Scientists recently discovered a massive aquifer of freshwater hidden from view just off the US coast. The freshwater extends from Southern New Jersey to Massachusetts and has sat undisturbed since the last Ice Age.

While the vast size of this massive cache is surprising, it’s not entirely unexpected. Signals of the water first showed up in the 1970s, when companies drilling off the coast searching for oil sometimes hit freshwater instead. But it wasn’t clear whether these freshwater deposits were isolated pockets or whether they covered a larger expanse.

“We knew there was fresh water down there in isolated places, but we did not know the extent or geometry,” said lead author Chloe Gustafson.

The yellow hatched area shows where the giant aquifer is hiding off the coast of New England.

Credit: Gustafson et al., 2019; CC BY 4.0

This water isn’t young, either. The researchers said they suspect that much of it is from the last ice age.

HOW DID ALL THAT FRESH WATER END UP UNDER THE OCEAN?

The aquifer likely came into being at the end of the last ice age, the researchers said. About 20,000 to 25,000 years ago, much of the world’s water was locked up in glaciers, making sea levels lower than they are now. As temperatures rose and the ice covering the U.S. Northeast melted, water washed away huge quantities of sediments, which formed river deltas on the still-exposed continental shelf. Large pockets of fresh water from the melted glaciers then got stuck in these sediment traps. Later, sea levels rose, trapping the sediment and fresh water under the ocean.

However today, it appears that the aquifer isn’t stagnant. Rather, it’s likely fed by subterranean run-off from the land. This water is then likely pumped seaward by the rising and falling pressure of the tides.

This conceptual model shows how offshore groundwater feeds the aquifer.

Credit: Gustafson et al., 2019; CC BY 4.0

The aquifer is purest close to shore and gets saltier farther out, indicating that it is slowly mixing with seawater. The freshwater near land is about 1-part-per-thousand salt, much like other terrestrial fresh water. In contrast, by the aquifer’s outer edges, it’s about 15 parts per thousand, which is still lower than typical seawater’s level of 35 parts per thousand.

In other words, this water would have to be desalinated before it can be used, but costwise it would still be cheaper to process than regular salt water.

“We probably don’t need to do that in this region, but if we can show there are large aquifers in other regions, that might potentially represent a resource,” Kerry Key a geophysicist said in a statement.

Scientists from Columbia University’s Lamont-Doherty Earth Observatory published their research on the topic in the journal Scientific Reports. The research team used electromagnetic sensors towed behind a research ship to measure the difference in conductivity in the water below. Salt water is much more conductive than freshwater and thus the research team was looking for areas of low conductance.

Source of article: Forbes & Live Science

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