Current Research Projects
20th Century ENSO As Seen By Tropical CoralsMy NSF Ocean Sciences proposal addresses an outstanding problem in paleoclimate: how do we relate the variations we can measure in "proxy" records to changes in large-scale atmosphere/ocean circulation? I am looking at reconstructions made from tropical coral skeletons, where the ratio of oxygen-18 to oxygen-16 taken up by the coral as it grows is controlled by changes to temperature and the composition of the seawater the reef is sitting in. Many people have shown that these variations are related to ENSO, but since we don't have good observations of conditions right near the reef it can be hard to interpret the details of what is going on. So I am going to use an isotope-enabled global climate model, combined with a regional ocean model, to "fill in the gaps" in the observational record and see exactly how El Nino and La Nina events over the past 50 years have led to the coral "delta 18O" variations we see. I'm working with a team of senior scientists on this project: Brian Powell and Mark Merrifield at UH, Kim Cobb at Georgia Tech, and David Noone at CU.
Last Millennium Hydroclimate Variability
I am a member of the team working on the Last Millennium Ensemble project at NCAR. This is a suite of 30 different simulations of the 850-2005 period, which uses climate "forcings" from solar variability, volcanic activity, orbital changes, land use/land cover, ozone/aerosols, and all of those things combined. As part of this project, I am looking at various aspects of how Last Millennium drought in arid regions relates to the tropical oceans.
ENSO Dynamics and Climate Change
I am involved with several efforts to understand how the physics of ENSO responds to changes in climate, both natural and human-induced. I am studying how El Nino events are generated in response to tropical volcanic eruptions, as well as looking at the competing influences of greenhouse gases and anthropogenic aerosol emissions on the persistence and intensity of El Nino and La Nina events.