In order to determine the relative aging status of upwelled or vertically mixed water in the northern Taiwan Strait, a recently developed method of calculating the degree of nutrient consumption (DNC) was employed. Up...In order to determine the relative aging status of upwelled or vertically mixed water in the northern Taiwan Strait, a recently developed method of calculating the degree of nutrient consumption (DNC) was employed. Upwelling was detected at a water depth of about 75 m in summer. Bottom waters in the aphotic zone and newly-upwelled waters in the euphoric zone were found to be low in terms of their DNC. In general, a low DNC was noted alongside the other traditional upwelling indicators, such as lower temperature and degree of oxygen saturation, but higher salinity, apparent oxygen utilization, nutrient contents and chlorophyll-a. Enhanced vertical mixing, but without an apparent upwelling signal, was detected near the same location in winter.展开更多
Distinctive white laminations appear in the generally black sediments of the anoxic, subalpine Great Ghost Lake in southern Taiwan. These white laminations have lower porosity, organic matter content and C/N ratio, bu...Distinctive white laminations appear in the generally black sediments of the anoxic, subalpine Great Ghost Lake in southern Taiwan. These white laminations have lower porosity, organic matter content and C/N ratio, but higher C/S, N/S ratios and magnetic susceptibility, and contain organic matter most probably derived from phytoplankton. This and the collision marks on the quartz particles suggest that they have an aeolian component and have been deposited in cooler and drier periods. The organic matter of the black sediments is mainly from land plants and the quartz particles bear no collision marks, suggesting local deposition under warmer and wetter climates. These high resolution data, the first not only in Taiwan but also for Southeast Asia, are in good agreement with the local climatological records deduced from documentary sources since 1681 and direct instrumental rainfall measurements at stations nearby since 1900. Rainfall over the past 2600 years has been reconstructed. Major droughts appear in 240 BC, 80 BC, 90 AD, 420-520 AD, 620-700 AD, 850-930 AD, 1350-1430 AD, 1570 AD, 1730-1800 AD and 1960 AD, and correspond to not only the periods of cold/dry and frequent dust storms but also major population declines based on the historical and natural records of China. These seem to reflect large scale climatic changes.展开更多
文摘In order to determine the relative aging status of upwelled or vertically mixed water in the northern Taiwan Strait, a recently developed method of calculating the degree of nutrient consumption (DNC) was employed. Upwelling was detected at a water depth of about 75 m in summer. Bottom waters in the aphotic zone and newly-upwelled waters in the euphoric zone were found to be low in terms of their DNC. In general, a low DNC was noted alongside the other traditional upwelling indicators, such as lower temperature and degree of oxygen saturation, but higher salinity, apparent oxygen utilization, nutrient contents and chlorophyll-a. Enhanced vertical mixing, but without an apparent upwelling signal, was detected near the same location in winter.
文摘Distinctive white laminations appear in the generally black sediments of the anoxic, subalpine Great Ghost Lake in southern Taiwan. These white laminations have lower porosity, organic matter content and C/N ratio, but higher C/S, N/S ratios and magnetic susceptibility, and contain organic matter most probably derived from phytoplankton. This and the collision marks on the quartz particles suggest that they have an aeolian component and have been deposited in cooler and drier periods. The organic matter of the black sediments is mainly from land plants and the quartz particles bear no collision marks, suggesting local deposition under warmer and wetter climates. These high resolution data, the first not only in Taiwan but also for Southeast Asia, are in good agreement with the local climatological records deduced from documentary sources since 1681 and direct instrumental rainfall measurements at stations nearby since 1900. Rainfall over the past 2600 years has been reconstructed. Major droughts appear in 240 BC, 80 BC, 90 AD, 420-520 AD, 620-700 AD, 850-930 AD, 1350-1430 AD, 1570 AD, 1730-1800 AD and 1960 AD, and correspond to not only the periods of cold/dry and frequent dust storms but also major population declines based on the historical and natural records of China. These seem to reflect large scale climatic changes.
