwelling filament

Flament, Pierre; Armi, Laurence; Washburn, Libe

doi:10.1029/jc090ic06p11765

Cited by 259 publications

(136 citation statements)

References 15 publications

(10 reference statements)

Supporting

Mentioning

123

Contrasting

Order By: Relevance

“…In the mixed layer, abundant examples of horizontal fronts with temperature and salinity that nearly cancel in their joint effect on density can be found on scales of 10-100 km [i.e., Roden, 1975Roden, , 1989Yuan and Talley, 1992). A few observations have been made of horizontal density fronts on scales finer than 10 km in which the temperature gradient is partially opposed by the salinity gradient [e.g., Flament et al, 1985;Rudnick and Luyten, 1996]. A useful measure of the degree of compensation is the density ratio R defined as the ratio of the relative effect of temperature and salinity on density over a spatial interval.…”

Section: Introductionmentioning

confidence: 99%

Thermohaline variability in the upper ocean

Ferrari¹,

Rudnick²

2000

J. Geophys. Res.

122

128

View full text Add to dashboard Cite

Abstract.The main goal of this exploratory study is to determine how the temperature-salinity relationship changes with horizontal length scale and depth in the ocean. Temperature and salinity were measured on a range of scales from 4 m to 1000 km, towing a SeaSoar along isobars and isopycnals in the subtropical gyre of the North Pacific, during the winter of 1997. The wavelet transform technique is used to compute the horizontal density ratio and thermohaline variability as a function of scale and location. Measurements along an isobar in the mixed layer show that the horizontal density ratio is 1 at all scales observed; that is, horizontal temperature and salinity gradients tend to cancel each other in their effect on density. Thermohaline variability at small scales is intermittent and clusters around large-scale thermohaline anomalies. Below the base of the mixed layer, horizontal gradients of temperature are only partially opposed by salinity, and the density ratio is close to 2. In the thermocline the distribution of thermohaline variability is uniform along isobars but intermittent and colocated at different scales along isopycnals. Density-compensated variability, ubiquitous in the mixed layer, is reduced along deeper isopycnals. Compensation of horizontal temperature and salinity gradients supports recent theoretical ideas that mixing in the winter mixed layer depends on horizontal density gradients.

show abstract

Section: Introductionmentioning

confidence: 99%

Thermohaline variability in the upper ocean

Ferrari¹,

Rudnick²

2000

J. Geophys. Res.

122

128

View full text Add to dashboard Cite

show abstract

“…These filaments are associated with narrow baroclinic jets that form over the continental shelf and flow offshore advecting cold, upwelled water into the open ocean. They are easily identified by their temperature signatures in satellite images of Sea Surface Temperature (SST) (Flament, Armi, & Washburn, 1985). Many projects have focussed on filaments in recent years in Eastern Boundary Systems (i.e.…”

Section: Introductionmentioning

confidence: 99%

Vertical structure, turbulent mixing and fluxes during Lagrangian observations of an upwelling filament system off Northwest Iberia

Barton

Inall

Sherwin

et al. 2001

Progress in Oceanography

View full text Add to dashboard Cite

In August 1998, a recurrent filament located near 42°N off Galicia was sampled as part of the OMEX-II project. Lagrangian and other observations were made on the shelf where the filament arose and offshore in the filament itself under upwelling favourable but fluctuating winds. The shelf drift experiment monitored a change from southward to weak northward net flow as the winds decreased to zero. Shipborne ADCP measurements showed that the shelf was supplying decreasing volumes of water to the filament as the wind speeds decreased. At the shelf edge the internal tide was larger than can be explained by local forcing and there were many unusually large high frequency internal waves with a quasi-sinusoidal form. Turbulence observations revealed enhanced dissipation rates and vertical eddy diffusion coefficients within the shelf thermocline (of order 1 cm 2 s Ϫ1), which appeared to be caused by the breaking of internal wave. A second Lagrangian experiment was executed in the filament some 120 km offshore, which again coincided with a period of wind relaxation. Cross-sections revealed a double cold core and that the offshore flow was limited to a thin surface layer. Substantial onshore flow occurred below 50 m in the centre of the filament, while the strongest and deepest offshore flow coincided with its northern boundary. Turbulent kinetic energy dissipation rate measurements showed very weak mixing below 15 m in the filament core, but enhanced mixing at its boundaries. Four mixed layer drifters released in the filament initially indicated convergence at its southern boundary, marked by strong temperature and salinity contrasts. After the wind became more favourable for upwelling, the drifters accelerated. One drifter traced the full extent of the filament, while the other three escaped from it and began to circulate cyclonically over 28 days in a 100 km diameter loop back towards their release point. Although strong mesoscale activity linked the shelf and ocean regimes, offshore transport in the filament was weak at the time of the experiment and vertical and horizontal re-circulations on a variety of time scales were important. There was sufficient vertical mixing in the thermocline to cause it to thicken and draw some heat into the lower layers during the summer months on the shelf. The amount of heat involved was too little to have a significant impact on the development of a filament over a typical lifetime of a week. 

show abstract

“…The northern boundaries, hereinafter called d-type boundaries (for diffuse transition), usually exhibit a smoother, more diffuse transition in SST from the warm water north of the filament into the filament's center. Both density compensated (e.g., Flament et al, 1985;Kosro and Huyer, 1986;Rienecker and Mooers, 1989) and non-density compensated (e.g., Kosro and Huyer, 1986;Reinecker et al, 1985;Ramp et al, 1991) s-type boundaries have been observed.…”

Section: Introductionmentioning

confidence: 99%

“…Their discussion, however, was not framed in terms of the d-type/s-type nature of oceanic fronts in these regions. Because convergence and subduction appears to occur near intense s-type boundaries (e.g., Flament et al, 1985;, it is possible that albacore orient themselves in order to take advantage of these processes. The subduction process may transport prey out of the nutrient rich filament and into clear warm water offshore.…”

Section: Acoustic Propagation In the Oceanmentioning

confidence: 99%

“…One of the most striking features of cold filament mechanics is the dissimilarity of the boundaries that separate the cold filament from the warmer water in the surrounding area (e.g., Flament et al, 1985;Kosro and Huyer, 1986;. Southern boundaries of filaments, hereinafter called s-type boundaries (for sharp transition), typically have a sharp transition in sea surface temperatures (SST) from cold to hot water.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation