On the causes of trends in the seasonal amplitude of atmospheric CO2

No consensus has yet been reached on the major factors driving the observed increase in the seasonal amplitude of atmospheric CO2 in the northern latitudes. In this study, we used atmospheric CO2 records from 26 northern hemisphere stations with a temporal coverage longer than 15 years, and an atmospheric transport model prescribed with net biome productivity (NBP) from an ensemble of nine terrestrial ecosystem models, to attribute change in the seasonal amplitude of atmospheric CO2 . We found significant (p < .05) increases in seasonal peak-to-trough CO2 amplitude (AMPP-T ) at nine stations, and in trough-to-peak amplitude (AMPT-P ) at eight stations over the last three decades. Most of the stations that recorded increasing amplitudes are in Arctic and boreal regions (>50°N), consistent with previous observations that the amplitude increased faster at Barrow (Arctic) than at Mauna Loa (subtropics). The multi-model ensemble mean (MMEM) shows that the response of ecosystem carbon cycling to rising CO2 concentration (eCO2 ) and climate change are dominant drivers of the increase in AMPP-T and AMPT-P in the high latitudes. At the Barrow station, the observed increase of AMPP-T and AMPT-P over the last 33 years is explained by eCO2 (39% and 42%) almost equally than by climate change (32% and 35%). The increased carbon losses during the months with a net carbon release in response to eCO2 are associated with higher ecosystem respiration due to the increase in carbon storage caused by eCO2 during carbon uptake period. Air-sea CO2 fluxes (10% for AMPP-T and 11% for AMPT-P ) and the impacts of land-use change (marginally significant 3% for AMPP-T and 4% for AMPT-P ) also contributed to the CO2 measured at Barrow, highlighting the role of these factors in regulating seasonal changes in the global carbon cycle.

[1]  E. Buitenhuis,et al.  Potential impact of changes in river nutrient supply on global ocean biogeochemistry , 2007 .

[2]  Charles D. Keeling,et al.  Seasonal amplitude increase in atmospheric CO2 concentration at Mauna Loa, Hawaii, 1959–1982 , 1985 .

[3]  Atul K. Jain,et al.  CO2 emissions from land‐use change affected more by nitrogen cycle, than by the choice of land‐cover data , 2013, Global change biology.

[4]  Heikki Mannila,et al.  Autumn temperature and carbon balance of a boreal Scots pine forest in Southern Finland. , 2010 .

[5]  Stéphane Blain,et al.  An ecosystem model of the global ocean including Fe, Si, P colimitations , 2003 .

[6]  Peter E. Thornton,et al.  Human-induced greening of the northern extratropical land surface , 2016 .

[7]  Marie-Alice Foujols,et al.  Impact of the LMDZ atmospheric grid configuration on the climate and sensitivity of the IPSL-CM5A coupled model , 2013, Climate Dynamics.

[8]  G. Marland,et al.  Monthly, global emissions of carbon dioxide from fossil fuel consumption , 2011 .

[9]  Analysis of CO 2 mole fraction data: first evidence of large-scale changes in CO 2 uptake at high northern latitudes , 2015 .

[10]  Philippe Ciais,et al.  Evidence for a weakening relationship between interannual temperature variability and northern vegetation activity , 2014, Nature Communications.

[11]  E. Buitenhuis,et al.  Biogeochemical fluxes through microzooplankton , 2010 .

[12]  P. Cox,et al.  Projected land photosynthesis constrained by changes in the seasonal cycle of atmospheric CO2 , 2016, Nature.

[13]  Ranga B. Myneni,et al.  Recent trends and drivers of regional sources and sinks of carbon dioxide , 2015 .

[14]  Wouter Peters,et al.  ObsPack: a framework for the preparation, delivery, and attribution of atmospheric greenhouse gas measurements , 2014 .

[15]  K. Macdicken,et al.  Global Forest Resources Assessment 2015: how are the world's forests changing? , 2015 .

[16]  E. A. Kort,et al.  Enhanced Seasonal Exchange of CO2 by Northern Ecosystems Since 1960 , 2013, Science.

[17]  Luis Guanter,et al.  Agricultural Green Revolution as a driver of increasing atmospheric CO2 seasonal amplitude , 2014, Nature.

