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Rapid Decay Indicated By Giant Cavity In Antarctic Glaciers

The melting rate on this side of the glacier is extremely high.

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A glacier is shown in a photo taken in Half Moon Bay, Antarctica, Feb. 18, 2018.
A glacier is shown in a photo taken in Half Moon Bay, Antarctica, Feb. 18, 2018. VOA

Scientists from NASA have discovered a gigantic cavity, almost 300 metres tall, growing at the bottom of the Thwaites Glacier in West Antarctica, indicating acceleration in rising global sea levels due to climate change.

The size of the cavity, at Thwaites’ bottom where ocean water could flow in and melt the glacier from below, is big enough to have contained 14 billion tonnes of ice.

Importantly, most of that ice melted over the last three years, the findings showed.

“(The size of) a cavity under a glacier plays an important role in melting,” said lead author Pietro Milillo of NASA’s Jet Propulsion Laboratory (JPL) in California.

Antarctica, Ice
The Collins glacier on King George Island has retreated in the last 10 years and shows signs of fragility, in the Antarctic, Feb. 2, 2018. VOA

“As more heat and water get under the glacier, it melts faster.”

The cavity, reported in the Science Advances journal, was revealed by ice-penetrating radar in NASA’s Operation IceBridge — an airborne campaign beginning in 2010 that studies connections between the polar regions and the global climate.

Thwaites Glacier is currently responsible for approximately 4 per cent of global sea level rise.

It holds enough ice to raise the world’s oceans a little over 2 feet and backstops neighbouring glaciers that would raise sea levels to an additional 8 feet if all the ice were lost.

Antarctica
Antarctica melting away at alarming rate: Study. Flickr

Thwaites is one of the hardest places to reach on Earth, but it is about to become better known than ever before.

The huge cavity was under the main trunk of the glacier on its western side – the side farther from the West Antarctic Peninsula.

In this region, as the tide rises and falls, the grounding line retreats and advances across a zone of about 3 to 5 km. The glacier has been coming unstuck from a ridge in the bedrock at a steady rate of about 0.6 to 0.8 km a year since 1992.

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Despite this stable rate of grounding-line retreat, the melting rate on this side of the glacier is extremely high.

These results highlighted that ice-ocean interactions were more complex than previously understood. (VOA)

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Scientists Create Map of Wind Circulation in the Upper Atmosphere of Mars

Scientists map winds in Mars' upper atmosphere for first time

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Mars
The new map of Mars winds helps scientists to better understand the workings of the Martian climate. (Representational image). Pixabay

Using data from NASA’s MAVEN spacecraft, researchers have created the first-ever map of wind circulation in the upper atmosphere of Mars.

The new map of Mars winds helps scientists to better understand the workings of the Martian climate, giving them a more accurate picture of its ancient past and its ongoing evolution.

“The observed global circulation provides critical inputs needed to constrain global atmospheric models,” said Mehdi Benna of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“These are the same models that are used to extrapolate the state of the Martian climate into the distant past,” added Benna in the first paper published in the journal Science.

MAVEN (Mars Atmosphere and Volatile EvolutioN mission) celebrated the five-year anniversary of its entrance into orbit around Mars on September 21.

Mission Mars
The winds observed in the Martian upper atmosphere are sometimes similar to what we see in global model simulations. (Representational image). Pixabay

The primary scientific goal of the mission is to study what is left of Mars’ atmosphere to determine how, in the distant past, an ocean-covered and potentially habitable Mars became the dry and desolate place it is today.

“The winds observed in the Martian upper atmosphere are sometimes similar to what we see in global model simulations, but other times can be quite different,” said Kali Roeten of University of Michigan.

“These winds can also be highly variable on the timescale of hours, yet in other cases, are consistent throughout the observation period, said Roeten in the second paper published in the Journal of Geophysical Research-Planets.

Upper atmospheric winds on Earth have already been mapped in detail.

Winds drive a series of processes in the atmosphere that can affect the propagation of radio waves, which are crucial for communications purposes for those on the surface, and the prediction of paths satellites will take in their orbit around Earth.

Mapping Martian winds, therefore, is a crucial step towards understanding characteristics of extraterrestrial atmospheres beyond what we know about processes on Earth.

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The upper atmospheric winds on both Earth and Mars are in the planets’ respective thermospheres, which are areas where temperature increases with height.

This discovery was the first detection of topography-induced gravity wave ripples in the thermosphere of any planet, even Earth. (IANS)