Process contribuhons of Australian ecosystems to interannual variahons in the carbon cycle

Transcription

1 Process contribuhons of Australian ecosystems to interannual variahons in the carbon cycle CSIRO OCEANS AND ATMOSPHERE Vanessa Haverd, Cathy Trudinger, Ben Smith, Lars Nieradzik, Peter Briggs, Pep Canadell

2 Ahlström, A. et al. The dominant role of semi- arid ecosystems in the trend and variability of the land CO2 sink. Science 348, (2015)

3 Poulter, B. et al. ContribuHon of semi- arid ecosystems to interannual variability of the global carbon cycle. Nature 509, (2014) Record global carbon uptake anomaly in 2011 Australian ecosystems: contributed 57% of 2011 anomaly of 1.5 ± 0.9 [1σ] Pg C have entered a regime of enhanced sensijvity to rainfall since the mid- 1990s. Lag between producjon and decomposijon amplifies interannual variability of net carbon uptake. fourfold increase in net carbon uptake sensijvity to precipitajon (comparing ; )

4 Piao, S. et al. EvaluaHon of terrestrial carbon cycle models for their response to climate variability and to CO2 trends. Global Change Biology 19, (2013). SensiJvity of Global Net Biome ProducJvity to Precip

5 ObjecHves QuanJfy interannual variability (IAV) of Australian Net Ecosystem ProducJon and magnitude of 2011 anomaly A\ribute IAV spajally and by process QuanJfy sensijvity of Australian Net Ecosystem ProducJon to precipitajon anomalies Demonstrate transfer of vegetajon drought response from Australian to global context.

6 DATA (for forcing) Precip, radiajon, temperature Soil, vegetajon (RS FPAR) All at 0.05 o (~ 5km) res MODEL CABLE Non- standard C- cycle soil- moisture responses SLI hydrology Reduced PFTs Prior PDF PRIOR INFORMATION Parameter esjmates (literature) DATA (for assimilahon) Eddy flux data (ET, R eco, GPP) Streamflow Li\erfall Carbon pools (soil, li\er and vegetajon) MODEL- DATA FUSION Cost funcjon Search strategy ( (down- gradient search ) Refine target variables Posterior PDF updated parameter PDF Haverd, V. et al. MulJple observajon types reduce uncertainty in Australia's terrestrial carbon and water cycles. Biogeosciences 10, , (2013). PRODUCTS Water and carbon fluxes and stores (with uncertainjes) Maps, monthly Jme series TESTING Independent data

7 Haverd, V. et al. MulJple observajon types reduce uncertainty in Australia's terrestrial carbon and water cycles. Biogeosciences 10, , (2013).

8 MulHple observahon types reduce uncertainty in Australian conhnental NPP Haverd, V. et al. MulJple observajon types reduce uncertainty in Australia's terrestrial carbon and water cycles. Biogeosciences 10, , (2013).

9 Interannual variability in Australia s terrestrial carbon cycle constrained by mulhple observahon types Trudinger et al., Biogeosciences Discuss., doi: / bg , 2016

10 Interannual variability in Australia s terrestrial carbon cycle constrained by mulhple observahon types Trudinger et al., Biogeosciences Discuss., doi: / bg , 2016

11 Model- obs comparison: monthly and annual fluxes at 14 sites Trudinger et al., Biogeosciences Discuss., doi: / bg , 2016

12 Interannual variability in Australian vegetahon produchvity and net carbon uptake (i) Haverd et al., Env. Res. Le\., 11, , 2016 (ii) Terrestrial ecosystems in Australia absorbed 0.6±0.2 [2σ] Pg C in 2011 or 40% of the record global residual land sink anomaly Gross Fire Emissions Anomaly (GFED4)

13 QuanHfying the contribuhon of parhal Hme series anomaly to total Hme series anomaly parjal Jme series Ahlström, A. et al. Science 348, (2015) contribujon total Jme series contributions sum to one +ve contributions reflect correlation with total time series -ve contributions reflect negative correlation with total time series

14 Regional ContribuHons to Interannual Variability of C- fluxes dominated by semi- arid ecosystems: Savanna and Sparsely Vegetated (i) (ii) [mm y - 1 ] (iii) Tropics Warm Temperate Savanna Cool Temperate Mediterranean Sparsely Vegetated Net Primary ProducJon (iv) Heterotrophic RespiraJon (v) (vi) Net Ecosystem ProducJon IAV [g m - 2 y - 1 ] Haverd et al., Env. Res. Le\., 11, , 2016 (vii) (viii) (ix) ContribuJon to conjnental IAV [% (10 4 km 2 ) - 1 ]

15 Extremeness of 2011 C- fluxes highest in Semi- Arid Regions (i) (v) Net Primary ProducJon (ii) z- score of 2011 flux (vi) 2011 flux anomaly [g C m - 2 y - 1 ] Heterotrophic RespiraJon (iii) (vii) Net Ecosystem ProducJon (iv) (viii) Haverd et al., Env. Res. Le\., 11, , 2016

16 Variability in decomposihon offsets variability in produchon at conhnental scale (i) Haverd et al., Env. Res. Le\., 11, , 2016 (ii) NPP (iii) R H Process ContribuJon to IAV in local NEP

17 Dryland vegetahon response to wet episode, not inherent shif in sensihvity to rainfall, behind Australia's role in 2011 global carbon sink anomaly : (1.7±0.1) 10 2 PgC mm - 1 month : (1.5±0.4) 10-2 PgC mm - 1 month Haverd et al., Global Change Biology, doi: /gcb

18 Transfer of drought response and soil evaporajon from Australian regional modelling improve CABLE ET predicjons at global Fluxnet sites Haverd et al, Geosci. Model Dev. Discuss., 2016, 1-24, 2016.

19 Transfer of drought response from Australian regional modelling helps to give good predichons of IAV in global terrestrial carbon uptake.

20 Summary SpaJally, IAV contribujons dominated by Eastern savannas By process, IAV contribujons dominated by NPP, significantly offset by Rh, and negligibly influenced by fire anomaly in Australian NEP (40% of record global sink) wide- spread across northern third of the conjnent. No evidence of inherent ship in the sensijvity of vegetajon acjvity to moisture availability. Transfer of drought response from Australian regional modelling helps to give good predicjons of IAV in global terrestrial carbon uptake.

21 Seasonal Drought: Northern Australian Tropical Transect

22 Alternate drought response and SLI hydrology improve CABLE ET predichons at global Fluxnet sites: examples

23 Model- obs comparison: monthly fluxes Trudinger et al., Biogeosciences Discuss., doi: / bg , 2016