Seabound alumna studies the questions beneath the surface

Of the many Harpeth Hall alumnae who demonstrate boundless curiosity, Maddie Shankle ’12, Ph.D. is a standout. Her academic path — from Harpeth Hall classrooms to research vessels and university labs — reflects a steady pursuit of questions about the planet’s past, present, and future.

A 2012 graduate of Harpeth Hall, Dr. Shankle took a gap year before going to Yale University, where she double-majored in environmental engineering and geology and geophysics, graduating in 2018. Her experience at Yale was greatly shaped by her geology degree, in which she specialized in oceans, atmosphere, and climate. She also spent a significant amount of time working in a paleoceanography research group, which focused on the study of the ocean in Earth’s past.

As part of that group, she studied how the ocean operated differently under past climate states, including the hot-house climate of the dinosaur era or the icy climate of Earth’s past ice ages. As a lab assistant, she generated proxy data, which is data collected on samples that indirectly measure features of the climate. When examining proxy data, scientists may look at tree rings, whose width and density indicate past temperature and rainfall conditions, or the chemical composition of ocean sediments, which can tell you about changing ocean conditions over time as you go deeper into the sediment core. Dr. Shankle worked on the latter and carried on in this role for one year following graduation.

At the end of that time, she became curious about how the modern ocean worked and, in 2018, undertook a Master of Science at Bangor University in the United Kingdom. There, Dr. Shankle studied the physics of how the ocean flows, ranging from tides to large-scale circulations like the Gulf Stream. Her Ph.D. brought her back to paleo at the University of St Andrews, where she studied the ocean’s state during Earth’s past ice ages. Specifically, she studied the different ways the ocean absorbed CO2 and stored it for long periods of time. What she learned is that such processes would have drawn down CO2 from the atmosphere, thereby cooling the climate, which is the leading hypothesis for why the ice ages occurred. Dr. Shankle completed her Ph.D. in 2025 and now works as a research scientist at the University of St Andrews. While she still occasionally studies questions of the past ocean, she now focuses on CO2 uptake by the ocean in the modern day. Dr. Shankle sat down to tell us more about how Harpeth Hall inspired her search for knowledge and what her job looks like today.

1. When did your curiosity about the planet — and specifically the ocean — first take hold? Was there a moment at Harpeth Hall that pointed you toward this path?

I would say my curiosity about the planet and ocean developed in full when I got to college. I had always cared about taking care of the planet, and I actually applied to college intending to major in engineering. This seemed the best way to put my skills to use, building solar panels or windmills or similar infrastructure to help combat climate change. However, in a freshman year class, I realized I was so much more fascinated by learning how the planet itself worked, and I was surprised to find how much work was left to be done on the subject. This is when I got really curious about the climate, and my passion for the ocean specifically came out of a long process of dabbling in different disciplines in my classes and employment in research labs. Harpeth Hall definitely started me on this path, though, since it was my senior year physics class that made me want to go to college for engineering. I had always enjoyed all my science classes equally, but that year I discovered I loved physics the best, and physical science still makes up the majority of my work today.

2. Your work connects geology, paleoclimatology, and physical oceanography.

What possibilities open up when you blend disciplines rather than choose just one? This makes me think of the old adage, “A jack of all trades is a master of none, but oftentimes better than a master of one.” While it’s easy to focus on the first half and doubt my abilities compared to peers who have studied a single subject their whole careers, I know that my more circuitous route has ultimately only served to help me, since I am now in a field (which yes is some amalgamation of paleoclimatology and physical oceanography) which my interests and abilities are precisely suited to. When you’re a jack of all trades, different possibilities open up for you. You have the skillset to pursue more varied research, and you also often serve a valuable role as a liaison between people of deeper, but narrower, expertise. I’d also say that oceanography, or any field related to the planet — meteorology, climatology, ecology, etc. — is inherently multidisciplinary. For example, I study how the ocean absorbs and stores CO2 , and this is influenced by lots of chemical, physical, and biological processes happening all at the same time. You need to be multidisciplinary to get a good grasp of what’s going on.

