An Iceberg The Size of a Country Breaks Away, What Happens Next?

A tabular iceberg gets stuck in thin, seasonal sea ice.
A tabular iceberg gets stuck in thin, seasonal sea ice. Mark Brandon, CC BY-NC-SA

You never forget the first time you see an iceberg. The horizon of a ship at sea is a two dimensional space and to see a three dimensional piece of ice appear in the ocean is quite something. But, in truth, the first iceberg you see is likely to be small. Most icebergs that make it far enough north from Antarctica to where they are danger to shipping are sometimes many years old and at the end of their lives. They are small fragments of what once left the continent.

Once in a while, however, a monster breaks free from the edge of Antarctica and drifts away. Tens of kilometres long these bergs can tower perhaps 100 metres above the sea and reach several hundred more below the surface. These are called tabular icebergs – and while it is rare for humans to see something on such a scale they are part of the normal cycle of glacial ice in Antarctica.

Everyone knows Antarctica is an ice-covered continent, but the ice is not static. To a scientist it is a dynamic environment – it’s just a question of the timescale you are looking at. Snow falls on the continent and over time it has built up layers of ice which flow in glaciers towards the coast.

On reaching the sea, these glaciers fracture and release icebergs or form large regions of floating ice known as ice shelves. In a few special places glaciers can extend tens of kilometres into the ocean – giant fingers of ice several hundred metres thick, pointing out into the sea.

Just like a wall they shield what is in their lee, and rather than the ocean being covered by drifting sea ice it can remain open throughout the year to form what is called a polynya. The ocean still freezes, but the ice is constantly pushed away by the prevailing winds. Open water throughout winter helps seals and penguins survive, and stimulates phytoplankton production.

Tracking The Mega Icebergs

A new research article in the journal Nature Communications by a French team working in Antarctica has looked at the history of the polynya in the lee of the Mertz Glacier going back 250 years. This glacier forms one of these fingers of ice reaching out from the continent and the polynya in its lee can be up to 6,000 square kilometres.

The glacier tongue (blue) in summer and winter.
The glacier tongue (blue) in summer and winter. The polynya is shaded yellow. Campagne et al.

What they did was take a core sample of sediment from the sea bed in the lee region (the red star in the above images) and look back in time using climate proxies such as the titanium content – which can be considered a proxy for the how much of the sediment comes from the land.

The proxies tell us which species of plankton dominated the region in a particular period: if the sediment is dominated by species which live in open water then they can infer that the polynya existed and so the Mertz Glacier had a long tongue extending north. If the sediment is dominated by species which live in the sea ice, then the polynya and the glacier tongue were absent. It is quite an elegant way to investigate glacier flow.

mertz tongue A massive iceberg (right) drifts slowly towards the Mertz tongue. Neal Young / Australian Antarctic Division

What they found is that every 70 or so years the Mertz polynya is absent for tens of years. Given that the glacier is advancing about 1 km per year this means a super-iceberg tens of kilometres in length has regularly formed in this region.

These days we can see this happen in almost real time through the amazing access we have to satellite imagery and in February 2010 an iceberg containing almost 900 billion tonnes of fresh water broke free.

What Happens Next?

You may think it would drift north, away from the continent, but icebergs this big don’t have an easy path. They crash and bounce along any relatively shallow region of the sea floor and wipe out anything in their way. Most people know trawling harms the sea floor; imagine the trail of damage 900 billion tonnes of ice scraping on the sea floor can leave.

B-09B collides with the Mertz Glacier Tongue
B-09B collides with the Mertz Glacier Tongue, causing it to break off and form a new iceberg. NASA/Goddard/Jeff Schmaltz

Very large icebergs get identifying codes; this one became C28 as it was the 28th large iceberg from this sector of Antarctica. It took two months for C28 to reach the deep water before it shattered into two pieces (C28A and C28B since you ask) both still massive, and both went on to spawn further icebergs as they fractured into ever smaller pieces over the next few years.

When still close to shore these giant bergs are bad news for penguins, who suddenly have to travel much further – around the iceberg – to find open sea, and their food. Chicks growing up near a massive iceberg may starve and die and some entire colonies may become unviable.

Penguins can make bad life choices too
Penguins can make bad life choices too. David Stanley, CC BY

As they drift away these huge icebergs create their own habitat cooling the seas and freshening the waters, and also seeding the oceans with iron which means more algae and plankton at the bottom of the food chain in remote locations such as South Georgia, where icebergs run aground and die.

Over the past 50 or so years the robust cycle of growth and decay in the Mertz glacier has broken down. The researchers think this is due to large-scale changes in the way the wind circulates over Antarctica – the so-called Southern Annular Mode (SAM). Other studies have shown us that the way the SAM has changed over recent decades has an anthropogenic footprint. It seems even in Antarctica we can identify human impacts on climate processes that are likely to have been operating for thousands of years.

The ConversationThis article was originally published on The Conversation.
Read the original article.

