The Earth’s climate has changed drastically throughout history. One striking example occurred 20,000 years ago during the last Ice Age when massive ice sheets covered much of North America. Because the advance and retreat of the ice sheets affect the ocean, studying the history of the ocean can provide insights into how the climate has changed because of natural causes.
On Thursday, June 21, at 7:00 p.m., at the University of Delaware College of Marine Studies in Lewes, Katharina Billups, assistant professor of oceanography, will present “Ocean History through the Microscope.” The presentation is part of the Ocean Currents Lecture Series, held monthly at the Lewes campus through September.
Billups quotes Winston Churchill who says, “The farther backward you can look, the farther forward you can see,” as a reason for studying the history of the ocean. “If we study how the ocean has affected the climate when only natural changes were a factor,” says Billups, “then we can look to the past to help unlock the mysteries of how our climate may change from human activity.”
During her talk, Billups, who joined the college last year, will describe how she conducts chemical analyses on the shells of one-celled organisms, called foraminifera (forams), to reconstruct the history of the ocean. Although forams are still among the most plentiful marine organisms in the ocean today, there are some areas of the deep sea where the bottom sediments are composed almost exclusively of the shells of forams that lived thousands of years ago. Information about the water in which these organisms lived is recorded in the chemistry of their shells.
Billups will show slides of how deep-sea drilling equipment is used to collect cores, or samples, of sediments from the bottom of the ocean. Once the core samples are retrieved, laboratory analyses are conducted to determine the ratio of oxygen-18 and oxygen-16 — two varieties of oxygen atoms called isotopes — that are present in the shells. Billups will explain how this ratio is used to paint a picture of the ocean’s history.
“The isotope ratio in the shell is dependent on two things — the amount of ice that is present at the poles and also on the temperature of the water. For example, during periods of glaciation, seawater has a higher concentration of oxygen-18. The lighter isotope, oxygen-16, tends to evaporate more easily from the water and then falls as snow at the poles and gets locked up in the ice,” says Billups. “Therefore, if the shells are high in oxygen-18, then the forams lived during a period of glaciation, in cold water, or in both. The tricky part is being able to distinguish between these two effects.”
Billups earned her doctorate in Earth sciences from the University of California in Santa Cruz and a bachelor’s and master’s degree in geology from the University of California in Davis. Prior to joining CMS, she completed a postdoctoral fellowship at Harvard University in Cambridge, Massachusetts.
The lecture will begin at 7:00 p.m. in Room 104, Cannon Laboratory, at the Hugh R. Sharp Campus, 700 Pilottown Road, Lewes. The hour-long talk will be followed by light refreshments.
While the lecture is free and open to the public, seating is limited and reservations are required. To reserve your seat, please contact the college at (302) 645-4279.