Typhoon footprints on ocean surface temperature and chlorophyll-a in the South China Sea

Abstract

Typhoons pose great threats to coastal regions, leaving distinctive ocean surface changes along the typhoon track before landing. However, a quantitative description of the spatial and temporal patterns of typhoon-induced oceanic responses remains unclear. Sixteen years of composited data of sea surface temperature (SST) and sea surface chlorophyll-a (Chl-a) in the South China Sea demonstrate that typhoon-induced changes initiate immediately before the arrival of the typhoon and continue to increase during its passage. The largest decrease in temperature occurred one day after the typhoon, leading the maximum Chl-a increase by four days. The spatial distribution of changes in SST and Chl-a clearly shows the prominent enhancement to the right of the typhoon's path. Both typhoon features and ocean status determine the corresponding impact on the oceans, as large temperature responses are associated with strong wind, slow translation speed and shallow mixed layer depth (MLD). The Chl-a responses generally followed the same rule, but the maximum Chl-a increase was found with a moderate value of the MLD that was most favorable to induce phytoplankton blooms. Quantifying the typhoon footprints will help to predict how the ocean responds to extreme events in the future climate.

Keywords: Chlorophyll-a increases; Mixing; Ocean surface; South China Sea; Temperature decreases; Typhoon.