Aragonite Undersaturation in the Arctic Ocean: Effects of Ocean Acidification and Sea Ice Melt

Yamamoto‐Kawai, Michiyo; McLaughlin, Fiona A.; Carmack, Eddy C.; Nishino, Shigeto; Shimada, Koji

doi:10.1126/science.1174190

Cited by 305 publications

(264 citation statements)

References 26 publications

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“…These low saturation zones will be associated with increased melting of ice and freshwater inputs leading to a decrease in total alkalinity [7]. Undersaturated conditions have already been found in near coastal waters under the influence of heavy freshwater influence [38]. Temperate latitudes showed large absolute changes in V a , in the Atlantic (site 4, from V a ¼ 3.7 in 1860 to V a ¼ 1.9 in 2095) as well as in the Pacific (site 9, from V a ¼ 3.6 in 1860 to V a ¼ 1.7 in 2095).…”

Section: Discussionmentioning

confidence: 99%

Impact of aragonite saturation state changes on migratory pteropods

et al. 2011

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Thecosome pteropods play a key role in the food web of various marine ecosystems and they calcify, secreting the unstable CaCO 3 mineral aragonite to form their shell material. Here, we have estimated the effect of ocean acidification on pteropod calcification by exploiting empirical relationships between their gross calcification rates (CaCO 3 precipitation) and aragonite saturation state V a , combined with model projections of future V a . These were corrected for modern model-data bias and taken over the depth range where pteropods are observed to migrate vertically. Results indicate large reductions in gross calcification at temperate and high latitudes. Over much of the Arctic, the pteropod Limacina helicina will become unable to precipitate CaCO 3 by the end of the century under the IPCC SRES A2 scenario. These results emphasize concerns over the future of shelled pteropods, particularly L. helicina in high latitudes. Shell-less L. helicina are not known to have ever existed nor would we expect them to survive. Declines of pteropod populations could drive dramatic ecological changes in the various pelagic ecosystems in which they play a critical role.

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Section: Discussionmentioning

confidence: 99%

Impact of aragonite saturation state changes on migratory pteropods

et al. 2011

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“…In surface waters, is lower in cold, high-latitude oceans than in tropical and temperate oceans because of increased CO 2 solubility, the sensitivity of acid-base dissociation coefficients at cold temperatures, and ocean mixing patterns. Although surface waters in high-latitude oceans today are generally supersaturated with respect to aragonite (aragonite is more soluble than calcite), recent studies have reported undersaturated seawater in the Canada Basin of the Arctic Ocean (Yamamoto-Kawai et al, 2009;Bates et al, 2009). From the modeling projections, small regions of surface water in the Arctic Ocean may already be undersaturated with respect to aragonite (Gangstø et al, 2008) or will become undersaturated within a decade under the A2 Scenario of the Special Report on Emissions Scenarios (SRES-A2) (Steinacher et al, 2009;Frölicher and Joos, 2010).…”

Section: A Yamamoto Et Al: Impact Of Rapid Sea-ice Reduction In Thementioning

confidence: 99%

Impact of rapid sea-ice reduction in the Arctic Ocean on the rate of ocean acidification

et al. 2012

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Abstract. The largest pH decline and widespread undersaturation with respect to aragonite in this century due to uptake of anthropogenic carbon dioxide in the Arctic Ocean have been projected. The reductions in pH and aragonite saturation state in the Arctic Ocean have been caused by the melting of sea ice as well as by an increase in the concentration of atmospheric carbon dioxide. Therefore, future projections of pH and aragonite saturation in the Arctic Ocean will be affected by how rapidly the reduction in sea ice occurs. The observed recent Arctic sea-ice loss has been more rapid than projected by many of the climate models that contributed to the Intergovernmental Panel on Climate Change Fourth Assessment Report. In this study, the impact of sea-ice reduction rate on projected pH and aragonite saturation state in the Arctic surface waters was investigated. Reductions in pH and aragonite saturation were calculated from the outputs of two versions of an Earth system model with different sea-ice reduction rates under similar CO 2 emission scenarios. The newer model version projects that Arctic summer ice-free condition will be achieved by the year 2040, and the older version predicts ice-free condition by 2090. The Arctic surface water was projected to be undersaturated with respect to aragonite in the annual mean when atmospheric CO 2 concentration reaches 513 (606) ppm in year 2046 (2056) in new (old) version. At an atmospheric CO 2 concentration of 520 ppm, the maximum differences in pH and aragonite saturation state between the two versions were 0.1 and 0.21 respectively. The analysis showed that the decreases in pH and aragonite saturation state due to rapid sea-ice reduction were caused by increases in both CO 2 uptake and freshwater input. Thus, the reductions in pH and aragonite saturation state in the Arctic surface waters are significantly affected by the difference in future projections for sea-ice reduction rate. Our results suggest that the future reductions in pH and aragonite saturation state could be significantly faster than previously projected if the sea-ice reduction in the Arctic Ocean keeps its present pace.

