Simulation of Oxygen Isotopes in a Global Ocean Model
Simulation of Oxygen Isotopes in a Global Ocean Model
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全球海洋模型中的氧同位素模拟
DOI：
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发表时间：
1999
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通讯作者：
T. Wolff
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作者：
A. Paul;S. Mulitza;J. Pätzold;T. Wolff
我们将海水的氧同位素组成δ 18 Ow纳入全球海洋模型，该模型基于地球物理流体动力学实验室（GFDL）的模块化海洋模型（MODEM，第2版）。在第一个实验中，该模型运行到平衡，以模拟当今的海洋;在第二个实验中，南极地表水（AAS W）的氧同位素组成被设置为一个恒定值，以间接解释海冰的影响。我们用观测资料检验了δ 18 Ow的深度分布。此外，我们还计算了方解石δ 18 Oc的平衡分馏，并与底栖有孔虫δ 18 O进行了比较。模拟的δ 18 Ow分布与GEOSECS数据比较吻合。我们表明，δ 18 Ow值可以用来表征不同的水团。然而，全球海洋模式的暖偏差产生的δ 18 Oc值在2 km深度以上偏轻约0.5%，并在2 km深度以下显示出虚假的垂直梯度。我们的最终目标是解释丰富的有孔虫δ 18 O数据在古海洋中的水团变化，例如在末次冰盛期（LGM）。这就需要对全球海洋模式的暖偏置进行修正。此外，该模式可能必须与简单的大气和海冰模式相耦合，这样既不需要指定海表盐度（SSS）也不需要指定表面δ 18 Ow，也可以避免使用现有的δ 18 Ow-盐度关系。
We incorporate the oxygen isotope composition of seawater δ18Ow into a global ocean model that is based on the Modular Ocean Model (MOM, version 2) of the Geophysical Fluid Dynamics Laboratory (GFDL). In a first experiment, this model is run to equilibrium to simulate the present-day ocean; in a second experiment, the oxygen isotope composition of Antarctic Surface Water (AAS W) is set to a constant value to indirectly account for the effect of sea-ice. We check the depth distribution of δ18Ow against observations. Furthermore, we computed the equilibrium fractionation of the oxygen isotope composition of calcite δ18Oc from a paleotemperature equation and compared it with benthic foraminiferal δ18O. The simulated δ18Ow distribution compares fairly well with the GEOSECS data. We show that the δ18Ow values can be used to characterize different water masses. However, a warm bias of the global ocean model yields δ18Oc values that are too light by about 0.5 %o above 2 km depth and exhibit a false vertical gradient below 2 km depth. Our ultimate goal is to interpret the wealth of foraminiferal δ18O data in terms of water mass changes in the paleocean, e.g. at the Last Glacial Maximum (LGM). This requires the warm bias of the global ocean model to be corrected. Furthermore the model must probably be coupled to simple atmosphere and sea-ice models such that neither sea-surface salinity (SSS) nor surface δ18Ow need to be prescribed and the use of present-day δ18Ow-salinity relationships can be avoided.