Deep submarine groundwater discharge (DSGD) of fresh-brackish water was suggested to occur globally, yet its driving mechanism is not well constrained. Specifically, it is unclear whether the phenomenon may represent a steady-state condition of a hydrological system, in which the terrestrial recharge area is hydraulically connected with the submarine discharge area (by a confined aquifer, for example). Recently, our hydrogeological modeling suggested that such a system exists in northern Israel. The model predicted the location of a brackish water seepage within the Achziv Submarine Canyon, ~10 km offshore, where the Cretaceous Judea Group confined aquifer is carved by the canyon. The present work is a field study that attempts to identify these brackish seeps in the water column of the canyon at the aquifer exposure. The field observations include salinity and temperature profiling of the water column along the canyon during three cruises and 224Ra measurements of water samples from the canyon. The results point to a significant near-bottom low-salinity and low-temperature anomaly right where the aquifer submarine outcrop is mapped that coincide with a high 224Ra activity anomaly. Such near-bottom anomalies are absent in an adjacent submarine canyon, in which the confined aquifer is not exposed. The anomalies in the water column of the Achziv Submarine Canyon corroborate the results of the hydrogeological modeling that predicted brackish DSGD from the sea bottom at the aquifer outcrop. The possibility of DSGD in specific geo-hydrological settings is relevant for various biological, geochemical, hydrological, and geotechnical studies of the marginal ocean.
|Journal||Journal of Geophysical Research: Oceans|
|State||Published - 1 Jan 2020|
Bibliographical noteFunding Information:
The authors thank the following people for their assistance during the research cruises and after: Yossi Mart, Orit Hyams‐Kaphzan, Yehudit Harlavan, Michael Kittin, Mor Feldman, Avner Amorai, Gilad Amorai, and Inbar Vaknin. To the EcoOcean organization for their support and to the team members: Itay Katzman, Eran Sela, and the Mediterranean Explorer R/V crew. This work was funded by Mediterranean Sea Research Center of Israel (support provided to AP) and by the Israel Science Foundation (Grant 954/15 to OK). Data from this study are available as electronic files in cloud‐based repositories. For access please contact firstname.lastname@example.org .
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