A Dynamic Antarctic Ice Sheet in the Miocene and Pliocene: Resolving a Classic Model-Data Paradox

Abstract:

Proxy ice volume and sea-level indicators imply a highly dynamic Antarctic Ice Sheet in the Miocene and early-mid Pliocene, especially if the Northern Hemisphere is assumed to be ice-free. Until now, the presumed insensitivity of a fully developed Antarctic Ice Sheet to orbital forcing and a wide range of greenhouse gas concentrations has made Miocene and Pliocene ice volume variability difficult to reconcile. Here, we show how the inclusion of new ice-model physics, more highly resolved atmospheric models, and new ice-climate coupling techniques are reducing the strength of Antarctic Ice Sheet hysteresis, bringing data-model comparisons into better agreement. This is especially true in light of new atmospheric CO2 reconstructions hinting at concentrations higher than previous estimates. The global implications of a more dynamic Antarctic cryosphere in the Neogene will be discussed in light of its potential impact on the atmosphere and global ocean circulation.