Floods Beneath Antarctica's Ice Sheet Create a Glacial Slip-and-Slide

By Eliza Strickland | November 17, 2008 2:06 pm

Antarctica glacierDeep beneath the Antarctic ice sheet, floods of water from buried lakes can hurry glaciers along on their slow slide towards the sea, according to a new study that tracked recent floods beneath the Byrd Glacier. “It’s like putting in a squirt of oil,” says Andy Smith of the British Antarctic Survey, who was not involved in this latest study. “The water lubricates the base of the glacier” [New Scientist]. The findings will help researchers understand the movement of glaciers around the world, a matter of great interest to climate scientists who are investigating how rapidly ice sheets may melt into the ocean due to global warming.

Researchers discovered only recently that inaccessible subglacial lakes in Antarctica periodically shed huge quantities of water. Data collected by a satellite launched in 2003 … revealed a complex network of subglacial plumbing in which water periodically cascades from one hidden reservoir to another [AFP]. The water in the lakes remains liquid, despite being buried beneath a mile of ice in some places, due to warmth from the underlying rock. Now, researchers have shown that these hidden floods affect the thick mountains of ice above.

As reported in Nature Geoscience [subscription required], researchers measured the elevation of the ice in the Byrd Glacier by satellite. When the subglacial lakes fill up, they raise the elevation of the ice above them, and when the water spills over in a flood, the elevation sinks again, allowing researchers to track the water. Between December 2005 and February 2007 researchers saw rapid changes in the ice elevation that coincided with a marked increase in the speed of the ice flow. Conversely, the movement of the glacier slowed when the flood ceased and the lakes began to refill [New Scientist].

Researchers stressed that the floods beneath the Byrd Glacier were not caused by global warming: The lakes probably flood and drain on a regular basis that has nothing to do with atmospheric or ocean warming. However, the scientists say the mechanisms involved need to be understood so the knowledge can be applied to those ice masses which are being exposed to warmer temperatures, such as in Greenland [BBC News]. The International Panel on Climate Change (IPCC) has said that one of the great unknowns regarding climate change is what proporition of the world’s ice sheets will melt into the ocean, and how much that will raise sea levels.

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Image: flickr / giladr

CATEGORIZED UNDER: Environment
  • Kim

    It’s unbelievable that scientists have been able to uncover this. And the face that the glacier’s movements might not be an affect of global warming is an important idea too. It turns global warming into a concept, sure we are leaving a horrid carbon foot print but what if some of the “affects of global warming” are actually supposed to happen?

  • Kin

    ….what’s up with this article? “heat of underlying rock”. I’m pretty sure it’s mostly the massive pressure from the mile of ice. What I’m really asking is for the distinction that should be here between the flood waters and natural lubrication caused by the pressure not allowing freezing. Because as an article it’s not clear.

  • http://climatechangepsychology.blogspot.com Tenney Naumer

    kimmie, dear, is that really you?

  • http://www.flickr.com/groups/coach-purses-ca/discuss/72157626756354934/ Florencio Lepri

    A powerful share,

  • http://capoeirameister.de/ Alvin Lykken

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  • Jay Yoon

    The article says the subglacial lakes fill up, drain, and then fill up again, and drain, ad infinitum. But it doesn’t say what happens if there becomes a subglacial lake that is so big that it doesn’t stop draining until a very long time has passed? It’s clear that the speed of the glacier doesn’t drop back down until the subglacial lake is fully drained so in that situation, the glacier would move very quickly for a very long time, which could be a situation in which catastrophic glacial flow might happen.

    I have also inferred the following: the fact that there is a period of time in which the subglacial lake fills up implies that the inflow into the subglacial lake from melting (I presume at the base of the glacier near the subglacial lake) exceeds the outflow due to drainage. Since the amount of melting (and hence inflow) is not that significant, it must be the case that outflow due to drainage must be insignificant to a greater order; otherwise, the subglacial lake wouldn’t be able to fill up. The fact that the subglacial lake eventually drains means that the amount of drainage must increase dramatically; again, because if this didn’t happen, then the lake would simply continue to fill up rather than draining. I predict that the reason why the drainage amount increases drastically is because of the same reason why ice floats in water; namely, the mass of ice immediately above the vicinity of a subglacial lake is subject to a large buoyant force .

