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- SW Climate
My research explores the dynamical mechanisms of the North American monsoon over the Holocene (last 10,000 years). The North American monsoon delivers half of our annual precipitation, but it is currently a feature of Southwest climate that is not well reproduced in global climate models. Thus, we do not yet know if we should prepare for major changes in the monsoon as climate changes – what if it fails, as it did in the summer of 2009 when we got only a few weeks of rain, for a number of years in a row? What does that mean for water managers and residents of the Southwest?
With those questions in mind, I am reconstructing the range of monsoon variability on a variety of timescales (interannual to millennial). I use lake sediments and cave speleothems to achieve this. Lakes respond to changes in hydrologic balance in a variety of ways (lake level, chemistry, etc), and isotopes in cave speleothems can be used to determine the winter to summer rain balance to the cave site over short (10yr) to long (100,000yr) timescales. We can use the monsoon reconstructions from these archives to better understand the response of the monsoon to changes in forcings, such as sea surface temperatures of nearby ocean basins, atmospheric conditions, El Niño, or changes in radiative forcing (increased solar insolation in the past, or increased greenhouse gas concentrations in the present). By targeting time periods in the past where we know these conditions were different than they are today, we can hope to develop more reliable projections of summer rain in the coming years to decades as these forcings change. Understanding the variability inherent in the monsoon system is critical to preparing for future changes in water availability in southern Arizona and Mexico.