GEOTHERMAL IN PORTLAND, OREGON
I recently worked with a large, multi-disciplinary team to investigate a novel application of geothermal for heating buildings in the Portland Metro area. This project looked at the ability of relatively deep aquifers in the Portland Basin to store summer heat for usage in the winter. It was funded by the Department of Energy and is summarized in a conference paper.
THE EVOLUTION OF STABLE ISOTOPES IN WATER
Stable isotopes (δ18O and δD) in water have been used extensively to understand changes in climate and topography through time. There is an inverse relationship between the isotopic composition of precipitation and elevation on the windward side of mountain ranges such as the Cascades, Himalaya, and Andes. Here is a plot of δ18O and elevation for modern surface water up the eastern flank of the Andes (eastern Cordillera) showing this relationship (Bershaw et al., 2010).
PALEOALTIMETRY
Because certain rocks and minerals are thought to preserve paleo-water chemistry, the paleoelevation of these ranges can be estimated. I continue to be involved in research that looks at the isotopic composition of paleowater using proxies like sedimentary carbonates, fossil teeth, and volcanic glass. Here are results from one of many fossil teeth that suggest the Altiplano underwent significant surface uplift between ~25 Ma and ~10 Ma (Bershaw et al., 2010).
VOLCANIC ASH FROM THE CASCADES
With students at Portland State University, I am looking at the isotopic composition of volcanic glass from tuff collected throughout Oregon to constrain the topographic evolution of the Cascades (Bershaw et al., 2019). The timing and spatial distribution of volcanism and associated topography are key inputs into geodynamic models that help us understand the tectonic evolution of the Earth. Here's a talk I gave on this subject at GSOC.
MODERN WATER ISOTOPES IN CONTINENTAL INTERIORS
I am also studying modern water isotopes in more arid and continental environments to test how paleoaltimetry can be applied to regions where atmospheric processes other than orographic precipitation (elevation) are significant. For example, on both the Tibetan Plateau and Altiplano, we found that surface water recycling accounts for significant changes in surface water chemistry, obscuring the isotope-elevation relationship (Bershaw et al., 2016; Bershaw et al., 2012).
I was recently focused on the Tian Shan (Sky Mountains) in central Asia, which also lack an isotope-elevation relationship typical of mountain ranges elsewhere (see location map). This appears to be due to seasonal variations in precipitation with altitude.
I also work with students to distinguish between the effects of temperature and evaporation on water isotopes, a challenge in continental environments where aridity and air mass mixing may significantly affect water chemistry. This is accomplished using a relatively new isotopic tracer, δ17O (Bershaw et al., 2020).
TERROIR
The study of terroir describes how the soil, climate, and other characteristics of a particular location uniquely affect the quality of plants grown there. In the context of wine, think Champagne from Champagne, France or Pinot Noir from the Willamette Valley. Cannabis is now legal to grow and consume in Oregon, with more states soon to follow. The scientific basis for what makes Oregon and California cannabis unique does not yet exist. I am interested in starting to establish the scientific basis for these distinctions. This article in LAWeekly gives a "taste" of what is to come.
SELECTED PUBLICATIONS *indicates student author
*Cohen, J., Bershaw, J., Hugo, R. (2024). Volcanic Glass as a Proxy for Paleotopography Suggests New Features in Late-Miocene Oregon. Atmosphere, 15, 561. DOI:10.3390/atmos15050561. Download
Wang, S., Yang, G., Bershaw, J., Liu, X., Yoshimura, K., Xiao, Y., & Zhang, M. (2024). Interannual variations in stable isotopes of atmospheric water in arid Central Asia due to changes in atmospheric circulation. Global and Planetary Change, 234, 104367. Download
*Jimenez, A. A., Bershaw, J., Saslaw, M., Gall, S., Rahalski, E. (2023). Evaluating the Efficacy of Manmade Canals at Maintaining Lake Habitats for Salmon and Birds Using Seasonal Variations in Isotopes of Meteoric Water. EES Open Archive. Authorea Preprints. DOI:10.22541/essoar.168926403.34465563/v1. Download
*Scanlon, D. P., Bershaw, J., Wells, R. E., & Streig, A. R. (2021). The spatial and temporal evolution of the Portland and Tualatin forearc basins, Oregon, USA. Geosphere, 17(3), 804-823. doi:10.1130/GES02298.1. Download
*McLean, A., & Bershaw, J. (2021). Molecules to Mountains: A Multi-Proxy Investigation Into Ancient Climate and Topography of the Pacific Northwest, USA. Frontiers in Earth Science, 9, 145. doi:10.3389/feart.2021.624961. Download
Bershaw, J., Hansen, D. D., Schauer, A. J., (2020), Deuterium excess and 17O-excess variability in meteoric water across the Pacific Northwest, USA, Tellus B. doi:10.1080/16000889.2020.1773722. Download
Bershaw, J., Burns, E. R., et al., (2020), An Integrated Feasibility Study of Reservoir Thermal Energy Storage in Portland, Oregon, USA, Stanford Geothermal Workshop Conference Paper. Download
Bershaw, J., Cassel, E., J., Carlson, T., B., Streig, A., R., Streck, M., J., (2019), Volcanic Glass as a Proxy for Cenozoic Elevation and Climate in the Cascade Mountains, Oregon, USA, Journal of Volcanology and Geothermal Research. doi:10.1016/j.jvolgeores.2019.05.021. Download
Bershaw, J., Lechler, A. (2019), The isotopic composition of meteoric water along altitudinal transects in the Tian Shan of Central Asia, Chemical Geology, 516, 68-78, doi:10.1016/j.chemgeo.2019.03.032. Download
Bershaw, J. (2018), Controls on deuterium excess across Asia. Geosciences, 8(7), 257, doi:10.3390/geosciences8070257. Download
Bershaw, J., Saylor, J. E., Garzione, C. N., Leier, A., and Sundell, K. E. (2016), Stable Isotope Variations (δ18O and δD) in Modern Waters Across the Andean Plateau, Geochimica et Cosmochimica Acta, 194, doi:10.1016/j.gca.2016.08.011. Download
Bershaw, J., Penny, S. M., and Garzione, C. N. (2012), Stable isotopes of modern water across the Himalaya and eastern Tibetan Plateau: Implications for estimates of paleoelevation and paleoclimate, Journal of Geophysical Research, 117, doi:10.1029/2011JD016132. Download
Bershaw, J., C. N. Garzione, L. Schoenbohm, G. Gehrels, and L. Tao (2012), Cenozoic evolution of the Pamir plateau based on stratigraphy, zircon provenance, and stable isotopes of foreland basin sediments at Oytag (Wuyitake) in the Tarim Basin (west China), Journal of Asian Earth Sciences, 44, 136-148, doi:10.1016/j.jseaes.2011.04.020. Download
Bershaw, J., C. N. Garzione, P. Higgins, B. J. MacFadden, F. Anaya, and H. Alvarenga (2010), Spatial-temporal changes in Andean plateau climate and elevation from stable isotopes of mammal teeth, Earth and Planetary Science Letters, 289, doi:10.1016/j.epsl.2009.11.047. Download