Global Warming Could Make Our Beaches Saltier

Christopher Hollis via Wikimedia Commons // CC BY 2.5
Christopher Hollis via Wikimedia Commons // CC BY 2.5 / Christopher Hollis via Wikimedia Commons // CC BY 2.5

It seems like every week now, we’re learning about some new and unexpected consequence of environmental upheaval. The latest comes from a beach in Delaware, where researchers say global warming has made the shore saltier. They published their findings in the journal Scientific Reports.

Peaceful as the beach may seem to us, it’s actually a well-oiled natural machine with a lot of moving parts. Elements like water quality, climate, erosion, pollution, and wildlife are all connected. As in any ecosystem, changes in one piece affect the others.

Scientists from the New Jersey Institute of Technology's Center for Natural Resources Development (CNRDP) wanted to check in on the salinity of our beaches. They focused their attention on the littoral, or intertidal zone—the stretch of sand between high and low tide points. This part of the beach is prime territory not only for small children with toy shovels and buckets, but also for crabs, mussels, anemones, shorebirds, and seaweed.

Co-author and coastal geologist Nancy Jackson traveled to Slaughter Beach in Delaware, where she collected almost 400 sand samples over the course of a month, capturing physical snapshots of the littoral zone at every point in the tidal cycle.

Jackson and her colleagues Xiaolong Geng and Michel Boufadel then measured the chemical composition of the seawater and the water trapped between the grains of sand, also known as the pore water.

They found that seawater near the beach had salt concentrations of 25 grams per liter (g/L). They expected to find similar or lower concentrations in the pore water, since the sand this high up the beach is also washed with groundwater from inland. Instead, they found that pore water in the top of the intertidal zone was much, much saltier, with concentrations of 60 to 100 grams of salt per liter of water.

The researchers say these high numbers have likely been caused by a rise in evaporation. As beach temperatures rise, evaporation intensifies, leaving behind more salt in less water—a change that could have big consequences for the plants and animals that live there.

"Evaporation is an important driver of underground water flow and salinity gradients, and animals such as mussels and crabs are affected by changes in salinity," Geng said in a press statement. "If the concentrations are too high or too low, they will move away."

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