Prevalence of strong vertical CO<sub>2</sub> and O<sub>2</sub> variability in the top meters of the ocean

Calleja, María Ll.; Duarte, Carlos M.; Álvarez, Marta; Vaquer-Sunyer, Raquel; Agustı́, Susana; Herndl, Gerhard J.

doi:10.1002/gbc.20081

Cited by 17 publications

(18 citation statements)

References 49 publications

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“…For dissolved gases, vertical gradients in the top meters due to surface trapping had been predicted (McNeil and Merlivat, 1996), and later were observed in the open ocean (Soloviev et al, 2002;Calleja et al, 2013). The two studies showed that concentration differences of oxygen and carbon dioxide exist across the top meters of several open ocean regions, however 5 with little average effect on gas exchange estimates.…”

Section: Introductionmentioning

confidence: 91%

“…A study on oxygen gradients and fluxes in the open ocean during the GasEx98 project (Soloviev et al, 2002) found weak gas gradients (average 15 systematic oxygen flux overestimation of 4 % across the top 4 m, with peak maxima of 30 % in calm conditions). A study on oxygen and CO 2 near-surface gradients in different open ocean regions (Calleja et al, 2013) found large variability of upward and downward near-surface gas gradients in the top 8 m, which however was unsystematic with the mean gradient not significantly different from zero (their Fig. 2).…”

Section: Impact Of Near-surface N 2 O Gradients On Bias Of Total Emismentioning

confidence: 96%

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Gas exchange estimates in the Peruvian upwelling regime biased by multi-day near-surface stratification

Fischer¹,

Kock²,

Arévalo‐Martínez³

et al. 2018

Preprint

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The coastal upwelling regime off Peru in December 2012 showed considerable concentration gradients of dissolved nitrous oxide (N 2 O) across the top few meters of the ocean. The gradients were predominantly downward, i.e. concentrations decreased toward the surface. Ignoring these gradients causes a systematic error in regionally integrated gas exchange estimates, when using observed concentrations at several meters below the surface as input for bulk flux parameterizations -as is routinely practiced. Here we propose that multi-day near-surface stratification events are responsible for the observed near-surface N 2 O 5 gradients, and that the gradients induce the strongest bias in gas exchange estimates at winds of about 3 to 6 m s −1 . Glider hydrographic time series reveal that events of multi-day near-surface stratification are a common feature in the study region. In the same way as shorter events of near-surface stratification (e.g. the diurnal warm layer cycle), they preferentially exist under calm to moderate wind conditions, suppress turbulent mixing, and thus lead to isolation of the top layer from the waters below (surface trapping). Our observational data in combination with a simple gas-transfer model of the surface trapping mechanism 10 show that multi-day near-surface stratification can produce near-surface N 2 O gradients comparable to observations. They further indicate that diurnal and shorter stratification cycles can only create N 2 O gradients that do not substantially impact emission estimates. Quantitatively, we estimate that the integrated bias for the entire Peruvian upwelling region in December 2012 represents an overestimation of the total N 2 O emission by about a third, if concentrations at 5 m or 10 m depth are used as surrogate for bulk water N 2 O concentration. Locally, gradients exist which would cause emission overestimations by a factor 15 of two or more. As the Peruvian upwelling region is an N 2 O source of global importance, and other strong N 2 O source regions could tend to develop multi-day near-surface stratification as well, the bias resulting from multi-day near-surface stratification may also impact global oceanic N 2 O emission estimates.Biogeosciences Discuss., https://doi.

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Section: Introductionmentioning

confidence: 91%

Section: Impact Of Near-surface N 2 O Gradients On Bias Of Total Emismentioning

confidence: 96%

Gas exchange estimates in the Peruvian upwelling regime biased by multi-day near-surface stratification

Fischer¹,

Kock²,

Arévalo‐Martínez³

et al. 2018

Preprint

View full text Add to dashboard Cite

show abstract

“…Other typical approaches to collecting surface water p CO 2 data are discrete station sampling by rosette, which retrieves water from no shallower than 1 m or from drifting or moored surface buoys (e.g., Bakker et al, ; Sutton et al, ). In temperate, well‐mixed, open ocean waters, all these approaches may give similar estimates of p CO 2 under most conditions, but significant near‐surface vertical variability in p CO 2 has been observed across a range of oceanic environments (Calleja et al, ; Murata et al, ), particularly in river‐influenced coastal waters (Gong et al, ). Also, under very calm conditions, true surface p CO 2 , in the sea‐surface microlayer directly in contact with the atmosphere, may be different from even the values measured directly below the surface, because of slow diffusion, reactions occurring in the microlayer, or near‐surface temperature gradients (Garbe et al, ; Wanninkhof & Knox, ; Ward et al, ).…”

Section: Arctic Ocean Stratification and Estimating Air‐sea Co2 Fluxementioning

confidence: 99%

Air‐Sea CO₂ Flux Estimates in Stratified Arctic Coastal Waters: How Wrong Can We Be?

