The Passage of the Bomb Radiocarbon Pulse into the Pacific Ocean
The Passage of the Bomb Radiocarbon Pulse into the Pacific Ocean
复制标题
炸弹放射性碳脉冲进入太平洋
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
K. F. Reden
中科院分区：
文献类型：
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作者：
W. Jenkins;K. Elder;A. McNichol;K. F. Reden
我们报告并比较了1991年和2005年在南太平洋沿150°W的2个经向海洋学断面上的放射性碳观测结果。这些分布反映了核武器产生的14C逐渐渗透到海洋温跃层中。相对于我们的分析标准化中任何可能的漂移，14年来职业之间的变化明显很大。在该剖面1600 m以上网格化数据计算得到的差场在200 ~ 300 m以上随时间显著降低（Δ14C接近40 ~ 50‰），与原子弹爆炸后大气14C水平的年代际下降一致。以南极中间水（AAIW）低盐度岩心为中心的强烈正异常（随时间增加）在Δ14C接近50-60‰，是该水体中14C瞬变下游演化的明确标志。我们利用这一观测结果估计了南太平洋东南部AAIW“源区”的过境时间，并计算了该水团的有效储集年龄。两个剖面显示深海14C分布变化不大，但变化显著。1991 ~ 2005年，在55°S以北2000 m以下，Δ14C上升了9‰。总的来说，这种变化伴随着盐度和溶解氧的适度增加，以及溶解二氧化硅的轻微减少。这些变化表明通风更大。“磷酸盐星”的计算也表明，这可能是由于从南大洋转向北大西洋深水作为深海南太平洋的通风源。
We report and compare radiocarbon observations made on 2 meridional oceanographic sections along 150°W in the South Pacific in 1991 and 2005. The distributions reflect the progressive penetration of nuclear weapons-produced 14C into the oceanic thermocline. The changes over the 14 yr between occupations are demonstrably large relative to any possible drift in our analytical standardization. The computed difference field based on the gridded data in the upper 1600 m of the section exhibits a significant decrease over time (approaching 40 to 50‰ in Δ14C) in the upper 200–300 m, consistent with the decadal post-bomb decline in atmospheric 14C levels. A strong positive anomaly (increase with time), centered on the low salinity core of the Antarctic Intermediate Water (AAIW), approaches 50–60‰ in Δ14C, a clear signature of the downstream evolution of the 14C transient in this water mass. We use this observation to estimate the transit time of AAIW from its “source region” in the southeast South Pacific and to compute the effective reservoir age of this water mass. The 2 sections show small but significant changes in the abyssal 14C distributions. Between 1991 and 2005, Δ14C has increased by 9‰ below 2000 m north of 55°S. This change is accompanied overall by a modest increase in salinity and dissolved oxygen, as well as a slight decrease in dissolved silica. Such changes are indicative of greater ventilation. Calculation of “phosphate star” also indicates that this may be due to a shift from the Southern Ocean toward North Atlantic Deep Water as the ventilation source of the abyssal South Pacific.