Presentation on theme: "Pliocene Climate Modelling, and the onset of Northern Hemisphere Glaciation 1)The Pliocene 2)Expansion of Greenland glaciation in the Late Pliocene – uncertainties."— Presentation transcript:
Pliocene Climate Modelling, and the onset of Northern Hemisphere Glaciation 1)The Pliocene 2)Expansion of Greenland glaciation in the Late Pliocene – uncertainties. 3)Uplift and North American Pliocene glacial inception. 4)Impact of changing Cenozoic ice sheets on climate sensitivity.
From Rainer Zahn Legacy of ODP. Climate evolution - the last 5 million years
Expansion in Greenland glaciation at ~2.75 Ma Bartoli et al, EPSL, 2005
The mid-Pliocene ~3.3 – 3.0 Ma Enhanced CO 2 : Best estimate 360 – 400ppmv Reconstructions of: e.g. vegetation, ice, SST Haywood et al, Geoscientific Model Development, 2010
The mid-Pliocene represents an accessible example of a world that is similar in many respects to what models estimate could be the Earth of the late 21st Century. Taken together, the average of the warmest times during the mid-Pliocene presents a view of the equilibrium state of a globally warmer world, in which atmospheric CO2 concentrations were likely higher than pre-industrial values. Jansen et al. 2007 chapter 6, pages 440 to 442.
So, what is robust? 21% of simulations show large (>3 m) change due to CO 2 18% of simulations show small (<0.2 m) change due to CO 2 100% of simulations show a greater change due to CO 2 than any other mechanism.
Foster et al, Climate of the Past, in press Possible role for Canadian Rockies uplift?
Possible Priming mechanism for Cordilleran ice sheet. And possible explanation for non- glaciation in the low CO2 of the Miocene:
Summary Enhancement of Greenland glaciation around 2.75 Ma Many hypotheses including CO 2, Panama, Rockies, ENSO … Modelling work indicates CO 2 is primary driver, with orbital modulation. BUT, magnitude of effect is uncertain. Maybe role for Canadian Rockies uplift in determining timing of more general NH glaciation…..and non-glaciation during low CO 2 time periods
Problems / Challenges for pre-Quaternary ice sheets and climate… pre ice-core multiproxy CO 2 reconstructions Interpretation of records – proxy modelling Development and use of Earth System Models – especially with fully coupled ice sheets Proper treatment of uncertainties in modelling Can pre-quaternary data ever constrain ice sheet models?