PAOC Colloquium: Galen McKinley (Lamont-Doherty Earth Observatory)

Diagnosing change in the ocean carbon sink

Abstract: Since preindustrial times, the ocean has absorbed an excess of carbon equivalent to 41% of cumulative fossil fuel emissions, and thus has significantly slowed atmospheric CO₂ growth and the resulting climate change. Ocean carbon uptake is expected to grow substantially through 2100. Thus, international climate policy efforts require the carbon cycle science community to regularly diagnose ocean carbon fluxes and to distinguish changes in atmospheric CO₂ due to natural variability from changes due to emission cuts. Our analysis of 35 years of surface ocean pCO₂ observations illustrates significant large-scale variability on interannual to decadal timescales. If the expected long-term growth in the ocean carbon sink is to be directly detected, the growth signal must emerge from the noise of this variability. We predict emergence timescales using a large ensemble of the NCAR climate model (NCAR-LENS). The forced trend in carbon uptake is largest and emerges most quickly at the high latitudes. In the subtropics, the sink grows slowly and does not emerge until late in the century. Surface ocean pCO₂ observations indicate carbon sink growth consistent with the predicted emergence only in the North Pacific; elsewhere, variability continues to dominate.

About the Speaker: Professor McKinley studies the mechanisms of the carbon cycle in the global oceans and Great Lakes, with her research lying at the intersection of physical and chemical oceanography. Her primary tools are numerical models and analysis of large datasets. More specifically, her research addresses the physical drivers of ecosystem and carbon cycle variability in the North Atlantic, global oceans and Great Lakes. Professor McKinley is a member of the faculty at Columbia University and the Lamont Doherty Earth Observatory; she was previously at University of Wisconsin – Madison. In addition to research and teaching, Professor McKinley frequently contributes to national and international scientific coordination and offers scientific advice to policy-makers.

About this Series: The PAOC Colloquium is a weekly interdisciplinary seminar series that brings together the whole PAOC community. Seminar topics include all research concerning the physics, chemistry, and biology of the atmospheres, oceans and climate, but also talks about e.g. societal impacts of climatic processes. The seminars generally take place on Monday from 12-1pm. Lunch is provided to encourage students and post-docs to meet with the speaker. Besides the seminar and lunch, individual meetings with professors, post-docs, and students are arranged.