Estimating carbonate parameters from hydrographic data for the intermediate and deep waters of the Southern Hemisphere oceans

Bostock, Helen C.; Fletcher, S. E. Mikaloff; Williams, Michael

doi:10.5194/bg-10-6199-2013

Cited by 40 publications

(40 citation statements)

References 59 publications

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“…Another feature that agrees with the hypothesis of upwelling intensification is the shoaling of the ASD following the path of upwelling of the UCDW layer. This feature was also described by Bostock et al (2013) in an oceanic climatology of Ar and could be due to the naturally lower buffer capacity of the UCDW layer (low value of TA / DIC ≈ 1.043) with respect to upper layers (TA / DIC ≈ 1.06 in the AASW layer). However, the greatest shoaling of the ASD in the UCDW layers compared to the AAIW layer (Table 6) is consistent with the upwelling of UCDW, as both water masses have similar TA / DIC ratios (TA / DIC ≈ 1.043 for the UCDW layer and TA / DIC ≈ 1.042 for the AAIW layer).…”

Section: Discussionsupporting

confidence: 56%

Carbon uptake and biogeochemical change in the Southern Ocean, south of Tasmania

et al. 2017

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Abstract. Biogeochemical change in the water masses of the Southern Ocean, south of Tasmania, was assessed for the 16-year period between 1995 and 2011 using data from four summer repeats of the WOCE-JGOFS-CLIVAR-GO-SHIP (Key et al., 2015;Olsen et al., 2016) SR03 hydrographic section (at ∼ 140 • E). Changes in temperature, salinity, oxygen, and nutrients were used to disentangle the effect of solubility, biology, circulation and anthropogenic carbon (C ANT ) uptake on the variability of dissolved inorganic carbon (DIC) for eight water mass layers defined by neutral surfaces (γ n ). C ANT was estimated using an improved back-calculation method. Warming (∼ 0.0352 ± 0.0170 • C yr −1 ) of Subtropical Central Water (STCW) and Antarctic Surface Water (AASW) layers decreased their gas solubility, and accordingly DIC concentrations increased less rapidly than expected from equilibration with rising atmospheric CO 2 (∼ 0.86 ± 0.16 µmol kg −1 yr −1 versus ∼ 1 ± 0.12 µmol kg −1 yr −1 ). An increase in apparent oxygen utilisation (AOU) occurred in these layers due to either remineralisation of organic matter or intensification of upwelling. The range of estimates for the increases in C ANT were 0.71 ± 0.08 to 0.93 ± 0.08 µmol kg −1 yr −1 for STCW and 0.35 ± 0.14 to 0.65 ± 0.21 µmol kg −1 yr −1 for AASW, with the lower values in each water mass obtained by assigning all the AOU change to remineralisation. DIC increases in the Sub-Antarctic Mode Water (SAMW, 1.10 ± 0.14 µmol kg −1 yr −1 ) and Antarctic Intermediate Water (AAIW, 0.40 ± 0.15 µmol kg −1 yr −1 ) layers were similar to the calculated C ANT trends. For SAMW, the C ANT increase tracked rising atmospheric CO 2 . As a consequence of the general DIC increase, decreases in total pH (pH T ) and aragonite saturation ( Ar ) were found in most water masses, with the upper ocean and the SAMW layer presenting the largest trends for pH T decrease (∼ −0.0031 ± 0.0004 yr −1 ). DIC increases in deep and bottom layers (∼ 0.24 ± 0.04 µmol kg −1 yr −1 ) resulted from the advection of old deep waters to resupply increased upwelling, as corroborated by increasing silicate (∼ 0.21 ± 0.07 µmol kg −1 yr −1 ), which also reached the upper layers near the Antarctic Divergence (∼ 0.36 ± 0.06 µmol kg −1 yr −1 ) and was accompanied by an increase in salinity. The observed changes in DIC over the 16-year span caused a shoaling (∼ 340 m) of the aragonite saturation depth (ASD, Ar = 1) within Upper Circumpolar Deep Water that followed the upwelling path of this layer. From all our results, we conclude a scenario of increased transport of deep waters into the section and enhanced upwelling at high latitudes for the period between 1995 and 2011 linked to strong westerly winds. Although enhanced upwelling lowered the capacity of the AASW layer to uptake atmospheric CO 2 , it did not limit that of the newly forming SAMW and AAIW, which exhibited C ANT storage rates (∼ 0.41 ± 0.20 mol m −2 yr −1 ) twice that of the upper layers.

