Recent Antarctic temperature rise `unusual but not unique`

The Antarctic Peninsula, the rugged protrusion extending towards South America, is one of the most rapidly warming places on the planet.

London: The Antarctic Peninsula, the rugged protrusion extending towards South America, is one of the most rapidly warming places on the planet.
According to the British Antarctic Survey (BAS), ice equivalent to 1,000 years of British domestic water consumption has been lost over the past half century.

Though the recent temperature rise at the region and associated ice loss is unusual, it`s not unprecedented, a new research has revealed.

Analysis of a 364m-long ice core containing several millennia of climate history shows Antarctic Peninsula previously basked in temperatures slightly higher than today.

However, the study warned that the peninsula is now warming rapidly, threatening previously stable areas of ice.

To determine whether this modern warming is extraordinary, BAS researchers drilled and analysed an ice core from James Ross Island (JRI). The site was chosen because of its proximity to recent ice shelf collapses.

An ice core - formed by compaction of previous snowfalls - constitutes a historical record of the local climate and atmosphere stretching back over thousands of years.

The JRI ice core, taken in the Antarctic summer of 2008, contained in total about 50,000 years of climate history.

Entombed within the ice core were quantities of a tell-tale type, or isotope, of hydrogen called deuterium.

Atoms of deuterium contain a neutron, whereas “normal” hydrogen atoms do not.

By measuring the ratio of “normal” hydrogen to the heavier deuterium, Dr Robert Mulvaney and his team were able to make a detailed reconstruction of temperatures spanning the last 15,000 years.

The analysis revealed that 15,000-12,000 years ago, the Antarctic Peninsula experienced significant warming, becoming about 1C warmer than today.

The region then cooled markedly around 2,500 years ago, and temperatures remained relatively stable. This co-incided with the late-Holocene development of ice shelves near JRI.

Around 600 years ago, the peninsula started to warm once more - slowly at first, but then, from around 1920, much more rapidly.

Average temperatures change slowly - at a rate of roughly 0.1-0.2C per century.

But the research showed that the recent rate of change in the peninsula has been considerably faster.

Prof Eric Steig from the University of Washington in Seattle has reported similar changes in West Antarctica.

“A fingerprint of forced climate change - that is, anthropogenic (man-made) forcing of climate by greenhouse gases - is that it will warm in most places at the same time. And that`s clearly the fingerprint that we are seeing,” ProfSteig told BBC News.

The work is reported in Nature journal.