「海洋酸化」是近年來相當受重視的議題之一，目前為止，以時間序列測站觀測海水酸化的區域大都位於開放性大洋，而在邊緣海地區尚未有深入的研究。因此本研究利用位於南海(邊緣海)的東南亞時間序列測站(SouthEast Asian Time-series Study, SEATS)，於1999年9月至2012年9月間共43個航次所測得之水文及碳化學參數等時間序列變化趨勢，探討南海海水酸化之情況，並與HOT和BATS兩個時間序列測站之觀測結果進行比較。
結果顯示，SEATS測站與其他大洋之時間序列測站(如HOT、BATS測站)同樣有pH逐年下降(-0.0018 yr-1)、nDIC逐年升高(1.3~1.4 mol kg-1 yr-1)的現象，顯示SEATS測站海水與其他大洋相仿，亦同樣在逐漸酸化中。
將SEATS測站與HOT和BATS兩測站相比較，其酸化的速率為：BATS (-0.0036yr-1)、HOT (-0.0007 yr-1)、SEATS (-0.0018 yr-1)。筆者認為各測站酸化速率的不同應與緯度有關，高緯度地區由於受到較多人為二氧化碳影響，其酸化速率最快(BATS)，而位於最低緯度的SEATS測站的酸化速率卻比HOT測站快，推測應為SEATS測站混合層深度逐年加深(約1.6m yr-1)所致。由於SEATS位於近熱帶地區，混合層都相當淺，因此混合層一旦加深，便帶更多下方較高DIC、TA及低pH的次表水至表層，造成觀測到的酸化速率加快。在2004~2008年間，其冬季混合層的深度，確實顯示較其他年份的混和層深度為深。在鹽度時間序列上也可觀測到類似的現象。因此造成SEATS測站的酸化速率較HOT為高，推測應是由於SEATS測站混合層深化的結果。

"Ocean acidification" is one of the most important and popular topics today. Our present knowledge from time-series studies has largely focused in the open ocean rather than in the marginal seas. In this study, a total of 43 cruises from September 1999 to September 2012 with measurements of the hydrological and carbon chemical parameters in surface seawater have been conducted to better understand the ocean acidification at SEATS (SouthEast Asian Time-series Study, SEATS) site in the northern South China Sea (SCS). A comparison of results from this station with those from the HOT (Hawaii Ocean Time-series) and BATS (Bermuda Atlantic Time-series Study) time series stations was thoroughly delineated.
Results shows that rate of the pH decrease between September 1999 to September 2012 was 0.0018 yr-1 at the SEATS site, and the normalized dissolved inorganic carbon concentration (nDIC) has increased at a rate of 1.3 ~ 1.4 mol kg-1 yr-1. Such results show that surface seawater at the SEATS station is acidifying in line with other oceanic region.
As compared to HOT (-0.0007 yr-1) and BATS (-0.0036 yr-1), surface seawater pH at SEATS station declines at a rate of -0.0018 yr-1. It has been suggested that the acidification rate of the surface seawater is latitudinally related, as seawater at the high latitude regions absorb more carbon dioxide than those of the lower latitudes. However, our observed results show that the acidification rate at the SEATS station is faster than the HOT station, presumably due to the increasing mixed layer depth at the SEATS became deeper (approximately 1.6m yr-1) during the study period. Comparing our results with those from the HOT and BATS stations, it appears that the SEATS station locates in a subtropical region where the mixed layer is relatively shallow. When the mixed layer becomes deeper, more higher DIC, TA but low pH sub-surface water reaches to the surface, causing surface seawater to be more acidic. From 2004 to 2008, the mixed layer depth was deeper than those of the other years and so is salinity. However, these were not observed at the other two stations. In other words, the deeper the mixed layer at the SEATS site, more acidic of seawater at the SEATS is.

誌謝...............................................................................................................i
摘要............................................................................................................ii
Abstract......................................................................................................iv
目錄..............................................................................................................vi
圖目錄....................................................................................................viii
表目錄........................................................................................................xi
壹、緒論.......................................................................................................1
1.1 前言................................................................................................1
1.2 東南亞時間序列測站緣起及文獻回顧.......................................9
1.3 研究區域之背景介紹..................................................................11
1.3.1 南海簡介...............................................................................11
1.3.2 南海水文特性.......................................................................14
1.3.3 南海的氣候型態……………………………….………..…16
1.4 研究目的......................................................................................19
貳、研究材料與方法................................................................................20
2.1 採樣方法………………………………..…………….………..20
2.2 研究方法………………………………..…………….………..23
2.2.1 酸鹼值( pH )之測定.…………..…………………………..23
2.2.2溶解態無機碳(DIC)之測定………………………………...23
2.2.3 海水滴定總鹼度(TA)之測定……………………………...25
2.2.4 海水中二氧化碳分壓(fCO2)之計算………………………26
2.2.5 海氣交換通量(CO2 flux)之計算…………………………..27
2.2.6 海水總溶解態無機碳碳同位素組成(13CDIC)之測定…….28
參、結果與討論.....................................................................................32
3.1 SEATS測站各化學水文參數之時間序列分布...........................32
3.1.1 溫鹽資料………...................................................................32
3.1.2 5m TA、DIC及13CDIC之時間序列變化...............................34
3.1.3 5m pHmeas.及pHcal.之時間序列變化…..................................39
3.1.4 a和c之時間序列變化......................................................42
3.1.5 二氧化碳海氣交換(CO2 flux)通量之時間序列變化…......43
3.2 SEATS測站與HOT及BATS測站之比較..................................48
3.2.1溫鹽時間序列變化比較........................................................49
3.2.2 碳化學參數時間序列變化比較...........................................52
肆、結論......................................................................................................61
伍、參考文獻..............................................................................................63

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網站資料
Mauna Loa Record (http://esrl.noaa.gov/gmd/ccgg/trends/)
HOT station data (http://hahana.soest.hawaii.edu/hot/hot_jgofs.html )
BATS station data (http://bats.bios.edu/index.html)
NASA (http://aquarius.nasa.gov/education-salinity.php)