    The surrounding mass of ice that is not immediately above the vicinity of the subglacial lake, of course, is continuous with the ice that is immediately above. If this were not the case, and they were completely disconnected, the “pillar” of ice immediately above the subglacial lake would jut upward like a spike above the surrounding ice due to the buoyant force.

    This would not occur if the subglacial lake wasn’t filled up to a large extent, because then the ice would displace only a tiny volume of the water in the lake (only up to the water level). But the upward buoyant force is a linear function of the height of the water underneath the subglacial lake. When the height of the water exceeds a certain threshold (where the upward buoyant force exerted on that portion of the ice sheet above the subglacial lake exceeds the total gravitational downward force exerted on that said portion), that portion of the glacier would be rapidly pushed upward.

    If the subglacial lake encompassed the entire base of an ice sheet, the entire ice sheet would, as a single mass, be lifted upward by the enormous hydrostatic buoyant force…and from that point on, a hydrostatic situation would have changed into a hydrodynamic situation. This is doubly significant since much of the West Antarctic and Greenland ice sheets have bases that are significantly below present-day sea level (and incremental gradual melting of these ice sheets prior to my purported catastrophic event would again increase that). This gives us an almost infinite reserve of seawater that can seep underneath the ice sheet in the space between the ice sheet and the bedrock on which it lies. And since water inevitably tries to go “downstream,” if the glacier bedrock is below sea level, the oceans will “go downstream” underneath the glacier bedrock if at all possible. I conjecture that if the ocean at large and a subglacial lake ever meet each other, either because the former encroaches into and under the ice sheet, or the latter grows large enough, then nothing will prevent the sea from then exploiting that channel/gap, no matter how small, and making it grow into an unsealable gap. This positive feedback cascade, again, will occur because the sea is at a higher elevation (sea level) than the bedrock under the ice sheet/glacier, which is below sea level, and the mass of the ocean is so large that essentially nothing will stop it from flowing downward into an area of lower gravitational potential – and the worst part is that the ocean is essentially an infinite reservoir, so the ensuing cascade can continue for a very, very long time before a new equlibrium is reached – and by then, the entire ice sheet may have been, and I predict, will be, lifted up, disintegrate, and lead to an ESSENTIALLY INSTANTANEOUS increase in the sea level, rather than the more gradual sea level increase that many climatologists are predicting would happen (they really only consider the possibility of comparatively slower meltwater runoff).

    It’s the difference between holding an ice cube above a glass of water that’s full, and seeing what happens as the gradual melting of the ice cube “drips” into the glass – sure, the glass of water will overflow, but the effect will be almost trivial since only one drop of excess overflow leaves as one drop from the ice cube falls. If you wait until the ice cube melts completely, then the amount of overflow will be equal to the total volume of water initially “locked up” in the ice cube. But if the ice cube is “dropped” into the glass of water that’s full, it will immediately cause an overspill of water equal to the volume of the ice cube itself. And of course, it is obvious that an ice cube melts faster when placed in water than when placed in air…but that is not the most important point. What is most critical is that the falling ice cube will cause an essentially INSTANTANEOUS increase in the sea level (which corresponds to overspillage of the water in the glass). An ant, say, near the base of the glass of water would not be subject to a trickle of water, which he can adjust and adapt to, but rather an immediate and enormous torrent of water falling onto it, which he obviously cannot adapt to (i.e. he will die in a massive deluge).

    If you scale up the above thought experiment so that the ice cube is an ice sheet and the glass of water is the ocean, then that gives you a clue as to how big the difference is in a gradually melting ice sheet that maintains its fixture to the bedrock below (no matter how fast the melting occurs), and a ice sheet that gets lifted up above the bedrock due to buoyancy (an ice sheet being “lifted up” over the water is functionally identical to an ice sheet being “dropped down into” the water). In the long run, the same amount of water enters the ocean, but in the former, the effect occurs over thousands of years, and in the latter, it happens almost overnight (especially since it’s a positive feedback cycle in which the process cannot be stopped by any means natural or human once initiated).

