Nick Stephens Greencycles Mid-Term Review meeting 21/02/2007 1/18 Ocean Biogeochemistry Nicholas...

Nick Stephens Greencycles Mid-Term Review meeting 21/02/2007 1/18

Ocean Biogeochemistry

Nicholas Stephens

Max-Planck-Institut für Biogeochemie, Jena


Aims of present studies

• Synthesise current understanding/ experimental findings

– N2 and N cycle

– Associated biology

– Ocean processes

• Decoupling of N:P


Aims of present studies

• DGOP goal is to build global biogeochemistry models based on PFT’s

• Understand and quantify the feedbacks between marine ecosystems and climate


The role of biology

• Resulting C fluxes and DIC concentrations are affected by photoautotrophic C fixation

• C fixation and the contribution to export is a function of community structure and physiology

• Growth is regulated by availability of other nutrients (DIN, PO4, Fe), and physical variables such as temp


Ocean-atmosphere carbon fluxes

IPCC, third assessment

Nitrogenfixation


Effects on biogeochemical cycles


Present model: PlankTOM6.0DIN SiFePO4

DiatomsN2 fixersCalcifiersNanophyto plankton

Mesozoo-plankton

Microzoo-plankton

Bacterial

remineralisation

Light

NO3 (mol L-1)

0 5 10 15 20

Gro

wth

Ra

te

(d-1)

0.0

0.1

0.2

0.3

0.4

0.5

0.6 Silicifier

Calcifier

N2 fixer

Mixed


Limitation of growth due to NO3

PO4 (mol L-1)

0.00 0.05 0.10 0.15 0.20 0.25

Gro

wth

Ra

te

(d-1

)

0.0

0.1

0.2

0.3

0.4

0.5Silicifier

Calcifier

N2 fixer

Mixed


Limitation of growth due to PO4

Temperature (oC)

0 10 20 30 40

Nor

mal

ised

rat

e of

gro

wth

(d-1

)

0.0

0.2

0.4

0.6

0.8

1.0

1.2PlankTOM9.0

=maxEXP(-((T-Topt)4/(Twidth)

4)

Schoemann et al. 2005


Carpenter et al. 2004

La Roche and Breitbarth, 2005

Staal et al. 2003

Temperature relationship of N2-fixing PFT

strategy for forced atmospheric conditions


µmolC L-1

Calcifiers N2 fixers

Mixed Phytoplankton Silicifiers


Results for a PlankTOM6.0 2005 October simulation

N2 fixed = 0.171 PgN yr-1, Primary Productivity = 71.08 PgC yr-1, Export to 100m = 13.05 PgC yr-1


µmolC L-1

Simulated monthly mean N2 fixer concentration, April 2005


Comparison to remote sensing information

Westberry et al. 2006

Nick Stephens Greencycles Mid-Term Review meeting 21/02/2007 15a/18

The Working Group on Coupled Modelling (CLIVAR/WCRP) took place in September 2006.

This working group guides the development of the Coupled Models which are used by hundreds of scientists to project the future state of climate, and evaluate those projections (e.g. the IPCC

model archive).

Here is a brief report of the state of the carbon cycle presented by Corinne Le Quéré during the

September meeting. Full version available at [email protected]

Nick Stephens Greencycles Mid-Term Review meeting 21/02/2007 15b/18

Ongoing model developments

On land:

• fires• land use

• CH4 cycle

• N cycle• more advance ecosystem dynamics (including competition and succession)

Unresolved issues:

• importance of CO2 fertilisation

• importance of forest regrowth• temperature dependence of soil respiration

•CH4 budget

In the oceans:

• more advanced ecosystem dynamics (incl. grazers and incl. major efforts on biological data synthesis)• relaxation of N/P ratio and quota models• coastal ocean dynamics (over years)• links with higher trophic levels

Unresolved issues:

• importance of ecosystem dynamics• impact of ocean acidification on ecosystems • impact of recent changes in ocean physics and temperature (including on respiration)

Nick Stephens Greencycles Mid-Term Review meeting 21/02/2007 15c/18

Issues for model inter-comparison (C4MIP):

• fragmented understanding of the processes• limited observations for validation• incomplete models, thus they should not be expected to reproduce observation (e.g. no fires, no land use)• no financial support for C4MIP activities• no standards• no shared 3D fields• no archiving strategy

Issues on the C-Cycle

• C-cycle - climate feedbacks will increase before they are constrained

• C-cycle – CO2 feedbacks will increase before they are constrained

• C-cycle - climate feedbacks are highly dependent on the water cycle

• standards and archiving of C-cycle variables not organized


Present activities • Stephens N. and Flynn KJ. in prep. “Nitrogen-status of

Gloeothece sp. cells reflects growth supported by different inorganic nitrogen sources”

• Stephens N. et al. in prep “Including N2 fixation as a Plankton Functional Type in a Dynamic Green Ocean Model”

• Stephens N. in prep. “Nitrogen fixation and inorganic nitrogen assimilation in the cyanobacterium Trichodesmium spp. can be described using a mathematical model.

