Detection of cyclone-induced rapid increases in chlorophyll-a with sea surface cooling in the northwestern Pacific Ocean from a MODIS/SeaWiFS merged satellite chlorophyll product

Abstract

We performed a comprehensive analysis of satellite chlorophyll-a concentration (chl-a) data to detect all events in which chl-a rapidly increased on a time scale of 10 days or less. Our analysis could successfully detect cases in which chl-a increased and sea surface temperature (SST) decreased rapidly after the passages of tropical and extratropical cyclones. The events with large SST decreases tended to occur south of Japan, in the Sea of Okhotsk, and in the regions between 35° and 45° N, especially the Kuroshio–Oyashio Extension (KOE) region. Although the contribution of cyclones on the yearly total chl-a increase was basically small, the cyclone-induced chl-a increases accounted for a few tens of per cent of the total chl-a increase in some areas. In oligotrophic regions, the increases in chl-a tended to become larger as the corresponding SST decrease became larger, although the relationship between them is opposite in mesotrophic and eutrophic regions.

Acknowledgements

This work was supported by the Japan Society for the Promotion of Science (JSPS), Grant-in-Aid for Scientific Research (C) (19612005). Microwave OI SST, SSM/I and AMSR-E data were produced by RSS and sponsored by the National Oceanographic Partnership Program (NOPP), the NASA Earth Science Physical Oceanography Program, the NASA MEaSUREs (Making Earth Science data records for Use in Research Environments) DISCOVER (Distributed Information Services for Climate and Ocean products and Visualizations for Earth Research) Project and the AMSR-E Science Team. Data are available at www.remss.com. The merged chl-a concentration data are produced and released by NASA/GSFC. The TC best track data and weather charts were provided by the Japan Meteorological Agency. The authors are extremely grateful to J. Ishizaka of Nagoya University, H. Kawamura of Tohoku University, K. Sasaoka, S. Hosoda, S. Kouketsu and K. Satoh of Japan Agency for Marine–Earth Science and Technology (JAMSTEC) for providing useful information. The authors also really appreciate valuable comments from reviewers.