Mixed layer heat and salinity budgets during the onset of the 2011 Atlantic cold tongue

Schlundt, Michael; Brandt, Peter; Dengler, Marcus; Hummels, Rebecca; Fischer, Tim; Bumke, Karl; Krahmann, Gerd; Karstensen, Johannes

doi:10.1002/2014jc010021

Cited by 39 publications

(83 citation statements)

References 96 publications

(123 reference statements)

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“…Many uncertainties remain with respect to the exact mechanisms that lead to the development of the ACT. Jouanno et al (2011) suggested that the strong increase of the westward SEC associated with the ITCZ (Philander and Pacanowski, 1986), and the maximum shear above the core of the underlying EUC lead to the low SSTs, confirmed later by microstructure measurements (Hummels et al, 2013;Schlundt et al, 2014). Although the shear is maximal at 0 • E, maximum cooling appears at 10 • W due to the stronger stratification in the eastern basin of the equatorial Atlantic.…”

Section: Oceanographic Descriptionmentioning

confidence: 80%

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Halocarbon emissions and sources in the equatorial Atlantic Cold Tongue

et al. 2015

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Abstract.Halocarbons from oceanic sources contribute to halogens in the troposphere, and can be transported into the stratosphere where they take part in ozone depletion. This paper presents distribution and sources in the equatorial Atlantic from June and July 2011 of the four compounds bromoform (CHBr 3 ), dibromomethane (CH 2 Br 2 ), methyl iodide (CH 3 I) and diiodomethane (CH 2 I 2 ). Enhanced biological production during the Atlantic Cold Tongue (ACT) season, indicated by phytoplankton pigment concentrations, led to elevated concentrations of CHBr 3 of up to 44.7 and up to 9.2 pmol L −1 for CH 2 Br 2 in surface water, which is comparable to other tropical upwelling systems. While both compounds correlated very well with each other in the surface water, CH 2 Br 2 was often more elevated in greater depth than CHBr 3 , which showed maxima in the vicinity of the deep chlorophyll maximum. The deeper maximum of CH 2 Br 2 indicates an additional source in comparison to CHBr 3 or a slower degradation of CH 2 Br 2 . Concentrations of CH 3 I of up to 12.8 pmol L −1 in the surface water were measured. In contrary to expectations of a predominantly photochemical source in the tropical ocean, its distribution was mostly in agreement with biological parameters, indicating a biological source. CH 2 I 2 was very low in the near surface water with maximum concentrations of only 3.7 pmol L −1 . CH 2 I 2 showed distinct maxima in deeper waters similar to CH 2 Br 2 . For the first time, diapycnal fluxes of the four halocarbons from the upper thermocline into and out of the mixed layer were determined. These fluxes were low in comparison to the halocarbon sea-to-air fluxes. This indicates that despite the observed maximum concentrations at depth, production in the surface mixed layer is the main oceanic source for all four compounds and one of the main driving factors of their emissions into the atmosphere in the ACTregion. The calculated production rates of the compounds in the mixed layer are 34 ± 65 pmol m −3 h −1 for CHBr 3 , 10 ± 12 pmol m −3 h −1 for CH 2 Br 2 , 21 ± 24 pmol m −3 h −1 for CH 3 I and 384 ± 318 pmol m −3 h −1 for CH 2 I 2 determined from 13 depth profiles.

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Section: Oceanographic Descriptionmentioning

confidence: 80%

“…A more detailed description of the method to derive K dia and diapycnal fluxes below the mixed layer can be found in Schafstall et al (2010), Hummels et al (2013), and Schlundt et al (2014).…”

Section: Calculation Of Diapycnal Fluxes Of Halocarbonsmentioning

confidence: 99%

Halocarbon emissions and sources in the equatorial Atlantic Cold Tongue

et al. 2015

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“…Collection of discrete samples and water profiling were carried out by means of a Sea‐Bird 911 CTD/Rosette (Sea‐Bird Electronics, Inc., USA) equipped with 10 L Niskin bottles and double temperature, conductivity and oxygen (O 2 ) sensors. CTD‐derived salinity was calibrated against discrete samples which were analyzed on board by means of a Guildline Autosal salinometer [ Schlundt et al ., ]. Likewise, measured O 2 data were calibrated against discrete samples collected from the CTD/Rosette and that were analyzed on board following the Winkler method [ Hansen , ].…”

