The Earth Story

Collapsing ice cap

This cracked-up glacier is one of the outlets of Kapp Mohn outlet glacier that drains the Austfonna ice cap in the Svalbard archipelago, a small group of islands found north of Norway in the Arctic Ocean.

Austfonna is a large, permanent ice cap, sitting in the high ground on a portion of Nordaustlandet Island. It covers an area of 8,200 square kilometers and the ice is on average over 500 meters thick. Or at least, it used to be.

This ice cap is literally collapsing before our eyes. The outlet glacier pictured in this image accelerated by a factor of 25 from 2013 to 2016, causing dramatic drops in the thickness of the ice upstream. The European Space Agency has launched several satellites in their Sentinel program containing sophisticated radar systems able to measure small changes in elevation on the Earth’s surface, including the elevation of ice caps. Combined with previous measurements of the thickness of this ice cap, scientists from the University of Leeds determined that since 2012, this ice cap has lost 1/6 of its thickness, driven by the acceleration at this outlet glacier.

The waters of the Arctic Ocean have warmed at a rapid pace relative to the rest of the world over recent years, and 2012 in particular was a year of exceptional melting and warmth in the arctic due to some extreme storms. The sudden movement in this glacier suggests that this pulse of heat has helped destabilize glaciers in the surrounding territory and it is happening at an exceptionally rapid pace. Several other glaciers in this area have begun similar surges over the past few years - accelerating their motion towards the ocean by a factor of 10 or more. 

At present, about 1/3 of the sea level rise in the last century is estimated to have been contributed by melting glaciers, but sudden acceleration in large ice caps like this one keep making the case that the ice caps worldwide, which hold large quantities of water on land, are one way that sea level rise can and will accelerate as the planet warms due to human-imposed increases in greenhouse gases. 

-JBB

Image credit: Thorben Dunse, University of Oslo http://wapo.st/1zH9rs0

Read more: http://dx.doi.org/10.1002/2014GL062255 http://www.sciencedaily.com/releases/2015/01/150123081723.htm http://www.cpom.org/research/largeice.htm https://www.smithsonianmag.com/science-nature/what-surging-glaciers-svalbard-tell-us-about-future-rising-seas-180970060/ https://www.the-cryosphere-discuss.net/tc-2017-5/tc-2017-5.pdf

evosia

Drone flight up to the ice cap atop Eyjafjallajökull volcano, Iceland. Original caption:

Hiding a volcano

Take a good look at this image. This shot was taken in Antarctica, on top of several kilometers of ice. Ask yourself this question…if there was a volcano directly underneath these people…could they know it? A kilometer of ice…some volcanoes might poke through that, but many wouldn’t.

Dr. Doug Weins from Washington University in St. Louis might have just found one. As part of one of the investigations of the ice sheet, their research group deployed a series of seismographs on the surface of the West Antarctic Ice Sheet. Seismographs can help monitor the thickness of the ice and how it is flowing, so the deployment wasn’t necessarily there to look beneath the ice.

In 2010 and 2011, those seismographs started recording earthquakes. A fairly good number of earthquakes, over a thousand, in one spot under 2 kilometers of ice, 55 kilometers from the nearest known volcano. Movement of magma through the Earth’s crust gives a specific seismic signature, producing small earthquakes just like these, meaning they were likely caused by movement within a magma chamber.

Other seismic investigations revealed a strange layer in the ice at this point. It’s buried a kilometer deep, half way between the top of the ice and the ground. Their best explanation for that layer is that it’s ash, frozen in the ice sheet from a major eruption thousands of years ago.

A volcano like this can release a lot of heat. Not nearly enough to threaten the entire ice sheet, but enough to melt large amounts of the ice above it. This layer of ash suggests that about 8000 years ago, this volcano underwent a large eruption. Not as large as something like Yellowstone going off, but given the amount of ice it melted, about as large as the 1883 eruption of Krakatoa.

A hidden Krakatoa, buried under 2 kilometers of ice with no one knowing it’s there. Fascinating find.

-JBB

Image credit: Hannes Grobe/AWI http://commons.wikimedia.org/wiki/File:White-out_hg.jpg

Original paper (subscription): http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo1992.html_ _

Sky glows green in motion control timelapse and when the clouds break, a red aurora appears.

The drone view of the icecap and tiny valley glaciers coming out of this is spectacular. Narrated Iceland trip tells you the geologic story of Iceland while simultaneously exploring the landscape. Original video caption:

The oldest ice

Scientists have used ice cores to give amazing record of the earth’s atmosphere and climate over the past 800,000 years. Drill cores through the ice caps in Antarctica and Greenland give ice that is literally layered, with each layer representing a year’s snowfall. The chemistry of the snow can be used as a record of the temperature at the time it formed, and the gaps in-between ice crystals contain tiny slices of the last atmosphere the ice exchanged with.

The last atmosphere sampled in an ice core comes a little time after the snow falls, because it takes a lot of weight on top of snow to turn it to ice. That little bit of gas trapped in most ice makes the ice look white – you can even test that one in your freezer at home.

So far, scientists have had limits in the oldest ice they can recover. Once the pile of ice in a glacier gets thick enough, it spreads out and flows away. Ice at the very bottom of an ice cap also has a small extra heat source – heat flowing out of the planet Earth isn’t enough to melt much of the glacier, but it can cause the ice to recrystallize. Once these reactions happen, some of the information contained in the ice is lost, such as the yearly banding and the gas stored in the ice.

