Using sediment cores to model climate conditions

In the lab of Andreas Schmittner in the College of Earth, Ocean, and Atmospheric Sciences, recently-graduated PhD student Juan Muglia has been developing a climate model to understand ocean current circulation, carbon cycling, and ocean biogeochemistry during the last ice age, focusing on the Southern Ocean surrounding Antarctica.

Juan has developed a climate model using data gathered from sediment cores, which are samples from the ocean floor that provide researchers with a glimpse into the elemental and organic composition of the ocean at different points in time. Scientists can acquire insight into the characteristics of the Earth’s past climate by analyzing the geologic record spanning thousands of years. Modeling the conditions of the last ice age, which occurred 20,000 years ago, allows researchers to better understand how the Earth responds to glacial and interglacial cycles, prompting the transition between cold and warm phases (we are currently in a warm interglacial period).

The process of generating an accurate climate model consists of tuning parameters embedded in the physics equations and fortran code of the model, to reproduce characteristics directly observable in modern times. If researchers can validate their model by reproducing directly observable characteristics, the model can then be used to investigate the climate at points in time beyond our direct observational capacity.

Since it’s not possible to directly measure temperature or nutrient composition of the ocean during the last ice age, Juan uses an indirect signature that serves as a proxy for direct measurement. Three isotopic sediment tracers, including 15Nitrogen, 14Carbon, and 13Carbon, are incorporated into Juan’s climate model as proxies for biological productivity and current circulation in the ocean. Investigating changes in the elemental composition of the ocean, also known as biogeochemistry, is important for understanding how climate and biology have transformed over thousands of years. The ocean serves as an enormous reservoir of carbon, and much more carbon is sequestered in the ocean than in the atmosphere. The exchange of carbon dioxide at the interface of the ocean and atmosphere is important for understanding how carbon dioxide has and will continue to impact pH, ocean currents, and biological productivity of the ocean.

Even as a kid, Juan dreamed of becoming an oceanographer. He grew up near the ocean in Argentina, surrounded by scientists; his mom was a marine botanist and his dad is a geologist. During his undergraduate studies, he majored in physics with the goal of eventually becoming a physical oceanographer, and his undergraduate thesis consisted of building fortran code for a statistical physics project. After finishing his post-doctoral studies at OSU, Juan plans to return to his hometown in Argentina, where he hopes to develop a model specific to the Argentinian climate.

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