An important factor for predicting the effect of increased CO₂ on future acidification of the ocean is a proper understanding of the interactions controlling production and dissolution of calcium carbonate minerals (CaCO₃). The production and dissolution of CaCO₃ in the ocean can be assessed over large spatial scales by measuring seawater calcium concentrations and total alkalinity (A_T), yet past studies suggest that there could be large discrepancies between calcium and A_T-based balances of the CaCO₃ cycle in the North Pacific and Indian Oceans. Here, we analyse water column samples collected along transects in the North Pacific, Southern Ocean, tropical Indian Ocean and Red Sea for their concentrations of calcium, nutrients, and A_T. We find that there is an excess calcium over A_T anomaly in the top 1000 m of the tropical Indian Ocean water-column. The source of this anomaly is the dissolution of subsurface gypsum deposits in the Red Sea. We find no evidence for calcium-over-A_T anomalies in the North Pacific, in contrast to previous studies. Our results show that, in most cases, calcium and A_T data agree well and can be used to reconstruct the marine CaCO₃ cycle.

预测CO ₂增加对未来海洋酸化的影响的重要因素是对控制碳酸钙矿物质（CaCO ₃）的产生和溶解的相互作用的正确理解。可以通过测量海水中的钙浓度和总碱度（A _T），在较大的空间范围内评估CaCO ₃在海洋中的产生和溶解，但过去的研究表明，钙和基于A _T的平衡之间可能存在较大差异。碳酸钙₃在北太平洋和印度洋循环。在这里，我们分析了在北太平洋，南洋，热带印度洋和红海沿样带采集的水柱样品中的钙，养分和A _T浓度。我们发现，在印度洋热带水柱的前1000 m处，钙含量超过了A _T异常。这种异常的根源是红海中地下石膏沉积物的溶解。我们发现了钙过一个没有证据_ŧ在北太平洋的异常，而相比之下，以前的研究。我们的结果表明，在大多数情况下，钙和A _T数据吻合良好，可用于重建海洋CaCO ₃循环。