Klages, J. P., Hillenbrand, C.-D., Bohaty, S. M., Salzmann, U., Bickert, T., Lohmann, G., Knahl, H. S., Gierz, P., Niu, L., Titschack, J., Kuhn, G., Frederichs, T., Müller, J., Bauersachs, T., Larter, R. D., Hochmuth, K., Ehrmann, W., Nehrke, G., Rodríguez-Tovar, F. J., Schmiedl, G., Spezzaferri, S., Läufer, A., Lisker, F., van de Flierdt, T., Eisenhauer, Anton , Uenzelmann-Neben, G., Esper, O., Smith, J. A., Pälike, H., Spiegel, C., Dziadek, R., Ronge, T. A., Freudenthal, T. and Gohl, K. (2024) Ice sheet–free West Antarctica during peak early Oligocene glaciation. Science, 385 (6706). pp. 322-327. DOI 10.1126/science.adj3931.

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Abstract

One of Earth’s most fundamental climate shifts, the greenhouse-icehouse transition 34 million years ago, initiated Antarctic ice sheet buildup, influencing global climate until today. However, the extent of the ice sheet during the Early Oligocene Glacial Maximum (~33.7 to 33.2 million years ago) that immediately followed this transition—a critical knowledge gap for assessing feedbacks between permanently glaciated areas and early Cenozoic global climate reorganization—is uncertain. In this work, we present shallow-marine drilling data constraining earliest Oligocene environmental conditions on West Antarctica’s Pacific margin—a key region for understanding Antarctic ice sheet evolution. These data indicate a cool-temperate environment with mild ocean and air temperatures that prevented West Antarctic Ice Sheet formation. Climate–ice sheet modeling corroborates a highly asymmetric Antarctic ice sheet, thereby revealing its differential regional response to past and future climatic change.

Editor’s summary

Earth’s climate underwent a dramatic transition around 34 million years ago, when the Antarctic Ice Sheet first began to form, but the regional evolution of that ice sheet remains poorly defined. Klages et al . present data from marine sediments near West Antarctica showing that conditions there during the beginning of the Oligocene were mild and unfavorable to the growth of a permanent ice sheet. Model results based on those data suggest that the ice sheet in West Antarctica did not begin to form until 7 or 8 million years after the process began in East Antarctica.

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