ITCZ의 계절변동으로 기원된 입자플럭스의 계절변화

Abstract

To evaluate the effect of physical processes on surface ocean productivity, a time-series sediment trap study was carried out from July 2003 to June 2005 at a station (10.5°N, 131°W) in the 10°N thermocline ridge area. The monitoring period can be divided into two intervals based on the Ocean Niño Index (ONI; sea surface temperature anomaly in the ‘NINO 3.4’ region); weak El Niño period from June 2004 to February 2005 with SST anomalies greater than 0.5℃ and normal condition period with SST anomalies between -0.5℃ and 0.5℃. The normal condition period can be further divided into three seasons based on the particle fluxes; period 1 (July-August; intermediate particle fluxes), period 2 (December-May; high particle fluxes), and period 3 (the other periods; low particle fluxes).Particle fluxes during the period 2 were mostly 2 times greater than those of period 3. These high particle fluxes are attributed to strong northeast trade wind that develops in the site by southward shifting of the Inter-tropical Convergence Zone (ITCZ). It resulted in deepening of wind-driven mixed layer, which induced more effective supply of nutrient-enriched sub-surface water to the surface ocean. Also, particle fluxes during the period 1 were 26-80% higher than those of period 3. The increased particle fluxes during the period 1 are likely due to regional upwelling because the study site locates at the boundary between North Equatorial Counter Current and North Equatorial Current during this period. The particle fluxes observed at regional upwelling season, period 1, were much less than high wind season of period 2. It might be attributed to heavy precipitation for period 1 when the study site lies under the ITCZ. Heavy precipitation forms a low density surface layer that suppresses the supply of nutrient-enriched sub-surface water to the surface ocean. Thus, the productivity of the surface ocean in the 10°N thermocline ridge area is affected by regional upwelling a