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Imaggeo on Mondays: The ancient guard of Altai

Imaggeo on Mondays: The ancient guard of Altai

In the heart of Eurasia, an ancient stone statue overlooks the expanse of the Kurai Valley and the Altai Mountains in Russia. This relic was crafted more than a thousand years ago, sometime during the 6th or 7th century. A Turkish clan that inhabited the region, known as the First Turkic Khaganat, would often erect stones as monuments of funeral rituals.

Natalia Rudaya, who took this photograph, is a senior researcher at the Institute of Archeology and Ethnography of the Siberian Branch of the Russian Academy of Sciences. She and her research team were taking sediment cores from the bottom of Lake Teletskoye, the largest lake in the Altai Mountains, in southeastern West Siberia, close to the photograph’s location.

The lake samples give clues on how the local environment has shifted over the last couple thousand years, and how these changes might have influenced the human societies that inhabited the Altai Mountains. Investigating palaeoclimates and past vegetation shifts are also important for understanding how current climate change will affect Earth’s ecosystems.

By analysing sediment cores, Rudaya and her colleagues were able to reconstruct the region’s environmental and climatic history. Their results showed that in the beginning of the mid- to late- Holocene (roughly 4,250 years ago), the region exhibited a relatively cool and dry climate, and the land surface was dominated by Siberian pine and Siberian fir forests. However, starting around 3,900 years ago, plant populations faced significant deforestation for roughly three centuries. Then 3,600 years ago, dark coniferous mountain taiga began to extend across the territory; the sediment samples also show that this forest expansion coincided with slight increases in temperature and humidity. This climate persisted for roughly 2,000 years, then the mountainous environment faced cooler temperatures once again.

References

Rudaya, N. et al.: Quantitative reconstructions of mid- to late holocene climate and vegetation in the north-eastern altai mountains recorded in lake teletskoye, Global and Planetary Change., 141, 12-24, 2016

Huang, X. et al.: Holocene Vegetation and Climate Dynamics in the Altai Mountains and Surrounding Areas, Geophysical Research Letters, 45, 6628-6636, 2018.

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 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: Probing the Pliocene

Imaggeo on Mondays: Probing the Pliocene

The heights we go to for science…

This photograph shows a member of our team preparing to abseil down a cliff in the Charyn Canyon, in the Ili River basin of southeast Kazakhstan. The Charyn River and its tributaries, a branch of the Ili River north of the Tien Shan Mountains, have cut canyons up to 300 metres deep, carving through rocks of different geologic ages, some as old as 540 million years.

The name “Charyn” may derive from local Uighur or Turkic words for “ash tree” or “precipice” respectively, both of which are common in the area.

Charyn Canyon is presently characterized by a cold semi-arid climate, with dry summers and cold winters. However, these conditions are likely to have varied through time, becoming wetter, drier, warmer and cooler in response to major climate systems’ changing intensity and influence over the region.

Our research team investigates the past and present climate systems of the Cenozoic era, our current geological era which began 66 million years ago; the most recent 2.6 million years have been characterised by alternating ice ages and warmer so-called “interglacial” phases, and saw the evolution of humans. More specifically, we study climate systems in one of the most remote regions of Central Asia, known as the Eurasian Continental Pole of Inaccessibility. The area is a challenging place for climate research since it has no marine or ice core records, the most common calendars of ancient climate.

This region is poorly understood yet important within the global climate system, since it lies at the boundaries of the major northern hemispheric climate systems. These systems, such as the Siberian high pressure system and Asian monsoons, are likely to have shifted, expanded and contracted over time. These changes occur in response to factors like mountain uplift, and changes in the Earth’s orbital patterns and incoming solar radiation.

The aim of our study is to reconstruct climatic change over this period. By analysing various chemical and physical characteristics of the sediments, such as their age, magnetism, grain size and chemistry, we can reconstruct quantitative palaeoclimatic variability through time.

Here we focus on an 80-metre thick layer of sediment, which alternates between layers of river-transported gravels and wind-blown dust deposits, known as loess. Younger sedimentary layers have thicker dust deposits, reflecting a long-term aridification trend in the Ili Basin and, more broadly, Central Asia.

Our preliminary results from our fieldwork indicate that the canyon’s sediments represent an uninterrupted representation of the region’s climate from the Pliocene to early Pleistocene (from approximately 4.5 to 1 million years ago).

