Projects - Water Cycle and Marine Ecosystem

  • PI: Dr. Sei-ichi Saitoh (Hokkaido Univ.)
  • Project title in 2006: Linkages between Freshwater Discharges, Sea-ice Conditions and Primary Productivity and Climate Changes in the Sub Arctic Marginal Seas and Arctic Ocean
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During the summer of 1997, for the first time ever recorded, aquamarine waters, resulting from massive bloom of coccolithophores, covered most of the continental shelf of the eastern Bering Sea. A sequence of unusual phenomena occurred in the coupled atmosphere-ice-ocean system that year, which may have favored rapid growth of the coccolithophores. In 1998, bloom of coccolithophores had also started in spring and continued to summer. Some scientists discuss direct or indirect effects of El Nino events and global warming. This may be an example of the response of Bering Sea ecosystem to climate changes. However, climate change in the Bering Sea is difficult to detect because of large year-to-year variability that can mask a more gradual trend. Although Bering Sea environmental data show some of these rapid shifts, the main characteristic of the last 6 years (2000-2005) is a year-to-year persistence in lack of sea ice, warm bottom temperature, and warm air temperature anomalies in late winter through summer, even though the AO (Arctic Oscillation) and PDO (Pacific Decadal Oscillation) have shown large interannual variability. In 2006, sea ice extended to southern shelf region and shows dramatically change of sea ice extent.

On the other hand, 2004 Alaska forest fire was the largest in these 50 years. A fire, named "Boundary Fire", took place near Fairbanks and burned surface soil severely. It is predicted that there will be influence on water circulation, permafrost degradation, and vegetation recovery in the watershed. We do not understand a linkage between such land surface change and ocean primary production through river discharge including snow and glacier melting. In this program, we will focus on the linkage between freshwater discharge from Yukon River, sea-ice conditions, and primary productivity and climate changes in the sub-arctic marginal seas, including Bering Sea and Okhotsk Sea, and Arctic Ocean. Especially, we will employ satellite remote sensing data and develop new in-water and atmospheric correction algorithms in these Case 2 water regions of high-latitude.

Fig. 1. Map by MODIS and SEM image of coccolith

Figure 1. (a) Monthly coccolith map by MODIS in September, 2005. The coccolith blooming peaked in this month and indicated in red.

(b) Scanning electron microscope image of coccoliths collected in the Bering Sea

 

Fig. 2. Chlorophyll-a concentration

Figure 2. Chlorophyll-a concentration images by SeaWiFS on June 18, 2002.

Increasing aerosol by forest fires has an affect on optical observation by satellite. The adequate atmospheric correction is necessary for the estimation of chlorophyll-a concentration and the amount of phytoplankton.

Left: No absorptive aerosol correction. Right: With absorptive aerosol correction.

 

Research structure

Management Group
Summarizing the results of each group
Hydrological Group
Monitoring seasonal change of turbidity, temperature, and flux in the Yukon River
Snow Cover and Sea Ice Group
Observing snow cover and sea ice, longitudinal measurement of snow temperature and moisture content, and boring ice core
Marine Ecosystem Group
On-site observation in the Arctic Ocean, Bering Sea, and Okhotsk Sea by oceanographic research ships
Satellite Algorithms Group
Collection and processing of satellite data and model construction

Project titles since 2000

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