As the climate changes, more and more warm seawater reaches the glaciers of Antarctica and threatens them to collapse. A group of researchers explores how feasible the idea is to block channels that bring warm water to the glaciers with flexible buoyant curtains, anchored to the seabed. Their study has now been published in the open access journal PNAS Nexus.

The possible collapse of the West Antarctic Ice Sheet
is one of the most dramatic impacts of climate warming. Currently, floating ice
shelves hold the ice sheet in place. But the Thwaites and Pine Island Glaciers in
Antarctica are rapidly thinning and retreating as deep salty seawater warmed by
climate change licks at the undersides of their leading edges.

–
Once started, and there is evidence that it has already, a collapse cannot be
stopped by reducing greenhouse gas emissions, says John Moore, researcher at the
Arctic Centre at the University of Lapland in Rovaniemi and the Beijing Normal
University in China.

– The sea level will rise several meters
over the next few centuries and force the largest migration in human history away
from the coasts, Moore adds. Given the slow and limited response of sea level to
emissions control, Moore and his team came up with an alternative method to
stabilize the ice sheets.

Naturally, the waters around Antarctica
have an upper layer of relatively cold and fresher water on top of a warmer, higher
salinity layer beneath. Moore and his colleagues examine how to physically block the
warm water from reaching Antarctica. The way to do it: partially blocking deep
seabed channels that guide warm seawater.

– A couple of us
glaciologists independently noticed how seabed sills and high points naturally keep
warm waters away from the ice edge, so it seemed natural to raise the sea floor.
Then Bowie Keefer, an engineer from Canada, told us much cleverer ways to do it by
using curtains, Moore explains.

The curtains would be around 100
meters high, deployed as many in narrow sections, so that they block the stream in
the lower layer but allow the outflow of nutrient-rich waters from the glaciers.
Additionally, the curtains need to be flexible so that icebergs push them aside as
they move past, rather than destroy them.

With warm water access
reduced, the ice would thicken and reground on the seafloor to securely support the
vulnerable parts of the West Antarctica ice sheet. The authors estimate that the
installation of these curtains would cost 40 to 80 billion dollars and requires one
to two billion dollars per year in maintenance.

– This might
sound like a lot of money but doing nothing would be far more expensive. By 2100,
building and maintaining coastal protection is expected to cost around 40 billion
dollars per year for every meter of sea level rise, and such adaptation is far
harder for the Developing World than in the wealthy countries that have caused
global heating, Moore points out.

Seabed
curtain schematic (not to scale). A) Exchange flow over the curtain. Front view of a
single curtain panel with buoyancy concentrated at the top, B), or distributed along
the height (C) showing how the curtain panels could be pivoted to allow transverse
sway. Sets of panels (D) joined to make a long curtain with overlapping front and
back rows to accommodate locally varying forces.

Studies in Greenland could provide important
insights

Before the method can be
applied to Antarctica, there is much research to be done: on governance, ecology,
engineering, and glacier oceanography. An 80 km long Antarctic curtain would be the
most challenging engineering project ever attempted. So, engineers and
oceanographers have much to learn in more accessible places. Moore and his team are
exploring if shorter curtains in key Greenland fjords make any sense. The Greenland
ice sheet faces the same problem as Antarctica but is already much warmer, and
fishing and hunting ways of life are rapidly changing.

–
Greenlanders we work with find some positives in the intervention idea – it empowers
local peoples and raises global awareness of their stewardship of this vital global
good. But any intervention must be done as a co-design with local people in the
Arctic – it’s their choice in the end, and must benefit them as well as the globe,
Moore says.

In October 2022, Moore and his colleagues were able
to discuss their ideas at a meeting in Reykjavik with several rightsholders as well
as engineering companies and leading scientists in several fields.

– These discussions were a great beginning. There are a lot more people
wanting to get involved, which is crucial for simulating potential impacts of doing
any interventions, and exploring ways of financing and governing, says
Moore.

The next steps include setting up an advisory committee to
represent both local and international expertise and interests and identify gaps in
knowledge and focus areas of intensive research.

– It will take
at least a decade, maybe two before any intervention is built in Antarctica, moving
a step at a time up in scales and difficulty as we go. We still have time to act,
but the research is enormously challenging, and it must start now, Moore points
out.

Article
Feasibility of ice sheet conservation using seabed anchored curtains was
published by Bowie Keefer, Michael Wolovick, and John C. Moore in PNAS Nexus on
28.03.2023.

More
information:
Research Professor John Moore, Arctic
Centre, University of Lapland, john.moore(at)ulapland.fi;
john.moore.bnu(at)gmail.com, +358 400 194 850