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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/35316

Title: 2012年蘇拉颱風通過前後台灣東南外海海氣二氧化碳交換通量之變化
Variation of air-sea CO2 flux in surface water off southeast Taiwan in response to the passage of Typhoon Saola in 2012
Authors: Mi-Shuan Lee
李宓薰
Contributors: NTOU:Institute of Marine Environmental Chemistry and Ecology
國立臺灣海洋大學:海洋環境化學與生態研究所
Keywords: 海氣二氧化碳交換通量;二氧化碳分壓差;表水二氧化碳分壓;大氣二氧化碳分壓
air-sea CO2 flux;∆pCO2;pCO2 sw;pCO2 air
Date: 2013
Issue Date: 2013-10-07T02:53:29Z
Abstract: 過去關於颱風的研究文獻指出,颱風通過時強烈的風速可大幅提高海氣二氧化碳的交換通量。因此探討颱風通過前、後海氣二氧化碳交換通量的變化,對正確估算海洋對大氣二氧化碳的吸收能力,扮演了重要的角色。然而,受限於惡劣的海況及航次的安排,在颱風來臨前、後同一海域所取得之實際觀測數據可說非常的稀少。 本研究利用海研二號1893(2012/7/26-30)及1894B(2012/8/4-6)等兩個航次的觀測結果,比較了蘇拉颱風(2012/7/31-8/3)通過前、後,台灣東部黑潮海域二氧化碳分壓(pCO2)的變動情形。觀測結果顯示,颱風前,∆pCO2(= pCO2 sw-pCO2 air)介於 -37至41 atm之間;颱風後,介於 -36至38 atm之間。颱風前後大氣二氧化碳的源區主要皆出現在表水pCO2的相對高值與大氣pCO2的相對低值區,主要應是受高的表水pCO2所造成。相反的,大氣二氧化碳的匯區主要都出現在大氣pCO2的相對高值與表水pCO2的相對低值區,主要應是受陸地氣團所帶來之高的大氣pCO2所造成。颱風前,海氣二氧化碳交換通量平均值為 -0.05 mmolC/m-2/day-1;而颱風後平均值為0.05 mmolC/m-2/day-1;颱風通過時之平均值為0.48 mmolC/m-2/day-1。颱風前後之空間分布主要受∆pCO2的強弱所控制,風速的強弱的差異在颱風前後並不顯著。而颱風通過時與颱風前後的差異在於颱風時提高的風速遠高於颱風前後之風速,因此通量可能會大了7倍甚至更高。另外,推估出經過本研究海域的2個颱風(蘇拉、天秤颱風),夏季非颱風期間海水吸收4.25 molm-2 day-1的二氧化碳,颱風通過時海水釋放4.32 molm-2 day-1。換言之,2012年夏季本研究海域在非颱風期間所吸收之大氣二氧化碳,幾乎全部在颱風期間重新被釋放回大氣當中。 此外,夏季時亞熱帶海域多為大氣二氧化碳的源,且前人研究指出颱風通過時之高風速會大幅提高海氣二氧化碳的交換速率。因此,颱風通過基本上會增加此等海域向大氣釋放二氧化碳的通量。而本研究在台灣東岸黑潮流域之觀測結果,大致與前人的研究結果相符。
Previous studies suggest that strong winds can largely enhance air-sea CO2 exchange flux during the passage of typhoon. Understanding how air-sea CO2 exchange flux would response to the passage of typhoon is therefore essential to better quantify the carbon budget in the subtropical oceans. However, limited to the rough sea conditions and cruise arrangement, the field data of air-sea CO2 exchange flux just before and after typhoon passage are scarce. In this study, two cruises (OR2 1893, 2012/7/26-30 and OR2 1894B, 2012/8/4-6) off the southeast Taiwan were fortuitously conducted just pre- and post-Typhoon Saola passage (2012/8/1-3) in summer 2012, which thus provide a unique opportunity to examine the response of air-sea CO2 exchange flux to typhoon passage in the subtropical ocean. The results show that ∆pCO2 (the difference of partial pressure of CO2 between the surface water and the air = pCO2sw – pCO2air) ranged between -37 to 41 and -36 to 38 atm before and after the typhoon passage, respectively. The source area is generally associated with the occurrence of high pCO2sw, while the sink area is coincident with the appearance of high pCO2air, which may be resulted from the air mass from land. The averaged air-sea CO2 exchange flux was -0.05 and 0.05 mmolC m-2 day-1 before and after the typhoon passage, respectively, suggesting that the study area turned from a sink of atmospheric CO2 pre-typhoon passage to a CO2 source post-typhoon passage. The wind speeds difference between the pre- and post-typhoon periods was not significant so that it only play a minor role on the variation of air-sea CO2 flux in response to the typhoon passage. Nonetheless, the elevated wind speed during the period of typhoon passage might lead to CO2 efflux increase by about 7 times (~0.48 mmolC m-2 day-1). Furthermore, the amount of CO2 uptake during the non-typhoon period in summer was estimated to be about 4.25 mmolm-2, while the amount of CO2 release during the typhoon period was about 4.32 mmolm-2. In other words, the CO2 uptake during the non-typhoon period was almost totally release back to the atmosphere during the typhoon period. As a result, the study area was nearly neutral to the atmospheric CO2 in summer 2012. Finally, our result generally confirms the previous findings that the passage of typhoon may enhance CO2 release from ocean to the atmosphere in the subtropical oceans, which may represent a positive feedback to global warming.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0010083003
http://ntour.ntou.edu.tw/handle/987654321/35316
Appears in Collections:[海洋環境與生態研究所] 博碩士論文

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