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Overview: Diagnosis and prognosis of effects of changes in lake and wetland extent on the regional carbon balance of northern Eurasia. Ted Bohn Princeton Workshop, December 4-6, 2006. Outline. Project Details Motivation Carbon, Water, and Climate High-latitude Wetlands Lakes

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Overview: Diagnosis and prognosis of effects of changes in lake and wetland extent on the regional carbon balance of northern Eurasia

Ted Bohn

Princeton Workshop, December 4-6, 2006


Outline
Outline lake and wetland extent on the regional carbon balance of northern Eurasia

  • Project Details

  • Motivation

    • Carbon, Water, and Climate

    • High-latitude Wetlands

    • Lakes

  • Science Questions

  • Strategies

    • Modeling

    • Remote Sensing

    • Validation: In-Situ Data

  • Preliminary Results

  • Future Work

(Freeman et al., 2001)


Project details
Project Details lake and wetland extent on the regional carbon balance of northern Eurasia

Part of Northern Eurasia Earth Science Partnership Initiative (NEESPI)

Personnel:

  • PI:

    • Dennis Lettenmaier (University of Washington, Seattle, WA, USA)

  • Co-PIs:

    • Kyle MacDonald (NASA/JPL, Pasadena, CA, USA)

    • Laura Bowling (Purdue University, Lafayette, IN, USA)

  • Collaborators:

    • Gianfranco De Grandi (EU Joint Research Centre, Ispra, Italy)

    • Reiner Schnur (Max Planck Institut fur Meteorologie, Hamburg, Germany)

    • Nina Speranskaya and Kirill V. Tsytsenko (State Hydrological Institute, Russia)

    • Daniil Kozlov and Yury N. Bochkarev (Moscow State University)

    • Martin Heimann (Max Planck Institut fur Biogeochemie, Jena, Germany)

    • Ted Bohn (University of Washington, Seattle, WA, USA)

    • Erika Podest (NASA/JPL, Pasadena, CA, USA)

    • Ronny Schroeder (NASA/JPL, Pasadena, CA, USA)

    • KrishnaVeni Sathulur (Purdue University, Lafayette, IN, USA)


NEESPI Region lake and wetland extent on the regional carbon balance of northern Eurasia

Wetlands

Forest

Crops

Grass/Shrub/Tundra


Carbon water and climate
Carbon, Water, and Climate lake and wetland extent on the regional carbon balance of northern Eurasia

  • Human impact since 1750

    • Emissions of 460-480 Gt C (as CO2)

      • Burning of fossil fuels: 280 Gt C

      • Land-use change: 180-200 Gt C

    • Atmosphere’s C pool has only increased by 190 Gt C (~ 40% of emissions)

    • Land and ocean have taken up the remainder (roughly 150 Gt C, or 30%, each)

  • Ability of land/ocean to continue absorbing C is limited and depends on climate

  • Hydrology plays a major role

(Keeling et al., 1996)


Terrestrial carbon stocks
Terrestrial Carbon Stocks lake and wetland extent on the regional carbon balance of northern Eurasia

(IPCC 2001)

  • Wetland soils store the most carbon per unit area

  • Wetland extent depends on hydrology

  • Wetland behavior depends on hydrology


High latitude wetlands boreal peatlands
High-Latitude Wetlands – Boreal Peatlands lake and wetland extent on the regional carbon balance of northern Eurasia

  • Carbon Sink

    • cold T & saturated soil for most of year

    • NPP > Rh and other C losses

    • 70 TgCyr-1 (Clymo et al 1998) - very uncertain

    • Current storage: 455 Pg C (1/3 of global soil C, ¼ of global terrestrial C) (Gorham 1991)

Dual role in terrestrial carbon cycle

  • Methane Source

    • Saturated soil → anaerobic respiration

    • 46 TgCyr-1 (Gorham 1991; Matthews & Fung 1987) very uncertain

    • Roughly 10 % of global methane emissions

    • Methane is a very strong greenhouse gas

(Wieder, 2003)

