Cold and dry

Geochem. Geophys. Geosys.http://doi.org/mjd (2013)

The growth of the East Antarctic ice sheet 34 million years ago altered high-latitude atmospheric circulation patterns and led to drying over the continent, an analysis of continental weathering suggests. The growth of the ice sheet at this time was linked to a drop in atmospheric CO₂ concentrations and global temperature.

Sandra Passchier of Montclair State University, New Jersey, and colleagues used the elemental composition of sediments deposited off the coast of East Antarctica to assess the amount and type of continental weathering that occurred between 54 and 13 million years ago. By looking at which elements were specifically removed and which rocks were chemically and physically broken down, they linked the weathering regimes to broader climate patterns. The warmest and wettest conditions occurred at the beginning of the record. According to their reconstruction, temperatures then fell by over 8 °C over the next 41 million years. The greatest drop in precipitation occurred as ice volume on the continent grew 34 million years ago.

The spread of an ice sheet would have increased the reflectivity of the continent, altering the polar high pressure cell and promoting the development of northward-blowing cold and dry winds.