Because of its thick and extensive ice sheets, Antarctica appears to be one continuous landmass centered over Antarctica and spanning both hemispheres. The strip of the Western Hemisphere’s ice sheet is shaped like a traveler’s thumb – an apt metaphor, because the West Antarctic ice sheet is constantly moving. The ice sheet over West Antarctica is affected by rising ocean and atmospheric temperatures. It melts, flows out, and decreases in sizeAll at an amazing pace.
Much of the discussion about the melting of massive ice sheets during climate change deals with its effects on humans. This makes sense: Millions will see their homes damaged or destroyed Rising sea levels And storms.
But what will happen to Antarctica itself as the ice sheets melt?
In layers of sediment accumulated on the sea floor over millions of years, Researchers He loves we The researchers found evidence that when West Antarctica melted, there was a rapid rise in onshore geological activity in the region. the Evidence suggests what he’s hiding For the future.
A journey of discovery
30 million years ago, much of what we now call Antarctica was covered by an ice sheet. But during the Pliocene epoch, which lasted from 5.3 million to 2.6 million years ago, the West Antarctic ice sheet declined dramatically. Instead of a continuous ice sheet, all that remains are high ice caps and glaciers on or near mountaintops.
About 5 million years ago, Conditions around Antarctica are beginning to warmThe ice in West Antarctica has diminished. About 3 million years ago, the entire Earth entered a warm climate phase, similar to what occurs today.
Glaciers are not static. These large masses of ice form on land and flow seaward, moving over bedrock and removing material from the overlying landscape, carrying that debris as the ice moves, almost like a conveyor belt. This process accelerates when the climate warms, as is the case with collapse into the sea, which forms icebergs. Debris-laden icebergs can carry that continental rock material out to sea, dropping it to the sea floor as the icebergs melt.
In early 2019, we joined a big scientific expedition – International Ocean Discovery Program Expedition 379 – To the Amundsen Sea, South Pacific. Our expedition aimed to recover material from the sea floor to find out what happened in West Antarctica during its melting period since then.
Aboard the drill ship JOIDES Resolution, workers lowered a drilling operation approximately 13,000 feet (3,962 meters) to the seafloor and then drilled 2,605 feet (794 meters) into the ocean floor, just offshore from the most vulnerable part of the West Antarctic ice sheet.
The drill brought long tubes called “cores” containing layers of Sediments deposited from 6 million years ago to the present. Our research focused on fragments of sediment from the Pliocene epoch, when Antarctica was not completely covered by ice.
An unexpected discovery
While on the plane, one of us, Christine Sidaway, was surprised to discover an object Unusual sandstone pebble In a troubled section of the heart. Sandstone fragments were rare in the core, so the origin of the pebble was of great importance. Tests showed that the pebble came from deep mountains in the interior of Antarctica, about 800 miles (1,300 kilometers) from the drilling site.
For this to happen, the icebergs must have broken off from glaciers flowing from the interior mountains and then floated toward the Pacific Ocean. The pebble provided evidence of a deep-water ocean passage — not today’s thick ice sheet — through the interior of what is now Antarctica.
After the expedition, and once the researchers returned to their home laboratories, this finding was confirmed by analysis of silt, clay, rock fragments and microfossils that also appeared in the sediment core. The chemical and magnetic properties of the underlying material revealed a detailed timeline of the ice sheet’s retreat and advance over many years.
One major sign came from analyzes conducted by Keiji Horikawa. He tried to match thin clay layers in the core with underlying rocks from the continent, to test the idea that icebergs carried such material over very long distances. Each clay layer was deposited immediately after the thaw, when the ice sheet retreated, creating a layer of cobblestone clay carried by the glacier. By measuring the amounts of various elements, including strontium, neodymium and lead, he was able to do this Bonding certain thin layers of clay into the drill cores to chemical signatures in outcrops in the Ellsworth Mountains, 870 miles (1,400 km) away.