[18]  E. Stehfest,et al.  Harmonization of land-use scenarios for the period 1500–2100: 600 years of global gridded annual land-use transitions, wood harvest, and resulting secondary lands , 2011 .

[19]  Mark A. Friedl,et al.  Direct human influence on atmospheric CO2 seasonality from increased cropland productivity , 2014, Nature.

[20]  J. Thepaut,et al.  The ERA‐Interim reanalysis: configuration and performance of the data assimilation system , 2011 .

[21]  C. D. Keeling,et al.  Increased activity of northern vegetation inferred from atmospheric CO2 measurements , 1996, Nature.

[22]  Peter E. Thornton,et al.  Assessing future nitrogen deposition and carbon cycle feedback using a multimodel approach: Analysis of nitrogen deposition , 2005 .

[23]  Tsutomu Ikeda,et al.  Biogeochemical fluxes through mesozooplankton , 2006 .

[24]  R. B. Jackson,et al.  A Large and Persistent Carbon Sink in the World’s Forests , 2011, Science.

[25]  Corinne Le Quéré,et al.  Carbon emissions from land use and land-cover change , 2012 .

[26]  P. Cox,et al.  The Joint UK Land Environment Simulator (JULES), model description – Part 2: Carbon fluxes and vegetation dynamics , 2011 .

[27]  Philippe Ciais,et al.  Declining global warming effects on the phenology of spring leaf unfolding , 2015, Nature.

[28]  Bala Rajaratnam,et al.  Contribution of changes in atmospheric circulation patterns to extreme temperature trends , 2015, Nature.

[29]  P. Tans,et al.  Atmospheric carbon dioxide at Mauna Loa Observatory: 2. Analysis of the NOAA GMCC data, 1974–1985 , 1989 .

[30]  R. Reynolds,et al.  The NCEP/NCAR 40-Year Reanalysis Project , 1996, Renewable Energy.

[31]  Atul K. Jain,et al.  Increased light‐use efficiency in northern terrestrial ecosystems indicated by CO2 and greening observations , 2016 .

[32]  Christopher B. Field,et al.  The contribution of terrestrial sources and sinks to trends in the seasonal cycle of atmospheric carbon dioxide , 1997 .

[33]  P. Ciais,et al.  Net carbon dioxide losses of northern ecosystems in response to autumn warming , 2008, Nature.

[34]  Robert B. Cook,et al.  The North American Carbon Program Multi-scale Synthesis and Terrestrial Model Intercomparison Project – Part 2: Environmental driver data , 2013 .

[35]  Karl E. Taylor,et al.  An overview of CMIP5 and the experiment design , 2012 .

[36]  F. Joos,et al.  Multiple greenhouse-gas feedbacks from the land biosphere under future climate change scenarios , 2013 .

[37]  S. Carpenter,et al.  Global Consequences of Land Use , 2005, Science.

[38]  C. D. Keeling,et al.  Modelling the seasonal contribution of a CO2 fertilization effect of the terrestrial vegetation to the amplitude increase in atmospheric CO2 at Mauna Loa Observatory , 1989 .

[39]  Peter E. Thornton,et al.  Global Latitudinal-Asymmetric Vegetation Growth Trends and Their Driving Mechanisms: 1982-2009 , 2013, Remote. Sens..

[40]  R. Naiman,et al.  Freshwater biodiversity: importance, threats, status and conservation challenges , 2006, Biological reviews of the Cambridge Philosophical Society.

[41]  E. Barnes,et al.  Isentropic transport and the seasonal cycle amplitude of CO2 , 2016 .

[42]  Ranga B. Myneni,et al.  Weakening temperature control on the interannual variations of spring carbon uptake across northern lands , 2017 .

[43]  W. Post,et al.  The North American Carbon Program Multi-Scale Synthesis and Terrestrial Model Intercomparison Project – Part 1: Overview and experimental design , 2013 .

[44]  Nuno Carvalhais,et al.  Enhanced seasonal CO2 exchange caused by amplified plant productivity in northern ecosystems , 2016, Science.

[45]  J. Randerson,et al.  Technical Description of version 4.0 of the Community Land Model (CLM) , 2010 .

[46]  J. Galloway,et al.  Transformation of the Nitrogen Cycle: Recent Trends, Questions, and Potential Solutions , 2008, Science.