Ancient Climate Change

How does past climate change on the California coast help us understand and predict future climate scenarios?

Examinations of tar deposits from sediment cores taken off the Santa Barbara coast by Tessa Hill, associate professor with the Bodega Marine Laboratory, suggest that global warming may have melted undersea methane ice, disturbing the sea floor and opening new cracks that allowed petroleum and methane to bubble to the surface. Hill collects coral skeletons and deep sea sediments as records of past climate events. Corals can live for hundred of years, preserving a high-resolution record of environmental conditions, including processes like El Nino and anthropogenic warming. Deep sea sediments provide an even longer record, going back tens of thousands of years. For example, Hill investigated whether undersea emissions of methane increased during periods of global warming from 14,000 to 16,000 and from 10,000 to 11,000 years ago. These are the most dramatic warming periods in Earth’s recent history, when glacial eras gave way to more moderate temperatures.


Has climate change affected all freshwater lakes in the same way over time?

It is necessary to investigate the impacts of a broad range of latitudinal and altitudinal gradients. A project by Geoff Schladow, director of the Tahoe Environmental Research Center, and collaborators in Chile, Japan and Pacific Rim nations, uses both water column data and sediment data, allowing for the investigation of responses dating back tens to hundreds of thousands of years.


How can researchers use ice core records more accurately?

In the past it was thought that most of the material deposited in snow was preserved without significant changes. However, more recent work, including studies by Cort Anastasio, professor of land, air, and water resources, has shown that reactions in surface snow can change the composition of the snow grains as well as the surrounding air. Anastasio’s research group is characterizing these changes for several important tracers, such as hydrogen peroxide and nitrate, that will help other researchers more accurately read ice core records of past atmospheres.


What are the latest methods for reconstructing the history of the Earth’s climate?

Molecular-level tools have the capability of transforming our understanding of how isotopes can be used to unravel the history of Earth’s climate. Jim Rustad, professor emeritus of geology, uses the distribution of stable isotopes among minerals, water and the atmosphere as important indicators of climate change. Doing so allows him to see back in time much further than is possible from data obtained from ice cores. His research uses a cross between computer science and chemistry — called computational chemistry — to improve the reliability of these isotopic methods in soil minerals and ocean sediments. Rustad’s group is carrying out calculations that start at the level of established laws of quantum mechanics to determine isotope distributions for the ratio of boric acid to borate, which serves as a “paleo-pH meter.” He also uses dissolved aqueous carbonates and trace carbonate components in soil minerals.

UC Davis Logo