Intense phytoplankton bloom induced by typhoon in coastal water
Abstract
Typhoon landfall is devastating to the economy and may cause human lives. Yet typhoon may also enhance other forms of life - the primary productivity of coastal water. Large human population lives near the coast and understands the threat of strong wind and heavy rain of marine storms. Coastal water and marginal seas are the most productive part of global oceans, but few people realize that typhoons may pump nutrients to the surface water and benefit fishery after their passages. . The typhoon forcing and oceanic responses over coastal water have strong temporal and spatial variability that cannot be sufficiently resolved by operational numerical weather prediction models and ground measurements. Two spaceborne microwave sensors, QuikSCAT and the Tropical Rain Measuring Mission Microwave Imager (TMI) allow us to measure ocean surface wind vectors and sea surface temperature (SST) under the cloud cover of typhoons day and night, and the Sea Viewing Wide-Field-of-View Sensor (SeaWifs) shows us the ocean color, and the biological activities it denotes, after the typhoon passage. An interdisciplinary study of physical forcing and biological response based on synergistic applications of the three space missions will be presented. Three typhoons were tracked, through the QuikSCAT surface wind field and Ekman pumping, over the coastal water and marginal seas of East Asia in the summer of 2000. Super-typhoon Bilis left a cold wake in the deep water east of Taiwan as observed by TMI, but with no increase in biological activities near the surface as observed by SeaWifs. A weaker typhoon Prapirron followed Bilis a week later producing a cold wake at the north east tip of Taiwan. SeaWifs observed increase in biological activities in this wake after Prapirron passage. Climatological in situ measurements show that in the ocean east of Taiwan, the nutrients lie deep. They do not rise to the surface even with the passage of super-typhoon. However, in the coastal shallow water, nutrients are near the surface and they rise to the surface even with the passage of a weak typhoon. Typhoon Kai-Tak passed slowly through the northern part of South China Sea, which is a semi-enclosed marginal sea. TMI and SeaWifs show a 10 C cooling of SST and 100 time increases (from 0.1 to 10 mg/m3 ) chlorophyll-a (indicating biological activities), confirming that the biological response to Ekman pumping by typhoons can be much stronger than generally believed in coastal water and marginal seas where nutrients reside in shallow water.
- Publication:
-
34th COSPAR Scientific Assembly
- Pub Date:
- 2002
- Bibcode:
- 2002cosp...34E1447L