Surface Ocean CO2 Variability and Vulnerabilities

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Surface Ocean CO2 Variability and Vulnerabilities
April 11-14 2007 IOC/UNESCO, Paris
Interannual and Decadal Variability of Air-Sea
CO2 Fluxes in the Equatorial and South Pacific
Oceans Richard A. Feely, Taro Takahashi, Rik
Wanninkhof, Catherine E. Cosca, Chris Sabine,
Stewart Sutherland, and Mary-Elana Carr
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Outline

• Background on Interannual Variability of CO2 in
  the
• Atmosphere and Oceans

• Comparisons of Estimates of CO2 Sources and
  Sinks
• from Observations and Models for the Equatorial
  and South Pacific Ocean

• Conclusions

Richard A. Feely, Taro Takahashi, Rik
Wanninkhof, Catherine E. Cosca, Chris Sabine,
Stewart Sutherland, and Mary-Elana Carr
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CO2 Emissions and Atmospheric Growth Rate
General Trends
Slowdown in CO2 growth rate before an El Niño
event Enhancement of CO2 growth rate once an El
Niño is underway.
Land Ocean Uptake
Atmospheric Increase
Question What is the variability of the CO2 flux
from the oceans?
From Hibbard et al. (2001)
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International surface pCO2 observations
from volunteer observing ships and time series
moorings
Moorings
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Climate Observations and Services Program
Surface water pCO2 Measurements from Ships
KaImimoana
Columbus Waikato/Cap Victor
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Empirical Approach Creation of Flux Maps

• Obtain data from ships (and other platforms)
• Create regional algorithms with biogeochemical
  and physical parameters that are
• measured at higher frequency and with
  regional coverage
• Use high data coverage to create flux maps that
  captures spatial and temporal variability

Remotely sensed products used Q-Scat Wind for
gas transfer Reynolds SST for pCO2w (tied to
ship SST) Nutrients Nitrate, Phosphate, Silicate
Ocean Color chlorophyll Mixed layer
depth entrainment Salinity delineation of
provinces Sea surface height entrainment
Producing Seasonal CO2 Flux Maps
Algorithm development pCO2 f (SST, color)
pCO
maps
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Apply algorithm to regional SST color fields to
obtain seasonal PCO2 maps
Flux maps
Algorithm development Gas transfer, k f (U10,
SST)
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pCO2 in the Equatorial Pacific Niño 3.4 Area
There is a significant enhancement of the rate of
increase of oceanic pCO2 in the equatorial
Pacific, beginning 1989-1990, which is roughly
consistent with the increase in the overturning
circulation.
Temperature Anomaly (C)
Equatorward Convergence (106 m3s-1)
Zhang et al., (2006)
Feely et al., (2006)
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• Effect of different phase shift years chosen on
  the mean rate of change in fCO2sw for the
  preshift and postshift decade.
• Western Pacific Warm Pool region
• Nino 3.4 region
• The error bars indicate the uncertainties in the
  rate, and the numbers associated with each point
  indicate the number of data used in the analysis.

Mean Rate of Change of fCO2 _at_ SST (µatm yr-1)
Feely et al., (2006)
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Simple Relationships between fCO2 and Temperature
fCO2 versus Temperature in the Equatorial
Pacific 93 Data Sets Collected Between March 1992
and July 2001
fCO2 (27.8) -12.4T747.6 R20.574 (N520)
Sea Surface Temperature (ºC)
Cosca et al., (2003)
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pCO2 and CO2 flux in the Equatorial Pacific

• Large-Scale Observational
• Results 1982-2005
• El Niño 0.2 - 0.3 Pg C yr-1
• Non El Niño 0.5 - 0.7 Pg C yr-1
• La Niña 0.6 - 0.8 Pg C yr-1
• Average 0.5 0.2 Pg C yr-1
• Increase in flux after
• the 1997-1998 El Niño

Estimates utilize the gas transfer scaling factor
of 0.24, For NCEP-DOE AMIP-II winds (after
Takahashi et al, in prep.)
Feely et al., (in prep)
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Ocean Carbon Interannual Variability Equatorial
Pacific
(Doney, Pers. Comm)
fCO2 distributions and CO2 fluxes in the
equatorial Pacific from November 1997 thru July
2006 indicate significant interannual and decadal
changes which have been linked to ENSO
variability.
Feely et al., (in prep)
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Average CO2 Flux in the Equatorial Pacific from
165EW to 95W
Monthly Mean Wind Speed

• There is a strong decrease in CO2 flux associated
  with each ENSO event prior to 1999.

Monthly mean fCO2

• There are significant increases in wind speed,
• fCO2, and CO2 flux beginning mid-1998 thru 2001.

El Nino
CO2 flux
Feely et al., (in prep)
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?pCO2 Data from Columbus WaikatoFebruary 04
January 06
Abs Student-t Mean Value Diff
Cosca et al., (2006)
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Seasonal Variability of ?pCO2 in the Pacific
There is a strong seasonal pattern of pCO2 in
subtropical South and North Pacific which are
out of phase with each other. The equatorial
Pacific shows a weak seasonal pattern and the
subarctic Pacific shows a very strong seasonal
pattern.
Takahashi et al., (in preparation)
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pCO2 Increase in the South Pacific
There is a steady enrichment of pCO2 in the South
Pacific that is consistent with the atmospheric
increase.
Takahashi et al., (in preparation)
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Generating a Global Flux Map
Using the satellite data to derive seasonal flux
maps gives the same qualitative picture, but the
uncertainties are likely to be large and biases
non-uniform.
Park et al. 2006
Takahashi (1995)
Using the observing system data we can improve
the regional algorithms used to calculate the
flux (as we have done in the eastern equatorial
Pacific). We can also use the observing system
data to assess the uncertainties and potential
biases in the approach.
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Generating a South Pacific Regional Flux Map
Carbon Metric Uncertainty in regional seasonal
air-sea flux maps
Goal Reduce average regional uncertainty in CO2
flux to lt0.2 PgC yr-1
Approach
1. Improve regional relationships by
incorporating additional parameters (e.g. mixed
layer depth, chlorophyll) 2. Improve regional
relationships using ship-based and moored pCO2sw
observations
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CO2 Flux Anomalies by Region from 1995 thru 2005
Wanninkhof et al., (unpublished)
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Conclusions
1. Observations and models are getting much
closer to agreement with the interannual
variability, but models have not delineated
variability of long-term trends yet.
2. Observations show decadal variations of the
growth rate of CO2 in the Equatorial
Pacific but not in the South Pacific.
3. Interannual and decadal variability of CO2
fluxes in the Equatorial Pacific is primarily
controlled by changes in circulation and winds.
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Surface pCO2 Measurement Projects
R. Wanninkhof, C.L. Sabine, R. Feely, T.
Takahashi, S. Sutherland, N. Bates, F. Chavez, S.
Cooke, F. Millero and S. Maenner
Goal
To quantify the daily to interannual variability
in air-sea CO2 fluxes and understand the
mechanisms controlling these fluxes.
Approach
Make autonomous surface pCO2 measurements using
research and volunteer observing ships (VOS) to
get spatial coverage at seasonal time scales and
using a network of surface moorings to get high
frequency temporal resolution.
Achievements
The VOS program has outfitted 7 ships and has a
full data exchange policy with 7 other ships. The
moored pCO2 program currently has 10 open ocean
and 6 coastal/shelf systems deployed.