AGW Observer

Papers on ocean acidification


This is a list of papers on ocean acidification with emphasis on reduction of ocean pH due to rising atmospheric carbon dioxide concentration. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

UPDATE (November 16, 2012): Byrne et al. (2010) and Bates et al. (2012) added.
UPDATE (September 13, 2010): Feely et al. (2008) added.
UPDATE (April 7, 2010): Pelejero et al. (2010) added.

Detecting anthropogenic carbon dioxide uptake and ocean acidification in the North Atlantic Ocean – Bates et al. (2012) “Fossil fuel use, cement manufacture and land-use changes are the primary sources of anthropogenic carbon dioxide (CO2) to the atmosphere, with the ocean absorbing approximately 30% (Sabine et al., 2004). Ocean uptake and chemical equilibration of anthropogenic CO2 with seawater results in a gradual reduction in seawater pH and saturation states (Ω) for calcium carbonate (CaCO3) minerals in a process termed ocean acidification. Assessing the present and future impact of ocean acidification on marine ecosystems requires detection of the multi-decadal rate of change across ocean basins and at ocean time-series sites. Here, we show the longest continuous record of ocean CO2 changes and ocean acidification in the North Atlantic subtropical gyre near Bermuda from 1983–2011. Dissolved inorganic carbon (DIC) and partial pressure of CO2 (pCO2) increased in surface seawater by ~40 μmol kg−1 and ~50 μatm (~20%), respectively. Increasing Revelle factor (β) values imply that the capacity of North Atlantic surface waters to absorb CO2 has also diminished. As indicators of ocean acidification, seawater pH decreased by ~0.05 (0.0017 yr−1) and ω values by ~7–8%. Such data provide critically needed multi-decadal information for assessing the North Atlantic Ocean CO2 sink and the pH changes that determine marine ecosystem responses to ocean acidification.” Bates, N. R., Best, M. H. P., Neely, K., Garley, R., Dickson, A. G., and Johnson, R. J.: Detecting anthropogenic carbon dioxide uptake and ocean acidification in the North Atlantic Ocean, Biogeosciences, 9, 2509-2522, doi:10.5194/bg-9-2509-2012, 2012. [Full text]

Paleo-perspectives on ocean acidification – Pelejero et al. (2010) “The anthropogenic rise in atmospheric CO2 is driving fundamental and unprecedented changes in the chemistry of the oceans. This has led to changes in the physiology of a wide variety of marine organisms and, consequently, the ecology of the ocean. This review explores recent advances in our understanding of ocean acidification with a particular emphasis on past changes to ocean chemistry and what they can tell us about present and future changes. We argue that ocean conditions are already more extreme than those experienced by marine organisms and ecosystems for millions of years, emphasising the urgent need to adopt policies that drastically reduce CO2 emissions.” Carles Pelejero, Eva Calvo, Ove Hoegh-Guldberg, Trends in Ecology & Evolution, Volume 25, Issue 6, 332-344, 30 March 2010, DOI: 10.1016/j.tree.2010.02.002. [Full text, John Cook’s article on this paper]

Direct observations of basin-wide acidification of the North Pacific Ocean – Byrne et al. (2010) “Global ocean acidification is a prominent, inexorable change associated with rising levels of atmospheric CO2. Here we present the first basin-wide direct observations of recently declining pH, along with estimates of anthropogenic and non-anthropogenic contributions to that signal. Along 152°W in the North Pacific Ocean (22–56°N), pH changes between 1991 and 2006 were essentially zero below about 800 m depth. However, in the upper 500 m, significant pH changes, as large as −0.06, were observed. Anthropogenic and non-anthropogenic contributions over the upper 800 m are estimated to be of similar magnitude. In the surface mixed layer (depths to ∼100 m), the extent of pH change is consistent with that expected under conditions of seawater/atmosphere equilibration, with an average rate of change of −0.0017/yr. Future mixed layer changes can be expected to closely mirror changes in atmospheric CO2, with surface seawater pH continuing to fall as atmospheric CO2 rises.” Byrne, R. H., S. Mecking, R. A. Feely, and X. Liu (2010), Direct observations of basin-wide acidification of the North Pacific Ocean, Geophys. Res. Lett., 37, L02601, doi:10.1029/2009GL040999. [Full text]

Physical and biogeochemical modulation of ocean acidification in the central North Pacific – Dore et al. (2009) “Here we report the results of nearly 20 years of time-series measurements of seawater pH and associated parameters at Station ALOHA in the central North Pacific Ocean near Hawaii. We document a significant long-term decreasing trend of −0.0019 ± 0.0002 y−1 in surface pH, which is indistinguishable from the rate of acidification expected from equilibration with the atmosphere.” [Full text]

Ocean Acidification: The Other CO2 Problem – Doney et al. (2009) A review paper. “Rising atmospheric carbon dioxide (CO2), primarily from human fossil fuel combustion, reduces ocean pH and causes wholesale shifts in seawater carbonate chemistry. The process of ocean acidification is well documented in field data, and the rate will accelerate over this century unless future CO2 emissions are curbed dramatically. Acidification alters seawater chemical speciation and biogeochemical cycles of many elements and compounds. One well-known effect is the lowering of calcium carbonate saturation states, which impacts shell-forming marine organisms from plankton to benthic molluscs, echinoderms, and corals.” [Full text]

Dynamic patterns and ecological impacts of declining ocean pH in a high-resolution multi-year dataset – Wootton et al. (2008) “In a high-resolution dataset spanning 8 years, pH at a north-temperate coastal site declined with increasing atmospheric CO2 levels and varied substantially in response to biological processes and physical conditions that fluctuate over multiple time scales.” [Full text]

