Air-sea CO2 Research Articles

Air—sea CO 2 fluxes in a coastal embayment affected by upwelling: physical versus biological control

Water column pCO 2 and air-sea CO 2 fluxes were studied during an 18-month period (May 1994–September 1995) in a coastal embayment affected by upwelling, located in the northwestern Iberian Peninsula (Ria de Vigo and adjacent shelf). Overall, the region acted as a net annual atmospheric CO 2 sink, with magnitude ranging from 0.54 mgC m −2d −1 in the Ria estuary to 22 mgC m −2d −1 offshore. During moderate upwelling and upwelling relaxation conditions the sampling area was a sink for atmospheric CO 2. By contrast, during winter conditions and during intense upwelling the flux reversed towards the atmosphere. The relative influence of physical and biological processes on pCO 2 was evaluated using two different approaches: firstly, statistical analysis of physico-chemical correlations, and secondly, a thermodynamic analysis in the oceanic CO 2 system. Both methods yielded consistent results, showing that the main processes controlling seasonal and spatial pCO 2 variability were the production and remineralization of organic matter, explaining ca. 70 % of the total variability. In the inner part of the embayment, air-sea CO 2 exchange was mainly modulated by CO 2 partial pressure gradient, whereas in the adjacent shelf, wind speed largely contributed to CO 2 fluxes between the ocean and the atmosphere.

Satellite sea surface temperature: a powerful tool for interpreting in situ pCO2 measurements in the equatorial Pacific Ocean

In order to determine the seasonal and interannual variability of the CO 2 released to the atmosphere from the equatorial Pacific, we have developed p CO 2 -temperature relationships based upon shipboard oceanic CO 2 partial pressure measurements, p CO 2 , and satellite sea surface temperature, SST, measurements. We interpret the spatial variability in p CO 2 with the help of the SST imagery. In the eastern equatorial Pacific, at 5°S, p CO 2 variations of up to 100 μatm are caused by undulations in the southern boundary of the equatorial upwelled waters. These undulations appear to be periodic with a phase and a wavelength comparable to tropical instability waves, TIW, observed at the northern boundary of the equatorial upwelling. Once the p CO 2 signature of the TIW is removed from the Alize II cruise measurements in January 1991, the equatorial p CO 2 data exhibit a diel cycle of about 10 matm with maximum values occurring at night. In the western equatorial Pacific, the variability in p CO 2 is primarily governed by the displacement of the boundary between warm pool waters, where air–sea CO 2 fluxes are weak, and equatorial upwelled waters which release high CO 2 fluxes to the atmosphere. We detect this boundary using satellite SST maps. East of the warm pool, Δ P is related to SST and SST anomalies. The 1985–97 CO 2 flux is computed in a 5° wide latitudinal band as a combination of Δ P and CO 2 exchange coefficient, K , deduced from satellite wind speeds, U . It exhibits up to a factor 2 seasonal variation caused by K -seasonal variation and a large interannual variability, a factor 5 variation between 1987 and 1988. The interannual variability is primarily driven by displacements of the warm pool that makes the surface area of the outgassing region variable. The contribution of Δ P to the flux variability is about half the contribution of K . The mean CO 2 flux computed using either the Liss and Merlivat (1986) or the Wanninkhof (1992) K – U parametrization amounts to 0.11 GtC yr −1 or to 0.18 GtC yr −1 , respectively. The error in the integrated flux, without taking into account the uncertainty on the K – U parametrization, is less than 31%. DOI: 10.1034/j.1600-0889.1999.00025.x

Temporal variations of mixed-layer oceanic CO<SUB>2</SUB> at JGOFS-KERFIX time-series station: Physical versus biogeochemical processes