Section: Methods and Datamentioning

confidence: 99%

Nitrous oxide during the onset of the Atlantic cold tongue

et al. 2017

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The tropical Atlantic exerts a major influence in climate variability through strong air‐sea interactions. Within this region, the eastern side of the equatorial band is characterized by strong seasonality, whereby the most prominent feature is the annual development of the Atlantic cold tongue (ACT). This band of low sea surface temperatures (∼22–23°C) is typically associated with upwelling‐driven enhancement of surface nutrient concentrations and primary production. Based on a detailed investigation of the distribution and sea‐to‐air fluxes of N2O in the eastern equatorial Atlantic (EEA), we show that the onset and seasonal development of the ACT can be clearly observed in surface N2O concentrations, which increase progressively as the cooling in the equatorial region proceeds during spring‐summer. We observed a strong influence of the surface currents of the EEA on the N2O distribution, which allowed identifying “high” and “low” concentration regimes that were, in turn, spatially delimited by the extent of the warm eastward‐flowing North Equatorial Countercurrent and the cold westward‐flowing South Equatorial Current. Estimated sea‐to‐air fluxes of N2O from the ACT (mean 5.18 ± 2.59 μmol m−2 d−1) suggest that in May–July 2011 this cold‐water band doubled the N2O efflux to the atmosphere with respect to the adjacent regions, highlighting its relevance for marine tropical emissions of N2O.

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“…3b). At this time of the year the westward advection of Congo and Niger waters explains the freshening of the ACT until mid-June (Schlundt et al, 2014). The location of the mooring, between the salty southern waters and the ACT region, explains the high fCO 2 variability with values that could vary 20Á30 matm over a few days period (Fig.…”

Section: Seasonal Variability Of the Mooring Datamentioning

confidence: 89%

“…The opposite SEC and the intense Eastward Undercurrent (EUC) underneath generate vertical shear and intense mixing at the base of the mixed layer. This process is the main source of cooling for the ACT (Foltz et al, 2003;Wade et al, 2011;Giordani et al, 2013;Schlundt et al, 2014).…”

Section: Hydrological Variabilitymentioning

confidence: 99%

Variability and trends of carbon parameters at a time series in the eastern tropical Atlantic

Lefèvre¹,

Veleda²,

Araújo³

et al. 2016

Tellus B: Chemical and Physical Meteorology

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A B S T R A C THourly fCO 2 is recorded at a time series at the PIRATA buoy located at 68S 108W in the eastern tropical Atlantic since June 2006. This site is located south and west of the seasonal Atlantic cold tongue and is affected by its propagation from June to September. Using an alkalinityÁsalinity relationship determined for the eastern tropical Atlantic and the observed fCO 2 , pH and the inorganic carbon concentration are calculated. The time series is investigated to explore the intraseasonal, seasonal and interannual timescales for these parameters, and to detect any long-term trends. At intraseasonal timescales, fCO 2 and pH are strongly correlated. On seasonal timescales, the correlation still holds between fCO 2 and pH and their variations are in agreement with those of sea surface salinity. At interannual timescales, some important differences appear in 2011Á2012: lower fCO 2 and fluxes are observed from September to December 2011 and are explained by higher advection of salty waters at the mooring, in agreement with the wind. In early 2012, the anomaly is still present and associated with lower sea surface temperatures. No significant long-term trend is detected over the period 2006Á2013 on CO 2 and any other physical parameter. However, as atmospheric fCO 2 is increasing over time, the outgassing of CO 2 is reduced over the period 2006Á2013 as the flux is mainly controlled by the difference of fCO 2 between the ocean and the atmosphere. A longer time series is required to determine if any significant trend exists in this region.

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Mixed layer heat and salinity budgets during the onset of the 2011 Atlantic cold tongue

Cited by 39 publications

References 96 publications

Halocarbon emissions and sources in the equatorial Atlantic Cold Tongue

Halocarbon emissions and sources in the equatorial Atlantic Cold Tongue

Nitrous oxide during the onset of the Atlantic cold tongue

Variability and trends of carbon parameters at a time series in the eastern tropical Atlantic

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