The heat is on in West Antarctica

Eric Steig

Regular followers of RealClimate will be aware of our publication in 2009 in Nature, showing that West Antarctica — the part of the Antarctic ice sheet that is currently contributing the most to sea level rise, and which has the potential to become unstable and contribute a lot more (3 meters!) to sea level rise in the future — has been warming up for the last 50 years or so.

Our paper was met with a lot of skepticism, and not just from the usual suspects. A lot of our fellow scientists, it seems, had trouble getting over their long-held view (based only on absence of evidence) that the only place in Antarctica that was warming up was the Antarctica Peninsula. To be fair, our analysis was based on interpolation, using statistics to fill in data where it was absent, so we really hadn’t proven anything; we’d only done an analysis that pointed (strongly!) in a particular direction.

It has been a strange couple of years in limbo: we have known with certainty for at least two years that our results were basically correct, because there was a great deal of very solid corroborating evidence, including the borehole temperature data that confirmed our basic findings, and data from automatic weather stations near the center of West Antarctica that we hadn’t used, but which Andy Monaghan at Ohio State (now NCAR) had shown also corroborated our results. But most of this work was unpublished until very recently, so it wasn’t really usable information.

So it was a nice early Christmas present to see the publication of a new assessment by the well-known guru of Antarctic meteorology, David Bromwich, along with his students and colleagues at Ohio State, the University of Wisconsin (who run the U.S. automatic weather station program in Antarctica) and NCAR, which back up our results. Actually, they do more than back-up our results: they show that our estimates were too conservative and that West Antarctica is actually warming by about a factor of two more than we estimated. They also agree with the key interpretation of the results that both we and David Schneider and colleagues at NCAR have presented: that in the winter and spring seasons, when the most rapid warming is occurring in West Antarctica, the driver has been changes in the tropical Pacific, not the ozone hole (which is invoked too frequently, in my view, to explain everything from penguin populations to sea ice changes).

The borehole temperature data were published earlier this year by Orsi et al. in Geophysical Research Letters. The new temperature reconstruction of Monaghan was included as part of a paper (Küttel et al.) on ice core records in Climate Dynamics, also earlier this year; it was also included in the reconstruction in Schneider et al. 2011 in Climate Dynamics. Both showed unambiguously that West Antarctic is warming up, as fast as the Antarctic Peninsula. Bromwich et al. gets this same result again.

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