The seasonal and interannual variations in mixed-layer carbon dioxide in the Southern Ocean are analyzed from January 1990 to March 1995 at KERFIX time-series station (50°40S-69°25E). The temperature, salinity and chlorophyll time series are used as constraints on a simple box model to extrapolate total dissolved inorganic carbon (DIC), total alkalinity (TA) and oceanic CO 2 fugacity (fCO 2 ) over the five years of the monitoring. Results of the simulation are compared to all available observations. Both measured and simulated DIC and TA give seasonal signals of 25 μmol/kg and 8 μeq/kg, respectively. In spite of a weak primary production about 70 gC/m 2 /yr, the biological pump appears to play a significant role on seasonal and interannual variations in air-sea CO 2 exchanges. Its contribution varies from 10 to 45% of the total sea surface fCO 2 variations depending on the period. This area has been a sink for atmospheric CO 2 with annual mean values of -0.8 to -3.0 mol/m 2 /yr during the whole period investigated. Annually the CO 2 sink is due to the balance between biological activity and mixing processes on fCO 2 inducing thermodynamically mediated variations. The sink's interannual variations appear to be mainly due to the high variability of the wind speeds and hence, of the mixed-layer depth. The impact of the anthropogenic atmospheric CO 2 increase on oceanic fCO 2 is also investigated. The rate of increase of oceanic fCO 2 (0.6 μatm/yr) was half that of atmospheric fCO 2 (1.2 μatm/yr). The increase of the air-sea CO 2 gradient lead to an increase of the CO 2 sink of about 0.07 mol/m 2 /yr (0.02 GtC/yr) over the five years investigated.

CO2 fluxes from a coastal transect: a time-series approach

The coastal ocean is a region with highly variable physical processes, and high and variable rates of primary production and organic matter recycling, but very little is known about the effect of these factors on the flux of CO 2 into or out of this environment. To address this question, a time-series of geochemical measurements was initiated along a 32 km transect across the inner continental shelf , off New Jersey. Water column measurements of temperature, salinity, total carbon dioxide, total alkalinity, oxygen and nutrients were made approximately monthly at seven stations along the transect. Fluxes (−0.43 to −0.84 mol m −2 yr −1 ) calculated from local wind speed and the air–sea CO 2 difference indicate that this region acts as a small net sink for atmospheric CO 2 on a yearly averaged basis. The inner and outer stations varied on different time-scales, but in general, surface waters were a source of CO 2 to the atmosphere in the summer and fall, offset by large fluxes into the surface waters during the winter to early spring. The calculated fugacity of surface water carbon dioxide ( f CO 2 ) between April 1994 and April 1996 ranged from 211 to 658 μatm. Superimposed on the large spatial and temporal variability typical of the coastal environment, was a clear seasonal trend in f CO 2 which was primarily responsible for the observed trend in the flux. The dominant processes responsible for the observed changes in f CO 2 are examined in detail. An important finding is that the magnitude of the effect of organic matter cycling on changes in f CO 2 generally decreased in the offshore direction.

Contribution of soft-bottoms to the community metabolism (primary production and calcification) of a barrier reef flat (Moorea, French Polynesia)

The relative contribution of soft bottoms to the community metabolism (primary production, respiration and net calcification) of a barrier reef flat has been investigated at Moorea (French Polynesia). Community metabolism of the sedimentary area was estimated using in situ incubations in perspex chambers, and compared with estimates of community metabolism of the whole reef flat obtained using a Lagrangian technique (Gattuso et al., 1996. Carbon flux in coral reefs. 1. Lagrangian measurement of community metabolism and resulting air–sea CO 2 disequilibrium. Mar. Ecol. Prog. Ser. 145, 109–121). Net organic carbon production ( E), respiration ( R) and net calcification ( G) of sediments were measured by seven incubations performed in triplicate at different irradiance. Respiration and environmental parameters were also measured at four randomly selected additional stations. A model of Photosynthesis–irradiance allowed to calculate oxygen (O 2), organic carbon (CO 2) and calcium carbonate (CaCO 3) evolution from surface irradiance during a diel cycle. As chlorophyll a content of the sediment was not significantly different between stations, primary production of the sediment was considered as homogeneous for the whole lagoon. Thus, carbon production at the test station can be modelled from surface light irradiance. The modelled respiration was two times higher at the test station than the mean respiration of the barrier reef, and thus underestimated sediment contribution to excess production. Sediments cover 40–60% of the surface and accounted for 2.8–4.1% of organic carbon excess production estimated with the modelled R and 21–32% when mean R value was considered. The sedimentary CaCO 3 budget was a very minor component of the whole reef budget.

