During a spectacular cruise in 2017 onboard RV “G.O. Sars” a CAGE team of scientists discovered a new cold seep from the Lofoten-Vesterålen margin (Norwegian Sea). This summer, the team is back at the site and will try to find more evidence for the ultimate driver for this cold seep.
Text: Jochen Knies
With the help of Remotely Operating Vehicle (ROV) “Ægir 6000” the team found a biomass-rich, chemosynthesis-based community in ca. 800 m water depth, far from light-dependent photosynthetic marine productivity (see Sen et al. 2019). The ultimate driver for the formation of these organisms remains unclear. However, the team discovered that submarine groundwater discharge is closely associated with the occurrence of chemosynthetic organisms (Hong et al. 2019). This freshwater seepage is likely coupled to the outcropping, highly porous sandstone of the Eocene age that acts as a potential aquifer for the freshwater. Dating of methane-derived authigenic carbonates precipitated around the cold seep shows that the freshwater accumulation in the sub-seafloor is an inherited product of the collapsing ice sheet once covered the nearby landmasses in NW Europe during the last ice age.
From the 06th to 13th of June, the CAGE team will have another opportunity to chase this freshwater onboard RV “G.O. Sars” with ROV Ægir 6000. The goal is to inspect more sites along the Lofoten-Vesterålen margin to see whether the freshwater discharge is more widespread along the margin and can indeed be traced back to the former ice sheet.