Download For Internet Explorer user, click here to view a Powerpoint Diaporama

Modelling some Southern Ocean
biogeochemical paradox
or How S.O. response to global change ?
or How bad we understand the S.O. ?
P. Monfray (IPSL, Paris)
Acknowledgments: L.Bopp, O.Aumont, C.Le Quéré
& J.Orr
Prepared for JGOFS-SOSG, Hawaï,
February 16th, 2002
According to national copyright laws, the formal
permission of the author ([email protected])
is requested before copying any of this document.
Please see the last transparent for
the list of references;
Friedlingstein et al., 2001
Dufresne et al., 2002
PISCES
Aumont et
al., 2001
A- External Geochemical Impact
Do dust change could affect the SO ?
Diatoms change (%)
X 100
Bopp L., 2001
Export Production Change
• Export Production +6 %
• But gyres increases … and PP decreases
Bopp L., 2001
Aumont et al.,
2001
>>> Be careful with iron geo-engineering…
diatoms should reduce surface primary production, food quality
and marine resources
Bopp L., 2001
Do Si change could affect the SO ?
Fe (Mahowald, 1999)
+ Si (Tréguer et al., 2000) ?
But effect negligible in PISCES-OPA model
Is it correct?
Nutrient co-limitation
Diatoms
Do the model too limited by Fe and not enough by Si?
Relative Si co-limitation to Fe co-limitations is a key stone for
SO response…
Data ?
Aumont et
al., 2001
Do [CO2]d change could affect the SO ?
In Eq.Pac, a jump from 0.5 to 2 x CO2 advantages diatoms
proportion by a factor 2 (Tortell et al., OSC, 2002)
What about taxonomic response to CO2 in S.O. ???
At LGM, this effect have opposite effect than Fe and Si
What about the future ???
B- Climate Impact
Do stratification change could affect the
SO ?
Climate impact on
ocean physics at
2xCO2
Major Stratification
Bopp et al., 2001
Export production change at 2xCO2
Simulation P3ZD-OPA-LMD
30 gC m-2 an -1
Moyenne
Zonale
(2xCO2-1xCO2)
-30 %
- 30 gC m-2 an -1
+30 %
• Global diminution of -5 to -10 %
• But opposition between low latitudes (-20%) / high latitudes (+20%)
• Robust for different biological or physical models
Bopp L., 2001
Shift from Diatom to Nanoplankton at 2xCO2
Nanoplanktons
Diatoms
Bopp L., 2001
Do grazing could play a role ?
Export change under stratification in North-Pacific
Nutrient limitation case
(HAMOCC3)
Grazing control case
( P3ZD)
2xCO2 < 1xCO2
2xCO2 > 1xCO2
60
Seasonal Cycle
at 1xCO2
at 2xCO2
Export
gC m-2 y-1
120
0
Jan
Dec
What about S.O. ?
0
Jan
Dec
Bopp L., 2001
Combining climate and external
geochemical impacts
The paleo-productivity challenge
Export Production Change at
LGM
Increase in whole Austral Ocean
Bopp L., 2001
Export Production at LGM
Data
Modelling
Dust
+ Circulation
+ SST
+ Sea-ice
LGM < Present
LGM ~ Present
LGM > Present
Ambiguous
From K.E. Kohfeld’s compilation
(proxies : C-org, CaCO3, Ba, assemblages…)
/
PISCES-OPA simulation
(Export, LGM-Present, gC m-2 y-1)
Bopp et al., 2002b
Do UV change could affect the SO ?
Important in lab experiment, but repair processes
Who knows at local, regional or bassin scale ?
C- Impact of SO on atmospheric
chemistry
Do SO change could impact
atmospheric CO2 ?
Anthropogenic CO2
fluxes at 700m
The S.O.: a priori the
main CO2 regulator
But efficiency could be
half by stratification
change
Physical change is the
main uncertainty
Bopp L., 2001
Do SO change could impact DMS ?
Potential impact on
DMS cycle
Speciation change is the
main uncertainty
Phaeocystis ?
2xCO2 - 1xCO2
Aumont et al., 2002
Bopp et al., 2002
D- How to improve our knowledge on
present change and response ?
Do Antarctic Circumpolar Waves (ACW) could
be used as a climate change experiment ?
• ACW
SST: ± 1°C
MLD: ± 50m
Biological response: 1-2 wk
Geochemical response: 1 yr
• 2CO2 climate
SST: 0.5-2°C
MLD: 30-100m
Biological response: 1-2 wk
Geochemical response: 1-10 yr ?
