B14A-05 – Influence of Phosphorus Cycle Coupling on Carbon–Climate Feedbacks (Invited)


Xiaojuan Yang (yangx2 at ornl dot gov)
Oak Ridge National Laboratory
Peter Thornton
Oak Ridge National Laboratory
Daniel Ricciuto
Oak Ridge National Laboratory
Forrest Hoffman
University of California Irvine; Oak Ridge National Laboratory

Monday, December 15, 2014 05:00 PM – 05:15 PM
Moscone West 2002

It is being increasingly recognized that carbon-nutrient interactions play important roles in regulating terrestrial carbon cycle responses to increasing CO2 in the atmosphere and climate change. Nitrogen-enabled models in CMIP5 indicated that the inclusion of nitrogen cycle reduces CO2 fertilization effect and warming-induced carbon loss from land ecosystems. None of the CMIP5 models has considered phosphorus (P) as a limiting nutrient. Phosphorus has been commonly considered to be the most limiting nutrient in lowland tropical forests. Only recently a few land models have considered P dynamics and C-N-P interactions (CASA-CNP, JSBACH-CNP and CLM-CNP) and these models show strong P limitation in tropical forest responses to increasing atmospheric CO2. In this study, we have performed a set of offline global-scale simulations using CLM-CNP constrained by realistic maps of phosphorus distribution. We examine the influence of including phosphorus cycle dynamics and C-N-P interactions on C–climate feedbacks. We illustrate the spatial patterns of dominant nutrient limitation (N-limited vs. P-limited) on the global scale. We show that P-limitation dominates over most of the tropics and sub-tropics, while N limitation dominates over most of the temperate and high-latitude regions. We also show that phosphorus cycle coupling reduces the sensitivity of net carbon exchange to variations in both temperature and precipitation.

Forrest M. Hoffman (forrest at climatemodeling dot org)