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Gigantic Iceberg Disintegrates as Concern Grows Over Glacier Stability, Sea Level Rise

The stability of a key Antarctic glacier appears to have taken a turn for the worse as a large iceberg that broke off during September has swiftly shattered. Meanwhile, scientists are concerned that the rate of sea level rise could further accelerate in a world forced to rapidly warm by human fossil fuel burning.

(Iceberg drifting away from the Pine Island Glacier rapidly shatters. Image source: European Space Agency.)

This week, a large iceberg that recently calved from West Antarctica’s Pine Island Glacier rapidly and unexpectedly disintegrated as it drifted away from the frozen continent. The iceberg, which covers 103 square miles, was predicted to drift out into the Southern Ocean before breaking up. But just a little more than two months after calving in September, the massive chunk of ice is already falling apart.

The break-off and disintegration of this large berg has caused Pine Island Glacier’s ice front to significantly retreat. From 1947 up until about 2015, the glacier’s leading edge had remained relatively stable despite significant thinning as warmer water began to cut beneath it. But since 2015, this key West Antarctic glacier has begun to rapidly withdraw. And it now dumps 45 billion tons of ice into the world ocean each year.

(Glaciers like Pine Island balance on a geological razor’s edge. Because they sit on a reverse slope, it only takes a relatively moderate amount of ocean warming to precipitate a rapid collapse. These collapses have happened numerous times in the past when the Earth warmed. Now, human-forced climate change is driving a similar process that is threatening the world’s coastal cities. Image source: Antarctic Glaciers.)

The present rate of melt is enough to raise sea levels by around 1 millimeter per year. That’s not too alarming. But there’s concern that Pine Island Glacier will speed up, dump more ice into the ocean and lift seas by a faster and faster rate.

Pine Island Glacier and its sister glacier Thwaites together contain enough water to raise seas by around 3-7 feet. The glacier sits on a reverse slope that allows more water to flood inland, exposing higher and less stable ice cliffs as the glacier melts inland. If the glacier melts too far back and the ice cliffs grow too high, they could rapidly collapse — spilling a very large volume of ice into the ocean over a rather brief period of time. As a result, scientists are very concerned that Pine Island could swiftly destabilize and push the world’s oceans significantly higher during the coming years and decades.

No one is presently predicting an immediate catastrophe coming from the melt of glaciers like Pine Island. However, though seemingly stable and slow moving, glacial stability can change quite rapidly. Already, sea level rise due to melt from places like Greenland and Antarctica is threatening many low-lying communities and nations around the world. So the issue is one of present and growing crisis. And there is very real risk that the next few decades could see considerable further acceleration of Antarctica’s glaciers as a result of human-forced warming due to fossil fuel burning.

Dr Robert Larter, a marine geophysicist at British Antarctic Survey, who has researched Pine Island Glacier in his work with the Alfred Wegener Institute, recently noted to Phys.org:

“If the ice shelf continues to thin and the ice front continues to retreat, its buttressing effect on PIG will diminish, which is likely to lead to further dynamic thinning and retreat of the glacier. PIG already makes the largest contribution to  of any single Antarctic glacier and the fact that its bed increases in depth upstream for more than 200 km means there is the possibility of runway retreat that would result in an even bigger contribution to sea level.”

CREDITS:

Hat tip to Colorado Bob

Hat tip to Erik Friedrickson

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From Ice Apocalypse to Mega-Thunderstorms, Continuing to Burn Fossil Fuels Makes the World Scary as all Hell

So I’ve got to say I feel for Eric Holthaus.

Here’s a smart guy. Probably a few years younger than me. A meteorologist by degree and a climate journalist by trade. A guy with two kids that, as is clear from his twitter comments, mean all the world to him. And he’s finally gotten to that point in his study of climate change where he’s thrown his hands up and said — this stuff scares the crap out of me, can we please all just do something about it?

