- 期刊
太平洋十年振盪對呂宋島北部海域葉綠素a濃度之影響
Impacts of Pacific Decadal Oscillation on Chlorophyll-a Concentration in the Water of North of Luzon Island
摘要
本文利用MODIS（Moderate-resolution Imaging Spectroradiometer）－Aqua葉綠素a濃度數據，發現呂宋島北部沿海的海面葉綠素a濃度顯著高於周圍地區。在卡加延河口，太平洋十年振盪（PDO）冷相位的葉綠素a濃度比暖相位多出0.14 mg/m^3。PDO為負值時，地轉流場顯示黑潮在呂宋島東北端以北流速減弱，而以南則增強。PDO在此時與TRMM（Tropical Rainfall Measuring Mission）衛星的累積降雨量數據呈顯著負相關。降雨型態、流場及海底地形為呂宋島北部提供營養物質使得卡加延河口的葉綠素a濃度顯著上升。在PDO負相位時，地轉流場阻礙貧營養的黑潮水進入南海，困住該海域的葉綠素a。此研究揭示了氣候變化下降雨與洋流在調節葉綠素a濃度中的複雜關係。
並列摘要
This study analyzes monthly Moderate-resolution Imaging Spectroradiometer (MODIS)-Aqua sea surface chlorophyll-a (SChl-a) data and finds significantly high SChl-a concentrations along the northern coast of Luzon Island compared to its surrounding areas. In the Cagayan River estuary near the Luzon Strait, the average SChl-a concentration in the cold phase of the Pacific Decadal Oscillation (PDO) is up to 0.14 mg/m3 higher than that in the warm phase. In months with negative PDO index (cold phase), geostrophic current composites show the oligotrophic Kuroshio current weakens north of the northeastern tip of Luzon Island (approximately 18°N) and strengthens south. A significant negative correlation was found between the PDO index and cumulative precipitation within the Cagayan River basin, as measured by the Tropical Rainfall Measuring Mission (TRMM) during this period. SChl-a concentrations thrive in the Cagayan River estuary because precipitation, geostrophic currents, and local bathymetry create an ideal environment that retains nutrient-dense materials. During the negative phase of the PDO, the pattern of the geostrophic current prevents the nutrient-poor Kuroshio water from entering the South China Sea via the southern Luzon Strait and traps the SChl-a in this sea area. This study elucidates the complex relationship between terrestrial precipitation and oceanic currents in regulating SChl-a concentrations in this important ecosystem under climatic variability.