Publication Date:
2019
Description:
Abstract
The summer South Vietnam Upwelling (SVU) is a major component of the South China Sea circulation where it also influences ecosystems. Here we revisit the existing knowledge of the SVU interannual variability. Based on a set of 15‐year eddy‐resolving sensitivity simulations, we quantify the respective contributions from different factors (atmospheric, river and oceanic forcings, ocean intrinsic variability OIV, El‐Niño Southern Oscillation ENSO) to this interannual variability and explore the underlying mechanisms. Our sea surface temperature upwelling indices allow us to quantify the strong SVU interannual variability in terms of strength and spatial distribution. Strong SVU years are offshore‐dominant with SVU centers located within 11‐12oN and 110‐112oE whereas weak SVU years are coastal‐dominant with SVU centers located near the coast and spanning a larger 10‐14oN latitude range. Our study confirms the leading influence of the summer wind, and further reveals that coastal SVU variability is related to the variability of the eastward jet that develops from the coast, whereas offshore SVU variability is strongly driven by the spatio‐temporal collocation of wind stress curl with cyclonic eddies. OIV, and to a lesser extent perturbations induced by river discharge and lateral oceanic conditions, strongly triggers interannual variability of background eddy circulation, thus of the SVU. ENSO influences the SVU mainly through its direct influence on summer winds.
Print ISSN:
2169-9275
Electronic ISSN:
2169-9291
Topics:
Geosciences
,
Physics
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