Interbasin exchange and mixing in the hypolimnion of a large lake: The role of long internal waves

Umlauf, Lars; Lemmin, Ulrich

doi:10.4319/lo.2005.50.5.1601

Cited by 75 publications

(66 citation statements)

References 23 publications

(48 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In lakes, localized and shortterm circulation caused by differential heat exchange and convective flows are well-known (MacIntyre and Melack 1995), in particular between shallow marginal shelves and the main body of a lake. Short-term exchanges between main lake basins and small side basins driven by internal waves and wind speed have been described (Umlauf and Lemmin 2005). However, little is known in lakes about longer term circulation and about annual net exchange of heat between major regions within lakes.…”

Section: Discussionmentioning

confidence: 99%

Differential cooling drives large‐scale convective circulation in Lake Tanganyika

Verburg

Antenucci

Hecky

2011

Limnology & Oceanography

View full text Add to dashboard Cite

Field data, scaling analysis, and three-dimensional numerical experiments demonstrate that the dominant large-scale circulation pattern during the southeast trade winds in Lake Tanganyika (East Africa) is a downwind flow in the metalimnion, with a returning southward upwind flow in the upper region of the epilimnion. This is in the opposite direction to all prior literature available on the lake, which has assumed that the southeast trade winds must drive a northward surface flow due to momentum induced by the wind. The gradient in wind speed and humidity along the length of the lake and the resulting gradient in heat exchange with the atmosphere result in warm water accumulating at the northern end of the lake. The north basin of Lake Tanganyika, thus, acts as a heat sink while the south basin is a net source of heat to the atmosphere. The resulting variation in buoyancy flux is strong enough to drive a convective flow in the upper layer in the opposite direction to the wind. A large-scale convective circulation results in an annual exchange of 6.2 3 10 12 m 3 of water and an annual net transport of heat (averaging 0.2 terawatt) from the northern to the southern region of the lake. Currents in the upper 100-m layer, with a mean flow of 0.2 Sverdrup and flow speed of 0.08 m s 21 , can be described by the superposition of a parallel convective flow with the internal seiche motion.

show abstract

Section: Discussionmentioning

confidence: 99%

Differential cooling drives large‐scale convective circulation in Lake Tanganyika

Verburg

Antenucci

Hecky

2011

Limnology & Oceanography

View full text Add to dashboard Cite

show abstract

“…Those parameters have physical meanings and are thus adjustable by means of laboratory and model [direct numerical simulation (DNS)] experiments. For more details of the parameter determination, see Umlauf and Burchard (2003). In the closure approach we apply here, secondmoment dynamics are reduced to algebraic relations, a simplification that makes such closures suitable for implementation into three-dimensional models; for details, see Burchard and Bolding (2001).…”

Section: Modeling Tools a Turbulence Closure Modelmentioning

confidence: 99%

Impact of Density Gradients on Net Sediment Transport into the Wadden Sea

Burchard

Flöser

Staneva

et al. 2008

Journal of Physical Oceanography

100

View full text Add to dashboard Cite

This study tests the hypothesis that horizontal density gradients have the potential to significantly contribute to the accumulation of suspended particulate matter (SPM) in the Wadden Sea. It is shown by means of long-term observations at various positions in the Wadden Sea of the German Bight that the water in the inner regions of the Wadden Sea is typically about 0.5-1.0 kg m Ϫ3 less dense than the North Sea water. During winter this occurs mostly because of freshwater runoff and net precipitation; during summer it occurs mostly because of differential heating. It is demonstrated with idealized one-dimensional water column model simulations that the interaction of such small horizontal density gradients with tidal currents generates net onshore SPM fluxes. Major mechanisms for this are tidal straining, estuarine circulation, and tidal mixing asymmetries. Three-dimensional model simulations in a semienclosed Wadden Sea embayment with periodic tidal forcing show that SPM with sufficiently high settling velocity (w s ϭ 10 Ϫ3 m s Ϫ1) is accumulating in the Wadden Sea Bight because of density gradients. This is proven through a comparative model simulation in which the dynamic effects of the density gradients are switched off, with the consequence of no SPM accumulation. These numerical model results motivate future targeted field studies in different Wadden Sea regions with the aim to further support the hypothesis.

show abstract

“…Free oscillations of the waterbody, or seiches, are the most prominent features of lake hydrodynamics and play a key role in mechanical transport and biological processes (Gloor et al 1994;Umlauf and Lemmin 2005). Seiches have been a focus of limnological studies since the early investigations by Forel (1895), Watson (1904), and Wedderburn (1907).…”

mentioning

confidence: 99%

Seasonal pattern of rotation‐affected internal seiches in a small temperate lake

Bernhardt

Kirillin

2013

Limnology & Oceanography

View full text Add to dashboard Cite

The aim was to disclose the seasonality in the internal seiches during summer stratification in 2010 within the small, 3 km long, ellipse-shaped, temperate Lake Arendsee (Germany) with simple morphometry. We used observations of temperatures from two thermistor chains (09 April to 24 September), conductivity and temperature profiles, and wind speeds and directions (January to December). To analyze the seasonality in the periods, appearance and modal structure of the seiches, and the wind forcing, we applied spectral analysis on monthly time series of isotherms and wind speeds, and wavelet analysis on 6 month long time series of integrated potential energy and wind speeds. To determine the effect of earth's rotation on seiches, we applied two analytical models based on three-layer density stratification. Earth's rotation affected internal seiches significantly even in a small lake. That was shown by the models and the Burger number being , 1 during stratification. Vertical mode 1 Kelvin-type seiches dominated the internal seiche weather in Lake Arendsee, with their periods changing because of seasonal variations in stratification. Weak, free seiches of vertical mode 2 were amplified during three episodes: (1) in midsummer, when their periods coincided with the inertial period at the lake's latitude, (2) in late spring, and (3) in autumn, both when their periods approached 24 h. The amplifications were caused by resonance between free seiches and wind-forced oscillations at diurnal and inertial periods. Such short-term resonance events, associated with enhanced mixing, are inherent for the seasonal stratification cycle in the most temperate lakes.

show abstract

Interbasin exchange and mixing in the hypolimnion of a large lake: The role of long internal waves

Cited by 75 publications

References 23 publications

Differential cooling drives large‐scale convective circulation in Lake Tanganyika

Differential cooling drives large‐scale convective circulation in Lake Tanganyika

Impact of Density Gradients on Net Sediment Transport into the Wadden Sea

Seasonal pattern of rotation‐affected internal seiches in a small temperate lake

Contact Info

Product

Resources

About