Sensitivity of a global oceanic carbon cycle model to the circulation and to the fate of organic matter: Preliminary results

We examine the effect of the circulation on the resulting distribution of tracers in the ocean and the sensitivity of surface CO 2 to the remineralization cycle of organic matter. For this purpose we built a 3-dimensional global model of the oceanic carbon cycle. The processes considered are air-sea CO 2 exchanges, export production of organic matter and its remineralization, CaCO 3 precipitation and dissolution or sedimentation. The annual mean fields needed to drive the model are provided by two different OGCM's. The sensitivity of the tracer distribution to the circulation is evaluated by examining the results obtained with each set of hydrodynamic fields driving the geochemical model with identical parameterizations of the biochemical processes in both cases. The model is then applied to investigate the consequences on the surface Δ p co 2 of various behavior of the dead organic material. The consideration of fast sinking particles leads to a distribution which is in better agreement with measurements than the one obtained under the assumption that the organic matter is mainly under dissolved form.

Spatio-temporal distributions of air-sea fluxes of CO2 in the Indian and Antarctic oceans. A first step

Sea surface and atmospheric measurements of carbon dioxide fugacity (fCO 2 ) made during 14 cruises in 1991, 1992 and 1993, are used to describe the seasonal and meridional variation of air-sea CO 2 flux into the antarctic, subantarctic, subtropical and tropical regions of the Indian Ocean. We first estimate seasonal (January to May and May to September) zonal averaged air-sea CO 2 fluxes from shipboard measured sea surface and atmospheric fCO 2 as well as observed ship winds. Depending of the gas transfer coefficient used, a sink of −0.22 or −0.43 Gt Carbon from January to September is calculated for the band 50°S-20°S. From June to September, the tropical region is a source between 0.04 and 0.08 GtC. From January to May, the southern ocean is a sink between −0.01 and −0.03 GtC. Next, we compare these observed air-sea fluxes CO 2 calculations with reconstructed sea surface fCO 2 distributions obtained from climatological data (SST and wind). By using the in-situ data obtained in 1991, large-scale seasonal relations between sea surface fCO 2 and sea surface temperature (SST) are extracted and applied to the 1992 monthly climatological SST fields in the 50°S-20°S region only. Compared to observations made in 1992, seasonal sea surface fCO 2 distribution is well reproduced. In the band 50°S-20°S, reconstructed sea surface fCO 2 and climatological gas transfert coefficient computed from derived climatological winds lead to an annual air-sea CO 2 exchange between −0.20 and −0.37 Gt Carbon/year

Spatio-temporal distributions of air-sea fluxes of CO<sub>2</sub> in the Indian and Antarctic oceans

Sea surface and atmospheric measurements of carbon dioxide fugacity (fCO 2 ) made during 14 cruises in 1991, 1992 and 1993, are used to describe the seasonal and meridional variation of air-sea CO 2 flux into the antarctic, subantarctic, subtropical and tropical regions of the Indian Ocean. We first estimate seasonal (January to May and May to September) zonal averaged airsea CO 2 fluxes from shipboard measured sea surface and atmospheric f CO 2 as well as observed ship winds. Depending of the gas transfer coefficient used, a sink of – 0.22 or – 0.43 Gt Carbon from January to September is calculated for the band 50°S−20°S. From June to September, the tropical region is a source between 0.04 and 0.08 GtC. From January to May, the southern ocean is a sink between 0.01 and -0.03 GtC. Next, we compare these observed air-sea fluxes CO 2 calculations with reconstructed sea surface fCO 2 distributions obtained from climatological data (SST and wind). By using the in-situ data obtained in 1991, large-scale seasonal relations between sea surface fCO 2 and sea surface temperature (SST) are extracted and applied to the 1992 monthly climatological SST fields in the 50°S−20°S region only. Compared to observations made in 1992, seasonal sea surface f CO 2 distribution is well reproduced. In the band 50°S−20°S, reconstructed sea surface f CO 2 and climatological gas transfert coefficient computed from derived climatological winds lead to an annual air-sea CO 2 exchange between -0.20 and -0.37 Gt Carbon/year. DOI: 10.1034/j.1600-0889.47.issue1.7.x

Long-term trend of the partial pressure of carbon dioxide (pCO<sub>2</sub>) in surface waters of the western North Pacific, 1984-1993

