Internal waves Research Papers - Academia.edu (original) (raw)

Reflecting internal gravity waves in a stratified fluid preserve their frequency and thus their angle with the gravitational directi on. This leads to a focusing or defocus- ing of the waves at boundaries that are neither hor izontal nor... more

Reflecting internal gravity waves in a stratified fluid preserve their frequency and thus their angle with the gravitational directi on. This leads to a focusing or defocus- ing of the waves at boundaries that are neither hor izontal nor vertical. Previous theoreti- cal and experimental work has demonstrated how this can result in the internal wave en- ergy being focused

Proteus mirabilis colonies exhibit striking geometric regularity. Basic microbiological methods and imaging techniques were used to measure periodic macroscopic events in swarm colony morphogenesis. We distinguished three initial phases... more

Proteus mirabilis colonies exhibit striking geometric regularity. Basic microbiological methods and imaging techniques were used to measure periodic macroscopic events in swarm colony morphogenesis. We distinguished three initial phases (lag phase, first swarming phase, and first consolidation phase) followed by repeating cycles of subsequent swarming plus consolidation phases. Each Proteus swarm colony terrace corresponds to one swarming-plus-consolidation cycle. The duration of the lag phase was dependent upon inoculation density in a way that indicated the operation of both cooperative and inhibitory multicellular effects. On our standard medium, the second and subsequent swarm phases displayed structure in the form of internal waves visible with reflected and dark-field illumination. These internal waves resulted from organization of the migrating bacteria into successively thicker cohorts of swarmer cells. Bacterial growth and motility were independently modified by altering th...

Hummocky cross-stratification (HCS) is considered a diagnostic structure of surface storm activity at the shoreface–offshore transition. However, the origin of HCS is still debated. Laboratory experiments have not yet reproduced it and... more

Hummocky cross-stratification (HCS) is considered a diagnostic structure of surface storm activity at the shoreface–offshore transition. However, the origin of HCS is still debated. Laboratory experiments have not yet reproduced it and direct observations on the continental shelves do not exist. Most hydrodynamic interpretations invoke pure oscillatory flows, unidirectional-dominated combined flows and oscillatory-dominated flows, but they all share the assumption of HCS to reflect the combined action of surface storm waves and related currents. Within this context of uncertainties, internal waves (gravity waves propagating along the pycnocline) provide an alternative mechanism to explain the origin of HCS. Internal waves breaking on the shelf create episodic high-turbulence events and induce upslope- and downslope currents as well as oscillatory flows at the depth where the pycnocline intersects the sea floor. In this scenario, both the oscillatory- and the unidirectional components needed for HCS to form are not necessarily linked to surface storm waves, but can occur at various depth as far and near there is a pycnocline where internal waves can form.

Nonlinear dynamics of surface and internal waves in a stratified ocean under the influence of the Earth's rotation is discussed. Attention is focussed upon guided waves long compared to the ocean depth. The effect of rotation on... more

Nonlinear dynamics of surface and internal waves in a stratified ocean under the influence of the Earth's rotation is discussed. Attention is focussed upon guided waves long compared to the ocean depth. The effect of rotation on linear processes is reviewed in detail as well as the existing nonlinear models describing weakly and strongly nonlinear dynamics of long waves. The

The Labani Channel is one of the entry passages of Indonesian Throughflow (ITF) in Makassar Strait. The Channel has strong internal tidal energy which is released due to narrowing passage of the strait. Internal tide is one of the main... more

The Labani Channel is one of the entry passages of Indonesian Throughflow (ITF) in Makassar Strait. The Channel has strong internal tidal energy which is released due to narrowing passage of the strait. Internal tide is one of the main energy sources which causes mixing processes in the oceans. The purpose of this research is to estimate the turbulent mixing by using the Thorpe scale approach. Field observation was carried out on 7-8 of June, 2013 in the Labani Channel, Makassar Strait. A CTD (an instrument with conductivity, temperature and depth sensors) wase cast twelve times during one tidal cycle (24 hours). The results showed that the Labani Channel has an internal tide with a semidiurnal period. The average value of Kρ in the Labani Channel is 2.44 x 10-3 ± 4.73 x 10-3 m2 s-1 and the highest value is found in the deep layer, 2.61 x 10-3 ± 1.67 x 10-3 m2 s-1. This is presumably due to a strong internal tide there. The strong effect of the internal tide occurred particularly during the low tide when the water mass was induced to the deep layer.