Evidence for Upwelling of Corrosive “Acidified” Water onto the Continental Shelf – Feely et al. (2008) “The absorption of atmospheric carbon dioxide (CO2) into the ocean lowers the pH of the waters. This so-called ocean acidification could have important consequences for marine ecosystems. To better understand the extent of this ocean acidification in coastal waters, we conducted hydrographic surveys along the continental shelf of western North America from central Canada to northern Mexico. We observed seawater that is undersaturated with respect to aragonite upwelling onto large portions of the continental shelf, reaching depths of 40 to 120 meters along most transect lines and all the way to the surface on one transect off northern California. Although seasonal upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic CO2 has increased the areal extent of the affected area.” Richard A. Feely, Christopher L. Sabine, J. Martin Hernandez-Ayon, Debby Ianson, Burke Hales, Science 13 June 2008: Vol. 320. no. 5882, pp. 1490 – 1492, DOI: 10.1126/science.1155676. [Full text]

Southern Ocean acidification: A tipping point at 450-ppm atmospheric CO2 – McNeil & Matear (2008) “We present a large-scale Southern Ocean observational analysis that examines the seasonal magnitude and variability of CO32− and pH. Our analysis shows an intense wintertime minimum in CO32− south of the Antarctic Polar Front and when combined with anthropogenic CO2 uptake is likely to induce aragonite undersaturation when atmospheric CO2 levels reach ≈450 ppm.” [Full text]

pH variability and CO2 induced acidification in the North Sea – Blackford & Gilbert (2007) A model study. “Annual pH ranges are found to vary from 1.0 in areas influenced by riverine signals, consistent with observations and previous studies. It is shown that benthic, as well as pelagic, activity is an important factor in this variability. The acidification of the region due to increased fluxes of atmospheric CO2 into the marine system is calculated and shown to exceed, on average, 0.1 pH units over the next 50 years and result in a total acidification of 0.5 pH units below pre-industrial levels at atmospheric CO2 concentrations of 1000 ppm.”

The interannual variability of oceanic CO2 parameters in the northeast Atlantic subtropical gyre at the ESTOC site – Santana-Casiano et al. (2007) Reports pH measurements (among other parameters) from a single location. “Our series of experimental pHT data confirm the acidification of surface waters in the east Atlantic Ocean, with an interannual decrease of 0.0017 ± 0.0004 pH units yr−1.” [Full text]

Interannual variability of the oceanic CO2 sink in the subtropical gyre of the North Atlantic Ocean over the last 2 decades – Bates (2007) While concentrating on oceanic CO2 sink measurements, reports pH measurements from a single location. “In addition, seawater pH, CO32- ion concentrations, and CaCO3 saturation states have also decreased over time.” [Full text]

Experimental measurement of boron isotope fractionation in seawater – Klochko et al. (2006) “The boron isotopic composition of marine carbonates is considered to be a tracer of seawater pH. Use of this proxy benefits from an intimate understanding of chemical kinetics and thermodynamic isotope exchange reactions between the two dominant boron-bearing species in seawater: boric acid B(OH)3 and borate ion B(OH)4. However, because of our inability to quantitatively separate these species in solution, the degree of boron isotope exchange has only been known through theoretical estimates. In this study, we present results of a spectrophotometric procedure wherein the boron isotope equilibrium constant (11–10KB) is determined empirically” [Full text]

Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms – Orr et al. (2005) A model study. “Here we use 13 models of the ocean–carbon cycle to assess calcium carbonate saturation under the IS92a ‘business-as-usual’ scenario for future emissions of anthropogenic carbon dioxide. … Our findings indicate that conditions detrimental to high-latitude ecosystems could develop within decades, not centuries as suggested previously.” [Full text]

Ocean acidification due to increasing atmospheric carbon dioxide – Raven et al. (2005) The Royal Society report. “Evidence indicates that emissions of carbon dioxide from human activities over the past 200 years have already led to a reduction in the average pH of surface seawater of 0.1 units and could fall by 0.5 units by the year 2100. This pH is probably lower than has been experienced for hundreds of millennia and, critically, at a rate of change probably 100 times greater than at any time over this period.” [Full text]

Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans – Feely et al. (2004) “Here we estimate the in situ CaCO3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO2 on CaCO3 shell–forming species. CaCO3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon.” [Full text]

Anthropogenic carbon and ocean pH – Caldeira & Wickett (2003) A model study. “Here we quantify the changes in ocean pH that may result from this continued release of CO2 and compare these with pH changes estimated from geological and historical records. We find that oceanic absorption of CO2 from fossil fuels may result in larger pH changes over the next several centuries than any inferred from the geological record of the past 300 million years, with the possible exception of those resulting from rare, extreme events such as bolide impacts or catastrophic methane hydrate degassing.” [Full text]

The role of pHT measurements in marine CO2-system characterizations – Byrne et al. (1999) “In this work, using the NOAA 1992 boreal autumn Equatorial Pacific (EqPac) dataset, it is shown that CO2-system variables calculated via pHT can be used to enhance both the precision and accuracy of directly measured parameters. Through the procedures described in this work significant problems were revealed in the initial version of the 1992 NOAA dataset, and the dataset was greatly improved.”

The role of pH measurements in modern oceanic CO2-system characterizations: Precision and thermodynamic consistency – Clayton et al. (1995) “In May 1992, surface seawater samples were collected along an equatorial transit (130 to 100°W) and analyzed for total hydrogen ion concentration (expressed as spectrophotometric pHT) total dissolved inorganic carbon (coulometric CT), and total alkalinity (potentiometric AT and spectrophotometric AT). … In light of recent advances, the role of pH measurements in CO2-system characterizations should be re-evaluated. Spectrophotometric measurements of pH have much to contribute in documenting the oceans’ evolving response to anthropogenic C02.”

Closely related

Ocean acidification – A blog devoted to the subject.