Submarine groundwater discharge into coastal areas is a common global phenomenon and is rapidly gaining scientific interest due to its influence on marine ecology, the coastal sedimentary environment, and its potential as a future freshwater resource. We conducted an integrated study of hydroacoustic surveys combined with geochemical pore water and water column investigations at a well‐known groundwater seep site in Eckernförde Bay (Germany). We aim to better constrain the effects of shallow gas and submarine groundwater discharge on high‐frequency multibeam backscatter data and to present acoustic indications for submarine groundwater discharge. Our high‐quality hydroacoustic data reveal hitherto unknown internal structures within the pockmarks in Eckernförde Bay. Using precisely positioned sediment core samples, our hydroacoustic‐geochemical approach can differentiate intrapockmark regimes that were formerly assigned to pockmarks of a different nature. We demonstrate that high‐frequency multibeam data, in particular the backscatter signals, can be used to detect shallow free gas in areas of enhanced groundwater advection in muddy sediments. Intriguingly, our data reveal relatively small (typically <15 m across) pockmarks within the much larger, previously mapped pockmarks. The small pockmarks, which we refer to as “intrapockmarks,” have formed due to the localized ascent of gas and groundwater; they manifest themselves as a new type of “eyed” pockmarks, revealed by their acoustic backscatter pattern. Our data suggest that, in organic‐rich muddy sediments, morphological lows combined with a strong multibeam backscatter signal can be indicative of free shallow gas and subsequent advective groundwater flow.

中文翻译：

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波罗的海埃克恩弗德湾的声学数据和沉积核揭示了复杂的眼状斑点和海底地下水排放

将海底地下水排放到沿海地区是一种普遍的全球现象，并且由于其对海洋生态，沿海沉积环境及其作为未来淡水资源的潜力的影响，正在迅速引起科学兴趣。我们在Eckernförde湾（德国）的一个著名的地下水渗漏现场进行了水声调查，地球化学孔隙水和水柱调查的综合研究。我们旨在更好地限制浅层气体和海底地下水排放对高频多波束反向散射数据的影响，并提出海底地下水排放的声学指示。我们高质量的水声数据揭示了埃克恩弗德湾麻点内迄今为止未知的内部结构。使用精确定位的沉积岩心样本，我们的水声地球化学方法可以区分以前被分配给不同性质的麻点的内部麻点制度。我们证明了高频多波束数据，特别是反向散射信号，可以用于检测泥沙中地下水平流增强区域的浅层游离气体。有趣的是，我们的数据揭示了在较大的，先前映射的麻点内相对较小的麻点（通常小于15 m）。由于天然气和地下水的局部上升，形成了小的麻点，我们称之为“内麻点”。它们表现出一种新型的“眼”状麻点，通过其声音的反向散射图案显示出来。我们的数据表明，在富含有机物的泥质沉积物中，