Investigadores internacionales[{» attribute=»»>Thwaites Glacier Collaboration found that the West Antarctic Ice Sheet had been thinner in the past and had regrown, suggesting that glacial retreat could be reversed. The study used rock samples to show that ice near Thwaites Glacier was at least 35 meters thinner in the last 5000 years and took a minimum of 3000 years to reach its current size. However, this recovery timeframe poses concerns given the expected impact of sea level rise due to imminent climate change.

The West Antarctic Ice Sheet is shrinking, with many glaciers across the region retreating and melting at an alarming rate. However, this was not always the case according to new research published last month in The Cryosphere. A team of scientists from the International Thwaites Glacier Collaboration (ITGC), including two researchers from the British Antarctic Survey (BAS), discovered that the ice sheet near Thwaites Glacier was thinner in the last few thousand years than it is today. This unexpected find shows that glaciers in the region were able to regrow following earlier shrinkage.

Sea level rise is already putting millions of people in low-lying coastal communities around the world at risk from flooding. The contribution from melting Antarctic ice is currently the greatest source of uncertainty in predictions of how much and how quickly the sea level will rise in the coming decades and centuries. Together with its immediate neighbor, Thwaites Glacier currently dominates the Antarctic contribution to sea level rise. To understand how this important glacier will respond to the climate changes expected in the coming century, scientists need to know how it behaves under a wide range of climatic conditions and over long timescales. Since satellite observations only go back a few decades in time, we need to look at the geological record to find this information.

The rock cores were taken back to the lab from Thwaites for analysis. Credit: Keir Nichols (Imperial College London)

Jonathan Adams, co-author and PhD student at BAS, says:

“By studying the history of glaciers like Thwaites, we can gain valuable insight into how the Antarctic Ice Sheet may evolve in future. Records of ice sheet change from rocks that are presently exposed above the ice sheet surface end around 5000 years ago, so to find out what happened since then, we need to study rock presently buried beneath the ice sheet.”

Using drills specially designed to cut through both ice and the underlying rock, the team recovered rock samples from deep beneath the ice sheet next to Thwaites Glacier. They then measured, in those rock samples, specific atoms that are made when rocks are exposed at the surface of the Earth to radiation coming from outer space. If ice covers those rocks, these particular atoms are no longer made. Their presence can therefore reveal periods in the past when the ice sheet was smaller than the present.

Keir Nichols, a glacial geologist from Imperial College London and a lead author of the study, says:

“This was a huge team effort: several of us spent weeks away from home doing fieldwork in an extremely remote part of Antarctica, whilst others endured literally thousands of hours in the lab analyzing the rocks we collected. The atoms we measured exist only in tiny amounts in these rocks, so we were pushing right to the limit of what is currently possible and there was no guarantee it would work. We are excited that this is the first study to reveal the recent history of an ice sheet using bedrock collected from directly beneath it.”

The team discovered that the rocks they collected were not always covered by ice. Their measurements showed that, during the past 5000 years, ice near Thwaites Glacier was at least 35 meters thinner than it is now. Furthermore, their models demonstrated that its growth since then – making the ice sheet the size it is today – took at least 3000 years.
This discovery reveals that ice sheet retreat in the Thwaites Glacier region can be reversed. The challenge for scientists now is to understand the conditions required to make that possible.

Joanne Johnson, a geologist at BAS and co-author of the study, says:

“On the face of it, these results seem like good news – Thwaites Glacier was able to regrow from a smaller configuration in the geologically-recent past. However, our study shows that this recovery took more than 3000 years, in a climate that was likely not as warm as what we expect for the coming centuries. If we want to avoid the impacts of sea level rise on our world that will result from continued retreat of the West Antarctic Ice Sheet, that timescale is far longer than we can afford to wait.”

Reference: “Reversible ice sheet thinning in the Amundsen Sea Embayment during the Late Holocene” by Greg Balco, Nathan Brown, Keir Nichols, Ryan A. Venturelli, Jonathan Adams, Scott Braddock, Seth Campbell, Brent Goehring, Joanne S. Johnson, Dylan H. Rood, Klaus Wilcken, Brenda Hall and John Woodward, 28 April 2023, The Cryosphere.
DOI: 10.5194/tc-17-1787-2023

Una nueva mirada a los datos antiguos revela nuevos detalles sobre la formación galáctica.

Los astrónomos han descubierto que las burbujas eRosita, estructuras gaseosas de alta energía en el[{» attribute=»»>Milky Way, are more complex and not hotter than surrounding areas, contrary to previous assumptions. Their analysis of Suzaku satellite data suggests the bubbles originate from nuclear star-forming activity rather than a supermassive black hole.

Astronomers have revealed new evidence about the properties of the giant bubbles of high-energy gas that extend far above and below the Milky Way galaxy’s center.

