Sarothi Ghosh
University of Florida
Research Mentor: T.J. Fudge
Project: Exploring the δ18O response to WAIS collapse using simple isotope models
My name is Sarothi Ghosh, and I’m a 3rd year Physics major at the University of Florida. Over the summer, I worked with Lindsey Davidge and Dr. T.J. Fudge of the UW Earth & Space Sciences Department to model heavy water isotope ratios using simple, zonally averaged climate models.
About 120k years ago, the Earth was in a relatively warm period known as the Last Interglacial. One uncertainty about the climate during this period is the extent of ice loss in the West Antarctic Ice Sheet (WAIS). Ratios of heavy water isotopes (such as H218O/H216O, or δ18O) depend on climate conditions related to the WAIS. Therefore, measuring these ratios in future Antarctic ice cores may indicate the condition of West Antarctica during this period. My project was focused on understanding the climate factors that control δ18O during a WAIS collapse. This was done by comparing outputs from different climate models, using inputs from the same scenario.
The WAIS collapse scenario, as well as a control run, were conducted using a 3-D general circulation model known as the CCSM4. Another 3-D model, the WRF, was run over Antarctica using forcings from the CCSM4. This provided an output of δ18O with relatively high resolution and complexity. The 3-D model runs were conducted by Andrew Pauling, Dr. Marina Dütsch, and Dr. Peter Blossey.
I was involved with simpler, 1-D climate models; these models simulated averages across longitudes, from the South Pole to the North Pole. Climate variables (temperature, evaporation, and precipitation) were taken from the CCSM4 runs and used as inputs into these models. The simpler modeling of climate and δ18O allowed me to focus on larger-scale drivers of δ18O change; comparing the models’ outputs with the WRF’s outputs assisted in understanding the role of more local variations. The 1-D models were created by Dr. Nick Siler; I ran them in MATLAB, and examined the results in Python.
Our results showed that local variations in evaporation and precipitation were very important in modeling the δ18O response to a WAIS collapse. That said, some changes in evaporation and precipitation appeared significant enough to be captured on the global scale. In addition, modeling of δ18O near the South Pole had mixed results when using the 1-D models. These results are preliminary, and we plan to continue this research through my fall semester at the University of Florida.
This internship was a great opportunity. I gained experience with coding in Python and MATLAB, investigating paleoclimate questions, and presenting research. In addition, this was a great chance to explore Seattle and the Pacific Northwest. Many thanks to UW/CICOES, Lindsey, T.J., and all of the researchers mentioned above for making this project possible.
Project introduction
Research poster