About The Author

Mark Brandon is a Reader in Polar Oceanography at The Open UniversityMark Brandon is a Reader in Polar Oceanography at The Open University. He is a polar oceanographer interested in the interaction of the ocean with the cryosphere, and has currently published more than 30 research articles in this area. He is a member of the NERC Peer Review College, and has sat on many grant panels acting as Vice Chair on many occasions. He was also co-chair of the NERC Ice Sheet Stability Expert Group with Professor Tony Payne (Bristol).

Related Book:

InnerSelf Market

Amazon

enafarzh-CNzh-TWdanltlfifrdeiwhihuiditjakomsnofaplptruesswsvthtrukurvi

follow InnerSelf on

facebook icontwitter iconyoutube iconinstagram iconpintrest iconrss icon

 Get The Latest By Email

Weekly Magazine Daily Inspiration

LATEST VIDEOS

The Great Climate Migration Has Begun
The Great Climate Migration Has Begun
by Super User
The climate crisis is forcing thousands around the world to flee as their homes become increasingly uninhabitable.
The Last Ice Age Tells Us Why We Need To Care About A 2℃ Change In Temperature
The Last Ice Age Tells Us Why We Need To Care About A 2℃ Change In Temperature
by Alan N Williams, et al
The latest report from the Intergovernmental Panel on Climate Change (IPCC) states that without a substantial decrease…
Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get?
Earth Has Stayed Habitable For Billions Of Years – Exactly How Lucky Did We Get?
by Toby Tyrrell
It took evolution 3 or 4 billion years to produce Homo sapiens. If the climate had completely failed just once in that…
How Mapping The Weather 12,000 Years Ago Can Help Predict Future Climate Change
How Mapping The Weather 12,000 Years Ago Can Help Predict Future Climate Change
by Brice Rea
The end of the last ice age, around 12,000 years ago, was characterised by a final cold phase called the Younger Dryas.…
The Caspian Sea Is Set To Fall By 9 Metres Or More This Century
The Caspian Sea Is Set To Fall By 9 Metres Or More This Century
by Frank Wesselingh and Matteo Lattuada
Imagine you are on the coast, looking out to sea. In front of you lies 100 metres of barren sand that looks like a…
Venus Was Once More Earth-like, But Climate Change Made It Uninhabitable
Venus Was Once More Earth-like, But Climate Change Made It Uninhabitable
by Richard Ernst
We can learn a lot about climate change from Venus, our sister planet. Venus currently has a surface temperature of…
Five Climate Disbeliefs: A Crash Course In Climate Misinformation
The Five Climate Disbeliefs: A Crash Course In Climate Misinformation
by John Cook
This video is a crash course in climate misinformation, summarizing the key arguments used to cast doubt on the reality…
The Arctic Hasn't Been This Warm For 3 Million Years and That Means Big Changes For The Planet
The Arctic Hasn't Been This Warm For 3 Million Years and That Means Big Changes For The Planet
by Julie Brigham-Grette and Steve Petsch
Every year, sea ice cover in the Arctic Ocean shrinks to a low point in mid-September. This year it measures just 1.44…

LATEST ARTICLES

green energy2 3
Four Green Hydrogen Opportunities for the Midwest
by Christian Tae
To avert a climate crisis, the Midwest, like the rest of the country, will need to fully decarbonize its economy by…
ug83qrfw
Major Barrier to Demand Response Needs to End
by John Moore, On Earth
If federal regulators do the right thing, electricity customers across the Midwest may soon be able to earn money while…
trees to plant for climate2
Plant These Trees To Improve City Life
by Mike Williams-Rice
A new study establishes live oaks and American sycamores as champions among 17 “super trees” that will help make cities…
north sea sea bed
Why We Must Understand Seabed Geology To Harness The Winds
by Natasha Barlow, Associate Professor of Quaternary Environmental Change, University of Leeds
For any country blessed with easy access to the shallow and windy North Sea, offshore wind will be key to meeting net…
3 wildfire lessons for forest towns as Dixie Fire destroys historic Greenville, California
3 wildfire lessons for forest towns as Dixie Fire destroys historic Greenville, California
by Bart Johnson, Professor of Landscape Architecture, University of Oregon
A wildfire burning in hot, dry mountain forest swept through the Gold Rush town of Greenville, California, on Aug. 4,…
China Can Meet Energy and Climate Goals Capping Coal Power
China Can Meet Energy and Climate Goals Capping Coal Power
by Alvin Lin
At the Leader’s Climate Summit in April, Xi Jinping pledged that China will “strictly control coal-fired power…
Blue water surrounded by dead white grass
Map tracks 30 years of extreme snowmelt across US
by Mikayla Mace-Arizona
A new map of extreme snowmelt events over the last 30 years clarifies the processes that drive rapid melting.
A plane drops red fire retardant on to a forest fire as firefighters parked along a road look up into the orange sky
Model predicts 10-year burst of wildfire, then gradual decline
by Hannah Hickey-U. Washington
A look at the long-term future of wildfires predicts an initial roughly decade-long burst of wildfire activity,…

 Get The Latest By Email

Weekly Magazine Daily Inspiration

New Attitudes - New Possibilities

InnerSelf.comClimateImpactNews.com | InnerPower.net
MightyNatural.com | WholisticPolitics.com | InnerSelf Market
Copyright ©1985 - 2021 InnerSelf Publications. All Rights Reserved.