The ocean is an important sink for anthropogenic CO 2 emissions, but there are only a few measurements which confirm the oceanic CO 2 uptake. Since 1981, partial pressure of CO 2 (pCO 2 ) in the western North Pacific (35°N−3°N, 128°E−155°E) and the overlying air have been measured periodically to clarify the seasonal and long-term trends of the oceanic carbonate system. The partial pressure of CO 2 in surface seawater (pCO 2 sea ) observed every boreal winter during the period from 1984 to 1993 give a growth rate of 1.8 ± 0.6 µ atm yr -1 ( n = 27) north of 15°N and 0.5 ± 0.7 µ atm yr -1 ( n = 23) south of 14°N with an average of 1.2 ± 0.9 µ atm yr -1 ( n = 50). The rate of pCO 2 sea a increase north of 15°N is equal to that of atmospheric CO 2 (1.8 µ atm yr -1 ) during the same period but that south of 14°N is lower. The difference in rate of pCO 2 sea a increase is suggestive of temporal variations in ΔpCO 2 distribution. After removing the long-term trend from the pCO 2 sea data, the seasonal variation of pCO 2 sea in the western North Pacific (132°E−142°E) was evaluated with a linear regression between the pCO 2 sea and sea surface temperature (SST). Generally, a thermodynamic process (temperature effect) plays a predominant role in determining the seasonal variations of pCO 2 sea . South of 14°N, however, a clear interannual variability is significant relative to the seasonal changes if an El Nino event is accompanied by enhanced vertical mixing. The annual air-sea CO 2 flux showed a large influx of CO 2 into the ocean north of 27°N (Kuroshio Counter Current) because of a large negative ΔpCO 2 (− 60 µ atm) and strong wind during the winter season. Toward the south, the annual average air-sea CO 2 flux increased by 9 mmol m -2 day -1 from – 8 mmol m -2 day -1 at 31°N to 1 mmol M -2 day -1 at 5°N. South of 10°N, the ocean acts as a source for atmospheric CO 2 (0.2-0.7 mmol m -2 day -1 ), but this is a considerably weaker source as compared with those of the central and eastern equatorial Pacific. The observed increase of pCO 2 sea and the estimated air/sea CO 2 flux suggest the importance of carbon transport from the mixed layer to the intermediate/deep water in the area of Subtropical Mode Water formation, south of the Kuroshio and east of Japan. DOI: 10.1034/j.1600-0889.47.issue4.2.x

Geographical, seasonal and interannual variations of air-sea CO<sub>2</sub> exchange in the subtropical Pacific surface waters during 1983–1988: (II). Air-sea CO<sub>2</sub> fluxes with skin-temperature adjustments

Air-sea fluxes of CO 2 in surface seawater of the northeast (15°N–45°N) and southwest (25°S–15°S) subtropical Pacific Ocean from January 1985 to February 1988 were estimated. Initially, the net CO 2 flux unadjusted for the temperature deviation at the sea surface microlayer was estimated as a multiplicative product of the CO 2 transfer velocity, the solubility of CO 2 in seawater, and the difference in CO 2 fugacities between surface seawater and air. The fugacities of CO 2 in surface seawater and in the overlying air were given in Part I of this report. We used the Liss-Merlivat formulation to estimate the CO 2 transfer velocity from wind speed and seawater temperature. The monthly mean CO 2 fluxes were also adjusted for the temperature deviation Δ T between the mixed layer and the surface skin. The mean Δ T was estimated from the climatological means of solar radiation and heat fluxes across the boundary layer. Estimated Δ T for 1985-1988 averaged about 0.3 °C. The overall effect of the depressing skin temperature was an increased strength of the CO 2 sink, as expressed by a factor o to estimate the surface temperature deviation on the net CO 2 flux for a given month and oceanic zone. The relative shifts between unadjusted and adjusted fluxes on a seasonal basis for each 10° latitudinal bands in the subtropical Pacific could vary between + 56% and – 71%. During the study period, the adjustments increased the net CO 2 fluxes within 25°S−15°S by 5% in austral winter and 56% in austral summer. Within 15°N-35°N, CO 2 effluxes reduced in the summer by 39% but increased in the winter by 15%. In northern waters within 35°N−45°N, the summer CO 2 effluxes were reduced by about 14%, whereas the winter CO 2 influxes showed an increased of about 7%. Thus, it is important to include the skin temperature effect in deriving the correct magnitude of the air-sea CO 2 flux. In the boreal winter/spring, the northeast Pacific within 15°N−35°N was a CO 2 sink with the adjusted net CO 2 flux averaged about – 1.7 mmol CO 2 m -2 d -1 during the 1986/1987 El Nino and about – 2.2 mmol m -2 d -1 before and after the El Nino. In the boreal summer/autumn, the CO 2 fluxes averaged, respectively, about 0.4 mmol m -2 d -1 and 0.6 mmol m -2 d -1 during the El Nino and the non-El Nino periods. Within 35°N-45°N, the average CO 2 flux was about 1.4 mmol m -2 d -1 in summer; about – 5.2 mmol m -2 d -1 in the winter/spring. The southwest subtropical Pacific within 25°5-15°S was basically a CO 2 sink year round with net CO 2 flux averaged at about – 2.0 mmol m -2 d -1 in austral winter/spring and – 0.7 mmol m -2 d -1 in austral summer/autumn. DOI: 10.1034/j.1600-0889.47.issue4.4.x

