Supplementary material to "Investigating the effect of El Niño on nitrous oxide distribution in the Eastern Tropical South Pacific"

2018 ◽  
Author(s):  
Qixing Ji ◽  
Mark A. Altabet ◽  
Hermann W. Bange ◽  
Michelle I. Graco ◽  
Xiao Ma ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
El Niño ◽  
El Nino ◽  
South Pacific ◽  
Supplementary Material

scholarly journals Investigating the effect of El Niño on nitrous oxide distribution in the Eastern Tropical South Pacific

2018 ◽  
Author(s):  
Qixing Ji ◽  
Mark A. Altabet ◽  
Hermann W. Bange ◽  
Michelle I. Graco ◽  
Xiao Ma ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
South Pacific ◽  
Biological Properties ◽  
Nitrite Reduction ◽  
Sea Surface ◽  
N2o Production ◽  
Annual Variations

Abstract. The open ocean is a major source of atmospheric warming and ozone depleting gas nitrous oxide (N2O). Intense sea-to-air fluxes of N2O occur in major oceanic upwelling regions such as the Eastern Tropical South Pacific Ocean (ETSP). The ETSP is influenced by the El Niño-Southern Oscillation that leads to inter-annual variations of physical, chemical and biological properties. A strong El Niño was developing in this region in October 2015, during which we investigated the N2O production pathways and, by comparing to previous non-El Niño years, the effects of El Niño on water column N2O distributions and fluxes. Analysis of N2O natural abundance isotopomers suggested that both nitrification and partial denitrification (nitrate and nitrite reduction to N2O) were important N2O production pathways. Higher than normal sea-surface temperatures were associated with a deepening of the oxycline, while the level of sea surface N2O supersaturation on the continental shelf was nearly an order of magnitude lower than those of non-El Niño years. Therefore, a significant reduction of N2O efflux in the ETSP occurred during the 2015 El Niño event. At both offshore and coastal stations, the N2O concentration profiles during El Niño showed moderate N2O concentration gradients, and peak N2O concentrations were deeper than during non-El Niño years; this was likely the result of suppressed upwelling retaining N2O in subsurface waters. The depth-integrated N2O concentrations during El Niño were nearly twice as high as those measured in non-El Niño years, indicating subsurface N2O during El Niño could be a reservoir for intense N2O effluxes when normal upwelling is resumed after El Niño.

scholarly journals Investigating the effect of El Niño on nitrous oxide distribution in the eastern tropical South Pacific

2019 ◽  
Vol 16 (9) ◽  
pp. 2079-2093 ◽  
Author(s):  
Qixing Ji ◽  
Mark A. Altabet ◽  
Hermann W. Bange ◽  
Michelle I. Graco ◽  
Xiao Ma ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Water Column ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
South Pacific ◽  
Biological Properties ◽  
Nitrite Reduction ◽  
N2o Production ◽  
Near Surface

Abstract. The open ocean is a major source of nitrous oxide (N2O), an atmospheric trace gas attributable to global warming and ozone depletion. Intense sea-to-air N2O fluxes occur in major oceanic upwelling regions such as the eastern tropical South Pacific (ETSP). The ETSP is influenced by the El Niño–Southern Oscillation that leads to inter-annual variations in physical, chemical, and biological properties in the water column. In October 2015, a strong El Niño event was developing in the ETSP; we conduct field observations to investigate (1) the N2O production pathways and associated biogeochemical properties and (2) the effects of El Niño on water column N2O distributions and fluxes using data from previous non-El Niño years. Analysis of N2O natural abundance isotopomers suggested that nitrification and partial denitrification (nitrate and nitrite reduction to N2O) were occurring in the near-surface waters; indicating that both pathways contributed to N2O effluxes. Higher-than-normal sea surface temperatures were associated with a deepening of the oxycline and the oxygen minimum layer. Within the shelf region, surface N2O supersaturation was nearly an order of magnitude lower than that of non-El Niño years. Therefore, a significant reduction of N2O efflux (75 %–95 %) in the ETSP occurred during the 2015 El Niño. At both offshore and coastal stations, the N2O concentration profiles during El Niño showed moderate N2O concentration gradients, and the peak N2O concentrations occurred at deeper depths during El Niño years; this was likely the result of suppressed upwelling retaining N2O in subsurface waters. At multiple stations, water-column inventories of N2O within the top 1000 m were up to 160 % higher than those measured in non-El Niño years, indicating that subsurface N2O during El Niño could be a reservoir for intense N2O effluxes when normal upwelling is resumed after El Niño.

