ENSO-related variability in latitudinal distribution of annual mean
                        atmospheric potential oxygen (APO) in the equatorial Western Pacific

Tohjima, Yasunori; Terao, Yukio; Mukai, Hirofumi; Machida, Toshinobu; Nojiri, Yukihiro; Maksyutov, Shamil

doi:10.3402/tellusb.v67.25869

Cited by 16 publications

(23 citation statements)

References 37 publications

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“…Bender et al, 2005;Manning and Keeling, 2006;Ishidoya et al, 2012aIshidoya et al, , 2012bTohjima et al, 2015). These observations revealed spatio-temporal variations in atmospheric δ(O 2 /N 2 ) and APO.…”

Section: Observation Site and Measurement Systemmentioning

confidence: 86%

Seasonal and short-term variations in atmospheric potential oxygen at Ny-Ålesund, Svalbard

Goto

Morimoto

Aoki

et al. 2017

Tellus B: Chemical and Physical Meteorology

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Oxygen in the atmosphere undergoes variations and changes in response to biospheric activities, ocean-atmosphere exchange and fossil fuel combustion. Continuous in situ measurements of atmospheric δ(O 2 /N 2 ) and CO 2 mole fraction were started at Ny-Ålesund, Svalbard (78.93°N, 11.83°E, 40 m a.s.l.) in November 2012. Atmospheric potential oxygen (APO) calculated from the measured O 2 and CO 2 values during November 2012-January 2015 show a clear seasonal cycle with a peak-to-peak amplitude of approximately 50 per meg. The seasonal cycle of APO simulated using an atmospheric transport model, with prescribed oceanic O 2 , N 2 and CO 2 fluxes at monthly time intervals, is in excellent agreement with the observed APO. However, in spring and early summer, high values of APO are observed irregularly on a timescale of hours to days. By comparing backward trajectories of air parcels released from the site with distributions of marine net primary production (NPP), and tagged tracer experiments made using the atmospheric transport model for APO, it is found that these high APO fluctuations are primarily attributable to O 2 emissions from the Greenland Sea, the Norwegian Sea and the Barents Sea, due to marine biological productivity. Marine net community production, estimated based on the sea-to-air O 2 flux derived from observed APO fluctuations, agrees with NPP obtained from satellite observations within an order of magnitude. The results obtained in this study have still some uncertainties, but our continuous observations of atmospheric δ(O 2 /N 2 ) and CO 2 mole fraction at Ny-Ålesund can play an important role in detecting possible changes in the carbon cycle in the near future.

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Section: Observation Site and Measurement Systemmentioning

confidence: 86%

Seasonal and short-term variations in atmospheric potential oxygen at Ny-Ålesund, Svalbard

Goto

Morimoto

Aoki

et al. 2017

Tellus B: Chemical and Physical Meteorology

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“…Tohjima and colleagues attribute these anomalies mainly to the effects of ENSO‐related variations in atmospheric transport on surface APO distributions, reinforced by small variations in air‐sea fluxes of CO 2 . While the findings of Tohjima et al [] seem to contradict the inferred relation between the Scripps APO record and ENSO, they may simply reflect complex phenomena that are not resolved by the sparse tropical observations network or these studies' short analysis periods.…”

Section: Introductionmentioning

confidence: 92%

Impacts of ENSO on air‐sea oxygen exchange: Observations and mechanisms

Eddebbar

Long

Resplandy

et al. 2017

Global Biogeochemical Cycles

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Models and observations of atmospheric potential oxygen (APO ≃ O2 + 1.1 * CO2) are used to investigate the influence of El Niño–Southern Oscillation (ENSO) on air‐sea O2 exchange. An atmospheric transport inversion of APO data from the Scripps flask network shows significant interannual variability in tropical APO fluxes that is positively correlated with the Niño3.4 index, indicating anomalous ocean outgassing of APO during El Niño. Hindcast simulations of the Community Earth System Model (CESM) and the Institut Pierre‐Simon Laplace model show similar APO sensitivity to ENSO, differing from the Geophysical Fluid Dynamics Laboratory model, which shows an opposite APO response. In all models, O2 accounts for most APO flux variations. Detailed analysis in CESM shows that the O2 response is driven primarily by ENSO modulation of the source and rate of equatorial upwelling, which moderates the intensity of O2 uptake due to vertical transport of low‐O2 waters. These upwelling changes dominate over counteracting effects of biological productivity and thermally driven O2 exchange. During El Niño, shallower and weaker upwelling leads to anomalous O2 outgassing, whereas deeper and intensified upwelling during La Niña drives enhanced O2 uptake. This response is strongly localized along the central and eastern equatorial Pacific, leading to an equatorial zonal dipole in atmospheric anomalies of APO. This dipole is further intensified by ENSO‐related changes in winds, reconciling apparently conflicting APO observations in the tropical Pacific. These findings suggest a substantial and complex response of the oceanic O2 cycle to climate variability that is significantly (>50%) underestimated in magnitude by ocean models.

