Is Antarctica Melting?

by Tamsin Gray     Department: Earth

The short answer is yes, parts of Antarctica have certainly been melting at an accelerated rate in recent years.

But wait a minute...

As some areas of the continent warm up (as a result of recent climate change) melting increases but snow accumulation increases too. The overall Antarctic contribution to sea level rise depends on the sensitive balance between melting and accumulation. So when it comes to the question of sea level rise, the real question is: Is there more snow melting or falling?

Some areas of West Antarctica, especially the Antarctic Peninsula, could be on the verge of a major MELTDOWN.

Whilst records from stations across East Antarctica (including Halley where I'm based) show little warming, the Antarctic peninsula is one of the fastest warming regions on the planet. Over the past 50 years, annual mean temperatures have risen by nearly 6 degrees Fahrenheit. Ocean temperatures in the region have risen too, causing the break up of large ice shelves such as the sudden dissintegration of the massive Larsen-B ice shelf in 2002.

Evidence from marine sediments shows that the Larsen-B had probably been stable for at least 10,000 years prior to its dramatic break up. This suggests that recent warm temperatures are exceptional within the context of the last 10,000 years, making it unlikely that they can be explained by natural variability alone (one more piece in the jigsaw of evidence that led the Intergovernmental Panel on Climate Change (IPCC) to conclude that humans are likely to be changing the climate).

The break-up of coastal ice shelves doesn't cause sea levels to rise - the ice is already floating - but it can have a knock on effect on glaciers. Ice shelves can act as a barrier to the advance of glaciers and once they are gone, huge volumes of ice can flow freely into the ocean. The ice is helped along by another effect of the recent warming: increased melting of surface ice and snow which can flow through cracks to the base of the glacier, lubricating its flow. The result: the unprecedented advance of glaciers observed on the Antarctic Peninsula over the last decade, thought to be a major contributor to global sea level rise.

In East Antarctica, however, recent satellite surveys show the ice sheet slowly getting thicker. This is thought to be largely due to increased evaporation from the oceans due to global warming. It is sometimes reported that thickening in East Antarctica will counteract any sea level rise due to increased melting elsewhere.

That's certainly not the case in the long term as David Vaughan, a glaciologist of the British Antarctic Survey warned in a recent article in Nature:

"The thickening of the eastern ice sheet should not be seen as a long-term protection against a rise in sea level. Glaciers in West Antarctica are accelerating, releasing more and more icebergs into the sea. And the Antarctic Peninsula, which stretches towards South America, now regularly hits temperatures above 0 °C in the summer, leading to direct melting of the ice there.

What's more, snowfall over East Antarctica will not continue to increase indefinitely in a warming world. Conversely, every extra degree of temperature rise will continue to accelerate glaciers and cause more melting on the western side of Antarctica, swelling the world's oceans further." 

Tags: Antarctica, climate change, global warming, ice, sea level rise, snow

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