Horikawa discovered not just one instance of this material, but as many as five clay layers deposited between 4.7 million and 3.3 million years ago. This indicates that the ice sheet melted and the open ocean formed, then the ice sheet grew again and filled its interior, repeatedly, over short periods ranging from thousands to tens of thousands of years.
Create a fuller picture
Her teammate Ruthie Halberstadt combined this chemical and timing evidence into computer models explaining how this happened An archipelago of rugged, ice-covered islands emerged The ocean replaced the thick ice sheets that now fill Antarctica’s interior basins.
The biggest changes occurred along the coast. Model simulations show a rapid increase in iceberg production and a significant retreat of the ice sheet edge toward the Ellsworth Mountains. The Amundsen Sea became choked with icebergs coming from all directions. Rocks and pebbles in glaciers floated out to sea inside icebergs and fell to the sea floor as the icebergs melted.
Ancient geological evidence from Antarctica and elsewhere around the world shows that as the ice melted and flowed out of the Earth,… The earth itself rises Because the ice no longer pressures him. This shift can cause EarthquakesEspecially in West Antarctica, which lies over particularly hot areas of the Earth’s mantle High recovery rates When the ice melts on top of them.
Releasing pressure on the Earth also leads to increased volcanic activity, as happens on Earth Iceland today. Evidence for this in Antarctica comes from the layer of volcanic ash identified by Sidaway and Horikawa in the cores, which formed 3 million years ago.
Long-standing ice loss and upward movements in West Antarctica have also triggered massive rock avalanches and landslides in broken and damaged rock, forming glacial valley walls and coastal cliffs. Undersea collapses have displaced huge amounts of sediment from the marine shelf. No longer fixed in place due to the weight of the glacial ice and ocean water, huge blocks of rock broke off and rushed into the water, creating a tsunami. Unleash more coastal devastation.
The rapid onset of all these changes made the decaying West Antarctica a model of what is called “Catastrophic geology“.
The rapid rise in activity is similar to what has happened elsewhere on the planet in the past. For example, at the end of the last ice age in the Northern Hemisphere, 15,000 to 18,000 years ago, the area between Utah and British Columbia was subjected to Floods caused by the explosion of melting glacial lakesground recovery, rockslides and Increased volcanic activity. In coastal Canada and AlaskaSuch events still occur today.
Dynamic ice sheet retreat
Our team’s analysis of the chemical composition of the rocks shows that West Antarctica is not necessarily undergoing a massive, gradual transition from ice-cover to ice-free, but rather oscillates back and forth between vastly different states. Every time the ice sheet disappeared in the past, it caused geological chaos.
The future consequence for West Antarctica is that when the ice sheet next collapses, catastrophic events will return. This will happen repeatedly, as the ice sheet retreats and advances, opening and closing the connections between them Different regions of the world’s oceans.
This dynamic receptor may lead to equally rapid responses in the biosphere, e.g Algae bloom around icebergs in the oceanResulting in an influx of marine species into the newly opened sea lanes. Vast tracts of land on the islands of West Antarctica would then be opened to the growth of mossy ground cover and coastal plants that would Turning Antarctica greener than its current icy white.
Our data on the past of the Amundsen Sea and the resulting predictions suggest that land-based changes in West Antarctica will not be slow, gradual, or imperceptible from a human perspective. Rather, what happened in the past is likely to be repeated: rapid geological shifts that are felt locally as apocalyptic events such as earthquakes, explosions, landslides, and tsunamis – with global impacts.
This article was republished from Conversationan independent, non-profit news organization bringing you trustworthy facts and analysis to help you understand our complex world. Written by: Christine Sidaway, Colorado College; Anna Ruth (Ruthie) Halberstadt, University of Texas at Austinand Keiji Horikawa, Toyama University
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Christine Sidaway received funding from the U.S. Science Support Program of the IODP and the National Science Foundation (Grants 1939146 and 1917176, OPP Antarctic Earth Sciences) to support this research.
Anna Ruth Halberstadt received funding from the US Science Support Program to participate in IODP Expedition 379.
Keiji Horikawa receives funding from the JSPS KAKENHI grant (JP21H04924 and JP25H01181) to support this research.