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“…9, each point for the in situ measurement , we conclude that these standard deviations correspond to the upper limits of the uncertainties of the in situ measurements onboard NC2. The differences between flask sampling and in situ measurements by the GC/TCD method were reported as −0.6±9.1 per meg of APO on the Oceanian route (Tohjima et al, 2015), and 7.0±9.9 per 15 meg of δ(O2/N2) at Cape Ochi-ishi . From these results, we conclude that the reliability of the O2 measurements of this study is similar to that of the GC/TCD method.…”

Section: Comparison Between Flask Sampling and In Situ Observationsmentioning

confidence: 99%

“…Latitudinal transection of the data in the western Pacific region revealed that the magnitude of equatorial elevation appearing in the annual mean APO was associated with the El Niño-Southern Oscillation cycle (Tohjima et al, 2015). The relatively high spatiotemporal sampling density allowed us to investigate the interannual variation of the annual mean APO in the western Pacific.…”

mentioning

confidence: 99%

In situ observation of atmospheric oxygen and carbon dioxide in the North Pacific using a cargo ship

Yu¹,

Tohjima²,

Katsumata³

et al. 2018

Preprint

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Abstract. Atmospheric oxygen (O2) and carbon dioxide (CO2) mixing ratios in the North Pacific were observed onboard a cargo ship, the New Century 2 (NC2), while it cruised between Japan and the United States between December 2015 and November 2016. A fuel cell analyzer and a non-dispersive infrared analyzer were used for measurement of O2 and CO2, respectively. To achieve parts-per-million precision for the O2 measurements, we precisely controlled the flow rates of the sample and reference air introduced into the analyzers and the outlet 10 pressure. A relatively low airflow rate (10 cm 3 min −1 ) was adopted to reduce the consumption rate of the reference gases. In the laboratory, the system achieved measurement precisions of 3.8 per meg for the O2/N2 ratio, which is commonly used to express atmospheric O2 variation, and 0.1 ppm for the CO2 mixing ratio. After the in situ observation started onboard NC2, we found that the ship's motion caused false wavy variations of the O2 signal with an amplitude of more than several tens of ppm and a period of about 20 s. Although we have not resolved the 15 problem at this stage, hourly averaging considerably suppressed the variation associated with ship motion.Comparison between the in situ observation and flask sampling of air samples onboard NC2 showed that the averaged differences (in situ -flask) and the standard deviations (±1σ) are −2.1±9.2 per meg for the O2/N2 ratio and −0.02±0.33 ppm for the CO2 mixing ratio. We compared the 1 yr of in situ data for atmospheric potential oxygen (APO) (= O2 + 1.1 × CO2) obtained from the broad middle-latitudes region (140°E-130°W, 29°N-45°N) 20 with previous flask sampling data from the North Pacific. This comparison showed that longitudinal differences in the seasonal amplitude of APO, ranging from 51 to 73 per meg, were smaller than the latitudinal differences.

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ENSO-related variability in latitudinal distribution of annual mean atmospheric potential oxygen (APO) in the equatorial Western Pacific

Cited by 16 publications

References 37 publications

Seasonal and short-term variations in atmospheric potential oxygen at Ny-Ålesund, Svalbard

Seasonal and short-term variations in atmospheric potential oxygen at Ny-Ålesund, Svalbard

Impacts of ENSO on air‐sea oxygen exchange: Observations and mechanisms

In situ observation of atmospheric oxygen and carbon dioxide in the North Pacific using a cargo ship

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