A Global Model for Iodine Speciation in the Upper Ocean
A Global Model for Iodine Speciation in the Upper Ocean
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DOI：
10.1029/2019gb006467
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发表时间：
2020-04
影响因子：
5.2
通讯作者：
H. Hepach;M. Wadley;D. Stevens;T. Jickells;Ciaran Hughes;R. Chance;L. Tinel;L. Carpenter
中科院分区：
文献类型：
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作者：
H. Hepach;M. Wadley;D. Stevens;T. Jickells;Ciaran Hughes;R. Chance;L. Tinel;L. Carpenter
提出了海洋碘循环模型，该模型可以预测上层海洋的碘形态。该模型包括上层海洋的三层平流和扩散海洋环流模型以及嵌入该环流中的碘循环模型。图中显示了碘的两个主要储存库：碘化物和碘酸盐。碘酸盐在混合层中被还原为碘化物，与初级生产有关，与碘与碳 (I:C) 的比率相关。使用全局恒定的 I:C 比率无法获得与观测结果拟合满意的模型，当 I:C 比率依赖于海面温度（在低温下增加）时，可以获得最佳拟合。与观察到的碘化物分布的比较表明，当碘化物氧化回碘酸盐与混合层硝化相关时，获得最佳模型拟合。模型参数和过程受到扰动的敏感性测试表明，初级生产力、混合层深度、氧化、平流、地表淡水通量和 I:C 比都在确定表面碘化物浓度方面发挥作用，并且混合层中碘化物的时间尺度足够长，使得非局域过程变得重要。模拟的碘化物表面场与其他作者的参数化的比较表明，在存在观测的区域中具有良好的一致性，但在没有观测的区域中存在显着差异。这就提出了一个问题：现有的参数化是否能够捕捉到确定表面碘化物所涉及的全部过程，并表明迫切需要在目前没有参数化的地区进行观测。
An ocean iodine cycling model is presented, which predicts upper ocean iodine speciation. The model comprises a three‐layer advective and diffusive ocean circulation model of the upper ocean and an iodine cycling model embedded within this circulation. The two primary reservoirs of iodine are represented, iodide and iodate. Iodate is reduced to iodide in the mixed layer in association with primary production, linked by an iodine to carbon (I:C) ratio. A satisfactory model fit with observations cannot be obtained with a globally constant I:C ratio, and the best fit is obtained when the I:C ratio is dependent on sea surface temperature, increasing at low temperatures. Comparisons with observed iodide distributions show that the best model fit is obtained when oxidation of iodide back to iodate is associated with mixed layer nitrification. Sensitivity tests, where model parameters and processes are perturbed, reveal that primary productivity, mixed layer depth, oxidation, advection, surface freshwater flux, and the I:C ratio all have a role in determining surface iodide concentrations, and the timescale of iodide in the mixed layer is sufficiently long for nonlocal processes to be important. Comparisons of the modeled iodide surface field with parameterizations by other authors show good agreement in regions where observations exist but significant differences in regions without observations. This raises the question of whether the existing parameterizations are capturing the full range of processes involved in determining surface iodide and shows the urgent need for observations in regions where there are currently none.