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Kira Lawrence began working at Lafayette as an assistant professor of geology and environmental geosciences in August. Less than one month later, she began research funded by a grant from the National Science Foundation (NSF) that will be used to reconstruct long, high records of ocean surface temperatures and productivity.
The grant, totaling $96,660, will stretch over three years starting Sept. 1 and will help pay for research expenses such as student assistants.
The records will span four million to five million years and the resolution will entail approximately one sample every 3,000 years. Productivity, Lawrence notes, is a measure of the amount of organic material synthesized by organisms from nutrients present in the seawater in a given area in a given amount of time.
These records are generated by extracting lipid compounds preserved in ocean sediment, which are formed when species of phytoplankton that dwell in the ocean’s surface die, Lawrence explains.
“Characterizing ocean surface temperature provides direct information about the nature of past climate,” she says. “The productivity index is far more complicated because it is one component of the very complex global carbon cycle. The organisms that make the lipid compounds photosynthesize, sequestering carbon dioxide and making it into organic matter. What that means is that changes in ocean productivity can change the amount of carbon dioxide, an important greenhouse gas, in the Earth’s atmosphere.”
According to Lawrence, the time interval from 5 million years ago to the present witnessed a major transition in Earth’s climate. Prior to 3.5 million years ago, there was little or no year-round ice in the Northern Hemisphere and Earth’s climate was, on average, 3ºC warmer than at present. For reasons that remain unclear, between 3.5 and 2.5 million years ago, ice growth at high latitudes, particularly in the Northern Hemisphere, increased rapidly in an event called the intensification of Northern Hemisphere Glaciation, she explains.
Lawrence says that she and her collaborator, Tim Herbert, a professor at Brown University who was Lawrence’s advisor at graduate school, are ultimately trying to understand the nature of this transition to determine what exactly happened and, more importantly but much more difficult to ascertain, why it happened. The work they will do on this project is an extension of the work Lawrence did for her PhD.
“This project will provide the first systematic look at changes in ocean surface temperature in the high-latitude oceans both in the northern and southern hemispheres during the intensification of Northern Hemisphere Glaciation,” she says. “Having high resolution, continuous records of how surface temperature and ocean productivity have changed will give us a much better characterization of what happened during this transition. That information, used in conjunction with other records documenting changes in global ice volume and deep ocean circulation that have previously been generated by others, will give us much more information with which to test ideas about why this transition happened.”
Lawrence plans to involve students in her work; she is in the process of meeting geology majors at Lafayette and getting to know the students in her introductory course. She hopes to have at least two students involved in the project at any one time.
“I hope by next semester to have two students with interests in past climate and Earth’s history to be working with me on this project,” she explains. “Over the course of three years, I imagine that maybe six or more students will have been involved with the project.”
Lawrence is interested in pursuing this research because she wants to better understand how and why the Earth’s climate has changed through time.
“There are times in Earth’s history when it was much warmer and also much cooler than it is at present,” she explains. “I am out to understand what caused the climate to shift from ‘warm states’ to ‘cold states’ and visa versa. Understanding these transitions turns out to be tricky because there are so many different components to the Earth’s system that affect its climate. I am motivated to try and understand how the climate system works because climate has played and continues to play a profound role in the evolution of life on Earth.”
Lawrence has published her research on the planet’s climate changes over long timescales in journals such as Global Change Biology, Global Ecology and Biogeography, Science, and Nature. The recipient of several grants, she has conducted research at the U.S. Geologic Survey and Woods Hole Research Center. She earned Ph.D. and M.Sc. degrees in geological sciences from Brown University, an M.S. in earth sciences from University of California, Santa Cruz, and an A.B. in earth sciences from Dartmouth College.