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Arne Körtzinger - One of the best experts on this subject based on the ideXlab platform.

  • Anthropogenic CO2 accumulation rates in the north atlantic ocean from changes in the 13c 12c of dissolved inorganic carbon
    Global Biogeochemical Cycles, 2007
    Co-Authors: Paul D Quay, Rolf E Sonnerup, Arne Körtzinger, J Stutsman, J Maurer, X A Padin, Carol Robinson
    Abstract:

    [1] The Anthropogenic CO2 accumulation rate for the North Atlantic Ocean was estimated on the basis of the decrease in the δ13C of the dissolved inorganic carbon measured between cruises in 1981 (Transient Tracers in the North Atlantic), 1993 (OACES) and 2003 (Repeat Hydrography). A mean depth-integrated δ13C change of −15.0 ± 3.8‰ m yr−1 was estimated by applying a multiple linear regression approach to determine the Anthropogenic δ13C decrease at 22 stations where δ13C depth profiles were compared. The largest and deepest Anthropogenic δ13C decreases occurred in the subpolar ocean and, in contrast, the smallest and shallowest decreases occurred in the tropical ocean. A mean Anthropogenic CO2 accumulation rate of 0.63 ± 0.16 mol C m−2 yr−1 (0.32 ± 0.08 Pg C yr−1) in the North Atlantic Ocean over the last 20 years was determined from the mean depth-integrated δ13C change and a ratio of Anthropogenic δ13C to DIC change of −0.024‰ (μmol kg−1)−1. Only half of the accumulated Anthropogenic CO2 in the North Atlantic during the last 20 years was the result of air-sea CO2 uptake, based on a comparison of the air-sea 13CO2 flux to the DIC13 inventory change, with the other half likely a result of northward advective transport.

  • an estimate of Anthropogenic CO2 inventory from decadal changes in oceanic carbon content
    Proceedings of the National Academy of Sciences of the United States of America, 2007
    Co-Authors: Toste Tanhua, Arne Körtzinger, Darryn W Waugh, Karsten Friis, Douglas W R Wallace
    Abstract:

    Increased knowledge of the present global carbon cycle is important for our ability to understand and to predict the future carbon cycle and global climate. Approximately half of the Anthropogenic carbon released to the atmosphere from fossil fuel burning is stored in the ocean, although distribution and regional fluxes of the ocean sink are debated. Estimates of Anthropogenic carbon (Cant) in the oceans remain prone to error arising from (i) a need to estimate preindustrial reference concentrations of carbon for different oceanic regions, and (ii) differing behavior of transient ocean tracers used to infer Cant. We introduce an empirical approach to estimate Cant that circumvents both problems by using measurement of the decadal change of ocean carbon concentrations and the exponential nature of the atmospheric Cant increase. In contrast to prior approaches, the results are independent of tracer data but are shown to be qualitatively and quantitatively consistent with tracer-derived estimates. The approach reveals more Cant in the deep ocean than prior studies; with possible implications for future carbon uptake and deep ocean carbonate dissolution. Our results suggest that this approachs applied on the unprecedented global data archive provides a means of estimating the Cant for large parts of the world's ocean.

  • on the temporal increase of Anthropogenic CO2 in the subpolar north atlantic
    Deep Sea Research Part I: Oceanographic Research Papers 52 . pp. 681-698., 2005
    Co-Authors: Karsten Friis, Arne Körtzinger, Johannes Patsch, Douglas W R Wallace
    Abstract:

    Abstract The subpolar North Atlantic (NA) plays a key role in the oceanic uptake of Anthropogenic CO 2 . The availability of a historical high quality data set from the Transient Tracers in the Ocean North Atlantic Study (TTO-NAS) in 1981, together with data from recent studies in 1997 and 1999, makes it possible to assess the temporal increase of Anthropogenic CO 2 ( C T ant ) in the region. We introduce an extension of a previous published empirical approach for estimating temporal increases of C T ant , which is known as multiple linear regression approach (MLR). The method is based on a multiple linear-regression model employing hydrographic and chemical parameters. The accuracy of the extended MLR calculation (eMLR) proposed here is estimated to be ±3 μmol/kg for a parameterization based on potential temperature, total alkalinity, silicate, and phosphate. Calculated increases of C T ant ( Δ C T ant ( PO 4 ) ) for the time period 1981–1997 are 1–20 μmol/kg at depths greater than 100 m. The distribution corresponds well to silicate and CFC-12 distributions. Open ocean profiles show a relative minimum between 300 and 1000 m, which is not apparent in profiles of the total C T ant concentration. The Δ C T ant ( PO 4 ) inventory calculation for the northern NA region (40–65°N) yields a change in Anthropogenic CO 2 storage of 4.2 (±1) pg C over the 16-yr time period 1981–1997. This is equivalent to a mean annual C T ant increase of 0.27 (±0.06) pg C/yr or more than 10% of the global ocean uptake for this period.

