Accounting for terrestrial ecosystem feedbacksin a regional climate model

Baltex 2008: Utility of Regional Climate Models

Ben Smith

Geobiosphere Science Centre,Lund University, Sweden

Credits:

Patrick Samuelsson, Ulf Hansson, Rossby Centre SMHI

Anna Wramneby, Lund University

Global carbon cyclemean stocks and fluxes for 1990s (Gt C)

oceans:38 000 +2/yr

soils: 1700

vegetation:600

atmosphere: 760 +3/yr

terrestrial ecosystems:2 300 +3/yrland use

change

fossil fuel burningcement production

92

90

8

6 2

120

123

Source: IPCC, 2007

Albedo change could offset carbon sequestrationas forests expand at high northern latitudes*

*Betts 2000Nature 408: 187

Albedo change

Radiation forcing due to albedo change

W m−2

CO2-emission yielding same radiation forcing

tC ha−1

latent heat(evapo-

transpiration)sensible

heat

sensibleheat

incomingSW radiation

incomingSW radiation

Partitioning of land surface-atmosphere energy fluxesdepends on vegetation type and cover

latent heat(evapo-

transpiration)

Land surface scheme of RCA3*

• forest, open land, bare ground, snow

• conifer, broadleaved forest (prescribed fractions)

• leaf phenology (prescribed)• leaf area index (scaled to

soil T)

*Samuelsson et al. 2006Nature 408: 187

Soil organicmatter

SOM dynamics

populationdynamics

migrationphenology& growth

Vegetation

climateCO2

LPJ-GUESS – a process-based ecosystem modelling framework*

*Smith et al. 2001Global Ecology and Biogeography 10: 621

0

5

10

15

20

0

5

10

15

20Model Model

Bio

mas

s (k

gC m

−2)

0

4

8

12

16

0

4

8

12

16Pollen record Pollen recordP

olle

n ac

cum

ulat

ion

rate

Years before present Years before present200040006000800010,000 0 200040006000800010,000 0

Pinus sylvestrisPicea abiesPopulus tremula

Betula spp.Alnus incanaUlmus glabra

Quercus roburTilia cordataCorylus avellana

*Miller et al. 2008Journal of Ecology

Aborrtjärnen, Sweden 63° 53’ N Laihalampi, Finland 61° 29’ N

Modelling Holocene vegetation history in Fennoscandia*

Observed and modelled changes in leaf phenology and LAI*

*Lucht et al. 2002.Science 296: 1687-1689

Global land areasnorth of 40°N

0.100.05

0−0.05−0.10−0.15

0.100.05

0−0.05−0.10−0.15

1996 1997 1998 1996 1997 1998

Net

eco

syst

em C

exc

hang

e (k

gC m

−2m

o−1 )

Temperate deciduous(Denmark 55° 29’ N, 11° 39’ E)

Boreal conifer(Finland 61° 51’ N, 24° 17’ E)

Temperate conifer(Scotland 56° 36’ N, 3° 48’ W)

Mediterranean conifer(France 44° 43’ N, 0° 05’ E)

eddy covariance datacohort modelpopulation model

flux to atmosphereflux to ecosystem

Carbon exchange of European forest ecosystems*

*Morales et al. 2005Global Change Biology 11: 2211

boundarylayer

vegetation

soilwater

snow

ecosystem model

boundarylayer

vegetation

soilwater

snow

land surface scheme rest of RCM

climate and weatherclimate and weather climate andweather

RCA-GUESS: a coupled regional climate-terrestrial vegetation model

soil carbon

fraction of conifer,broadleaved forest,open land, bare ground

roughness, albedo,displacement heightevaporation,transpiration

incoming SW radiation photosynthesis,stomatal conductance

interception, displacement height, radiation partitioning,transpiration

near-canopytemperature

respiration,photosynthesis,canopy conductance,fire

soil water stomatal conductance,soil respiration,fire

soil temperature

GUESS tells RCA Used by RCA for RCA tells GUESS Used by GUESS for

respiration

leaf area index(LAI)

Surface temperature (°C) Precipitation (mm mo−1) Cloudiness (%)

RCA3-GUESS − CRU RCA3-GUESS − ERA40 RCA3-GUESS − CRU

RCA3-GUESS ERA40 1961-1990 JJA

Comparison of modelled to observed climate

RCA3-GUESS Ver 070709

Leaf

are

a in

dex

2021-291961-902021-291961-90

RCA3-GUESS

RCA3

Change in JJA leaf area index ΔLAI

Simulated change (2020-2029)−(1961-1990) RCA3-GUESS ECHAM5-A1B Transient

Simulated changes in vegetation structure

Leaf

are

a in

dex

boreal/temperate needleleaved evergreenshade-tolerant broadleaved summergreenshade-intolerant broadleaved summergreenbroadleaved evergreenMediterranean needleleaved summergreengrass/herbaceous vegetation

trees

S Sweden Alps W Turkey

Simulated changes in vegetation composition

RCA3-GUESS ECHAM5-A1B Transient 1964-2030Forest tile

Temperature change JJA ΔT Precipitation change JJA ΔP

Feedback contribution ΔTRCAG−ΔTRCA Feedback contribution ΔPRCAG−ΔPRCA

°C mm mo−1

Quantifying feedback of vegetation structural change on climate

Simulated change (2020-2029)−(1961-1990) RCA3-GUESS ECHAM5-A1B Transient

sequestration emission

Net ecosystem C exchange (kgC m−2 yr−1)

1964-1990 2021-2030

RCA3-GUESS ECHAM5-A1B Transient 1964-2030Open land tile

Simulated change in terrestrial ecosystem carbon balance

Future prospects

• Centennial runs, stabilisation scenario, alternative emission pathways

• Land use change and management (forestry, agriculture)

• Peatlands, permafrost, non-CO2 trace gases

• Integration with global studies using ESMs

Thanks

Rossby Centre at SMHI

The Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS)

The Swedish Research Council