  • Balance of these effects depends on climate

    • Climate feedback


Peatland h 2 o budget
Peatland H lake and wetland extent on the regional carbon balance of northern Eurasia 2O Budget

Precipitation (P)

Evaporation (E)

Transpiration (Tr)

Living Biomass

Surface Runoff (Qs)

Acrotelm

To

Ocean

Water Table

Streams

From Upslope

Subsurface Flow (Qsb)

Groundwater

Catotelm

Water Table = f(P, E, Tr, Qs, Qsb)


Peatland c budget
Peatland C Budget* lake and wetland extent on the regional carbon balance of northern Eurasia

(NPP – Rh ≈ 200-300 Tg C/y)

CO2

CH4 (45 Tg C/y)

CO2

CO2 (25-40 Tg C/y)

Fire

NPP

Living Biomass

CO2 (25-50 Tg C/y)

Litter

Acrotelm

Outgassing

Aerobic Rh

Org C

To

Ocean

Water Table

DOC

DOC

Streams

(25 Tg C/y)

Anaerobic Rh

DOC

From Upslope

Subsurface Flow (Qsb)

Catotelm

Carbon balance = f(NPP, T, water table, fire, DOC export)

* Extremely crude estimates!


Peatland Distribution in N. Eurasia lake and wetland extent on the regional carbon balance of northern Eurasia

West Siberian

Lowlands

Majority of world’s peatlands are in Eurasia

(mostly peatlands)

  • Belt of major peat accumulation overlaps with:

  • boreal forest (taiga)

  • permafrost

(Gorham, 1991)


High latitude lakes
High-Latitude Lakes lake and wetland extent on the regional carbon balance of northern Eurasia

  • Accumulate large amounts of carbon

    • Lakes worldwide accumulate 42 Gt C/yr in their sediments (Dean and Gorham, 1998)

  • Vent terrestrial carbon to the atmosphere

    • Respiration > Productivity in most lakes (Kling et al., 1991, Cole et al., 1994)

    • R:P correlates with DOC (del Giorgio et al., 1994)

    • DOC is imported from surrounding terrestrial ecosystems (especially true near wetlands)

    • Some Arctic terrestrial ecosystems may become net sources of atmospheric carbon when DOC loss is taken into account

  • NE Siberian thaw lakes are strong methane sources (Walter et al., 2006)

    • Decomposition of “fresh” carbon in newly-thawed soil under lakes

    • Substantial amounts of C could be liberated as methane if all permafrost were to thaw


Lake h 2 o budget
Lake H lake and wetland extent on the regional carbon balance of northern Eurasia 2O Budget

Precipitation (P)

Evaporation (E)

Streams, Surface Runoff,

Groundwater

Streams

To

Ocean

Balance: P + Qin = E + Qout


Lake c budget
Lake C Budget lake and wetland extent on the regional carbon balance of northern Eurasia

CO2

CO2, CH4

CO2

Dis-

solution

Evasion

NPP

Algae

Aerobic

Rh

DOC

Streams, Surface Runoff,

Groundwater

POC

DOC

POC

(~30%)

Streams

Sediment Deposition

To

Ocean

42 Gt C/yr

Anaerobic Rh

Balance: TOCin + NPP = Rh + TOCout


High latitudes have experienced change
High-Latitudes Have Experienced Change lake and wetland extent on the regional carbon balance of northern Eurasia

  • Increasing precipitation (Serreze et al., 2000)

  • Increasing river discharge (Peterson et al., 2002)

  • Growing/shrinking lakes (Smith et al., 2005)

  • Thawing of permafrost (Turetsky et al., 2002)

  • Increased outgassing of methane (Walter et al., 2006)


Doc export
DOC Export lake and wetland extent on the regional carbon balance of northern Eurasia

