Trends and drivers in global surface ocean pH over the past 3 decades

Lauvset, Siv K.; Gruber, Nicolas; Landschützer, Peter; Olsen, Are; Tjiputra, Jerry

doi:10.5194/bg-12-1285-2015

Cited by 142 publications

(173 citation statements)

References 44 publications

Supporting

Mentioning

143

Contrasting

Order By: Relevance

“…2e, f . The trend in pH T is similar to the one found by Lauvset et al (2015) between 1991 and 2011 for the IO-STPS (Indian Ocean subtropical permanently stratified) biome (−0.0027 ± 0.0005 yr −1 ). We found a decrease in DIC π ∂DIC ∂t π = −0.34 ± 0.06 µmol kg −1 yr −1 , Table 5 in the STCW layer due to a negative trend of DIC π SAT resulting from a decrease in solubility that resulted from a temperature increase (calculated from the section data) in the STCW layer of 0.0335 ± 0.0130 • C yr −1 (not shown).…”

Section: Resultssupporting

confidence: 83%

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

et al. 2017

View full text Add to dashboard Cite

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.

show abstract

Section: Resultssupporting

confidence: 83%

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

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The annual increase also occurs against a background of large spatial variation of, for example, 140 µatm in different regions of the Southern Ocean in spring (Bakker et al, 2008; E. M. . Similarly, seasonal variation of 0.04 in surface pH in the subtropical North Atlantic Ocean (González-Dávila et al, 2007) is 20 times the mean annual decrease in surface ocean pH at a rate of −0.002 yr −1 Lauvset et al, 2015).…”

Section: Introductionmentioning

confidence: 94%

“…A number of studies estimate trends in surface ocean pH or the carbonate concentration by combining SOCAT f CO 2 values with another carbonate parameter (Lauvset and Gruber, 2014;Freeman and Lovenduski, 2015;Lauvset et al, 2015).…”

Section: Scientific Applications Of Socatmentioning

confidence: 99%

A multi-decade record of high-quality fCO2 data in version 3 of the Surface Ocean CO2 Atlas (SOCAT)

Bakker

Pfeil

Landa

et al. 2016

Earth Syst. Sci. Data

Self Cite

5,812

394

View full text Add to dashboard Cite

A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water f CO 2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. Highprofile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "living data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection Sabine et al., 2013;Bakker et al., 2014). Individual data set files, included in the synthesis product, can be downloaded here: doi:10.1594/PANGAEA.849770. The gridded products are available here:

show abstract

“…For pH(sst) we used the decomposition method described in Lauvset et al (2015) to quantify the importance of different parameters. This method estimates the monthly pH changes expected from corresponding changes observed in SST, SSS, DIC, and TA as well as their sum.…”

Section: Controls Of Seasonal Variability and Trendsmentioning

confidence: 99%

Aragonite saturation states and pH in western Norwegian fjords: seasonal cycles and controlling factors, 2005–2009

et al. 2016

Self Cite

View full text Add to dashboard Cite

Abstract. The uptake of anthropogenic carbon dioxide (CO2) by the ocean leads to a process known as ocean acidification (OA), which lowers the aragonite saturation state (ΩAr) and pH, and this is poorly documented in coastal environments including fjords due to lack of appropriate observations.Here we use weekly underway data from the Voluntary Observing Ships (VOS) program covering the period 2005–2009 combined with data from research cruises to estimate ΩAr and pH values in several adjacent western Norwegian fjords, and to evaluate how seawater CO2 chemistry drives their variations in response to physical and biological factors.The OA parameters in the surface waters of the fjords are subject to strong seasonal and spatially coherent variations. These changes are governed by the seasonal changes in temperature, salinity, formation and decay of organic matter, and vertical mixing with deeper, carbon-rich coastal water. Annual mean pH and ΩAr values were 8.13 and 2.21, respectively. The former varies from minimum values ( ≈  8.05) in late December – early January to maximum values of around 8.2 during early spring (March–April) as a consequence of the phytoplankton spring bloom, which reduces dissolved inorganic carbon (DIC). In the following months, pH decreases in response to warming. This thermodynamic decrease in pH is reinforced by the deepening of the mixed layer, which enables carbon-rich coastal water to reach the surface, and this trend continues until the low winter values of pH are reached again. ΩAr, on the other hand, reaches its seasonal maximum (> 2.5) in mid- to late summer (July–September), when the spring bloom is over and pH is decreasing. The lowest ΩAr values ( ≈  1.3–1.6) occur during winter (January–March), when both pH and sea surface temperature (SST) are low and DIC is its highest. Consequently, seasonal ΩAr variations align with those of SST and salinity normalized DIC (nDIC).We demonstrate that underway measurements of fugacity of CO2 in seawater (fCO2) and SST from VOS lines combined with high frequency observations of the complete carbonate system at strategically placed fixed stations provide an approach to interpolate OA parameters over large areas in the fjords of western Norway.

show abstract

Trends and drivers in global surface ocean pH over the past 3 decades

Cited by 142 publications

References 44 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

A multi-decade record of high-quality <i>f</i>CO<sub>2</sub> data in version 3 of the Surface Ocean CO<sub>2</sub> Atlas (SOCAT)

Aragonite saturation states and pH in western Norwegian fjords: seasonal cycles and controlling factors, 2005–2009

Contact Info

Product

Resources

About

Trends and drivers in global surface ocean pH over the past 3 decades

Cited by 142 publications

References 44 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

A multi-decade record of high-quality &lt;i&gt;f&lt;/i&gt;CO&lt;sub&gt;2&lt;/sub&gt; data in version 3 of the Surface Ocean CO&lt;sub&gt;2&lt;/sub&gt; Atlas (SOCAT)

Aragonite saturation states and pH in western Norwegian fjords: seasonal cycles and controlling factors, 2005–2009

Contact Info

Product

Resources

About

A multi-decade record of high-quality <i>f</i>CO<sub>2</sub> data in version 3 of the Surface Ocean CO<sub>2</sub> Atlas (SOCAT)