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“…Model calculations (Orr et al 2005) indicate that a decrease in carbonate mineral saturation states is occurring throughout the global open ocean and will impact the polar oceans first (Orr et al 2005). During the summer of 2008, the Canada Basin of the Arctic Ocean was undersaturated with respect to aragonite (Yamamoto-Kawai et al 2009). …”

Section: Current Trends In Open-ocean and Coastal Phmentioning

confidence: 99%

Is Ocean Acidification an Open-Ocean Syndrome? Understanding Anthropogenic Impacts on Seawater pH

Duarte

Hendriks

Moore

et al. 2013

Estuaries and Coasts

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Ocean acidification due to anthropogenic CO 2 emissions is a dominant driver of long-term changes in pH in the open ocean, raising concern for the future of calcifying organisms, many of which are present in coastal habitats. However, changes in pH in coastal ecosystems result from a multitude of drivers, including impacts from watershed processes, nutrient inputs, and changes in ecosystem structure and metabolism. Interaction between ocean acidification due to anthropogenic CO 2 emissions and the dynamic regional to local drivers of coastal ecosystems have resulted in complex regulation of pH in coastal waters. Changes in the watershed can, for example, lead to changes in alkalinity and CO 2 fluxes that, together with metabolic processes and oceanic dynamics, yield high-magnitude decadal changes of up to 0.5 units in coastal pH. Metabolism results in strong diel to seasonal fluctuations in pH, with characteristic ranges of 0.3 pH units, with metabolically intense habitats exceeding this range on a daily basis. The intense variability and multiple, complex controls on pH implies that the concept of ocean acidification due to anthropogenic CO 2 emissions cannot be transposed to coastal ecosystems directly. Furthermore, in coastal ecosystems, the detection of trends towards acidification is not trivial and the attribution of these changes to anthropogenic CO 2 emissions is even more problematic. Coastal ecosystems may show acidification or basification, depending on the balance between the invasion of coastal waters by anthropogenic CO 2 , watershed export of alkalinity, organic matter and CO 2 , and changes in the balance between primary production, respiration and calcification rates in response to changes in nutrient inputs and losses of ecosystem components. Hence, we contend that ocean acidification from anthropogenic CO 2 is largely an open-ocean syndrome and that a concept of anthropogenic impacts on marine pH, which is applicable across the entire ocean, from coastal to open-ocean environments, provides a superior framework to consider the multiple components of the anthropogenic perturbation of marine pH trajectories. The concept of anthropogenic impacts on seawater pH acknowledges that a regional focus is necessary to predict future trajectories in the pH of coastal waters and points at opportunities to manage these trajectories locally to conserve coastal organisms vulnerable to ocean acidification.

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Aragonite Undersaturation in the Arctic Ocean: Effects of Ocean Acidification and Sea Ice Melt

Cited by 305 publications

References 26 publications

Impact of aragonite saturation state changes on migratory pteropods

Impact of aragonite saturation state changes on migratory pteropods

Impact of rapid sea-ice reduction in the Arctic Ocean on the rate of ocean acidification

Is Ocean Acidification an Open-Ocean Syndrome? Understanding Anthropogenic Impacts on Seawater pH

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