Tag Archives: Cores

Study of Ice Cores Shows Low CO2 Levels During 3 Million-Year-Old Warm Period

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Exploration at Antarctica’s Allan Hills Reveals 3 Million-Year-Old Ice Cores

Credit: Austin Carter

Researchers have used ancient air bubbles trapped in a 3-million-year-old ice core to analyze atmospheric gases from the late Pliocene for the first time. This era, when global temperatures were approximately 1°C higher than today, and sea levels were 25 meters elevated, serves as a crucial reference for current climate discussions.

The results indicated that carbon dioxide and methane concentrations from this period were significantly lower than today’s levels, suggesting that Earth’s climate might be more susceptible to minor changes in atmospheric conditions than previously believed.

In various regions of Antarctica, annual snow accumulation compresses layers into ice that entraps air bubbles, allowing scientists to construct a historical atmospheric record. Last year, the Beyond EPICA team successfully extracted the oldest continuous ice record, dating back over a million years. Learn more about this significant breakthrough.

Furthermore, scientists obtained even older ice in areas where prevailing winds eroded younger layers, bringing older “blue” ice closer to the surface.

Julia Marks Peterson, a professor at Oregon State University, and her colleagues utilized this ancient ice from Allan Hills to make direct measurements of carbon dioxide and methane levels in the Pliocene atmosphere. They discovered that, around 3 million years ago, carbon dioxide was at 250 ppm and methane at 507 ppb—much lower than previously estimated. The higher temperatures of that era went hand-in-hand with a cooling phase where carbon dioxide decreased slightly, while methane remained stable.

These findings starkly contrast earlier indirect measurements, which suggested carbon dioxide levels were nearly equal to today’s 400 ppm. Direct measurements of past methane levels are not feasible, but current standards show it hovering just below the 2000 billionth mark. Explore more about methane trends.

“The results were a bit surprising,” says Marks Peterson. If validated, these findings imply that even slight variations in greenhouse gas concentrations can dramatically affect climate systems. “This could indicate that the Earth is more sensitive to changes in CO2 than we currently understand. That’s a concerning thought,” she adds, “and one that remains unanswered given our existing records.”

New evidence suggesting lower-than-expected Pliocene carbon dioxide levels raises concerns about the potential severity of future climate change, according to Christian Proistosescu from the University of Illinois at Urbana-Champaign, who was not involved in the study.

However, additional research is essential to leverage these findings in climate modeling. Tim Naish from Victoria University of Wellington emphasizes the need for caution. He remains optimistic about uncovering data that could reveal an era of even warmer Pliocene temperatures.

Thomas Chalk from the European Center for Environmental and Geoscience Research and Education asserts the accuracy of the study’s lower CO2 measurements. Yet, he cautions that ancient ice distortions complicate interpretations regarding whether these low values reflect specific climatic periods or an overall average. “It’s essential to understand what these figures truly represent, as they don’t inherently provide a temperature estimate,” he clarifies.

The research team aims to enhance the credibility of their findings by cross-referencing their results with records from the Beyond EPICA group. “This collaborative effort will deepen our understanding of climate history,” states Marks Peterson. “We eagerly anticipate the new insights they will uncover.”

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Source: www.newscientist.com

Huge Neutron Stars Could Have Cores Composed of Unconfined Quark Matter

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The core of a neutron star contains the highest density of matter in the universe. This highly compressed matter can undergo a phase transition in which nuclear matter dissolves into unconfined quark matter, releasing its constituent quarks and gluons. However, it is currently unknown whether this transition occurs inside at least some physical neutron stars. In a new study, physicists from the University of Helsinki, the University of Stavanger, the Flatiron Institute, and Columbia University quantified this possibility by combining information from astrophysical observations and theoretical calculations.

Artist's impression of a neutron star. Image credit: Sci.News.

Neutron stars are extreme astrophysical objects containing the densest matter found in the modern universe.

It has a radius of about 10 km (6 miles) and a mass of about 1.4 solar masses.

“A long-standing unresolved question concerns whether the enormous central pressure of a neutron star can compress protons and neutrons into a phase called cold quark matter. In this exotic state, individual protons and neutrons no longer exist. We don’t,” said Professor Aleksi Vuorinen of the University of Helsinki.

“The quarks and gluons that make them up are instead freed from typical color confinement and can move almost freely.”

In a new paper, Professor Vuorinen and colleagues provide the first quantitative estimate of the possibility of a core of quark matter existing inside a massive neutron star.

They showed that quark matter is almost inevitable in the most massive neutron stars, based on current astrophysical observations. The quantitative estimates they extracted put the likelihood in the 80-90% range.

For there to be a small chance that all neutron stars are composed only of nuclear matter, the change from nuclear matter to quark matter must occur through a strong primary phase similar to the phenomenon in which liquid water turns to ice. Must be a metastasis.

This type of rapid change in the properties of neutron star matter could destabilize the star in such a way that even the formation of a tiny quark matter core could cause the star to collapse into a black hole.

An artist's impression of the various layers inside a giant neutron star. The red circle represents a significant amount of quark matter core. Image credit: Jyrki Hokkanen, CSC.

“A key element in deriving the new results is a series of large-scale supercomputer calculations that utilize Bayesian inference, a branch of statistical deduction that estimates the likelihood of various model parameters through direct comparison with observed data. “, the authors explained.

“We demonstrate that the Bayesian component allows us to derive new limits on the properties of neutron star matter, approaching the so-called conformal behavior near the center of the most massive and stable neutron stars.”

Dr. Joonas Nettila from the University of Helsinki added: “It is interesting to see specifically how each new neutron star observation improves the ability to estimate the properties of the neutron star material.” .

“Being able to compare theoretical predictions with observations and constrain the possibility of quark-matter nuclei requires hundreds of supercomputers,” said Jonas Hirvonen, a doctoral student at the Flatiron Institute and Columbia University. “We had to spend tens of thousands of CPU hours.”

“We are very grateful to the Finnish Supercomputer Center CSC for providing us with all the necessary resources.”

of paper It was published in the magazine nature communications.

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E.Annara other. 2023. Strongly interacting matter exhibits unconfined behavior in massive neutron stars. Nat Commune 14, 8451; doi: 10.1038/s41467-023-44051-y

Source: www.sci.news