(The calving front of the Pine Island Glacier as seen by a NASA DC-8 aircraft. Image source: Commons.)

For him, as with any of us, the point of existential realization can come through overexposure to a wide range of worsening climate problems. Declining ocean health, rising extreme weather, how much faster we are warming the world up than during the worst hothouse extinction, can all weigh heavily on the heart and mind of any compassionate, feeling person who takes these subjects seriously enough to actually read the science. For Eric, the big deal, and it is a very, very big deal, was sea level rise.

Ice Apocalypse

Yesterday, Eric penned this seminal article on the issue of ice cliff stability as explored by glacier scientist Robert DeConto entitled Ice Apocalypse.

Ice cliff stability is a pretty technical term. One that may make the eyes of your typical reader gloss over. But when we consider that the glaciers of Greenland and Antarctica can be upwards of two miles high, then the question of whether or not the cliffs of those great ice mountains are stable may start to generate a flicker of warning. May conjure up a phantom of the titanic roar set off when such ice giants tumble away into the sea as has happened throughout the deep history of Earth whenever the world warmed up by a certain amount.

When I think of the words ice cliff stability, my mind’s eye pictures a vast wall of numbing white-blue stretching hundreds of feet high. It expands both left and right as far as I can see. And it looms over an endless warming ocean. Waiting for a colossal fall if just that right amount of extra heat is applied.

Ice is fragile. It’s not like stone. It doesn’t flex much. It doesn’t give much. And even minor stresses are enough to make it shatter. We see this with ice cubes in a cup of water at home. Put an ice cube into relatively warmer water, and that little 1×2 inch block will snap and crack. Now just compound that fragility. Set it on the massive scale of a mile-high glacier. Not too hard to image what can happen.

(2012 filming of massive calving event at Jakobshavn Glacier.)

It’s happened already at Jakobshavn Glacier in Greenland. The ocean warmed. The ice shelf protecting the glacier dissolved. And the front of the gigantic glacier fell like great, enormous, white dominoes. We’ve seen it happening in films like Chasing Ice. And we’ve struggled to grasp the enormous scale of it.

Our burning of fossil fuels did this.

Jakobshavn is, even now, contributing to a more rapid rate of global sea level rise. But the amount of ice held back by Jakobshavn is small when compared to the vast volumes kept in check by the Pine Island and Thwaites Glaciers of West Antarctica. What Robert DeConto did, and what has apparently scared Eric Holthaus so much, was apply a computer model based on observations of Jakobshavn ice sheet collapse to these larger Antarctic ice masses.

The DeConto study unearthed results that, indeed, looked apocalyptic. From Grist:

A wholesale collapse of Pine Island and Thwaites would set off a catastrophe. Giant icebergs would stream away from Antarctica like a parade of frozen soldiers. All over the world, high tides would creep higher, slowly burying every shoreline on the planet, flooding coastal cities and creating hundreds of millions of climate refugees.

All this could play out in a mere 20 to 50 years — much too quickly for humanity to adapt…

Instead of a three-foot increase in ocean levels by the end of the century, six feet was more likely, according to DeConto and Pollard’s findings. But if carbon emissions continue to track on something resembling a worst-case scenario, the full 11 feet of ice locked in West Antarctica might be freed up, their study showed.

The DeConto study is just one scientific exploration of what could happen in West Antarctica this Century. And, already, reassurances to a worried Eric Holthaus are forthcoming.

But the problem with the DeConto study, as with any other form of serious climate risk, is that there are plausible scenarios in which terrible catastrophic events are possible even if their degree of likelihood is still somewhat debatable. And reasonable precaution would dictate that even if there were just a 10-20 percent chance of DeConto like events coming to pass, we would do everything we could to avoid them. The risk of this scenario emerging, however, is probably a bit higher. As numerous studies have identified the potential for 6, 8, or even 12 feet of sea level rise by as early as 2100.

