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Cryospheric Sciences

Geosciences Column: The best spots to hunt for ancient ice cores

Geosciences Column: The best spots to hunt for ancient ice cores

Where in the world can you find some of Earth’s oldest ice? That is the question a team of French and US scientists aimed to answer. They recently identified spots in East Antarctica that likely have the right conditions to harbor ice that formed 1.5 million years ago. Scientists hope that obtaining and analysing an undisturbed sample of ice this old will give them clues about Earth’s ancient climate.

The team published their findings in The Cryosphere, an open access journal of the European Geosciences Union (EGU).

Why study ancient ice?

When snow falls and covers an ice sheet, it forms a fluffy airy layer of frozen mass. Over time, this snowy layer is compacted into solid ice under the weight of new snowfall, trapping pockets of air, like amber trapping prehistoric insects. For today’s scientists, these air bubbles, some sealed off thousands to millions of years ago, are snapshots of what the Earth’s atmosphere looked like at the time these pockets were locked in ice. Researchers can tap into these bubbles to understand how the proportion of greenhouse gases in our atmosphere have changed throughout time.

As of now, the oldest ice archive available to scientists only goes back 800,000 years, according to the authors of the study. While pretty ancient, this ice record missed out on some major climate events in Earth’s recent history. Scientists are particularly interested in studying the time between 1.2 million years ago and 900,000 years ago, a period scientifically referred to as the mid-Pleistocene transition.

In the last few million years leading up to this transition, the Earth’s climate would experience a period of variation, from cold glacial periods to warmer periods, every 40,000 years. However, after the mid-Pleistocene transition, Earth’s climate cycle lengthened in time, with each period of variation occurring every 100,000 years.  

Currently, there isn’t a scientific consensus on the origin of this transition or what factors were involved. By examining old ice samples and studying the composition of the atmospheric gases present throughout this transition, scientist hope to paint a clearer picture of this influential time. “Locating a future 1.5 [million-year]-old ice drill site was identified as one of the main goals of the ice-core community,” wrote the authors of the study.  

The quest for old ice

Finding ice older than 800,000 years is difficult since the Earth’s deepest, oldest ice are the most at risk of melting due to the planet’s internal heat. Places where an ice sheet’s layers are very thick have an even greater risk of melting.

Mesh, bedrock dataset (Fretwell et al., 2013; Young et al., 2017) and basal melt rate (Passalacqua et al., 2017) used for the simulation. Credit: O. Passalacqua et al. 2018.

“If the ice thickness is too high the old ice at the bottom is getting so warm by geothermal heating that it is melted away,” said Hubertus Fischer, a climate physics researcher from the University of Bern in Switzerland not involved in the study, in an earlier EGU press release.

Last summer, a team of researchers from Princeton University announced that they had unearthed an ice core that dates back 2.7 million years, but the sample’s layers of ice aren’t in chronological order, with ice less than 800,000 years old intermingling with the older frozen strata. Rather than presenting a seamless record of Earth’s climate history, the core can only offer ‘climate snapshots.’

Finding the best of the rest

The authors of the recent The Cryosphere study used a series of criteria to guide their search for sites that likely could produce ice cores that are both old and undisturbed. They established that potential sites should of course contain ice as old as 1.5 million years, but also have a high enough resolution for scientists to study frequent changes in Earth’s climate.

Additionally, the researchers established that sites should not be prone to folding or wrinkling, as these kinds of disturbances can interfere with the order of ice layers.

Lastly, they noted that the bedrock on which the ice sheet sits should be higher than any nearby subglacial lakes, since the lake water could increase the risk of ice melt.

Magenta boxes A, B and C correspond to areas that could be considered as our best oldest-ice targets. Colored points locate possible drill sites. Credit: O. Passalacqua et al. 2018.

 

Using these criteria, the researchers evaluated one region of East Antarctica, the Dome C summit, which scientists in the past have considered a good candidate site for finding old ice. They ran three-dimensional ice flow simulations to locate parts of the region that are the most likely to contain ancient ice, based on their established parameters.

By narrowing down the list of eligible sites, the researchers were able to pinpoint regions just a few square kilometres in size where intact 1.5 million-year-old ice are very likely to be found, according to their models. Their results revealed that some promising areas are situated a little less than 40 kilometres southwest of the Dome C summit.

The researchers hope their new findings will bring scientists one step closer towards finding Earth’s ancient ice.

By Olivia Trani, EGU Communications Officer

Imaggeo on Mondays: Science in the Arctic trenches

Imaggeo on Mondays: Science in the Arctic trenches

Pictured here are climate scientists processing ice core samples in the East Greenland Ice-core Project (EastGRIP) science trench 10 m under the surface of the Greenland ice cap.

The trenches of this ice core camp require minimum building materials, utilising giant inflatable balloons that are dug in and covered with snow. The snow is left to compact for a few days, thereafter leaving back an arch-shaped underground trench ideal for ice core processing activities.

