Variability in the ocean - from modewater biogeochemistry to SST

1
Variability in the ocean - from modewater
biogeochemistry to SST

• Holger Brix
• UCLA, JIFRESSE and Dept. of Atmospheric and
  Oceanic Sciences
• JPL, 16 September 2008

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Acknowledgements

• Curtis Deutsch, UCLA
• Nicolas Gruber, ETH, Zürich
• Scott Doney, Ivan Lima, WHOI
• Crews and scientists of NOAA, UH, BBSR, and other
  research vessels
• Dimitris Menemenlis, JPL

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Outline

• Mode water biogeochemistry
• Global Carbon Cycle Perturbations
• Carbon and the Ocean
• Why mode waters (and what are they anyway)?
• Mode water variability - time-scales and places
• Modeling the gaps
• Sea surface temperatures and heat flux
  variability in ECCO2 and beyond

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Outline

• Mode water biogeochemistry
• Global Carbon Cycle Perturbations
• Carbon and the Ocean
• Why mode waters (and what are they anyway)?
• Mode water variability - time-scales and places
• Modeling the gaps
• Sea surface temperatures and heat flux
  variability in ECCO2 and beyond

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The Global Carbon Cycle
Sarmiento Gruber, 2002
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Perturbation of Global Carbon Budget (1850-2006)
2000-2006
deforestation
Source
tropics
extra-tropics
1.5
CO2 flux (Pg C y-1)
Sink
Time (y)
Le Quéré, unpublished Canadell et al. 2007, PNAS
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Perturbation of Global Carbon Budget (1850-2006)
2000-2006
fossil fuel emissions
7.6
Source
deforestation
1.5
CO2 flux (Pg C y-1)
Sink
Time (y)
Le Quéré, unpublished Canadell et al. 2007, PNAS
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Perturbation of Global Carbon Budget (1850-2006)
2000-2006
fossil fuel emissions
7.6
Source
deforestation
1.5
CO2 flux (Pg C y-1)
Sink
Time (y)
Le Quéré, unpublished Canadell et al. 2007, PNAS
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Perturbation of Global Carbon Budget (1850-2006)
2000-2006
fossil fuel emissions
7.6
Source
deforestation
1.5
CO2 flux (Pg C y-1)
atmospheric CO2
4.1
Sink
Time (y)
Le Quéré, unpublished Canadell et al. 2007, PNAS
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Perturbation of Global Carbon Budget (1850-2006)
2000-2006
fossil fuel emissions
7.6
Source
deforestation
1.5
CO2 flux (Pg C y-1)
atmospheric CO2
4.1
Sink
ocean
2.2
Time (y)
Le Quéré, unpublished Canadell et al. 2007, PNAS
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Perturbation of Global Carbon Budget (1850-2006)
2000-2006
fossil fuel emissions
7.6
Source
deforestation
1.5
CO2 flux (Pg C y-1)
atmospheric CO2
4.1
Sink
land
2.8
ocean
2.2
Time (y)
Le Quéré, unpublished Canadell et al. 2007, PNAS
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Outline

• Mode water biogeochemistry
• Global Carbon Cycle Perturbations
• Carbon and the Ocean
• Why mode waters (and what are they anyway)?
• Mode water variability - time-scales and places
• Modeling the gaps
• Sea surface temperatures and heat flux
  variability in ECCO2 and beyond

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Sea-air CO2 Flux
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The Biogeochemical loop
N. Gruber, 2002
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Marine Phytoplankton
From top left Diatoms, Radiolaria,
Dinoflagellates
http//www.amonline.net.au/exhibitions/beyond/phyt
oplnkton/
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The Biogeochemical loop
Production
Export
N. Gruber, 2002
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Production, Respiration, Export

Photosynthesis Net Primary Production (NPP)
Corg
CO2
NPP
Phytopl.
Bacteria
Zoopl.
Rh
Export Production
Respiration (Heterotrophic)
Net Community Production NCP NPP - Rh
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The Biogeochemical loop
Production
NPP
Export (NCP)
N. Gruber, 2002
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NPP-NCP-POC at HOT(Hawaii Ocean Time-Series)
Brix et al., 2006
POC Particulate Organic Carbon
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Spatial patterns in ?pCO2 due to biology and
temperature are also mostly opposing each other!
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Anthropogenic CO2
Gruber (2002)
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Outline

• Mode water biogeochemistry
• Global Carbon Cycle Perturbations
• Carbon and the Ocean
• Why mode waters (and what are they anyway)?
• Mode water variability - time-scales and places
• Modeling the gaps
• Sea surface temperatures and heat flux
  variability in ECCO2 and beyond

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The Ocean Conveyor
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Surface density, isopycnal outcrops
Waters will move mostly along surfaces of
constant density.
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What Are Mode Waters? Definitions after Hanawa
and Talley (2001)

• Homogeneity of water properties (such as
  temperature, salinity, oxygen)
• Thickening of isopycnal layer - substantial
  volume
• At a single vertical profile, mode water appears
  as low vertical density gradient (pycnostad)
  between high gradients (seasonal and main
  pycnocline)
• Mode water is found well beyond its outcropping
  areas as a result of advection
• Formation or maintenance usually associated with
  wintertime convective mixing

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Mode Waters Example 18o Mode Water
Subtropical Mode Water (STMW) in the North
Atlantic
Potential Temperature ?
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Why are we interested in Mode Waters?