• Allen et al. in prep. “Evaluating and validating Plankton Functional Type models” as part of a recent AMEMR workshop


Future plans

• Preparation of the PlankTOM10.0 model for coupling to the QUEST coupled model

• Preparation of the PlankTOM10.0 model for publication • Investigating the response of the nitrogen cycle and implications

for climate due to changing physical conditions


Acknowledgements

• Corinne Le Quéré, Erik Buitenhuis and members of the Green Ocean Project

• Greencycles Project• Marie Curie Actions• MPI-BGC, Jena• UEA

Dus

t dep

osit

ion

(μm

ol N

kg-1

mon

th-1

)

World Ocean Atlas 2001

Bergman, botan website

Trichodesmium erythraeum

Mea

n N

:P (

μmol

N k

g-1/μ

mol

P k

g-1)


16

DIN Phyto-uptake

Leakage/lysis

Remineralisation

Diatom-uptake

Regulation of N2 fixation

Cocco-uptake

Physical processes

N 2 fix

/uptake

N2 fixer Sedimentation

DIN

PO4

Decay

Fe

N2

Heterotrophy

O 2

Summary

• Significance of biogeochemical processes and feedbacks

• N cycle leads to better representation of fluxes of C

• N2 fixation needs a relationship to N

• Denitrification requires more substantial relationship to P

latest developments are done with NEMO, running on a linux cluster at the Univ. of East Anglia

some developments done with OPA8.1, running on the German DKRZ super-computer

we do mostly interannual simulations with NCEP forcing

we focus on CO2, O2, and marine ecosystems

large parallel data synthesis

phyto-plankton

mixed

silicifiers

zoo-plankton

proto

meso

PlSCES-T

• limitation by Fe, P, and Si

• Meso-zooplankton parameterisation based on global data compilation (difference to Olivier Aumont's PISCES model)

phyto-plankton

calcifiers

mixed

silicifiers

zoo-plankton

proto

meso

PlankTOM 5

• limitation by Fe, P, and Si

• Meso-zooplankton parameterisation based on global data compilation

• Micro-zooplankton parameterisation based on global data compilation (work with Richard Rivkin)

• Ballast effect based on Stokes law

• adjusted grazing preferences

pico-heterotrophsbacteria

phyto-plankton

pico-autotrophs

N2-fixers

calcifiers

DMS-producers

mixed

silicifiers

zoo-plankton

proto

meso

PlankTOM 9 (under

development)

pico-heterotrophsbacteria

phyto-plankton

pico-autotrophs

N2-fixers

calcifiers

DMS-producers

mixed

silicifiers

zoo-plankton

proto

meso

macro

PlankTOM 10 (planned for 2007)

N2 fixed = 0.171 PgN yr-1, Primary Productivity = 96.60 PgC yr-1, Export to 100m depth = 16.27 PgC yr-1

PlankTOM 6.0 simulation for 1st October 2005

N2 fixers

Mixed phytoplankton

Diatoms

Coccolithophores

Projection of atmospheric CO2 up to 2060

anomalies in atmospheric forcing

north

equator

south

Temperature (oC)

Precipitations (m yr-

1)zonal wind stress (N m-

2)

model projection of climate change in 2060

temperature

ice cover

mixed layer depth

change in the CO2 sink in 2060 (mol/m2/y)

Calcifiers

PO

4

Fe

PlankTOM

PISCES-T

Laurent’s thesis

-30 % +30 %

Comparison to results from the thesis of Laurent Boppexport production at 100 m for 2xCO2

PISCES-T

PlankTOM-5

Prototype of the PlankTOM 10 Dynamic Green Ocean Model

pico-heterotrophsHeterotrophic bacteria and

Archaea

phyto-plankton

pico-autotrophs

N2-fixers

calcifiers

DMSp-producers

mixed

silicifiers

zoo-plankton

proto

meso

macro

10 Plankton Functional Types (PFTs) selected for

(a) their explicit biogeochemical role,

(b) quantitative importance in at least one region of the ocean,

(c) a distinct set of environmental and nutrient requirements for productivity,

(d) a distinct impact on the rest of the community (e.g. composition).

Other DGOMs under construction with similar (but not identical) choices of PFTs:

1. ERSEM global (M. Vichi, I. Allen)

2. PISCES + (O. Aumont)

3. NEMURO (Y. Yamanaka)

4. BEC (K. Moore + S. Doney)

5. Hamocc5 (E. Maier-Reimer)

6. Gregg (W. Gregg et al.)

bacteria

phytoplankton zooplankton

pico-hetero.

pico-autotr.

