On the variability in the CO2 system and water productivity in the western tropical Atlantic off North and Northeast Brazil

Araújo, Moacyr; Noriega, Carlos; Medeiros, Carmen; Lefèvre, Nathalie; Ibánhez, J. Severino P.; Montes, Manuel F.; Silva, Alex Costa da; Santos, Maria de Lourdes Souza

doi:10.1016/j.jmarsys.2018.09.008

Cited by 17 publications

(32 citation statements)

References 72 publications

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“…of 18 drawdown is mainly driven by the physical solubility pump, which has already been suggested as the main driver of pCO 2 changes in this sub-region (Araujo et al, 2018). This is more evident when TA and DIC are normalized to SSS, revealing that pCO 2 drawdown is almost counteracted by the increase in SST, which decreases the CO 2 solubility.…”

Section: Of 18mentioning

confidence: 61%

“…For instance, if global CO 2 emissions are cut to net zero by around 2050, in the most optimistic scenario (SSP1‐1.9), the NEC sub‐region would switch to releasing instead of taking up CO 2 and NBC‐NECC would double its CO 2 outgassing in approximately 20 years, assuming the current sea surface p CO 2 trend. However, it remains difficult to predict an accurate response of the marine carbonate system to different scenarios, because sea‐air CO 2 exchanges are an important driver for sea surface p CO 2 in these sub‐regions (e.g., Araujo et al., 2018). In any case, the increase in sea surface p CO 2 can further lead to changes in seawater pH and hence affect the extensive reef system at the Amazon River mouth along the continental shelf (Moura et al., 2016), which is highly sensitive to changes in biogeochemical conditions (Francini‐Filho et al., 2018; Neumann‐Leitão et al., 2018).…”

Section: Discussionmentioning

confidence: 99%

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Contrasting Sea‐Air CO₂ Exchanges in the Western Tropical Atlantic Ocean

Monteiro

Batista

Henley

et al. 2022

Global Biogeochemical Cycles

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The western Tropical Atlantic Ocean is a biogeochemically complex region due to the structure of the surface current system and the large freshwater input from the Amazon River coupled with the dynamics of precipitation. Such features make it difficult to understand the dynamics of the carbon cycle, leading to contrasting estimates in sea‐air CO2 exchanges in this region. Here, we demonstrate that these contrasting estimates occur because the western Tropical Atlantic Ocean can be split into three distinct sub‐regions in terms of the sea‐air CO2 exchanges. The sub‐region under the North Brazil Current domain acts as a weak annual CO2 source to the atmosphere, with low interannual variability. The sub‐region under the North Equatorial Current influence acts as an annual CO2 sink, with great temporal variability. The third sub‐region under the Amazon River plume influence shows greater interannual variability of CO2 exchanges, but it always acts as a net oceanic sink for CO2. Despite this large spatial variability, the entire region acts as a net annual CO2 sink of −1.6 ± 1.0 mmol m−2 day−1. Importantly, the Amazon River plume waters drive 87% of the CO2 uptake in the western Tropical Atlantic Ocean. In addition, we found a significant increasing trend in sea surface CO2 partial pressure in the North Brazil Current and North Equatorial Current waters. Such trends are more pronounced than the increase in atmospheric CO2 partial pressure, revealing the sensitivity of carbon dynamics in these sub‐regions to global climate change.

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Section: Of 18mentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Contrasting Sea‐Air CO₂ Exchanges in the Western Tropical Atlantic Ocean

Monteiro

Batista

Henley

et al. 2022

Global Biogeochemical Cycles

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“…Previous studies have not investigated the trends in pCO 2 or CO 2 flux in the Amazon plume; however, the carbon retention in a coloured ocean site (CARI-ACO), situated to the northwest, displayed positive trends in pCO 2 (sw) of 2.95 ± 0.43 µatm yr −1 (Bates et al, 2014). Araujo et al (2019) identified a positive trend in pCO 2 (sw) of 1.20 µatm yr −1 but a trend in pCO 2 (atm) of 1.70 µatm yr −1 (i.e. decreasing pCO 2 ) for the northeast Brazilian coast, although the air-sea CO 2 flux and pCO 2 within the Amazon plume region are spatially and temporally variable (Valerio et al, 2021;Ibánhez et al, 2016;Bruto et al, 2017).…”

