New clues shed light on the importance of Earth’s ice sheets

Researchers who examined subglacial waters from both Antarctica and Greenland found that these waters have higher concentrations of important life-sustaining elements than previously thought, answering a big unknown for scientists trying to understand the geochemical processes of the Earth.

“The data from an Antarctic lake is particularly interesting,” said Jon Hawkings, a postdoctoral fellow at Florida State University. “Most people tend to think of Antarctica as ice only, but we have known about these lakes under glaciers in Antarctica for 40 years and over 400 of them have currently been identified. Some scientists refer to the subglacial environment in Antarctica as the world’s largest wetland. The challenge for scientists is that it is extremely difficult to sample them. “

Hawkings, along with colleagues from Florida State and Montana State University, released a new study this week on Proceedings of the National Academy of Sciences exploring these subglacial waters.

The study specifically examines liquid water under ice sheets in Antarctica and Greenland. About 10% of the earth’s surface is covered by these ice sheets, and these polar environments are undergoing rapid changes due to rising temperatures. Scientists are very interested in understanding these environments and how continuous warming will affect critical geochemical processes in the future.

Hawkings analyzed the water samples focusing on what are called trace elements, chemical elements that are present in extremely small quantities but which are essential for microscopic organisms and therefore the global carbon cycle. Scientists have thought for years that the waters beneath glaciers around the world contain these elements in such minute quantities that they do not play a significant role in the geochemical and biological processes of the Earth.

“What we found is that ice sheets are actually apparently more important to life processes than we initially thought,” said Robert Spencer, Associate Professor of Earth, Ocean and Atmospheric Sciences at FSU. “As major unknowns are discovered in our contemporary understanding of how our planet works, it reminds us of how much there is still to learn.”

For example, scientists expected to see less than 5 micrograms per liter of dissolved iron (an extremely important trace element) in some of these subglacial waters, but they saw up to 1,000 micrograms per liter. These large variations can make a big difference in the amount of life that can be sustained in extreme subglacial ecosystems and ocean waters that receive ice sheet meltwater.

“These trace elements are a lot like the vitamin tablets that people take every day,” Spencer said. “Even if we only need small amounts of these materials, they are essential for the development of healthy ecosystems.”

Collecting subglacial waters for analysis is no easy feat, especially in Antarctica. Researchers have to work in remote and difficult environments.

Hawkings and Spencer collaborators of Montana State University, Professors John Priscu and Mark Skidmore, orchestrated a logistically complicated research expedition to Antarctica to drill more than 3,500 feet through the Antarctic ice sheet.

After receiving funding from the National Science Foundation in 2016 for the Subglacial Antarctic Lakes Scientific Access (SALSA) project, Priscu spearheaded a field campaign that involved moving nearly 1 million pounds of gear by planes and tractors across the ice cap to the camp site.

Then, from December 2018 to January 2019, the SALSA project’s science team drilled about three-quarters of a mile of ice in Subglacial Lake Mercer, a lake more than 5.5 miles (9 kilometers) long and 50 feet (15 meters) deep. . They chose that particular lake because it was located where two streams meet.

“We were interested in the physical, chemical and biological processes that occur in that specific lake, but then there is also this broader context of these lakes that are part of the larger hydrological system beneath the ice sheet,” Skidmore said. “We want to see what is generated under the ice sheet and how it relates to coastal environments.”

Skidmore took samples according to a protocol Hawkings established and then shipped them back to the United States via a temperature-controlled merchant ship, taking several months, and then forwarded to Tallahassee via overnight delivery in special coolers to keep the sample temperatures stable.

Hawkings and colleagues separately collected samples in Greenland from a large meltwater river that emerged below the Leverett Glacier. The fieldwork, led by Jemma Wadham of the University of Bristol in the UK, involved monitoring the river’s hydrological and geochemical characteristics over a three-month period during the summer melt season.

Hawkings and Spencer then conducted geochemical analyzes in specially designed laboratories at FSU’s National High Magnetic Field Laboratory that minimize dust or other environmental factors that could potentially contaminate the samples.

The researchers said their collaborative resources and interdisciplinary approach ultimately led to a study that will advance their field.

“Discoveries are made at the intersection of disciplines,” Priscu said. “The PNAS the card intersects many disciplines and shows the power of international collaboration. The results of this manuscript have transformed our view of how the polar ice caps affect the Earth System. ”