Measurements of atmospheric and oceanic CO<sub>2</sub> in the tropical Atlantic: 10 years after the 1982-1984 FOCAL cruises

Measurements of CO 2 parameters in and over the tropical Atlantic ocean have been made during the CITHER 1 cruise (January to March 1993). These observations are compared to the results obtained a decade earlier in the same area during the FOCAL experiment (1982-1984). The increase of atmospheric CO 2 (1.3 to 1.5 ppm year -1 ) is in agreement with the secular trend. The variation of CO 2 fugacity, f CO 2 , in surface seawater is analysed and compared with variations of hydrographic conditions. The apparent increase of ocean surface f CO 2 is somewhat higher than the atmospheric increase: during the 9-year period, the apparent increase of oceanic f CO 2 is found to range from 22.5 to 24.9 µ tm. A new estimate of air-sea CO 2 flux in the Atlantic equatorial belt indicates that the oceanic source is enhanced in 1993 compared to 1984. An interannual change in total inorganic carbon, T CO 2 , through the accumulation of CO 2 in the mixed layer is assessed and analysed in comparison with the f CO 2 increase. The agreement between the evolutions of the two parameters of the oceanic CO 2 system is acceptable by taking into account the uncertainties to estimate these evolutions. DOI: 10.1034/j.1600-0889.47.issue1.8.x

Enhanced calcification in the coccolithophorid Emiliania huxleyi (Haptophyceae) under phosphorus limitation

Abstract The effect of phosphorus limitation on calcification in the coccolithophorid Emiliania huxleyi (Lohmann) Hay et Mohler was investigated by chemical Ca and C analyses, as well as in short-term 14C uptake experiments. The latter made use of a newly developed microdiffusion method to separate 14C in coccolith carbonate from photosynthetically assimilated 14C. In comparison with exponentially growing cells in a nutrient-replete medium, cells grown in P-limited chemostats at half the maximum growth rate produced c. 60% more CaCO3 relative to organic carbon. In the short-term incubations, cells from P-limited chemostats showed a relative increase in the capacity for calcification under reduced irradiance and in the dark. Nutrient effects on calcification are of potential interest in considerations of the impact of E. huxleyi blooms on the sea-air CO2 interchange, and they deserve further study.

Acknowledgement

Despite their moderately sized surface area, continental marginal seas play a significant role in the biogeochemical cycles of carbon, as they receive huge amounts of upwelled and riverine inputs of carbon and nutrients, sustaining a disproportionate large biological activity compared to their relative surface area. A synthesis of worldwide measurements of the partial pressure of CO2 (pCO2) indicates that most open shelves in the temperate and high-latitude regions are under-saturated with respect to atmospheric CO2 during all seasons, although the low-latitude shelves seem to be over-saturated. Most inner estuaries and near-shore coastal areas on the other hand are over-saturated with respect to atmospheric CO2. The scaling of air–sea CO2 fluxes based on pCO2 measurements and carbon mass-balance calculations indicate that the continental shelves absorb atmospheric CO2 ranging between 0.33 and 0.36 Pg C yr−1 that corresponds to an additional sink of 27% to ∼30% of the CO2 uptake by the open oceans based on the most recent pCO2 climatology [Takahashi, T., Sutherland, S.C., Wanninkhof, R., Sweeney, C., Feely, R.A., Chipman, D., Hales, B., Friederich, G., Chavez, F., Watson, A., Bakker, D., Schuster, U., Metzl, N., Inoue, H.Y., Ishii, M., Midorikawa, T., Sabine, C., Hoppema, M., Olafsson, J., Amarson, T., Tilbrook, B., Johannessen, T., Olsen, A., Bellerby, R., De Baar, H., Nojiri, Y., Wong, C.S., Delille, B., Bates, N., 2009. Climatological mean and decadal change in surface ocean pCO2, and net sea–air CO2 flux over the global oceans. Deep-Sea Research II, this issue [doi: 10.1016/j.dsr2.2008.12.009].]. Inner estuaries, salt marshes and mangroves emit up to 0.50 Pg C yr−1, although these estimates are prone to large uncertainty due to poorly constrained ecosystem surface area estimates. Nevertheless, the view of continental shelves as sinks and near-shore ecosystems as sources of atmospheric CO2 allows reconciling long-lived opposing views on carbon cycling in the coastal ocean.