At this site, an international research consortium of ten countries led by the Center for Ice and Climate at the University of Copenhagen is aiming to retrieve an ice core from the surface of the Northeast Greenland Ice Stream, a fast-moving ribbon of ice within the Greenland Ice Sheet (GIS), all the way to the bedrock (approx. 2500 m).

Contrary to previous ice coring sites from the ice divide of the GIS, the EastGRIP site is a very dynamic place with a surface velocity of 55 m/year. Ice streams are responsible for a significant amount of the mass loss from the GIS, however their properties and behaviour are currently poorly understood. Having a better understanding of the streams’ features will allow for more accurate estimates of how the GIS accumulates and loses ice under current conditions as well as in warmer climate scenarios.

In order to understand the behavior of the site better, scientists carry out a series of state-of-the-art measurements on the ice core. They examine the physical properties and grain structure of the ice, as well as palaeoclimatic parameters, such as water isotopic ratios, gas concentrations and impurities. This research is often run by novel analytical methods that were specially developed in-house by members of this project. This constitutes a massive effort in terms of ice core sampling and measuring, a large part of which takes place in the field.

In weather-protected trenches under the surface of the snow, scientists process the ice core, part of which is measured on site. The rest of the ice is flown out of camp and distributed to laboratories around the world. The trenches provide a stable temperature environment, a feature important for the quality of the ice core sample.

By the end of the 2017 field season, the drill had reached a depth of 893 m and operations for 2018 are currently well under way. It is possible to follow the camp’s daily activities at the field diaries section here.

By Vasileios Gkinis, Center for Ice and Climate at the University of Copenhagen

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Hints of an eruption

Imaggeo on Mondays: Hints of an eruption

The photograph shows water that accumulated in a depression on the ice surface of Vatnajökull glacier in southeastern Iceland. This 700m wide and 30m deep depression [1], scientifically called an ‘ice cauldron’, is surrounded by circular crevasses on the ice surface and is located on the glacier tongue Dyngjujökull, an outlet glacier of Vatnajökull.

The photo was taken on 4 June 2016, less than 22 months after the Holuhraun eruption, which started on 29 August 2014 in the flood plain north of the Dyngjujökull glacier and this depression. The lava flow field that formed in the eruption was the largest Iceland has seen in 200 years, covering 84km2 [2] equal to the total size of Manhattan .

A number of geologic processes occurred leading up the Holuhraun eruption. For example, preceding the volcanic event, a kilometre-wide area surrounding the Bárðarbunga volcano, the source of the eruption, experienced deformation. Additionally, elevated and migrating seismicity at three to eight km beneath the glacier was observed for nearly two weeks before the eruption [3]. At the same time, seven cauldrons, like the one in this photo, were detected on the ice surface (a second water filled depression is visible in the upper right corner of the photo). They are interpreted as indicators for subglacial eruptions, since these cauldrons usually form when geothermal or volcanic activity induces ice melt at the bottom of a glacier [4].

Fracturing of the Earth’s crust led up to a small subglacial eruption at the base of the ice beneath the photographed depression on 3 September 2014. This fracturing was further suggested as the source of long-lasting ground vibrations (called volcanic tremor) [5].

My colleagues and I studied the signals that preceded and accompanied the Holuhraun eruption using GPS instruments, satellites and seismic ground vibrations recorded by an array of seismometers [2, 5]. The research was conducted through a collaboration between University College Dublin and Dublin Institute for Advanced Studies in Ireland, the Icelandic Meteorological Office and University of Iceland in Iceland, and the GeoForschungsZentrum in Germany.

The FP7-funded FutureVolc project financed the above mentioned research and further research on early-warning of eruptions and other natural hazards such as sub-glacial floods.

By Eva Eibl, researcher at the GeoForschungsZentrum

Thanks go to www.volcanoheli.is who organised this trip.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

May GeoRoundUp: the best of the Earth sciences from around the web

May GeoRoundUp: the best of the Earth sciences from around the web

Drawing inspiration from popular stories on our social media channels, as well as unique and quirky research news, this monthly column aims to bring you the best of the Earth and planetary sciences from around the web.

Major Story

This month the Earth science media has directed its attention towards a pacific island with a particularly volcanic condition. The Kilauea Volcano, an active shield volcano on the southeast corner of the Island of Hawai‘i, erupted on 3 May 2018, following a magnitude 5.0 earthquake that struck the region earlier that day.

Since the eruption, more than two dozen volcanic fissures have emerged, pouring rivers of lava onto the Earth’s surface and spurting fountains of red-hot molten more than 70 metres into the air.  As of today, Kilauea’s eruption has covered about 3534 acres (14.3 square kilometres) of the island in lava, according to the U.S. Geological Survey’s most recent estimates.

The island’s volcanic event has dealt heavy damages to the local community, forcing thousands of locals to evacuate the affected area. On 4 May, the governor of Hawaii, David Ige, declared a local state of emergency, activating military reservists from the National Guard to help with evacuations. Over the month Kilauea’s eruption has engulfed nearby neighborhoods in an oozing layer of lava, overtaking 75 homes, blocking major roads, swallowing up many vehicles, and even briefly threatening a geothermal power plant.

