Project Funding: 2013 - 2015

NRA: 2012 NASA: Ocean Biology and Biogeochemistry   

Funded by NASA

Abstract:
The ocean is the dominant sink for atmospheric carbon on centennial timescales. But the rate of this sink, and the potential for it to be significantly slowed by climate change, are of critical interest because they weigh heavily on future climate projections. McKinley et al. (2011) offer a promising new approach that directly considers change across interannual to the multidecadal timescales for three gyre-scale regions covering the North Atlantic, and show that previously-reported trends are best explained by climate variability. Here, we propose to extend this approach to the globe. Significant temporal change in productivity has also been observed, but we do not yet have a coherent explanation for its driving mechanisms or with respect to its impacts on carbon uptake. In terms of future projections, the CMIP5 archive of earth system model projections through 2100 needs to be confronted with data-based metrics and the most robust simulations need to be summarized with respect to future change in both productivity and carbon uptake. In this proposed work, we will (1) evaluate trends in observed surface ocean pCO2 over 16 global biomes; (2) develop mechanistic understanding of the drivers of interannual variability in both surface ocean pCO2 and productivity using in situ pCO2 data, ocean color products, and an ocean state estimate for physics; (3) develop metrics for CMIP5 models based on pCO2 trends and interannual variability mechanisms; and (4) evaluate future ocean carbon sinks from selected CMIP5 simulations. These efforts will be driven by 4 research questions and related hypotheses: Question 1: What are the trends in surface ocean pCO2, pCO2-T and pCO2-nonT globally between 1981 and 2010? What do these trends reveal about mechanisms of carbon-climate feedbacks? Hypothesis 1.1: Interannual to decadal variability dominates surface ocean pCO2 trends based on the available data. Thus, only in a few biomes can long-term equilibration with the atmosphere be discerned. Hypothesis 1.2: A significant warming component (pCO2-T) for the total pCO2 trend is most clear in the North Atlantic.  Question 2: What drives biome-scale variability in surface ocean productivity and pCO2? Does productivity change impact pCO2? Hypothesis 2.1: Mechanisms of variability are physically-driven and vary regionally. Examples include (1) stratification-driven in the subpolar North Atlantic, (2) wind-driven in the Southern Ocean, (3) ENSO-driven in the equatorial Pacific. Hypothesis 2.2: Physical variability dominates both productivity and pCO2; thus significant correlations are due to indirect mechanisms. Question 3: How well do CMIP5 Earth System models represent decadal variability in surface ocean productivity and pCO2, and driving mechanisms, from 1998 to present? Hypothesis 3.1: Physical mechanisms dominate, consistent with the observations. Question 4: In the CMIP5 ESMs that perform well mechanistically, what is predicted for future ocean carbon uptake through 2100? Hypothesis 3.1: Solubility reduction due to warming and increased stratification will be the dominant negative feedback on ocean carbon uptake. This work responds directly to ROSES 2012 A.3 Ocean Biology and Biogeochemistry s solicited investigation 2.1 Impacts On and Vulnerability Of Biological Oceanography and 2.5 Successor Studies. This is a successor study to New Investigator NNX08AR68G. This work is also aligned with the Ocean Carbon and Biogeochemistry program s currently-identified research priorities of: Climate sensitivities of and change in ecosystem structure and associated impacts on biogeochemical cycles and Ocean carbon uptake and storage.

Publications:

Fay, A. R., McKinley, G. A. 2017. Correlations of surface ocean pCO2to satellite chlorophyll on monthly to interannual timescales. Global Biogeochemical Cycles. 31(3), 436-455. DOI: 10.1002/2016GB005563

McKinley, G. A., Fay, A. R., Lovenduski, N. S., Pilcher, D. J. 2017. Natural Variability and Anthropogenic Trends in the Ocean Carbon Sink. Annual Review of Marine Science. 9(1), 125-150. DOI: 10.1146/annurev-marine-010816-060529

McKinley, G. A., Pilcher, D. J., Fay, A. R., Lindsay, K., Long, M. C., Lovenduski, N. S. 2016. Timescales for detection of trends in the ocean carbon sink. Nature. 530(7591), 469-472. DOI: 10.1038/nature16958

Muller-Karger, F. E., Hestir, E., Ade, C., Turpie, K., Roberts, D. A., Siegel, D., Miller, R. J., Humm, D., Izenberg, N., Keller, M., Morgan, F., Frouin, R., Dekker, A. G., Gardner, R., Goodman, J., Schaeffer, B., Franz, B. A., Pahlevan, N., Mannino, A. G., Concha, J. A., Ackleson, S. G., Cavanaugh, K. C., Romanou, A., Tzortziou, M., Boss, E. S., Pavlick, R., Freeman, A., Rousseaux, C. S., Dunne, J., Long, M. C., Klein, E., McKinley, G. A., Goes, J., Letelier, R., Kavanaugh, M., Roffer, M., Bracher, A., Arrigo, K. R., Dierssen, H., Zhang, X., Davis, F. W., Best, B., Guralnick, R., Moisan, J., Sosik, H. M., Kudela, R., Mouw, C. B., Barnard, A. H., Palacios, S., Roesler, C., Drakou, E. G., Appeltans, W., Jetz, W. 2018. Satellite sensor requirements for monitoring essential biodiversity variables of coastal ecosystems. Ecological Applications. 28(3), 749-760. DOI: 10.1002/eap.1682

More details may be found in the following project profile(s):

• NASA Ocean Biology & Biogeochemistry (OBB) Project Profile