Modeling CO2 and CH4 Emissions in the Arctic

Transcription

1 Modeling CO2 and CH4 Emissions in the Arctic Qianlai Zhuang Departments of Earth & Atmospheric Sciences and Agronomy

2 Serreze et al., 2000, Climatic Change

3 Ecosystems in Northern High Latitudes Large vulnerable carbon pool (~1/3 of world soil C) Large wetland distribution (~1/2 of world wetlands) Longer growing season (1-4 days /decade) Changing vegetation (e.g., moving treeline)

4 Large-scale processes in the region Permafrost thawing (~1/4 of areas underlain by permafrost) Fire disturbance increase (~1% yr -1 )

5 Questions What is the current budget of CO 2 and CH 4 for the region? How will the budget change over the 21 st century? What is the impact of the budget change on climate in the 21 st century?

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7 Soil Thermal Module Upper Boundary Conditions Prescribed Temperature Snow Cover Moss&litter Soil Snow Depth Moss Depth Organic Soil Depth Mineral Soil Depth Prescribed Temperature Frozen Ground Organic Soil Thawed Ground Mineral Soil Frozen Ground Heat Conduction Moving phase plane Moving phase plane Temperatures at Different Depths Lower Boundary Conditions (Zhuang et al., 2001JGR)

8 Soil Temperatures of an Old Black Spruce Ecosystem in Canada

9 Carbon Fluxes of an Old Black Spruce Ecosystem in Canada 250 Tower estimates STM-TEM GPP (g C m -2 ) RESP (g C m -2 ) Jan May Sep Jan M ay Sep Jan May Sep Jan M ay Sep

10 Alaskan and Canadian Large Fire Database from 1950 to 1999 Figure 4. Location and area of historical fires in Alaska ( ) and Canada ( ).

11 The Modified Terrestrial Ecosystem Model NCE CO 2 Concentration NPP R H Fire Emissions Climate (Temperature, Precipitation) Fire regime (Severity, History) TEM Carbon Pools (Zhuang et al., 2002JGR)

12 Fire Emissions 1) Follow French et al. (2003, 2004), the total carbon emissions during fire is modeled: T C = B A( Caβ a + Cg g β ) 2) Gas species emissions are modeled: E i = BA[ Ca β a ( f af E fi + f as Esi ) + C g β g ( f gf E fi + f gs Esi )]

13 Regrowth after Fire (Zhuang et al., 2002JGR)

14 Fire Carbon Emissions from 1959 to 1999 in Canada

15 Comparison of Observed and Simulated CO 2 at Monitoring Stations (Zhuang et al., 2003)

16 Current Net CO 2 Exchanges Carbon sources at 277 Tg C year (g CO 2 -eq. m -2 year -1 ) (Zhuang et al., 2003)

17 Progress Summary The region currently is a source at about 277 Tg C yr -1 due to fire emissions and the enhanced soil respiration after fire

18 Updated Hydrological Module Rainfall Snowfall Evaporation Sublimation Canopy Transpiration Evaporation Rain throughfall Snow throughfall Sublimation Infiltration Non-Wetland Soil & Root Drainage Runoff S L1 S L2... S L n Wetland Layer 1 Layer 2 Water Table (Z W ) Drainage (Zhuang et al., 2002JGR)

19 Model Framework Hydrological Module (HM) Soil Thermal Module (STM) Terrestrial Ecosystem Model (TEM) Water Table and Soil Moisture Profile Soil Temperature Profile Active Layer Depth Labile carbon Vegetation Characteristics Methane Consumption and Emission Module (MCEM) (Zhuang et al., 2004GBC)

20 Methane Consumption and Emission Module Atmospheric CH 4 Concentration (A M ) (Oxic Soil) Diffusion (D SA ) Plant- Mediated Emission (P M ) Ebullition (E B ) Soil / Water Surface Upper Boundary (Anoxic Soil) CH 4 Consumption (M C ) CH 4 Production (M P ) Water Table Lower Boundary (Zhuang et al., 2004 GBC)

21 Methane Fluxes at a Fen Site in Canada (Zhuang et al., 2004 GBC)

22 Methane Fluxes of a Wet Tundra Ecosystem in Alaska (Zhuang et al., 2004GBC)

23 Net Methane Fluxes in the 1990s Emissions = 56 Tg CH 4 yr -1 Consumption = -7 Tg CH 4 yr -1 Net Methane Fluxes = 49 Tg CH 4 yr -1 (Zhuang et al., 2004GBC)

24 Progress Summary Wetlands represent hotspots of CH 4 emissions Large areas of upland ecosystems in the region consume CH 4 The region currently acts as a source of 49 Tg CH 4 yr -1

25 Current GHG Budget of CO 2 and CH 4

26 Calculation of GHG Budget 1. Convert net methane fluxes (NMF) into global warming potentials (CO 2 -equivalent) on 100-year time horizon: GWP CH4 = NMF Convert net carbon dioxide fluxes (NCE) from C into CO 2 units: NCE'=NCE 44/12 3. Obtain greenhouse gas budget: Greenhouse gas budget = GWP CH4 + NCE'

27 Greenhouse Gas Budget in the 1990s GHG source = 2.1 Pg CO 2 -eq. yr -1 (g CO 2 -eq. m -2 yr -1 )

28 Progress Summary GHG budget is source of 2.1 Pg CO 2 -eq.yr -1 with considering fire disturbances in the 1990s (due to fire effects and methane emissions)

29 Future GHG Budget of CO 2 and CH 4

30 Factors and Processes Considered to Project Future GHG Budget Three plausible climate and atmospheric CO 2 concentration scenarios With and without CO 2 fertilization effects Three future fire disturbance scenarios Three plausible vegetation redistributions

