Brøgger Seminar Series – The Dynamic Cryosphere: A Miocene perspectivee

by Carrie Lear 
Department of Earth and Ocean Sciences, Cardiff University, UK

When? Monday 26 May, 11.15–12.00
Where? Ahlmannsalen, Geovetenskapens hus


Current sea level rise associated with melting ice sheets highlights the importance of an improved understanding of cryosphere stability. The East Antarctic ice sheet is by far the largest ice sheet on Earth, today containing the equivalent of approximately 60m sea level rise. The high altitude and polar location of its upper surface severely limits the potential for surface melt such that modelled CO2 thresholds for ice melt are far higher than those for ice growth. The problem with this apparent hysteresis effect is that the geological record contains several convincing lines of evidence for major ice sheet growth and retreat in the past that are inconsistent with the basic theory. This suggests limitations in (i) models ability to realistically capture ablation processes, (ii) constraints on the variability of past radiative forcing, (iii) geochemical proxy constraints on ice sheet growth and decay, and/or (iv) understanding of the role of less stable (e.g., Northern Hemisphere) ice sheets in the system.
Here I address issues iii and iv using new foraminiferal geochemical proxy records of seawater δ18O (an indicator for global ice volume), pCO2 and sea surface temperature. The results provide new insights into the timing of extensive Northern Hemisphere Glaciation (Plio-Pliestocene [1.88 Ma], or mid Miocene [14 Ma] onset?) as well as ice sheet dynamics in the early Miocene.

Co-sponsored by the:
Bolin Centre for Climate Research
A cooperation between Stockholm University, SMHI and KTH 


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