3. Women remain underrepresented in scientific research roles globally. How did Harpeth Hall help you develop the confidence to pursue STEM at the highest levels?

I’ll always be grateful for the excellent teachers at Harpeth Hall, whose unwavering vocalized and demonstrated support I’m sure kept any creeping doubts at bay. Not once did any doubt cross my mind that I couldn’t pursue anything that I wanted to, and I have the wonderful culture and overall spirit of Harpeth Hall to thank for that. The ample STEM resources and opportunities afforded to us were also crucial. Clubs like Science Olympiad and IMAGINE (I’m a Girl in Engineering) gave me experience working out problems on my own and not having the answer in the back of the textbook. This is exactly what real science is like(!) and did a lot to boost my confidence. And of course, Winterim was invaluable in the same way. I still can’t believe how fortunate we are to have had these experiences. I worked in a hospital laboratory in D.C., which developed treatments to metabolic diseases in children. It was such fascinating work with such an uplifting and motivating goal. I wanted to work to make the world a better place in a similar way, and having that experience under my belt gave me the confidence to do so.

4. Your work spans an incredible range — from studying ancient climate systems to modeling future ocean changes. What motivates you to keep asking new questions and pushing into the unknown?

I think one main thing that motivates me is an inherent satisfaction that comes from figuring out how something works and learning something new that we didn’t know before. When you get deep enough into any scientific field, you find gaps in our understanding, and it’s a very methodical process working out the missing piece — running tests, analyzing data for trends and patterns, and so forth. I find this analytical work very satisfying. More satisfying, however, is the end result, which usually includes some new understanding of how something works or why something is the way that it is. Uncovering this new knowledge, that no one knew for certain before, I find very motivating and is what keeps me coming back to asking new questions.

5. What skills or lessons from Harpeth Hall show up most in your daily life as a researcher?

I will always be grateful for the quality of education I received at Harpeth Hall. I not only became proficient in math and science, I also became an effective communicator and writer. This is actually crucial to being a scientist when you present your results at a conference or write them into an article. I find I constantly use all of my left-brain and right-brain academic skills, first nurtured and developed at Harpeth Hall. More broadly, though, a certain spirit of genuine and supportive camaraderie is something I’ve carried with me throughout my education and career. It was a bit of a shock when I experienced how competitive graduate school and science can be. With such an inordinate amount of pressure to perform and deliver, people can be overly protective of their work or even sabotage others’. It is sad because it completely squashes the spirit of collaboration that moves science forward so well. Harpeth Hall taught me not only to have confidence in my own abilities but also that sharing my strengths and my work with others would not drag me down. This made the whole journey a lot easier and earned me some friends along the way.

6. You’ve pursued knowledge in classrooms, laboratories, and fieldwork across three continents and multiple oceans. How has that global experience inspired you?

I’m incredibly fortunate to have had the experiences I’ve had around the world. You learn so much more working in different countries, in different contexts, and with different people than you ever could learn in one place. It advances your science because you get to be exposed to new disciplines and interact with experts in completely different fields from yours, who may look at the same problem differently or generate ideas you would never have thought of. Real advances often happen as a result of these collaborations, and it’s inspiring to get to see scientific breakthroughs happening in real time. It’s a major factor that makes me so satisfied in my work. Getting to have such global experiences as part of science also advances your own personal development and growth. You get to try out new things and thus develop your own unique interests. You make connections with such a variety of people and take away the very best from all of them to apply in your own life. I’m very fortunate and wouldn’t be where I am today without these experiences.

7. In research, a single question can change everything. Can you share a moment when digging deeper — asking “why?” or “what if?” — shifted the direction of your work?

