Browsing by Author "Escauriaza, Cristian"

Now showing 1 - 5 of 5
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    A snapshot of turbulence in the Northeastern Magellan Strait
    (2024) Lozovatsky, Iossif; Escauriaza, Cristian; Suarez, Leandro; Fernando, Harindra J. S.; Williams, Megan; Coppersmith, Ronald Scott; Mayorga, Nicolas
    First-ever measurements of the turbulent kinetic energy (TKE) dissipation rate in the northeastern Strait of Magellan (Seg-unda Angostura region) taken in March 2019 are reported here. At the time of microstructure measurements, the magnitude of the reversing tidal current ranged between 0.8 and 1.2 ms(-1). The probability distribution of the TKE dissipation rate in the water interior above the bottom boundary layer was lognormal with a high median value epsilon(MS)(med) = 1.2x10(-6) Wkg(-1). Strong vertical shear, (1-2)x10(-2) s(-1), in the weakly stratified water interior ensued a sub-critical gradient Richardson number Ri < 10(-1) - 10(-2). In the bottom boundary layer (BBL), the vertical shear and the TKE dissipation rate both decreased exponentially with the distance from the seafloor xi, leading to a turbulent regime with an eddy viscosity K-M similar to 10(-3) m(2)/s, which varied with time and location, while being independent of the vertical coordinate in the upper part of BBL (for xi > similar to 2 meters above the bottom).
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    Anthropogenic effects on flood hazards in a hyper-arid watershed: The 2015 Atacama floods
    (2024) Contreras, Maria Teresa; Nash, Sebastian; Escauriaza, Cristian
    An unprecedented precipitation event in the hyper-arid Atacama Desert of Northern Chile occurred in March 2015. Geomorphic alterations to the river channel and the coastal zone, coupled with the exceptional magnitude of the rainfall, caused catastrophic damage and loss of life. On the coast of the El Salado watershed, legacy mine tailings infilled the watershed-ocean connection, while the river channel was altered both by tailings and urbanization. The consequences of this event resulted from the coupling of anthropogenic geomorphic changes with an unusual climate event. Lack of field data, complex geomorphology and sediment loads influenced by human activity make analysing floods in these regions especially challenging. The objective of this work is to improve our understanding of the factors that control flood hazards by using numerical simulations to reconstruct the 2015 flood in El Salado. We carry out unsteady two-dimensional simulations fully coupled with the sediment concentration to identify the influence of tailing deposits, considering high-resolution data of the pre- and post-2015 flood topography. The results highlight the importance of specific event-based studies, using models that can help designing better strategies for climate change adaptation and risk mitigation, while providing information for risk reduction and channel restoration.
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    Flow characterization and turbulence in the eastern section of the Strait of Magellan, Southern Chile
    (2024) Suarez, Leandro; Guerra, Maricarmen; Williams, Megan E.; Escauriaza, Cristian; Lozovatsky, Iossif; Coppersmith, Ronald; Fernando, Harindra Joseph S.
    The Strait of Magellan connects the Pacific and Atlantic oceans in South America's southern region, and it has been recognized for centuries as an important transoceanic navigation route as well as a unique marine environment with a rich ecological diversity. Evaluations of the impact of human activities in the channel and multiple potential future developments require abetter understanding of the physical environment to design sustainable strategies aimed at preserving these characteristics. In this investigation, we study the flow near the Atlantic inlet of the Strait where the dynamics is characterized by the interactions of the tide propagation within two narrows, which are the predominant features of the channel morphology. Tides amplified by the Patagonian shelf generate strong currents through these narrows and control the exchange between the Atlantic and central regions of the Strait. We employ bottom-mounted and vessel-mounted Acoustic Doppler Current Profilers (ADCPs) with tide gauges to analyze the mean flow, tidal propagation, and turbulence, complementing the data with previous available measurements. The analysis reveals residual flows directed toward ebb flow at the channel center and flood near the edges, showing a significant spring-neap variation. Turbulence statistics in the second narrows exhibit a significant variability between ebb and flood, with a balance between production and dissipation observed only during ebb phases.
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    Lagrangian drifter modelling of an experimental RIP current
    (2012) Suarez, Leandro; Cienfuegos, Rodrigo; Escauriaza, Cristian; Barthélemy, Eric; Michallet, Hervé
    A non-uniform alongshore wave forcing on an experimental uneven mobile bathymetry create mean circulation on a rip channel. A 2D numerical hydrodynamic model that integrates the non-linear shallow-water equations in a shock-capturing finite-volume framework is used to validate the nearshore circulation, and drifters displacement.
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    Understanding Salinity Intrusion and Residence Times in a Small-Scale Bar-Built Estuary under Drought Scenarios: The Maipo River Estuary, Central Chile
    (2024) Soto-Rivas, Karina; Flores, Raul P.; Williams, Megan; Escauriaza, Cristian
    The Maipo River estuary is a low-inflow bar-built estuary that includes a protected wetland, which harbors a rich ecosystem. The estuary and wetland have been threatened by a persistent drought for more than a decade, which has resulted in greater salinity intrusion and increased residence times. Previous studies have described salinity and pollutants in estuaries; however, almost all have focused on deeper and/or wider estuaries with dimensions much larger than those of the small-scale Maipo River estuary. In this study, we used the numerical model FVCOM to simulate the dynamics of the Maipo River estuary under drought scenarios and explored the interactions between river discharge and tides in terms of saline intrusion and particle dispersal. The model was validated against observations collected during a field campaign near the river mouth. The simulations successfully reproduced the water surface elevation but underestimated salinity values, such that the vertical salinity structure observed in the field was not captured by the model in this shallow and morphologically complex estuary. Consequently, our model results provide qualitative insight related to salinity and baroclinic dynamics. Results of maximum saline intrusion showed an exponential decay with increasing river discharge, and the analysis of salinity intrusion time series revealed that droughts may cause permanent non-zero salinity levels in the estuary, potentially affecting ecological cycles. The incorporation of passive tracers showed that decreasing river discharge increases the residence time of particles by allowing the tracers to re-enter the estuary. Model results showed the formation of accumulation zones (hotspots) in the shallower zones of the estuary.