Tropical cyclones (TCs) often change intensity as they move over mesoscale oceanic features, as a function of the oceanic mixed layer (OML) thermal response (cooling) to the storm's wind stress. For example, observational evidence... more

Tropical cyclones (TCs) often change intensity as they move over mesoscale oceanic features, as a function of the oceanic mixed layer (OML) thermal response (cooling) to the storm's wind stress. For example, observational evidence indicates that TCs in the Gulf of Mexico rapidly weaken over cyclonic cold core eddies (CCEs) where the cooling response is enhanced, and they rapidly intensify over anticyclonic warm features such as the Loop Current (LC) and Warm Core Eddies (WCEs) where OML cooling is reduced. Understanding this contrasting thermal response has important implications for oceanic feedback to TCs' intensity in forecasting models. Based on numerical experimentation and data acquired during hurricanes Katrina and Rita, this dissertation delineates the contrasting velocity and thermal response to TCs in mesoscale oceanic eddies. Observational evidence and model results indicate that, during the forced stage, the wind-driven horizontal current divergence under the sto...

We report a novel and spectacular instability of a fluid surface in a rotating system. In a flow driven by rotating the bottom plate of a partially filled, stationary cylindrical container, the shape of the free surface can spontaneously... more

We report a novel and spectacular instability of a fluid surface in a rotating system. In a flow driven by rotating the bottom plate of a partially filled, stationary cylindrical container, the shape of the free surface can spontaneously break the axial symmetry and assume the form of a polygon rotating rigidly with a speed different from that of the

Internal waves are waves that propagate along the pycnocline, the interface between two density-stratified fluids. Even though internal waves are ubiquitous in oceans and lakes, their impact in the sedimentary record has remained largely... more

Internal waves are waves that propagate along the pycnocline, the interface between two density-stratified fluids. Even though internal waves are ubiquitous in oceans and lakes, their impact in the sedimentary record has remained largely unrecognized. Internal waves can remobilize the sediment from the depth at which the internal waves break onto the sea floor. In shelf, or ramp settings, internal wave deposits (internalites) have to be distinguished from tempestites while in slope and deeper settings internalites require distinction from turbidites. The Upper Kimmeridgian carbonate ramp succession cropping out near Ricla (NE Spain) provides some key evidence to differentiate the depositional processes induced by breaking internal waves from those related to surface storm waves. Sandy-oolitic grainstone eventites, previously interpreted as tempestites, contain evidence of reworking by turbulent events related to breaking internal waves. Underlying rationale are: 1) they occur in distal mid-ramp position, detached from the coeval shallow-water successions; 2) they do not have the characteristic coarsening- and thickening upward trend of storm deposits; 3) they gradually thin-out to disappear both up dip and down dip, interbedded with mid-ramp lime mudstones; and 4) they show little or no erosion towards the shallower areas. A facies model for internalites produced by two sediment populations, sand and mud, on a gently sloping carbonate ramp is proposed. The individual internalites occurring at Ricla include several architectural elements, sequentially organized in dip direction, which can be related to the flows associated with breaking internal waves: erosion in the breaker zone, swash run-up and tractive backwash flow. Individual internalites stack, with down- and up-slope shingling configuration, in dm-thick packages thought to reflect the up-slope and down-slope migration of the breaker zone, in turn related to depth variations of the palaeo-pycnocline. Packages occur in dm- to m-thick clusters suggested to reflect changes in sediment supply and/or variations in water stratification affecting the energy of internal waves.