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Attempting to Recreate the Late Ordovician Glaciation with the University of Victoria Earth System Climate Model

Warthen, Seth Tyler

Abstract Details

2016, Master of Science, Ohio State University, Atmospheric Sciences.

The University of Victoria Earth System Climate Model (UVic ESCM) of intermediate complexity was used to simulate the Late Ordovician period (~440 Mya) in order to attempt to recreate the conditions which would be favorable to induce a short-lived glaciation, which is evidenced to have occurred through isotopic and geological analysis of Late Ordovician sediments. This time period featured vastly different geography than that of present day, CO2 concentrations likely ranging from 8x to 20x that of preindustrial levels (PIL), decreased solar luminosity and decreased day length. In addition, life during the time period was limited almost exclusively to the oceans. The end of the Late Ordovician period features one the largest mass extinction events throughout the history of the Earth, in which over three quarters of all marine species became extinct.

Multiple simulations were conducted with the UVic ESCM under numerous boundary conditions in order to attempt to replicate the conditions which might lead to glaciation. Primarily these boundary conditions include running simulations at different concentrations of CO2 (from 6x PIL to 12x PIL), and using different orbital configurations designed to yield the hottest or coldest possible summertime temperatures in the southern hemisphere. Attempts were made to reduce the value of solar luminosity in some experiments, but these attempts were unsuccessful due to the model simulations becoming unstable.

Literature diverges on what orbital configuration results in the coldest or warmest southern hemisphere summertime temperatures. This study found that the coldest summer temperatures are achieved with an eccentricity of 6.0 x 10-2, an obliquity of 22.0°, and a longitude of perihelion of 90°. The warmest summer temperatures were achieved with an eccentricity of 6.0 x 10-2, an obliquity of 24.5°, and a longitude of perihelion of 270°.

Overall, the failure to reduce the solar luminosity resulted in temperatures too warm to successfully replicate the temperatures which would be found during the Late Ordovician glaciation. While reducing the concentration of atmospheric CO2 to the lower bound of the plausible range for the time did result in lower temperatures, they would not be cold enough for glaciation. With all possible orbital configurations, wintertime temperatures along southern Gondwana fail to fall below freezing, thus causing all precipitation to fall as rain, precluding any glaciation from commencing. One simulation which was undertaken at a CO2 concentration 12x PIL did successfully have the solar luminosity reduced by 1.77%, and yielded similar temperatures to simulations undertaken with a non-reduced solar luminosity and CO2 concentrations of 6x PIL. This strongly implies that future work will need to successfully reduce the solar luminosity in order to successfully achieve subfreezing temperatures, and subsequent glaciation.

Alvaro Montenegro, Dr. (Advisor)
Bryan Mark, Dr. (Committee Member)
159 p.

Recommended Citations

Citations

  • Warthen, S. T. (2016). Attempting to Recreate the Late Ordovician Glaciation with the University of Victoria Earth System Climate Model [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1465828293

    APA Style (7th edition)

  • Warthen, Seth. Attempting to Recreate the Late Ordovician Glaciation with the University of Victoria Earth System Climate Model. 2016. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1465828293.

    MLA Style (8th edition)

  • Warthen, Seth. "Attempting to Recreate the Late Ordovician Glaciation with the University of Victoria Earth System Climate Model." Master's thesis, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1465828293

    Chicago Manual of Style (17th edition)