Artificial wall under ice sheets could prevent glaciers from melting

The
Thwaites Glacier in Antarctica is seen from
above.
NASA

• If the glaciers holding back
  ice sheets in Antarctica and Greenland were to collapse,
  sea level rise rates around the globe would skyrocket.
• This would
  quickly render the coastal cities where hundreds of
  millions of people live uninhabitable.
• To prevent this, scientists are proposing a new kind of
  geoengineering
  plan to prop up the ice sheets with mounds or walls underneath.
• These would be the biggest civil engineering projects in
  human history.

For the hundreds of millions of people who live alongside the
world’s coasts, the scariest sea-level rise scenario is the idea
that ice sheets could collapse.

Seas are already
rising rapidly, threatening to
swamp cities like Miami within the lifetimes of people
alive today. If the sheets of ice that sit on top of Antarctica
and Greenland were to collapse, the rate of sea level rise could
skyrocket, making coastal cities uninhabitable and destroying
trillions of dollars of property and infrastructure.

To prevent or slow these floods from washing over cities,
humanity may need to embark on the biggest civil engineering
project in human history, according to a
study published Thursday in the European Geosciences Union
journal The Cryosphere. The project: building massive walls under
the ice sheets to stop them from falling apart.

It would be a geoengineering effort — a way of reworking our
planet — that might buy time for coastal areas to adapt and
for humanity to reverse some of the warming we’ve caused by
burning fossil fuels and changing the climate.

“Doing geoengineering means often considering the unthinkable,”
said John Moore, one of two authors of the new study and a
climate scientist at Beijin Normal University and Finland’s
University of Lapland Arctic Centre,
in a statement.

The project is still theoretical. This sort of “ice sheet
intervention today would be at the edge of human capabilities,”
the authors wrote in the study. But it’s possible that
catastrophic ice sheet collapse could happen in the foreseeable
future, and the processes that could trigger it at the Thwaites
Glacier in West Antarctica — one of the most vulnerable
glaciers — could already be happening.

“Thwaites could easily trigger a runaway [West Antarctic] ice
sheet collapse that would ultimately raise global sea level by
about 3 metres,” Michael Wolovick, a geosciences researcher at
Princeton and the other author of the study, said in a statement.

Crevasses
near the grounding line of Pine Island Glacier,
Antarctica.
Ian Joughin, University of
Washington

Predicting collapse

There’s enough ice stacked on top of Antarctica to raise
seas around the globe by almost 200 feet. While it takes time for
major changes to occur with that much ice, Antarctica is melting
faster than we thought, according to a 
study
published in June in the journal Nature
.

While it would take thousands of years for seas to change
by hundreds of feet, people have already caused seas to start
rising.

In the 20th century, sea levels around the globe rose about six
inches on average, Michael Oppenheimer, a professor of
geosciences at Princeton, said during a media briefing earlier
this year on sea level rise. That was enough to narrow the
typical East Coast beach by about 50 feet.

Since the mid-1990s, places
like Miami have seen an additional five
inches of sea level rise. Seas rise faster
in some places than others, due to ocean currents and the effects
of gravity.

Several factors contribute to global sea level rise. As the
world has warmed due to the burning of fossil fuels, oceans have
absorbed the majority of the heat. Warmer water expands, which
takes up more space.

Glaciers are also melting, adding more water to the system.
The final factor is melting from ice sheets in Antarctica and
Greenland that are still protected by glaciers.

Over
the course of several years, turbulent water overflow from a
large melt lake carved this 60-foot deep
canyon.

Ian
Joughin

Propping up the ice

According to the recent study, we could try to build up support
structures or even walls underneath the ice sheets to prevent
them from breaking apart or being weakened by the influx of warm
water from below. 

Wolovick and Moore have been researching this concept for

several years now. In their new study, they calculated how
likely it would be that ice sheet engineering could avoid the
collapse of the Thwaites Glacier. It’s an especially challenging
glacier because of its extreme width, which means it would need a
large support structure.

The first method of propping up the glacier modeled by the study
authors is sticking a series of thousand-foot mounds underneath
it. While this wouldn’t block warm water from flowing beneath the
ice, the mounds would help support the glacier, making collapse
less likely and giving it a chance to regrow.

Even this “simpler” method would be a massive undertaking —
“comparable to the largest civil engineering projects that
humanity has ever attempted,” the authors wrote, like digging the
Suez Canal but in a much harsher environment.

The authors calculated that this approach would have a 30% chance
of preventing the collapse of the Thwaites Glacier — which could
trigger the loss of the West Antarctic Ice Sheet — for the next
1,000 years.

The more complex approach would be to build an actual wall
underneath the glacier, potentially stopping the influx of half
of the warm flowing water. Such a project would have a 70% chance
of success over the next 1,000 years, the authors wrote. But it
would be far more difficult to pull off.

Yet without dealing with
the emissions problem, climate change will
continue.
Reuters/Alexander
Gerst/NASA

Not a total solution

Aside from the technical difficulties involved with conducting
the biggest engineering project the world has ever seen, there
are other concerns about attempting this.

The study authors worry that fossil fuel interests could use the
idea that there is an engineering solution to sea level rise as
an argument in favor of continuing to pump greenhouse gases into
the atmosphere.

But unlike other proposed geoengineering solutions, such as the

idea that we could block out some of the sun’s light to stave off
warming, this solution is focused only on one of the
consequences of climate change.

In other words, it might help lessen some of the negative effects
of sea level rise, but the other effects of climate change would
continue unabated. These include drought, ocean acidification,
intense storms, and searing heat waves.

Plus, as the world warms, these glaciers will continue to melt
and proceed towards collapse, even if they are propped up from
below.

“The more carbon we emit, the less likely it becomes that the ice
sheets will survive in the long term at anything close to their
present volume,” Wolovick said.