The Arctic cryosphere in the Mid-Pliocene and the future

• Published in: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
• Main Authors: Lunt, Daniel J, Haywood, Alan M, Foster, Gavin L, Stone, Emma J
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2008
• Subjects: Arctic; Greenland; arctic cryosphere; Climate change; Ice Sheet
• Online Access: http://dx.doi.org/10.1098/rsta.2008.0218; https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.2008.0218; https://royalsocietypublishing.org/doi/full-xml/10.1098/rsta.2008.0218

The Mid-Pliocene ( ca 3 Myr ago) was a relatively warm period, with increased atmospheric CO 2 relative to pre-industrial. It has therefore been highlighted as a possible palaeo-analogue for the future. However, changed vegetation patterns, orography and smaller ice sheets also influenced the Mid-Pliocene climate. Here, using a general circulation model and ice-sheet model, we determine the relative contribution of vegetation and soils, orography and ice, and CO 2 to the Mid-Pliocene Arctic climate and cryosphere. Compared with pre-industrial, we find that increased Mid-Pliocene CO 2 contributes 35 per cent, lower orography and ice-sheet feedbacks contribute 42 per cent, and vegetation changes contribute 23 per cent of Arctic temperature change. The simulated Mid-Pliocene Greenland ice sheet is substantially smaller than that of modern, mostly due to the higher CO 2 . However, our simulations of future climate change indicate that the same increase in CO 2 is not sufficient to melt the modern ice sheet substantially. We conclude that, although the Mid-Pliocene resembles the future in some respects, care must be taken when interpreting it as an exact analogue due to vegetation and ice-sheet feedbacks. These act to intensify Mid-Pliocene Arctic climate change, and act on a longer time scale than the century scale usually addressed in future climate prediction.