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Lake Superior Region Carbon Cycle

Lake Superior Region Carbon Cycle. Ankur R Desai Atmospheric & Oceanic Sciences University of Wisconsin-Madison (and the CyCLeS team). Viewed from the air . Lake Superior Biogeochemistry Workshop August 5, 2008. What’s in the airwaves?. Lakes, lands, & carbon The atmospheric tracer view

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Lake Superior Region Carbon Cycle

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  1. Lake Superior Region Carbon Cycle Ankur R Desai Atmospheric & Oceanic Sciences University of Wisconsin-Madison (and the CyCLeS team) Viewed from the air Lake Superior Biogeochemistry Workshop August 5, 2008 desai@aos.wisc.edu

  2. What’s in the airwaves? • Lakes, lands, & carbon • The atmospheric tracer view • An eddy flux view • Lake Superior & micrometerology desai@aos.wisc.edu

  3. Lakes, Land, & Carbon desai@aos.wisc.edu

  4. The big picture • Sarmiento and Gruber, 2002, Physics Today desai@aos.wisc.edu

  5. Slightly smaller picture • Cardille et al. (2007) desai@aos.wisc.edu

  6. Real Numbers Are Complicated • Atmos. flux: ~3-12 Tg yr-1 - 35-140 gC m-2 yr-1 desai@aos.wisc.edu

  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 desai@aos.wisc.edu

  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? desai@aos.wisc.edu

  9. The Atmospheric Tracer View desai@aos.wisc.edu

  10. Global CO2 • NOAA/ESRL/GMD/CCGG desai@aos.wisc.edu

  11. Global Experiment • Marland et al., DOE/CDIAC desai@aos.wisc.edu

  12. The Inverse Idea desai@aos.wisc.edu

  13. The Inverse Idea • Courtesy S. Denning, CSU desai@aos.wisc.edu

  14. The Inverse Idea • Peters et al (2007) PNAS desai@aos.wisc.edu

  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- desai@aos.wisc.edu

  16. A 1-point Inversion • [CO2] Air flowing over lake > [CO2] over land desai@aos.wisc.edu

  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) desai@aos.wisc.edu

  18. The Boundary Layer Problem • Courtesy of S. Spak, UW desai@aos.wisc.edu

  19. Getting More Sophisticated • Courtesy M. Uliasz, CSU • Tracer transport modeled influence function August 2003 at WLEF entire domain water land desai@aos.wisc.edu

  20. Great Lakes Influence at WLEF • Land: 85.4% • Lake Superior: 9.5% • Lake Michigan: 1.8% • Other water: 3.1% desai@aos.wisc.edu

  21. The Potential • Potential exists for constraining flux and interannual var. with local observations of CO2 1996 2003 desai@aos.wisc.edu

  22. An Eddy Flux View desai@aos.wisc.edu

  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 desai@aos.wisc.edu

  24. Eddies! desai@aos.wisc.edu

  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 desai@aos.wisc.edu

  26. The Data desai@aos.wisc.edu

  27. The Data Pt. 2 desai@aos.wisc.edu

  28. The Data Pt. 3 desai@aos.wisc.edu

  29. Much Data… desai@aos.wisc.edu

  30. A CHEAS-y Lake desai@aos.wisc.edu

  31. Scale This! desai@aos.wisc.edu

  32. Some Observations Desai et al, 2008, Ag For Met desai@aos.wisc.edu

  33. The 6x6 km View desai@aos.wisc.edu

  34. More Observations desai@aos.wisc.edu

  35. Land History desai@aos.wisc.edu

  36. Land History • Have to account for age structure too desai@aos.wisc.edu

  37. All The ChEAS Flux Data desai@aos.wisc.edu

  38. Magically Scaled desai@aos.wisc.edu

  39. The “Bottom-Up” Flux desai@aos.wisc.edu

  40. Evaluation • “Top-down” vs “Bottom-up” desai@aos.wisc.edu

  41. Evaluation desai@aos.wisc.edu

  42. Land • 1989-2006 average desai@aos.wisc.edu

  43. Lake? desai@aos.wisc.edu

  44. Lake and Land desai@aos.wisc.edu

  45. Lake Superior & Micrometeorology desai@aos.wisc.edu

  46. Better Forcing? • Many observations are sparse desai@aos.wisc.edu

  47. Better [CO2] desai@aos.wisc.edu

  48. Coherent Interannual Variability desai@aos.wisc.edu

  49. Lake Interannual Variability Annual avg. dissolved organic carbon (DOC) desai@aos.wisc.edu

  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 desai@aos.wisc.edu

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