OFFshore freshened groundwater systems – Emergence and persistence analysis by geochemical modellING (OFFING)

近海淡水化地下水是世界大陆边缘地区普遍存在的现象。由于对水资源、生态系统功能和全球元素收支的影响，在过去的二十年里，OFG的识别和预测越来越受到人们的关注。然而，尽管最近的科学进步，我们的知识的侵位机制和淡水在近海环境的演变仍然是粗略的。在许多情况下，不知道OFG体目前是否正在积极充电，或者是过去环境条件的残留物。拟议的研究将通过将创新的一维和二维数值输运-反应模型应用于IODP在新西兰近海（317航段）和新泽西近海（313航段）两个大陆边缘钻探工作的地球化学数据来解决这一知识差距。到目前为止，我们对这些地区OFG流动模式及其随时间的发展的看法基本上来自大规模的水文地质模型。然而，这些数据不能充分再现（由于空间分辨率不足），甚至与IODP钻探的现有地球化学数据相冲突。在这个建议中，我们建议进行前所未有的，定量评价孔隙水地球化学数据从几个钻孔岩芯，以限制和评估的定位机制和时间OFG在腿313和317。我们的研究结果可能对可持续开发OFG作为沿海城市的饮用水源及其在全球元素循环中的作用具有重要意义。

Offshore freshened groundwater (OFG) is a ubiquitous phenomenon in continental margins worldwide. The identification of OFG occurrences and the prediction of their volumes gained increasing attention over the past two decades due to implications for water resources, ecosystem function and global element budgets. However, in spite of recent scientific progress, our knowledge of emplacement mechanisms and the evolution of fresh groundwater in the offshore environment still remains sketchy. In many cases, it is not known if OFG bodies are actively recharged at present or are rather remnants of past environmental conditions. The proposed study will address this knowledge gap by applying innovative 1D and 2D numerical transport-reaction models to geochemical data from IODP drilling efforts at two continental margins, offshore New Zealand (Leg 317) and New Jersey (Leg 313). To date, our perception of OFG flow patterns in these areas and their development over time are essentially derived from large-scale hydrogeological models. These, however, do not sufficiently reproduce (due to insufficient spatial resolution) or are even in conflict with available geochemical data from IODP drilling. In this proposal, we suggest conducting an unprecedented, quantitative evaluation of pore water geochemical data from several drill cores in order to constrain and evaluate emplacement mechanisms and timing of OFG at Legs 313 and 317. Our findings may have important implications for sustainable exploitation of OFG as a source of potable water in coastal cities and its role in global element cycles.