Seminar Schedule

Dr. Daniel H. Rothman

Monday, January 22, 2018 2:30pm

Kemper-Fox Seminar Room, 701 Keen

Thresholds of Catastrophe in the Earth System

Abstract:

Earth's carbon cycle, a loop between photosynthesis and respiration, represents metabolism at a global scale.  Mass extinction is always accompanied by disruption of the loop.  Yet the geochemical record also exhibits many such disruptions without mass extinction.  What separates extinctions from benign events?  At geologic timescales, mass extinctions are associated with perturbations of the carbon cycle that exceed a critical rate related to incomplete respiration.  At short time scales, mass extinction instead occurs when a perturbation exceeds a critical mass related to other biogeochemical processes.  A simple calculation suggests that the mass of carbon added to the oceans by human activities will exceed the critical mass by the year 2100.  What happens next?  Analysis of a two-dimensional dynamical system reveals two routes to runaway ocean acidification: via bifurcation of a stable fixed point to a stable limit cycle, or by the transient excitation of a stable fixed point (as in biophysical models of action potentials).  The latter route, which is consistent with observations, shows how modest perturbations can result in catastrophic excitations of an otherwise stable carbon cycle.

Refreshments will be served at 12:45pm

 

 


UPCOMING SPRING 2018 COLLOQUIUM


 

Date

01/08/2018

01/15/2018

01/22/2018

01/29/2018

02/05/2018

02/12/2018

02/19/2018

02/26/2018

03/05/2018

03/12/2018

03/19/2018

03/26/2018

04/02/2018

04/09/2018

04/16/2018

04/23/2018

04/30/2018

Speaker (Host)

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Dr. Daniel H. Rothman

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Affiliation

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Massachusetts Institute of Technology

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