OSCAR - Oceanographic and Seismic Characterisation of heat dissipation and alteration by hydrothermal fluids at an Axial Ridge

年轻洋壳的冷却是将热量从固体地球转移到水圈的主要物理过程。在大洋中脊附近，海水通过多孔和断裂的玄武岩地壳进行热液循环，从而控制了快速冷却。这些热液随后主要沿着洋脊排入海洋。在这个跨学科的项目中，我们将研究这种热损失和热液循环在固体地球和海洋中的影响。我们将首次推导出一个综合模型，该模型将受到地球物理、地质和物理海洋学数据的约束，其中包括固体地球和海洋中的路径，包括通过海底的通量，最快速的热交换发生在快速扩张的海脊附近，那里几乎没有沉积物，由热液流驱动。寒冷的海水进入断裂的玄武岩在地区上的脊侧翼和流动通过可渗透的地壳成为过热的轴向岩浆房附近。这些高度浮力的水迅速上升，并沿着脊轴沿着流入海洋，形成了独特的喷口，称为黑烟囱。一旦进入海洋，热水通过夹带与周围的冷水混合，并形成上升到中性密度点的羽流。卷吸过程可使羽流中水的体积增加几个数量级，从而提供了一种机制来加热并将致密沃茨提升远离底部边界层。作为全球温盐循环系统的一部分，这些沃茨水更容易进一步混合和加热。地壳中热液流的强度随着与脊轴的距离而衰减，因为地球化学蚀变产物堵塞了通道，改变了地壳的地球物理性质，随着年龄的增长，远洋沉积物将断裂的玄武质上地壳与上覆水隔离开来，阻止了直接的水交换。该项目将获得一个跨学科数据集，将物理海洋学和海洋物理学纳入一次数据采集航行。利用这些数据，我们将建立和参数化新的综合模型，这将提供宝贵的见解和新的制约因素的热过程靠近洋脊，包括一个可渗透的海底。这些数据和由此产生的模型将为综合多物理实验设定一个新的基准，并将使人们对洋脊的流体和热通量有一个新的认识，同样重要的是，将使人们更好地了解地球物理和海洋学数据在洋脊轴向环境中实际解决了什么问题，并使人们更好地了解一个可适用于世界各地类似洋脊系统的预测模型。

The cooling of young oceanic crust is the main physical process responsible for removing heat from the solid Earth to the hydrosphere. Close to the mid-ocean ridge rapid cooling is dominated by hydrothermal circulation of seawater through the porous and fractured basalt crust. This hydrothermal fluid is then discharged into the ocean mainly along the ridge. In this interdisciplinary project we will investigate the effects of this heat loss and hydrothermal circulation in both the solid Earth and the ocean. We will, for the first time, derive an integrated model which will be constrained by geophysical, geological and physical oceanography data that includes pathways in both the solid Earth and the ocean including fluxes through seabed.The most rapid heat exchange occurs close to the fast-spreading ridges, where there are little or no sediments, driven by hydrothermal flow. Cold ocean water enters the fractured basalt in areas on the ridge flanks and flows through the permeable crust becoming super-heated in the proximity of the axial magma chamber. This highly buoyant water ascends rapidly and escapes into the oceans along the ridge axis and is known to form distinct vents called black smokers. Once in the ocean the hot water mixes with the ambient cold water through entrainment and forms a plume that rises to its point of neutral density. The entrainment process may increase the volume of the water in the plume by several orders of magnitude thereby providing a mechanism to heat and lift the densest waters away from the bottom boundary layer. These waters are then more readily available for further mixing and heating as part of the global thermohaline circulation system. The intensity of the hydrothermal fluid flow in the crust decays with distance from the ridge axis because of clogging of the pathways by geochemical alteration products which changes the geophysical properties of the crust and with age, pelagic sediments isolate the fractured basaltic upper crust from the overlaying water preventing direct water exchange. Here conductive heat loss is determined by the thickness and structure of this layer of sediment.The project will acquire an interdisciplinary dataset which integrates physical oceanography and geophysics into a single data acquisition cruise. Using these data we will build and parameterise new integrated models that will provide valuable insight and new constraints of the thermal processes close to ocean ridges that includes a permeable seabed. These data and resultant models will set a new benchmark for integrated multi-physics experiments and will result in a new understanding of the fluid and heat fluxes at ocean ridges and, as importantly a better understanding of what geophysical and oceanographic data actually resolve in the context in an oceanic axial ridge setting, and a predictive model that can be applied to similar ocean ridge systems world-wide.