Community metabolism and air-sea C02 fluxes in a coral reef ecosystem (Moorea, French Polynesia)

Community metabolism (primary production, respiration and calcification) and air-sea CO2 fluxes of the 'Tiahura barrier reef' (Moorea, French Polynesia) were investigated in November and December 1991 Gross production and respiration were respectively 640.2 to 753 and 590.4 to 641.5 mm01 (02 or CO2) m-' d-l (7.7 to 9.0 and 7.1 to 7.7 g C m-2 d ' ) and the reef displayed a slightly negative excess (= net) production. The contribution of planktonic primary production to reef metabolism was negligible (0.15 ?4, of total gross production). Net calcification was positive both during the day and at night; its daily value was 243 mm01 CaCO, m-2 d ' (24.3 g CaC03 m m 2 d-l). Reef metabolism decreased seawater total CO2 by 433.3 mm01 m-d-' The air-sea CO, fluxes were close to zero in the ocean but displayed a strong daily pattern at the reef front and the back reef. Fluxes were positive (COz evasion) at night, decreased as irradiance increased and were negative during the day (COz invasion) Integration of the fluxes measured during a 24 h experiment at the back reef showed that the reef was a source of CO2 to the atmosphere (1 5 minol m-2 d-l).

Air‐sea CO2 fluxes in the equatorial Pacific in January‐March 1991

The partial pressure of CO2 in surface seawater and in air were continuously measured during the cruise ALIZE II (January 1991–March 1991) in the equatorial Pacific from Panama to Nouméa via Tahiti. It provides a large set of data for estimating the air‐sea CO2 flux in the equatorial Pacific. An average flux is calculated between 2.5N and 2.5S. This estimation ranges from 5 to 8.5 mmol m−2d−1 according to the CO2 exchange coefficient used.

Intrinsic error in the air-sea CO<sub>2</sub> exchange coefficient resulting from the use of satellite wind speeds

This paper is aimed at justifying the use of satellite wind speed measurements for the determination of the carbon dioxide exchange coefficient at the air–sea interface. We relate it to the wind speed using a relationship determined by Liss and Merlivat, which enables us to monitor the spatio-temporal variations of the CO 2 exchange coefficient on a global scale, using satellite measurements of the wind speed. Yet these measurements integrate the wind speed over areas having a diameter ranging from 25 to 100 km. Moreover, a satellite has a global coverage only after a few days and samples a given place every few days (usually 3 days). We simulate the spatial integration and temporal sampling of spacecraft measurements from in-situ wind speed measurements to infer the errors induced. While the space integration results in a negligible error (a few tenths of cm h -1 at most), a caveat should be given about the sampling error. It is of the order of the statistical error of a normal distribution, depending on the standard deviation and number of measurements. An example of the statistical error resulting from the use of 1 month of SEASAT scatterometer data is shown. Provided this caution about the statistical error is kept in mind and the space and time integration is properly chosen, satellite data, after careful validation of the wind speed retrieval, are well suited for long-term global survey of the CO 2 exchange coefficient space and time variations. The use of a relationship between the exchange coefficient and the wind speed, which accuracy is presently discussed, is the only way to access these variations. DOI: 10.1034/j.1600-0889.1991.00016.x

Exxon global CO2 measurement system

This paper describes a system designed to acquire atmospheric and surface-ocean pCO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> data essential to the scientific study of air-sea CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> exchange, atmospheric CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> growth, and their variabilities. Highlighted is a computer-based measurement system installed aboard an oil tanker whose route traverses several oceans.

A first measurement of sea-air CO2flux by eddy correlation

CO2 fluxes between the ocean and the atmosphere were measured off a beach on Sable Island by using the eddy correlation method. These gas fluxes were measured directly over a short enough time period and a local enough region that weather and other conditions which determine the fluxes were nearly constant. Values for the fluxes measured were about 0.8 μmol/m2 s out of the ocean.