Kilauea’s molten rock, with temperatures at about 1,170 degrees Celsius, is an obvious danger to the local Hawaiian community (one serious injury reported so far). However, the volcanic eruption presents many airborne hazards as well.

In addition to spewing out lava, the Kilauea eruption has projected ballistic blocks, some up to 60 centimeters across, and released clouds of volcanic ash and vog (a volcanic smog of sulfur dioxide and aerosols). The ashfall and gas emissions can create hazardous conditions for travel, produce acid rain as well as cause irritation, headache and respiratory issues.

Kilauea’s lava has steadily marched towards the coast of the Big Island, and recently reached the Pacific Ocean. This interaction of molten rock and ocean water has created plumes of laze (lava haze). Laze is essentially a cloud of acidic steam, mixed with hydrochloric acid and fine particles of volcanic glass. Coming into contact with the toxic vapour can result in eye and skin irritation as well as lung damage.  

Map as of 2:00 p.m. HST, May 31, 2018. Given the dynamic nature of Kīlauea’s lower East Rift Zone eruption, with changing vent locations, fissures starting and stopping, and varying rates of lava effusion, map details shown here are accurate as of the date/time noted. Shaded purple areas indicate lava flows erupted in 1840, 1955, 1960, and 2014-2015. (Image: U.S. Geological Survey)

While residents have been fleeing the the Kilauea-affected region, many scientists have rushed to the Big Island to study the eruption. A swarm of researchers have spent the month recording lava flow activity, measuring seismicity and deformation, monitoring ash plumes by aircraft, and taking samples on foot.

Many volcano scientists have also turned to social media to answer questions from the general public about the recent eruption (like why is the eruption pink? Can you roast a marshmallow with lava?) and bust volcano myths floating online (expect no mega-tsunami from this eruption). The EGU’s own early career scientist representative for the Geochemistry, Mineralogy, Petrology & Volcanology Division, Evgenia Ilyinskaya, was invited to explain some volcano lingo on BBC News.

The volcano’s eruption has been ongoing for weeks, with no immediate end in site. Lava flows are still advancing across the region and volcanic gas emissions remain very high, says the U.S. Geological Survey’s Hawaiian Volcano Observatory. You can stay up to date with the volcano’s latest activity on the agency’s site.  

What you might have missed

A team of scientists from the PolarGAP project have found mountain ranges and three massive canyons underneath Antarctica’s ice using radar technology. These valleys play an important role in channeling ice flow from the centre of the continent towards the ocean, according to the researchers. “If Antarctica thins in a warming climate, as scientists suspect it will, then these channels could accelerate mass towards the ocean, further raising sea-levels,” reports an article from BBC News.

Also in Antarctic news, the Natural Environment Research Council (UK) and the National Science Foundation (US) have announced an ambitious plan to determine the Thwaites Glacier’s risk of collapse. The rapidly melting glacier sheds off 50 billion tons of ice a year, and if Thwaites were to completely go under, the meltwater would contribute more than 80 cm to sea level rise. “Because Thwaites drains the very center of the larger ice sheet system, if it loses enough volume, it could destabilize the rest of the entire West Antarctic Ice Sheet,” according to an article in Scientific American. The research team plans to collect various kinds of data on the glacier and use this information to predict the fate of Thwaites and West Antarctica. The $25-million (USD) joint effort will involve about 100 scientists on eight projects over the course of five years, posing to be one of the largest Antarctic research endeavors undertaken.

Meanwhile, looking out hundreds of millions of kilometres away, scientists have made an interesting discovery about one of Jupiter’s potentially habitable moons.

A team of scientists uncovered a new source of evidence that suggests Europa, one of Jupiter’s moons, may be venting plumes of water vapour above its icy exterior shell. The researchers came across this finding while re-examining data collected by NASA’s Galileo spacecraft, which performed a flyby 200 kilometres above the Europa in 1997. While running the decades old data through today’s more sophisticated computer systems, the research team found a brief, localised bend in the magnetic field, a phenomenon that is now recognised as evidence of water plume presence. These new results have made some scientists more confident that NASA’s Europa Clipper mission, set to launch by 2022, will find plumes on Jupiter’s moon.

Links we liked

The EGU Story

A 2007 paper on global climate zones published in Hydrology and Earth System Sciences, a journal of the European Geosciences Union, has been named the most cited source on Wikipedia, referenced more than 2.8 million times. The Guardian and WIRED reported this story that neither Copernicus Publications nor the Australian authors of the paper were aware of.

EGU training schools offer early career scientists specialist training opportunities they do not normally have access to in their home institutions. Up until 15 August 2018, the Union now welcomes requests for EGU support of training schools in the Earth, planetary or space sciences scheduled for 2019.

In addition, the EGU will now accept proposals for conferences on solar system and planetary processes, as well as on biochemical processes in the Earth system, in line with two new EGU conference series named in honour of two female scientists. The Angioletta Corradini and Mary Anning conferences are to be held every two years with their first editions in 2019 or 2020. The deadline to submit proposals is also 15 August 2018.

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