In a study recently published in Nature Astronomy, a team led by scientists at The Ohio State University was able to show that the shells of these structures – dubbed “eRosita bubbles” after being found by the eRosita X-ray telescope – are more complex than previously thought.

Although they bear a striking similarity in shape to Fermi bubbles, eRosita bubbles are larger and more energetic than their counterparts. Known together as the “galactic bubbles” due to their size and location, they provide an exciting opportunity to study star formation history as well as reveal new clues about how the Milky Way came to be, said Anjali Gupta, lead author of the study and a former postdoctoral researcher at Ohio State who is now a professor of astronomy at Columbus State Community College.

These bubbles exist in the gas that surrounds galaxies, an area that is called the circumgalactic medium.

“Our goal was really to learn more about the circumgalactic medium, a place very important in understanding how our galaxy formed and evolved,” Gupta said. “A lot of the regions that we were studying happened to be in the region of the bubbles, so we wanted to see how different the bubbles are when compared to the regions which are away from the bubble.”

Previous studies had assumed that these bubbles were heated by the shock of gas as it blows outward from the galaxy, but this paper’s main findings suggest the temperature of the gas within the bubbles isn’t significantly different from the area outside of it.

“We were surprised to find that the temperature of the bubble region and out of the bubble region were the same,” said Gupta. Additionally, the study demonstrates that these bubbles are so bright because they’re filled with extremely dense gas, not because they are at hotter temperatures than the surrounding environment.

Gupta and Smita Mathur, co-author of the study and a professor of astronomy at Ohio State, did their analysis using observations made by the Suzaku satellite, a collaborative mission between NASA and the Japanese Aerospace Exploration Agency (JAXA).

By analyzing 230 archival observations made between 2005 and 2014, researchers were able to characterize the diffuse emission – the electromagnetic radiation from very low-density gas – of the galactic bubbles, as well as the other hot gases that surround them.

Although the origin of these bubbles has been debated in scientific literature, this study is the first that begins to settle it, said Mathur. As the team found an abundance of non-solar neon-oxygen and magnesium-oxygen ratios in the shells, their results strongly suggest that galactic bubbles were originally formed by nuclear star-forming activity, or the injection of energy by massive stars and other kinds of astrophysical phenomena, rather than through the activities of a supermassive black hole.

“Our data supports the theory that these bubbles are most likely formed due to intense star formation activity at the galactic center, as opposed to black hole activity occurring at the galactic center,” Mathur said. To further investigate the implications their discovery may have for other aspects of astronomy, the team hopes to use new data from other upcoming space missions to continue characterizing the properties of these bubbles, as well as work on novel ways to analyze the data they already have.

“Scientists really do need to understand the formation of the bubble structure, so by using different techniques to better our models, we’ll be able to better constrain the temperature and the emission measures that we are looking for,” said Gupta.

Reference: “Thermal and chemical properties of the eROSITA bubbles from Suzaku observations” by Anjali Gupta, Smita Mathur, Joshua Kingsbury, Sanskriti Das and Yair Krongold,1 May 2023, Nature Astronomy.
DOI: 10.1038/s41550-023-01963-5

Other co-authors were Joshua Kingsbury and Sanskriti Das of Ohio State and Yair Krongold of the National Autonomous University of Mexico. This work was supported by NASA.

MDA trabajar con Tecnología Thoth para crear una capacidad canadiense de vigilancia por radar y conocimiento del dominio espacial (SDA) en el espacio profundo. Las compañías anunciaron el miércoles un acuerdo estratégico para combinar los servicios de datos comerciales de MDA con la tecnología de radar terrestre de Thoth para la vigilancia soberana en el espacio profundo de Canadá.

Thoth tiene una tecnología de radar terrestre llamada Earthfence que puede caracterizar objetos en órbita geosincrónica (GEO), incluida una instalación de radar en el norte de Ontario. La MDA proporcionará una herramienta de plataforma basada en la web para evaluar y almacenar datos de Earthfence, y brindará una interfaz de cliente para todas las solicitudes de datos.

Las empresas dijeron que Earthfence proporciona información más precisa que los sistemas ópticos actuales y, al trabajar juntas, las empresas desarrollarán capacidades «transformadoras» en la vigilancia del espacio profundo y SDA.

“MDA actualmente opera [Canada’s] La nave espacial Sapphire del Departamento de Defensa Nacional, el único contribuyente espacial no estadounidense a la red de vigilancia espacial de EE. UU., y con este acuerdo con Thoth, estamos bien posicionados para continuar brindando capacidades críticas de conocimiento del dominio espacial que son una parte esencial de la vigilancia espacial. y seguridad espacial”, comentó el director ejecutivo de la MDA, Mike Greenley.