Expedition | 501

Coastal hydrological systems provide significant freshwater to coastal communities around the world, and the offshore component of these systems is poorly understood. While volumetrically significant, onshore-offshore freshened water is also susceptible to contamination due to rising sea level. To date, we know very little about the dynamics these shoreline-crossing groundwater systems and the age of the water in these systems, and even less about their influence on cycling of nutrients and rare earth elements.

The northeast coast of the United States is perhaps the best understood example of an offshore freshwater system, and multiple studies have been undertaken to determine the origin and volume of offshore freshwater. Coring and sampling the subseafloor offshore Massachusetts, USA, will provide data for understanding the processes driving emplacement of freshwater lenses offshore New England and elsewhere globally, and lead to a better understanding of this worldwide hydrogeological phenomenon. This is essential for protection and sustainable management of offshore freshwater systems and for better understanding biogeochemical and elemental cycling in continental shelf environments.