  • DOC export from Arctic land into Arctic Ocean: 25.1 Tg C/y (Opsahl et al. 1999)

  • Peatlands supply most of this (Pastor et al. 2003)

  • Higher DOC in streams can drive outgassing of CO2 (evasion)

  • Fry and Smith, 2005:

  • Permafrost zone: DOC export small

  • Permafrost-free zone: DOC export large

(Opsahl et al., 1999)


Main science issues
Main Science Issues lake and wetland extent on the regional carbon balance of northern Eurasia

  • High-latitude lakes and wetlands are potentially large sources of CO2 and CH4

  • Fluxes and extent are sensitive to climate (especially hydrology)

  • Lake/wetland extent is underrepresented by low-resolution remote sensing

  • Long time series of high-resolution remote sensing data not available


Science questions
Science Questions lake and wetland extent on the regional carbon balance of northern Eurasia

  • Overarching Science Questions:

    • How have changes in lake and wetland extent in northern Eurasia over the last half-century affected the region’s carbon balance?

    • What will the effects be over the next century?

  • Sub-Topics:

    • What areas within the region have been/will be affected by changes in lake/wetland extent?

    • How are ongoing changes in the tundra region affecting the dynamics of wetlands?

      • Changes in permafrost active layer depth

    • How are/will these changes affect the carbon balance of the region?

    • How well can current sensors (MODIS, SAR) detect changes in wetland extent?

    • Can high-resolution SAR products be used to provide seasonal and interannual variations in lake/wetland extent?

      • Extend the rapid repeat cycle of lower-resolution products like MODIS


Modeling strategy
Modeling Strategy lake and wetland extent on the regional carbon balance of northern Eurasia

Integrate several models:

  • VIC – hydrology (incl. frozen soil, water table, explicit lake/wetlands model)

  • BETHY – fast ecosystem processes on sub-daily timescale (photosynthesis, respiration)

  • Walter-Heimann (WHM) methane model – methane emissions on daily timescale

    • CH4 flux = f(water table, soil T, NPP)

  • LPJ – slow ecosystem processes on yearly timescale (change in plant assemblage, fire)


Vic large scale hydrology
VIC: Large-scale Hydrology lake and wetland extent on the regional carbon balance of northern Eurasia

  • Typically 0.5- to 0.125-degree grid cells

  • Water and energy balance

  • Daily or sub-daily timesteps

Inputs

  • Meteorology:

    • Gridded ERA-40 reanalysis

  • Soil parameters:

    • FAO soil properties

    • Calibration parameters

      • Soil layer depth

      • Infiltration

      • Baseflow

  • Vegetation parameters:

    • Observed veg cover fractions (AVHRR)

    • Veg properties from literature

      Outputs

  • Moisture and energy fluxes and states

  • Hydrograph (after routing)

Mosaic of veg tiles;

Penman-Monteith ET

Heterogeneous infiltration/runoff

Non-linear baseflow

Multi-layer soil column


Vic lake wetland algorithm
VIC Lake/Wetland Algorithm lake and wetland extent on the regional carbon balance of northern Eurasia

soil

saturated

land surface runoff enters lake

evaporation depletes soil moisture

lake recharges soil moisture

Lake drainage = f(water depth, calibration parameter)


Model integration

(Completed) lake and wetland extent on the regional carbon balance of northern Eurasia

Model Integration

Obs Met Data or

Climate Model

Precipitation,

Air temperature,

Wind, Radiation

Obs or Projected [CO2]

  • VIC

  • Hydrology

  • BETHY

  • Photosynthesis

  • Respiration

  • C storage

  • LPJ

  • Species distribution

  • Fire

Soil moisture,

evapotranspiration

C fluxes

Plant functional types

Water table,

Soil temperature

NPP

  • Walter-Heimann Methane Model

  • Methane emissions


Validation remote sensing
Validation: Remote Sensing lake and wetland extent on the regional carbon balance of northern Eurasia

