Two phytoplankton blooms near Luzon Strait generated by lingering Typhoon Parma

Two phytoplankton blooms near Luzon Strait triggered by Typhoon Parma in 2009 were investigated using remote sensing data and in situ observations. Parma was slow moving (a translation speed of similar to 2ms(-1)) and relatively weak (a maximum sustained wind of similar to 30ms(-1)) during its lingering path northwest of Luzon Island. After it reached a point (120.5 degrees E, 20.3 degrees N) west of Luzon Strait, Parma turned sharply back toward the northern Philippines along approximately the same course. Such long (similar to 7days) lingering typhoons are rather rare in the South China Sea (SCS). Before Parma, low Chl-a concentrations (<0.2mgm(-3)) were observed in the northeastern SCS. After its passage, a strong offshore phytoplankton increase (Chl-a>0.6mgm(-3)) appeared west of the central Luzon Strait; a nearshore phytoplankton increase was also observed north of Luzon Island, together with high CDOM (color dissolved organic matter). During and after the typhoon, sea-surface cooling (similar to 3 degrees C), stronger wind (>20ms(-1)), and heavy rainfall (>100mmday(-1)) were seen in the above regions. The offshore bloom occurred where Parma's translation speed was the slowest (similar to 1ms(-1)). It may be caused primarily by the Ekman pumping which brought nutrients upward to the euphotic zone and also by the entrainment mixing. The nearshore bloom may be triggered by the heavy typhoon-induced rainfall, which supplied nutrients for the coast region north of Luzon Island. The rapid increase of CDOM in the nearshore region implied that terrestrial input may be the source of nutrients.The present research was supported by the National Natural Science Foundation of China (Grant number: 41006070, 41176011, and U0933001) and the Canadian Space Agency Government Related Initiative Program (GRIP). We thank NASA's Ocean Color Working Group for providing Modis and SeaWiFS data, Remote Sensing Systems for TMI-AMSRE sea-surface temperature and QuikSCAT wind-vector data, the Physical Oceanography Distributed Active Archive Center (PO.DAAC) for QuikScat wind stress, GES DAAC for TRMM accumulated rainfall data, and the Colorado Center for Astrodynamics Research (CCAR) Altimeter Data Research Group for sea-level anomaly data