N2-fix. calcifiers

DMS-prod.

mixed-phyto

silicifiers

proto meso macro

rates x

data available for parameterisation

phytoplankton growth

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 5 10 15 20 25 30

T [°C]

µ [

1/d

]

model

phaeo

dia

ehux

pico

n2

Based on IRONAGES results (C. Lancelot et al.)

meso-zooplankton growth

Buitenhuis et al., 2006

bacteria


pico-hetero.

pico-autotr.

N2-fix. calcifiers

DMS-prod.

mixed-phyto

silicifiers

proto meso macro

rates x

data available for parameterisation

Even where an abundance of data exists does not necessarily imply well constrained parameters

bacteria


pico-hetero.

pico-autotr.

N2-fix. calcifiers

DMS-prod.

mixed-phyto

silicifiers

proto meso macro

rates xbiomass

satellite

geochem.

data available for parameterisation and evaluation

bacteria


pico-hetero.

pico-autotr.

N2-fix. calcifiers

DMS-prod.

mixed-phyto

silicifiers

proto meso macro

rates xbiomass x # x # x # # x xsatellite

geochem.


• The only exhaustive (>5000 points) insitu database of biomass concentration exists for meso-zooplankton. Efforts are underway for a similar database on proto-zooplankton

• Gregg et al. have a database on percent distribution of ~500 data points

• The EU euroceans project has some funding for building a data base of PFT concentration before 2009, but it is not clear how much effort is needed.

bacteria


pico-hetero.

pico-autotr.

N2-fix. calcifiers

DMS-prod.

mixed-phyto

silicifiers

proto meso macro


geochem.


Mesozooplankton biomass

(µmol C L-1)

bacteria


pico-hetero.

pico-autotr.

N2-fix. calcifiers

DMS-prod.

mixed-phyto

silicifiers

proto meso macro


geochem.


• A few algorithms can detect phyto-PFT from space (but they also need evaluation)

PHYSAT PFTs (January 98-05 synthesis map)

Alvain et al., 2005

bacteria


pico-hetero.

pico-autotr.

N2-fix. calcifiers

DMS-prod.

mixed-phyto

silicifiers

proto meso macro


geochem. x x x x


• geochemical data can be used to assess that the sum of the processes is correct (e.g. biological, chemical, and physical). The data include concentrations of DIC, TALK, Si, PO4, NO3 and O2.

bacteria


pico-hetero.

pico-autotr.

N2-fix. calcifiers

DMS-prod.

mixed-phyto

silicifiers

proto meso macro


geochem. x x x x


the absolute top priority to evaluate DGOMs is to fill this table

Especially biomass

Time (h)

L10 DO D2 D4 D6 D8 D10 L0 L2

N:C

(N

C-1

)

0.00

0.15

0.20

0.25

0.30a)

N2

NO3-

NH4+

Stephens, unpublished

N:C calculations for batch cultures of Gloeothece

Estimates for pelagic N2 fixation

• N2 fixation ~100-200 Tg N yr-1 (Sarmiento and Gruber, 1997)

• Denitrification estimated ~450 Tg N yr-1

• Capone et al. 2005 estimates for N2 fixation in the N Atlantic are 3-4 times Sarmiento and Gruber (1997) estimates for same region

• Short residence times of N (<3000 yr) have potential for substantial change in N inventory

• N2 fixation is part of a very dynamic ocean N cycle

Method Used

Area Considered km2 ×106

Integrated Annual N2 fixation, mol N ×1012 Reference

Direct 17.8-28.0 1.6-2.4 Capone et al., 2005

Extrapolated 7-19 2-25 Carpenter and Romans, 1991

Extrapolated 7-19 1.1 Lipschulz and Owens, 1996

Geochemical 7-19 3.7-6.4 Michaels et al. 1996

Geochemical 28 2.0 Gruber and Sarmiento, 1997

Geochemical 49 2.0 Lee et al., 2002

Geochemical 20-30 2.0 Lee et al., 2002

Geochemical 6.1 0.15-0.46 Hansell et al., 2004

Geochemical 17.8-28.0 5.5-8.7 Capone et al., 2005

5.5 – 8.7 T mol N yr-1 = 77 – 121.8 T gN yr-1

C:N = 4.7 – 7.3 for Trichodesmium

361.9 - 889.14 T gC yr-1

•just for a 28 M km2 area of the N Atlantic!•Considering only Trichodesmium

•Estimates for new N considered conservative

Estimates for pelagic N2 fixation based fluxes per area in the Atlantic Ocean

Capone, 2005; Sarmiento and Gruber, 1997; La Roche and Breitbarth, 2005

Mea

n N

:P (

μmol

N k

g-1/μ

mol

P k

g-1)


Moutin et al. 2005

Letelier and Karl, 2005

Capone et al. 2005

Fu et al. 2005

16

AMT

Richelia intracellularis

Gomez et al. 2005

Rhizosolenia clevei

Gomez et al. 2005

Chaetoceros compressus

Gomez et al. 2005

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