The Earth is currently experiencing a profound global-scale change in its carbon and water cycles caused by anthropogenic greenhouse gas emissions and global warming. To predict and mitigate these changes, we need a better understanding of the processes controlling these biogeochemical cycles, both in the present and under different climate conditions in the past. My research works to develop and apply isotopic analyses of specific molecules as a tracer for changes in the carbon and water cycles. The ratios of carbon and hydrogen isotopes in individual molecules provide excellent tracers for the movement and metabolism of carbon and water across time and space. My research program is currently organized around applying isotopic geochemistry in four overlapping topics: 1) Carbon storage and export in terrestrial ecosystems; 2) Methane production and atmospheric emissions; 3) Characterizing past hydrological change and its effect on human societies; and 4) Understanding globally warm climates in Earth’s past.
Carbon storage and export in terrestrial ecosystems
Terrestrial ecosystems store vast reservoirs of carbon that are sensitive to environmental change, and isotope measurements are valuable for understanding the processes that control the size and stability of these reservoirs. Recently, increasing attention has turned to lakes and rivers as crucially important components of terrestrial carbon cycling, and much of my research focuses on these inland waters. Much of my current research on this topic is focused on permafrost environments, given the potential for a large carbon-cycle feedback as thawing permafrost releases aged carbon. But members of my group are studying terrestrial carbon cycling in other environments, including research on the sources of carbon in lava caves in California and the uptake of volcanic CO2 by trees.
The processes controlling methane production and atmospheric emission:
Methane is an important biological substrate, a key global source of energy, and a powerful greenhouse gas, and therefore is of critical importance in many areas of the geosciences. Research in my lab is focusing on developing and integrating isotopic tracers for methane sources, including both natural and anthropogenic emissions to the atmosphere. In addition to research on permafrost methane emissions, this includes a developing collaboration with Environment and Climate Change Canada to perform the first 14C measurements of atmospheric methane in Canada. The primary target of this research will be to quantify regional fugitive emissions of methane from oil and gas extraction in western Canada.
The impacts of past hydrological change on human societies:
One of the impacts of future global warming that is likely to have the strongest societal impact is increased drought frequency and intensity. We can gain insights into the societal impacts of long-term drought by examining past periods of hydrological change during human history. Current work on this topic includes developing analyses of organic geochemical markers for human waste, and combining these measurements with paleoclimatological proxies in lake sediment cores. Members of my research group are also developing projects to better calibrate and apply plant wax hydrogen isotope measurements as tracers of past climate change in the Arctic Ocean and in Central American lakes.
Characterizing globally warm climates in the past
Past periods of globally warm climate in Earth’s history provide important analogues for understanding future global warming. Previously I have analyzed isotopic measurements of carbonate fossils to study the distribution of ocean temperatures during the Eocene epoch, with a particular focus on understanding why temperature differences between the poles and the tropics were much smaller than in the current climate. More recently my group has performed some of the first isotopic analyses of plant-wax lipids from the Cretaceous-Paleogene Boundary to understand water and carbon-cycle changes associated with one of the Earth’s largest mass extinction events.