The Contribution of Boreal Spring South Pacific Atmospheric Variability to El Niño Occurrence

2020 ◽  
Vol 33 (19) ◽  
pp. 8301-8313
Author(s):  
Qingye Min ◽  
Renhe Zhang
Keyword(s):  
El Niño ◽  
El Nino ◽  
South Pacific ◽  
Tropical Pacific ◽  
The South ◽  
Atmospheric Variability ◽  
Boreal Spring ◽  
El Niño Events ◽  
El Nino Events ◽  
The Tropical Pacific

AbstractDespite the fact that great efforts have been made to improve the prediction of El Niño events, it remains challenging because of limited understanding of El Niño and its precursors. This research focuses on the influence of South Pacific atmospheric variability on the development of the sea surface temperature anomaly (SSTA) in the tropical Pacific. It is found that as early as in the boreal spring of El Niño years, the sea level pressure anomaly (SLPA) shows a configuration characterized by two significant negative anomaly centers in the north and a positive anomaly center in the south between the subtropics and high latitudes in South Pacific. Such an anomalous SLPA pattern becomes stronger in the following late boreal spring and summer associated with the strengthening of westerly anomalies in the tropical Pacific, weakening the southeasterly trade winds and promoting the warming of tropical eastern Pacific, which is conducive to the development of El Niño events. It is demonstrated that the SLPA pattern in boreal spring revealed in this study is closely associated with boreal summer South Pacific Oscillation (SPO) and South Pacific meridional mode (SPMM). As a precursor in boreal spring, the prediction skill of the South Pacific SLPA in boreal spring for the SSTA in the eastern equatorial Pacific is better than that of the SPMM. This study is helpful to deepen our understanding of the contribution of South Pacific extratropical atmospheric variability to El Niño occurrence.

scholarly journals Tropical Cyclone Climatology of the South Pacific Ocean and Its Relationship to El Niño–Southern Oscillation

2012 ◽  
Vol 25 (18) ◽  
pp. 6108-6122 ◽  
Author(s):  
Andrew J. Dowdy ◽  
Lixin Qi ◽  
David Jones ◽  
Hamish Ramsay ◽  
Robert Fawcett ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
El Niño ◽  
Large Scale ◽  
Critical Line ◽  
El Nino ◽  
Southern Oscillation ◽  
South Pacific ◽  
El Niño Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
The South

Abstract Climatological features of tropical cyclones in the South Pacific Ocean have been analyzed based on a new archive for the Southern Hemisphere. A vortex tracking and statistics package is used to examine features such as climatological maps of system intensity and the change in intensity with time, average tropical cyclone system movement, and system density. An examination is presented of the spatial variability of these features, as well as changes in relation to phase changes of the El Niño–Southern Oscillation phenomenon. A critical line is defined in this study based on maps of cyclone intensity to describe the statistical geographic boundary for cyclone intensification. During El Niño events, the critical line shifts equatorward, while during La Niña events the critical line is generally displaced poleward. Regional variability in tropical cyclone activity associated with El Niño–Southern Oscillation phases is examined in relation to the variability of large-scale atmospheric or oceanic variables associated with tropical cyclone activity. Maps of the difference fields between different phases of El Niño–Southern Oscillation are examined for sea surface temperature, vertical wind shear, lower-tropospheric vorticity, and midtropospheric relative humidity. Results are also examined in relation to the South Pacific convergence zone. The common region where each of the large-scale variables showed favorable conditions for cyclogenesis coincided with the location of maximum observed cyclogenesis for El Niño events as well as for La Niña years.

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