FY2004 Research Products
Variability of primary productivity in the Bering Sea: Marine ecosystem response to climate change using SeaWiFS, AVHRR and TOPEX/POSIEDON data
- PI: Dr.Sei-ichi Saitoh
- Project title: Variability of Primary Productivity in the Sub-Arctic Seas and Arctic Ocean using ADEOS-II GLI - Response of Marine Ecosystem to Climate Changes
In the Bering Sea, inter-annual and seasonal variability of surface chlorophyll-a concentrations (Chi-a) and primary production are examined using Empirical Orthogonal Function (EOF) analysis of Sea-viewing Wide Fired-of-view Sensor (SeaWiFS) and the Ocean Color Temperature Scanner datasets. From 1997-2003, the large El Nino and the Southern Oscillation (ENSO) phenomena occurred in the Pacific region. The results of EOF analysis on the normalized monthly fields in spring show the east - west seesaw pattern of Chl-a in the spring bloom during April through June. The first EOF mode explains about 31% of temporal and spatial variability, indicating that the outer shelf region off the Kamchatka Peninsula has a different phase during the spring bloom. The second EOF mode shows the costal and offshore wind variability. The third EOF mode describes phase difference in the continental shelf off the Kamchatka Peninsula. This strong east - west signal is linked by the ocean surface wind. The wind anomaly, derived from Special Sensor Microwave Imager (SSMI), shows similar features: the east - west pattern related to the Aleutian low position. The Aleutian low shifted from westward to eastward. Weak wind stress facilitated the development of stratification, resulting in the enhancement of a strong spring bloom off the Kamchatka Peninsula. The position and strength of the Aleutian low correspond to the North Pacific Index. Hence, atmospheric forcing modulation would have a connection with variability of the spring phytoplankton biomass in the Bering Sea through a teleconnection of an ENSO event. The positive relationship between chlorophyll EOF1 and EOF2 with coefficient of 0.51 was obtained.
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| Figure 1. Relationship between chlorophyll-a EOF mode1 and PAR EOF mode 2 (copyright, S. Saitoh) (a) Temporal change of both modes (Correlation R=0.51) (b) Spatial pattern of chlorophyll-a EOF mode 1 (c) Spatial pattern of PAR EOF mode 2 |
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