Chlorofluoromethanes in the northeast Pacific Ocean: Measured vertical distributions and application as transient tracers of upper ocean mixing
Chlorofluoromethanes in the northeast Pacific Ocean: Measured vertical distributions and application as transient tracers of upper ocean mixing
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DOI：
10.1029/jc087ic12p09441
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发表时间：
1982-11
影响因子：
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通讯作者：
R. Gammon;J. Cline;D. Wisegarver
中科院分区：
文献类型：
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作者：
R. Gammon;J. Cline;D. Wisegarver
人造氯氟甲烷CCl3F （F-11）和CCl2F2（F-12）的垂直分布已在北太平洋东部深度超过500米的两个地点进行了测量。在这两个地点（北纬46°，西经125°的华盛顿-俄勒冈海岸和北纬50°，西经140°的阿拉斯加湾），发现卤甲烷浓度随着混合层以下深度的增加呈指数下降。在50°N条件下，F-11的表面浓度（3.2×10−12 mol/l）与实测大气浓度（190 pptv）达到饱和平衡。测量到的氟氯甲烷剖面已根据指数驱动的保守示踪剂垂直扩散/平流进入无底海洋的一维模型进行了解释。在“瞬态稳态”的适当极限下，投影剖面是由平流扩散尺度深度H描述的简单指数，深度H是垂直涡扩散系数Kz、上升流速度w和示踪剂浓度指数增长的特征时间τ的函数。两个海域的氟利昂温跃层深度在H≃120-140 m范围内，其中F-12一般比F-11深10-20%。在50°N处，F-11和F-12垂直剖面具有一致的垂直扩散系数（Kz ~ 1.2 ~ 1.3 cm2 s−1）和上升速度（w≈12 ~ 14 m yr−1）。该模型还允许从一种指数驱动的瞬态示踪剂（氟里昂）到另一种示踪剂（化石燃料二氧化碳）进行简单的缩放，从而预测北太平洋东部化石燃料二氧化碳的平均渗透深度约为300米。
The vertical distributions of the man-made chlorofluoromethanes CCl3F (F-11) and CCl2F2(F-12) have been measured at two locations in the eastern North Pacific Ocean to depths greater than 500 m. At both sites (46°N, 125°W off the Washington-Oregon coast and 50°N, 140°W in the Gulf of Alaska) the halomethane concentrations were found to fall off exponentially with increasing depth below the mixed layer. For F-11 at 50°N, the surface concentration (3.2×10−12 mol/l) was found to be in saturation equilibrium with the measured atmospheric concentration (190 pptv). The measured chlorofluoromethane profiles have been interpreted in terms of a one-dimensional model for the vertical diffusion/advection of an exponentially driven, conservative tracer into a bottomless ocean. In the appropriate limit of ‘transient steady state’ the projected profiles are simple exponentials described by an advective-diffusive scale depth H, which is a function of the vertical eddy diffusivity Kz, the upwelling velocity w, and the characteristic time τ for the exponential growth of the tracer concentration at the boundary. At the two ocean locations studied the freon thermocline depth scales were in the range H ≃ 120–140 m, with F-12 generally 10–20% deeper than F-11. At 50°N the F-11 and F-12 vertical profiles gave consistent values of vertical diffusivity (Kz ∼ 1.2–1.3 cm2 s−1) and upwelling velocity (w ≃ 12–14 m yr−1). The model also allows a simple scaling from one exponentially driven, transient tracer (freon) to another (fossil fuel CO2), leading to a predicted mean depth of penetration of fossil fuel CO2 of approximately 300 m in the eastern North Pacific.