Paleoclimate, Speleothems, Geochemistry, Isotopes, Asian Monsoon
Fellow of the Geological Society of America
Post-doctoral Research Fellow, Gary Comer Abrupt Climate Change Fellowship
University of Oxford, UK 2004-2007
Lecturer in Earth Sciences, Jesus College, University of Oxford, UK 2006-2007
My research primarily involves the use of geochemical variations preserved in cave-calcite deposits (speleothems) to reconstruct time-series of past environmental changes. A major goal of my research is to improve our understanding of what fundamentally controls speleothem stable isotopic composition and trace-element composition at both short and long timescales (seasonal to glacial-interglacial scale). These proxies are primarily controlled by variations in temperature and/or rainfall at a particular study area, but the specific mechanisms are complicated, incorporating a range of atmospheric, hydrologic, biologic, pedologic, kinetic, crystallographic, and thermodynamic controls. To understand these controls, I combine detailed studies of modern cave systems with studies of fossil speleothems, utilizing a wide range of analytical techniques (e.g. microsampling, analytical chemistry, mass spectrometry, laser ablation, etc.) along with laboratory experiments, rigorous data analysis, and geochemical modeling. Speleothem records can be dated much more precisely than most other paleoclimate archives using U-series methods, and therefore, often provide important information about the relative timing and mechanisms of abrupt climate change. The ultimate goal of my research is to obtain precisely dated, high-resolution, quantitative reconstructions of past variations in rainfall and temperature at a wide range of timescales.
I am currently working on paleoclimate records from Laos, Vietnam, and Mexico. High resolution speleothem records from these regions have great potential to help answer key questions about past rainfall variability in these heavily populated regions, where even small changes in the timing and intensity of rainfall can have significant societal, environmental, and economic impacts. In addition, by studying past climate in these regions, we hope to improve our understanding of the past variability and interactions between such major climate modes as the El Nino Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the Asian monsoon system. Speleothems are one of the most promising archives where millennial-to-seasonal scale continental climate variability may be investigated, and I plan to continue working towards a more spatially and temporally complete speleothem record and an improved understanding of these archives in general.
2018-2019 UCI Inclusive Excellence Spirit Award for “UCI Natural Reserves and Building Relationships with Native Nations as Kuuyam (guests) on Indigenous Homelands.”
College-Level Promotion of Education Award, 2018 Women of Color in STEM Conference, Career Communications Group, Inc.
2017-2018 UCI Inclusive Excellence Spirit Award for “Cultivating Consciousness in Acjachemen and Tongva Homelands”
2016 Bromery Award for Minorities, Geological Society of America (Sept. 25th, 2016)
Chancellor’s Award for Excellence in Fostering Undergraduate Research, University of California, Irvine. (May 18, 2013).
Outstanding Contributions to Undergraduate Education, School of Physical Sciences. (May 2012).
Outstanding Contributions to Undergraduate Education, School of Physical Sciences. (May 2010).
Gary Comer Abrupt Climate Change Foundation Fellowship. (August 2004 - June 2007).
Graduate Student Research Grant, Geological Society of America. (2002).
Scholarship in Geochronology, Berkeley Geochronology Center. (1999 - 2002).
38. Wolf. A., Roberts, W.H.G., Ersek, V., Johnson, K.R., Griffiths, M.L. (2020). Rainwater isotopes in central Vietnam controlled by two oceanic moisture sources and rainout effects. Scientific Reports, 10:16482.
37. Comas-Bru, L., Rehfeld, K., Roesch, C., Amirnezhad-Mozhdehi, S., Harrison, S. P., Atsawawaranunt, K., Breitenbach, S. F.,……and SISAL members (2020). SISALv2: A comprehensive speleothem isotope database with multiple age-depth models. Earth System Science Data, 12, 2579-2606.
36. Griffiths, M.L., Johnson, K.R., Pausata, F.S.R., White, J.C., Henderson, G.M., Wood, C.T.*, Yang, H.*, Ersek, V., Conrad, C., Sekhon, N.* (2020). End of Green Sahara amplified mid-to late Holocene megadroughts in mainland Southeast Asia. Nature Communications, 11(1).
35. Gutierrez-Garcia, G., Beramendi-Orosco, L.E., Johnson, K.R. (2020). Climate-growth relationships of Pinus pseudostrobus from a tropical mountain cloud forest in northeast Mexico. Dendrochronologia, 125749.
34. Wang, Y., Hu, C., Ruan, J., Johnson, K.R. (2020). East Asian precipitation d18O relationship with various monsoon indices. Journal of Geophysical Research: Atmospheres, 125(13), e2019JD032282.
33. Cottone, C. M. M., Lu, S., Wu, Y. X., Guan, K., Yoon, R., Limfueco, L., ... & Patel, R. M. (2020). Surface-Treated Pellethanes: Comparative Quantification of Encrustation in Artificial Urine Solution. Journal of Endourology, 34(8).
