Fellow, Climate Assessment for the Southwest
Sarah Truebe is a 2014 recipient of the Climate Assessment for the Southwest (CLIMAS) Climate & Society Graduate Fellows Program. Sarah is a Ph.D student in the Department of Geosciences at the University of Arizona.
Sarah's CLIMAS Fellows project:
An Assessment of Speleothem Sampling Methods for Paleoclimate Research
Abstract: Stalagmites are incomparable archives of paleoclimate information. Methods to extract past climate information from speleothems are necessarily destructive; sampling occurs along the growth axis. As the popularity of stalagmite paleoclimate science grows, development of sustainable sampling methods for these nonrenewable resources is necessary to balance the needs of science and cave conservation. Here we collect information from scientists and cave managers to develop current "best practice" guidelines for sampling. The final output will be a peer-reviewed methodology assessment, giving managers and scientists a place to start when wanting to sample in a more conservation-friendly way. Additional outputs (interpretive educational products, workshops, a stalagmite sample archive, etc.) will be developed through collaboration with stalagmite paleoclimate labs and cave/karst managers worldwide.
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 cave stalagmites (speleothems) to achieve this. Isotopes in cave speleothems can be used to determine the winter to summer rain balance to the cave site over short (30yr) to long (100,000yr) timescales. We can use monsoon reconstructions 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. Additionally, I'm investigating the methods by which paleoclimate scientists sample speleothems, as current methods are permanently destructive to speleothems. My work as a CLIMAS Climate & Society Fellow revolves around the boundary between paleoclimate science from speleothems and long-term responsible resource management. Developing methods to increase sampling sustainability will help in developing more robust climate records in the future as well.