東南亞河川流域及海洋之碳循環---總計畫(II)
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Date
2005-12-23
Authors
陳鎮東
王樹倫
林曉武
吳朝榮
莊秉潔
彭宗仁
楊盛行
鄭利榮
鍾竺均
羅建育
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Abstract
碳循環與全球溫室效應及聖嬰現象息息相關，十餘年來國際間之大型計畫，如全球海洋通量聯合研究(Joint Global Ocean Flux Study，由International Geosphere Biosphere Programme及Scientific Committee on Oceanic Research共同組成)，全球海洋環流實驗(World Ocean Circulation Experiment，由聯合國系統之World Climate Research Programme贊助)及海陸地區交互作用(Land-Ocean Interaction in the Coastal Zone，由IGBP贊助)均以海洋之碳循環為主軸。然而JGOFS及WOCE之重點為大洋，而LOICZ之重點為河川、河口及沿海地區。近年來JGOFS及LOICZ已開始注意邊緣海之研究，並在報告人之倡導下，成立了JGOFS/LOICZ Continental Margins Task Team(CMTT)，由報告人擔任第一任主席。我國在CMTT始終保持相當影響力，如國科會海科中心前主任劉康克曾擔任CMTT共同主席，目前依然負責CMTT總結報告書之編撰。然而，一則JGOFS計畫已於2003年底結束，二則為求跨領域之進展，IGBP與International Human Dimensions Programme(IHDP)、WCRP及DIVERSITAS將以碳、水、食物及人體健康四大主軸為經，海、陸及大氣三領域為緯，繼續推動今後十年之第二階段研究，並於2002年1月共同成立聯合碳研究計畫(Global Carbon Project; GCP)，IGBP推薦報告人擔任GCP科學指導委員會之委員。IGBP及GCP均認為今後全球變遷研究應加強區域性計畫。有鑑於上述國際全球變遷研究之最新進展，以及我國在全球變遷研究東南亞區(SARCS)之主導地位，報告人提出「東南亞河川流域及海洋之碳循環計畫」，並由國科會永續會資助，92年8月起開始執行台澎金馬地區及南海海盆之水域碳循環研究。重點如下：(1)南海海盆真光層、中層水、底層水及沈積物內之碳循環及與菲律賓海、蘇祿海、巽它海峽之交換；(2)南海周邊地區河川、湖沼、水庫所釋出至大氣之CO2、CH4及N2O通量，以及沈積物所儲藏之有機及無機碳；(3)南海周邊地區河川所輸送入海之溶解態及顆粒態有機與無機碳通量；(4)上述碳通量於河川、湖泊、大陸棚、大陸坡及南海海盆之反應、變化及最終去處；(5)地下水與海洋交換之關聯；(6)氣候海洋模式及海陸交互作用；(7)興建水庫後河川碳通量之變化，及對沿海地區及大陸棚湧升流、底棲生物及漁業之影響；及(8)大氣沈降中之微量元素(鐵、磷及硝酸鹽等)對生產力之影響。總計畫負責安排航次及地下水之採樣。以上結果可作為其它海盆之參考及供GCP全球循環模式使用。其中第(6)項亦可供IGBP II之水循環以及食物兩大研究群參考。上述研究除需要海洋化學學者外，尚需地球化學及海洋生物學者之支援。本計畫已完成之採樣包括河川流域與海域等區域。河川流域採樣包括台灣本島河川與湖泊；大陸地區於長江口及福建九龍江以南之河流，包括九龍江、珠江與各支流；東南亞部份包括越南、寮國、柬埔寨、泰國、緬甸、馬來西亞、新加坡、印尼、汶萊及菲律賓之數十條河流。海域部分已前往珠江口及湄公河口，進行由河口、大陸棚、大陸坡至南海海盆之採樣。原則上每年除於台灣採樣三、四次之外，會安排一次至南海周邊國家之河川流域採樣一次。海上工作則擬每年申請三十天之海研一號及十六天之海研三號船期，儘可能逐年前往珠江口、湄南河、紅河和湄公河口外，進行由河口、大陸棚、大陸坡至南海海盆之採樣。由於生物作用影響碳循環甚巨，因此與生物生長密切相關之N、P及葉綠素，亦為除了碳因子(pCO2, pH, alkalinity, PIC, POC, DOC及DIC)之外之重要分析項目。同時，南海之相關研究免不了需周邊國家配合，方可順利取得主要河川及各國大陸棚上之資料，因此已由SARCS祕書處取得經費，先後資助了11個SARCS會員國之相關計畫，目前已有泰國、寮國、越南、馬來西亞、新加坡、印尼及菲律賓學者參與。也辦理了二次為期二週之South China Sea Regional Carbon Project Training Workshop，以求提升東南亞周邊國家相關研究人員之測量能力。2006年11月將再行辦理此訓練營。
Alarming as it is, human intervention in the carbon cycle over the last two centuries has caused anthropogenic carbon fluxes to become comparable in magnitude to major natural fluxes in the global carbon cycle. All the while, river basin development, most notably from the construction of dams and irrigation systems, has had a profound impact on riverine inputs of freshwater and carbon to the oceans. On a global scale, approximately 40% of the freshwater and particulate matter entering the oceans is transported by the ten largest rivers, and this is in the form of a buoyant plume on the open shelves. The situation we must confront, however, is that the number of large dams has increased a startling sevenfold since 1950, and within the next few decades, to make matters worse, more than 20% of total global river flow to the seas may be dammed or diverted. Given these facts, the export of carbon to the atmosphere and oceans from fluvial systems will most certainly be severely affected. Besides this, and put into simple terms, the more seriously freshwater outflow and the buoyancy effect are reduced by damming, the more likely it is that the continental shelves will operate under a much less efficient biological pump and that fish production will decrease accordingly. This three-year old project aims to continue developing several theories vis-a-vis carbon cycles in the fluvial and oceanic systems of the South China Sea region, such as its biogeochemical dimensions and fisheries along with their interactions and feedback, among others. This has been partially achieved by determining and explaining the following: Patterns and Variability: the current geographical and temporal distributions of the major stores and fluxes of carbon and associated elements in the SCS region, including the deep SCS basin, shelves, estuaries and river basins; Processes, Controls and Interactions: the underlying mechanisms and feedback that control the dynamics of the regional aquatic carbon cycle which encompasses its interactions with water and nutrient cycles as well as fisheries; and Future Dynamics of the Carbon Cycle: the range of plausible trajectories in the future as concerns