Tundra photosynthesis captured by satellite-observed solar-induced chlorophyll fluorescence

Creators: Luus, K. A.; Commane, R.; Parazoo, N. C.; Benmergui, J.; Euskirchen, E. S.; Frankenberg, C.; Joiner, J.; Lindaas, J.; Miller, C. E.; Oechel, W. C.; Zona, D.; Wofsy, S.; Lin, J. C.

Abstract

Accurately quantifying the timing and magnitude of respiration and photosynthesis by high-latitude ecosystems is important for understanding how a warming climate influences global carbon cycling. Data-driven estimates of photosynthesis across Arctic regions often rely on satellite-derived enhanced vegetation index (EVI); we find that satellite observations of solar-induced chlorophyll fluorescence (SIF) provide a more direct proxy for photosynthesis. We model Alaskan tundra CO2 cycling (2012–2014) according to temperature and shortwave radiation, and alternately input EVI or SIF to prescribe the annual seasonal cycle of photosynthesis. We find that EVI-based seasonality indicates spring "green-up" to occur nine days prior to SIF-based estimates, and that SIF-based estimates agree with aircraft and tower measurements of CO_2. Adopting SIF, instead of EVI, for modeling the seasonal cycle of tundra photosynthesis can result in more accurate estimates of growing season duration and net carbon uptake by arctic vegetation.

Additional Information

© 2017 American Geophysical Union. Accepted manuscript online: 16 January 2017; Manuscript Accepted: 12 January 2017; Manuscript Revised: 27 December 2016; Manuscript Received: 14 August 2016. The authors wish to acknowledge contributions from the OCO-2 and GOME-2 teams. Funding from NSERC through a Postdoctoral Fellowship (KAL) is gratefully acknowledged. Some of the research described in this paper was performed for the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE), an Earth Ventures (EV-1) investigation, under contract with NASA. A portion of the research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Data from Imnavait, Alaska, were provided by E. Euskirchen, C. Edgar, and M.S. Bret-Harte and collected through a grant from the National Science Foundation Collaborative Research on Carbon, Water, and Energy Balance of the Arctic Landscape at Flagship Observatories in Alaska and Siberia. Eddy covariance and meteorological observations from Barrow and Atqasuk were provided by W. Oechel, D. Zona, and the Global Change Research Group. Funding and support were provided by CARVE subcontract 1443296, under contract with NASA, and by the NASA grant, award NNX16AF94A, Arctic-Boreal Vulnerability Experiment (ABoVE) to W. Oechel and by Division of Polar Programs of the National Science Foundation (NSF) (award 1204263) to D. Zona. NCEP Reanalysis data were provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at http://www.esrl.noaa.gov/psd/. The MODIS MOD13A1, MOD10A2, and MOD09A1 data products were retrieved from the online Data Pool, courtesy of the NASA Land Processes Distributed Active Archive Center (LP DAAC), USGS/Earth Resources Observation and Science (EROS) Center, Sioux Falls, South Dakota, https://lpdaac.usgs.gov/data_access/data_pool. MOD17A2 GPP was provided by the Numerical Terradynamic Simulation Group (NTSG) at the University of Montana. We wish to thank the Oak Ridge National Lab for hosting open access to all Alaskan PolarVPRM outputs presented here, which can be downloaded from Luus and Lin [2016].

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Published - Luus_et_al-2017-Geophysical_Research_Letters.pdf

Supplemental Material - 2016GL070842-sup-0001-TextSI-S01_AA.pdf

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