Retracing Antarctica’s glacial past
Whilst recent terrestrial and marine empirical insights have improved understanding of the chronology, pattern and rates of retreat of this vast ice sheet, a concerted attempt to model the deglaciation of the EISC honouring these new constraints is conspicuously lacking. Retreat of the ice sheet complex was highly asynchronous, reflecting contrasting regional sensitivities to climate forcing, oceanic influence, and internal dynamics. Most rapid retreat was experienced across the Barents Sea sector after Independent glacio-isostatic modelling constrained by an extensive inventory of relative sea-level change corroborates our ice sheet loading history of the Barents Sea sector. Subglacial conditions were predominately temperate during deglaciation, with over subglacial lakes predicted along with an extensive subglacial drainage network. Deglaciation temporarily abated during the Younger Dryas stadial at The final stage of deglaciation converged on present day ice cover around the Scandes mountains and the Barents Sea by 8. Previous article in issue.
The first impact crater found underneath the Greenland ice sheet
Share It’s a story that began more than ten years ago… In March , the Homeland Security Act set into motion what would be the single-largest government reorganization since the creation of the Department of Defense. Leveraging those authorities, ICE has become a powerful and sophisticated federal law enforcement agency. Throughout , ICE looked back at its achievements and history through a series of stories, images and milestones.
Each month focused on the events and accomplishments in one year starting with Message From the Director It’s a story that began more than ten years ago… A little more than 10 years ago, U. ICE was created based on the recognition that global threats have become more dangerous, and a new approach was needed to ensure the security of the U.
Marine ice sheet instability hypothesis and the threat of a collapse of the West Antarctic Ice Sheet. Ice shelf removal could result in grounding line retreat.
Climate at the core: Amy Dusto Like a prehistoric fly trapped in amber during dinosaurs’ days, airborne relics of Earth’s earlier climate—including dust, air bubbles, sea salts, volcanic ash, and soot from forest fires—can end up trapped in glacial ice for eons. To climate scientists, those relics tell a story about how our planet’s climate and atmosphere have changed over thousands of years.
The embedded pebbles and dingy ice tell researchers that this portion of the ice core is from the bottom of the glacier, right above bedrock. This chunk comes from the first ice core drilled at Mt. Hunter, Alaska; the core’s total length was feet. Photo by Mike Waszkiewicz. What they find out could have an impact on worldwide civilization within a few generations—especially in coastal regions.
Ice cores may reveal whether Antarctica’s western ice sheet melted fully the last time Earth’s climate warmed to the temperatures the planet is predicted to reach in the next two centuries. If it did, it’s likely to again, which would raise sea levels significantly enough to threaten many seaside cities. Unlocking ice cores’ secrets To unlock the information inside an ice core, researchers in the lab may melt or crush the sample bit by bit; each deeper layer represents a slightly earlier time in the Earth’s climate history.
PIXE analysis as a tool for dating of ice cores from the Greenland ice sheet
September 25, , Louisiana State University Researchers excavated and analyzed ancient fossilized organisms from the bottom of the ocean in Antarctica and discovered new information about an ice shelf that will inform future sea level rise predictions. Phil Bart, LSU More than 26, years ago, sea level was much lower than it is today partly because the ice sheets that jut out from the continent of Antarctica were enormous and covered by grounded ice—ice that was fully attached to the seafloor.
The ice sheets were as large as they could get and at the time, sea level was much lower because a lot of ice was sequestered on the continent. As the planet warmed, the ice sheets melted and contracted, and sea level began to rise. Their research recently published in Nature’s Scientific Reports may change today’s sea level rise predictions as Earth and its icy continent continues to warm.
The ice sheets were as large as they could get and at the time, sea level was much lower because a lot of ice was sequestered on the continent. As the planet warmed, the ice sheets melted and.
May 31, Since , scientists have reckoned the ages of many old objects by measuring the amounts of radioactive carbon they contain. New research shows, however, that some estimates based on carbon may have erred by thousands of years. It is too soon to know whether the discovery will seriously upset the estimated dates of events like the arrival of human beings in the Western Hemisphere, scientists said.
But it is already clear that the carbon method of dating will have to be recalibrated and corrected in some cases. They arrived at this conclusion by comparing age estimates obtained using two different methods – analysis of radioactive carbon in a sample and determination of the ratio of uranium to thorium in the sample. In some cases, the latter ratio appears to be a much more accurate gauge of age than the customary method of carbon dating, the scientists said. In principle, any material of plant or animal origin, including textiles, wood, bones and leather, can be dated by its content of carbon 14, a radioactive form of carbon in the environment that is incorporated by all living things.
Antarctica’s ice shelves collapsing would be the start of our problems
Burdukeiwicz It is important to realise the changes in climate towards the end of the last ice age. The history of the development of modern man falls into the most recent geological age, the Quaternary. From a climatic point of view, the quaternary can be divided into cold and warm periods. In contrast to climatically stable warm periods, the climate of the cold periods was characterised by changes from warmer to extremely cold phases. This is confirmed by the remains of hippos from deposits near the Thames.
Between the Eem and the Holocene lies the last cold period, which is here referred to as the Vistula.
Parent/Caregivers may be aware of the phenomenon of dating violence, however, it is likely they underestimate their own child’s involvement in, or vulnerability for, abusive relationships.
Ice-sheet dynamics Sampling the surface of Taku Glacier in Alaska. There is increasingly dense firn between surface snow and blue glacier ice. An ice core is a vertical column through a glacier, sampling the layers that formed through an annual cycle of snowfall and melt. At Summit Camp in Greenland, the depth is 77 m and the ice is years old; at Dome C in Antarctica the depth is 95 m and the age years. The bubbles disappear and the ice becomes more transparent.
