Report on CCSM Biogeochemistry Working Group Meeting

Seventh Annual CCSM Workshop, The Village at Breckenridge

Co-Chairs: Inez Fung and Scott Doney

27 June 2002

The CCSM Biogeochemistry Working Group met for about half a day at the annual CCSM meeting. The meeting was divided among presentations on the current status of the CCSM-1 carbon-climate experiments ("Flying-Leap-0"), progress on development of the biogeochemical modules for the CCSM-2 component models, entrepreneurial research projects, and general discussion.

CCSM-1 Carbon-climate "Flying Leap-0" (Doney)

• Ocean: Prognostic new production with iron - decreased global export ~4.5 PgC/y as particles; improved seasonal cycle; weakened equatorial dominance
  
• Implement parameterizations for full depth ocean iron biogeochemistry and scavenging. The scavenging rate is: proportional to Fe concentration, particle flux, dissolved organic matter, and a small background; increases nonlinearly above 0.6 nM; partitioned so that some fraction is immediately removed from system and the reset is transported downward on particles and can be remineralized.
• Land: prototypes for prognostic LAI and allocation; still working out the details.
• Have completed land-atmosphere and ocean-atmosphere spin-up experiments; hope to have fully coupled carbon-climate land-ocean-atmosphere control simulation going in the Fall.

Marine Eco-biogeochemistry for CCSM2 (Doney)

• Completed - Porting of BGC code from NCOM to POP; incorporation of a multi-species, multi-nutrient ecosystem model following Moore et al. (2002a; 2002b)
• In progress - Couple ecosystem model and BGC code, compute equilibrium. solutions of coupled model, and explore subsurface remineralization and scavenging parameterizations.
• Future - Incorporate trace gases, microbial loop, sediments, the coastal ocean and river biogeochemistry.
• Phytoplankton-iron limitation - Fe key reaction center in metabolic energy transfer enzymes; growth proportional to cellular Fe/C ratio (currently ignoring the large contrast between open ocean and coastal cellular Fe utilization).
• Phytoplankton growth model - add iron to Geider et al. nitrogen based model using iron results from K Johnson (MBARI) Eq Pac incubation experiment (growth rate vs. added Fe) and Sunda and Huntsman (1997) cellular Fe/C. Luxury uptake not yet in model.
• Results - Equatorial Pacific NO3 maximum too broad; global NPP - 39.54 GtC/yr vs. SeaWiFS - 50.02 GtC/yr; model under-predicts coastal production; nitrogen fixation pattern - reasonable; sinking fluxes computed for C, biogenic Si, CaCO3; export ratio
• CaCO3 closure; currently have no sediments and no rivers so all the sinking CaCO3 is remineralized.

Terrestrial Biogeochemistry in CCSM-2 (Thornton)

• Peter reviewed the proposed new CLM2 code architecture with three levels: Li - land types, geomorphology; Cij - soil column for disturbance history and age class distribution; Pijk- plant function types - multiple functional types competing for resources in single Cij
• Code 2.1 code review - the committee formed following the Spring BGC and land working group meeting recommended adopting this code architecture as new platform for land model R&D. Response of SSC to recommendation? Requires new history routines to handle land output from multiple levels of hierarchy.
• Proposed land C/N BGC components:
  • Net ecosystem exchange (NEE) - need accurate gross primary production, GPP and autotrophic R_a and heterotrophic R_h respiration.
  • Photosynthesis - parameterization of VCMAX, fraction of leaf N in RuBisCO, T_opt for carboxylation and oxygenation reactions of RuBisCO. Age dependent.
  • Modified sunlit/shaded canopy. Leaf T calculated separately for sunlit and shaded canopy. Leaf longevity a central concern for evergreen types.
  • Stomatal control - does the Ball-Berry approach need to be re-parameterized for new treatment of Vcmax? Simpler approach? Not priority for change at this time.
  • N limitation effects on GPP, stomatal conductance, and allocation
  • Maintenance respiration as a function of tissue N
  • Mortality and fine root allocation as a function of age
  • Age class distribution - continuous migration of area between bins
  • Hetertrophic respiration R_h - competition for mineral N
  • Spin-up - exploring new strategies with Nan Rosenbloom
  • N-limitation on R_h - to prevent runaway Q10.
  • Vcmax = (area based leaf N) x (fraction of leaf N in Rubisco) x (g Rub/gN_Rub) x …Vcmax - veg type dependent
  • Feedback from N from decomposition to GPP
  • Bonan: CLM is dry model - too much interception. How to separate GCM problems from ecophysiology?
  • Francis - other WG have found coupling magnifies the problem. Need to know what the dominant feedbacks allowed in the loop. Tune the dominant feedback loop? What are dominant feedback loops? How to test those loops? Need to know them first, asap. Thornton - N cycle, disturbance. FB: can change climate without changing NEE. Ojima:

