Growing up in a rural part of South Korea, Jung-Eun Lee spent a lot of time looking up at the clouds. “I just loved looking at them,” she said, “and I wanted to know more about them.”
She managed to turn that fascination into a career researching Earth’s climate and hydrological cycle. She joins the faculty in Brown’s Department of Geological Sciences this fall.
Lee’s expertise is in climate models, complex supercomputer simulations of the circulation of Earth’s atmosphere. She takes real-world proxies of past climate — evidence from fossils, ice cores and other sources — and incorporates those data into the models.
“I work with geologists, paleontologists, or biogeochemists who actually measure those proxies,” she said. “My main work has been interpreting these proxies and thinking about the larger scale dynamics and what the paleoenvironment was like.”
While earning her Ph.D. in Earth and planetary science from the University of California–Berkeley, Lee worked on data gathered from Antarctic ice cores, which provide a record of precipitation that goes back about 800,000 years. Varying isotopes of hydrogen and oxygen in the samples can be used as a signal of the temperature through time. By interpreting those ratios in a climate model, Lee was able to show that Antarctica was about 50 percent colder during the last glacial maximum than previously thought.
Lee’s current interest is the role land surfaces — particularly the trees and plants that cover them — play in shaping the global climate. Understanding those processes is a growing focus of climate research, according to Lee.
“So far we’ve been looking mostly at how the oceans influence the land surface,” she said. “But when we look at the water budget over the land surface, two-thirds of the precipitation over land is recycled from the land.”
Much of that recycled water comes from trees. They serve as conduits that transfer water from underground into the atmosphere. Plant roots take up water from the soil, which is circulated to leaves. Leaves have tiny pores called stomata that they open to take in carbon dioxide, a crucial element of photosynthesis. When the stomata are open, water evaporates from the leaves, a process called transpiration.
During a postdoctoral program at the University of Chicago (2008-2010), Lee worked on a project aimed at understanding how the evolution of plant physiology influenced the climate. Flowering plants — essentially all of the trees and plants on Earth today except conifers, ferns and mosses — are relatively new to the planet, having emerged a scant 120 million years ago. Kevin Boyce, a paleontologist at Stanford who studies fossil leaves, found that paleo-plants before flowering plants had a much lower capacity for transpiration. Lee was able to incorporate that data into a climate model and show that the world before flowering plants would have been a much hotter and dryer place.
For example, she showed that Amazonian everwet forests — forests without an annual dry season — would shrink by 80 percent without water provided by flowering plants. Because everwet forests are hubs for biodiversity, the work shows how important transpiration from flowering plants has been in shaping the diversity of life on Earth today.
Following her postdoctoral studies at Chicago, Lee moved on to NASA’s Jet Propulsion Laboratory, where she used satellite imagery to further investigate the link between plants, water, and the climate. She will continue that work at Brown.
“My personal goal is to understand how biosphere and the climate system coevolve,” she said. “If you take a look at Earth’s land surface, it’s covered in plants unless the climate is too harsh. At the same time, plants can influence climate by slowing down the wind speed, changing how much energy is absorbed by Earth, and modifying the amount of water vapor in the atmosphere. I’m particularly interested in the water part: how the climate system provides enough rain to grow forests, how much water is coming out of plants, and how that water influences atmospheric convection and cloud formation.”
Even with a Ph.D. and several important publications under her belt, for Lee it still comes down to a fascination with clouds.