Two decades of inorganic carbon dynamics along the West Antarctic Peninsula

Hauri, Claudine; Doney, Scott C.; Takahashi, Taro; Erickson, Michelle A.; Jiang, Guanghui; Ducklow, Hugh W.

doi:10.5194/bg-12-6761-2015

Cited by 36 publications

(75 citation statements)

References 78 publications

(88 reference statements)

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“…Across the WAP shelf, carbonate system parameters show strong onshore-offshore gradients in the upper ocean during summer, with low DIC and fCO 2 and high pH and aragonite saturation state in near-shore waters, due to strong biological carbon uptake, especially in the southern WAP subregion ( Figure 8) (Carrillo et al 2004;Hauri et al 2015;Ruiz-Halpern et al 2014). The degree of summertime DIC and fCO 2 drawdown is closely related to phytoplankton biomass and primary production (Moreau et al 2012), which are regulated by winter sea ice coverage and wind patterns during spring (Montes-Hugo et al 2010).…”

Section: Nutrient Biogeochemistrymentioning

confidence: 99%

Variability and change in the west Antarctic Peninsula marine system: Research priorities and opportunities

Henley

Schofield

Hendry

et al. 2019

Progress in Oceanography

106

112

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The west Antarctic Peninsula (WAP) region has undergone significant changes in temperature and seasonal ice dynamics since the mid-twentieth century, with strong impacts on the regional ecosystem, ocean chemistry and hydrographic properties. Changes to these long-term trends of warming and sea ice decline have been observed in the 21 st century, but their consequences for ocean physics, chemistry and the ecology of the high-productivity shelf ecosystem are yet to be fully established. The WAP shelf is important for regional krill stocks and higher trophic levels, whilst the degree of variability and change in the physical environment and documented biological and biogeochemical responses make this a model system for how climate and sea ice changes might restructure high-latitude ecosystems. Although this region is arguably the best-measured and bestunderstood shelf region around Antarctica, significant gaps remain in spatial and temporal data capable of resolving the atmosphere-ice-ocean-ecosystem feedbacks that control the dynamics and evolution of this complex polar system. Here we summarise the current state of knowledge regarding the key mechanisms and interactions regulating the physical, biogeochemical and biological processes at work, the ways in which the shelf environment is changing, and the ecosystem response to the changes underway. We outline the overarching cross-disciplinary priorities for future research, as well as the most important discipline-specific objectives. Underpinning these priorities and objectives is the need to better-define the causes, magnitude and timescales of variability and change at all levels of the system. A combination of traditional and innovative approaches will be critical to addressing these priorities and developing a coordinated observing system for the WAP shelf, which is required to detect and elucidate change into the future.

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Section: Nutrient Biogeochemistrymentioning

confidence: 99%

Variability and change in the west Antarctic Peninsula marine system: Research priorities and opportunities

Henley

Schofield

Hendry

et al. 2019

Progress in Oceanography

106

112

View full text Add to dashboard Cite

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“…DeVries et al (2017), used a global inverse model to postulate that changes in circulation are responsible for most of the variability in the oceanic CO 2 uptake, with the weakening of the upper-ocean circulation being responsible for the increase in oceanic carbon uptake over the past decade. Ocean acidification has been observed in the whole Southern Ocean and locally in the Atlantic and Pacific sectors (Williams et al, 2015;Hauri et al, 2015). South of Tasmania, McNeil et al (2001) reported an increase in C ANT uptake between 1968 and 1996 for the region 45-50 • S. These authors reported, for the first time, C ANT accumulation in the AABW and highlighted the importance of the formation of bottom and mode waters as a mechanism for transporting C ANT to the ocean.…”

Section: Introductionmentioning

confidence: 71%

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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“…Furthermore, in the relatively lower salinity waters of the 2011 mixed layer, the biological enhancement of saturation state significantly outweighed the decrease due to dilution. This is in contrast to observations in the Arctic Ocean, which have linked sea ice meltwater with surface freshening and depressed saturation states [e.g., Yamamoto‐Kawai et al ., ; Mathis et al ., ; Yamamoto‐Kawai et al ., ], but in broad agreement with recent studies of coastal systems in the West Antarctic Peninsula region [ Hauri et al ., ; Jones et al ., ]. If sea ice melt is associated with a source of dissolved iron (Fe) to the surface waters, this may stimulate biological productivity under otherwise Fe‐limited conditions, which are common in the open Southern Ocean and occur seasonally in the marginal ice zone [e.g., Sambrotto et al ., ; de Jong et al ., ].…”

Section: Discussionmentioning

confidence: 99%

Late‐summer biogeochemistry in the Mertz Polynya: East Antarctica

2017

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A marked reconfiguration of the Mertz Polynya following the 2010 calving of the Mertz Glacier Tongue has been associated with a decrease in the size and activity of the polynya. We report observations of the oceanic carbonate (CO2) system in late‐summer 2013, the third post‐calving summer season. Estimates of seasonal net community production (NCP) based on inorganic carbon deficits and the oxygen‐argon ratio indicate that the waters on the shelf to the east of Commonwealth Bay (adjacent to the Mertz Glacier) remain productive compared to pre‐calving conditions. The input of residual or excess alkalinity from melting sea ice is found to contribute to the seasonal enhancement of carbonate saturation state and pH in shelf waters. Mean rates of NCP in 2012–2013 are more than twice as large as those observed in the pre‐calving summers of 2001 and 2008 and suggest that the new (post‐calving) configuration of the polynya favors enhanced net community production and a stronger surface ocean sink for atmospheric CO2 due at least in part to the redistribution of sea ice and associated changes in summer surface stratification.

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Two decades of inorganic carbon dynamics along the West Antarctic Peninsula

Cited by 36 publications

References 78 publications

Variability and change in the west Antarctic Peninsula marine system: Research priorities and opportunities

Variability and change in the west Antarctic Peninsula marine system: Research priorities and opportunities

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

Late‐summer biogeochemistry in the Mertz Polynya: East Antarctica

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