Abrupt Climate Change

(project web page [link], password protected)

    Unlike today, the Earth’s climate system was extremely volatile during the last ice age. Climate proxy observations from the Greenland ice core document a series of large flips between warm and cold climate states (figure 1). These events correlate with other major environmental changes throughout the globe and turned upside down traditional notions that Earth’s climate only evolves slowly. This topic is galvanizing a large cross section of the observational and modeling components of the climate research community to answer how and why these transitions occur and to assess their relevance to future climate. Now, a decade after the first documented evidence for abrupt climate change, we are still struggling to understand how the wealth of documented evidence concerning the global extent and character of these events can be explained by what we know about the physics of climate.

Research Plans

    Starting May 1st, 2004 the NSF plans to fund a three-year project entitled "An Inverse Model Study of Abrupt Climate Change" awarded to Charles Jackson (UTIG) and Olivier Marchal (WHOI). Here is a segment of the project summary:

"A leading theory of abrupt change invokes the susceptibility of the meridional overturning circulation (MOC) and zonally- and depth-integrated heat flux (F_h) in the Atlantic, to glacial meltwater discharges from northern hemisphere ice sheets. Here we propose to apply, for the first time, the techniques of ‘inverse modeling’ to the study of abrupt climate change. We will use data assimilation techniques developed in the framework of optimal control theory and Bayesian stochastic inversion, to combine the Greenland paleotemperature record and numerical models of the ocean-atmosphere system in the Atlantic (a relatively simple box model and the more complex Stocker/Wright zonally-averaged model). Our aim is to estimate the temporal evolutions of the Atlantic MOC, F_h, and surface freshwater forcing during the marine isotope stage 3 (24.1-59.0 ka BP) that are consistent with both the Greenland record and the physics embedded in the models. The estimated evolutions, in concert with paleoceanography records from Atlantic sediments, will be used to assess the adequacy of the theory to explain rapid climate change."

Opportunities for Graduate Student Involvement

   We are currently looking for a graduate student with good quantitative skills and a long-term interest in working in climate research to work with Jackson at the UT Institute for Geophysics (although this person need not be affiliated with Jackson School of Geosciences). This graduate student will be involved in all aspects of experiment design, implementation, and interpretation. For more information, please contact Charles Jackson.