There's a giant crack in an Antarctic ice shelf. Should we be worried?

February 24, 2017 by Thea Singer, Northeastern University
The crack in an Antarctic ice shelf continues to grow, and scientists warn a giant iceberg may soon break away from the shelf. Credit: Photo via Flickr user Stuart Rankin

An accelerating crack in the ice shelf known as Larsen C, the fourth largest ice shelf in Antarctica, has grown by 17 miles since the beginning of December, according to multiple news reports, including a recent article in the New York Times. The crack runs one-third of a mile deep, slicing through to the ice-shelf floor, and is, in total, more than 100 miles long.

Scientists with Project Midas, the British research team that has been monitoring the rift since 2014, warn that a giant iceberg measuring up to 2,000 square miles—approximately the size of Delaware—may soon break away, or "calve," from the shelf. "[T]his event will fundamentally change the landscape of the Antarctic Peninsula," wrote the Project Midas team.

We asked Northeastern's Daniel Douglass, lecturer in the Department of Marine and Environmental Sciences and an expert in glacial geography, to explain why form, what causes them to crack, and how they affect the environment.

What exactly is an ice shelf?

An is created when a glacier—ice that is moving over land—enters the ocean. The ice will float up and the ocean will flood under, thereby creating the ice shelf. An ice shelf can be anywhere from a hundred to a few thousand feet thick. It becomes progressively thinner toward the outer edge of the glacier. Calving is the process whereby pieces of ice break off the thinner, outer edge of the ice shelf to create icebergs. Ice shelves are different from sea ice, which forms when ocean water freezes. Sea ice is analogous to frozen lakes in winter and is usually less than 10 feet thick.

What role does climate change play in the break-up of an ice shelf? What other factors contribute to its dissolution?

A warming climate can contribute to calving in two ways. First, if the ice shelf is exposed to warmer air above and-or warmer water below, then there will be more rapid melting of the shelf. A thinner ice shelf is weaker than a thick ice shelf, and it is easier for a "through-going," or top to bottom, crack to form. Such a crack allows pieces of ice to break off the front of the shelf. Second, if water formed by the melting of the glacier's snow or ice has accumulated on the surface of the glacier and filled surface crevasses—cracks on the glacier's surface that do not go all the way through—then the water pressure at the bottom of the crevasse can widen and deepen the crack, potentially wedging all the way through the ice shelf,facilitating the calving process.

This second process was clearly in play when the Larsen B ice shelf, positioned just to the north of Larsen C, collapsed in 2003, but I am not sure that this has been a factor for the Larsen C. In the case of Larsen B, there were clearly large bodies of standing water on the surface of the ice before the calving event, and I have not seen that in any of the images of Larsen C. Nevertheless, the entire Antarctic Peninsula has been warming quite rapidly over the past several decades.

Generally, the calving process is a totally natural response to ice flowing into the ocean, and it should be expected. If warming is thinning and weakening the ice shelf, then there will be faster calving, producing more icebergs and the edge of the ice shelf will retreat.

Scientists say the disintegration of ice shelves contributes to rising global sea levels. How so?

Ice shelves act as buttresses to keep glaciers from flowing into the ocean. Sea levels rise when the ice in a glacier that is still on land accelerates into the ocean. The glacier then will lose ice to the ocean, and that transfer of ice mass displaces ocean water and sea levels rise.

Sea level rise has the potential to be the most expensive consequence of global climate change. Many of the world's largest cities grew in coastal environments because the nearby ocean facilitated transportation (shipping) and provided food (fishing). Sea level has not changed much in the past several thousand years, so it made sense to invest in infrastructure close to the water to facilitate the loading and unloading of ships. If sea levels rise too much, however, cities like New York, Mumbai, Shanghai, and of course Boston will no longer be in an ideal location. They could experience flooding during storms and perhaps even during twice-daily high tides. At first this will be an inconvenience, but as sea level rise becomes more dramatic, we will be faced with difficult decisions about whether to build sea defenses to protect the land from being flooded or to abandon certain areas to the rising waters.

How might we stop the processes that create these rifts?

Calving is an inevitable consequence of glaciers flowing into oceans. There are probably giga-technologies (very large-scale engineering processes; the extreme opposite of nanotechnologies) that could close the rift that has formed in Larsen C and suture the loose piece back onto the glacier, but I don't think that would be a good allocation of resources. That ice is already in the ocean, and the calving event itself does not cause rise until the land-based glacier accelerates into the ocean.

The long-term solution is to stabilize the Earth's climate so that glaciers don't continue to melt, thin, and accelerate into the ocean. The obvious place to start would be to reduce the amount of fossil fuels that are used in the global economy. The alternatives, including solar panels and wind turbines, are being improved all the time. Innovative research could yield a kind of energy revolution that permits us to transition away from fossil fuels entirely.

There are also a wide range of geoengineering options to manage the Earth's climate at the global scale. These include inducing reflective clouds in the atmosphere, fertilizing the ocean with iron so that algae growth absorbs excess carbon dioxide from the oceans and atmosphere, and mirrors in space to reflect incoming sunlight. Some of these methods will be more effective than others, but all are experimental, and all will have unintended and potentially negative consequences.

