29/11/2020

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Almost Alien: Antarctic Subglacial Lakes are Cold, Dark and Full of Secrets

Getting water samples from an Antarctic lake under 800 meters of ice takes days of
drilling, precise equipment, lots of patience and an eagerness to understand one of
the world’s most extreme environments.

More than half of the planet’s fresh water is in Antarctica. While most of it is frozen
in the ice sheets, underneath the ice pools and streams of water flow into one another
and into the Southern Ocean surrounding the continent. Understanding the movement
of this water, and what is dissolved in it as solutes, reveals how carbon and nutrients
from the land may support life in the coastal ocean.

Gathering data on the biogeochemistry of these systems is an undertaking of Antarctic
proportions. Trista Vick-Majors, assistant professor of Biological Sciences at Michigan
Technological University, is part of a team that gathered samples from the Whillans
Subglacial Lake in West Antarctica and is lead author on a paper about the lake, recently
published in Global Biogeochemical Cycles.

“Life is tough — it can handle a lot,” Vick-Majors said. “This paper is putting together
what we know about the biology and how active it is under Antarctic ice with information
about the composition of organic carbon in the lake.”

Life on a Carbon Budget

Life beneath the ice puts up with a lot — there is no sunlight and pressure from the
ice above in combination with heat radiating up from the Earth’s core melts the water
to form the lake, so the temperature hovers just below freezing. Organic carbon, an
important food source for microorganisms, is present in relatively high concentrations
in Whillans Subglacial Lake, even if it lacks the verdant mess of a Midwest pond in
late August. Instead, as cameras dropped down the borehole of Mercer Subglacial Lake
(a neighbor of Whillans) reveal, the subglacial lake is dark, cold, full of soft and
fluffy sediment, and lined with bubble-filled ice.

A Glimpse of Mercer Subglacial Lake – SALSA Science Team

Mercer Lake is another subglacial lake in West Antarctica and the videographers on
the Subglacial Antarctic Lakes Scientific Access (SALSA) project were able to get
a glimpse of its turbid depths. Credit: Kathy Kasic and Billy Collins/SALSA

The lake bed looks more alien than earth. Studying extreme environments provides insight
into what extraterrestrial life could be like or how earthly life might survive in
similar conditions. Not that humans, penguins or fish could handle it; life in the
waters beneath Antarctica’s ice is mostly microbial. They still show signs of life
— organic carbon and other chemical byproducts of living, eating, excreting and dying
— that Vick-Majors and her team can measure and budget.

seen through through the glass roof of a mobile lab, a researcher works on gathering samples
Trista Vick-Majors wears a Tyvek suit to keep water samples and equipment clean during
its 800-meter dive into Whillans Subglacial Lake. Credit: JT Thomas 

Using mass balance calculations, the team’s research shows that a pool of dissolved
organic carbon in the Whillans Subglacial Lake can be produced in 4.8 to 11.9 years.
As the lake fills and drains, which takes about the same amount of time, all those
nutrients slip and slide their way to the ice-covered coast of the Southern Ocean.
Based on the team’s calculations, the subglacial lakes in the region provide 5,400%
more organic carbon than what microbial life in the ice-covered ocean downstream needs
to survive.

“There’s no photosynthesis under the ice in the ocean downstream of this lake — this
limits the available food and energy sources in a way that you wouldn’t find in a
surface lake or the open ocean,” Vick-Majors said. “The idea is that these subglacial
lakes that are upstream could provide important sources of energy and nutrients for
things living in the ice-covered regions of the Southern Ocean.”

Drilling for Data

While the Whillans Subglacial Lake on its own indicates that upstream nutrients may
be an important factor, it is only a single source of data in an ice-covered complex
of underground lakes, streams and estuary-like mixing zones that undergo seasonal
and sporadic fluxes.

To expand their view, Vick-Majors and the rest of the team have been gathering data
at other sites (Mercer Subglacial Lake was sampled by the SALSA team in early 2019), and doing so is no small feat. They make it happen with a hot water
drill, a specially designed hose, a 10-liter water sampling bottle, some sediment
coring devices, and a week of summery polar weather that can plunge to 20 below. The
crew wears Tyvek suits and all equipment is thoroughly cleaned. They also filter the
drilling water, run it past several banks of ultra-violet lights to knock down microbial
contamination, and then heat it up to use the hot water to open an approximately 1000-meter
borehole down to the lake.

Subglacial Secrets diagram, including details on more than 800 meters down, 60 centimeters wide, 2 hours to sample water, 24 hours to drill borehole
Labs under Antarctica: Researchers work in mobile facilities and use filtered and
decontaminated hot water to drill down nearly a kilometer under the ice. 

“Some of that melted ice water, which has now circulated through the drill, is removed
from the hole so that when the lake is punctured, water from the lake moves up into
the borehole,” Vick-Majors said, explaining that the crew has to keep the hot water
from the drill separate from the lake water to keep their samples and the lake clean.
“It takes about 24 hours to drill the borehole and we keep it open for a few days;
gathering a single sample or letting down the cameras can take two hours or more,
depending on the equipment.”

And the hole keeps trying to refreeze. Plus, Vick-Majors is not a lone scientist;
she is embedded in an interdisciplinary team and everyone needs access to the borehole
for different experiments. But for all the tight logistics and cold toes, she says
it’s worth it.

“There is water and there is life under the ice,” Vick-Majors said. “These can teach
us a lot about our planet because this is a great place to look at somewhat simplified
ecosystems, without higher levels of organisms. So we can answer questions about life
that can be really hard to answer in other places.”

The flip side is that physical-biological interactions can be still be complicated
in these environments; the paper is step towards understanding them. The almost otherworldly
subglacial lakes of West Antarctica grant insight into the possibilities for exoplanet
environments while revealing the deep, water-kept secrets of our own world.

Michigan Technological University is a public research university, home to more than
7,000 students from 54 countries. Founded in 1885, the University offers more than
120 undergraduate and graduate degree programs in science and technology, engineering,
forestry, business and economics, health professions, humanities, mathematics, and
social sciences. Our campus in Michigan’s Upper Peninsula overlooks the Keweenaw Waterway
and is just a few miles from Lake Superior.