Home https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ Science https://server7.kproxy.com/servlet/redirect.srv/sruj/smyrwpoii/p2/ The Antarctic Ice liked a one-two climate blow

The Antarctic Ice liked a one-two climate blow

About 15 million years ago, when Earth's atmosphere was overloaded with carbon dioxide, the oceans were heated and the ice around Antarctica disappeared, causing a significant portion of Antarctica the ice cap to melt and dramatically raise the global sea level (left). New research warns that a warming world caused by increased carbon dioxide in the atmosphere and in combination with periodic changes in the geometry of Earth's orbit may heat the oceans, leading to loss of sea ice (right) and sparking a dramatic retreat of the Antarctic sheet, raising sea levels above Worldwide. Credit: Richard Levy

Scientists have long speculated that our planet's climate system is closely linked to the Earth's celestial movements.

For example, the pacing of recent ages can be attributed to changes in the shape of our planet's orbit around the sun, and to cyclical changes in the Earth's slope on its axis and its "top-of-the-line" wobble on the axis that everyone has influence on. distribution and intensity of solar radiation.

It now turns out that variations in the axial slope – which scientists call "bias" – of the planet have significant consequences for the ascent and decline of the Antarctic ice, the deep deep carpet of ice that unlocks large amounts of water, There, if melted, will increase sea level dramatically and change the world's coastlines.

Writing this week in the journal Nature Geoscience a team led by Richard Levy of New Zealand's GNS Science and Victoria University of Wellington, and Stephen Meyers of the University of Wisconsin-Madison describe research matching the geological record of the Antarctic ice with the periodic astronomical movements of the earth. Comparing the two records, New Zealand and Wisconsin reconstruct the researchers' history of the Arctic sheet over the past 34 million years, beginning when the ice sheet first formed.

Supporting the new perspective of the Arctic sheet in Antarctica is a refined assessment of the sensitivity of the Earth's climate system to changes in bias, a powerful tool for exploring Antarctica's well-known history.

Research is important because it plays out the pattern of growth and decay of ice over geological time, including the presence of sea ice, a thin and fragile layer of frozen sea around Antarctica. A critical finding suggests that in a world heated by an increasing amount of atmospheric carbon dioxide, a loss of sea ice is likely to exacerbate the cyclical effects of the earth's bias on the ice as sea water. A loss of sea ice due to warming of the climate can cause instability of the Arctic sheet in Antarctica with serious consequences for global sea levels.

"What this study does is characterize the growth and decay of the Arctic sheet and shine on what is forcing it to change," explains Meyers, professor of geosciences UW Madison and an expert on how the climate is similar. changes in solar radiation from the Earth's astronomical movements. "What has emerged through this work and other studies is that the Antarctic ice is not only sitting there. It is vulnerable to decay."

First measured at the end of the 1950s by UW-Madison glacierologist Charles Bentley, the West Antarctic Ice Sheet alone contains enough ice to raise the sea level by approx. 5 meters. The continental ice sheet is by far the largest single mass of ice on Earth. Miles deep in places and contain more than 26 million cubic kilometers of ice. The impact is so heavy, Bentley and his colleagues discovered that much of the West Indian ice sheet is on land thousands of feet below sea level, making it a marinis in places.

Marine ice sheets, note Levy and Meyers, are particularly sensitive to heat supplied by ocean currents. Fast-flowing inner ice currents in the West Atlantic are suppressed by floating ice shelves, which – if they are reduced or lost – increase the possibility of an outflow of sea ice in the West.

The new study suggests that a reduction in sea ice is due to climate change will destroy the barrier that holds the ice – including parts of it beneath the ocean – in place.

"Havis creates a barrier between the sea and the ice. If we fail to reach carbon dioxide emissions and the Earth's average temperature heats more than 2 degrees Celsius, the sea ice will fall and we jump into a world that is similar to that last experienced in the early to mid-Miocene, "says Levy, referring to a geological era that ended about 14 million years ago when the Earth and its polar regions were much more temperate, with an atmosphere that was supercharged with carbon dioxide and global temperatures, on average, warmer at 3 to 4 degrees Celsius (7 to 9 degrees Fahrenheit). 9005] To restore the history of the ice sheet, Meyers and Levy turned to the geological records of the Antarctic and attached them to more distant seabed sediment cores containing fossil shells from microscopic organisms known as foraminifera or ancestry. The chemistry of foram shells, especially oxygen isotopes, contains a signature that documents the ebb and flow of Antarctica, Meyers explains. Forams living in the deep sea collect isotopes in their shells, and various isotopes of oxygen can provide a detailed chemical overview of the changing amounts of the Arctic sheet.

These geological records, says Levy and Meyers, suggest significant variability in the size of the Arctic sheet in Antarctica driven by predictable changes in the Earth's astronomical parameters and threshold changes at atmospheric carbon dioxide levels. Prior to this new research, why the ice-cream reacted differently to the same astronomical cycles at different times was a puzzle. Linking these cycles to a detailed chemical record suggests that elevated carbon dioxide in the atmosphere and the resulting loss of sea ice around Antarctica played a major role in enhancing the effects of changes in the Earth's astronomical movements on the durability and stability of Antarctic ice sheets.

"All of these data indicate that we need to crack and reduce our greenhouse gas emissions," says Levy, noting that 2017 and 2018 then reduced Antarctic sea ice after several decades of growth. "We don't want to lose that one."

Explore further:
The ancient Antarctic ice collapse could happen again and trigger a new global flood

More Information:
Antarctic Sheet Sensitivity to Biasing Improved Through Marine Connections, Nature Geoscience (2019). DOI: 10.1038 / s41561-018-0284-4, https://www.nature.com/articles/s41561-018-0284-4

Journal reference:

Provided by:
University of Wisconsin-Madison

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