The Future of Mega-Thunderstorms Looks Grim if We Continue to Burn Fossil Fuels

Eric’s appeals to his Twitter friends related to his article were touching to me in that I feel like I go through similar shocks with each passing week. And what should be a time of national thanksgiving even as more than half of Puerto Rico’s population is still in the dark 63 days after the climate change amplified blow of Hurricane Maria is no exception.

For a model study recently produced by Nature Climate Change and explored by Bob Henson at Weather Underground has found that the rate of rainfall in large thunderstorm clusters could increase by 80 percent this Century if fossil fuel burning proceeds along a business as usual pathway.

To put this in context, an 80 percent increase in the amount of rain that fell in the Ellicott City Flood in Maryland last year would have produced nearly ten inches of rain in an hour and a half.

(The rainfall intensity in large thunderstorm clusters was found to be greatly enhanced under worst case fossil fuel burning scenarios [RCP 8.5] according to a recent Nature Study. Image source: NCAR, Nature, and Weather Underground.)

As with ice cliff instability, we find ourselves faced with another scientific term in the new study — mesoscale convective systems (MCS). And to translate this term we can simply say that MCSs are gigantic clusters of thunderstorms. The study found that rainfall amounts in the largest of thunderstorm complexes were greatly enhanced as warming proceeded along a business as usual track.

From the Study author’s statement to Weather Underground:

“These new simulations of future MCS rainfall are concerning, because they show very large increases in the amount of rain that a given MCS is likely to produce. The MCSs that we would today consider to be ‘extreme’ in terms of precipitation would become more commonplace in the future. There are also some regions that currently don’t see a lot of MCS activity that might start seeing some of these heavily raining MCSs in the future.”

These increases are on top of already elevated rates of rainfall intensity we presently see today in destructive events that our infrastructure and disaster planning is clearly not prepared for (as seen during Harvey). So as we take the time to give thanks for the great bounty that many of us still have, perhaps we should also take the time to think of the things we can do to keep safe what we have worked so hard for and care so much about and to do our best to help those who are less fortunate. Who have already fallen casualty to a time of troubles.

Doomed Pine Island Glacier Releases Guam-Sized Iceberg into Southern Ocean

Science has confirmed it. Human-caused warming is killing Antarctica’s massive Pine Island Glacier (PIG). And this week’s release of a chunk of ice larger than Guam into the southern ocean is just one of the many major losses that will occur as part of what is now an inevitable demise of one of the world’s greatest glaciers.

(CNN provides this stunning NASA imagery sequence of the break-off of B-31, a 12×24 mile iceberg from the, now doomed, Pine Island Glacier.)

Heat-Charged Blow to The Soft Underbelly of Antarctic Ice Shelves

As human greenhouse gas emissions caused the world’s oceans to warm, upwelling currents delivered a portion of that heat to the continental shelf zone surrounding Antarctica. A fortress of ice, numerous glacial ice shelves thrust out from this frozen land and drove deep into the sea floor. Ocean-fronting glaciers featured submerged sections hundreds of feet below the sea surface.

The warming currents encountered these massive ice faces, eroding their undersides and providing pathways for ocean waters to invade many miles beneath the glaciers. These invasions subjected the vulnerable ice shelves not only to the heat forcing of an ever-warming ocean, but also to wave and tidal stresses. The reduction in grounding and the constant variable stresses set the glaciers into a rapid seaward motion.

Antarctica’s most vulnerable glaciers lie along its western out-thrust. Two, Thwaites and the Pine Island Glacier, have recently seen very rapid increases in forward speed. Of these, the Pine Island Glacier, according to a recent study, is undergoing the process of an irreversible collapse. What this means is that the glacier’s speed of forward motion is now too great to be halted. Inevitably, even if the climate were to cool, the entire giant glacier will be launched into the world’s oceans where it will entirely melt out.

