Abyssal Circulation Driven by a Periodic Impulsive Source in a SmallBasin with Steep Bottom Slope with Implications to the East Sea
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In the theory of source-driven abyssal circulation, the forcing is usually assumed to be steadysource (deep-water formation). In many cases, however, the deep-water formation occurs instantaneouslyand it is not clear whether the theory can be applied well in this case. An attempt is made to resolve thisproblem by using a simple reduced gravity model. The model basin has large depth change compared forits size, like the East Sea, such that isobaths nearly coincide with geostrophic contours. Deep-water isformed every year impulsively and flows into the model basin through the boundary. It is found that thecirculation driven by the impulsive source is generally the same as that driven by a steady source exceptthat the former has a seasonal fluctuation associated with unsteadiness of forcing. The magnitudes of boththe annual average and seasonal fluctuations increase with the rate of deep-water formation. The problemcan be approximated to that of linear diffusion of momentum with boundary flux, which well demonstratesthe essential feature of abyssal circulation spun-up by periodic impulsive source. Although the modelgreatly idealizes the real situation, it suggests that abyssal circulation can be driven by a periodic impulsivesource in the East Sea.
Abstract
In the theory of source-driven abyssal circulation, the forcing is usually assumed to be steadysource (deep-water formation). In many cases, however, the deep-water formation occurs instantaneouslyand it is not clear whether the theory can be applied well in this case. An attempt is made to resolve thisproblem by using a simple reduced gravity model. The model basin has large depth change compared forits size, like the East Sea, such that isobaths nearly coincide with geostrophic contours. Deep-water isformed every year impulsively and flows into the model basin through the boundary. It is found that thecirculation driven by the impulsive source is generally the same as that driven by a steady source exceptthat the former has a seasonal fluctuation associated with unsteadiness of forcing. The magnitudes of boththe annual average and seasonal fluctuations increase with the rate of deep-water formation. The problemcan be approximated to that of linear diffusion of momentum with boundary flux, which well demonstratesthe essential feature of abyssal circulation spun-up by periodic impulsive source. Although the modelgreatly idealizes the real situation, it suggests that abyssal circulation can be driven by a periodic impulsivesource in the East Sea.
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