DECADE TIME SCALE VARIABILITY OF VENTILATION IN THE NORTH-ATLANTIC - HIGH-PRECISION MEASUREMENTS OF BOMB RADIOCARBON IN BANDED CORALS
DECADE TIME SCALE VARIABILITY OF VENTILATION IN THE NORTH-ATLANTIC - HIGH-PRECISION MEASUREMENTS OF BOMB RADIOCARBON IN BANDED CORALS
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DOI：
10.1029/jc094ic03p03271
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发表时间：
1989-03-15
影响因子：
3.6
通讯作者：
DRUFFEL, ERM
中科院分区：
文献类型：
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作者：
DRUFFEL, ERM
首次对北大西洋两个地点的带状珊瑚进行了上层海洋的高精度放射性碳测量。马尾藻海的百慕大和墨西哥湾流的佛罗里达海峡1950年后的记录之间的显著差异说明了每个地点上层海洋中不同的混合过程。晚冬期间，马尾藻海北部的对流翻转与18°水的形成有关，这有利于在深海储存大量的炸弹放射性碳，这是20世纪60年代百慕大Δ14C信号减弱的原因。用多箱等周期混合模式估算了1950-1983年马尾藻海水柱上部700m的通风率。为了满足珊瑚中核弹放射性碳的时间历史，采用了反模型，即计算了核弹后时期的水质量更新率。利用在GEOSECS(1972-1973年)和海洋瞬变示踪器(1980-1981)调查期间进行的海水放射性碳量测来约束由该模型计算的次表层放射性碳值。结果表明，马尾藻海的水团更新率在1963-1964年间很高，在20世纪60年代末有所下降，在70年代的大部分时间里保持在较低的水平。由14C得到的水团更新记录比由马尾藻海等温盐度得到的记录早了大约4年[Jenkins，1982]，说明珊瑚14C记录在很大程度上是由海洋环流的变化控制的，而不是由大气中的二氧化碳交换控制的。
The first high‐precision radiocarbon measurements for the upper ocean are presented for banded corals from two sites in the North Atlantic Ocean. The striking dissimilarities between the post‐1950 records at Bermuda in the Sargasso Sea and the Florida Straits in the Gulf Stream illustrate the different mixing processes in the upper ocean at each site. Convective overturn associated with 18° degree water formation during late winter in the northern Sargasso Sea facilitates storage of considerable quantities of bomb radiocarbon at depth, which accounts for the damping of the Δ14C signal at Bermuda during the 1960s. A multibox isopycnal mixing model is used to estimate the ventilation rate of the upper 700 m of the water column in the Sargasso Sea from 1950 to 1983. An inverse model is used; that is, the water mass renewal rate was calculated for the post‐bomb period in order to satisfy the bomb radiocarbon time history in the corals. Sea water radiocarbon measurements made during the GEOSECS (1972–1973) and Transient Tracers in the Ocean (1980–1981) surveys are used to constrain the subsurface radiocarbon values calculated by the model. Results show that the rate of water mass renewal in the Sargasso Sea was high during 1963–1964, decreased during the late 1960s, and remained low during most of the 1970s. The14C‐derived record of water mass renewal precedes by about 4 years that derived from isopycnal salinity in the Sargasso Sea [Jenkins, 1982], illustrating that the coral14C record is controlled to a large extent by changes in ocean circulation rather than by atmospheric exchange of CO2.