Effects of internal waves on carbon chemistry in the euphotic zone in the northern South China Sea.

• Main Authors: Wu, Kuan-Chieh, 吳冠杰
• Other Authors: Chou, Wen-Chen
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/87q447

碩士 === 國立臺灣海洋大學 === 海洋環境與生態研究所 === 107 === In order to understand the impact of internal waves on oceanic CO2 dynamics, the time-series evolutions of hydrological and carbonate chemistry data were investigated at two sites in the northern South China Sea, using mooring sensors and shipboard CTD. One of the study sites is located in the shallow water area near the Dongsha Island (DS station with a water depth of ~100 m), and the other is situated in the deep water area (K2 station with a water depth of ~1000 m). The results showed that the vertical displacements of seawater triggered by internal waves were observed two times within 36 hours at both DS and K2 stations. However, no significant difference in chlorophyll a inventory within the euphotic zone was found between the warm water carried down (WWCD) and cold water brought up (CWBU) periods at the both stations, suggesting that phytoplankton production might not respond to the passage of internal waves during the short term study period (36 hours). Furthermore, partial pressure of CO2 (pCO2) in surface water did not showed significant difference between the WWCD and CWBU periods at the both stations, implying that the vertical motion of seawater was restricted beneath the mixed-layer and with negligible impact for surface pCO2. The comparison between the two stations further revealed that the nutrient-replete subsurface water could be brought into shallower depth at DS station than K2 station during the passage of internal waves, which can subsequently stimulate phytoplankton production. Consequently, the chlorophyll a inventory within the euphotic zone at DS station was significantly higher than that at K2 station. Moreover, the surface pCO2 at the DS station was significantly lower than that at the K2 station by ~20 atm, which could be resulted from the enhanced phytoplankton production and cooling effect induced by the passage of internal waves in the shallow water area. In summary, the present results showed that the passage of internal waves may be favorable for the absorption of atmospheric CO2 in the shallow water area.