My work often starts by asking “why” or “what if” about some interesting feature of the ocean in the past, gleaned from what’s called “proxy” data (e.g., the changing chemical make-up of ocean sediments down through a drill core can tell you about the ocean’s chemistry back in time when those sediments were laid down, thus being a “proxy” for past ocean chemistry). Climate and ocean models can then be used to answer “why.” Why was the ocean that much more acidic X-millions of years ago? What if this circulation pattern was dramatically weakened, like the proxy data suggests? What would happen then? For example, in one part of my Ph.D., we had some proxy data showing that the Pacific circulated in a dramatically different way during Earth’s past ice ages, circulating much more vigorously. We wondered whether this would allow the Pacific as a whole to hold more or less CO2 . We simulated the ocean in a model and gave the Pacific a stronger circulation (finding that it did help the ocean hold more CO2 , drawing CO2 out of the atmosphere and contributing to the cold ice age climate!), and after this, I was hooked on modeling. The ability to ask “what if” and then actually test and see your hypothesis play out in a model was the exact kind of work I wanted to do. This marked the point when I pivoted from paleoclimatology (and being primarily lab-based) to modeling and questions of physical oceanography.

8. Scientific progress also often includes setbacks. What’s one challenge in your work that taught you resilience or sparked a new approach?

The first half of my Ph.D. was exclusively lab-based, which I actually found very challenging. In preparing your samples, you have to carry out many steps in a complicated chemical procedure before finally analyzing them on wildly complex machines. Chemistry never actually came very naturally to me, and this made both troubleshooting and even routine day-to-day work in the lab very difficult and draining. Meanwhile, most of my labmates seemed not to mind, or even enjoy it. I was at first very hard on myself, telling myself it would be easier if I were just smarter or better at chemistry, and I viewed my “failure” to thrive in the lab as a major setback to my work. However, I soon realized there was no sense fighting an uphill battle, especially when there are so many other fields and ways to contribute to science. This realization largely helped me make the switch to modeling. So, while resilience is crucial and got me through those difficult lab years, I would also caution aspiring scientists to be self-aware and not push through on a difficult path just for the sake of it. “Setbacks” are not setbacks if they point you in a new, more productive direction.

9. Harpeth Hall’s vision statement speaks to discovering oneself and embracing strengths. How has curiosity shaped who you are beyond your scientific pursuits?

Curiosity has absolutely not only shaped my career trajectory (bouncing me around different disciplines) but my life’s path as a whole. By being open to new experiences, it gave me the courage to not always follow the conventional path. For instance, I took a year off both before and in the middle of college, which afforded me lots of new experiences and helped me develop my interests, both in and out of science. Going abroad for graduate school was also as largely a personal decision as it was a career-based one, and it has made me very happy. I enjoy living in the U.K. and have found an excellent community of friends and colleagues here. Musing on all this, I’ve come to realize that you can be curious in your day-to-day life or in a task at hand, but you can also be curious in your life path and where you allow yourself to go, if the opportunity presents itself. For me, it has made all the difference in both my work and personal life.

10. For our students and alumnae with scientific dreams, what advice would you give about pursuing curiosity with confidence?

My advice is to follow your curiosity and passions, and not your doubts. When you’re doing something you love, you can overcome any challenge, but it can be a long road to find what that thing is. So don’t shut yourself off from anything just because you think you can’t do it or won’t be good at it. Also, don’t compare yourself to others. This is a recipe for self-doubt and can really take away from the joys of doing science while doing nothing to serve you or make your science better. Remember that science is difficult for everyone (whether they show it or not!), and as long as you enjoy the topic you’re studying, then you’re right where you belong. Finally, be open to unconventional paths or changes in direction when things go wrong, which they inevitably will. Failure is so common — whether it’s not getting into a dream school or dream job, or being rejected for a large grant proposal, or anything — but if you stay open to all the opportunities around you, then you can still find your way to where you want to go.

This article appears in the Winter 2025-2026 issue of Hallways, Harpeth Hall's bi-annual publication.