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Section: Discussionsupporting

confidence: 56%

Carbon uptake and biogeochemical change in the Southern Ocean, south of Tasmania

et al. 2017

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“…It has been shown that such algorithms often fail in coastal waters due to the strong influence that coastal processes 15 have on the distribution of TA (Bostock et al, 2013;Cai et al, 2010). Our results confirmed that such open ocean models are not necessarily optimal for predicting TA in coastal waters and their use can result in large systematic errors in some regions (Fig.…”

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confidence: 81%

“…dissolved organic inputs and 35 biological processes such as calcification and organic matter production). Thus, these relationships may not be robust in coastal regions (Bostock et al, 2013;Cai et al, 2010).…”

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confidence: 99%

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Estimating total alkalinity for coastal ocean acidification monitoring at regional to continental scales in Australian coastal waters

Baldry

Hardman-Mountford

Greenwood

2017

Preprint

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Abstract.Owing to a lack of resources, tools, and knowledge, the natural variability and distribution of Total Alkalinity (TA) has been poorly characterised in coastal waters globally, yet variability is known to be high in coastal regions due to the complex interactions of oceanographic, biotic, and terrestrially-influenced processes. This is a 5 particularly challenging task for the vast Australian coastline, however, it is also this vastness that demands attention in the face of ocean acidification (OA). Australian coastal waters have high biodiversity and endemism, and are home to large areas of coral reef, including the Great Barrier Reef, the largest coral reef system in the world. Ocean acidification threatens calcifying marine organisms by hindering calcification rates, Biogeosciences Discuss.,

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“…Previous studies have used multiple linear regression models (MLR) to estimate inorganic carbon variables from hydrographic measurements (Juranek et al, 2009(Juranek et al, , 2011Kim et al, 2010;Alin et al, 2012;Bostock et al, 2013;Williams et al, 2016;Carter et al, 2017). These were applied to different data sets (hydrographic surveys, time-series, profiling floats, climatology) in order to reconstruct estimates of the natural variability of carbon variables.…”

Section: Introductionmentioning

confidence: 99%

Can Empirical Algorithms Successfully Estimate Aragonite Saturation State in the Subpolar North Atlantic?

et al. 2017

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The aragonite saturation state ( Ar ) in the subpolar North Atlantic was derived using new regional empirical algorithms. These multiple regression algorithms were developed using the bin-averaged GLODAPv2 data of commonly observed oceanographic variables [temperature (T), salinity (S), pressure (P), oxygen (O 2 ), nitrate (NO − 3 ), phosphate (PO 3− 4 ), silicate (Si(OH) 4 ), and pH]. Five of these variables are also frequently observed using autonomous platforms, which means they are widely available. The algorithms were validated against independent shipboard data from the OVIDE2012 cruise. It was also applied to time series observations of T, S, P, and O 2 from the K1 mooring (56.5 • N, 52.6 • W) to reconstruct for the first time the seasonal variability of Ar . Our study suggests: (i) linear regression algorithms based on bin-averaged carbonate system data can successfully estimate Ar in our study domain over the 0-3,500 m depth range (R 2 = 0.985, RMSE = 0.044); (ii) that Ar also can be adequately estimated from solely non-carbonate observations (R 2 = 0.969, RMSE = 0.063) and autonomous sensor variables (R 2 = 0.978, RMSE = 0.053). Validation with independent OVIDE2012 data further suggests that; (iii) both algorithms, non-carbonate (MEF = 0.929) and autonomous sensors (MEF = 0.995) have excellent predictive skill over the 0-3,500 depth range; (iv) that in deep waters (>500 m) observations of T, S, and O 2 may be sufficient predictors of Ar (MEF = 0.913); and (iv) the importance of adding pH sensors on autonomous platforms in the euphotic and remineralization zone (<500 m). Reconstructed Ar at Irminger Sea site, and the K1 mooring in Labrador Sea show high seasonal variability at the surface due to biological drawdown of inorganic carbon during the summer, and fairly uniform Ar values in the water column during winter convection. Application to time series sites shows the potential for regionally tuned algorithms, but they need to be further compared against Ar calculated by conventional means to fully assess their validity and performance.

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Estimating carbonate parameters from hydrographic data for the intermediate and deep waters of the Southern Hemisphere oceans

Cited by 40 publications

References 59 publications

Carbon uptake and biogeochemical change in the Southern Ocean, south of Tasmania

Carbon uptake and biogeochemical change in the Southern Ocean, south of Tasmania

Estimating total alkalinity for coastal ocean acidification monitoring at regional to continental scales in Australian coastal waters

Can Empirical Algorithms Successfully Estimate Aragonite Saturation State in the Subpolar North Atlantic?

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