Anya Hess

Paleoceanographer, Paleoclimatologist, Geochemist

Postdoctoral Research Fellow at George Mason University

Hi there!

I am a paleoceanographer and paleoclimatologist who uses geochemical tools to understand our planet's past. I study ocean oxygenation and am particularly interested in oxygen minimum zones, shallow-water areas of the ocean that would be teeming with life if it weren't for their extremely low oxygen concentrations. They expand and contract in response to complex environmental factors, and have been expanding in recent decades. I study how and why they have changed in the geologic past, in response to things like ocean and atmospheric circulation (ventilation pathways, upwelling, stratification, and atmospheric Walker Circulation), biological productivity, and tectonics. I work on timescales from decades during the last millennium to millions of years across warm periods of the Cenozoic, to understand how processes interact on different timescales. All of this comes together to help inform how our environment will likely change as our planet warms, so that we can adapt to those changes.

Picture of me smiling at the camera, with a computer screen in the background with an SEM image of a planktonic foraminifera. This was taken when I was running the SEM to image my forams.

The photo on the screen is an SEM image of a planktonic foraminifera, one of the images I took that day.

I use the chemistry of deep-sea sediments to learn about the oceans of the past.

Picture of me smiling at the camera with the Element II Mass Spectrometer in the background. The machine is running and the plasma is glowing brightly.

This is the lab at Rutgers, and the instrument behind me is our Element II Mass Spectrometer. The machine is running and the plasma is glowing brightly in the center of the white area! This is how I collected all of my elemental data during my Ph.D., and it is where we developed the I/Ca methodology that lets us run it alongside other elements!

I am a trace elemental geochemist, which means I measure the amount of different elements in deep-sea sediments and the trace fossils they contain (foraminifera, or "forams" to their friends). Ratios of different elements tell me about the shallow waters the forams lived in and the deep ocean waters in which they were buried, everything from temperature to the concentration of oxygen and nutrients in the waters. I also use carbon and oxygen isotopes to learn about temperature, water density and salinity, and biological productivity.

My favorite proxy is iodine-to-calcium (I/Ca), a measure for oxygen concentration, and some of my work has focused on laboratory techniques and methods to better understand this proxy. And I work closely with scientists who use other proxies that can tell us even more about the oceans.

If you're interested in collaborating, please reach out!

A bit more background...

I earned my Ph.D. in Earth and Planetary Sciences from Rutgers University in 2024, my Master's in Geology from University of Kansas, and my B.S. in Geology from Bucknell University.

My undergraduate and Master's research were field-based projects in carbonate sedimentology. It was a layer of black shale in my undergraduate section, remnants of anoxia in the Appalachian Basin, that first got me interested in ocean oxygenation.

During my Ph.D., I sailed aboard the JOIDES Resolution expedition JR100 with Samantha Bova and Yair Rosenthal, who would become my Ph.D. advisor. I attended IsoCamp, a 2 week short course in isotope geochemistry in 2019, the last year before it left its original home at the University of Utah. In 2023, I did a model-data integration internship with Natalie Burls at GMU. Her exciting work on Pliocene North Pacific overturning inspired my ideas for the Miocene and is the basis for my current postdoc.

Picture of me smiling at the camera with a bit of a goofy grin. I'm standing next to a microscope with a slide containing foraminifera on it. I am wearing a NASA tshirt with a rocket.

Picking individual forams for analyses is a lot of work, but it lets us learn about specific parts of the oceans. It's amazing how detailed these tiny organisms are!

Before I came to GMU, I was a Postdoctoral Investigator at Woods Hole Oceanographic Institution, where I studied the evolution of the Pacific Walker Circulation during the last millennium. This atmospheric circulation drives upwelling in the eastern tropical Pacific, fueling one of the largest oxygen minimum zones.

I have also worked as a geologist in the oil industry and as a geologic map editor at the U.S. Geologic Survey, and I am happy to speak with students about careers both in and outside of academia.

This website last updated July 2025

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