About me bonus: what I do, why I do it and the basic science behind my PhD

By now, most of you are well aware of my love affair with geology. However, some of you may still not exactly understand what I do or why I do it or have any idea what my upcoming PhD focus means. Because my work will never be an easy explanation for those unfamiliar with what I do, I decided to take this week to describe as best I could (and as un-jargony as possible) what I do, why I do it and the basic science behind my PhD. Eventually, I’ll add or link a shortened version of this to my about me (hence the title), but I felt these words were probably best served first as a standalone post.

As with many geologists, I study the past. I do this for a variety of reasons. First and foremost, I enjoy it. It’s exciting for me to dig into Earth’s history and learn something we didn’t know before or better understand something than we did before. Second, Earth is extremely complex. Studying modern-day change is vital to understanding the complex relationships of Earth systems, but studying the past, and all its glorious “natural experiments,” allows scientists to explore Earth dynamics beyond modern constraints. The past was different than today, and understanding the differences between ancient and modern Earth is extremely important. Lastly, studying the past allows scientist to apply past analogs to future scenarios (i.e. using the past to inform the future) not only in an effort to predict possible outcomes, but also to help the world prepare to face those outcomes. The latter point is the most important to me. We live in a rapidly changing world where human actions have a resounding impact on Earth’s future. Understanding how our planet responded and reacted to past changes, is our greatest hope to predict, plan and prepare for (and in an ideal world, limit) the negative impacts stemming from modern human actions on the complex Earth system.

climate comic

Extremely relevant Joel Pett cartoon, USA Today (2009)

There are lots of ways to study the past, which is why there are lots of different types of geologists (and paleo-[add your science here]-ists). There are geologists who study large, massive structures in ancient formations that are visible for miles away, and there are geologists who study the chemical make-up of rocks and minerals that can only be be discerned after hours of laboratory prep and machine analysis. Some geologists focus on deep time, while others focus on more recent events. Then there are geologists who wander all around the geologic boundaries, putting on all sorts of geologic hats in an attempt to better understand our wonderfully complex planet. Pick any topic and any time period (or even multiple combinations as insane as it may seem), and I guarantee you there’s a geologist somewhere dedicating his or her life to that very geologic niche.

In the spectrum of geologic possibilities, I am a paleoceanographer, paleoclimatologist and geochemist focused (for now) mainly on the more recent geologic past. To decode that geological jargon: I study ancient (but not too ancient) oceans and climate, and I use elements (i.e. chemistry) to discern past events (i.e. geology). Simply put, I’m one of those that wears lots of hats. And to make it even more confusing for you, all of the aforementioned words I used to describe myself as a geologist don’t necessarily make me a geologist at all. Paleoceanographers and paleoclimatologists come from all walks of scientific life. Some are geologists, yes, but many are atmospheric and oceanic scientists, or physicists, or chemists, or even biologists and statisticians. And like the word spells out for you, geochemists are often trained chemists “dabbling” in the world of geology. I will spend the next five years dipping my toes into geology… and all the other wonderful sciences that play a role at the cross-section of paleoceanography, paleoclimatology and geochemistry. Needless to say, I will be very busy as PhD student (gathering lots of pretty hats).

g. ruber foram

An example of fossil foraminifera. See source for detail: Thirumalai et al. (2014), Globigerinoides ruber morphotypes in the Gulf of Mexico: A test of null hypothesis. Scientific Reports 4, 6018. doi: 10.1038/srep06018

Now for the technical stuff. For my science readers–this will probably be easy for you to follow. For all my other readers–I’ll do my best to de-jargon. During my PhD, I will be using (i.e. picking, processing, dissolving and analyzing) fossil foraminifera (a marine protist with a calcite shell–here’s Wikipedia) that have been preserved in ocean sediments to determine and understand past ocean and climate states, changes and relationships. How will I do that?: magnesium (Mg) and calcium (Ca). Mg/Ca ratios can be used as a paleo-proxy (i.e. recorder of the past) for temperature. Simply (and without sending this post down the rabbit-hole of Mg/Ca relationships), the amount of Mg in a calcite mineral relates to the temperature at which that mineral was formed; the more Mg that is in a calcite, the higher the temperature was at the time of formation. In the case of formanifera, or forams, the temperature recorded by a calcite shell is the temperature of the sea water surrounding the foram at the time of shell formation or its calcification temperature. Pretty cool, right? (Yeah, I think so). Measuring Mg/Ca ratios in fossil forams allows scientists to calculate past ocean temperatures! (I know you’re as excited as I am). The exact Mg/Ca-temperature relationship can be dependent on other factors, including foram species, habitat, salinity and even dissolution effects (all things I won’t get into here as it would turn this post into a lengthy research project), but some very, very smart people have developed a myriad of calibration equations (i.e. equations that directly relate Mg/Ca ratios to temperature) to isolate the temperature signal.

Phew. If you made it this far–HIGH FIVE!

Now, some of you are probably wondering exactly how ancient ocean temperatures are going to help me determine and understand past ocean AND climate states, changes and relationships–and that would be a very fair thing for you to wonder. The ocean plays a major role in the Earth climate system, which also includes very important things such as the biosphere and the atmosphere. A perturbation in one part of the system often affects the other parts of the system. For example, a major shift in surface temperatures on Earth will cause a shift in ocean temperatures, which will cause a change in atmospheric winds and weather, which will affect the plants and animals dependent on all those things (…so on and so forth). Understanding the whole Earth climate system requires knowledge of all its parts. And knowledge of one part can also lead to insights on others. I choose to study the ocean because it’s a part of the Earth climate system that we probably know and understand the least about. And while the ocean is only one piece of the giant, complicated climate puzzle, its piece and its close connection with other pieces can tell us a lot about the past. So really, my ancient ocean temperatures will actually tell me a lot more than a simple reading on a thermometer. For those curious about exactly what my PhD project will be, I’ll probably reveal more about that later down the road. As a new graduate student, I’m focused mainly on catching up on the slew of wonderful Mg/Ca-foram literature (I still have a lot to learn), and while I have a pretty good idea where my project is going, things can always change.

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