We currently have several projects to look at 1) weather events and hydroclimate during the Last Glacial Maximum; 2) Miocene evolution of landscape, climate, and mammal diversity; 3) mid-Pliocene storm tracks, atmosphere river events, and southwestern North American monsoon; 4) climate response to the asteroid impact at the end-Cretaceous
Weather events and hydroclimate during the Last Glacial Maximum
Southwest North America is one of the world’s most climatically sensitive regions with inherently variable hydroclimate. Much evidence exists for repeated, large regime shifts in this region’s hydroclimate at the sub-decadal to millennial-scale during the last glacial cycle and Holocene, but the mechanisms driving this change remain uncertain. We are conducting high-resolution Earth system simulations to evaluate how North Pacific storm track behavior and the resulting precipitation signal is archived in the stalagmite proxy records, and the mechanisms underlying changes in precipitation in the context of the changing environmental forcings of the past 21,000 years (collaborating with Prof. Isabel P. Montañez at UC Davis).
Miocene evolution of landscape, climate, and mammal diversity
In the middle Miocene, a pulse of mammal diversity tracks the rate of extension within the collapsing orogen of what is now the Basin and Range province. Using constraints from the models of paleotopography and climate, we test hypotheses that relate these dramatic changes in mammal diversity to the development of large-scale gradients in topography, climate, and the removal of large topographic barriers (Collaborating with Prof. Bill Holt, and Prof. Tara Smiley at Stony Brook University, Prof. Catherine Badgley at University of Michigan).
Mid-Pliocene hurricanes, atmosphere rivers, and the North American monsoon
Recent multi-year droughts in the American Southwest highlight the need to improve predictions of southwest climate responses to rising greenhouse gases. Climate model experiments of future emissions scenarios as well as past warm intervals like the mid-Pliocene (3.0 – 3.3 Ma) predict widespread drying in response to rising greenhouse gases. However, proxy records suggest wet conditions during the Pliocene, in direct contradiction with simulations. We are carrying out a suite of high-resolution Earth system model simulations to explore mid-Pliocene changes in the North American Monsoon (NAM) as well as other fine-scale circulation features that may bring precipitation to the western North America in a warm world. (Collaborating with Prof. Tripti Bhattacharya at Syracuse University)
Earth system responses to the asteroid impact at the end-Cretaceous
Over 75% of all species went extinct across the Cretaceous-Paleogene Boundary (66 million years ago). This extinction coincided with a massive asteroid impact in the Yucatan Peninsula, which emitted gases and particles high into the atmosphere and caused widespread fires. We are using an Earth system model to simulate the climate responses to emissions of dust and sulfur from the impact and soot from fires.