Isotopes in the CCSM

1
Isotopes in the CCSM

• No resources in NCAR community effort
• NCAR efforts to organize Andrew Gettelman and
  Natalie Mahowald
• Identify priorities
• Identify gaps/complementary and overlaping
  activities
• Make plan to implement water and carbon dioxide
  isotopes into CCSM
• Organizational meeting (June, 2003) community
  indicated there was a need for a workshop and
  plan
• CCSM Isotope workshop (Jan, 2004) Identified
  Science questions, Priorities and Work plan (with
  Inez Fung and Bette OttoBliesner on
  organizational committee)

2

• Water Isotopes can help address following science
  questions
• Paleoclimate (many proxies are isotopes)
• Upper troposphere/lower stratospheric transport
• Water cycle improvements
• Improve parameterizations of cloud processing,
  transport
• Improve understanding
• Surface Water budget
• Ocean circulation
• Need for some carbon
• dioxide isotopes

Figure courtesy of Gavin Schmidt
3

• Carbon dioxide isotopes (delO18)
• Can provide information about sources and sinks
  of carbon dioxide in atmosphere and plants
• Intimately linked with water isotopes in the
  plants
• Requires links to water in soils and plants

Figure courtesy of Chris Still
4

• Carbon dioxide isotopes
• (C13) Differentiates between different land
  sources and sinks of carbon dioxide (land, ocean,
  C3/C4 plants)
• (C14-bomb C14) Provides information about
  reservoir lifetimes of carbon in different pools
  (e.g. woody mass, roots, etc.)

5
Work Plan

• Priorities (1) Water Isotopes, (2) Carbon
  dioxide isotopes
• Water Isotopes ongoing work by
• David Noone (CU), Sun Wong (Maryland), Andrew
  Gettelman (NCAR)
• Jung Eun Lee (UCB) simple approach
• Difficulties
• Moving target (CCM3-CAM2-gtCAM3)
• Problems in physics, transport code makes water
  isotopes difficult to implement
• Few NCAR resources (need to incorporate into
  development branch, etc.)

6
Carbon dioxide isotopes (work plan)

• Entrepeneurial work by
• Bill Riley, Chris Still and David Noone to
  incorporate delO18 isotopes into CLM (from LSM)
• Scott Denning and Neil Suits to incorporate
  delC13 into CLM
• delC14 ?(relatively easy once above done, but no
  plan)
• Ocean model isotopes (tracer work in progress)
• Problems
• Moving targets (LSM vs. CLM), hopefully reduced
  in future
• Needs many new features (e.g. new tracers
  advected in plants in CLM)
• Lack of BGC resources (land working group
  supportive)

7
CAM2 - Precipitation Weighted Annual Mean ?18O in
Precipitation
CAM2
GNIP Obs.

• Reasonable first simulation of water isotopes in
  precipitation in CAM2.

Jung-Eun Lee and Inez Fung
8
Mean Annual ?D in vapor
CAM2

• Observed
• Nebraska, USA (Ehhalt, 1974)
• Heidelberg, Germany (Taylor, 1972 only up to 5
  km)
• Stratosphere (Pollock, 1980)
• From Araguas-Araguas
• et al., 2000

• CAM 2 captures general feature of the vertical
  profile of water isotopes in vapor.
• But minimum value too low--first guess need
  more condensate in CAM2 upper tropopause,
  oxidation of methane (?)

Jung-Eun Lee and Inez Fung
9
CCM3 prototype
David Noone
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What BGCWG (and other working groups) can do

• Identify isotopes in the model as a priority to
  the CCSM so that resources are allocated to
  implement and support the codes.

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New areas

• Iron cycle (atmosphere (Mahowald) and ocean
  (Moore))
• Nitrogen cycleland (Thornton) and atmosphere
  (Lamarque/Hess)
• Sulfur cycle--? (atmosphere ready, ocean?)
• River biogeochemistry
• Coastal biogeochemistry
• Ocean Sediment model
• Isotopes
• Fires
• Phosphate (no need to couple?)