Climate History of West Antarctica Gives Clues for the Future

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James Ross Island is located near the northern tip of the Antarctic Peninsula, in the area where a series of ice shelves have collapsed over the last two decades. Image courtesy NASA/BAS.

Fears about climate change and global warming point very firmly to the future – but scientists believe that past climate change, and the factors influencing it, are key to a better understanding of the future.

That’s one of the potential applications of a new piece of research (published in the journal Nature) that evaluates an ice core taken from the West Antarctic Peninsula.

What Are Ice Cores and What do They Tell Us?

Ice cores provide a record of snowfall and ice accumulation, and, in places where ice cover has persisted for millennia, can offer an excellent opportunity to glimpse far back into the past.

Now, scientists have drilled a 364 metre long core which provides clues to climate of West Antarctica dating as far back as 15,000 years.

The key to interpreting ice cores lies in water chemistry, which involves different isotopes of oxygen and hydrogen (which are, of course, the components of water, and thus of ice).

Isotopic chemistry is based on the fact that some isotopes are lighter than others, so that molecules containing them evaporate more easily.

When local temperatures are low, the lighter isotopes predominate in ice, and the heavier ones in water, and vice versa.

The Changing Rates of Warming in the Antarctic Peninsula

According to lead author, Dr. Robert Mulvaney, of the British Antarctic Survey, the study has provided an unprecedented climate record for an Antarctic site. “We have a highly resolved dataset taken from the ice core,” he told Decoded Science, “which is dated to within a few years in the last centuries, but at lower accuracy as we get older (but still with accuracies of around 200 years at 10,000 years).

The 15,000 year period covers the Earth’s emergence from the last ice age, and shows warming of about 6⁰C in the early stages. Subsequent warming took the temperature above the current average, and was followed by cooling, to a minimum level at around 600 years ago. These cycles, which preceded the Industrial Revolution, are naturally-induced.

Recent Evidence of Anthropogenic Warming

A core of ice was collected continuously through the James Ross Island ice cap, providing the first history of Antarctic Peninsula temperature changes since the last ice age. Image courtesy BAS

But it’s the later part of the core which is perhaps of most interest to climate scientists. Dr. Mulvaney explains that: “as warming began 600 years ago, the rate was equivalent to around 0.2°C per century, whereas the most recent 100 years was around 1.5°C per century … We cannot for certain say, of course, that the current more rapid warming is human-induced, but our suspicion is that we are seeing human-induced and natural warming adding together.”

The implications of the research will inevitably raise concerns about the collapse of the floating ice shelves adjacent to the Antarctic Peninsula in the Weddell Sea. “We also fear that if warming continues at the present rate,” warns Dr. Mulvaney, “further ice shelves in this region might be lost (including those that have likely remained stable since the last glacial period).

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