New evidence published in Geology helps solve the mystery surrounding a collapse of the Antarctic ice sheet 23 million years ago. The surface of the East Antarctic ice sheet is so cold that models can only simulate its collapse by applying a significant climatic warming. Yet numerous lines of evidence suggest that 23 million years ago the Antarctic ice sheet decayed in size as changes in Earth's orbit around the Sun drove more subtle changes in Earth's seasons. Scientists from Cardiff University's School of Earth and Ocean Sciences analyzed fossil "foraminifera". These microscopic animals live in the ocean - on death their shells collect on the seafloor making a geological record of the past. The team found that while the ice sheet was expanding, more carbon was buried on the seafloor. Later, while the ice sheet decayed, carbon was introduced back into the oceans. It seems the subtle changes in Earth's orbit around the Sun were amplified by a positive feedback effect, most likely involving the greenhouse gas carbon dioxide. Dr. Lear said: "Understanding what caused dramatic collapses of the Antarctic ice sheet in the past is necessary to test the accuracy of current ice sheet models."
Coastline retreat via progressive failure of rocky coastal cliffs
Nick J. Rosser et al., Department of Geography, Durham University, South Road, Durham DH1 3LE, UK. First published on 3 July 2013, http://dx.doi.org/10.1130/G34371.1.
Despite much research on the many processes that erode rocky coastal cliffs, accurately predicting the nature, location and timing of coastline retreat remains challenging. This is also confounded by the apparently episodic nature of cliff failure. The dominant drivers of coastal erosion, marine and sub-aerial processes, are anticipated in future to increase, so understanding
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Geological Society of America