the dynamics of the aquatic carbon cycles of the region. This is clearly a long-term project. The initial steps will be focussed on boundaries (air-sea, air-fluvial systems, river-sea, sea-sediments, reservoirs-sediment, sea-sea, euphotic zone-deep water), as well as temporal variations of physico-chemical properties and fisheries. Sampling has been done in and around Taiwan as well as in Changjiang, and rivers in Fujien, Guandong, Guanxi, Vietnam, Laos, Cambodia, Thailand, Myanmar, Malaysia, Singapore, Indonesia, Brunei and Philippines. In addition, OR Ⅰand III have been deployed off the continental shelves of Guandong, off Mekong River and on the Sunda shelf. Collaboration with Thailand, Vietnam, Laos, Singapore, Malaysia, Philippines and Indonesia has been funded separately. These activities, plus the two-week long training workshops held in Nov., 2003 and 2005 under the umbrella of the South China Sea Regional Carbon Project enhanced the possibility of success of this project. Another workshop will be held in Nov., 2006.
Alarming as it is, human intervention in the carbon cycle over the last two centuries has caused anthropogenic carbon fluxes to become comparable in magnitude to major natural fluxes in the global carbon cycle. All the while, river basin development, most notably from the construction of dams and irrigation systems, has had a profound impact on riverine inputs of freshwater and carbon to the oceans. On a global scale, approximately 40% of the freshwater and particulate matter entering the oceans is transported by the ten largest rivers, and this is in the form of a buoyant plume on the open shelves. The situation we must confront, however, is that the number of large dams has increased a startling sevenfold since 1950, and within the next few decades, to make matters worse, more than 20% of total global river flow to the seas may be dammed or diverted. Given these facts, the export of carbon to the atmosphere and oceans from fluvial systems will most certainly be severely affected. Besides this, and put into simple terms, the more seriously freshwater outflow and the buoyancy effect are reduced by damming, the more likely it is that the continental shelves will operate under a much less efficient biological pump and that fish production will decrease accordingly. This three-year old project aims to continue developing several theories vis-a-vis carbon cycles in the fluvial and oceanic systems of the South China Sea region, such as its biogeochemical dimensions and fisheries along with their interactions and feedback, among others. This has been partially achieved by determining and explaining the following: Patterns and Variability: the current geographical and temporal distributions of the major stores and fluxes of carbon and associated elements in the SCS region, including the deep SCS basin, shelves, estuaries and river basins; Processes, Controls and Interactions: the underlying mechanisms and feedback that control the dynamics of the regional aquatic carbon cycle which encompasses its interactions with water and nutrient cycles as well as fisheries; and Future Dynamics of the Carbon Cycle: the range of plausible trajectories in the future as concerns the dynamics of the aquatic carbon cycles of the region. This is clearly a long-term project. The initial steps will be focussed on boundaries (air-sea, air-fluvial systems, river-sea, sea-sediments, reservoirs-sediment, sea-sea, euphotic zone-deep water), as well as temporal variations of physico-chemical properties and fisheries. Sampling has been done in and around Taiwan as well as in Changjiang, and rivers in Fujien, Guandong, Guanxi, Vietnam, Laos, Cambodia, Thailand, Myanmar, Malaysia, Singapore, Indonesia, Brunei and Philippines. In addition, OR Ⅰand III have been deployed off the continental shelves of Guandong, off Mekong River and on the Sunda shelf. Collaboration with Thailand, Vietnam, Laos, Singapore, Malaysia, Philippines and Indonesia has been funded separately. These activities, plus the two-week long training workshops held in Nov., 2003 and 2005 under the umbrella of the South China Sea Regional Carbon Project enhanced the possibility of success of this project. Another workshop will be held in Nov., 2006.