  • relationship between Anthropogenic CO2 and the 13c suess effect in the north atlantic ocean
    Global Biogeochemical Cycles, 2003
    Co-Authors: Paul D Quay, Arne Körtzinger, Rolf E Sonnerup
    Abstract:

    [1] Temporal trends in oceanic dissolved inorganic carbon (DIC) and δ13C-DIC were reconstructed along five isopycnals in the upper 1000 m of the North Atlantic Ocean using a back-calculation approach. The mean Anthropogenic DIC increase was 1.21 ± 0.07 μmol kg−1 yr−1 and the mean 13C decrease was −0.026 ± 0.002‰ yr−1, both in good agreement with the results from previous studies. The observed δ13C-DIC perturbation ratio is −0.024 ± 0.003‰ (μmol kg−1)−1. Our results indicate that the North Atlantic is able to maintain equilibrium with the Anthropogenic perturbation for DIC and follows it with decadal time lag for δ13C. A CFC-calibrated one-dimensional isopycnal advection-diffusion model is used to evaluate temporal DIC and δ13C trends and perturbation ratios of the reconstructions. We investigate the time history of the air-sea CO2 and 13C disequilibria in the North Atlantic and discuss the importance of physical and biological processes in maintaining them. We find evidence that the North Atlantic Ocean is characterized by enhanced uptake of Anthropogenic CO2. Also, we use the model to examine how the time rate of change of δ13C depends on changes in the temporal evolution of δ13C in the atmosphere. The model evolution explains the curious result that the time rate of change of surface water δ13C in the North Atlantic Ocean can exceed that observed concurrently in the atmosphere. Finally we introduce a powerful way of estimating the global air-sea pCO2 disequilibrium based on the oceanic δ13C-DIC perturbation ratio.

  • Redfield ratios revisited: Removing the biasing effect of Anthropogenic CO2
    Limnology and Oceanography, 2001
    Co-Authors: Arne Körtzinger, John I. Hedges, Paul D Quay
    Abstract:

    Redfield ratios of remineralization are calculated based on chemical data analysis on isopycnal surfaces. The concentrations of dissolved inorganic carbon used in this study were corrected for the Anthropogenic CO2 content as estimated with a back-calculation technique. The corrections increased the apparent carbon remineralization by 25–30%, thus proving important for the reliable estimation of Redfield carbon ratios in the presence of Anthropogenic CO2. Best estimates from this study largely confirm the more recently published Redfield ratios of remineralization. The following results were obtained for the latitude range 3–41°N along 20–29±W in the Northeast Atlantic Ocean: Corg: P ratio = 123 ± 10; Corg : N ratio = 7.2 ± 0.8; —O2 :Corg ratio = 1.34 ± 0.06; —O2 : P ratio = 165 ± 15; N: P ratio = 17.5 ± 2.0. These ratios are in close agreement with the average composition of phytoplankton and represent respiration of organic matter consisting on average of 52% protein, 36% polysaccharide, and 12% lipid.

Nicolas Gruber - One of the best experts on this subject based on the ideXlab platform.

  • the oceanic sink for Anthropogenic CO2 from 1994 to 2007
    Science, 2019
    Co-Authors: Nicolas Gruber, Richard A Feely, Robert M Key, Mario Hoppema, Masao Ishii, D Clement, Brendan R Carter, Steven Van Heuven, Alex Kozyr
    Abstract:

    We quantify the oceanic sink for Anthropogenic carbon dioxide (CO 2 ) over the period 1994 to 2007 by using observations from the global repeat hydrography program and contrasting them to observations from the 1990s. Using a linear regression–based method, we find a global increase in the Anthropogenic CO 2 inventory of 34 ± 4 petagrams of carbon (Pg C) between 1994 and 2007. This is equivalent to an average uptake rate of 2.6 ± 0.3 Pg C year −1 and represents 31 ± 4% of the global Anthropogenic CO 2 emissions over this period. Although this global ocean sink estimate is consistent with the expectation of the ocean uptake having increased in proportion to the rise in atmospheric CO 2 , substantial regional differences in storage rate are found, likely owing to climate variability–driven changes in ocean circulation.

  • potential future coral habitats around japan depend strongly on Anthropogenic CO2 emissions
    2016
    Co-Authors: Nicolas Gruber, Yumiko Yara, Hiroya Yamano, Marco Steinacher, Masahiko Fujii, Meike Vogt, Yasuhiro Yamanaka
    Abstract:

    Using the results from the NCAR CSM1.4-coupled global carbon cycle–climate model under the Intergovernmental Panel on Climate Change (IPCC) emission scenarios SRES A2 and B1, we estimated the effects of both global warming and ocean acidification on the future habitats of corals in the seas around Japan during this century. As shown by Yara et al. (Biogeosciences 9:4955–4968, 2012), under the high-CO2-emission scenario (SRES A2), coral habitats will be sandwiched and narrowed between the northern region, where the saturation state of the carbonate mineral aragonite (Ωarag) decreases, and the southern region, where coral bleaching occurs. We found that under the low-emission scenario SRES B1, the coral habitats will also shrink in the northern region by the reduced Ωarag but to a lesser extent than under SRES A2, and in contrast to SRES A2, no bleaching will occur in the southern region. Therefore, coral habitats in the southern region are expected to be largely unaffected by ocean acidification or surface warming under the low-emission scenario. Our results show that potential future coral habitats depend strongly on CO2 emissions and emphasize the importance of reducing CO2 emissions to prevent negative impacts on coral habitats.

