New Radiocarbon Constraints on the Upwelling of Abyssal Water to the Ocean’s Surface
New Radiocarbon Constraints on the Upwelling of Abyssal Water to the Ocean’s Surface
复制标题
深海水上升到海洋表面的新放射性碳限制
DOI：
10.1007/978-3-642-84608-3_14
复制
发表时间：
1993
期刊：
影响因子：
3.7
通讯作者：
B. Samuels
中科院分区：
文献类型：
--
作者：
J. Toggweiler;B. Samuels
根据北太平洋深层水和南极表层水的Δ 14 C差异，比较了7个不同海洋模式的模拟结果。这组模型产生了北太平洋-南极Δ 14 C的差异范围在-173‰和-108‰之间，除了最小的差异之外，所有差异都大大大于实际的爆炸前差异，-80到-110‰。预测值与从太平洋向南流出的中层水的数量高度相关。大部分南极底层水在中等深度处流回海盆的环流产生最小的北太平洋-南极Δ 14 C差异，而所有底层水流入通过温跃层上升的环流产生最大和最小的实际差异。根据模型，上升的深海水被夹带到风驱动的温跃层水向赤道的收敛。当它到达表面时，它向南北扩散，沿着赤道产生Δ 14 C最小值。对原子弹爆炸前和爆炸后Δ 14 C数据的详细分析表明，热带太平洋最古老的水实际上是在赤道以南发现的，与秘鲁的上升流有关，而不是沿着赤道的上升流。Toggweiler等人（1991年）追踪了秘鲁上升流中的低Δ 14 C信号，到达南极洲周围表面的深水，这些深水被绕极风向北推入温跃层。根据这些模型，即使少量的深海水（~ 3 × 10 6 m3·s-1）通过温跃层上涌，也会在表层Δ 14 C分布中留下未观测到的特征信号。人们得出的一般结论是，世界海洋中几乎没有与自上而下的温盐环流相关的上升流。事实上，所有的深海水涌上海洋表面都发生在南极洲周围，那里的水主要是由风驱动的。这一结论对碳循环的影响进行了讨论。
The output from seven different ocean model simulations is compared on the basis of the Δ14C difference between North Pacific deep water and Antarctic surface water. This set of models produces a range of North Pacific-Antarctic Δ14C differences between -173‰ and -108‰, all but the smallest of which are substantially larger than the actual pre-bomb difference, -80 to -110‰. Predicted values are highly correlated with the quantity of mid-depth water which flows out of the Pacific to the south. A circulation in which most of the Antarctic bottom water flows back out of the basin at mid-depth produces the smallest North Pacific-Antarctic Δ14C differences, whereas a circulation in which all the inflow of bottom water upwells through the thermocline produces the largest and least realistic differences. According to the models, upwelled abyssal water becomes entrained into the wind-driven convergence of thermocline water toward the equator. When it reaches the surface it spreads to the north and south, producing a Δ14C minimum along the equator. A detailed analysis of both pre-bomb and post-bomb Δ14C data indicates that the oldest water in the tropical Pacific is actually found south of the equator and is associated with the upwelling off Peru, not the upwelling along the equator. Toggweiler et al. (1991) trace the low-Δ14C signal in the Peru upwelling to deep water raised to the surface around Antarctica which is pushed northward into the thermocline by circumpolar winds. According to the models, even a small amount of abyssal water upwelling through the thermocline (~3x106 m3·s -1) leaves a characteristic signal in the surface Δ14C distribution which is not observed. One is left with the general conclusion that there is very little upwelling associated with a top-to-bottom thermohaline circulation in the world ocean. Virtually all the upwelling of abyssal water to the ocean’s surface occurs around Antarctica where it is mainly wind-forced. The implications of this conclusion for the carbon cycle are discussed.