January 15, 2003

Personal Statement of Julie Pullen

My mother tells how as a child I would come home from school every spring day and immediately go outside to the dirt road in front of our house in order to cast objects into the streams formed by the spring snow melt.  I never tired of watching the flow be redirected and change course in response to obstacles.  And I delighted in tracing where the meandering path of the water would deposit the floating twigs.

My drive to understand the patterns of response and behavior, in both physical and biological systems, has been a cord linking almost everything I have done.  The search to organize and communicate that understanding has been a major focus of my life.

I “discovered” the nascent Santa Fe Institute (SFI) when I was a sophomore in college and had the opportunity to study there under the direction of Stuart Kauffman, an evolutionary biologist.  Working along with a visiting biologist and an economist I conducted cellular automata simulations of an idealized single-species ecosystem.  In that model I explored how the spatial distribution of “food” in the environment (heterogeneous vs. homogeneous) influenced the evolution of the strategies of the “animals.”

As I was continuing advanced undergraduate coursework in math and physics, I also started taking graduate courses in biology.  One such course lasted all summer and was held at the Friday Harbor Marine Lab on San Juan Island.  The course focused on the developmental stages of marine invertebrates.  We watched and recording living organisms move through the early cell stages.  I was intrigued to learn that the spatial location of the embryonic cells determined how the cell fate unfolded.  I spent the summer after my junior year of college using a flow tank to investigate how the shape of barnacle clusters related to the feeding behavior expressed by barnacles in unidirectional and oscillating flow.  I wrote and published my first scientific paper about those experiments.

I enjoyed splashing in the intertidal zone and in flow tanks, but I was also keenly interested in developing my numerical skills so that I could predict the response of larger-scale fluid environments, like the ocean.  I ultimately earned an M.S. in applied mathematics and a Ph.D. in physical oceanography, specializing in coastal ocean modeling. 

While in school I seized many opportunities to teach others.  This included teaching or assisting in teaching both graduate and undergraduate courses and volunteering at community outreach events to describe our studies of the ocean world and its connection to the earth as a whole.  I really enjoy the feeling of watching a student or child internalize a concept – really grasp what I am explaining – and say it back to me in a way that deeply makes sense to them.  It is such a wonderful sensation. 

I volunteered on several research cruises during my time in graduate school.  One of them was a marine geology cruise off northern California.  I appreciated the challenge of being on the ocean, sometimes during really inclement weather, and working hard to ensure that as much quality data as possible was collected.  And I went on to use that data in my Ph.D. work to evaluate the impact of the resolution of the ocean model on prediction capability.  In that work I was able to explain the operative physical dynamics of the coastal circulation off northern California – why the ocean moves the way it does.  In the process of carrying out my research, I assisted the geologists in interpreting the transport pathways of the sediment delivered to the ocean by floods of the local river. 

What gets me the most excited about my field is how truly interdisciplinary the studies of the ocean need to be, and will increasingly become in the future.  I’ve taken graduate courses in the other disciplines of marine science: biological oceanography, chemical oceanography, and geological oceanography and am constantly seeking ways to connect the branches.  In addition, I’ve taught undergraduate marine studies with an interdisciplinary team of teachers. 

In my postdoctoral research I worked predominantly with meteorologists.  Then and now, I am helping to make connections among an international group of scientists with very different disciplinary backgrounds so we can better predict the circulation in the Mediterranean Sea.  I continue to collaborate with sediment geologists in my modeling of the northern Adriatic so that we can mine my results to deepen our understanding of the local ocean currents that move sediments, and I can use their data about the currents to confirm the predictions of my model.  Recently I completed work that documented the impact of the resolution of the meteorological forcing on the ability of the ocean model to create quality forecasts of the state of the sea.

I tend to view the ocean as a place that incubates interactions – more of a systems view that erases discipline boundaries.  I think some of the most fascinating questions lie at the interface between the realms: the boundaries between the air and the ocean, and the ocean and the sediment bottom, as well as the interaction of the biology with the fluid flow surrounding it. 

The structure of the environment molds certain responses: the motion of the atmosphere creates the complex patterns of ocean circulation, and the movement of water determines the fate of sediment, and the behavior of organisms.  However the environment is also influenced by the interaction: the winds respond to the surface ocean temperature, while the sediments and creatures contribute to the density of the water in the ocean.

Intrinsically the fluctuations in the environment and the reciprocal interactions nurtured by the environment operate on multiple scales – thus necessitating high-resolution computer models to approach a full understanding and to acquire a forecast capability.  I wondered how high the model resolution needed to be to mirror reality and to gain reasonable predictive skill.  In my research I have provided quantitative answers to these questions by varying the spatial resolution of models of both the ocean and the atmosphere. 

I return to this question again in my most recent work, although the context is different.  My current research asks what resolution is required of an atmospheric dispersion model of the urban environment in order to reliably forecast evacuation routes and regions to distribute medication in the event of a nuclear/biological/chemical (NBC) incident in a city.  Very small scales of motion are generated as a contaminant plume interacts with the urban landscape created by streets and buildings – taxing our ability to predict plume fate with certainty.  The burden on models is significant when national security is at risk.  We need to know how much we can rely on environmental forecast models when making critical decisions in an emergency, when lives are at stake.  These issues will continue to confront us as model forecasts are used increasingly in a wide range of settings to lay future plans and influence current policy.