The position of the “polar front,” where cold Antarctic waters meet relatively warmer waters of the subantarctic. This reconstruction shows the likely position of the polar front during an interglacial period 3.15 million years ago (red dashed line) and other late Pliocene interglacial intervals (blue dashed line). During these warm periods, the polar front was much closer to the Antarctic continent than in the present day, while sea-ice was less extensive (area in lightest blue color). Credit: Taylor-Silva and Riesselman, 2018, Figure 5b
Source: Paleoceanography and Paleoclimatology

The late Pliocene (3.3 to 3.0 million years ago) was the most recent interval in Earth’s history when global temperatures were within the range of warming predicted for the 21st century. During this period, atmospheric carbon dioxide concentrations last reached 400 parts per million, a value we now have surpassed. Taylor-Silva and Riesselman [2018] document presence and extent of sea ice as well as a major southward migration of the Antarctic polar front during a single interglacial period (3.17 to 3.15 million years ago) within the late Pliocene, using information from diatoms, unicellular algae which form a siliceous skeleton. Global reconstructions and climate models suggest that summer sea surface temperatures were an average of more than two degrees warmer relative to the present day. The results suggest that this interglacial period is a crucial interval to test ice sheet stability in the context of anthropogenic warming.

Citation: Taylor-Silva, B. I., & Riesselman, C. R. [2018]. Polar frontal migration in the warm late Pliocene: Diatom evidence from the Wilkes Land margin, East Antarctica. Paleoceanography and Paleoclimatology, 33.

—Ellen Thomas, Editor in Chief, Paleoceanography and Paleoclimatology

Text © 2018. The authors. CC BY-NC-ND 3.0
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