AGW Observer

Observations of anthropogenic global warming

Papers on the ocean carbon dioxide sink

Posted by Ari Jokimäki on January 14, 2010

This is a list of papers on the measurements of ocean uptake of atmospheric carbon dioxide. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Climatological mean and decadal change in surface ocean pCO2, and net sea–air CO2 flux over the global oceans – Takahashi et al. (2009) “A climatological mean distribution for the surface water pCO2 over the global oceans in non-El Niño conditions has been constructed with spatial resolution of 4° (latitude) ×5° (longitude) for a reference year 2000 based upon about 3 million measurements of surface water pCO2 obtained from 1970 to 2007. … The annual mean for the contemporary net CO2 uptake flux over the global oceans is estimated to be −1.6±0.9 Pg-C y−1, which includes an undersampling correction to the direct estimate of −1.4±0.7 Pg-C y−1. Taking the pre-industrial steady-state ocean source of 0.4±0.2 Pg-C y−1 into account, the total ocean uptake flux including the anthropogenic CO2 is estimated to be −2.0±1.0 Pg-C y−1 in 2000.”

Tracking the Variable North Atlantic Sink for Atmospheric CO2 – Watson et al. (2009) “Historically, observations have been too sparse to allow accurate tracking of changes in rates of CO2 uptake over ocean basins, so little is known about how these vary. Here, we show observations indicating substantial variability in the CO2 uptake by the North Atlantic on time scales of a few years. Further, we use measurements from a coordinated network of instrumented commercial ships to define the annual flux into the North Atlantic, for the year 2005, to a precision of about 10%.”

Saturation of the Southern Ocean CO2 Sink Due to Recent Climate Change – Le Quéré et al. (2007) “Based on observed atmospheric carbon dioxide (CO2) concentration and an inverse method, we estimate that the Southern Ocean sink of CO2 has weakened between 1981 and 2004 by 0.08 petagrams of carbon per year per decade relative to the trend expected from the large increase in atmospheric CO2. We attribute this weakening to the observed increase in Southern Ocean winds resulting from human activities, which is projected to continue in the future.” [Full text]

An empirical estimate of the Southern Ocean air-sea CO2 flux – McNeil et al. (2007) “Here we employ an independent method to estimate the Southern Ocean air-sea flux of CO2 that exploits all available surface ocean measurements for dissolved inorganic carbon (DIC) and total alkalinity (ALK) beyond 1986. … Including the effects of sea ice, we estimate a Southern Ocean (>50°S) CO2 sink of 0.4 ± 0.25 Pg C/yr. Our analysis also indicates a substantial CO2 sink of 1.1 ± 0.6 Pg C/yr within the sub-Antarctic zone (40°S–50°S), associated with strong cooling and high winds. … This paper estimates for the first time basic seasonal carbon cycle parameters within the circumpolar Southern Ocean, which have up to now been extremely difficult to measure and sparse.” [Full text]

Inverse estimates of the oceanic sources and sinks of natural CO2 and the implied oceanic carbon transport – Mikaloff Fletcher et al. (2007) “We use an inverse method to estimate the global-scale pattern of the air-sea flux of natural CO2, i.e., the component of the CO2 flux due to the natural carbon cycle that already existed in preindustrial times, on the basis of ocean interior observations of dissolved inorganic carbon (DIC) and other tracers, from which we estimate ΔCgasex, i.e., the component of the observed DIC that is due to the gas exchange of natural CO2. … We find a pattern of air-sea flux of natural CO2 characterized by outgassing in the Southern Ocean between 44°S and 59°S, vigorous uptake at midlatitudes of both hemispheres, and strong outgassing in the tropics.” [Full text]

Decadal variability of the air-sea CO2 fluxes in the equatorial Pacific Ocean – Feely et al. (2006) “In order to determine the interannual and decadal changes in the air-sea carbon fluxes of the equatorial Pacific, we developed seasonal and interannual relationships between the fugacity of CO2 (fCO2) and sea surface temperature (SST) from shipboard data that were applied to high-resolution temperature fields deduced from satellite data to obtain high-resolution large-scale estimates of the regional fluxes. … On average, the surface water fCO2 in the equatorial region has been increasing at a rate similar to the atmospheric CO2 increase. In addition, there appears to be a slight increase (∼27%) in the outgassing flux of CO2 after the 1997–1998 Pacific Decadal Oscillation (PDO) regime shift.”

