Manfredi Manizza1 M. J. Follows1, S. Dutkiewicz1, C. N. Hill1
Towards Modeling The Carbon Cycle of the Arctic Ocean
1EAPS-MIT, Cambridge, MA2Jet Propulsion Laboratory, Pasadena, CA
3U. Texas at Austin, Port Aransas, TX4Marine Biological Laboratory, Woods Hole, MA
D. Menemenlis 2, J. W. McClelland 3, B. J. Peterson4
TALK OUTLINE
1) The Arctic Ocean Carbon Cycle (AOCC)
2) A role for riverine DOC in the AOCC
3) Transport, Fate & Lifetime of riverine DOC inthe Arctic Ocean: Model-Data comparison.
4) Conclusions
Arctic Ocean Carbon Cycle
ATMOSPHERE
CO2 Fluxes
Primary Production
= 0.4 PgC yr-1 PhytoplanktonShel
f
Coas
t
LandBiospher
e
Surface Ocean
Deep Ocean
CO2
ORGANICCARBONEXPORT
RiversSea Ice
DOC
RiverineDOC flux = 0.25
PgC yr-1
Approach of “Data-Model Fusion”
1) Realistic riverine DOC flux from land to ocean.
2) Realistic representation of Large Scale Ocean Circulation in the Arctic basin.
3) Proper time scale regulating the rate of decay for riverine DOC while in the ocean .
1- Riverine Discharge of DOC in the Arctic
From Lammers et al., JGR 20013754 Hydro-stations
RunoffClimatology
DOCdata fromTownsend
McClellandPeterson
Pan-Arctic DOC Riverine Flux
Large seasonal Cycle of River RunOff peaking in June
0
3.5
Time (months)
Eurasian Load > North-American Load
1011molC month-1
Regional Arctic Set-up of MITgcm
1 - Regional version of MITgcm (cubed sphere) for theArctic domain with open boundary conditions.
2 - Eddy-resolving (~20 Km), using 1992-2001 NCEPAtmospheric Forcing - 3 repeated simulated decades.
3 - ON-LINE version of MITgcm for tracer transportand marine biogeochemical processes (carbon cycle).
4 - This study: ARCTIC OCEAN CIRCULATION and PASSIVE & DECAYING TRACER simulating transport and fate of riverine DOC.
2) - Large Scale Circulation of the Arctic Ocean
Surface flow (0-200 m)
(Figure from Rudels, 2006)
Slide 9
Regional Arctic MITgcm
Surface Salinity & Surface velocity
38 24
Riverine Fluxes & Ocean Dynamics
MacKenzie
Eastern Arctic (EA)
Greenland
[Passive Tracer] & Surface velocity
(Units : microM)
1) Atlantic Waters : Low [TRC]
2) EA Coastal Waters : High [TRC]
3) Pacific Waters : Low [TRC]
30th simulated year - annual mean
0
100
4) WA Coastal Waters : High [TRC] (I) Evident link between :Location of riverine tracer fluxes
Ocean circulation patterns
Western Arctic (WA)
(II) Strong haline gradients set the differences in both water masses and
[trc] distributions
Cross-Shelf Transport, Mixing, and Decay of DOC
DOC(decaying
tracer)
Salinity (passive tracer)
Mixing Line
Coastal Waters (Higher DOC & Lower Salinity)
Open-Ocean Waters(Lower DOC & Higher
Salinity )
can impact mixing line. Hansell et al. 2004
Salinity
Black Dots = Western ArcticWhite Dots = Eastern Arctic
= Decay time scale of Tracer
Data-Model Comparison (I)
500
250
0
500
0
250Western Arctic Eastern Arctic
Without any decayTracer values too high !!
With 5 years decayLower Tracer values
BUT values OFFSET = 5 years
= 0
Manizza et al., in prep
Data-Model Comparison (II)
DOCtotal = DOCriver+ DOCin-situ
DOCin-situ ~ 50 microM
(Anderson , 2002)Eastern Arctic Western Arctic
500
250
0
CONCLUSIONS
1 - Regional Ocean Model (MITgcm) captures main ocean circulation features and water masses distribution in the Arctic Ocean.
3 - This study will help to constrain the carbon transfer for DOC to DIC pool to correctly estimate air-sea CO2 fluxes at basin scale.
2 - Model-data fusion is a robust approach and it’s reliable as benchmark for testing data-based hypotheses.
Assessing Lifetime of Riverine DOC
Circulation Only
∂C/∂t = Adv. + Diff.
∂C/∂t = Adv. + Diff. - C
= 1/ = Decay Time Scale
= 1 - 10 years (5 years example)
C = Idealized Tracer
Circulation +
Decay
Passive Tracer
Decaying Tracer