32. Wang, J.K.*, Yu, J.Y., Johnson, K.R. (2020). Pacific and Atlantic controls of the relationship between Mainland Southeast Asian and East China interannual precipitation variability. Climate Dynamics, 1-14.
31. Aarons, S.M.*, Arvin, L.J., Aciego, S.M., Riebe, C., Johnson, K.R., Blakowski, M.A., Koornneef, J.M., Hart, S.C., Barnes, M.E., Dove, N., Botthoff, J.K., Maltz, M., Aronson, E.L. (2019). Competing droughts affect dust delivery to Sierra Nevada. Aeolian Research, 41, 100545.
30. Wang, J. K.*, Johnson, K. R., Borsato,A., Amaya, D.J., Griffiths, M. L., Henderson, G. M., Frisia, S., Mason, A .(2019). Hydroclimatic variability in Southeast Asia over the past two millennia. Earth and Planetary Science Letters, 525, 115737.
29. Carlson, P.E., Banner, J.L., Johnson, K.R., Casteel, R.C., Breecker, D.O. (2019). Carbon cycling of subsurface organic matter recorded in speleothem 14C records: Maximizing bomb-peak model fidelity. Geochimica et Costmochimica Acta, 246, 436-439.
28. Beramendi-Orosoco, L.E., Johnson, K.R., Noronha, A.L.*, González-Hernández, G., Villanueva-Díaz, J. (2018). High precision radiocarbon concentrations in tree rings from Northeastern Mexico: A new record with annual resolution for dating the recent past. Quaternary Geochronology, 48, 1-6
27. Bergel, S., Carlson, P. E., Larson, T. E., Wood, C. T.*, Johnson, K. R., Banner, J. L., Breecker, D. O. (2017). A subsoil carbon source to cave-air CO2 and speleothem calcite in central Texas. Geochimica et Cosmochimica Acta, Volume 217, 112-127.
26. Ng, J. Y., Williams, B., Thompson, D. M., Mayne, C., Halfar, J., Edinger, E., Johnson, K. R. (2016). Assessing multi-site d18O-climate calibrations of the coralline alga Clathromorphum across the high-latitude Northern Hemisphere, Geochimica et Cosmochimica Acta, 194, 279–290.
25. McCabe-Glynn, S.*, Johnson, K. R., Strong, C., Zou, Y., Yu, J.-Y., Sellars, S., Welker, J. M. (2016). Isotopic signature of extreme precipitation events in the western US and associated phases of Arctic and tropical climate modes. Journal of Geophysical Research: Atmospheres, 121(15), 8913–8924.
24. Yang, H*., Johnson, K. R., Griffiths, M., Yoshimura, K. (2016). Interannual controls on oxygen isotope variability in Asian monsoon precipitation and implications for paleoclimate reconstructions. Journal of Geophysical Research: Atmospheres, 121(14), 8410–8428.
23. Griffiths, M. L**., Kimbrough, A. K., Gagan, M. K., Drysdale, R. N., Cole, J. E., Johnson, K. R., Zhao, J.-X., Cook, B. I., Hellstrom, J. C., Hantoro, W. S. (2016). Western Pacific hydroclimate linked to global climate variability over the past two millennia. Nature communications, 7.
22. Noronha, A. L.*, Johnson, K. R., Southon, J. R., Hu, C., Ruan, J., McCabe-Glynn, S. (2015). Radiocarbon evidence for decomposition of aged organic matter in the vadose zone as the main source of speleothem carbon. Quaternary Science Reviews, 127, 37-47.
21. Baker, A., Sodemann, H., Baldini, J. U.L., Breitenbach, S. F.M., Johnson, K. R., van Hunen, J., Zhang, P. (2015). Seasonality of westerly moisture transport in the East Asian Summer Monsoon and its implications for interpreting precipitation d18O. Journal of Geophysical Research: Atmospheres, 120(12), 5850–5862.
20. Noronha, A. L.*, Johnson, K. R., Hu, C., Ruan, J., Southon, J., Ferguson, J. E. (2014). Assessing influences on speleothem dead carbon variability over the Holocene: implications for speleothem-based radiocarbon calibration. Earth and Planetary Science Letters, 394, 20-29.
19. McCabe-Glynn, S.*, Johnson, K. R., Strong, C., Berkelhammer, M., Sinha, A., Cheng, H., Edwards, R. L. (2013). Variable North Pacific influence on drought in southwestern North America since AD 854. Nature Geoscience, 6, 617 - 621.
18. Ferguson, J.**, Johnson, K. R., Santos, G., Meyer, L., Tripati, A. (2013). Investigating d13C and ?14C within Mytilus californianus shells as proxies of upwelling intensity. G-cubed: Geochemistry, Geophysics, Geosystems, 14(6), 1856 - 1865.
