Michael Beman, University of California, Merced
Human activities have fundamentally altered the chemistry of the atmosphere and ocean, ultimately pushing our planet into a new geological period known as the ‘Anthropocene.’ While human-driven increases in atmospheric carbon dioxide (CO2) concentrations—and their strong connection with climate change—are well-known, atmospheric nitrous oxide (N2O) concentrations have increased in parallel with CO2. N2O is both a strong greenhouse gas and the dominant destroyer of stratospheric ozone; the steady increase in N2O concentrations is driven primarily by agricultural fertilization, yet N2O is produced by multiple microbial groups that interact in complicated ways, and that may respond to other forms of environmental change. At the same time, climate change is not the only effect of elevated CO2: 25-33% of human-generated CO2 dissolves in the ocean, where it forms a weak acid and reduces ocean pH—a process known as ‘ocean acidification.’ pH is fundamental for ocean chemistry and ocean organisms, and changes in dissolved nutrients, metals, and forms of inorganic carbon are an expected consequence of future ocean acidification. Ocean pH is projected to decline by 0.3-0.4 units by the end of the century, producing wide-ranging effects that include reduced calcification in corals, shellfish, and phytoplankton; altered physiology in fish and other animals; and changes in ocean biogeochemical cycles. In this overview talk, I will present the drivers behind ocean acidification and increased N2O, the underlying dynamics of these changes, their projected effects, and their ultimate interactions.
Kavli Frontiers of Science, 3 February 2013. Presentation.