#7 Climate, Carbon, Iron and the Ocean

Daniel Sigman, Ph.D.

Daniel Sigman is an American geoscientist, and the Dusenbury Professor of Geological and Geophysical Sciences at Princeton University.  Sigman received a MacArthur Foundation “genius grant” in 2009. He studies the global cycles of biologically active elements, in particular, nitrogen and carbon, and he is active in the development of analytical techniques for studying nitrogen in the environment. He also investigates the history of these cycles in order to understand the causes of past changes in the atmospheric concentration of carbon dioxide, the role of this greenhouse gas in the waxing and waning of ice ages, and the ocean’s response to climate change.

February 27, 2017 - 9:00 a.m. - 3:00 p.m.

Daniel Sigman, Ph.D., Department of Geosciences

“Give me a half tanker of iron, and I will give you an ice age.” With this proclamation, the chemical oceanographer John Martin entered the fray on the complex debate as to how humans might mitigate global warming by drawing carbon dioxide out of the atmosphere. We will discuss the ongoing rise in atmospheric carbon dioxide concentrations, the environmental consequences of this rise (most importantly, global warming), and the proposals that have been put forward to halt the rise in atmospheric greenhouse gases, including Martin’s proposal of purposeful “iron fertilization” of the ocean. We will then dig into the science behind iron fertilization, including the controls on the ocean’s biological productivity and the surprising reasons that algae in the ocean are starved of iron (hint: it has to do with the biological invention of photosynthesis early in Earth’s history).

I will also tell you about my work to address whether iron fertilization occurred during past ice ages. We will finish by hashing out a list of topics the broad vein of possible ways to slow the rise of greenhouse gases, with the goal of using scientific concepts to help students prioritize that list.