Evidence for ephemeral middle Eocene to early Oligocene Greenland glacial ice and pan-Arctic sea ice
Abstract
Earth's modern climate is defined by the presence of ice at both poles. But that ice is now disappearing. Therefore understanding the origin and causes of polar ice stability is more critical than ever. Here we provide novel geochemical data that constrain past dynamics of glacial ice on Greenland and Arctic sea ice. Based on accurate source determinations of individual ice-rafted Fe-oxide grains, we find evidence for episodic glaciation of distinct source regions on Greenland as far-ranging as 68°N and 80°N synchronous with ice-rafting from circum-Arctic sources, beginning in the middle Eocene. Glacial intervals broadly coincide with reduced CO2, with a potential threshold for glacial ice stability near 500 ppmv. The middle Eocene represents the Cenozoic onset of a dynamic cryosphere, with ice in both hemispheres during transient glacials and substantial regional climate heterogeneity. A more stable cryosphere developed at the Eocene-Oligocene transition, and is now threatened by anthropogenic emissions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T43I0528T
- Keywords:
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- 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICSDE: 8155 Plate motions: general;
- TECTONOPHYSICSDE: 8177 Tectonics and climatic interactions;
- TECTONOPHYSICSDE: 8178 Tectonics and magmatism;
- TECTONOPHYSICS