Reconstruction of the history of anthropogenic CO2 concentrations in the ocean

Khatiwala, S.; Primeau, François; Hall, Tim

doi:10.1038/nature08526

Cited by 580 publications

(680 citation statements)

References 38 publications

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“…Sabine and Tanhua, 2009;Khatiwala et al, 2009Khatiwala et al, , 2012. The methods of quantifying these changes require a means to separate natural and climate-induced changes in ocean inorganic carbon from that caused by the penetration of anthropogenic CO 2 from the atmosphere (Gruber et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Changes in deep-water CO2 concentrations over the last several decades determined from discrete pCO2measurements

Wanninkhof

Park

Takahashi

et al. 2013

Deep Sea Research Part I: Oceanographic Research Papers

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a b s t r a c tDetection and attribution of hydrographic and biogeochemical changes in the deep ocean are challenging due to the small magnitude of their signals and to limitations in the accuracy of available data. However, there are indications that anthropogenic and climate change signals are starting to manifest at depth. The deep ocean below 2000 m comprises about 50% of the total ocean volume, and changes in the deep ocean should be followed over time to accurately assess the partitioning of anthropogenic carbon dioxide (CO 2 ) between the ocean, terrestrial biosphere, and atmosphere. Here we determine the changes in the interior deep-water inorganic carbon content by a novel means that uses the partial pressure of CO 2 measured at 20 1C, pCO 2 (20), along three meridional transects in the Atlantic and Pacific oceans. These changes are measured on decadal time scales using observations from the World Ocean Circulation Experiment (WOCE)/World Hydrographic Program (WHP) of the 1980s and 1990s and the CLIVAR/CO 2 Repeat Hydrography Program of the past decade. The pCO 2 (20) values show a consistent increase in deep water over the time period. Changes in total dissolved inorganic carbon (DIC) content in the deep interior are not significant or consistent, as most of the signal is below the level of analytical uncertainty. Using an approximate relationship between pCO 2 (20) and DIC change, we infer DIC changes that are at the margin of detectability. However, when integrated on the basin scale, the increases range from 8-40% of the total specific water column changes over the past several decades. Patterns in chlorofluorocarbons (CFCs), along with output from an ocean model, suggest that the changes in pCO 2 (20) and DIC are of anthropogenic origin.Published by Elsevier Ltd.

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Section: Introductionmentioning

confidence: 99%

Changes in deep-water CO2 concentrations over the last several decades determined from discrete pCO2measurements

Wanninkhof

Park

Takahashi

et al. 2013

Deep Sea Research Part I: Oceanographic Research Papers

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“…Over the past few decades, the southern oceans have warmed at roughly twice the rate of the global mean ocean (1), and around 40% of the anthropogenic carbon in the oceans entered south of 40°S (4). Southern ocean ventilation is driven primarily by the westerly winds (5), which have strengthened and shifted poleward over recent decades, primarily as a consequence of Antarctic stratospheric ozone depletion (6).…”

mentioning

confidence: 99%

Recent Changes in the Ventilation of the Southern Oceans

Waugh

Primeau

DeVries

et al. 2013

Science

150

166

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Surface westerly winds in the Southern Hemisphere have intensified over the past few decades, primarily in response to the formation of the Antarctic ozone hole, and there is intense debate on the impact of this on the ocean's circulation and uptake and redistribution of atmospheric gases. We used measurements of chlorofluorocarbon-12 (CFC-12) made in the southern oceans in the early 1990s and mid-to late 2000s to examine changes in ocean ventilation. Our analysis of the CFC-12 data reveals a decrease in the age of subtropical subantarctic mode waters and an increase in the age of circumpolar deep waters, suggesting that the formation of the Antarctic ozone hole has caused large-scale coherent changes in the ventilation of the southern oceans.T he transport of surface waters into the interior ("ventilation") of the southern oceans plays an important role in global climate and the cycling of carbon, oxygen, and nutrients in the oceans (1-3). Over the past few decades, the southern oceans have warmed at roughly twice the rate of the global mean ocean (1), and around 40% of the anthropogenic carbon in the oceans entered south of 40°S (4). Southern ocean ventilation is driven primarily by the westerly winds (5), which have strengthened and shifted poleward over recent decades, primarily as a consequence of Antarctic stratospheric ozone depletion (6). Modeling studies suggest that this has caused changes in the ocean's overturning circulation (7-9), and carbon uptake (10, 11). However, the sensitivity of the southern ocean circulation and ventilation to decadal changes in wind stresses is under debate (12)(13)(14).Information on ventilation rates can be obtained from measurements of chlorofluorocarbons (CFCs). These compounds are conserved within the oceans, and their atmospheric concentrations have increased rapidly from when they were first produced in the 1930s until the mid1990s ( fig. S1). Because of this time dependence, CFC measurements can provide constraints on the rates and pathways of ocean transport (15, 16).We used CFC-12 measurements made along several sections in the southern oceans in the early 1990s as part of the World Ocean Circulation Experiment (WOCE) and resampled in mid-to late 2000s as part of the Climate Variability and Predictability (CLIVAR) and CO 2 repeat hydrography program (supplementary materials) to examine changes in the ventilation of the southern oceans over the past two decades.The measurements during WOCE show largest pCFC-12 at the surface, with values decreasing with depth along isopycnals (e.g., Fig. 1A). [We express the measurements as the partial pressure of CFC-12 ( pCFC-12), defined as the seawater concentration divided by the solubility (16). This enables direct comparison with the atmospheric history of CFC-12.] The repeat occupations 14 to 16 years later show large increases in pCFC-12 in the subtropical thermocline (~25°t o 45°S, 200 to 1000 m), which correspond to the waters formed by the transport of surface waters along surfaces of constant density (e.g., Fig. 1B). ...

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“…57 and 59 are widely used to quantify the ventilation rate of the ocean (e.g., England 1995; Haine and Hall 2002;Deleersnijder et al 2002). In practice, the modeling results may, however, be strongly dependent on the thickness of the surface layer and other boundary conditions can be considered (e.g., Khatiwala et al 2009;DeVries and Primeau 2010).…”

Section: Diagnosis Of the Ventilation Of The Deep Oceanmentioning

confidence: 99%

“…The appropriate framework is therefore five-dimensional, i.e., space × time × age (Bolin and Rodhe 1973;Hall and Plumb 1994;Delhez et al 1999;Ginn 1999;Haine and Hall 2002). While special techniques can be used to work in this five-dimensional space Cornaton 2012), this complexity is avoided in most Eulerian studies by resorting to the steady state hypothesis (e.g., Holzer and Hall 2000;Khatiwala et al 2009) or by considering only the mean value of the ages of the particles in a water parcel.…”

Section: Introductionmentioning

confidence: 99%

Partial ages: diagnosing transport processes by means of multiple clocks

Mouchet

Cornaton²,

Deleersnijder

et al. 2016

Ocean Dynamics

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The concept of age is widely used to quantify the transport rate of tracers -or pollutants -in the environment. The age focuses only on the time taken to reach a given location and disregards other aspects of the path followed by the tracer parcel. To keep track of the subregions visited by the tracer parcel along this path, partial ages are defined as the time spent in the different subregions. Partial ages can

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Reconstruction of the history of anthropogenic CO2 concentrations in the ocean

Cited by 580 publications

References 38 publications

Changes in deep-water CO2 concentrations over the last several decades determined from discrete pCO2measurements

Changes in deep-water CO2 concentrations over the last several decades determined from discrete pCO2measurements

Recent Changes in the Ventilation of the Southern Oceans

Partial ages: diagnosing transport processes by means of multiple clocks

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