The flux of water, nutrients, carbon and salt through the subsurface at the land-sea interface is an important control on coastal nutrient processes, salinization of coastal aquifers and carbon balances of the coastal zone. However, these fluxes are often spatially and temporally complex and difficult to quantify, especially in high-energy mesotidal systems. Here we use vertical temperature profiles along a morphologically complex mesotidal high-energy beachface to map and quantify water infiltration and exfiltration on the island of Spiekeroog, Germany. Water fluxes were quantified using heat transport calculations from three solutions to the 1D heat transport equation, and include 1) a steady state analytical solution, 2) a non-steady state numerical model and 3) a non-steady state analytical solution. The temperature profiles could clearly map areas of upwelling warm (up to 10 °C) groundwater during the winters of 2018 and 2019. These upwelling zones were focused on an intertidal runnel system and at the low water line, consistent with the current understanding of the site based visual observations and hydrogeological models. The steady state model provided good fits to the measured data in the winter when the seawater temperatures were not changing significantly, but was less able to reproduce the measured profiles in spring when seawater was warming. The steady state flux rates ranged from −110 to −43 mm d⁻¹ in the runnel and low water line to +43 mm d⁻¹ towards the high water line. The dynamic numerical model successfully captured the propagation of the seawater temperature signal into the subsurface and was able to reproduce the temperature profiles during both seasons. The flux estimates tended to be larger with the numerical model, with up to −150 mm d⁻¹ in the runnel and +110 mm d⁻¹ towards the high water line. The non-steady state analytical solution could only be applied to a limited time series due to the difficulty of logging temperatures in the subsurface at this highly dynamic site. Up to 1.5 days of data suggested fluxes that were considerably higher than the other two methods with best-estimates of −400 to −900 mm d⁻¹. Thermal Peclet numbers ranged from 0.2 to 2 suggesting that both conduction and advection of heat is important. This study demonstrates that the morphology of the beach face is an important control on spatial distribution of down-welling and upwelling zones along the beach and that temperature measurement combined with heat modelling are potentially useful methods for understanding the interactions between groundwater and the sea.

水，养分，碳和盐通过陆-海界面的地下通量是控制沿海养分过程，沿海含水层盐渍化和沿海地区碳平衡的重要手段。但是，这些通量通常在空间和时间上都很复杂，并且难以量化，尤其是在高能中介子系统中。在这里，我们使用沿形态复杂的中生高能滩面的垂直温度剖面图，对德国Spiekeroog岛上的水的渗透和渗出进行映射和量化。使用一维热传输方程的三个解通过热传导计算对水通量进行量化，包括1）稳态解析解，2）非稳态数值模型和3）非稳态解析解。温度剖面可以清楚地绘制出2018年和2019年冬季上升流温暖的地下水（最高10°C）的区域的图。这些上升流区域的重点是潮间带流道系统和低水位线，这与当前对地下水的认识相一致。基于现场的视觉观察和水文地质模型。当海水温度没有明显变化的冬季，稳态模型可以很好地拟合实测数据，但是当海水变暖时，春季静态模型无法重现实测数据。稳态通量率范围为-110至-43 mm d 符合当前对基于站点的视觉观测和水文地质模型的理解。在海水温度没有明显变化的冬季，稳态模型可以很好地拟合实测数据，但是当海水变暖时，春季静态模型无法再现实测的剖面。稳态通量率范围为-110至-43 mm d 符合当前对基于站点的视觉观测和水文地质模型的理解。在海水温度没有明显变化的冬季，稳态模型可以很好地拟合实测数据，但是当海水变暖时，春季静态模型无法再现实测的剖面。稳态通量率范围为-110至-43 mm d^-1在漏斗和低水线43毫米d ^-1朝向高水位线。动态数值模型成功地捕获了海水温度信号向地下的传播，并能够再现两个季节的温度曲线。在数值模型中，通量估计值往往会更大，在漏斗中可达-150 mm d ^-1，而在高水位线处可达+110 mm d ^-1。非稳态分析解决方案只能应用于有限的时间序列，这是因为在该高度动态的位置很难记录地下温度。长达1.5天的数据表明通量要比其他两种方法高得多，最佳估计值为-400至-900 mm d ^-1。热佩克雷特数在0.2到2之间，表明热量的传导和对流都很重要。这项研究表明，海滩面的形态是控制海滩上涌和下涌区的空间分布的重要控制，而温度测量与热模拟相结合是理解地下水与海洋相互作用的潜在有用方法。