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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/.

Geosciences Column: The science behind snow farming

Geosciences Column: The science behind snow farming

For roughly the last decade, some ski resorts and other winter sport facilities have been using a pretty unusual method to ensure white slopes in winter. It’s called snow farming. The practice involves collecting natural or artificially made snow towards the end of winter, then storing the frozen mass in bulk over the summer under a thick layer of sawdust, woodchips, mulch, or other insulating material.

Many winter sport destinations have adopted the practice. In preparation for the 2014 Winter Olympics, Sochi, Russia stockpiled about 800,000 cubic metres of human-made snow during the warmer season, enough snow to fill 320 Olympic-size swimming pools.

Despite the growing trend, there still is little research on snow farming techniques. Recently, a team of scientists from the Institute for Snow and Avalanche Research (SLF) and the CRYOS Laboratory at the École Polytechnique Fédérale in Switzerland examined the success of snow conservation practices and used models to estimate what factors influence covered snow. Their findings were published in the EGU’s open access journal The Cryosphere.

Why store snow for the winter?

The ski industry has been storing snow for many reasons. The practice is a way for winter sports facilities to accommodate training athletes, start ski seasons earlier, and guarantee snow for major sports events. Snow farming can also be seen as a way to adapt to Earth’s changing climate, according to the authors of the study. Indeed, research published last year in The Cryosphere, found that the Alps may lose as much as 70 percent of snow cover by the end of the century if global warming continues unchecked. Snow loss to this degree could severely threaten the $70 billion dollar (57 billion EUR) industry and the alpine communities that depend on ski tourism.

For some ski resorts, the effects of climate change are already visible. For example, in Davos, Switzerland, a popular venue of the International Ski Federation Cross-Country World Cup, winter temperatures have risen over the last century while snow depth in turn has steadily declined.

Snow heap study

The research team studied two snow heaps: one near Davos, Switzerland (pictured here) and another in South Tyrol. Credit: Grünewald et al.

To better understand snow conservation techniques, the research team studied two artificially made snow heaps: one sitting near Davos and another located in South Tyrol. Each pile contained approximately 7,000 cubic metres of snow, about enough ice and powder to build 13,000 1.8-metre tall snowmen. The piles were also each covered with a 40 cm thick layer of sawdust and chipped wood.

Throughout the 2015 spring and summer season, the researchers measured changes in snow volume and density, as well as recorded the two sites’ meteorological data, including air temperature, humidity, wind speed and wind direction. The research team also fed this data to SNOWPACK, a model that simulates snow pile evolution and helps determine what environmental processes likely impacted the snow.

Cool under heat

From their observations, the researchers found that the sawdust and chipped wood layering conserved more than 75 percent of the Davos snow volume and about two thirds of the snow in South Tyrol. Given the high proportion of remaining snow, the researchers conclude that snow farming appears to be an effective tool for preparing for winter.

According to the SNOWPACK model, while sunlight was the biggest source of snow melt, most of this solar radiation was absorbed by the layer of sawdust and wood chips. The simulations suggest that the snow’s covering layer took in the sun’s heat during the day, then released this energy at night, creating a cooling effect on the snow underneath. Even more, the model found that, when the thick layer was moist, the evaporating water cooled the snow as well. The researchers estimate that only nine percent of the sun’s energy melted the snow heaps. Without the insulating layer, the snow would have melted far more rapidly, receiving 12 times as much energy from the sun if uncovered, according to the study.

Images of the South Tyrol snow heap from (a) 19 May and (b) 28 October. The snow depth (HS) is featured in c & d and snow height change (dHS) is shown in e. Credit: Grünewald et al.

The researchers found that the thickness of the covering layer was an important factor for snow conservation. When the team modelled potential snow melt under a 20 cm thick cover, the insulating and cooling effects from the layer had greatly diminished.

The simulations also revealed that, while higher air temperatures and wind speed increased snow melt, this effect was not very significant, suggesting that subalpine areas could also benefit from snow farming practices.

In the face of changing climates and disappearing snow, snow farming may be one solution for keeping winters white and skiers happy.

References

Grünewald, T., Wolfsperger, F., and Lehning, M.: Snow farming: conserving snow over the summer season, The Cryosphere, 12, 385-400, https://doi.org/10.5194/tc-12-385-2018, 2018.

Marty, C., Schlögl, S., Bavay, M., and Lehning, M.: How much can we save? Impact of different emission scenarios on future snow cover in the Alps, The Cryosphere, 11, 517-529, https://doi.org/10.5194/tc-11-517-2017, 2017.

 

 

Imaggeo on Mondays: Tongue of a small giant

Imaggeo on Mondays: Tongue of a small giant

In a world where climate change causes many mountain glaciers to shrink away, bucking the ‘melting’ trend is not easy. In today’s post, Antonello Provenzale, a researcher in Italy, tells us of one glacier in the Alps which is doing just that.

Mountain glaciers are retreating worldwide, with the possible exception of the Karakoram area. For most glaciers, ablation (ice melt) during the warm season is stronger than the accumulation of new ice by snowfall. As a result, while glacier ice flows downhill, the accelerated melting at lower elevation forces the terminus of the glacier to retreat uphill, with a net loss of ice volume.

Such behavior is especially evident on the southern flank of the Alps, where many mountain glaciers have dramatically reduced their dimensions, often fragmenting into smaller, detached pieces.

An important exception is represented by the Miage glacier in Val Veny, Val d’Aosta, northwestern Italy, at the base of the Mount Blanc massif. This glacier is covered with a thick layer of debris, which protects the underlying ice from the direct heating by sunlight. The rocks which make up the debris are poor heat conductors and thus preserve the ice beneath them, making this glacier particularly stable.

This glacier is so stationary that vegetation and trees have grown on its margins and on the debris. Several ponds punctuate the surface of the glacier, as well as some areas on its sides. The Miage lake, for example, is directly in contact with the slowly flowing ice and it is sometimes run by large outburst waves generated by huge blocks of ice and rock falling into the lake water.

This picture was taken in September 2014, during a field excursion of the Italian Glaciological Committee. The image is a composition (stitch) of several images taken with a moderate wide angle lens on a rangefinder digital camera.

By Antonello Provenzale studies Geophysical Fluid Dynamics, Earth System processes and Geosphere-Biosphere interactions at the Institute of Geosciences and Earth Resources of the National Research Council of Italy.

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/.