Miller

Burgers

Burt

et al. 2019

Geophysical Research Letters

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Summer near‐surface seawater sampling in the Canadian Arctic revealed potential for significant errors (nearly 0.1 μmol·(m‐2 s‐1)) in CO2 fluxes calculated from measured air‐sea CO2 gradients. River runoff and sea ice melt strongly stratify these waters, often resulting in surface mixed layers only a few meters thick and isolated from waters sampled by shipboard underway systems. Samples collected with the underway system, rosette, and small boats exposed substantial near‐surface gradients in CO2 partial pressure (pCO2) over the top 7 m at many stations. Distributions of temperature, salinity, and fluorescence indicated that the sources of the CO2 system gradients varied between stations, precluding simple corrections to align subsurface data with shallower conditions. Overall, the strong summertime sink of atmospheric CO2 implied by the underway data was not supported by shallower data.

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“…For example, most k-wind-speed parameterizations do not explicitly capture the solubility effects associated with bubbles (Blomquist et al, 2006), although the COAREG gas transfer model incorporates this factor into a physically based flux algorithm (Fairall et al, 2003. Biogeochemical gradients near or at the ocean surface are also not considered, despite their potential to alter the air-sea exchange of gases, PMAs and SMAs (Facchini et al, 2008;Calleja et al, 2013).…”

Section: Comparison Of Soap Aerosol Number and Size Distributions 1 Imentioning

confidence: 99%

Overview and preliminary results of the Surface Ocean Aerosol Production (SOAP) campaign

et al. 2017

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Abstract. Establishing the relationship between marine boundary layer (MBL) aerosols and surface water biogeochemistry is required to understand aerosol and cloud production processes over the remote ocean and represent them more accurately in earth system models and global climate projections. This was addressed by the SOAP (Surface Ocean Aerosol Production) campaign, which examined air-sea interaction over biologically productive frontal waters east of New Zealand. This overview details the objectives, regional context, sampling strategy and provisional findings of a pilot study, PreSOAP, in austral summer 2011 and the following SOAP voyage in late austral summer 2012. Both voyages characterized surface water and MBL composition in three phytoplankton blooms of differing species composition and biogeochemistry, with significant regional correlation observed between chlorophyll a and DMSsw. Surface seawater dimethylsulfide (DMSsw) and associated air-sea DMS flux showed spatial variation during the SOAP voyage, with maxima of 25 nmol L −1 and 100 µmol m −2 d −1 , respectively, recorded in a dinoflagellate bloom. Inclusion of SOAP data in a regional DMSsw compilation indicates that the current climatological mean is an underestimate for this region of the southwest Pacific. Estimation of the DMS gas transfer velocity (k DMS ) by independent techniques of eddy covariance and gradient flux showed good agreement, although both exhibited periodic deviations from model estimates. Flux anomalies were related to surface warming and sea surface microlayer enrichment and also reflected the heterogeneous distribution of DMSsw and the associated flux footprint. Other aerosol precursors measured included the halides and various volatile organic carbon compounds, with first measurements of the short-lived gases glyoxal and methylglyoxal in pristine Southern Ocean marine air indicating an unidentified local source. The application of a real-time clean sector, contaminant markers and a common aerosol inlet facilitated multi-sensor measurement of uncontaminated air. Aerosol characterization identified variable Aitken mode and consistent submicron-sized accumulation and coarse modes. Submicron aerosol mass was dominated by secondary particles containing ammonium sulfate/bisulfate under light winds, with an increase in sea salt under higher wind speeds. MBL measurements and chamber experiments identified a significant organic component in primary and secondary aerosols. Comparison of SOAP aerosol number and size distributionsPublished by Copernicus Publications on behalf of the European Geosciences Union. 13646 C. S. Law et al.: Overview and preliminary results of the SOAP campaign reveals an underprediction in GLOMAP (GLObal Model of Aerosol Processes)-mode aerosol number in clean marine air masses, suggesting a missing marine aerosol source in the model. The SOAP data will be further examined for evidence of nucleation events and also to identify relationships between MBL composition and surface ocean biogeochemistry that may pr...

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Prevalence of strong vertical CO₂ and O₂ variability in the top meters of the ocean

Cited by 17 publications

References 49 publications

Gas exchange estimates in the Peruvian upwelling regime biased by multi-day near-surface stratification

Gas exchange estimates in the Peruvian upwelling regime biased by multi-day near-surface stratification

Air‐Sea CO₂ Flux Estimates in Stratified Arctic Coastal Waters: How Wrong Can We Be?

Overview and preliminary results of the Surface Ocean Aerosol Production (SOAP) campaign

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Prevalence of strong vertical CO2 and O2 variability in the top meters of the ocean

Cited by 17 publications

References 49 publications

Gas exchange estimates in the Peruvian upwelling regime biased by multi-day near-surface stratification

Gas exchange estimates in the Peruvian upwelling regime biased by multi-day near-surface stratification

Air‐Sea CO2 Flux Estimates in Stratified Arctic Coastal Waters: How Wrong Can We Be?

Overview and preliminary results of the Surface Ocean Aerosol Production (SOAP) campaign

Contact Info

Product

Resources

About

Prevalence of strong vertical CO₂ and O₂ variability in the top meters of the ocean

Air‐Sea CO₂ Flux Estimates in Stratified Arctic Coastal Waters: How Wrong Can We Be?