Earth Science

A Radioactive Gas Is Lurking Beneath the Permafrost

This story was originally published by Knowable Magazine. Deep in the frozen ground of the North, a radioactive hazard has lain trapped for millennia. But the U.K. scientist Paul Glover realized some years back that it wouldn’t always be that way: One day it might get out. Glover had...
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Holocene melting of the West Antarctic Ice Sheet driven by tropical Pacific warming

The primary Antarctic contribution to modern sea-level rise is glacial discharge from the Amundsen Sea sector of the West Antarctic Ice Sheet. The main processes responsible for ice mass loss include: (1) ocean-driven melting of ice shelves by upwelling of warm water onto the continental shelf; and (2) atmospheric-driven surface melting of glaciers along the Antarctic coast. Understanding the relative influence of these processes on glacial stability is imperative to predicting sea-level rise. Employing a beryllium isotope-based reconstruction of ice-shelf history, we demonstrate that glaciers flowing into the Amundsen Sea Embayment underwent melting and retreat between 9 and 6 thousand years ago. Despite warm ocean water influence, this melting event was mainly forced by atmospheric circulation changes over continental West Antarctica, linked via a Rossby wave train to tropical Pacific Ocean warming. This millennial-scale glacial history may be used to validate contemporary ice-sheet models and improve sea-level projections.

UnDisciplined: how stable are Utah's famous red rock formations?

Rocks represent immobility, right? But wait. Geologists have documented that red rock arches and towers move in response to far off earthquakes, wind, and even ocean waves. A Utahn research team generated predictions about the stability of these structures drawing upon not only movement sensors, but also experienced mountain climbers to get to the top of these tall towers of rock.

Optically stimulated luminescence dating of ancient landscapes

Nature Reviews Earth & Environment (2022)Cite this article. From valleys carved by Ice Age glaciers across Europe, to the remains of vast lakes in the Sahara Desert, geomorphological evidence of very different past environments is everywhere. Establishing when, why and how quickly these changes occurred is important for understanding how the Earth system responds to disturbances and what they mean for the species that inhabited these past landscapes, including our ancestors. However, dating the relics of some ancient landscapes can be challenging. For instance, radiocarbon dating relies on the presence of organic material (often unsuitable in deserts where little organic material is preserved) and have a limit of only 50,000 years. Optically stimulated luminescence (OSL) dating, by contrast, allows deposition to be dated directly without the need for organic preservation.

Hidden lake may reveal what Antarctica was like before it froze

An investigation of the underside of the world’s largest ice sheet in East Antarctica has revealed a city-size lake whose sediments might contain a history of the ice sheet since its earliest beginnings. That would answer questions about what Antarctica was like before it froze, how climate change has...

Submarine metalliferous carbonate mounds in the Cambrian of the Baltoscandian Basin induced by vent networks and water column stratification

Two massive precipitation events of polymetallic ore deposits, encrusted by a mixture of authigenic carbonates, are documented from the Cambrian of the semi-enclosed Baltoscandian Basin. δ34S ("’9.33 to "’2.08"°) and δ33S ("’4.75 to "’1.06"°) values from the basal sulphide breccias, sourced from contemporaneous Pb"“Zn"“Fe-bearing vein stockworks, reflect sulphide derived from both microbial and abiotic sulphate reduction. Submarine metalliferous deposits were triggered by non-buoyant hydrothermal plumes: plumes of buoyant fluid were trapped by water column stratification because their buoyancy with respect to the environment reversed, fluids became heavier than their surroundings and gravitational forces brought them to a halt, spreading out laterally from originating vents and resulting in the lateral dispersion of effluents and sulphide particle settling. Subsequently, polymetallic exhalites were sealed by carbonate crusts displaying three generations of ikaite-to-aragonite palisade crystals, now recrystallized to calcite and subsidiary vaterite. Th of fluid inclusions in early calcite crystals, ranging from 65 to 78 ºC, provide minimum entrapment temperatures for carbonate precipitation and early recrystallization. δ13Ccarb ("’1.1 to"‰+"‰1.6"°) and δ18Ocarb ("’7.6 to "’6.5"°) values are higher than those preserved in contemporaneous glendonite concretions ("’8.5 to "’4.7"° and "’12.4 to "’9.1"°, respectively) embedded in kerogenous shales, the latter related to thermal degradation of organic matter. Hydrothermal discharges graded from highly reduced, acidic, metalliferous, and hot (~"‰150 ºC) to slightly alkaline, calcium-rich and warm (<"‰100 ºC), controlling the precipitation of authigenic carbonates.

Scientists reveal different water isotope concentrations in precipitation observations across Brazil's diverse climate

An isotope of a chemical element contains the same number of protons in the center of its atom, but when compared to another atom, the number of neutrons is different. Regarding water, some hydrogen and oxygen atoms within water molecules contain different number of neutrons, resulting in water isotopes. Because of the wide range of interactions that water molecules within precipitation can have with the surrounding atmosphere, research collaborators from Brazil and the United States have come together to gain a better understanding of the different isotopes of water that naturally occur within precipitation.