• Mode waters can take up anthropogenic CO2 and
  hide it from the atmosphere (buffer capacity)
• After a time delay (years to decades) mode waters
  re-emerge at (possibly distant) regions

And where do we find them?

• In all ocean basins
• Descending on isopycnals from outcrop regions

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Mode Waters
Talley, 1999
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Intermediate Waters
LSW
NPIW
AAIW
Talley, 1999
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Outline

• Mode water biogeochemistry
• Global Carbon Cycle Perturbations
• Carbon and the Ocean
• Why mode waters (and what are they anyway)?
• Mode water variability - time-scales and places
• Modeling the gaps
• Sea surface temperatures and heat flux
  variability in ECCO2 and beyond

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U.S. JGOFS Time-series Sites
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DIC at BATS (Bermuda)
Bates et al., 2001
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Chlorophyll in the NAtl.
Lévy, 2005 Palter et al., 2005
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Apparent Oxygen Utilization
AOU O2,SAT - O2 (measure of respiration)
Figure prepared by Niki Gruber
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AAIW
MED
SPMW
LAB
NADW
AOU O2sat - O2
APPARENT OXYGEN UTILIZATION
STMW
SPMW
AAIW
MED
Johnson Gruber, Prog. Oceanography, 2007
LAB
NADW
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AOU CHANGES 2003-1993
Johnson Gruber, Prog. Oceanography, 2007
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AOU AND DIC CHANGES 2003-1993
Expected change from anthropogenic CO2
max 0-8 mmol/kg
Johnson Gruber, Prog. Oceanography, 2007
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O2 anomaly at HOT (Hawaii)
Deutsch, 2006
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Observed AOU differences North Pacific
Deutsch et al. (2006)
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Outline

• Mode water biogeochemistry
• Global Carbon Cycle Perturbations
• Carbon and the Ocean
• Why mode waters (and what are they anyway)?
• Mode water variability - time-scales and places
• Modeling the gaps
• Sea surface temperatures and heat flux
  variability in ECCO2 and beyond

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Case study IThe North Pacific
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Modeled AOU differences North Pacific
Deutsch et al. (2006)
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Surface CO2 Flux Variance
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Components of Variability
Changes in AOU can be decomposed into
components ?AOU ?AOUbiol ?AOUvent
?AOUcirc Using Multiple simulations with
climatological OUR (OUR dAOU/dt) and/or
preformed climatological AOU fields
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O2 change, 1990s-1980s, ? 26.6Deutsch et al.
(2006)
Total
Circulation
Ventilation
Biology
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Origin of O2 anomalies1990s - 1980s
a,b ventilation c,d circulation a,d decadal
trends b,c interannual perturbations
a
b
c
d
Deutsch et al. (2006)
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Case study IIThe North Atlantic
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A16N Repeat Hydrography
Apparent Oxygen Utilization (AOU) AOU O2,SAT -
O2 (measure of respiration)
?AOU 2003 - 1993
Mean 40o-60oN
Johnson Gruber, Prog. Oceanography, 2007
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Modeled AOU (standard deviation)
UCLA CCSM model runs
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Components of Variability
Changes in AOU can be decomposed into
components ?AOU ?AOUbiol ?AOUvent
?AOUcirc Using A single simulation
analyzing nutrient concentrations and the
(de-)coupling of C and O2
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Components of Variability
Changes in AOU can be decomposed into
components ?AOU ?AOUbiol
?AOUventAOUcirc ?AOUbiol can be approximated
using a constant stochiometic O2PO4 ratio ?AOU
rO2PO4 ?PO4 ?AOU ?AOU can
be analyzed using the (de-)coupling of C and O2
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?AOUrO2PO4?PO4?AOU
Total Biology
Physics
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Components of Variability
Biology / Physics
Correlation DIC-AOU
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Modewater Observations and Modeling

• Mode and Intermediate Waters are hotspots of
  oxygen, carbon and nutrient variability in
  mid-latitudes
• Formation regions of these Mode Waters also show
  substantial surface variability
• Analyses of components of biogeochemical
  variability require either
• Multiple model simulations
• Multi-tracer correlations

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Outline

• Mode water biogeochemistry
• Global Carbon Cycle Perturbations
• Carbon and the Ocean
• Why mode waters (and what are they anyway)?
• Mode water variability - time-scales and places
• Modeling the gaps
• Sea surface temperatures and heat flux
  variability in ECCO2 and beyond

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SST variability in ECCO2 and beyond.
ECCO2 AVHRR-AMSRE ROMS
model satellite data
model
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SST variability in ECCO2 and beyond.
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Mixed layer heat budget governs SST
This project will investigate the components of
mixed layer heat budget and its associated errors
as a function of region, spatial scale, and
frequency.
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Thank you!!!