Plio-Pleistocene Paleoclimate Change Research
Dr. Joseph D. Ortiz
Kent State University, Department of Geology
On glacial-interglacial timescales, variability in Earth's climate system is largely explained by the Milankovitch-Croll hypothesis, which postulates that glacial interglacial climate changes occur in response to cyclic variations in the geometry of Earth's orbit around the sun, which control changes in solar insolation (solar output per unit time per unit area). Milankovitch-forcing occurs on time scales ranging from 20,000 to 400,000 years per cycle, although longer cycles in solar insolation that are unresolved by current paleoclimate records may be present. On longer timescales, with trends or cycles of millions to billions of years in duration, large-scale changes in solar luminosity (total solar output), tectonic shifts, and biogeochemical cycling in response to the evolution of Earth's biosphere control the long-term, "Tectonic-scale" climate state. On shorter timescales (<20,000 years per cycle), the interplay of more subtle changes in solar irriadiance (solar output per unit area), volcanic forcing, internal oscillations of the climate system and anthropogenic forcing drive climate variability. The most important of these "short-term" changes has been anthropogenic-forcing of the climate system from the Industrial Revolution to present.
I've been fortunate to receive training from John Imbrie, Warren Prell, Alan Mix, and Nick Pisias, researchers who were instrumental in the development of our understanding of Milankovitch-scale climate change as part of the CLIMAP and SPECMAP projects. I apply a quantitative, time series analysis approach to study of the interactions of various components of the Earth's climate system on glacial-interglacial timescales. As with my study of climate variability on timescales shorter than <20,000 years per cycle, I make use of sediment physical properties measurements (visible derivative spectroscopy, laser particle size analysis, and elemental analysis by x-ray florescence) to reconstruct climate variability on glacial-interglacial timescales. These methods are rapid, require little sample preparation and yield, rich, multivariate data sets that can be unmixed, or decomposed using statistical methods to partition variance related to how different processes have influenced a location through time. I also employ micropaleontological and stable isotope analysis of foraminifera as needed to answer questions about glacial-interglacial climate change. Although I am interested in global processes, I address these questions through detailed regional reconstructions and have worked in most of the World Ocean's major basins.
Apply online to the Graduate Program in Geology at Kent State University.
More information about the Kent State University Geology Graduate program.
are some papers you can read to learn about my
work in this area:
Klompmaker, A., Ortiz, J.D. and Wells, N.A., 2013, How to explain a decapod crustacean diversity hotspot in a mid-Cretaceous coral reef, Palaeogeography, Palaeoclimatology, Palaeoecology, Early online release: 3/5/2013: http://dx.doi.org/10.1016/j.palaeo.2013.01.024.
Yi, L., Yu, H., Xu X., Ortiz J.D., Deng C., Qiang X., and Huang H., 2012, A reconstruction of late Pleistocene relative sea level in the south Bohai Sea, China, based on sediment grain-size analysis, Sedimentary Geology, 281, 88-100, Early online release: 9/3/2012, (doi: 10.1016/j.sedgeo.2012.08.007).
Yi, L., Yu H.-J., Ortiz, J.D., Xu, X.-Y., Chen, S.-L., Ge, J.-Y., Hao, Q.-Z., Yao, J., Shi, X.-F., Peng, S.-Z., 2012, Late Quaternary linkage of sedimentary records to three astronomical rhythms and the Asian monsoon, inferred from a coastal borehole in the south Bohai Sea, China, Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 329-330, 101-117, doi:10.1016/j.palaeo.2012.02.020.
Yurco, L., Ortiz, J.D., Leonid Polyak, L., and Darby, D., 2010, Reflectance-based clay mineral cycles in Quaternary sediments from the Northwind Ridge: implications for glacial-interglacial sedimentation patterns in the Arctic Ocean, Polar Research, DOI: 10.1111/j.1751-8369.2010.00160.x.
Sorhannus, U., Ortiz, J.D., Wolf, M., , 2010, Microevolution and Speciation in Thalassiosira weissfloggi, Protist, 161,237-249.
Adler, R.E., Polyak, L., Ortiz, J.D., Kaufman, D.S., Channell, J.E.T., Xuan, C., Grottoli, A.G., Sellen, E., Crawford, K.A., 2009, Sediment record from the western Arctic Ocean with an improved Late Quaternary age resolution: HOTRAX core HLY0503-8JPC, Mendeleev Ridge. Global and Planetary Change, (68), 18-29.
Polyak, L., Bischof, J., Ortiz, J.D., Darby, D.A., Channell, J.E.T., Xuan, C., Kaufman, D.S., Løvlie, R., Schneider, D.A., Eberl, D.D., Adler, R.E., Council, E.A., Late, 2009, Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean. Global and Planetary Change, (68), 5-17.
Dean, W. E., Zheng, Y., Ortiz, J.D., and A. van Geen, Sediment Cd and Mo accumulation in the oxygen-minimum zone off western Baja California linked to global climate over the past 52 kyr, Paleoceanography, 21, PA4209, doi:10.1029/2005PA001239, 2006.
Ortiz, J.D., O’Connell, S., DelViscio, J., Dean, W., Carriquiry, J., Marchitto, T., Zheng, Y., and A. van Geen, Enhanced marine productivity off western North America during warm climate intervals of the past 52 kyr, Geology, 32(6), 521-524, 2004.
van Geen, A., Y. Zheng, J. M. Bernhard, K. G. Cannariato, J. Carriquiry, W. E. Dean, B. W. Eakins, J.D. Ortiz, J. Pike, and other participants, 1999 RV Melville Baja California cruise, On the preservation of laminated sediments along the western margin of North America, Paleoceanography, 18(4),1098, doi:1029/2003PA000911, 2003.
Marchitto, T.M., Lehman, S.J., Ortiz, J.D., Fluckinger, J., and A. van Geen, Marine radiocarbon evidence for the mechanism of deglacial atmospheric CO2 rise (8 June 2007), Science 316 (5830), 1456. [DOI: 10.1126/science.1138679] (Supplemental Online Material). Advance online publication: / www.sciencexpress.org / 10 May 2007 / Page 5 / 10.1126/science.1138679.
O'Connell, S., and Ortiz, J.D. Data Report: Calcium carbonate stratigraphy from sample measurements and diffuse spectral reflectance at Site 1090, ODP Leg 177. In Gersonde, R., Hodell, D.A., and Blum, P. (Eds.), Proc. ODP, Sci. Results, 177 2002.
Ortiz, J.D., Mix, A., Harris, S., and S. O'Connell, Diffuse spectral reflectance as a proxy for percent carbonate content in North Atlantic sediments, Paleoceanography, 14, 171-186, 1999.
Ortiz, J.D., O'Connell, S., Leg 162 Shipboard Sedimentologists, and A. Mix, Data report: Spectral reflectance observations from Leg 162 recovered sediments, in Proc. ODP, Sci. Results, 162, Raymo, M.E., Jansen, E., Blum, P. and Herbert, T.D. (Eds.), College Station, TX, (Ocean Drilling Program), 259-264, 1999.
Hyun, S., Ortiz, J.D., Raymo, M.E., and A. Taira, Low-frequency oscillations in Site 983 sediments: Relationships between carbonate and productivity proxies Proc. ODP, Sci. Results, 162, in Raymo, M.E., Jansen, E., Blum, P. and Herbert, T.D. (Eds.), College Station, TX, (Ocean Drilling Program), 197-207, 1998.