Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published August 2015 | Published
Journal Article Open

Influence of ENSO and the NAO on terrestrial carbon uptake in the Texas-northern Mexico region

Abstract

Climate extremes such as drought and heat waves can cause substantial reductions in terrestrial carbon uptake. Advancing projections of the carbon uptake response to future climate extremes depends on (1) identifying mechanistic links between the carbon cycle and atmospheric drivers, (2) detecting and attributing uptake changes, and (3) evaluating models of land response and atmospheric forcing. Here, we combine model simulations, remote sensing products, and ground observations to investigate the impact of climate variability on carbon uptake in the Texas‐northern Mexico region. Specifically, we (1) examine the relationship between drought, carbon uptake, and variability of El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) using the Joint UK Land‐Environment Simulator (JULES) biosphere simulations from 1950–2012, (2) quantify changes in carbon uptake during record drought conditions in 2011, and (3) evaluate JULES carbon uptake and soil moisture in 2011 using observations from remote sensing and a network of flux towers in the region. Long‐term simulations reveal systematic decreases in regional‐scale carbon uptake during negative phases of ENSO and NAO, including amplified reductions of gross primary production (GPP) (−0.42 ± 0.18 Pg C yr^(−1)) and net ecosystem production (NEP) (−0.14 ± 0.11 Pg C yr^(−1)) during strong La Niña years. The 2011 megadrought caused some of the largest declines of GPP (−0.50 Pg C yr^(−1)) and NEP (−0.23 Pg C yr^(−1)) in our simulations. In 2011, consistent declines were found in observations, including high correlation of GPP and surface soil moisture (r = 0.82 ± 0.23, p = 0.012) in remote sensing‐based products. These results suggest a large‐scale response of carbon uptake to ENSO and NAO, and highlight a need to improve model predictions of ENSO and NAO in order to improve predictions of future impacts on the carbon cycle and the associated feedbacks to climate change.

Additional Information

© 2015. American Geophysical Union. Received 23 FEB 2015. Accepted 25 JUL 2015. Accepted article online 28 JUL 2015. Published online 24 AUG 2015. CRU‐NCEP climate information is obtained from ftp://nacp.ornl.gov/synthesis/2009/frescati/model_driver/cru_ncep/analysis/readme.htm. ENSO and NAO indices are obtained at NOAA CPC (http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml). JULES model output and CRU‐NCEP data are provided by A. Harper (A.Harper@exeter.ac.uk). SMOS data are available for data access at http://catds.ifremer.fr/Products/Products‐access. Chlorophyll fluorescence data were provided by C. Frankenberg (Christian.Frankenberg@jpl.nasa.gov). MPI‐BGC data set was provided by M. Jung (martin.jung@bgc‐jena.mpg.de). MODIS MOD17 GPP data are available at http://www.ntsg.umt.edu/project/mod17. GRACE land data are available at http://grace.jpl.nasa.gov. Flux tower data are collected/processed by M. Litvak (marcy.litvak@gmail.com) and gap‐filled/partitioned by S. Wolf (sewolf@berkeley.edu). We acknowledge all MODIS land product science team members for providing an invaluable public data set. The improved MOD17 GPP data were provided by the Numerical Terradynamic Simulation Group at the University of Montana. We thank the Global Carbon Project and TRENDY modelers for contributing model output. We also give special thanks to S. Sitch and P. Friedlingstein for organizing TRENDY. GRACE land data processing algorithms were provided by S. Swenson and supported by the NASA MEaSUREs Program. SMOS data were obtained from the Centre Aval de Traitement des Données SMOS (CATDS), operated for the Centre National d'Etudes Spatiales (CNES, France) by IFREMER (Brest, France). S. Wolf acknowledges support from a Marie Curie International Outgoing Fellowship. T.F. Keenan acknowledges support from a Macquarie University Research Fellowship. M. Litvak acknowledges support from NASA ROSES Program. We give special thanks to A. Mialon for providing assistance in the processing and interpretation of the SMOS data set. This research was funded by the NASA Atmospheric CO_2 Observations from Space (ACOS) program (grant NNX10AT42G) and carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA © 2014.

Attached Files

Published - Parazoo_et_al-2015-Global_Biogeochemical_Cycles.pdf

Files

Parazoo_et_al-2015-Global_Biogeochemical_Cycles.pdf
Files (1.7 MB)

Additional details

Created:
August 22, 2023
Modified:
October 19, 2023