GeoLog

Imaggeo on Mondays

Imaggeo on Mondays: Cumulonimbus, king of clouds

Imaggeo on Mondays: Cumulonimbus, king of clouds

This wonderful mature thunderstorm cell was observed near the German Aerospace Center (DLR) Oberpfaffenhofen. A distinct anvil can be seen in the background meanwhile a new storm cell is growing in the foreground of the cumulonimbus structure. Mature storm cells like this are common in Southern Germany during the summer season. Strong heat, enough moisture, and a labile stratification of the atmosphere enables the development of this exciting weather phenomenon.

Description by Martin Köhler, as it first appeared on imaggeo.egu.eu.

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: 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/.

Imaggeo on Mondays: Bristlecone pines, some of Earth’s oldest living life forms

Imaggeo on Mondays: Bristlecone pines, some of Earth’s oldest living life forms

About 5,000 years ago, the ancient city Troy was founded, Stonehenge was under construction, and in the rugged Sierra Nevada mountain range, groves of bristlecone pine seedlings began to take root. Many of these pines are still alive today, making them the world’s oldest known living non-clonal life forms. Raphael Knevels, a PhD student from the Friedrich-Schiller-University’s Department of Geography in Jena, Germany explains why these particular species live so long.

On a field trip in the western United States, my colleagues and I traveled to various interesting spots in the beautiful and scenic diverse California. One of the most unforgettable places we visited during our trip was the Inyo National Forest in the eastern Sierra Nevada mountain range. Here, we could experience the oldest known individual living life forms on Earth: the bristlecone pines.

Scientific interest in the bristlecone pine started around 1953 with Edmund Schulman, a dendrochronologist from the University of Arizona who studied tree-rings to better understand the impact of past climate change. Schulman and his scientific team discovered many ancient trees, some older than 4,000 years. But why do bristlecone pines persist so long?

Bristlecone pines are located in the upper-mountain ranges of the Great Basin of the western United States in altitudes of 2,700 to 3,700 m. The environment is relatively arid with an annual rainfall of around 315 mm. They grow typically on limestone outcroppings that provide sparse ground cover and scarce litter, making the trees relatively safe from wildfires. Especially at high-elevation sites, the population is isolated, stands are open and productivity is low. Scientists believe that past fires in the region have been infrequent, usually small, and of low-severity, with an expected likelihood of an outbreak occurring once in 300 years. Moreover, their retention of needles for 20 to 30 years provide a kind of stable photosynthetic capacity that can carry a tree over several years of stress. Some species have even shown drought-sensitivity records in their growth-ring sequences of almost 1700 years.

With the ongoing global warming, the effects that our changing climate will have on the bristlecone pine are assumed to be severe; increasing temperatures can lead to a higher pine mortality rate and can introduce invasive weeds and lower elevation conifers. This can in turn change the composition of organic material on the soil surface, and as a result, make the region more prone to wildfire.

Generally, the ecosystem of the bristlecone pine is still not fully understood, and the tree’s longevity remains a mystery. More research must be done to better understand the pine’s relationship with its environment and create appropriate adaption strategies to manage this species within a human-introduced changing climate. On that the trees continues to be the longest-lived life forms on Earth.

By Raphael Knevels, Friedrich-Schiller-University Jena (Germany)

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: Antarctic winds make honeycomb ice

Imaggeo on Mondays: Antarctic winds make honeycomb ice

These delicate ice structures may look like frozen honeycombs from another world, but the crystalline patterns can be found 80 degrees south, in Antarctica, where they are shaped by the white continent’s windy conditions.

In Western Antarctica is a 9-kilometre line of rocky ridges, called Patriot Hills. Often cold wind furiously descends from the hills across Horseshoe Valley glacier, sculpting doily-like designs into the surface layer. “The wind exploits weaknesses in the ice structure, picking out the boundaries between individual ice crystals, leading to the formation of a honeycomb pattern,” said Helen Millman, a PhD student at the University of New South Wales Climate Change Research Centre, who captured this photograph at Patriot Hills.

Besides creating decorations out of Antarctica’s ice, the region’s intense winds, known as katabatic winds, also cause sublimation, in which the ice on the glacier’s surface turns directly into water vapour. This phenomenon creates a snow-free zone that experiences a net loss in frozen mass, also known as ablation; it also gives the ice a slightly blue hue and ”small, smooth waves that resemble the ocean in a light breeze, despite the intensity of the katabatic winds,” Millman added.

A stretch of blue ice in Antarctica. Credit: Helen Millman

“Since older ice rises as the surface layers are ablated, the ice at the surface of blue ice areas may be hundreds of thousands, or even millions of years old,” said Millman. This allows for some pretty interesting geological artifacts to reach the glacier’s surface, such as meteorites. “This conveyor belt of old ice rising to the surface means that high concentrations of meteorites can be found in blue ice areas.” Scientists can study these ancient Antarctic meteorites to learn more about the formation and evolution of our solar system. The Antarctic Search for Meteorites program for instance has collected more than 21,000 meteorites since 1976, and are on the hunt for more.

References

IceCube South Pole Neutrino Obesrvatory, University of Wisconsin-Madison

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/.