Bonfils -

• Examining the internal variability and land water/CO2 linkages within the Leap0 spinup integrations
• atm-ocn : GPP 116 +/- 23 PgC/yr
• EOF/PC 1&2 - (MAM): GPP increases with T, reduces Bowen ratio.

Ojima: Integrated Regional Carbon (IRC) Project - grid-cohort system model coupling

• The IRC is a consortium of eco modelers. www.nrel.colostate.edu/projects/irc/
• Grid-cohort: ensemble method. Landscape units {cohort = age, management, plant soil types}. Each cohort has it's own "instantation" of an ecosystem model. Disturbance and land used to create new cohorts. Cell aggregates and distributes fluxes to external climate model. Similar to Thornton architecture scheme.
  • Land use: cropping, forestry, settlements
  • Disturbance: fire, flood, tilling, harvest … divides a cohort into two cohorts. Succession rules specify response
  • Aggregation: contingent upon cohort similarity
• Land-use: Biome300 - Ramakutty-Foley
• 1800-2000: evolution of agriculture for southeast, eastern colorado, corn belt, …
• DayCentury. HDF5 output; MPI version (distributed parallel)…
• Q: strategy for testing model… remote sensing… forest inventory, …

May Ver/Fred Mackenzie group: Modeling C-N-P BGC in coastal margin

• Human perturbation on global biogeochemical cycles: (500, 140, 12, 140) x 10^6 tons of C, N, P, and S, respectively; 25% of evapotranspiration (through agriculture), utilize 55% of runoff, …
• TOTEM - coupled C, N, P, S box model for linking land, rivers fluxes, estuaries and coastal and open ocean; 13 reservoirs. Land biota, humus, inorganic soil, soil water …
• What's the future of global coastal zone net primary production NPP and air-sea exchange in light of increase inputs from land?
  • Meybeck and Ragu unpublished GLORI database - will not be published, but Meybeck is willing to share the data if asked. Huge variation in data for 450 rivers for riverine DOC/POC, DIN/DIP. A lot of attention to small rivers, especially in Asia.
  • Refractory stuff - what to do?
  • Organic C balance in coastal zone -7e12 moles C/yr in 1700, and decreasing to -20e12 in 2000. Coastal CO2 flux - 0.2 GTC/yr emission in 1700, increasing to 0 in 2000 and transitioning to net sink in 2012 (because of increasing FF CO2 in atm).
  • New production increases due to P inputs. There remains excess N. High-medium-low population + H-M-L T predictions à release of P from land driven by soil T.
• How will changes in atmospheric CO2 affect carbonate saturation state and biological carbonate production in the global coastal ocean?
  • Chemistry: Uptake of gaseous CO2 up à CO3= down à saturation state down.
  • Model: 3 species: aragonite, calcite, Mg-calcite. pH drops, but no danger of dissolving carbonates. Mg-calcite buffers …
  • Increasing consumption of terrestrial organic C and carbon ppt counteracts and weakens coastal zone to act as a strong sink for CO2.

Pamela Martin/David Archer: Carbon cycling on the seafloor: Muds Sediment Model in POP

• Fe, Mn, S redox chemistry… OCMIP: carbonate, organic C and Silica rain rates depend on water chemistry and what they imply in terms of deep sea sediments. Sediment data as verification pool. The MUDS model has 9000 bottom grid points, updated every 10 years. MUDS maybe on separate nodes.
• Some issues: fossil fuel invasion - continental margins
• How to do paleo-climate simulation? First application: formation of sapropels? (layers of high POC) in Mediterranean
• Sundquist - important to get present day ocean C right; to what level of detail do we need rivers or sediments, and what should be our priorities?

