More ice loss through snowfall on Antarctica

Dec 12, 2012
Image: National Science Foundation

Stronger snowfall increases future ice discharge from Antarctica. Global warming leads to more precipitation as warmer air holds more moisture – hence earlier research suggested the Antarctic ice sheet might grow under climate change. Now a study published in Nature shows that a lot of the ice gain due to increased snowfall is countered by an acceleration of ice-flow to the ocean. Thus Antarctica's contribution to global sea-level rise is probably greater than hitherto estimated, the team of authors from the Potsdam Institute for Climate Impact Research (PIK) concludes.

"Between 30 and 65 percent of the gain due to enhanced in is countervailed by enhanced ice loss along the coastline," says lead-author Ricarda Winkelmann. For the first time, an ensemble of ice-physics simulations shows that future ice discharge is increased up to three times because of additional in Antarctica under global warming. "The effect exceeds that of surface warming as well as that of basal ice-shelf melting," Winkelmann says.

During the last decade, the has lost volume at a rate comparable to that of Greenland. "The one certainty we have about Antarctica under global warming is that snowfall will increase," Winkelmann explains. "Since surface melt might remain comparably small even under strong , because Antarctica will still be a pretty chilly place, the big question is: How much more mass within the ice sheet will slowly but inexorably flow off Antarctica and contribute to sea-level rise, which is one of the major ."

Since snowfall on the ice masses of Antarctica takes water out of the global water cycle, the continent's net contribution to sea-level rise could be negative during the next 100 years – this is what a number of global and regional models suggest. The new findings indicate that this effect to a large extent is offset by changes in the ice-. Snow piling up on the ice is heavy and hence exerts pressure – the higher the ice the more pressure. Because additional snowfall elevates the grounded ice-sheet but less so the floating ice shelves, it flows more rapidly towards the coast of Antarctica where it eventually breaks off into icebergs and elevates sea level.

A number of processes are relevant for ice-loss in Antarctica, most notably to sub-shelf melting caused by warming of the surrounding ocean water. These phenomena explain the already observed contribution to sea-level rise.

"We now know that snowfall in Antarctica will not save us from sea-level rise," says second author Anders Levermann, research domain co-chair at PIK and a lead author of the sea-level change chapter of the upcoming IPCC's 5th assessment report. "Sea level is rising – that is a fact. Now we need to understand how quickly we have to adapt our coastal infrastructure; and that depends on how much CO2 we keep emitting into the atmosphere," Levermann concludes.

Explore further: Hurricane Edouard right environment for drone test (Update)

More information: Winkelmann, R., Levermann, A., Martin, M.A., Frieler, K. (2012): Increased future ice discharge from Antarctica owing to higher snowfall. Nature, doi:10.1038/nature11616

Related Stories

Greenland and Antarctic ice sheet melting, rate unknown

Feb 16, 2009

The Greenland and Antarctica ice sheets are melting, but the amounts that will melt and the time it will take are still unknown, according to Richard Alley, Evan Pugh professor of geosciences, Penn State.

Warming ocean could start big shift of Antarctic ice

Sep 19, 2012

(Phys.org)—Fast-flowing and narrow glaciers have the potential to trigger massive changes in the Antarctic ice sheet and contribute to rapid ice-sheet decay and sea-level rise, a new study has found.

Antarctic ice loss speeds up, nearly matches Greenland loss

Jan 24, 2008

Ice loss in Antarctica increased by 75 percent in the last 10 years due to a speed-up in the flow of its glaciers and is now nearly as great as that observed in Greenland, according to a new, comprehensive study by UC Irvine ...

New structure found deep within West Antarctic Ice Sheet

Sep 23, 2004

Ice sheet more susceptible to change than previously thought Scientists have found a remarkable new structure deep within the West Antarctic Ice Sheet which suggests that the whole ice sheet is more susceptible to future ch ...

Warm sea water is melting Antarctic glaciers

Dec 06, 2012

The ice sheet in West Antarctica is melting faster than expected. New observations published by oceanographers from the University of Gothenburg and the US may improve our ability to predict future changes in ice sheet mass. ...

Recommended for you

NASA catches a weaker Edouard, headed toward Azores

3 hours ago

NASA's Aqua satellite passed over the Atlantic Ocean and captured a picture of Tropical Storm Edouard as it continues to weaken. The National Hurricane Center expects Edouard to affect the western Azores ...

