The cause of the 2008 cold disaster in the Taiwan Strait

Abstract

The offshore branch of the China Coastal Current in the Taiwan Strait normally makes a U-turn north of the Zhangyun Ridge. In early 2008, the current continued straight and carried water as cold as 14°C toward Penghu Island, causing damage to the local aquaculture and coral reef ecosystem. This study investigates the mechanism behind this intrusion of cold water using available data and a three-dimensional model.The model results show that the 2008 intrusion can be divided into three stages. At the beginning of February, the offshore branch of the China Coastal Current formed a U-shape in the Taiwan Strait; the branch moved cold water from the western strait to the central strait when the offshore geostrophic current, which is related to the southward sea level and density gradients, overcame the onshore Ekman transport caused by the northeasterly monsoon. In the second stage, in mid-February, strong northeasterly winds intensified the southwest current in the Taiwan Strait and resulted in abnormal transport of the cold water from the central strait to Penghu Island. Finally, at the end of February, the warm northeast current was re-established due to weakened wind, and the cold water gradually retreated to the north. The second processes occurred immediately after the first, resulting in the unique intrusion of cold water.