Remote impacts of low-latitude oceanic climate on coastal upwelling in a marginal sea of the Northwestern Pacific

Abstract

Upwelling plays an important role in the physical processes and biological variability of coastal regions. Using 40-year-long hydrographic and climate data, the remote impacts of low-latitude oceanic climate on the upwelling along the east coast of Korea were investigated. During El Niño, the development of anomalously enhanced anti-cyclonic circulation over Northwestern Pacific resulted in relatively strong (∼1.1 m s−1) southerly winds, compared to La Niña. During El Niño, the mean upwelling index was 402 ± 106 kg m−1 s−1, and 10 °C isotherm was located at a depth of 32.7 m. During La Niña, they were 368 ± 95 kg m−1 s−1 and 39.9 m, respectively. During El Niño, in the approximation, the offshore Ekman transport by wind-induced upwelling and the vertical transport by isotherm were higher than those during La Niña. This finding can be explained by the increased sea surface height gradient, the subsequent enhanced geostrophic current, the decrease in onshore sea surface temperature, and the increase in chl-a concentration during El Niño. The intensity of upwelling tended to be stronger (weaker) during periods when El Niño (La Niña) and the PDO (Pacific Decadal Oscillation) were in phase than those when they were out of phase. These results suggest that low-latitude climate change could affect the coastal upwelling in the mid-latitude marginal sea through the teleconnection.