Ice that has been altered and had most of its gas removed turns blue, as seen in this beautiful image. Areas of blue ice show up in Antarctica where deep, old ice comes back to the surface. So far, scientists have mostly avoided drilling cores in these areas because they don’t have the kinds of annual bands that can tell scientists how old the ice is – ice cores aren’t useful if you don’t know how old the ice is.

However, a new technique was developed a few years ago to recognize how old ice is even if it doesn’t have annual layers. An isotope of argon gas, argon-40, builds up slowly in the Earth’s atmosphere due to radioactivity in the crust. By measuring the amount of argon-40 in blue ice, a team from Princeton was able to locate ice that was 1-million years old in 2014 (http://bit.ly/2uR5npi).

That same team, with some new grad students, traveled back to Antarctica and took 2 more drill cores from the same area. These next 2 cores were even older – 1.5 and 2.7 million years old, making them the oldest ice humans have recovered from Antarctica.

For the last 800,000 years, the planet Earth has been locked in cycles of glacial expanse and contraction. These glaciations were triggered once CO2 got low enough to allow ice sheets to expand – a drawdown in CO2 probably triggered by chemical reactions and weathering happening associated with the growth of the Himalayan mountains.

From records in the ocean, it is thought that the glaciations extend much farther back in time, several million years earlier, but we don't have records for those as precisely as we do for the ones found in ice cores. These new ice cores contain tiny bits of gas from the time they were formed, and they show similar concentrations of CO2 and other greenhouse gases to those found in the glaciations we have better records of. However, they don’t show the swings we see in the modern glaciations. This could make it more complicated for geoscientists to understand exactly what triggered the growth and collapse pattern of more recent ice sheets.

This ice also confirms that the current CO2 contents in the atmosphere of over 400 ppm are far above those that have occurred on Earth any time in the last 2.7 million years.

Antarctica has likely been glaciated for tens of millions of years, ever since CO2 levels started dropping about 30 million years ago. The team is hoping they can find ice that is more than 5 million years old somewhere at this site – that ice would predate the drop in CO2 and growth of ice sheets recorded in ocean sediments at that time. If they could find it, that ice could tell us how much the atmosphere really had to change to trigger the first ice sheets on continents other than Antarctica, which 5 million years ago had not yet begun to form.

-JBB

Image credit: Christopher Michel https://flic.kr/p/dKA9up

Press report and conference abstract: http://bit.ly/2w2Gtan http://bit.ly/2wgUBMC

Out plane window view of a valley glacier draining the Greenland Ice Cap

Dogsled team travel, Thule, Greenland

Clouds rolling off the Vatnajökull Icecap, Iceland

Greenland ice sheet softening like butter.

Scientists have been puzzling out the exact mechanisms for the accelerating glacier surges flowing off the Greenland ice sheet as it continues to melt at an unprecedented rate in the face of climate change. These surges drain ice off the cap into the sea contributing to sea level rise. As the surface melts, lakes and rivers form on the ice, eventually draining into the ice sheet through holes known as moulins or by the phenomenon of ice lake drainage captured in the documentary Chasing Ice. Scientists already suspect that this water is lubricating the bottom of the sheet, lifting it off the bedrock and causing the surges.

A study published by the American Geophysical Union has shown that the deep interiors of the sheet are also surging much faster than a decade ago, and proposes that the cause is the relative warmth of the draining water from the surface melt. This sun heated water warms the deep ice from the inside and softens it, allowing it to flow faster. Warm water carries an immense amount of latent heat, and it is well known that the oceans have absorbed much more of the extra heat energy from climate change than the atmosphere.

Researchers used satellite images to quantify the movement of ice deep inland, and determined that it is moving at 1.5 times the speed of a decade ago (from 40 to 60 metres yearly). This worrying fact shows that the surging is not just happening towards the glacial snouts as they get into the warmer air closer to sea level, but deeper in the ice cap, suggesting that further downstream acceleration is likely.

Surging so deep in the ice cap is not related to what happens as it enters the sea, but must be related to a change in the deep ice. The team modelled the effect of the warm water entering the sheet from the surface and found that the result was a close approximation of observed reality, with the iuce softening and flowing like warmed butter under its own weight. This suggests that our current models are underestimating the likely future contribution this ice cap will make to sea level rise in our warming world. Earlier models essentially inputted the sheet as a giant ice cube, without taking account of the fact that surface melt water is turning it into something more akin to Swiss cheese.

The model showed that only a couple of degrees Celsius is sufficient to produce this effect, making for disturbing thoughts when one ponders that the current estimates give us 3-6 degrees of warming by 2100. The rise in sea level may well come much faster than we hope, constraining the time that society has to respond to the challenge of evacuating so much low lying land, including many of the world's great cities.

Loz

Image credit: J. Box

http://www.agu.org/news/press/pr_archives/2013/2013-35.shtml

Only a tiny slice of humanity will ever get to explore the Greenland Ice Cap in person. Here you can travel along with photographer Paul Zizka as he documents that landscape. 

Drone ascent over cracks in the Vatnajökull ice cap, Iceland - with ash layers readily apparent.  ​