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Carbon and Water Impacts of the Turn of the Century Drought in Western North America 2000-2004 1 Clark University, Graduate School of Geography 2 Northern.

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Presentation on theme: "Carbon and Water Impacts of the Turn of the Century Drought in Western North America 2000-2004 1 Clark University, Graduate School of Geography 2 Northern."— Presentation transcript:

1 Carbon and Water Impacts of the Turn of the Century Drought in Western North America Clark University, Graduate School of Geography 2 Northern Arizona University 3 National Snow & Ice Data Center Christopher Schwalm 1,2 Christopher A. Williams 1, Kevin Schaefer 3 Dennis Baldocchi, Andy Black, Allen Goldstein, Bev Law, Walt Oechel, Kyaw Tha Paw U, Russ Scott, Bardan Ghimire NACP AIM4 Albuquerque, NM February 2013

2 Data Sources: Zhao & Running, 2010 Mitchell & Jones, 2005 Willmott et al., 1985 Palmer Drought Severity Index Precipitation CRU TS 3.0 Soil Moisture UDel [mm month -1 ] [mm] Turn of the Century Drought in the US West

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8 Palmer Hydrological Index (Long-term Drought)

9 PDSI Lower than During the European Heat Wave

10 Evapotranspiration Evaporative Fraction from MERRA Air Temperature UDel Normalized Diff Veg Index Data Sources: Bosilovich et al., 2008 Tucker et al., 2005 Zhang et al., 2009,2010 Willmott & Robeson, 1995 Departures from June-September, Area-Wide Averages [mm month -1 ] [°C] Clear Reductions in Evaporation and Vegetation Index

11 Drought – Non-Drought = {’00-’04} – {’97-’99, ’05-’07} Response Was Coherent Across the Western Region

12 USGS Hydrologic Units Pacific Northwest California Upper CO Great Basin Lower CO Rio Grande River Flows Showed Large Reductions from Average

13 United States Geological Survey WaterWatch Major Decrease in River Discharge Across Western Basins TCD

14 BasinNumberlate 80searly 30s50s-60s Upper Colorado 0 Lower Colorado 0 Great Basin 6 yes Pacific Northwest 9 yes California 10 yes Rio Grande 1 BasinNumber Upper Colorado 0 Lower Colorado 0 Great Basin 6 Pacific Northwest 9 California 10 Rio Grande 1 Number of years in the Century-long record with a 5-year average runoff lower than during the TCD Basins that experienced low flows during other major droughts (yes)

15 National Agricultural Statistics Service (Data Source: Lobell et al., 2002) Western Crop Yield Decreased 10% Relative to 11-yr Average non-drought drought

16 Western Crop Yield Decreased 10% Relative to 11-yr Average

17 Agriculture $50 billion annually in net farm income Meaningful contributions from the West Market Value of Agricultural Products Sold: 2007 USDA Agriculture Projections to 2020, OCE USDA National Agricultural Statistics Service

18 North American Carbon Project (NACP) Site Synthesis & Ameriflux Eddy Flux Network Used as Observatory

19 Baseline: Sizeable Carbon Uptake, and Large Bowen Ratio Productivity: Forests >> Grasslands & Savannas Evaporation: Grasslands > Forests & Savannas

20 Anomaly = Drought – Baseline Mean Reduced Carbon Uptake and Evaporation, Increased Heating Carbon uptake decreased by 37% and 160% in forests and grasslands increased in woody savannas… respiration slowed more than productivity Evaporation decreased by 25%, 5%, and 16% for ENF, GRA, and WSA temperatures increased by ~0.4 °C

21 *Anomaly = Drought Mean – Baseline Mean Reduction in Carbon Uptake Offset 45% of Normal Sink Term [Tg C y -1 ] SourceDrought Anomaly* Baseline Flux Percent Reduction GPPMODIS % GPPUpscaled FLUXNET % NEPInversions % 44% NEPFlux Tower Network %

22 Direct Fire Emissions in the Western U.S. (only those > 400 ha in size) [Tg C y -1 ] Ghimire, Williams, Collatz (2012) Average Total TCD ~25 Tg C y-1 released from fires

23 Year PDSI reconstructed from dendrochronologies for western North America (Based on Cook et al., 1999, 2004) Historical Context: Most Severe 5-Yr Drought in 800 Years

24 World Climate Research Programme's Coupled Model Intercomparison Project 5 (CMIP5) multi-model dataset of summer precipitation values were based on the historical model experiment. 21 st Century runs were forced by a business as usual high emissions scenario (Representative Concentration Pathway, RCP8.5) (Data Source: Meehl et al., 2007) Projections Suggest It Could Become The New Normal TCD June – August Only

25 Annual Mean P - E Seager et al. Science 2007 Statistics from 19 Model Runs (CMIP3) with A1B forcing for the American Southwest Relative to a Baseline , 6-year filter Pink Shading Shows Multi-Model Spread in Annual P – E Paper “Model Projections of an Imminent Transition to a More Arid Climate in Southwestern North America Similar to Previous IPCC AR4 Model Runs

26 Greenhouse Gases Accumulate with Compounding Effects Natural Variability Is Real and Remains, But… Transition to a Drier Climate Normal

27 The turn of the century drought was a major 5-year anomaly, one of the largest in the past millennium Cause large reduction in water availability seen in multiple lines of evidence Substantially reduced the region’s carbon uptake and crop productivity Forecasts suggest it is likely to become the wet end of a drier 21 st Century because of human GHG-forcing Conclusions

28 NEP vs. PPT for Individual Flux Tower Sites Red = TCD; Blue = Reference Years Thick Black Line = Across-Site Mean Relationship

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30 Statistical Distributions Agree for PDSI and CMIP5 Precipitation

31 Statistical Distributions Agree for CMIP5 Precipitation and Observed Precipitation

32 Drought Area Index, 1931 to 2003 from Weather Instruments (blue) and Tree Rings (red) (Cook et al., 1999, 2004) Good Agreement between Annual Fluctuations in PDSI and Precipitation


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