An Integrated View of North American Biosphere Carbon Flux Inter-annual Variability: from satellite CO2 to phenology Junjie Liu1, Kevin Bowman1, Dave Schimel1, Nick Parazoo1, Anthony Bloom1, Meemong Lee1, Kevin Gurney2, Dimitris Menemenlis1 Jet Propulsion Lab, California Institute of Technology Arizona State University A-train Symposium April, 2017 How A-train observatioins can help us understand the carbon cycle, here we focus on north American biospere

Global carbon cycle Fossil fuel photosynthesis Atmospheric buildup http://www.bigskyco2.org/ Global carbon cycle has four major components: one is fossil fuel emissions of CO2, it has been steadily increasing. In recent years, the emissions are around 10GtC/year. Another is the atmospheric carbon buildup, which is the amount of Fossil fuel emssions remained in the atmosphere, shown by the blue bar. ON areverage, about 50% fossil fuel emissions reamined in the atmosphere. The remaining fossil fuel has been absorbed by the either land through biosphere or ocean. About 50% of fossil fuel emissions remained in the atmosphere The land and ocean sink have large interannual variability The net biosphere sink is the difference between gross primary production (GPP) and respiration

Focus of this study: North American Temperate Fossil fuel (FF) 2011 2012 Atmospheric buildup ? FF over North American Temperate FF over the region is about 20% of the global FF WE focus on North American temperate, which includes continental US, part of Canada and Mexico. Over this region, the FF emission is about 20% of global fossil fuel emissions. Over this region, there were two major droiught events, 2011 over texas mesix and 2013 How much of this FF has been absorbed by biosphere over the region? What is the interannual variability of this net biosphere flux? What is the impact of drought events on net biosphere fluxes and carbon exchange processes?

Previous studies… -929±477 -890±400 -890±409 Unit: TgC/year In-situ King et al., 2015 North American biosphere flux from in-situ based flux inversion has about 50% uncertainty; Many studies have tried to answer these questions. One of the methods is atmospheric inversion that infer surface fluxes based on atmospheric CO2 concentration observations. Using in-situ observatioins, which are about 100 around the globe, the inferred biosphere flux over North American has bout 50% uncertiaty in spite of relatively dense observations over the region.

Carbon Cycle Data Assimilation net biosphere exchange Methodology A-train OCO-2 Japanese GOSAT 2010 2011 2012 2013 2014 2015 Column CO2 Carbon Cycle Data Assimilation (CMS-Flux) In this study, we assimilated column CO2 observations from Ja carbon to constrain global net bisophere exchange over the globe net biosphere exchange

Methodology MODIS Column CO2 Carbon Cycle Data Assimilation (CMS-Flux) EVI A-train OCO-2 Japanese GOSAT 2010 2011 2012 2013 2014 2015 Solar Induced Chlorophyll fluorescence (SIF) Column CO2 Carbon Cycle Data Assimilation (CMS-Flux) To further understand the processes controlling biosphere exhange, we quantified GPP with SIF observations. MODIS, which is also on A-train, provide important phenology observations. net biosphere exchange Gross Primary Production (GPP)

Net biosphere carbon flux constrained by satellite CO2 observations North American Temperate GtC/year Replot with magenta Mean net biosphere sink is 1.2 ± 0.2 GtC with 0.2 GtC interannual variability

Biosphere, fossil fuel, and atmospheric buildup North American Temperate GtC/year In this chart, year 2011 has weaker sink than the mean value, and much larger atmospheric build up. ? 2010 2015 Mean (2010-2015) fossil fuel emission is 1.8 GtC; mean atmospheric build up is 0.6 GtC Mean FF air borne fraction is 33% (ranging from 17% to 54%)

2011 and 2012 drought impact on biosphere carbon fluxes

2011 and 2012 precipitation anomaly 2011 precip anomaly 2012 precip anomaly Texas-Mexico

2011 drought impact Replot the margin

2011 drought impact Precip mm/day

2011 drought impact Precip SIF-GPP mm/day MODIS-EVI

2011 drought impact Fossil fuel Δ GPP (2011-2015) Δ NBE (2011-2015) Relative to 2015, the 2011 Texas-Mexican drought reduced biosphere sink by 0.3±0.1 GtC, which is comparable to regional FF.

2012 drought Replot the margin

2012 drought impact Precip mm/day Lowest precipitation over the region

Net Biosphere Exchange 2012 drought impact Precip SIF-GPP mm/day MODIS-EVI Net biosphere uptake is the lowest. While the annual GPP and EVI anomaly is not significant. Why SIF-GG and MODIS EVI is not significant? GtC/year Net Biosphere Exchange Lowes precipitation and smallest biosphere C sink in 2012; Annual GPP and EVI anomaly are not significant

2012 drought impact on seasonality 2010 2012 2015 EVI SIF-GPP Precip anomaly 2010 2012 2015 Why is not significant? We examined the seasonality of precipitation and temperate anoamaly 2012 black and blue are 2010 and 2015 respectively. At the begiinig of the year, it is featured with higher preciptation T anomaly Warmer and wetter at the beginning of the year=> higher EVI and GPP at the beginning Drought peaked in June and July

Impact of 2012 drought impact Fossil fuel Δ GPP (2011-2015) Δ NBE (2011-2015) The net biosphere sink was reduced by 0.22±0.17 GtC which is 24% of regional FF emissions.

Impact of 2011 and 2012 drought Fossil fuel Δ GPP (2011-2015) Δ NBE (2011-2015) Both drought increased the FF air borne fraction; 2011 drought increased local FF air borne fraction by 100%, while 2012 drought increased local FF air borne fraction by 24% 2011 drought had larger impact on net biosphere carbon fluxes than 2012 drought

Conclusions Synergistic use of A-train observations is critical to quantify and understand biosphere carbon flux interannual variability . Mean FF air borne fraction over North American Temperate is 33%; with variability ranging from 17% to 54% Drought events have large impact on regional FF air borne fraction.

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Net biosphere exchange Fossil fuel Airborne Carbon Bar is the standard deviation plus inter annual variability.

Precipitation anomaly Seasonality Net biome exchange 2010 2011 2015 Precipitation anomaly EVI Replot the seasonality between 2010 and 2011 T anomaly SIF-GPP

Net flux difference between 2011 and 2010 Black: FLUXCOM Green: top-down

Net biosphere flux difference between 2012 and 2010 Black: FLUXCOM Red: top-down While for the net biosphere fluxes Increased uptake in April and reduced uptake in July, which are consistent with fluxnet upscaled FLUXCOM product

Methodology MODIS Column CO2 Carbon Cycle Data Assimilation (CMS-Flux) A--Train A-train OCO-2 Japanese GOSAT 2010 2011 2012 2013 2014 2015 500 MODIS EVI Solar Induced Chlorophyll fluorescence (SIF) Column CO2 Carbon Cycle Data Assimilation (CMS-Flux) Upscaled FLUXNET fluxes FLUXCOM net biosphere exchange Gross Primary Production (GPP) Independent Evaluation