Keeling, Ralph: UCSD Scripps Institution of Oceanography (Project Lead)
Project Funding:
2017 - 2020
NRA: 2016 NASA: Carbon Cycle Science
Funded by NASA
Abstract:
This proposal seeks to understand terrestrial ecosystem processes that control the exchanges of CO2 with the atmosphere on decadal and longer time scales. The approach makes time series measurements of CO2 concentration and isotopes and uses these and other datasets to challenge and improve carbon cycle models, including earth system models. This proposal is responsive to the solicited research Theme #1, relating to carbon cycling in Arctic and boreal regions, particularly to changes brought about by warming, CO2 and nitrogen fertilization, and associated changes to hydrology and carbon storage. It is also responsive to the need for “cross-cutting research activities”, e.g. for improving observations by providing an archive of CO2 samples to support development of novel isotopic applications related to land carbon cycling, and it is responsive to the need for modelling studies in relation to atmospheric transport modelling, ecosystem component modelling, regional and global modelling.
This proposal would provide core support for the measurement activities of the Scripps CO2 program, which sustains measurements from a flask sampling program from an array of ten stations distributed from the Arctic to the Antarctic including the iconic Mauna Loa continuous record. The program complements the larger NOAA ESRL program by providing critical redundancy for state of the art measurements, by ensuring continuity of the longest records of critical importance, and providing interpretive capabilities for understanding the data significance. The program also complements the DOE modelling (ACME) and measurements programs (NGEE-Arctic, FACE, Ameriflux) by providing cross cutting constraints on large-scale carbon cycling and it is highly relevant to the DOE Scientific Focus Area on Biogeochemistry–Climate Feedbacks. By sustaining the longest records of CO2 and isotopes and advancing related interpretive capabilities, the Scripps program is well positioned to make agenda setting discoveries related to carbon cycling and carbon/climate feedbacks.
In addition to supporting the continuation of these observations and their improvement, this proposal will support a collaboration with Drs. Peter Thornton and Lianhong Gu of ORNL which builds on two recent significant discoveries from the program. The first is the evidence of the large increase in the seasonal amplitude at high northern latitudes documented by Graven et al. (2013). The second is emergent evidence for a shift towards higher photosynthetic discrimination both globally and at high northern latitudes. Both discoveries are highly relevant for understanding ongoing changes in arctic and boreal ecosystems. Both potentially provide critical insights into the coupled carbon, nitrogen, and water cycling in the context of ongoing changes. The collaboration will entail combined data synthesis and modelling activities, taking advantage of recent advances in global and plant-level modelling capabilities at ORNL. The collaboration is aimed at answering these key questions:
1) How can the observed seasonal cycles in CO2 concentration be used to constrain the representation of nitrogen cycling within land surface models?
2) How does the formulation of nitrogen cycling in models impact the predicted photosynthetic discrimination on seasonal time scales?
3) What plausible changes in leaf level processes can account for the long-term changes in photosynthetic discrimination suggested by atmospheric data?
Publications:
Keeling, R. F., Graven, H. D. 2021. Insights from Time Series of Atmospheric Carbon Dioxide and Related Tracers. Annual Review of Environment and Resources. 46(1), 85-110. DOI: 10.1146/annurev-environ-012220-125406
Keeling, R. F., Graven, H. D., Welp, L. R., Resplandy, L., Bi, J., Piper, S. C., Sun, Y., Bollenbacher, A., Meijer, H. A. J. 2017. Atmospheric evidence for a global secular increase in carbon isotopic discrimination of land photosynthesis. Proceedings of the National Academy of Sciences. 114(39), 10361-10366. DOI: 10.1073/pnas.1619240114
Rodenbeck, C., Zaehle, S., Keeling, R., Heimann, M. 2018. History of El Nino impacts on the global carbon cycle 1957-2017: a quantification from atmospheric CO
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data. Philosophical Transactions of the Royal Society B: Biological Sciences. 373(1760), 20170303. DOI: 10.1098/rstb.2017.0303
Wang, K., Wang, Y., Wang, X., He, Y., Li, X., Keeling, R. F., Ciais, P., Heimann, M., Peng, S., Chevallier, F., Friedlingstein, P., Sitch, S., Buermann, W., Arora, V. K., Haverd, V., Jain, A. K., Kato, E., Lienert, S., Lombardozzi, D., Nabel, J. E. M. S., Poulter, B., Vuichard, N., Wiltshire, A., Zeng, N., Zhu, D., Piao, S. 2020. Causes of slowing-down seasonal CO
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amplitude at Mauna Loa. Global Change Biology. 26(8), 4462-4477. DOI: 10.1111/gcb.15162
More details may be found in the following project profile(s):
