• How stable is the mean state of the tropical ocean-atmosphere system (Ramanathan and Collins, 1991; Clement et al., 1996; Rind, 2003, Gu and Philander, 1995; Fedorov and Philander, 2001)?  
  
• How will increases in atmospheric greenhouse gas concentrations affect the frequency and amplitude of El Nino-Southern Oscillation (ENSO) warm and cold phase events in the 21st century (Timmerman et al., 1999; Collins, 2005)? 
  
• What are the physical mechanisms which explain long-term variability in the tropical ocean and atmospheres (Karspeck and Cane, 2002; Kushnir et al., 2002)?

Proxy paleoclimatology: Development of  high resolution proxy climate observations from regions sensitive to various phenomena of interest.  We have primarily focused on the tropics and coupled ocean-atmosphere dynamics associated with ENSO.  Thanks to support from NSF's MRI and EAR/I&F programs, a new stable isotope laboratory has recently been commissioned at the University of Maryland, Department of Geology.  We are developing paleoclimate records from tropical trees lacking annual rings, and from massive coral colonies, using high resolution, high throughput continuous flow methods.  More about the stable isotope laboratory is here.

Paleoproxy modeling:  Modeling of the processes by which environmental conditions are sensed by proxy systems, and recorded as proxy data to be measured.  With funding from NSF/P2C2 and NOAA/C2D2, we are exploring simple but realistically multivariate and/or nonlinear models for oxygen isotopic composition in tropical trees and corals; ring width and density in conifers; and exploring other important proxy systems.  We are using these models as diagnostic tools for understanding the origin of long-term variations in actual observations, and as weak constraints in paleoclimate data assimilation exercises. 

Paleoclimate reconstruction:  Validated reconstruction of  regional and global climate fields from sparse observational networks of paleoproxy data and statistical or physical models of the climate system.   Current NSF/P2C2 and NOAA/C2D2 collaborative research includes investigation of multivariate calibration, ensemble reduced space objective analysis climate field reconstruction, comparison of reconstructed fields with general circulation model output, and state space intercomparison of the results.  

Interested in paleoclimatological research opportunities?  Contact me for more information about possible student and postdoctoral projects in tropical isotope dendroclimatology, statistical reconstruction of paleoclimatic fields, process modeling of proxy data, and tropical paleoclimate dynamics.  I hold faculty or affiliate appointments, advise students and serve on committees in Geology , ESSIC,  Atmospheric Sciences and Applied Math and Scientific Computing at Maryland.  I hold adjunct positions at Lamont-Doherty and Arizona.  More info on graduate studies at UMD/Geology is here.  Learn more about my teaching interests and past and current student research projects from my online teaching portfolio.

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