Indications for the transition of Kelvin-Helmholtz instabilities into propagating internal waves in a high turbid estuary and their effect on the stratification stability

Held, Philipp; Kerstin, Bartholomä-Schrottke,; Bartholomä, Alexander

doi:10.1007/s00367-019-00564-4

Cited by 9 publications

(4 citation statements)

References 49 publications

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“…Histogram of aspect ratio from oceanic and estuarine observations of shear instability. The gray line is our estimate of the uncertainty range for asymmetric billows observed on the Ems Estuary (Held et al, 2019). Asterisks represent the current measurements (cf.…”

Section: Resultsmentioning

confidence: 99%

“…Such instabilities are very likely to contribute to the entrainment of fluid mud into upper fluid (Scarlatos & Mehta, 1993). Held et al (2013) and Held et al (2019) pointed out that internal waves breaking associated with shear instability mixes sediment‐laden fluid mud into the upper water layer. The layer with shear instabilities is typically more turbulent than the water above and below, leading to vertical transport of both mass and momentum (e.g., Chang et al, 2016; Geyer et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

“…In a mudflat channel, instability was inferred based on measurements of flow velocity and turbidity but was not documented directly (Adams et al, 1990). Held et al (2019, 2013) documented asymmetrically cusped waves in the Ems Estuary which they identified as Holmboe instability (e.g., Carpenter et al, 2007). In this study, symmetric KH billows growing on a lutocline are documented directly for the first time.…”

Section: Introductionmentioning

confidence: 99%

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Acoustic Observations of Kelvin‐Helmholtz Billows on an Estuarine Lutocline

Fan

Lian

et al. 2020

JGR Oceans

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Kelvin-Helmholtz (KH) instability plays an important role in turbulent mixing in deep oceans, coastal seas, and estuaries. Though widely observed and studied in thermohaline-stratified waters, KH instability has only rarely been observed in sediment-stratified environments. For the first time, we present direct observations of KH billows on an estuarine lutocline by combining echosounder images with velocity and density measurements. The interaction between velocity shear and the density stratification induced by suspended sediments initiated shear instabilities near the bed, indicated by gradient Richardson number (Ri) < 0.25 in the early stages of the observed billows. Once formed, the instabilities enhanced the vertical mixing of momentum, reducing vertical shear and elevating Ri. Linear instability analysis using measured velocity and density profiles well predicts the vertical location and spatial characteristics of the observed billows. These instabilities are believed to contribute to the vertical mixing, entrainment, and transport of estuarine and coastal sediments.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Acoustic Observations of Kelvin‐Helmholtz Billows on an Estuarine Lutocline

Fan

Lian

et al. 2020

JGR Oceans

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“…Based on the ADCP velocity measurements, high resolution estimates of vertical shear were derived, which can be large in ISWs, leading to intense diapycnal mixing. ISWs propagating shoreward can be associated with shear-induced Kelvin-Helmholtz instability (Held et al, 2019;Jones et al, 2020;Moum et al, 2003). Kelvin-Helmholtz instabilities which generate mixing are characterized by a super-critical Richardson number, ie., less than ¼ (Howard, 1961;Miles, 1961;Smyth and Moum, 2012).…”

Section: Adcpmentioning

confidence: 99%