ENSO,ENSO, DroughtDrought andand thethe ChangingChanging CarbonCarbon CycleCycle

NingNing ZengZeng

Dept.Dept. AtmosphericAtmospheric andand OceanicOceanic ScienceScience andand EarthEarth SystemSystem ScienceScience InterdisciplinaryInterdisciplinary CenterCenter UniversityUniversity ofof MarylandMaryland

Contributors: M. Heimann, A. Mariotti, C. Roedenbeck, P Wetzel, E. Maier-Reimer H. Qian, R. Iacono, E. Munoz CO2 ∆CO2 from climate feedback Enhanced global warming from carbon-climate interaction: Land uptake ∆ Land uptake the C4MIP results --- UMD Earth System Model (CABO)

Large differences in land response: Ocean uptake ∆ Ocean uptake interannual variability as a testbed

Friedlingstein et al., J. Climate in press AtmosphericAtmospheric CO2CO2 VariabilityVariability 19581958--20002000

Lagged Correlations Corr = 0.6

5 months lag dCO2/SOI

--- dCO2/dt Emission

-SOI 3-6 months lag Hydrology/SOI th 20 Century Observed Forcing Physical Climate Coupled Carbon Model

Transport Atmosphere Reanalysis Atmospheric CO2

Precipitation Precip, Temp Temperature Carbon Radiation (CRU, CMAP, GISS) Exchange wind,vapor Soil Moisture/temperature Vegetation+ Land Soil Carbon

Circulation Temperature Salinity Ocean Physics Ocean Chemistry/Biology Reanalysis

Goal: To understand the changing carbon cycle in the 20th Century The VEgetation-Global Atmosphere-Soil Model (VEGAS)

Atmospheric CO2 4 Plant Functional Types: Broadleaf tree Photosynthesis Autotrophic Needleleaf tree respiration C3 Grass (cold) C4 Grass (warm) NPP 3 Vegetation carbon pools: Carbon Leaf allocation Heterotrophic Root respiration (Rh) Wood Turnover 3 Soil carbon pools: Fast Intermediate Slow VEGASVEGAS IIII Photosynthesis:Photosynthesis: LightLight (PAR,(PAR, LAI,LAI, Height),Height), soilsoil moisture,moisture, temperature,temperature, CO2CO2 Respiration:Respiration: Temperature,Temperature, soilsoil moisture,moisture, lowerlower soilsoil poolspools slowerslower decaydecay Competition:Competition: NetNet growth,growth, shadingshading =>=> fractionalfractional covercover Fire:Fire: moisture,moisture, fuelfuel load,load, PFTPFT dependentdependent resistanceresistance Wetland/CH4:Wetland/CH4: moisture,moisture, topographytopography gradientgradient MechanismsMechanisms ofof InterannualInterannual VariabilityVariability II

Modeled land-atmo flux vs. MLO CO2 growth rate

Terrestrial carbon model forced by observed climate variability LandLand vs.vs. oceanocean fluxesfluxes

Land: VEGAS Land contributes to most of the interannual variability, Ocean: HAMOCC with significant contribution from ocean Modeling results supported by in-situ data and inversion El Nino 97/98

VEGAS

Inversion Roedenbeck 2003 Spatial patterns from PC1 PC2 multi-variate EOF analysis

1901 1995 C flux Tropics during El Nino

1) Drier and warmer conditions coexist at tropical locations

Precip 1+) Drier and warmer across much of tropical land during El Nino

2) Less precip => Less growth (lower NPP) Temp and more fire => Less C uptake

Higher T => more respiration (higher Rh) => more C release Why CO2 correlates so well with ENSO: A ‘conspiracy’ theory Tropics during El Nino

Precipitation Temperature decrease increase

Out of phase NPP decrease Rh increase

Additive

Land-atmo flux (Rh-NPP) increase + Spatially coherent climate anomalies

Large land-atmo C flux Fire carbon flux during 1997-98 El Nino

CASA VEGAS

Mean

1997-98 El Nino Anomalies

Input: climate only Input: satellite fire counts, climate

RecentRecent AnomalousAnomalous growthgrowth inin CO2CO2

1980 2003

Proposed explanations: 1. Fire in Siberia, North America, and other places 2. Accelerated carbon emission from China, India 3. Mid-latitude drought MidMid--latitudelatitude Drought:Drought: 19981998--20022002

RecentRecent AnomalousAnomalous growthgrowth inin CO2CO2 DryingDrying oror Warming?Warming? FireFire inin thethe US:US: NaturalNatural vsvs anthropogenicanthropogenic factorsfactors

Model

Observation WhatWhat happenedhappened inin AustraliaAustralia 19981998--20022002 ??

l

Observation ConclusionsConclusions

‹ Drought is the major source of CO2 variability, whether it’s tropical (ENSO) or midlatitude.

‹ The high correlation between CO2 and ENSO is mainly due to a ‘conspiracy’ between climate anomalies and plant/soil physiology.

– This conspiracy makes it difficult to narrow down the relative roles of NPP, Rh, and fire based on observations alone, yet models do not agree.

‹ Recent anomalously large CO2 growth can be explained by a (so far) unusual midlatitude drought, a possible glimpse into a warmer world

‹ Understanding the mechanisms and processes underlying such interactions provides crucial insight into the fate of anthropogenic CO2 and the degree of future climate change