Holocene climate and ice-shelf history on James Ross Island

A paper in this weeks’ Nature by Mulvaney et al. 2012 suggested that the climate around the Antarctic Peninsula has varied extensively over the Holocene. This data is derived from a 363.9 m ice core from the Mount Haddington Ice Cap on James Ross Island.

Glaciers and the extent of the former Prince Gustav Ice Shelf, showing glacier extent in 2001 and 2009. From: Davies et al., 2011 (The Cryosphere).

Bubbles of air and the isotopic chemical signature of the ice from this ice core provides information on climatic fluctuations during the Holocene. The ice core indicates that the atmosphere was about 6°C cooler than present during the Last Glacial Maximum (c. 18,000 years ago).

The reduced temperature of the LGM ice at Mount Haddington suggests that the ice cap was not overrun by isotopically colder ice from further south (Mulvaney et al. 2012).

There was an early Holocene climatic optimum that was about 1.3°C warmer than present. This was followed by stable cooler conditions from 9200 to 2500 years ago, with conditions similar to present.

Mulvaney et al. 2012 found that sustained warming began on James Ross Island ~600 years ago, and perhaps suggest the absense of a Little Ice Age signature in this area that was of a comparable scale to the Little Ice Age observed in the Northern Hemisphere. Over the last 100 years, this ice core record shows warming at a rate of 1.56±0.42°C, making it the fastest rate of warming in the last 2000 years. This rate is unusual, but not outside the limits of natural variation. The recent phase of warming began in the 1920s and over the last 50 years, the rate of warming has increased to 2.6±1.2°C per century.

Mulvaney et al. conclude that the ice shelves that recently disintegrated around the Antarctic Peninsula (see here) were therefore vulnerable to collapse. If warming continues at its current rate, then temperatures will soon exceed the conditions that were prevalent throughout the Holocene.

References

Mulvaney, R., Abram, N.J., Hindmarsh, R.C.A., Arrowsmith, C., Fleet, L., Triest, J., Sime, L.C., Alemany, O. and Foord, S., 2012. Recent Antarctic Peninsula warming relative to Holocene climate and ice-shelf history. Nature, advance online publication.

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