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

近海淡水地下水是全球大陆边缘普遍存在的一种现象。过去二十年来，由于对水资源、生态系统功能和全球要素预算的影响，对OFG发生情况的确定及其数量的预测受到越来越多的关注。然而，尽管最近取得了科学进展，我们对近海环境中的侵位机制和淡水地下水演化的了解仍然粗略。在许多情况下，不知道OFG物体目前是积极充电的，还是过去环境条件的残余物。拟议的研究将通过将创新的一维和二维数值传输-反应模型应用于IODP在新西兰近海(第317段)和新泽西(第313段)两个大陆边缘的钻探工作的地球化学数据，解决这一知识差距。到目前为止，我们对这些地区的OFG流动模式及其随时间的发展的认识基本上来自于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钻探获得的现有地球化学数据相冲突。在这项建议中，我们建议对几个钻芯的孔隙水地球化学数据进行前所未有的定量评估，以限制和评估OFG在第313和317段的就位机制和时机。我们的发现可能对沿海城市可持续利用OFG作为饮用水来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.