In today’s world, the news about the effects of climate change is unfortunately constant,
with temperatures rising, sea ice melting, and landscapes changing.
There are stories and situations emerging all over the world map. But one recent study takes us deep
into the ocean specifically, where changes are being seen in a unique way.
This is Unveiled, and today we’re answering the extraordinary question;
did scientists just discover that the seafloor is melting?
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Since most of the Earth is covered by ocean, there’s more seafloor on this planet than
there is land above the water’s surface. We’re not exactly familiar with the seafloor because
it’s so inaccessible for us, but it’s really a massive environment. Importantly, it’s not flat
and uniform all over, but is made up of various layers. The parts of seafloor that are nearest the
surface (and land) are called the continental shelf. But, where the shelf drops off, where
the seafloor plummets further below the water, we have what’s called the “abyssal plain”. And then,
in places after that, we move into the very deepest parts of the sea, the oceanic trenches…
the most famous of which is the deepest of all, the Marianas Trench in the Pacific.
Often, if a study of the ocean floor makes the news, it’s to do with exploring an exceptionally
deep trench somewhere. The story of the plastic bag found floating in Challenger Deep at the
bottom of the Marianas Trench, for example, caught international attention. However,
it’s the higher regions, the shelf and the abyssal plain, that we’re interested in
today. At first glance the seafloor here is vast, sandy, and seemingly quite empty…
but, actually, it’s full of diverse wildlife and some unique, sometimes bizarre, conditions.
For example, the wreck of the Titanic lies on the abyssal plain, and the ruined ship itself is now
home to a one-off and rich micro-ecosystem. The continental shelf and the abyssal plain
also hold lots of permafrost, though. Permafrost is permanent frost, as the name would suggest,
located on or under the ground, mostly in the northern hemisphere. On land, the effects of
rising global temperatures on permafrost are well-documented, melting (as it does) to reveal
things that had long ago been frozen and hidden below. The permafrost on the seabed is typically
more difficult to study, however. It’s expensive to take machines down there to remotely drill,
and it requires rare expertise. But in March 2022, a years-long study conducted by
MBARI – the Monterey Bay Aquarium Research Institute – was finally published. The study
involved sending remote submersibles into the deep water of the Canadian Beaufort Sea and taking
regular sonar scans, which produced a map of the seabed’s changing topography. One thing that
scientists soon discovered was that all over the sea floor enormous sinkholes have developed… where
the oceanic permafrost is melting. And they’re developing, potentially, at an alarming rate.
Though the precise cause isn’t completely agreed on, the general reason that melting
permafrost makes craters like these is that, when the ice that was there melts away,
it leaves behind enormous voids… which get filled with sediment falling in from all sides,
which creates a sinkhole. While eye-opening, then, it’s not an unprecedented discovery. We know that
above the waves, on land, similarly huge sinkholes have also formed in the Arctic Circle,
with some of the largest appearing in Siberia. In recent times, this isn’t
unexpected behavior from mother nature. And, interestingly, the study from MBARI,
while it may sound damning, isn’t all bad news. In fact, scientists have stressed that the melting
seabed likely isn’t wholly (or even partly) caused by man-made climate change. What data we have
about the temperatures in the ocean where this permafrost is, reportedly suggests that it hasn’t
really been getting all that warmer down there, in particular. This isn’t thought to be the case
across the entire ocean - where various other studies have found that water temperatures
have notably risen in recent times, with human action to blame - but, in this instance,
there are perhaps other forces at play. The most likely explanation proposed by
those behind the study is that this is a result of long-term, natural climate change. While the
current climate crisis is caused and worsened by human action and pollution, it’s also the case
that Earth has warmed and cooled many times over its 4.5-billion-year lifespan, and only
in this most recent cycle are humans to blame. With this in mind, MBARI says that the melting,
deep-sea permafrost we’re seeing could actually be an effect of Earth exiting the last glacial period
of the last ice age, around 11,000 years ago. The permafrost had formed in the 20,000 years or so up
until that point, and it’s been disappearing ever since - which is the natural course.
Even if humankind wasn’t here, it’s thought that this process would still be happening,
and these sinkholes would still be forming. But, still, it’s the very fact that humanity
DOES exist that makes the situation so potentially worrying. It’s feared that melting permafrost,
even at the bottom of the sea, could affect us by making the planet’s surface in general more
and more unstable. Already, melting permafrost on the ground is a very real danger to the people who
live in the Arctic Circle - which is a difficult enough place to live at the best of times.
But, while some sinkholes have appeared away from built-up areas, others - including, again,
in Siberia - have emerged close to towns and homes. Buildings and infrastructure are at risk,
which is both dangerous and expensive to fix. These things are unpredictable, too,
as it’s difficult to know exactly how big a sinkhole will become or when it will eventually
collapse. And, since most of the Arctic Circle is built on permafrost, it’s an ever-increasing issue
as the Arctic becomes warmer and warmer. Naturally, the sinkholes that form underwater
perhaps aren’t quite so immediately problematic for human populations, but coastlines may
well be affected - which is where many human settlements are based - and the general feeling
that even the bottom of the sea might be failing us is certainly disconcerting.
Especially because permafrost has another crucial function, as well:
to keep methane trapped and out of the atmosphere. Methane is a major greenhouse gas,
so the release of more and more of it by melting permafrost - either in the sea or on land - is bad
news. Before now, scientists have referred to the situation as a “methane time bomb”, but the latest
MBARI study appears to show that offshore, in the deep water, the bomb may be about to go off…
or may have already blown. It’s a problem because while, under ordinary circumstances,
a methane rise triggered by melting permafrost as a natural result of the last ice age ending
wouldn’t perhaps be anything to worry about… when it’s combined with rising levels caused by
other factors (including man-made climate change) it does become a concern.
Finally, though, the simple melting of permafrost isn’t the only thing that’s affecting the shape
of the bottom of the sea at the moment. A 2018 study found that, in some regions, the seafloor is
beginning to strain under the increased weight of water generated by melting ice caps. The pressure
at the bottom of the sea is already immense, but that pressure appears to be going up... and the
entire sea floor could be at risk of sinking, as a result. It’s as though the conditions
far below the waves, and far out of sight for most of us on a daily basis, are pressing in from all
sides. As yet, it’s not clear what the long-term consequences of this will be, and the “weight of
water” issue is held to be an entirely separate concern to the melting permafrost and sinkholes.
The two aren’t, at this stage, thought to be related… but it is another concern, nonetheless.
Clearly, this is an unfolding situation here, with various factors to consider. The ongoing effects
of the end of the last ice age are being seen, measured, and monitored… all while climate change
(natural and manmade) creates a unique set of circumstances. And that’s why scientists,
to some degree, have just discovered that the seafloor is melting.
What do you think? Is there anything we missed? Let us know in the comments, check out these other
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