Scientists Launching Drilling Expedition To Find Freshwater Beneath The Ocean Floor Off Nantucket

A team of international scientists will soon begin drilling beneath the sea floor off Nantucket in search of a vast freshwater aquifer that it not only believes exists, but could one day be tapped and used by humans.

Decades in the making, the research project will be the first of its kind in the world and will be conducted just a few miles southwest of the island where researchers will drill to depths of 1,600 feet to locate the freshwater believed to be there in potentially large quantities beneath the sea floor.

"I'm just excited about the science, and that finally, after all these years, someone's trying to get the truth," said Nantucket Water Department director Mark Willett. "Computers predicted it. Everybody thinks it's there. These guys are the first ones in the world who are going to go drill a hole and prove it."

The guys Willett is referring are the team members of the International Ocean Drilling Programme, led by Professor Brandon Dugan, the expedition's co-chief scientist and the associate department head for geophysics at the Colorado School of Mines.

Dugan was on Nantucket this week to brief Willett and others about the project - officially called the New England Shelf Hydrogeology Expedition - that will begin on May 1. By that date, a massive offshore rig known as Liftboat Robert will move into position off Nantucket and the drilling will begin. The team will be using some of the same tactics and equipment as those used for offshore oil and gas exploration, but instead of petroleum, it hopes to be extracting fresh water.

Willett and Dugan are particularly intrigued by the possibility that the offshore freshwater aquifer could be connected to a lower, untapped aquifer beneath Nantucket that Willett calls "ancient glacier lake Nantucket."

"If it is connected and it's young water that's being recharged actively today, that's really exciting, because it's a renewable source," Dugan said. "Our goal would be to provide the science and what we know about the system, and then the people who live there and are here year-round making all these decisions, it would be up to you to decide what to do. Sometimes the answer might be tomorrow, and sometimes the answer might be not for 10 years."

The expedition will focus on learning as much as possible about the offshore groundwater system, including its nature, extent, renewability, and quality of the water - specifically its salinity. The $26 million project - which includes 29 scientists representing 13 different countries - is being funded by the International Ocean Drilling Programme as well as the U.S. National Science Foundation.

"Our goal is to understand the quantity, the quality, and the origin of the water and then really share that with the people who would make those decisions" about its use, Dugan said. "It would be Nantucket, it would be your governing agencies, which would think about how - if we found out that it was fresh - it could be used for something."

The existence of sub-seafloor groundwater systems was first revealed during previous surveys by the U.S. Geological Survey's Atlantic Margin Coring project, which failed to discover petroleum but did provide evidence of freshwater deposits beneath the sea floor.

Over the three-month expedition, the New England Shelf Hydrogeology team will drill in three locations to collect water and sediment samples to gain a better understanding of the offshore aquifers. The wells that are drilled will "close naturally and reseal the aquifer," according to project leaders.

"We hypothesize that freshened water may exist in confined aquifers extending to 30 miles from the Cape and Islands," the group states. "The expedition also aims to understand the role that sea-level change and glaciation may have played over tens-to-thousands of years in charging these offshore aquifers with freshened/slightly saline water."

It also aims to answer the following "key scientific questions":

• What is the distribution of freshwater, fluid pressures, and temperatures across the New England Atlantic continental shelf?
• How old is the groundwater, and when was emplaced?
• Was freshwater recharged by basal melting of ice sheets, infiltration from proglacial lakes, and/or direct recharge from precipitation?
• Do fluid pressures reflect equilibriam conditions or are overpressuring mechanisms involved?
• What are the current concentrations, production/ consumption rates, and cycling of methane, nutrients, and rare Earth elements in shelf sediments?
• What are the rates of decomposition of sedimentary organic matter and which redox processes/microbial communities are involved?
• What are the magnitudes of long-term fluxes of methane and nutrients from the shelf due to periodic flushing during the Pleistocene?
• Does the emplacement of ice sheet meltwaters an confined aquifers create a unique environment for methane?
• What is the sea-level history along this glaciated margin?