31 MIT Integrated Global System Model (IGSM)

32 Three Climate and Atmospheric CO 2 Concentration Scenarios

33 Projection of Future Fire Burned Areas 1) Increase at rate of 0.5% yr -1 from the present to year ) Increase at rate of 1% yr -1 from the present to year 2100 (Based on last 50 year data) 3) Increase at rate of 1.5% yr -1 from the current to year 2100

34 Changes in CO 2 and CH 4 concentrations and global radiative forcing over the 21 st century associated with climate-related biogeochemical changes in the high northern latitudes CO 2 fertilization effect No CO 2 fertilization effect Anthropogenic Emissions Δ[CH 4 ] (ppm) Δ[CO 2 ] (ppm) ΔF (W/m 2 ) Δ[CH 4 ] (ppm) Δ[CO 2 ] (ppm) ΔF (W/m 2 ) High Intermediate Low (Zhuang et al., 2006 GRL)

35 Progress Summary CO 2 fertilization effects present a huge uncertainty Fire disturbances exert significant impacts on the regional sink and source activities Vegetation redistributions have minimum effects on the GHG budget during the 21 st century

36 Seasonal Changes of Inundation Areas in Canada and Alaska Week 4 of year 2000 snow (%) (Mialon et al., 2006)

37 Seasonal Changes of Inundation Areas in Canada and Alaska Week 20 of year 2000 snow (%)

38 Seasonal Changes of Inundation Areas in Canada and Alaska Week 36 of year 2000 snow (%)

39 Seasonal Changes of Inundation Areas in Canada and Alaska Week 48 of year 2000 snow (%)

40 Shrinkage of Open Water within the Yukon Flats National Wildlife Refuge (Riordan et al., 2006)

41 Changes in hydrology, soils, and vegetation with varying modes of permafrost degradation

42 Carbon in kg C/m 2 Carbon in kg C/m 2 Tussock tundra Shrub tundra Woodland Forest Postburn forest Moat #1 Moat #2 Bog Total C stock above + belowground Total C stock above + belowground C stock aboveground C stock aboveground Post-1963 soil C enriched by 14 C Post-1963 soil C enriched by 14 C or 137 Cs Pre-1963 soil C stock Pre-1963 soil C stock First tree establishment No trees 1970s 1880s 1770s Establishment of bog ~1700 ybp Permafrost depth ~30 cm gravel 40 cm Not found Discont. Permafrost depth ~70 cm ~60 cm >200 cm A. Draining of Thaw-Water is inferred from a spatial gradient of tundra-woodland-shrubland-forest at treeline along the Kapuruk River, AK. A loss of 7.6 kgc/m 2 is inferred from tundra vs forest comparison. 6.3 kgc/m 2 was lost from shallow soil since 1952 based on stocks labeled with radiocarbon enriched by weapons testing after 1952; the remaining 1.3 was lost from deeper soil pools. Meanwhile 0.7 kgc/m 2 was assimilated into forests wood. Modified from Wilmking et al., in press, to reflect soil C stocks only for soil profiles with radiocarbon data. B. Ponding of Thaw-Water formed a collapse bog in Tanana Flats, AK. Recent burning and chronologic and macrofossil data indicate that burns likely triggered several collapses since ~500 years ago. C stocks in the thawinduced bog resulted in a net increase of 5 kgc/m 2 based on replicate cores. C stocks associated with 137 Cs and 210 Pb dating indicate ~1 to 1.5 kg of accumulation occurred since 1963 when tree rings and diatoms indicate a shift in environment. Methane emissions were slightly elevated at the moat relative to the bog and forest sites. From Meyers-Smith et al, in press.

43 Coupled modeling systems of a new version of TEM and a spatially-explicit permafrost model Terrain Types and Permafrost Degradation Modes Moss and Litter Thickness TEM (CO 2, CH 4, DIC, DOC, DON) Soil Temperature Active Layer Depth Soil Moisture Runoff Drainage Water Table Evapo-transpiration Leaf Area Index Ecotype (vegetation/soil) map & table Vegetation Structure and Successional Stage Regional Snow Depth Snow Depth (site) Permafrost Model Digital Elevation Model (map) Equivalent Latitude Regional Air Temperature Air Temperatures (site) Thawing n-factors Freezing n-factors Soil Thermal Module (STM) Active Layer Depth Snow Thickness Soil Moisture Hydrological Module (HM) Soil Stratigraphy Surface Soil Temperatures Soil Thermal Properties (conductivity ratio) Deep Soil Temperatures (base of active layer)

44 (Walter et al., 2007, Phil. Trans. Royal Soc. A)

45 Sergey Zimov, director of the Northeast Science Station in Siberia, examining a cross-section of yedoma, carbon trapped in permafrost, along the bank of the Kolyma River in Siberia. The shiney surface of the cliff represents massive ice wedges. The dark sections in between are soil inclusions which contain ice-age organic carbon, left over from the Pleistocene steppe-tundra ecosystem. Organic carbon when deposited into lake bottoms provides food for bacteria that produce methane. Some scientists believe that as this organic matter becomes exposed to the air it will accelerate global warming faster than even predicted in the most pessimistic forecasts. Photo: Nature, Katey Walter

46 Next Efforts New data of land cover and land use change New field data of carbon, water and energy New understanding of processes and mechanisms Integration and synthesis Feedbacks with the climate system

47 Acknowledgement NASA LCLUC program NSF Arctic Sciences Program NSF Biocomplexity Program carbon and water National Center of Ecological Analysis and Synthesis (NCEAS) Collaborators, mentors, and group members at Purdue: Jerry Melillo, Dave McGuire, Terry Chapin, Ron Prinn, Jen Harden, Rob Striegl, Torre Jorgenson, Yuri Shur,Valodia Romanavosky, and many others