Kathleen R. Johnson

Assistant Professor, Earth System Science
School of Physical Sciences

B.S., University of Michigan, 1996, Geology

Ph.D., University of California, Berkeley, 2004, Geology

Phone: (949) 824-6174
Fax: (949) 824-3874
Email: kathleen.johnson@uci.edu

University of California, Irvine
3206 Croul Hall
Mail Code: 3100
Irvine, CA 92697

picture of Kathleen R. Johnson

Paleoclimatology, Speleology, Isotope and trace element geochemistry
2002 Graduate Student Research Grant, Geological Society of America
1999-2002 Scholarship in Geochronology, Berkeley Geochronology Center
1999 Karst Research Fellowship, Cave Research Foundation
Appointments 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 primarily on paleoclimate records from the Asian monsoon region (China) and the tropical Indian Ocean (Sri Lanka). 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.
Publications Johnson, K.R., Hu, C.Y., Belshaw, N.S., and 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, v. 244, p. 394-407.
  Johnson, K.R., Ingram, B.L., Sharp, W.D., and 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, v. 236, p. 5-19.
  Johnson, K.R., 2006, Caves and Climate Change, in Blumel, D., ed., McGraw -Hill 2006 Yearbook of Science & Technology: New York, NY, McGraw-Hill Professional.
  Johnson, K.R., and 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, v. 220, p. 365-377.
  Yang, B., Braeuning, A., and Johnson, K.R., 2002, General characteristics of temperature variation in China during the last two millennia: Geophysical Research Letters, v. 29.
  Zhang, P.Z., Johnson, K.R., Chen, Y.M., Chen, F.H., Ingram, L., Zhang, X.L., Zhang, C.J., Wang, S.M., Pang, F.S., and Long, L.D., 2004, Modern systematics and environmental significance of stable isotopic variations in Wanxiang Cave, Wudu, Gansu, China: Chinese Science Bulletin, v. 49, p. 1649-1652.
American Geophysical Union
Geological Society of America
National Speleological Society
Link to this profile http://www.faculty.uci.edu/profile.cfm?faculty_id=5444
Last updated 08/31/2007