Tracking the Flow

WHOI scientist Matt Charette and his students travel around the world studying groundwater flow to the ocean from various types of aquifers. Here, he checks the salinity of groundwater samples collected from seeps at Akumal Bay, Mexico. The samples are being filtered through cartridges that remove radium, a naturally-occurring isotope that occurs at very low levels in the environment, but is much more abundant in groundwater than in seawater. That difference makes it a good tracer for estimating the rate of groundwater flow into coastal waters.(Photo by Meagan Gonneea, Woods Hole Oceanographic Institution)