    The biggest problem with climate science today is that it constantly understates the potential consequences into an almost triviality. Even the so-called “climate alarmists” who voice their concerns about “catastrophic” climate change talk about what’s going to happen over the next 100 years or so (the next century blah blah). They say that the sea level might rise 2 meters over the next 100 years, and that if that happened, 100 million people would be displaced. Of course, if it happens over a 100 years, then human societies can adjust incrementally. They also say that in the worst case scenario, if the Antarctic and Greenland ice sheets melt completely, that the sea level would rise by 70-80 meters – but they qualify that scenario by saying that this isn’t something that can happen even in what is pretty long in the people-who-are-alive-now sense of 100 years, but is rather something that may happen (in the worst case scenario) of perhaps 5000 years (since we know that 18,000 years ago, North America was covered by an ice sheet, and that 8000 years ago, it was largely gone…and since that happened without any human causes, with the CO2 forcing that exists in the modern world, it could potentially happen twice as fast…so 5,000 years or so).

    We’re used to catastrophes occurring suddenly and with enormous rapidity. Maybe this is due to the Hollywood disaster movies that are so shamelessly unscientific or just due to human psychology’s love for drama…or maybe it’s actually something that scientists really need to think about. Maybe they need to think about the possibility that climate change could lead to effects that are truly catastrophic in the sense that they will occur ESSENTIALLY OVERNIGHT, and that their “worst-case-scenario” is correctly hypothesized in the sense that a 50-70 m sea level rise will occur…but that it is dead wrong in that it will happen just like a snap of the finger – and NOT in 5,000 years or a “geological” time span.

    The phrase “calm before the storm” is entirely apropos in this situation. The gradual increase in sea level that will occur before the “storm” will lull scientists into peddling their complacent, politically correct, long-term projections, and the anti-science folk into a smug sense of thinking that they’re smarter than the “experts.”

    But there will come a day when all squabbling will end, for the catastrophe is upon humanity. It will be the utmost irony when the climate change denial folks will realize that they did win the argument – they did refute the claims of the climate scientists – but tragically, they refuted what the scientists in their dogmatic clinging to uniformitarianism and limited imagination had warned about – and not the true disaster that was now befalling them. What they denigrated as “alarmism” in the scientific community and thus rejected was ironically, the greatest of understatements. And it will be an even greater irony when the so-called “expert” scientists find out – and it’s too late to do anything about it – that the warning was in the Bible (also the Epic of Gilgamesh, Sumerian legends, the Atlantis myth) all along – and that they were so close to saving the world from the catastrophic flood (for Noah, it was a tragedy, for us, it will be a farce), but their petty rejection of the world’s oral traditions and history (whether they are actually infallible and the Word of God notwithstanding) as obsolete, and inferior to their advanced, “cutting-edge,” “scientific” knowledge was their undoing, and were thus felled by their dismissal of true catastrophic events in our distant past (which were also related to ice sheets, a warming in the Earth’s average temperature) as “myths” that were beneath consideration.

    Shakespeare knew human nature the best when he said that history repeats itself – first as tragedy then as farce.

    We are all so proud about showing each other that the others’ arguments are wrong, and that we’re right. But we should always remember that just because someone’s argument is wrong doesn’t mean that yours is right.

    Key point: scientists underestimate the catastrophic potential of climate change, and then try to oversell it. the public, and laypeople, see this as exaggeration and alarmism, and instead of saying: “what if it’s WORSE,” they are content with the self-satisfaction that “they’re going to be right and the experts are going to be wrong.” Our need to feel like we’re right, our dichotomous either this – or that thinking, and our lack of openness to others’ viewpoints will everyone – with no malevolent intentions, to make the worst collective decisions.

    If only the scientists actually consider catastrophism as truly possible (and historically relevant), and not merely an old wives’ tale or an “unscientific” religious myth…as the public in general, although rejecting or denying the prophecies of the scientists, adamantly believe in prophecies of disaster both in the past and in the future…so it’s not that like scientists don’t know that some people believe that such catastrophes will happen – it’s that they consider those predictions as “unscientific” because they selectively look at the world from their own narrow disciplines). Of course, the public is to blame also, but if the experts call themselves experts, then it’s THEIR responsibility to warn the public – and move beyond those narrow confines of uniformitarianism – perhaps just this one time.

    Yes, climate change is real – yes it’s much worse than people think.

    Unfortunately, if CO2 emissions are something that has a large impact on climate, then we’re probably screwed – because once the disaster hits the runaway threshold, it will stay its course until millions die. Really – the best thing to do is PRAY that the scientists have overstated the effects of CO2 on the climate – because if they’re right on that – then not only will really, really bad things possibly happen, it might be literally impossible to prevent it from happening.

    Good day!

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