International experiment on Submarine Groundwater Discharge

Graduate student Aaron Beck in Mallorca

Principal Investigators: Henry Bokuniewicz

Funded by UNESCO and the IAEA

Students Supported: Aaron Beck (Ph.D.), Ruth Coffey (Ph.D.), John Rapaglia (Ph.D.)

Project Description: While the major rivers of the world are reasonably well gauged, it remains very difficult to evaluate the contribution of submarine groundwater discharge (SGD) into the ocean to marine geochemical budgets, in part because SGD is inherently difficult to measure. In order to develop the scientific and technical knowledge to address this issue more comprehensively, intercomparison experiments have been carried out in different coastal environments including coastal plains, fractured rock, glacial deposits and karst. At each location, three classes of observations were made: geophysical techniques, the application of radioactive tracers and point measurements directly on the seafloor using vented benthic chambers. All of these provide valid, but different, representations of SGD, not only integrating different temporal and spatial scales, but also determine different components of SGD, such as freshwater discharge versus recirculated seawater. We have come to expect that SGD is ubiquitous. SGD often shows complex spatial distributions resulting from the variability of the properties of coastal aquifers and of seafloor sediments. Multiple approaches will be required to establish the total SGD accurately in a local environment.

Field work in Ubatuba, Brazil

Graduate student John Rapaglia in the Mauritius