JERS: 100m SAR imagery

1 mosaic, acquired 1997/1998


Validation in situ data
Validation: In-Situ Data lake and wetland extent on the regional carbon balance of northern Eurasia

  • Landcover classifications:

    • 5-yearly landcover summaries (SHI) 1950s-1990s

  • Hydrological observations:

    • Soil moisture (SHI) 1960s-1980s

    • Evaporation (pan & actual) (SHI) 1960s-1990s

  • Carbon fluxes:

    • TCOS towers (hourly, 1998-2002)


soil moisture lake and wetland extent on the regional carbon balance of northern Eurasia

soil moisture

and T

evap

flux tower


Preliminary results
Preliminary Results lake and wetland extent on the regional carbon balance of northern Eurasia

Valdai/Fyodorovskoye Sites

Ob Site


Hydrology at valdai
Hydrology at Valdai lake and wetland extent on the regional carbon balance of northern Eurasia


Estimated Methane Emissions at Valdai lake and wetland extent on the regional carbon balance of northern Eurasia


Carbon Fluxes at Fyodorovskoye Tower lake and wetland extent on the regional carbon balance of northern Eurasia

Productivity and Respiration

g C/m2d

Net CO2 Emissions

g C/m2d

Date


Future work
Future Work lake and wetland extent on the regional carbon balance of northern Eurasia

  • Remote Sensing:

    • Validation of remote sensing classifications

      • In-situ data

      • Other remote-sensing products

    • Extension of classifications back in time via relationships with other remote sensing or in-situ products

  • Models:

    • Finish integration of models

      • Add photosynthesis, respiration, etc. to VIC

      • Take into account decomposition of carbon formerly locked up in permafrost (specifically: yedoma)?

      • DOC leaching from terrestrial systems

      • Take into account C cycling in lakes

      • Add long-term vegetation dynamics


Future work1
Future Work lake and wetland extent on the regional carbon balance of northern Eurasia

  • Validate models against historical observations

    • Landcover timeseries (from remote sensing/in situ data)

      • Lake extent (seasonal)

      • Wetland extent

      • Vegetation cover

    • Hydrological fluxes and storage

      • soil moisture and temperature

      • evaporation

      • runoff

      • water table

      • snow depth and cover

    • Carbon fluxes and storage

      • CO2

      • CH4

      • standing biomass

      • soil carbon profiles

      • DOC in soil, streams, lakes

      • C accumulation rates in soils, lake sediments

  • Expand from point estimates to regional estimates

  • Use climate models to predict changes over next century


Thank you
Thank You lake and wetland extent on the regional carbon balance of northern Eurasia

(Corradi et al., 2005)


Peatlands long term c sink but initial greenhouse source

6 g CO lake and wetland extent on the regional carbon balance of northern Eurasia 2/m2day over next 20 years

1 g CO2/m2day over next 100 years

0 net greenhouse effect

over next 149 years

Net greenhouse

sink thereafter

Peatlands: Long-term C Sink butInitial Greenhouse Source

  • Methane Greenhouse

  • Warming Potential (GWP):

  • 62 (20 years)

  • 23 (100 years)

  • 7 (500 years)

  • Compared to CO2, CH4 is

  • a stronger, but shorter-lived,

  • greenhouse gas

Adding 1 m2 of peatland produces

the equivalent CO2 emissions:

Removing 1 m2 of peatland

is initially a greenhouse sink,

then a source

Friborg et al., 2003


Modeling strategy1
Modeling Strategy lake and wetland extent on the regional carbon balance of northern Eurasia

  • Previous Studies:

    • Coarse statistical relationships between soil moisture and methane emissions

    • Some used explicit ecosystem C-cycling

    • Some handled frozen soils

    • None used explicit lake/wetland formulations

    • Large disagreement on magnitude of future emissions


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