Austral Ocean (45°S-60°S)
SST
No simple relationship between
stratification (SSH) and Chl
SSH
Chl
Le Quéré et al.,, 2001
East-West Dependence
Le Quéré et al.,, 2001
Stratification increases Chl:
light nutrient limitation ?
Stratification reduces Chl:
deep nutrient limitation ?
Le Quéré et al.,, 2001
Do O2 could be used as a climate change
diagnostic ?
Flux d ’O2 (mol m-2 an-1)
Oxygen outgassing due to climate change
Stratification
Effet
Thermique
Années
Bopp et al.,, 2001b
 Diminution of dissolved oxygen due to climate change.
0
1000
2000
Années
3000
Bopp et al.,, 2001b
S.O. Global Change
A provocative summary-1
A- External Geochemical Impact
• Do dust change could affect the SO:
 Role of Fe from continental margins ?
• Do Si change could affect the SO:
• Do [CO2]d change could affect the SO:
 Response of diverse planktonic assemblages ?
Paleo: ++,
Futur: +?
Paleo: +?
Paleo: +?,
Futur: - ?
Futur: ++?
B- Climate Impact
• Do stratification change could affect the SO geochemistry: Paleo: ++?,
Futur: +++?
• Do stratification change could affect the SO biology: Paleo: ++?,
Futur: +++?
 Responses of taxonomic groups and grazing to stratification (light) and
temperature increases? To sea-ice change?
S.O. Global Change
A provocative summary-2
C- Feedback on atmospheric chemistry
• CO2: SO a key stone for uptake BUT need better physics and dynamics
• DMS: Potential impact on clouds BUT need speciation dynamics
D- How to improve our knowledge on present change and response ?
• Use ACW as a climate change experiment for biology
 Need in depth analysis, both spatial and time patterns, of joint satellite
surveys (Chl, SST, SSH, etc)
• Use O2 (or other proxy) as an imprint of convection/climate variability and change
 Need data mining
 Need to setup new JGOFS or ARGO long time surveys
• Develop lab experiments to evaluate biological responses to dissolved CO2
 Need diverse planktonic assemblages, but how to jump in open condition?
• Determine role of the relative Fe sources (margins, atmospheric, oceanic)
 Need to study some key areas dominated by one main source (South blue
Pacific, Kerguelen plume) or various sources (South Atlantic)
• Others ?
References
•
•
•
•
•
•
•
•
•
•
Aumont, O., Belviso, S. and Monfray, P.. DMSP and DMS sea surface distributions simulated
from a global 3-D ocean carbon cycle model, J. Geophys. Res., in press, 2002.
Aumont O. , E. Maier-Reimer, Blain S. and Monfray P., An ecosystem model of the global ocean
including Fe, Si, P co-limitations, Global Biogeochemical Cycles, submitted, 2001.
Bopp, Climate changes and marine biogeochemistry, modelling LGM and industrial era, Thesis,
University of Paris VI, 318 pp, 2001.
Bopp L., P. Monfray, O. Aumont, J-L. Dufresne, H. LeTreut, G. Madec, L. Terray, et J.C. Orr,
Potential impact of climate change on marine export production, Global Biogeochemical Cycles,
15, 81-99, 2001
Bopp L., O. Aumont, S. Belviso et P. Monfray, Potential impact of climate change on marine DMS
(dimethylsulfide) emissions, Tellus, in revision, 2002.
Bopp L., C. LeQuéré, A.C. Manning, M. Heimann et P. Monfray,Climate-induced oceanic oxygen
fluxes: Implications for the contemporary carbon budget, Global Biogeochemical Cycles, in
press, 2001b
Bopp L., K.E. Kohfeld, C. Le Quéré, O. Aumont, O. Marti, I. Tegen, S.P. Harrison and I.C.
Prentice, Dust impact on marine biota and atmospheric pCO2 during glacial periods,
Paleoceanography ,submitted, 2002b
Dufresne J.L., P. Friedlingstein, M. Berthelot, Bopp L., P. Ciais, L Fairhead, H. Le Treut et P.
Monfray, On the magnitude of positive feedback between future climate change and the carbon
cycle, Geophysical Research Letters, in press, 2002.
Friedlingstein P., Bopp L., P. Ciais, J-L. Dufresne, L. Fairhead, H. LeTreut, P. Monfray and J.C.
Orr, Positive feedback of the carbon cycle on future climate change, Geophysical Research
Letters, 28, 1543-1546, 2001.
Le Quéré C., Bopp L. et I. Tegen, Antarctic Circumpolar Wave impact on marine biology,
Geophysical Research Letters, submitted, 2001.