Ice is lost at the edges of the glacier to icebergs , or to summer melting, and the overall shape of the glacier does not change much with time. These can be located using maps of the flow lines. These include soot, ash, and other types of particle from forest fires and volcanoes ; isotopes such as beryllium created by cosmic rays ; micrometeorites ; and pollen.
It can be up to about 20 m thick, and though it has scientific value for example, it may contain subglacial microbial populations ,  it often does not retain stratigraphic information.
Clam shells date when Greenland’s ice sheet was smaller
But, there’s growing evidence that as the planet heats up , these sprawling glaciers could begin flowing into the ocean at an accelerated pace, boosting sea levels not in feet — but yards. To halt the melting ice, some scientists have now proposed an ambitious geoengineering plan: As Earth’s temperature continues to rise due to human-caused global warming, it’s still not well understood how quickly the ice sheets might collapse, but the melting of these glaciers is already underway.
The last 5 Augusts have been the hottest in recorded history “The big goal would be to slow down or reverse an ice sheet collapse,” Michael Wolovick, a Princeton University geoscientist and coauthor of the geoengineering study published Thursday in The Cryosphere, said in an interview. A runaway, unstoppable flow of ice into the ocean isn’t considered an immediate threat this decade or next, but very well could be by the century’s end, or potentially sooner.
Already, though, this glacier is melting at an accelerating pace.
Cosmogenic nuclide exposure dating is a widely used method for constraining past ice sheet histories. We scrutinize a recently published data set of cosmogenic 10 Be data from erratic boulders in Norway used to constrain the deglaciation of the western Scandinavian Ice Sheet to 20 ka.
The ice sheet is currently stable due to its buttressing ice shelves and local regions where the bathymetry opposes the general trend. The figure panel opposite shows the Pine Island Glacier and Twaites ice streams, which are grounded well below sea level and drain a large proportion of West Antarctica. Their accumulation areas flow from the Transantarctic Mountains and out into the Amundsen Sea. Here, you can clearly see the difference between the West and East Antarctic ice sheets.
They are separated by the m high Transantarctic Mountains. The cross section shows how the West Antarctic Ice Sheet is grounded below sea level.
Woolly Mammoths: Evidence of Catastrophe
This is key to predicting the future rates of change of large ice masses, such as West Antarctic and Greenland ice Sheets, currently severely limited by a lack of data to underpin numerical models. The cruise surveyed and sampled material along 3 main transects in The Minch, Shetland and the North Sea areas. Coring targets in these transects were identified using primarily multibeam echo sounder and sub-bottom profiler data collected during this cruise.
Over individual cores were collected, totalling in excess of half a kilometre of core material.
Clues from a new dating technique that utilizes ancient clam shells suggest that 3, to 5, years ago Greenland’s ice sheet was the smallest it has been in the past 10, years.
Share shares Varves are the layered sediments that form when meltwater below an ice sheet routes large amounts of debris into lakes near the sheet’s edge. Like the rings of a tree, the layers of a glacial varve tell the story of each year’s conditions; a thicker layer indicates more melting, since there would have been a higher volume of water to carry the sediment. The team also compared the varves to cores from the Greenland ice sheet, whose layers contain a record of ancient atmospheric conditions.
Volcanic eruptions have been known to cool the global climate, but they can also speed up the melting of ice sheets, according to new research Testing of the layers for sulphates revealed which years experienced explosive volcanic eruptions, which tend to release large amounts of ash. Matching up the ice layers with varve layers from the same time periods, the team found that years with explosive volcanic activity corresponded to thicker varve layers, indicating more melting of the northern European ice sheet.
Dr Muschitiello and his colleagues studied a period ranging from 13, to 12, years ago, when the last ice age was transitioning into today’s warm climate. Although that eruption was relatively minor, its large ash cloud shut down air traffic across most of Europe for about a week.
View at Publisher Website: The upper end of this range, and even higher estimates, cannot be ruled out because of major uncertainties in the dynamic response of polar ice sheets to a warming climate. Here, we propose an ecological genetics approach that can provide insight into the past stability and configuration of the West Antarctic Ice Sheet WAIS. We propose independent testing of the hypothesis that a trans-Antarctic seaway occurred at the last interglacial.
The Eurasian ice sheet complex (EISC) was the third largest ice mass during the Last Glacial Maximum with a span of over km and responsible for around 20 m of eustatic sea-level lowering.
Previous research estimated that it covered much of western Canada as late as 12, years ago, but new data shows that large areas in the region were ice-free as early as 1, years earlier. This confirms that once ice sheets start to melt, they can do so very quickly. The melting of the Cordilleran Ice Sheet likely caused about 20 feet of sea level rise and big changes in ocean temperature and circulation. They mapped and dated moraines throughout western Canada using beryllium , a rare isotope of beryllium that is often used as a proxy for solar intensity.
About a thousand years later, the climate cooled again, and glaciers started to advance, then retreated as conditions warmed at the onset of the Holocene. This indicates a rapid disappearance rather than a gradual melting of the ice sheet. Reconstructing precise chronologies of past climate helps researchers establish cause and effect.
What caused the cooling is still up for debate. Creating a timeline of glacial retreat also provides insight into how the first people got to North America. Some say humans could have crossed through an opening between the ice sheets, but these new findings show that passage was likely closed until 13, years ago. This paper should serve as motivation for further studies, said Caffee. Kayla Zacharias, , kzachar purdue. Marc Caffee, , mcaffee purdue. Previous geologic evidence and numerical models indicate that the ice sheet covered much of westernmost Canada as late as