Doney - Group CCSM2-carbon model

• Focus on key processes and feedbacks in coupled system
• Involve community in land and ocean model formulation (entrepreneurial research -> common path)
  • Complete strawperson code and solution; distribute write-up, code and solution;
  • iterate on framework and parameterizations
• create diagnostics and evaluation metrics
• define biogeochemical coupler requirements
• coupling - testing, evaluation, controls, emission evaluations)
• Base model for other studies - e.g. leap1

Natalie Mahowald: CSM Flying Leap1 - moore/zender/thornton/levis/et al

• Ocean ecosystem based model including iron cycling and N fixation (Moore et al.)
• Land - Thornton - C and N BGC linked to growth
• Mineral aerosols (Levis/Zender) 4 size classes with sub-class variation + radiative feedbacks in CAM (Zender)
• Ready for coupling end of 2002.
• Land use - unclear what to do
• MATCH dust in CAM (Rasch, in progress)
• Flux Coupler - not currently setup for BGC; need to communicate needs
• Pipes from reservoir-reservoir (how to prioritize) and variables inside pipes (fluxes and state variables). Need to consider averaging periods …

Beth Holland: bioatm - reactive C-N cycle, including trop chemistry and BGC

• Entrepreneurial with aspirations of becoming community effort
• 1st objective: VOC: Isoprene, land use change, trop chemistry (ozone);
  • 3 case scenarios:
    • base case - MOZART2;
    • 1: simulate forest replace with pasture and suburban landscapes - low Nox case: 50% of each grid cell in Amazon, isoprene flux x 1/8; high NOX - SE US, 50% of each grid, flux x 1/8.
    • 2. forests replaced with plantations of high emitting tree species - NW US and Amazon
  • changes in global O3 - small
• 2nd objective - develop dry deposition submodel based on CLM - Resistance = stomatal resistance + mesophyll resistance + cuticular resistance + canopy turbulence + in-canopy resistance +
• VOC emission workshop, Sept. 2002 Lancaster England
• Workshop with U Michigan early 2003 to discuss measurements needed
• Future plans - trop chemistry coupling - 1-2 day workshop October 2002 …

Peter Hess, J-F Lamarque, Louisa Emmons, XX Tie, Holland, McKenna

• Proposed framework: online CAM-chemistry (GCM winds) or off-line CAM-line (analyzed winds) à species transport, species chemistry, emissions, physical loss, land processes. Consistent framework for testing model against observations.
• Climate-chemistry simulations of last 30-40 years à chemical variability
• Variability due to meteorology - transport and water vapor - (fixed SST, variable SST, stratosphere-trop exchange); due to photolysis rates (clouds, stratospheric O3, aerosols); due to emissions (anthrop, natural)
• Francis: how to deal with vertical mixing?

Dave Schimel, Scott Doney, Linda Mearns, Inez Fung, Tony Janetos Leap2.0 and beyond

• Coupled BGC/Assessment effort being proposed
• Large ensemble of coupled runs for future climate
• Significant stakeholder involvement and outreach component - Janetos
• BGC, Chemistry/Climate and CCA WG design model configuration and experimental design - multi-gas scenarios; need land use change and disturbance regimes. Model resolution is crucial.
• Opportunity for major computing on Earth Simulator in Japan - ca 10,000 model years
• First workshop in July on scenario development

Doney - wrap-up

• Update 5-year plan for SSG; build on materials for CSL request
  
• NSF Steve Meachem - facilitate and encourage university participation
  

Participant List

David Baker
Ian Baker
Adriana Beltran
Gordon Bonan
Celine Bonfils
Francis Bretherton
Shaoping Chu
William Collins
Alan Condron
Andrew Conley
Scott Denning
Scott Doney
David Fillmore
Inez Fung
Kevin Gurney
Andrea Hahmann
Matthew Hecht
Peter Hess
Forrest Hoffman
Elisabeth Holland
Tkashi Ishii
Jasmin John
Fortunat Joos
John Kleist
Joanie Kleypas
Zavareh Kothavala
Jean-Francois Lamarque
Samuel Levis
Keith Lindsay
Brett Longworth
Lixin Lu
Natalie Mahowald
Pamela Martin
Rebecca McKeown
Guo-Yue Niu
Dennis Ojima
Elisabetta Pierazzo
Philip Rasch
Nan Rosenbloom
Kevin Schaefer
Dave Schimel
Lisa Sloan
Pamela Stephens
John Taylor
Starley Thompson
Peter Thornton
Daisuke Tsumune
Leah May Ver
Mariana Vertenstein
Guiling Wang
Youlong Xia
Woo-Sun Yang
Hongbin Yu
Charles Zender
Xubin Zeng