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Recent Temperature Trends of Antarctica's Western Ross Sea
Reference
Sinclair, K.E., Bertler, N.A.N. and van Ommen, T.D. 2012. Twentieth-century surface temperature trends in the Western Ross Sea, Antarctica: Evidence from a high-resolution ice core. Journal of Climate 25: 3629-3636.

Background
The authors write that "although the Antarctic ice sheet plays a pivotal role in the global ocean and atmospheric circulation systems and their response to warming climates, there are few long-term observations of surface temperature across the continent," which they say is "particularly true for areas pole-ward of the Antarctic Peninsula because of the sparsity of scientific bases and problems associated with satellite measurements of surface temperature (Mayewski et al., 2009)." Consequently, for this important part of the world, they assert that there is a "pressing need for a better understanding of climate variability and the forcings that underlie these changes."

What was done
In search of this understanding, Sinclair et al. studied isotope-temperature relationships at a site on the Whitehall Glacier in northern Victoria Land (72°54'S, 169°5'E) on a flat ice divide about 12 km from the nearest seasonally-open water. Working with an ice core drilled to a depth of 105 meters there in 2006/2007, they developed a well-calibrated isotope-temperature relationship that they used to reconstruct annual temperatures, as well as summer (December-February) and cold season (April-September) for the 125-year span of their data.

What was learned
Over the full length of their record, the three researchers say, with respect to temperatures, that they could find "no significant trends between 1882 and 2006." Neither were there any significant trends in either summer or cold season temperatures since 1958. However, they say there was "a decrease in cold season temperatures of -1.59°C 0.84°C/decade at 90% confidence (p = 0.07) since 1979," which cooling, in their words, was "coincident with a positive trend in the southern annular mode, which is linked to stronger southerly winds and increased sea ice extent and duration in the western Ross Sea," which they say "is one of the few regions experiencing a significant positive trend in sea ice and a negative trend in sea surface temperatures," citing Comiso et al. (2011).

What it means
Sinclair et al. conclude that "positive sea ice extent anomalies in the region adjacent to the Whitehall Glacier site, and cooler more vigorous meridional circulation in cooler months, may also be linked to lowered continental surface temperatures," but they indicate that additional data are required to determine the full extent of the recent cooling.

References
Comiso, J.C., Kwok, R., Martin, S. and Gordon, A.L. 2011. Variability and trends in sea ice extent and production in the Ross Sea. Journal of Geophysical Research 116: 10.1029/2010JC006391.

Mayewski, P.A., Meredith, M.P., Summerhayes, C.P., Turner, J., Worby, A., Barrett, P.J., Casassa, G., Bertler, N.A.N., Bracegirdle, T., Naveira Garabato, A.C., Bromwich, D., Campbell, H., Hamilton, G.S., Lyons, W.B., Maasch, K.A., Aoki, S., Xiao, C. and van Ommen, T. 2009. State of the Antarctic and Southern Ocean Climate System (SASOCS). Reviews of Geophysics 47: 10.1029/2007RG000231.

Reviewed 10 October 2012