PIG basal melt

(Pine Island Glacier underwater melt dynamics. Image source: Nature)

Guam-Sized Chunk of Ice to be One of Many

The Pine Island Glacier is massive, covering a total area of 68,000 square miles and, in some locations, rising to over 2,000 feet in height. It represents 10% of all the ice in the West Antarctic Ice Sheet, holding enough liquid water to raise sea levels by between 1 and 2.5 feet all on its own. And the now destabilized PIG is bound to put added stresses on the adjacent Thwaites glacier together with almost the entire West Antarctic ice system.

Over recent years, PIG’s forward speed has accelerated. Increasing forward velocity by 73 percent from 1974 to 2007. Surveys made since that time show an even more rapid pace. By January of this year, studies were finding that PIG had entered a sate of irreversible collapse. So it is little wonder that enormous chunks of ice are breaking off from this massive glacier and drifting on out into the Southern Ocean.

As of early this week, the immense ice island dubbed B31 measuring 12×24 miles in size (nearly 290 square miles), slid off its temporary grounding on the sea bottom and began its journey out into the Southern Ocean. There it will remain for years, plaguing the world’s shipping lanes as it slowly disintegrates into a flotilla of icebergs. It is just the most recent event in the now ongoing decline of PIG. And we can expect many, many more major ice releases as this vast Antarctic glacier continues its dive to the sea.

Links:

Humongous Iceberg Slowly Drifts Away From Antarctica

Scientists: Warming Ocean, Upwelling Make an End to Antarctica’s Vast Pine Island Glacier

Nature

Retreat of Pine Island Glacier Controlled by Marine Ice Sheet Instability

The Pine Island Glacier

The Thwaites Glacier

Hat tip to Colorado Bob who’s been tracking PIG since 1994

 

 

Greenland Shatters Previous Melt Record Set in 2010; One Month of Melt Yet to Go

(Photo Credit: Marco Tedesco)

According to reports from Arctic researchers headed by Marco Tedesco, Greenland broke the melt record set in 2010 on August 8th of this year. With one month of melt still remaining, it appears that Greenland is now set to shatter all previous melt records since observations began 30 years ago.

This record melt coincided with the hottest summer Greenland has experienced in at least 123 years, the last time melting covered the entire ice sheet, as indicated by ice core data. It has also resulted in structural damage to parts of Greenland’s infrastructure.

“With more yet to come in August, this year’s overall melting will fall way above the old records. That’s a Goliath year — the greatest melt since satellite recording began in 1979,” noted researcher Marco Tedesco, assistant professor of Earth and atmospheric sciences from The City College of New York.

Tedesco and his fellow researchers made use of an array of microwave sensors aboard a US Air Force Satellite system called the Defense Meteorological Satellite Program. These sensors tracked melt over the Greenland ice sheet and established enough data to conclude that 2012 melt had entered record territory by August 8th.

The data Tedesco produced showed extreme melting in every region of Greenland including the higher elevation areas to the north. In these higher elevation areas, melt generally only continues for a few days. This year, so far, melt in these areas has occurred for more than two months running.

“Part of the meltwater will refreeze and part of the meltwater will run off to create streams and eventually take off into the sea and contribute to sea-level rise or the hydrological cycle,” Tedesco said during an interview with the magazine LiveScience.

Melt water also tends to bore holes through the ice sheet, finding its way to the bottom where it serves as a lubricant that can speed the movement of glaciers heading to sea.

For much of this summer, Greenland has experienced long periods of record warmth. This has likely contributed to increased melt volumes and durations. In addition, sea ice, which tends to serve as an atmospheric insulator for the Greenland ice sheet has diminished to record lows for much of the summer. This one-two punch is having a severe impact on Greenland’s ice sheet and is likely a major contributor to the record melt we’ve seen this summer.

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Links:

http://www.livescience.com/22387-greenland-melting-breaks-record.html

http://www.huffingtonpost.com/2012/08/15/greenland-ice-sheet-melting_n_1783063.html#slide=1114410

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