Tree rings and arroyos

Sep 18, 2014

A new GSA Bulletin study uses tree rings to document arroyo evolution along the lower Rio Puerco and Chaco Wash in northern New Mexico, USA. By determining burial dates in tree rings from salt cedar and wi ...

User comments : 16

Adjust slider to filter visible comments by rank

Display comments: newest first

Lurker2358
2.9 / 5 (15) Dec 12, 2012
As the temperature in Antarctica rises due to the greenhouse effect, you will expect several phenomena:

1, the minimum temperature of the snowpack and ice will increase due to higher ambient heat.

2, Surface melt in summer will increase because the ice is "warmer" to begin with, making it slightly easier to melt.

3, Sublimation will increase due to more ambient heat, even where temperatures remain below freezing.

4, much like has been experienced in the continental N.A. and Eurasia, these effects may offset totally the increased snowfall.

Example: During the year with "snowmageddon" the average snowpack was actually smaller than average, even though to snowfall totals were anomalously large, because the snow was melting away faster than it fell anyway, in spite of making many record high snowfall rates and accumulations.

Therefore increased snowfall due to higher convection from warmer SST necessarily guarantees neither increased accumulation of snowpack nor net gains in snowpack
brant
1.4 / 5 (20) Dec 12, 2012
First you have to show that the "greenhouse" effect is real...

Then you have to show that it actually has been warming as much as they say.

Then you have to show that it is not from solar activity.

And you have to show that the sea level is rising like they say....

http://wattsupwit...re-75580
Lurker2358
2.8 / 5 (19) Dec 12, 2012
First you have to show that the "greenhouse" effect is real.

It was known to be real at least as far back as Tesla and Edison.

Then you have to show that it actually has been warming as much as they say.

It has. The people in Greenland and Iceland and parts of northern Europe have seen it warm enormously in their lifetimes.

Then you have to show that it is not from solar activity.


Since we have many instruments, such as satellites and solar orbiters, in space studying the Sun, they would know if any increase had been taking place since the space race era.

And you have to show that the sea level is rising like they say.

It is.

I tried all this when I was a skeptic, and since nobody could convince me otherwise, I set out to prove myself wrong, and succeeded.

You can learn a lot by doing some thought experiments about the albedo feedback. I won't tell you how to do that, because it will be too easy and you won't learn anything if I tell you.

Good luck.
Parsec
4.1 / 5 (9) Dec 12, 2012
Its hard to argue with people who refuse to look at the information that is readily available out there. Actual measurements show that the global average temperature and the sea level are both rising.

Since there are a number of different techniques to measure these things, and they all agree, it is only ignorance that could motivate someone to believe these measurements are not valid.

Its like arguing that gravity doesn't exist, or equally, that the earth is flat.
maxberan
1.9 / 5 (7) Dec 12, 2012
Where do they suppose the moisture come from that falls as snow over Antarctica if not the ocean? It's like they were standing on a bridge watching the river flowing underneath and saying that the catchment upstream must be losing all its water.
Lurker2358
1.8 / 5 (10) Dec 12, 2012
Where do they suppose the moisture come from that falls as snow over Antarctica if not the ocean? It's like they were standing on a bridge watching the river flowing underneath and saying that the catchment upstream must be losing all its water.


The water comes from the ocean. They never claimed otherwise.

The problem is the ice melts or calves faster than the new snow falls.
eachus
1.8 / 5 (10) Dec 12, 2012
Sigh! Get the facts right... First, getting CO2 under control before it wipes out the human race, independent of global warming is necessary. As to global warming, the unresolved question is how do clouds interact with higher CO2 levels. The evidence so far, is warming at the poles, cooling in the tropics, and some of both in between. Net CO2 effect on global temperature? Probably warming, but at much lower levels than the extremists claim.

Am I a climate denier? Probably, but see the first sentence above. Elevated CO2 levels are already leading to both local death events, as well as global threats for those with breathing problems. Why am I so upset at some of the AGW crowd? Cleaning up cow farts will not deal with the effect of CO2 levels on humans.
VendicarD
3.3 / 5 (7) Dec 12, 2012
Brant apparently is unconvinced that the earth's surface temperature is higher than that of the moon.