The Oceanic Sink for Anthropogenic CO2 – Sabine et al. (2004) “Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic anthropogenic carbon dioxide (CO2) sink for the period from 1800 to 1994 of 118 ± 19 petagrams of carbon. The oceanic sink accounts for 48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO2 to the atmosphere of about 39 ± 28 petagrams of carbon for this period. The current fraction of total anthropogenic CO2 emissions stored in the ocean appears to be about one-third of the long-term potential.” [Full text]

Global sea–air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects – Takahashi et al. (2002) “Based on about 940,000 measurements of surface-water pCO2 obtained since the International Geophysical Year of 1956–59, the climatological, monthly distribution of pCO2 in the global surface waters representing mean non-El Niño conditions has been obtained with a spatial resolution of 4°×5° for a reference year 1995. The monthly and annual net sea–air CO2 flux has been computed using the NCEP/NCAR 41-year mean monthly wind speeds. An annual net uptake flux of CO2 by the global oceans has been estimated to be 2.2 (+22% or −19%) Pg C yr−1 using the (wind speed)2 dependence of the CO2 gas transfer velocity of Wanninkhof (J. Geophys. Res. 97 (1992) 7373).” [Full text]

Interannual Variability in the North Atlantic Ocean Carbon Sink – Gruber et al. (2002) “We report an 18-year time series of upper-ocean inorganic carbon observations from the northwestern subtropical North Atlantic near Bermuda that indicates substantial variability in this sink. We deduce that the carbon variability at this site is largely driven by variations in winter mixed-layer depths and by sea surface temperature anomalies.” [Full text]

Uptake and Storage of Carbon Dioxide in the Ocean: The Global CO2 Survey – Feely et al. (2001) “In this paper, we summarize our present understanding of the exchange of CO2 across the air-sea interface and the storage of natural and anthropogenic CO2 in the ocean’s interior.” [Full text]

Low interannual variability in recent oceanic uptake of atmospheric carbon dioxide – Lee et al. (1998) “Here we estimate the interannual variability in global net air–sea CO2 flux using changes in the observed wind speeds and the partial pressure of CO2 (p CO2) in surface sea water and the overlying air. … The calculated interannual variability in oceanic CO2 uptake of 0.4 Gt C yr-1 (2σ) is much less than that inferred from the analysis of atmospheric measurements.”

Quantification of decadal anthropogenic CO2 uptake in the ocean based on dissolved inorganic carbon measurements – Peng et al. (1998) “Accurate estimates of CO2 uptake have been difficult to obtain, however, as the annual increase of dissolved inorganic carbon (DIC) concentration in surface water due to anthropogenic input is 0.05% of the total DIC, an order of magnitude lower than past measurement precision. … Here we use recent improvements in DIC measurement techniques to determine changes in DIC concentrations between 1978 and 1995 in the Indian Ocean.”

Global air-sea flux of CO2: An estimate based on measurements of sea–air pCO2 difference – Takahashi et al. (1997) “Approximately 250,000 measurements made for the pCO2 difference between surface water and the marine atmosphere, ΔpCO2, have been assembled for the global oceans. … The annual net uptake flux of CO2 by the global oceans thus estimated ranges from 0.60 to 1.34 Gt-C yr−1 depending on different formulations used for wind speed dependence on the gas transfer coefficient. … Temperate and polar oceans of the both hemispheres are the major sinks for atmospheric CO2, whereas the equatorial oceans are the major sources for CO2. The Atlantic Ocean is the most important CO2 sink, providing about 60% of the global ocean uptake, while the Pacific Ocean is neutral because of its equatorial source flux being balanced by the sink flux of the temperate oceans. The Indian and Southern Oceans take up about 20% each.” [Full text]

Atmospheric carbon dioxide and the ocean – Siegenthaler & Sarmiento (1993) “The ocean is a significant sink for anthropogenic carbon dioxide, taking up about a third of the emissions arising from fossil-fuel use and tropical deforestation. Increases in the atmospheric carbon dioxide concentration account for most of the remaining emissions, but there still appears to be a ‘missing sink’ which may be located in the terrestrial biosphere.” [Full text]

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