Achieving a comprehensive geological sampling of the Charyn Canyon was only possible by abseil. Our fieldwork, undertaken from May to June 2017, was a hot and dusty business, but ultimately a lot of fun. Definitely not for those with a fear of heights!

By Kathryn Fitzsimmons, Max Planck Institute for Chemistry, Germany and Giancarlo Scardia, São Paulo State University, Brazil

Light years from home – a geologist’s tale

Light years from home – a geologist’s tale

In a departure from the usual posts we feature on the blog, today Conor Purcell (a freelance science writer) brings you a thought provoking science fiction piece. Grab a drink and dive into this geology inspired adventure!

“It’s typical geology for a rocky planet” K reported. “Captured beneath the ocean at its northern pole, the core is a mix of metamorphic and sedimentary rock, with sand and fossilized organisms of the non-intelligent form. Nothing unusual.”

“We should use our new systems for this analysis,” It thought to itself. “Best to begin with a rocky planet.” K was the collective thinking entity of its group, a unified consortium of representatives now located across interstellar space: their task to find intelligent life beyond itself.

Here, on the orbiting cube, lying lengthways in front of K, and secured within the hold of the onboard core analyser, was a long cylindrical section – a core – of rock and mud which had been excavated from the planet below. K was now beginning the routine inspection performed on each of the cores acquired across the surveyed planets.

“Inspect all elements and produce time-series of environmental parameters relevant for the planet” K commanded itself.

It was then that something unusual triggered a notification in its Thought Centre – something it had never experienced. “What is this?” it asked.

For millennia, K had been searching for evidence of intelligent life on exoplanets beyond its own host star. In earlier times ground based receivers had been constructed and used to scour the endless black sky, and although life had been discovered to exist almost everywhere, without exception it took the form of mindless cellular or multicellular organisms. No trace of another Type 1 civilization had ever been found. Even as K’s technology advanced, observing and measuring the atmospheres of millions of remote planets to seek out the signatures of machine and biological life, and now even visiting those remote worlds, no sign of intelligence had yet been discovered.

What now caught the attention of K’s Thought Centre was a narrow section of fine material which appeared to have been laid down in a remarkably short period of time, during just twenty solar orbits. “This geology is unique,” K thought.

“On a planet that contains layers stacked typically over tens of thousands or millions of years, what kind of mechanism could produce such a pattern?” it asked itself. “A rapid fluvial event could produce something like this” it responded. “But not exactly: the material here is far too fine to be explained by known terrestrial, oceanic or atmospheric forces in the universe,” it thought. K could not explain it.

Far below the orbiting cube on which the analysis was being performed, over extensive distances from the poles to the equatorial belt, the K machines proceeded to core their way across the planet. For a rocky sphere of this size, two hundred cores would be drilled and sampled. The complete process would take a little over one solar orbit.

“What do we think about this anomaly?” K asked itself. “We should compute an age model for the section.”

“The section in question is relatively young, just 2.167 million solar orbits in age” it calculated. “It is wedged at the intersection between two geological epochs, marked by a large (25 degrees Kelvin) and incredibly rapid (300 years) temperature increase across the transition.”

K next extracted a sample from each of the section’s annually laid sediments and instructed itself to begin the weighing of trace elements. Chemical analysis of the ratios of isotopes would spell out a varying signal across time, detailing past temperatures and planetary ice volume. This kind of varying palaeoclimate history had been discovered on planets throughout the galaxy. It was ubiquitous.

But, amazingly, unlike the millions of geological cores previously processed, this short section presented no ordinary signal: the pattern generated by the weight of these trace elements was encrypted.

K had not seen anything like it before and inside its Thought Centre an alert was raised: no signal in the known universe had ever been found encrypted.

“Perform an analysis on the encryption, decipher, and display results,” K commanded.

“The signal has been encrypted using a very basic cypher, and can be unravelled easily.”

The deciphering took just microseconds, and right there and then the signal was laid bare, changing K’s understanding of the universe forever.

After millennia of exploration, believing it was the lone thinking entity in the universe, here was evidence conveying the existence of another intelligence, a message sublimely detailed in the universal language of mathematics. It read:

‘This was once an inhabited place which we called Earth.’

By Conor Purcell Science & Nature Writer with a PhD in Earth Science

Conor Purcell is a Science & Nature Writer with a PhD in Earth Science. He can be found on twitter @ConorPPurcell and some of his other articles at cppurcell.tumblr.com.