Insights on Antarctic climate variability from paleo-temperature proxies

Abstract:

Few direct meteorological observations exist in Antarctica, which limits our understanding of the modes of climate variability in this region. In particular, atmospheric reanalyses do not produce a coherent picture of the known warming trend since 1979. Here we analyze a suite of paleo-temperature proxies to gain insight into both the recent temperature trend and the multi-decadal climate variability in Antarctica over the last 1000 years.

We present temperature records from two sites in Antarctica: WAIS Divide (79°S, 112°W, 1766 m a.s.l), and Talos Dome (72°S, 159°E, 2315 m a.s.l), reconstructed from the combination of inert gas isotopes from the ice core and borehole temperature measurements. Borehole temperature provides an absolute estimate of long-term trends, while noble gases track decadal to centennial scale changes. In addition, we use water isotopes to infer information about circulation changes.

We find a strong warming trend in West Antarctica over the last 50 years (+0.23°C/decade), which is accelerating (+0.8°C/decade since 1980). The longer temperature record shows that such a trend has analogs happening about every 200 years. However, the study of other climate proxies suggests that the recent trend is due to a different mechanism than the previous events.

We also find a long term cooling trend over the last 1000 years, which is stronger in East Antarctica (Talos Dome) than in West Antarctica (WAIS-Divide). At WAIS Divide, we find that "Little Ice Age" cold period of 1400-1800 was 0.52°C colder than the last century. Overall, both records are consistent with the idea that the solar minima and persistent volcanic activity of the Little Ice Age (1400-1850 A.D.) had a significant impact on the surface temperature in Antarctica. The feedbacks amplifying the forcing were likely stronger on the East Antarctic plateau than on the more marine-influenced West Antarctica.