Why is Antarctica gaining ice in a warming climate?

In late 2015 NASA published a series of reports showing that Antarctica is gaining ice and given that global temperatures have been shown to be rising, why is the world’s largest area of ice gaining ice? In order to explain these findings, one must understand the geographical controls on Antarctica’s climate and that all climate systems are dynamic and complex. It is also important to note how this research demonstrates how the term ‘global warming’ can be somewhat misleading at times, and why ‘climate change’ is a much more appropriate description of what our planet is experiencing.

Antarctica is one of Earth’s great wildernesses. It is extremely large, almost twice the size of Australia, and is also has the highest average elevation of any continent on the planet. Its geographical location over the South Pole means the sun is low in the sky and hits the Earth at a low angle. This coupled with Antarctica’s immense size and elevation encourages the formation and growth of ice sheets and as these ice sheets grow they cool Antarctica even further. White surfaces such as ice reflect a higher proportion of sunlight than dark surfaces like bare rock and oceans. Consequently, as ice sheets grow, more and more solar energy is reflected back into space and cooling is increased further. This is known as the albedo feedback loop and is key in the way climate systems function and respond to change. Another consequence of Antarctica’s extreme temperatures is that it is one of the biggest deserts on Earth. This is because cold air cannot hold water vapour to the extent that warm air can and the temperatures in Antarctica make precipitation very unlikely.

Despite all of these factors, Antarctica is still unusually cold and this is because of a geological event that happened around 40 million years ago. All of the continental plates on the Earth move via a process known as plate tectonics, and 40 million years ago the southernmost peninsula of South America broke away from Antarctica. Commonly know as the opening of the Drake Passage, the end result was the formation of the Antarctic circumpolar current because the Atlantic and Pacific Oceans were no longer separated. This produced significantly cooling of Antarctica, which previous to the Drake Passage opening did not have any ice caps.

Photograph: This diagram shows the general path of the Antarctic Circumpolar current that is responsible for making Antarctica extremely cold. The white waves represents slight fluctuations in the current path called eddies. (Diagram courtesy of Los Alamos National Laboratory) / CC
Photograph: This diagram shows the general path of the Antarctic Circumpolar current that is responsible for making Antarctica extremely cold. The white waves represents slight fluctuations in the current path called eddies. (Diagram courtesy of Los Alamos National Laboratory) / CC

Antarctica demonstrates how interconnected climate and geological processes are, but the question remains: why is it gaining ice is the Earth’s climate is warming. The NASA article released about these findings shows that increased snow accumulation began roughly 10,000 years ago following the end of the last ice age. This happened because the warmer temperatures led to an increase in water vapour in the air and consequently higher levels of snowfall. According to NASA glaciologist Jay Zwally, snow accumulation is now decreasing in Antarctica, but because snow takes time to change into ice through firnification (changed by pressure), the thickening of the ice caps is still taking place today. This gain of ice is currently substantial enough outweigh the losses from Antarctica’s glaciers. Glaciers are losing mass because they are generally on the edges of the continent, which typically are warmer because of the moderation/warming effect of the oceans, whereas the main ice gains are in the coldest and highest central regions of the continent. NASA measures the changes in ice mass via various satellites and has identified that the main areas of ice gain are in the eastern and central western regions of the continent.

What this research is showing is that the ice increase in Antarctica is consequence of a post-ice age increase in snowfall that is only now finishing the process of firnification into ice. The lag-time of accumulation produced by firnification means that the gains in ice from precipitation 10,000 years ago are only being seen now. It also shows that because of the unique geography of Antarctica, the coldest areas of the continent (mainly the east) are yet to really feel the effects of rising global temperatures, whereas the western regions of Antarctica that are generally lower lying and have greater interaction with the oceans are amongst the most rapidly warming areas on the planet.

The NASA report also comments on the future of Antarctic ice flux, and in the article on published on NASA’s website the glaciologist Zwally is quoted saying:

“If the losses of the Antarctic Peninsula and parts of West Antarctica continue to increase at the same rate they’ve been increasing for the last two decades, the losses will catch up with the long-term gain in East Antarctica in 20 or 30 years — I don’t think there will be enough snowfall increase to offset these losses.”

So it would seem the conclusions that can be drawn from the recent NASA data is that it is not a contradiction to ‘global warming’, rather a demonstration of the extended process of ice cap formation, and the climatic extremity of Antarctica.

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Chris Holdsworth 8 Articles
My writing interests spawn from my studies in Earth Sciences. The natural world fascinates and amazes me, but engaging and involving others in science is my greatest passion because of the ever-growing need for interest and understanding of the natural world.

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