17. Liu, Y. H., Henderson, G. M., Hu, C., Mason, A., Charnley, N., Johnson, K. R., Xie, S. (2013). Links between the East Asian monsoon and North Atlantic climate during the 8,200 year event. Nature Geoscience, 6, 117-120.
16. Griffiths, M. L.**, Fohlmeister, J., Drysdale, R. N., Hua, Q., Johnson, K. R., Hellstrom, J. C., Gagan, M., Zhao, J. (2012). Hydrological control of the dead carbon fraction in a Holocene tropical speleothem. Quaternary Geochronology, 14, 81-93.
15. Doezema, L., Longin, T., Cody, W., Perraud, V., Dawson, M., Ezell, M., Greaves, J., Johnson, K. R., Finlayson-Pitts, B. J. (2012). Analysis of secondary organic aerosols in air using extractive electrospray ionization mass spectrometry (EESI-MS). RSC Advances, 2(7), 2930-2938.
14. Berkelhammer, M., Stott, L., Yoshimura, K.., Johnson, K. R. (2012). Synoptic and mesoscale controls on the isotopic composition of individual storms systems striking the western US. Climate Dynamics, 38(3-4), 433-454. 0930-7575.
13. Santos, G. M., Ferguson, J.**, Acaylar, K., Johnson, K. R., Griffin, S., Druffel, E. R.M. (2011). ?14C and d13C of seawater DIC as tracers of coastal upwelling: A 5-year time series from Southern California. Radiocarbon, 43(4), 669-677.
12. Lee, J.-E., Johnson, K. R., Fung, I. (2009). Precipitation over South America during the Last Glacial Maximum: An analysis of the ‘‘amount effect’’ with a water isotope-enabled general circulation model. Geophysical Research Letters, 36(L19701).
11. Zhang et al. (2008). A Test of Climate, Sun, and Culture Relationships from an 1810-Year Chinese Cave Record. Science, 322, 940-942.
10. Hu, C. Y., Henderson, G. M., Huang, J. H., Chen, Z. H., Johnson, K. R. (2008). Report of a three-year monitoring programme at Heshang Cave, Central China. International Journal of Speleology, 37(3), 143-151.
9. Liu et al. (2008). Asian summer monsoon precipitation recorded by stalagmite oxygen isotopic composition in the western Loess Plateau during AD1875-2003 and its linkage with ocean-atmosphere system. Chinese Science Bulletin, 53, 2041-2049.
8. Lewis, H. A., Johnson, K. R., Ronquillo, W.(2008) Preliminary results of speleothem dating from Tabon Cave, Palawan, Philippines: moisture increase at the Last Glacial Maximum. Hukay.
7. Hu, C., Henderson, G. M., Huang, J. H., Xie, S. C., Johnson, K. R. (2008). Quantification of Holocene Asian monsoon rainfall from spatially separated cave records. Earth and Planetary Science Letters, 266, 221-232.
6. Yang, X. L., Zhang, P. Z., Chen, F. H., Huh, C. A., Li, H. C., Cheng, H., Johnson, K. R., Liu, J. H., An, C. L. (2007). Modern stalagmite oxygen isotopic composition and its implications of climatic change from a high-elevation cave in the eastern Qinghai-Tibet Plateau over the past 50 years. Chinese Science Bulletin, 52, 1238-1247.
5. Johnson, K. R., Hu, C. Y., Belshaw, N. S., Henderson, G. M. (2006). Seasonal trace-element and stable-isotope variations in a Chinese speleothem: The potential for high-resolution paleomonsoon reconstruction. Earth and Planetary Science Letters, 244, 394-407.
4. Johnson, K. R., Ingram, B. L., Sharp, W. D., Zhang, P. Z. (2006). East Asian summer monsoon variability during Marine Isotope Stage 5 based on speleothem delta O-18 records from Wanxiang Cave, central China. Palaeogeography Palaeoclimatology Palaeoecology, 236, 5-19.
3. Johnson, K. R., Ingram, B. L. (2004). Spatial and temporal variability in the stable isotope systematics of modern precipitation in China: implications for paleoclimate reconstructions. Earth and Planetary Science Letters, 220, 365-377.
2. Zhang, P., Johnson, K. R., Chen, Y., Chen, F., Ingram, B. L., Zhang, X., Zhang, C., Wang, S., Pang, F., Long, L. (2004). Modern systematics and environmental significance of stable isotopic variations in Wanxiang Cave, Wudu, Gansu, China. Chinese Science Bulletin, 49, 1649-1652.
1. Yang, B., Braeuning, A., Johnson, K. R., Shi, Y. F. (2002). General characteristics of temperature variation in China during the last two millennia. Geophysical Research Letters, 29.
American Geophysical Union
Geological Society of America
National Speleological Society
American Indian Science and Engineering Society