A Model for the Vertial Circulation of the Baltic Deep Water

Stigebrandt, Anders

doi:10.1175/1520-0485(1987)017<1772:amftvc>2.0.co;2

Cited by 139 publications

(100 citation statements)

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“…However, provided the basin water initially is homogeneous and lighter than the dense source, the plume will continue to be denser than the basin at all subsequent times (e.g. Baines and Turner, 1969;Stigebrandt 1987). Consequently, the plume will always land on the bottom, and there can be no interleaving of plume water at shallower depths (unless there is more than one source).…”

Section: A Toy Modelmentioning

confidence: 99%

How entraining density currents influence the stratification in a one-dimensional ocean basin

Wåhlin

Cenedese

2006

Deep Sea Research Part II: Topical Studies in Oceanography

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The sensitivity of the basin-scale ocean stratification to the vertical distribution of plume entrainment is being analyzed. A large ocean basin supplied by dense water from an adjoining marginal sea is considered. The dense water flows into the ocean basin as an entraining density current and interleaves at the bottom (or at the level of neutral density), where it deposits a mixture of marginal seaand basin water. As the basin water, i.e. 'old' plume water, is entrained and re-circulated in the plume a stratification develops in the basin. The mixture deposited at the bottom hence contains an increasing fraction of marginal sea water, and the basin density increases with depth as well as with time. A stationary solution in which diffusion of buoyancy from above is important is approached asymptotically in time.Non-diffusive solutions to the initial transient adjustment, as well as the diffusive asymptotic state, have been studied in four different parameterizations of plume entrainment. It is shown that in the transient regime the basin stratification and plume density are highly sensitive to how mixing is parameterized. The stationary diffusive solution that is approached asymptotically in time is less sensitive to parameterization but depends strongly on basin topography, source water density, and buoyancy flux at the surface.

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Section: A Toy Modelmentioning

confidence: 99%

How entraining density currents influence the stratification in a one-dimensional ocean basin

Wåhlin

Cenedese

2006

Deep Sea Research Part II: Topical Studies in Oceanography

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“…The integrated production of the turbulent kinetic energy exceeded the energy loss of inertial oscillations in the surface layer suggesting that additional energy sinks might have been inertial wave radiation during geostrophic adjustment of coastal jets and mesoscale eddies. The diapycnal mixing coefficient (α) of Stigebrandt (1987) was estimated to be 0.87 × 10 −7 m 2 s −2 , several times less than earlier estimates based on the bulk methods.…”

Section: Mixingmentioning

confidence: 55%

“…On the basis of monitoring data for the period 1965-2000, Laine et al (2007) found a continuous decrease in salinity and density stratification until the early 1990s, after which there was a slight increase. Based on independent data for 1987-2008, Liblik and Lips (2011 found that the deep salinities in summer increased after the 1993 major inflow by about 2 g kg −1 . Despite the increased mean stratification strength and more frequent occurrence of hypoxia events (see Chap.…”

Section: 3mentioning

confidence: 99%

“…Based on long-term modelling of the large-scale vertical circulation in the Baltic Proper, Stigebrandt (1987Stigebrandt ( , 2001 concluded that under contemporary conditions the basinwide vertical diapycnal diffusivity (or diapycnal mixing coefficient) in the deep-water pools can be reasonably well described by j ¼ minða=N; j max Þ where α and j max are constants and N is the Brunt-Väisälä frequency. In the horizontally integrated model for the Baltic Proper, Stigebrandt (1987) tuned α to equal 2 × 10 −7 m 2 s −2 .…”

Section: Mixingmentioning

confidence: 99%

“…In the horizontally integrated model for the Baltic Proper, Stigebrandt (1987) tuned α to equal 2 × 10 −7 m 2 s −2 .…”

Section: Mixingmentioning

confidence: 99%

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Recent Change—Marine Circulation and Stratification

Elken

Lehmann

Myrberg

2015

Regional Climate Studies

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This chapter describes recent change in the circulation and stratification of the Baltic Sea. A recent warming trend in sea-surface waters has been clearly demonstrated by in situ measurements, remote sensing data and numerical models. Trends in sea-surface temperature (SST) for the past three to four decades based on remote sensing data generally agree with trends determined from in situ observations. Models suggest the current warming within the Baltic Sea lies within the range experienced during the past 500 years. The salinity and stratification of the deep waters are strongly linked to the major inflows of North Sea water that occur sporadically and bring high-saline water into the deep layers of the Baltic Sea. The major inflows normally occur during winter and spring and bring cold oxygen-rich waters into the deep basins. Since 1996, large inflows have also occurred during summer, bringing in warm low-oxygen water. IntroductionChanges in thermohaline characteristics and stratification of the water column are usually analysed on the basis of data from repeat hydrographic observations, originating from shipborne monitoring programmes and/or permanent coastal and offshore oceanographic stations. Such datasets are described in recent books by Feistel et al. (2008) and Leppäranta and Myrberg (2009). In situ observations are often irregular in space and time, especially for offshore areas; therefore, trends and variability in the ocean state can only be determined by careful pre-processing of the data to address issues such as data homogenisation and the suppression of aliasing errors. In recent decades, horizontal undersampling by in situ measurements has been partially offset by the remote sensing of sea-surface properties from satellites; with these data free of spatial aliasing errors due to their high horizontal resolution. Satellite-derived cloud-free products for sea-surface temperature (SST) have been reasonably accurate since the 1980s. Many of the papers published over the past decade that address trends and variability in the circulation and stratification of the Baltic Sea are based on remote sensing data, often in combination with in situ observations and the results of numerical modelling. Improvements in the physical and numerical features of the models, accompanied by model validation studies, have increased confidence in the realism of the model results. Models provide dynamically balanced gridded datasets over decades or longer, including information for 'noisy' variables such as currents, transport and mixing fluxes. This chapter analyses the recent peer-reviewed literature, extending the findings from earlier review (Box 7.1).

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Deep‐water dynamics and boundary mixing in a nontidal stratified basin: A modeling study of the Baltic Sea

et al. 2014

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Recent results from a tracer release experiment have shown that, similar to many lakes and ocean basins, deep-water mixing in the Baltic Sea is largely determined by mixing processes occurring in the energetic near-bottom region. Due to the complexity and small vertical extent of this region, however, previous modeling studies of the Baltic Sea have so far not been able to provide a numerically and physically sound representation of boundary mixing. Here we discuss first results from a nested high-resolution simulation of the central Baltic Sea that aims at a realistic description of the turbulent bottom boundary layer with the help of new numerical techniques (adaptive coordinates) and state-of-the-art turbulence modeling. Using a comprehensive data set from the Baltic Sea Tracer Release Experiment, we show that the model is able to reproduce the key dynamical processes (near-inertial waves, topographic waves, and a rim current) with excellent accuracy. Boundary mixing triggered by these processes was found to result in simulated basin-scale mixing rates in close agreement with observations, including a seasonal variability that has been emphasized in previous studies. These results may be relevant also for the description of mixing in large lakes and other stratified basins.

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A Model for the Vertial Circulation of the Baltic Deep Water

Cited by 139 publications

References 0 publications

How entraining density currents influence the stratification in a one-dimensional ocean basin

How entraining density currents influence the stratification in a one-dimensional ocean basin

Recent Change—Marine Circulation and Stratification

Deep‐water dynamics and boundary mixing in a nontidal stratified basin: A modeling study of the Baltic Sea

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