"First you have to show that the "greenhouse" effect is real..." - Brant

For the sake of Humanity. Brant should not be permitted to reproduce.
Dug
1.5 / 5 (12) Dec 12, 2012
Global warming is a logical expectation given the amounts of fossil fuel we burn and the CO2 produced. What isn't logical is that our satellite sea level altitude measuring capability is 20mm, but we are using it to measure a supposed 3mm annual variation, which still doesn't match actual tidal measurements. We are producing computer models of climate change that have an absolutely miserable record of predicting climate change thus far. We are still finding large holes in these models - like particulate and volatiles estimates and other significant variables. I'm sure humans are having an impact on climate. I'm equally sure that we are clueless as to how to measure anywhere close to the claims that being made by climatologist and climate modelers. I'm even more sure that if we were serious about anthropogenic climate change - we would address it at its source - the human population. Want to reduce human caused climate change - reduce the human population.
Urgelt
3.3 / 5 (7) Dec 12, 2012
eachus wrote, "...the unresolved question is how do clouds interact with higher CO2 levels."

Wow. Scientists couldn't figure out 'the unresolved question,' so eachus steps up to the plate and tells them what to think.

Just one problem. There are *lots* of unresolved questions in climate science.

Here's a good one: how, exactly, will clathrate release feedback cycles manifest?

Or this one: what's the jet stream going to do as AGW progresses, and how will that play into climate change?

Or this one: how will changing anthropogenic emissions of aerosols affect climate change?

Or this one: how much of a feedback effect will albedo reductions in the Arctic (and elsewhere) generate?

In fact nearly everywhere you look, climate science is peeling back complexities and refining models to nail down dozens, hundreds of unresolved questions.

One thing I've come to expect of deniers is their inability to tolerate complexity. They cling to simplicity where none exists.
Sinister1811
1.7 / 5 (15) Dec 13, 2012
First you have to show that the "greenhouse" effect is real...


Of course it's real. It has been proven for centuries. We also know that the "greenhouse" effect is the primary cause of hostile conditions on Venus.

Then you have to show that it actually has been warming as much as they say.


There are decades worth of measurements done by climate scientists that show a correlation between an increase in CO2 (from the beginning of the industrial era) and the gradual rising of temperatures, globally.

Then you have to show that it is not from solar activity.


In terms of the sun, nothing's changed. But CO2 is the primary cause of an increased absorption of heat from the sun.

And you have to show that the sea level is rising like they say....


Really? Well, there has been a slight increase in flooding of coastal areas around the world lately. With the melting of the Arctic, it can only contribute to an increase in sea level.
gregor1
2.1 / 5 (19) Dec 13, 2012
Wow! They've just discovered gravity! The wonders of these modelers never ceases to amaze. Not only are they the high priests of AGW but now they're clowns too!
Lurker2358
1.8 / 5 (10) Dec 13, 2012
Or this one: how much of a feedback effect will albedo reductions in the Arctic (and elsewhere) generate?


Somewhere between half and 3/4ths of the existing forcing is caused by the albedo feedback.

This does not bode well, because the albedo feedback is only just getting started.

In the Northern Hemisphere, most of the albedo feedback is actually occurring due to changes in continental ice and snow packs below the Arctic Circle, due to the angle of sunlight incidence being higher than in the arctic circle.

The albedo feedback hits the arctic sometime in late july through early october, but it is removed entirely from the Arctic by November 6, this is caused by mechanical, physical limits due to seasonal parameters of the orbit

It's not that CO2 doesn't matter, it's that the CO2 pushes the baseline up more and more, and that pushes the melting days up more and more, and that pushes the albedo feedback up more and more, etc.
maxberan
4 / 5 (2) Dec 13, 2012
Lurker: But rather incredible not spelling it out don't you think! It switches the issue from straightforward conservation of mass where they seemed to want it to lie to the credibility of a model of ice dynamics, a much more uncertain matter. I detect no calibration against any history of inputs and outputs. To be convincing, we would need to see the author's independent (of a model) evidence of past positive feedbacks where increased input leads to enhanced output leading to reduced storage. The facts on the ground, and hence the default that needs to be overturned, would imply a chain of feedbacks where departures from normal input lead to departures of similar magnitude of the output and a balance over the long term. I could be doing them an injustice but I notice the authors work for an outfit dealing with impacts. In my experience "impacts" people are often well removed from the basics of the processes they deal with and not nearly sceptical enough when piling model upon model.
RobPaulG
1.9 / 5 (16) Dec 13, 2012
Did you guys not get the memo? It is called climate change now, because there has been no warming in 15 years...
mountain_team_guy
1.6 / 5 (13) Dec 13, 2012
More equals less. Of course. Common sense is obsolete. Just climb on the bandwagon sheeple.