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Viewed from the air

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Adapt the MIT-GCM ocean model to simulate physical and biogeochemical ... 3D sonic anemometer. Open or closed path gas analyzer. 5--20 Hz temporal resolution ... – PowerPoint PPT presentation

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Learn more at: http://flux.aos.wisc.edu
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Title: Viewed from the air


1
Lake Superior Region Carbon Cycle
  • Viewed from the air

Ankur R Desai Atmospheric Oceanic
Sciences University of Wisconsin-Madison (and the
CyCLeS team)
Lake Superior Biogeochemistry Workshop August 5,
2008
2
Whats in the airwaves?
  • Lakes, lands, carbon
  • The atmospheric tracer view
  • An eddy flux view
  • Lake Superior micrometerology

3
Lakes, Land, Carbon
4
The big picture
  • Sarmiento and Gruber, 2002, Physics Today

5
Slightly smaller picture
  • Cardille et al. (2007)

6
Real Numbers Are Complicated
  • Atmos. flux 3-12 Tg yr-1 - 35-140 gC m-2 yr-1

7
An Oceanic Lake
  • CyCLeS Cycling of Carbon in Lake Superior
  • Adapt the MIT-GCM ocean model to simulate
    physical and biogeochemical environment of Lake
    Superior
  • Physical model of temperature, circulation
  • Mostly implemented
  • Biogeochemical model of trace nutrients and
    air-sea exchange
  • In progress

8
Interesting Questions
  • How do magnitudes of lake and land flux compare
    and what does it imply for regional carbon
    budgets? (NACP, SOCCR)
  • Are interannual variations in lake and land CO2
    surface-atmosphere flux related and if so, due to
    what environmental forcing?
  • Can we see and constrain lake (and land) flux
    from regional atmospheric CO2 observations?
  • What are impacts on atmospheric forcing
    (temperature, stable layer depth, CO2) on lake
    biogeochemistry?

9
The Atmospheric Tracer View
10
Global CO2
  • NOAA/ESRL/GMD/CCGG

11
Global Experiment
  • Marland et al., DOE/CDIAC

12
The Inverse Idea
13
The Inverse Idea
  • Courtesy S. Denning, CSU

14
The Inverse Idea
  • Peters et al (2007) PNAS

15
Inversion and a Very Big Tower
  • WLEF-TV (PBS)
  • Park Falls, WI
  • 447-m tall
  • 6 levels CO2
  • 11 to 396 m
  • 3 levels CO2 flux
  • 30,122,396 m
  • Mixed landscape
  • Representative?
  • Running 1995-

16
A 1-point Inversion
  • CO2 Air flowing over lake gt CO2 over land

17
Air and Lake CO2 Comparison
  • Simple boundary layer budget tracer study
    suggests summer 2007 efflux 4-14 gC m-2 d-1
  • extrapolated to 30-140 gC m-2 yr-1
  • Analysis requires modeling of stable marine
    boundary layer
  • Larger than traditional air-sea pCO2 exchange
    calculation
  • Requires significant respiration in water column
  • Urban et al. (in press)

18
The Boundary Layer Problem
  • Courtesy of S. Spak, UW

19
Getting More Sophisticated
  • Courtesy M. Uliasz, CSU
  • Tracer transport modeled influence function
    August 2003 at WLEF

entire domain
water
land
20
Great Lakes Influence at WLEF
  • Land 85.4
  • Lake Superior 9.5
  • Lake Michigan 1.8
  • Other water 3.1

21
The Potential
  • Potential exists for constraining flux and
    interannual var. with local observations of CO2

1996
2003
22
An Eddy Flux View
23
Eddies?
  • Tracers in boundary layer primarily transported
    by turbulence
  • Ensemble average turbulent equations of motion
    and tracer concentration provide information
    about the effect of random, chaotic turbulence on
    the evolution of mean tracer profiles with time
  • In a quasi-steady, homogenous surface layer, we
    can simplify this equation to infer the surface
    flux of a tracer

24
Eddies!
25
The Maths
  • Some simplifications made

Storage
Turbulent flux
  • Equipment
  • 3D sonic anemometer
  • Open or closed path gas analyzer
  • 5--20 Hz temporal resolution
  • Multiple level CO2 profiler

26
The Data
27
The Data Pt. 2
28
The Data Pt. 3
29
Much Data
30
A CHEAS-y Lake
31
Scale This!
32
Some Observations
Desai et al, 2008, Ag For Met
33
The 6x6 km View
34
More Observations
35
Land History
36
Land History
  • Have to account for age structure too

37
All The ChEAS Flux Data
38
Magically Scaled
39
The Bottom-Up Flux
40
Evaluation
  • Top-down vs Bottom-up

41
Evaluation
42
Land
  • 1989-2006 average

43
Lake?
44
Lake and Land
45
Lake Superior Micrometeorology
46
Better Forcing?
  • Many observations are sparse

47
Better CO2
48
Coherent Interannual Variability
49
Lake Interannual Variability
  • Annual avg. dissolved organic carbon (DOC)

50
More measurements
  • CO2 over Lake Superior
  • Continuous CO2 eddy covariance on the lake
  • Better models of stability over lakes
  • Spatial atmospheric met data
  • Temp, wind, precip?, shortwave radiation

51
Conclusions
  • On annual and decadal timescales, Lake Superior
    is possibly a source of CO2 to the atmosphere
  • This source could be on the same order of
    magnitude as the terrestrial regional sink
  • Regional carbon budgets have to take lakes into
    account
  • We can estimate this flux from a number of
    techniques
  • Lake models may need to worry about
    spatiotemporal variability in atmospheric forcing
  • Models to tie land carbon flows into lake carbon
    can be useful for Lake Superior
  • Model-data fusion/optimization/assimilation
    techniques should be explored

52
Thanks
  • Desai lab and friends Ben Sulman, Jonathan Thom,
    Shelley Knuth, Scott Spak
  • ChEAS collaborators, esp. Bruce Cook, Paul
    Bolstad, Ken Davis, D. Scott Mackay, Nic
    Saliendra, Sudeep Samanta
  • CyCLeS team Galen McKinley, Noel Urban, Chin Wu,
    Nazan Atilla, Val Bennington
  • Funding DOE NICCR, NSF, USDA, NSF/NCAR, NASA,
    NOAA, under auspices of the North American Carbon
    Program (NACP)
  • Come visit us
  • AOSS 1549, desai_at_aos.wisc.edu, 265-9201
  • More info
  • http//flux.aos.wisc.edu
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