3D models reveal how seismic waves move through Earth

On a sunny morning in September 1985, a massive earthquake killed more than 9,000 people in Mexico City, even though the epicenter of the earthquake was some 200 miles away. The worst damage happened in the city itself—in part, because Mexico City is built on an ancient basin surrounded by mountains. The soft foundation is thought to have amplified the shaking, causing seismic waves to ricochet through the ground.

Kilometer-scale structure on the core"“mantle boundary near Hawaii

The lowermost mantle right above the core-mantle boundary is highly heterogeneous containing multiple poorly understood seismic features. The smallest but most extreme heterogeneities yet observed are 'Ultra-Low Velocity Zones' (ULVZ). We exploit seismic shear waves that diffract along the core-mantle boundary to provide new insight into these enigmatic structures. We measure a rare core-diffracted signal refracted by a ULVZ at the base of the Hawaiian mantle plume at unprecedentedly high frequencies. This signal shows remarkably longer time delays at higher compared to lower frequencies, indicating a pronounced internal variability inside the ULVZ. Utilizing the latest computational advances in 3D waveform modeling, here we show that we are able to model this high-frequency signal and constrain high-resolution ULVZ structure on the scale of kilometers, for the first time. This new observation suggests a chemically distinct ULVZ with increasing iron content towards the core-mantle boundary, which has implications for Earth's early evolutionary history and core-mantle interaction.

Pore structure evolution in andesite rocks induced by freeze"“thaw cycles examined by non-destructive methods

In this paper, we compare the values of petrophysical properties before and after 100 freeze"“thaw (F"“T) cycles, as well as recorded length change behaviour and temperature development on a vacuum-saturated fractured andesite rock sample taken from the Babina Quarry in Slovakia using a specially-constructed thermodilatometer, VLAP 04, equipped with two HIRT-LVDT sensors. We also used non-destructive visualization of the rock pore network by µCT imaging in order to study the development of the pore structure and fracture network in pyroxene andesites during the freeze"“thaw process. The results show that the andesite rock samples, due to good fabric cohesion, low porosity, and low pore interconnection, showed good resistance against frost-induced damage. However, it must be stated that the main process causing disintegration of this type of rock is fracture opening, which is caused by internal stresses induced by water"“ice phase transition. The overall residual strain recorded after 100 F"“T cycles was not significant, however, the increase of 31 pp in volume of the fracture showed us that repeated freezing and thawing can lead to long term deterioration in terms of subcritical crack growth in brittle-elastic solids like pyroxene-andesite rocks.

Spatio-temporal evolution and driving factors of carbon storage in the Western Sichuan Plateau

The carbon sequestration function of the ecosystem is one of the most important functions of ecosystem service, and it of great significance to study the spatio-temporal differentiation of carbon storage for promoting regional sustainable development. Ecosystems on the Western Sichuan Plateau are highly variable, but its spatio-temporal differentiation and driving factors are not yet clear. In this study, on the basis of land use monitoring data, meteorological and demographic data interpreted from Landsat remote sensing image, and through GIS analysis tools, the carbon storage module of InVEST (Integrated Valuation of Ecosystem Services and Trade-offs) model was used to estimate carbon storage and geodetector was used to detect the driving factors of carbon storage spatial differentiation. The results show that: (1) The carbon storage increased to 1.2455"‰Ã—"‰1010 t from 1.2438"‰Ã—"‰1010 t in the past 20 years, the ecosystem developed in a healthy way overall. (2) Carbon storage show High-High and Low-Low aggregation characteristics, but the area decreased by 1481.81 km2 and 311.11 km2 respectively, and the spatial cluster effect gradually weakened. (3) HAI is the leading factor causing the spatio-temporal differentiation of regional carbon storage, followed by temperature and NDVI; the interaction between factors significantly enhances the spatial differentiation of carbon storage, indicating that the change of carbon storage is the result of the joint action of natural and socioeconomic factors. The results of the study provide some theoretical basis for the development of differentiated ecological regulation models and strategies, and help to promote high-quality regional development.

Sea level along the world's coastlines can be measured by a network of virtual altimetry stations

Communications Earth & Environment volume 3, Article number: 117 (2022) Cite this article. For nearly 30 years, space-based radar altimetry has been routinely measuring changes in sea level at global and regional scales. But this technique designed for the open ocean does not provide reliable sea level data within 20"‰km to the coast, mostly due to land contamination within the radar echo in the vicinity of the coast. This problem can now be overcome through dedicated reprocessing, allowing the retrieval of valid sea level data in the 0-20"‰km band from the coast, and then the access to novel information on sea level change in the world coastal zones. Here we present sea level anomalies and associated coastal sea level trends at 756 altimetry-based virtual coastal stations located along the coasts of North and South America, Northeast Atlantic, Mediterranean Sea, Africa, North Indian Ocean, Asia and Australia. This new dataset, derived from the reprocessing of high-resolution (300"‰m) along-track altimetry data from the Jason-1, 2 and 3 missions from January 2002 to December 2019, allows the analysis of the decadal evolution of coastal sea level and fills the coastal gap where sparse sea level information is currently available.

Antarctica: Sea Ice Can Control Stability of Antarctic Ice Sheet

Antarctica has been one of the key interests when it comes to the field of glaciology, especially during the rapid ice melting phenomenon in many parts of the icy continent since the 1950s. Glaciologists and other scientists have long thought that this trend will likely continue in the coming years.