Long-term Air Pollution Trends and Sources
Ice core records from Greenland, the Canadian Arctic, and the European Alps show conclusively that heavy metal (Hg, Pb, Cd, Cu, Zn), SOx and NOx pollution have risen dramatically from low natural levels to modern polluted levels due primarily to fossil fuel combustion and industrial smelting. Most of these atmospheric pollutants peaked in concentration in the early 1970s and have been declining ever since due to the adoption of pollution abatement legislation in North American and Western European nations (e.g. 1970 Clean Air Act). However, our ice core records from the Saint Elias Mountains show that North Pacific levels of Pb, As, and Bi have been rising since the 1970s due to trans-Pacific pollution from Asia, contrasting dramatically with the recent falling pollution trends in the North Atlantic region.
Sam Beal’s 2015 paper on changes in atmospheric mercury concentrations in the Mt. Logan ice core allows us to better understand the natural cycling and human emissions of this element over the last 600 years.
Publications: Beal et al., 2015; Gross et al., 2012; Osterberg et al., 2008
Primary Productivity in the North Pacific
Satellite data has shown a decrease in 20th century primary productivity in the North Pacific, one of the most biologically productive marine ecosystems in the world, but long-term variability in primary productivity is not well constrained. David Polashenski, an undergrad at the time, collected evidence to develop an ice core proxy for primary productivity in the North Pacific. Phytoplankton (i.e. algae) emit dimethyl sulfide, which is oxidized in the atmosphere into methanesulfonic acid (MSA) and preserved in the ice core record. Using the Denali Ice Core and a model to track moisture sources, we showed that MSA concentrations can be used as a proxy for North Pacific marine primary productivity levels.
Publications: Polashenski et al., 2018
Lyme disease and Climate Change
We are working with Professor Jonathan Winter to study the spread of Lyme disease through the development of a next-generation model. Our aim is to understand the relative importance of climate change, land-use patterns, and host dynamics in the rapid northward spread of the disease over recent years (see figure).
Publications: Winter et al., 2020; Wallace et al., 2019
