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 Ankur R Desai, UW-Madison desai@aos.wisc.edu
What’s in the airwaves? Lakes, lands, & carbon The atmospheric tracer view An eddy flux view Lake Superior & micrometerology Ankur R Desai, UW-Madison desai@aos.wisc.edu
Lakes, Land, & Carbon Ankur R Desai, UW-Madison desai@aos.wisc.edu
The big picture Sarmiento and Gruber, 2002, Physics Today Ankur R Desai, UW-Madison desai@aos.wisc.edu
Slightly smaller picture Cardille et al. (2007) Ankur R Desai, UW-Madison desai@aos.wisc.edu
Real Numbers Are Complicated Atmos. flux: ~3-12 Tg yr-1 - 35-140 gC m-2 yr-1 Ankur R Desai, UW-Madison desai@aos.wisc.edu
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 Ankur R Desai, UW-Madison desai@aos.wisc.edu
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? Ankur R Desai, UW-Madison desai@aos.wisc.edu
The Atmospheric Tracer View Ankur R Desai, UW-Madison desai@aos.wisc.edu
Global CO2 NOAA/ESRL/GMD/CCGG Ankur R Desai, UW-Madison desai@aos.wisc.edu
Global Experiment Marland et al., DOE/CDIAC Ankur R Desai, UW-Madison desai@aos.wisc.edu
The Inverse Idea Ankur R Desai, UW-Madison desai@aos.wisc.edu
The Inverse Idea Courtesy S. Denning, CSU Ankur R Desai, UW-Madison desai@aos.wisc.edu
The Inverse Idea Peters et al (2007) PNAS Ankur R Desai, UW-Madison desai@aos.wisc.edu
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- Ankur R Desai, UW-Madison desai@aos.wisc.edu
A 1-point Inversion [CO2] Air flowing over lake > [CO2] over land Ankur R Desai, UW-Madison desai@aos.wisc.edu
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) Ankur R Desai, UW-Madison desai@aos.wisc.edu
The Boundary Layer Problem Courtesy of S. Spak, UW Ankur R Desai, UW-Madison desai@aos.wisc.edu
Getting More Sophisticated Courtesy M. Uliasz, CSU Tracer transport modeled influence function August 2003 at WLEF entire domain water land Ankur R Desai, UW-Madison desai@aos.wisc.edu
Great Lakes Influence at WLEF Land: 85.4% Lake Superior: 9.5% Lake Michigan: 1.8% Other water: 3.1% Ankur R Desai, UW-Madison desai@aos.wisc.edu
The Potential Potential exists for constraining flux and interannual var. with local observations of CO2 1996 2003 Ankur R Desai, UW-Madison desai@aos.wisc.edu
An Eddy Flux View Ankur R Desai, UW-Madison desai@aos.wisc.edu
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 Ankur R Desai, UW-Madison desai@aos.wisc.edu
Eddies! Ankur R Desai, UW-Madison desai@aos.wisc.edu
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 Ankur R Desai, UW-Madison desai@aos.wisc.edu
The Data Ankur R Desai, UW-Madison desai@aos.wisc.edu
The Data Pt. 2 Ankur R Desai, UW-Madison desai@aos.wisc.edu
The Data Pt. 3 Ankur R Desai, UW-Madison desai@aos.wisc.edu
Much Data… Ankur R Desai, UW-Madison desai@aos.wisc.edu
A CHEAS-y Lake Ankur R Desai, UW-Madison desai@aos.wisc.edu
Scale This! Ankur R Desai, UW-Madison desai@aos.wisc.edu
Some Observations Desai et al, 2008, Ag For Met Ankur R Desai, UW-Madison desai@aos.wisc.edu
The 6x6 km View Ankur R Desai, UW-Madison desai@aos.wisc.edu
More Observations Ankur R Desai, UW-Madison desai@aos.wisc.edu
Land History Ankur R Desai, UW-Madison desai@aos.wisc.edu
Land History Have to account for age structure too Ankur R Desai, UW-Madison desai@aos.wisc.edu
All The ChEAS Flux Data Ankur R Desai, UW-Madison desai@aos.wisc.edu
Magically Scaled Ankur R Desai, UW-Madison desai@aos.wisc.edu
The “Bottom-Up” Flux Ankur R Desai, UW-Madison desai@aos.wisc.edu
Evaluation “Top-down” vs “Bottom-up” Ankur R Desai, UW-Madison desai@aos.wisc.edu
Evaluation Ankur R Desai, UW-Madison desai@aos.wisc.edu
Land 1989-2006 average Ankur R Desai, UW-Madison desai@aos.wisc.edu
Lake? Ankur R Desai, UW-Madison desai@aos.wisc.edu
Lake and Land Ankur R Desai, UW-Madison desai@aos.wisc.edu
Lake Superior & Micrometeorology Ankur R Desai, UW-Madison desai@aos.wisc.edu
Better Forcing? Many observations are sparse Ankur R Desai, UW-Madison desai@aos.wisc.edu
Better [CO2] Ankur R Desai, UW-Madison desai@aos.wisc.edu
Coherent Interannual Variability Ankur R Desai, UW-Madison desai@aos.wisc.edu
Lake Interannual Variability Annual avg. dissolved organic carbon (DOC) Ankur R Desai, UW-Madison desai@aos.wisc.edu
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 Ankur R Desai, UW-Madison desai@aos.wisc.edu
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 Ankur R Desai, UW-Madison desai@aos.wisc.edu
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@aos.wisc.edu, 265-9201 More info: http://flux.aos.wisc.edu Ankur R Desai, UW-Madison desai@aos.wisc.edu