Respuesta del golfo de Arauco al paso de ciclones extratropicales durante el periodo invernal.
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Date
2023
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Publisher
Universidad de Concepción
Abstract
El Golfo de Arauco (GA), situado en las costas de la región del Biobío, es el cuerpo de agua semicerrado más grande de Chile central. Esta región ha sido ampliamente estudiada durante los meses estivales, época en que las condiciones atmosféricas favorecen una intensa surgencia. En contraste, durante el invierno, caracterizado por un aumento en el paso de sistemas de baja presión atmosférica, conocidos como ciclones extratropicales, los estudios son más limitados. Esto ha resultado en un conocimiento insuficiente sobre las dinámicas invernales del GA, especialmente bajo la influencia de estos fenómenos atmosféricos. Esta investigación aborda esta brecha, concentrándose en cómo el GA responde a la presencia de estos ciclones extratropicales y a los cambios asociados en los patrones de viento, con el fin de entender mejor las dinámicas invernales en esta región. Para llevar a cabo este estudio, se caracterizó el paso de ciclones extratropicales a partir de campos de presión atmosférica (1979-2020) y su efecto sobre el viento meridional en la región. Utilizando estos resultados, se evaluó la respuesta de las corrientes en las conexiones del Golfo de Arauco con el océano, mediante observaciones de ADCP en la boca Chica (BC) y en la región occidental de la boca Grande (Punta Delicada; PD), en los inviernos de junio-septiembre 2016 y mayo-julio 2018. Adicionalmente se compararon los principales modos de variabilidad de las corrientes con el viento local a través de estudios de correlación y ondeletas de coherencia, revelando una influencia directa de los ciclones en la generación y modulación de las corrientes del GA. Estos resultados sugieren que la respuesta hidrodinámica del GA al paso de ciclones extratropicales se debe principalmente a la influencia del viento norte asociado a estos sistemas. Estos vientos, al superar cierta intensidad, provocan un transporte superficial de agua en PD hacia el interior del GA. Esto crea un gradiente de presión que dirige un flujo de salida por BC y a través de las capas subsuperficiales de PD. A medida que la fuerza del viento norte disminuye, el flujo superficial en PD se atenúa, lo que permite que el agua salga a profundidades menores. Este mecanismo sugiere un rol importante de los ciclones en la renovación de las aguas del GA, reduciendo potencialmente los tiempos de residencia del agua en el golfo. Por lo que estos hallazgos no solo aportan al entendimiento de la dinámica invernal del GA, sino que también pueden tener implicaciones significativas para la gestión ambiental y marina en la región.
The Gulf of Arauco (GA), located along the coast of the Biobío region, is the largest semi-enclosed body of water in central Chile. This region has been extensively studied during the summer months when atmospheric conditions favor intense upwelling. In contrast, during winter, characterized by an increase in the passage of low atmospheric pressure systems, known as extratropical cyclones, studies are more limited. This has led to an insufficient knowledge of the GA’s winter dynamics, especially under the influence of these atmospheric phenomena. This research addresses this gap, focusing on how the GA responds to the presence of these extratropical cyclones and the associated changes in wind patterns, in order to better understand the winter dynamics in this region. To conduct this study, the passage of extratropical cyclones was characterized using atmospheric pressure fields (1979-2020) and their effect on the meridional wind in the region. Using these results, the response of the currents in the connections of the Arauco Gulf with the ocean was evaluated, through ADCP observations at Boca Chica (BC) and in the western region of Boca Grande (Punta Delicada; PD), during the winter periods of June-September 2016 and May-July 2018. Additionally, the main modes of current variability were compared with the local wind through correlation studies and coherence wavelets, revealing a direct influence of cyclones on the generation and modulation of the GA’s currents. These results suggest that the GA’s hydrodynamic response to the passage of extratropical cyclones is mainly due to the influence of the northerly winds. These winds can cause a surface transport of water in PD towards the interior of the GA. This creates a pressure gradient that directs an outflow through BC and through the subsurface layers of PD. As the north wind decreases, the surface flow in PD attenuates, allowing the water to exit at shallower depths. This mechanism suggests an important role of cyclones in the renewal of the waters of the GA, potentially reducing the residence times of water in the gulf. Therefore, these findings not only contribute to the understanding of the GA’s winter dynamics but also may have significant implications for environmental and marine management in the region.
The Gulf of Arauco (GA), located along the coast of the Biobío region, is the largest semi-enclosed body of water in central Chile. This region has been extensively studied during the summer months when atmospheric conditions favor intense upwelling. In contrast, during winter, characterized by an increase in the passage of low atmospheric pressure systems, known as extratropical cyclones, studies are more limited. This has led to an insufficient knowledge of the GA’s winter dynamics, especially under the influence of these atmospheric phenomena. This research addresses this gap, focusing on how the GA responds to the presence of these extratropical cyclones and the associated changes in wind patterns, in order to better understand the winter dynamics in this region. To conduct this study, the passage of extratropical cyclones was characterized using atmospheric pressure fields (1979-2020) and their effect on the meridional wind in the region. Using these results, the response of the currents in the connections of the Arauco Gulf with the ocean was evaluated, through ADCP observations at Boca Chica (BC) and in the western region of Boca Grande (Punta Delicada; PD), during the winter periods of June-September 2016 and May-July 2018. Additionally, the main modes of current variability were compared with the local wind through correlation studies and coherence wavelets, revealing a direct influence of cyclones on the generation and modulation of the GA’s currents. These results suggest that the GA’s hydrodynamic response to the passage of extratropical cyclones is mainly due to the influence of the northerly winds. These winds can cause a surface transport of water in PD towards the interior of the GA. This creates a pressure gradient that directs an outflow through BC and through the subsurface layers of PD. As the north wind decreases, the surface flow in PD attenuates, allowing the water to exit at shallower depths. This mechanism suggests an important role of cyclones in the renewal of the waters of the GA, potentially reducing the residence times of water in the gulf. Therefore, these findings not only contribute to the understanding of the GA’s winter dynamics but also may have significant implications for environmental and marine management in the region.
Description
Tesis presentada para optar al grado de Magíster en Ciencias con mención en Oceanografía.