Section: Multi-year Trends In Pco 2 and Co 2 Fluxmentioning

confidence: 95%

Identifying the biological control of the annual and multi-year variations in South Atlantic air–sea CO₂ flux

et al. 2022

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Abstract. The accumulation of anthropogenic CO2 emissions in the atmosphere has been buffered by the absorption of CO2 by the global ocean, which acts as a net CO2 sink. The CO2 flux between the atmosphere and the ocean, which collectively results in the oceanic carbon sink, is spatially and temporally variable, and fully understanding the driving mechanisms behind this flux is key to assessing how the sink may change in the future. In this study a time series decomposition analysis was applied to satellite observations to determine the drivers that control the sea–air difference of CO2 partial pressure (ΔpCO2) and the CO2 flux on seasonal and inter-annual timescales in the South Atlantic Ocean. Linear trends in ΔpCO2 and the CO2 flux were calculated to identify key areas of change. Seasonally, changes in both the ΔpCO2 and CO2 flux were dominated by sea surface temperature (SST) in the subtropics (north of 40∘ S) and were correlated with biological processes in the subpolar regions (south of 40∘ S). In the equatorial Atlantic, analysis of the data indicated that biological processes are likely a key driver as a response to upwelling and riverine inputs. These results highlighted that seasonally ΔpCO2 can act as an indicator to identify drivers of the CO2 flux. Inter-annually, the SST and biological contributions to the CO2 flux in the subtropics were correlated with the multivariate El Niño–Southern Oscillation (ENSO) index (MEI), which leads to a weaker (stronger) CO2 sink in El Niño (La Niña) years. The 16-year time series identified significant trends in ΔpCO2 and CO2 flux; however, these trends were not always consistent in spatial extent. Therefore, predicting the oceanic response to climate change requires the examination of CO2 flux rather than ΔpCO2. Positive CO2 flux trends (weakening sink for atmospheric CO2) were identified within the Benguela upwelling system, consistent with increased upwelling and wind speeds. Negative trends in the CO2 flux (intensifying sink for atmospheric CO2) offshore into the South Atlantic gyre were consistent with an increase in the export of nutrients from mesoscale features, which drives the biological drawdown of CO2. These multi-year trends in the CO2 flux indicate that the biological contribution to changes in the air–sea CO2 flux cannot be overlooked when scaling up to estimates of the global ocean carbon sink.

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“…Some field studies on the productivity of this tropical coast reported the oligotrophic conditions of the region (Knoppers et al, 1999;Souza et al, 2013;Jales et al, 2015;Carvalho et al, 2017;Araujo et al, 2019). Nevertheless, the presence of reef formations in oligotrophic seas is a particularly important source of nonuniformity within the coastal biome (Van Duyl et al, 2002;Longhurst, 2007;Racault et al, 2015;Cotovicz et al, 2020).…”

Section: Ocean and Coastal Researchmentioning

confidence: 98%

Distribution of nutrients and chlorophyll across an equatorial reef region: Insights on coastal gradients

et al. 2023

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On the variability in the CO2 system and water productivity in the western tropical Atlantic off North and Northeast Brazil

Cited by 17 publications

References 72 publications

Contrasting Sea‐Air CO₂ Exchanges in the Western Tropical Atlantic Ocean

Contrasting Sea‐Air CO₂ Exchanges in the Western Tropical Atlantic Ocean

Identifying the biological control of the annual and multi-year variations in South Atlantic air–sea CO₂ flux

Distribution of nutrients and chlorophyll across an equatorial reef region: Insights on coastal gradients

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On the variability in the CO2 system and water productivity in the western tropical Atlantic off North and Northeast Brazil

Cited by 17 publications

References 72 publications

Contrasting Sea‐Air CO2 Exchanges in the Western Tropical Atlantic Ocean

Contrasting Sea‐Air CO2 Exchanges in the Western Tropical Atlantic Ocean

Identifying the biological control of the annual and multi-year variations in South Atlantic air–sea CO2 flux

Distribution of nutrients and chlorophyll across an equatorial reef region: Insights on coastal gradients

Contact Info

Product

Resources

About

Contrasting Sea‐Air CO₂ Exchanges in the Western Tropical Atlantic Ocean

Contrasting Sea‐Air CO₂ Exchanges in the Western Tropical Atlantic Ocean

Identifying the biological control of the annual and multi-year variations in South Atlantic air–sea CO₂ flux