Late Pleistocene Paleoceanography of the Kuroshio Current in the Area Offshore Southeast Taiwan

台灣東南外海黑潮之晚更新世古海洋

陳民本(Min-Pen Chen) ； 黃兆愷(Chao-Kai Huang) ； 羅立(Lih Lo) ； 汪中和(Chung-Ho Wang)

《Terrestrial, Atmospheric and Oceanic Sciences》 3卷1期 (1992/03) Pp. 81-110

摘要

黑潮以1.5至2節的流速從台灣東南外海流往東北外海。其夏季的海表面水温介於28℃與29℃之間，而冬季則降至25℃至26℃之間。黑潮洋流的表層鹽度介於34.2‰與34.7‰之間。本文對於台灣東南外海黑潮古海洋之研究是以現今的海洋狀況以及海床上所採的19個箱型岩心和7支活塞岩心的岩心頂部沈積物中所含的浮游性有孔蟲群集作爲研究的基礎。
沈積的有孔蟲群集可以分成近岸及遠洋兩群。除了Globigerinoides ruber, G. sacculifer, Pulliniatinav obliquiloculata和Neogloboquadrina dutertrei四個含量較多的種之外，近岸群的重要種有Globigerinita glutinata和Globigerinoides bulloides；遠洋群的重要種有Globorotalia tumida和G. menardii。
在上次冰河期，兩支活塞岩心中所含的浮游性有孔蟲群集，再由轉換函數所計算出的夏季表層水溫仍介於28℃和29℃之間，上次間冰期的水溫甚至還高過29℃。但在冬季，上次冰河期的表層水温介於25℃和22℃；不過間冰期冬季的平均表層水溫僅比冰河期高大約1℃。
從氧同位素資料的計算，在上次冰河期間18,500年至17,500年前的海水面最低時期，當時海水面比現今低了150公尺。在98,000年前，上次間冰期的海水面最高期的海水面仍比現今低10尺。海水面突然上升的時期，黑潮流速會加快，而當海水面持續上升但黑潮流速減慢時，黑潮主流有向東偏移的現象。

並列摘要

The Kuroshio current flows from the southeast toward the northeast off eastern Taiwan at a speed of 1.5-2 knots. Its surface water maintains a temperature of28-29℃ in summer and 25-26℃ in winter. The salinity of the surface water is in the range of 34.2-34.7‰. The paleoceanography of the Kuroshio current off southeast Taiwan is based on recent hydrographic data and planktonic foraminiferal assemblages which have been identified and counted from the core tops of 19 box-cored and 7piston-cored sediments.
The deposited foraminiferal assemblages are divided into two major groups: neritic and pelagic groups. Besides four dominant species, Globigerinoides ruber, G. sacculifer, Pulleniatina obliquiloculata and Neogloboquadrina dutertrei, the remarkable species in the neritic group are Globigerinita glutinata and Globigerina bulloides. In the pelagic group, Globorotalia tumida and G. menardii are two prominent species.
During the last glacial epoch, the calculated water temperatures from the transfer function of the planktonic foraminiferal assemblages in two piston-cored sediments show that the surface water temperature fluctuated in the range of 28-29℃ in summer, but the calculated temperatures invariably exceeded 29℃ during the last interglacial period. In winter, the calculated temperature varied in the range of 22-25℃; however, the average temperature in the last interglacial epoch was only about 1℃ greater than that in the period of the last glaciation.
From the calculation of oxygen isotopic data, the lowest stand of sea level was probably 150 m below the present mean sea level for 18,500-17,500 years B.P.. The highest stand of sea level was still about 10 m below the present level about 98,000 years ago. The Kuroshio current would have had a great speed if the sea level had been raised abruptly in a short period. The main axis of the Kuroshio current might have shifted toward the east as the current decelerated and the sea level still rose.