Hidrodinámica invernal de la bahía de Concepción.
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Date
2025
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Publisher
Universidad de Concepción
Abstract
Este estudio caracteriza la hidrodinámica invernal de la bahía de Concepción (BC), Chile, durante el invierno austral de 2023 (junio-agosto). A partir de datos de CTD y ADCPs, se analizó la temperatura, salinidad, densidad, turbidez, oxígeno disuelto, fluorescencia, y las corrientes marinas con el objetivo de comprender la hidrografía invernal y los patrones de circulación y su variabilidad. Los análisis incluyeron dispersión de las corrientes, diagramas de vector progresivo y descomposición ortogonal para evaluar el flujo medio y su variabilidad por cada anclaje. Además, se aplicaron funciones ortogonales empíricas (EOF) a las corrientes horarias originales de cada anclaje por separado (estructura vertical) y también combinando los tres anclajes (EOF total). Los resultados revelaron una estructura de dos capas en las corrientes del sector Tomé (cercano a la boca Grande) con flujos superficiales predominantes hacia la cabecera de BC y un flujo compensatorio hacia el océano en el fondo, durante eventos de vientos desde el norte. Se identificó una correlación de Pearson (r) de 0,8 (p < 0,001), y una correlación cruzada máxima de un valor de 0,8, con un desfase de +2 horas entre la componente meridional del viento y la serie de tiempo del modo empírico 1 vertical en Tomé. Los primeros tres modos del modo empírico 1 de los tres anclajes combinados, explicaron el 64.4% de la variabilidad total de las corrientes en BC (modo 1: 39.8%, modo 2: 16.9%, modo 3: 7.6%). Por otra parte, la hidrografía evidenció una alta sensibilidad a las tormentas invernales en términos de influencia del viento, lluvia y aportes de agua dulce continental. Mientras que las fluctuaciones del viento invernal explicaron entre el 37 y 49% de la variabilidad de la corriente total, el agua dulce logró diluir la capa superficial de la BC en hasta un 80%, con respecto a una salinidad de referencia de 34. El estudio permite proponer que las tormentas de viento norte y el aumento de los caudales invernales provoca un apilamiento de agua diluida hacia la cabecera de BC, donde el nivel del mar aumenta generando un gradiente de presión meridional que tiende a evacuar el exceso de agua acumulada por el nivel del fondo, provocando una doble capa de circulación en la boca Grande de BC. Estos eventos son, por lo tanto, eficientes mecanismos de renovación de aguas en BC. Esta investigación representa el primer estudio que utiliza ADCPs anclados dentro de la bahía, entregando información actual para fortalecer el entendimiento de los procesos físicos que caracterizan la BC y orientar estrategias de su gestión ambiental.
This study characterizes the winter hydrodynamics of Concepción Bay (BC), Chile, during the austral winter of 2023 (June-August). From data sampled by CTD and ADCPs, physicochemical variables such as temperature, salinity, density, turbidity, dissolved oxygen, and fluorescence were analyzed, along with current measurements, to understand circulation patterns and their variability. The analyses included progressive vector diagrams to assess residual transport and mean flow for each anchorage. In addition, empirical orthogonal functions (EOF) were applied for the raw hourly currents of each anchor separately (vertical structure) and by combining the three anchors (total EOF). The results revealed a two-layer structure in the currents of the Tomé sector (near the Boca Grande) with predominant surface flows towards the head of BC and a compensatory flow towards the ocean at the bottom during wind events from the north. A Pearson correlation (r) of 0.8 (p < 0.001) was identified, and a maximum cross-correlation of a value of 0.8, with a lag of +2 hours between the southern component of the wind and the time series of the empirical mode 1 vertical in Tomé. The first three modes of empirical mode 1, when combined with the three anchors, explained 64.4% of the total variability of the currents in BC (mode 1: 39.8%, mode 2: 16.9%, mode 3: 7.6%). On the other hand, the fluctuations in hydrographic properties indicated the high sensitivity of the system to winter storms, both in terms of wind influence and rainfall, which diluted the surface layer of the BC by up to 80%. This analysis provides a comprehensive perspective to understand the physical mechanisms that control the circulation of this bay, highlighting the influence of winds on currents and surface layer dilution. These findings lay the foundation for the first study to utilize bay-anchored ADCPs, providing current information to enhance the understanding of the physical processes that characterize this region and inform environmental management strategies.
This study characterizes the winter hydrodynamics of Concepción Bay (BC), Chile, during the austral winter of 2023 (June-August). From data sampled by CTD and ADCPs, physicochemical variables such as temperature, salinity, density, turbidity, dissolved oxygen, and fluorescence were analyzed, along with current measurements, to understand circulation patterns and their variability. The analyses included progressive vector diagrams to assess residual transport and mean flow for each anchorage. In addition, empirical orthogonal functions (EOF) were applied for the raw hourly currents of each anchor separately (vertical structure) and by combining the three anchors (total EOF). The results revealed a two-layer structure in the currents of the Tomé sector (near the Boca Grande) with predominant surface flows towards the head of BC and a compensatory flow towards the ocean at the bottom during wind events from the north. A Pearson correlation (r) of 0.8 (p < 0.001) was identified, and a maximum cross-correlation of a value of 0.8, with a lag of +2 hours between the southern component of the wind and the time series of the empirical mode 1 vertical in Tomé. The first three modes of empirical mode 1, when combined with the three anchors, explained 64.4% of the total variability of the currents in BC (mode 1: 39.8%, mode 2: 16.9%, mode 3: 7.6%). On the other hand, the fluctuations in hydrographic properties indicated the high sensitivity of the system to winter storms, both in terms of wind influence and rainfall, which diluted the surface layer of the BC by up to 80%. This analysis provides a comprehensive perspective to understand the physical mechanisms that control the circulation of this bay, highlighting the influence of winds on currents and surface layer dilution. These findings lay the foundation for the first study to utilize bay-anchored ADCPs, providing current information to enhance the understanding of the physical processes that characterize this region and inform environmental management strategies.
Description
Tesis presentada para optar al título de Biólogo/a Marino/a.
Keywords
Hidrodinámica, Bahías, Invierno