Explore further: Image: Glacial 'aftershock' spawns Antarctic iceberg

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SamB
1 / 5 (3) Feb 24, 2017
Oh Yes.. Lets worry.
In fact let us exaggerate the consequences of NOT worrying so that we can get everyone together in on the 'worrying'!
gkam
1 / 5 (4) Feb 24, 2017
Sam, scientists have a requirement they be correct, unlike salesman or businessmen.

Please do not project the ethics of your profession onto science.
TheGhostofOtto1923
3.7 / 5 (3) Feb 24, 2017
Sam, scientists have a requirement they be correct, unlike salesman or businessmen
-or psychopaths...

"At the same time, psychopaths are good imposters. They have absolutely no hesitation about forging and brazenly using impressive credentials to adopt professional roles that bring prestige and power. They pick professions in which the requisite skills are easy to fake, the jargon is easy to learn, and the credentials are unlikely to be thoroughly checked. Psychopaths find it extremely easy to pose as financial consultants, ministers, psychological counselors and psychologists. And that's a scary thought."
Da Schneib
5 / 5 (1) Feb 24, 2017
Good article, very informative. From a good source, too, a glacial geographer and marine scientist.
Mimath224
4.5 / 5 (2) Feb 24, 2017
Unfortunately in the final paragraphs we are back to current arguments and we all know, at present, where these stand, or not, as the case may be.
rex113a
not rated yet Feb 25, 2017
But our present approach to energy creation is no longer viable

Human economic development based on fossil fuel exploitation is causing the world to get warmer and is polluting our atmosphere.
Despite technological advances and without financial support, alternative energy sources other than fossil fuel, will continue to be relatively uneconomic.
Word-wide, Governments and their taxpayers won't pay directly for such subsidies on a sufficient scale, and politicians are unwilling to challenge them.
Unsubsidised, they won't attract investment.
All attempts to limit fossil fuel use at a sufficient scale and pace across the world without subsidies, have failed and fossil fuel use is still rising.
We need a step change to do this in other ways.
Easiest is to ration fossil fuel for "free burn1" applications. It is the same carbon atom before and after burning.
Schemes already exist.
Da Schneib
5 / 5 (3) Feb 25, 2017
Unfortunately in the final paragraphs we are back to current arguments and we all know, at present, where these stand, or not, as the case may be.
Arguments are one thing; brute facts are another.

When people start denying brute facts, the "argument" is over and they've lost.
Mimath224
5 / 5 (3) Feb 25, 2017
@Da Schneib Of course you're right but people can and do choose to ignore the facts. Where I live I see the denial every day. Oh, the politicians say we must this and that, again where I live, yet their actions say otherwise. Rivers are being diverted here and their and habitats lost. When the Ice Caps, Glaciers etc are gone it'll be too late and the blame game will start...not that it will matter much. I know that is a very pessimistic view and I wish I were wrong.
Da Schneib
5 / 5 (1) Feb 25, 2017
@Mimath, I'm much more pessimistic after watching the US get Trumped. The average IQ is 100. Somebody's got to keep it down there.
Mimath224
5 / 5 (2) Feb 25, 2017
Y'know, I am inclined to think that we have already gone too far. An individual might be intelligent but collectively the 'masses' may be not so much. I am just as much to blame as the next person...I have arguments with my family living abroad 'Oh Dad why don't you buy a 'so and so mobile' then you can messenger....etc'. I don't want to be 'in' when I'm out if you see what I mean but I make up for that with my PC as I do a lot of work on it. Then there is my car and though I don't use to go everywhere (I walk if only going 500 meters or half a mile, even in 35+C degrees) But, and this is the important point, I still want the petrol/gasoline available if I want it. How do we 'wean' ourselves off all of the things we have come to enjoy? Alternative fuel is a good philosophy but it doesn't seem to be available to all and many oppose these ideas. But if we want to stop the Ice Caps from melting...Oh, maybe I talk too much!
Da Schneib
3.7 / 5 (3) Feb 25, 2017
@Mimath, if we each do all we can, that's the most we can do. And if we each would, it would be enough. The problem is people who don't do anything, or do things that make a mess even though they know it makes a mess. You're part of the solution, not part of the problem. Keep on keepin' on, man.
Mimath224
5 / 5 (2) Feb 26, 2017
@Da Schneib nice of you to encourage me but it is difficult. Take for example, washing clothes; My daughter says to me '...dad get an automatic...' but I won't. The reason is when service fit it in all the water is connected to go straight down the drain. I have a twin tub and I fit an extension hose on the outlet and all the water goes on the garden. I would do something like that with the shower room but there i would need a pump (too many rooms between that and the garden to use a trough) and using extra electricity for the pump would rather defeat the object, Ha. However, if one lives in a flat very few savings can be made.
Where I live there are various religious festivals throughout the year and I think to myself that my efforts are lost when I see the amount of water wasted.
Whe I saw the Noerthern ice lands, years ago, I was awed and to think they may vanish...Society seems to be on a destructive course.

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