  • detecting Anthropogenic CO2 changes in the interior atlantic ocean between 1989 and 2005
    Journal of Geophysical Research, 2010
    Co-Authors: Rik Wanninkhof, Scott C Doney, John L Bullister, Naomi M Levine, Mark J Warner, Nicolas Gruber
    Abstract:

    [1] Repeat observations along the meridional Atlantic section A16 from Iceland to 56°S show substantial changes in the total dissolved inorganic carbon (DIC) concentrations in the ocean between occupations from 1989 through 2005. The changes correspond to the expected increase in DIC driven by the uptake of Anthropogenic CO2 from the atmosphere, but the ΔDIC is more varied and larger, in some locations, than can be explained solely by this process. Concomitant large changes in oxygen (O2) suggest that processes acting on the natural carbon cycle also contribute to ΔDIC. Precise partial pressure of CO2 measurements suggest small but systematic increases in the bottom waters. To isolate the Anthropogenic CO2 component (ΔCanthro) from ΔDIC, an extended multilinear regression approach is applied along isopycnal surfaces. This yields an average depth-integrated ΔCanthro of 0.53 ± 0.05 mol m−2 yr−1 with maximum values in the temperate zones of both hemispheres and a minimum in the tropical Atlantic. A higher decadal increase in the Anthropogenic CO2 inventory is found for the South Atlantic compared to the North Atlantic. This Anthropogenic CO2 accumulation pattern is opposite to that seen for the entire Anthropocene up to the 1990s. This change could perhaps be a consequence of the reduced downward transport of Anthropogenic CO2 in the North Atlantic due to recent climate variability. Extrapolating the results for this section to the entire Atlantic basin (63°N to 56°S) yields an uptake of 5 ± 1 Pg C decade−1, which corresponds to about 25% of the annual global ocean uptake of Anthropogenic CO2 during this period.

  • inverse estimates of Anthropogenic CO2 uptake transport and storage by the ocean
    Global Biogeochemical Cycles, 2006
    Co-Authors: Nicolas Gruber, Scott C Doney, Mikaloff Fletcher, A R Jacobson, Stephanie Dutkiewicz, Markus Gerber, Michael J Follows, Fortunat Joos, Keith Lindsay
    Abstract:

    deviation of the models weighted by a CFC-based model skill score, which reduces the error range and emphasizes those models that have been shown to reproduce observed tracer concentrations most accurately. The greatest Anthropogenic CO2 uptake occurs in the Southern Ocean and in the tropics. The flux estimates imply vigorous northward transport in the Southern Hemisphere, northward cross-equatorial transport, and equatorward transport at high northern latitudes. Compared with forward simulations, we find substantially more uptake in the Southern Ocean, less uptake in the Pacific Ocean, and less global uptake. The large-scale spatial pattern of the estimated flux is generally insensitive to possible biases in the data and the models employed. However, the global uptake scales approximately linearly with changes in the global Anthropogenic CO2 inventory. Considerable uncertainties remain in some regions, particularly the Southern Ocean.

  • the oceanic sink for Anthropogenic CO2
    Science, 2004
    Co-Authors: Christopher L Sabine, Richard A Feely, Rik Wanninkhof, Nicolas Gruber, Kitack Lee, Robert M Key, John L Bullister, C S Wong, Douglas W R Wallace, Bronte Tilbrook
    Abstract:

    Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic Anthropogenic carbon dioxide (CO2) sink for the period from 1800 to 1994 of 118 19 petagrams of carbon. The oceanic sink accounts for48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO 2 to the atmosphere of about 39 28 petagrams of carbon for this period. The current fraction of total Anthropogenic CO2 emissions stored in the ocean appears to be about one-third of the long-term potential. Since the beginning of the industrial period in the late 18th century, i.e., over the anthropocene (1), humankind has emitted large quantities of CO2 into the atmosphere, mainly as a result of fossil-fuel burning, but also because of land-use practices, e.g., deforestation (2). Measurements and reconstructions of the atmospheric CO2 history reveal, however, that less than half of these emissions remain in the atmosphere (3). The Anthropogenic CO2 that did not accumulate in the atmosphere must have been taken up by the ocean, by the land biosphere, or by a combination of both. The relative roles of the ocean and land biosphere as sinks for Anthropogenic CO2 over the anthropocene are currently not known. Although the Anthropogenic CO2 budget for the past two decades, i.e., the 1980s and 1990s, has been investigated in detail (3), the estimates of the ocean sink have not been based on direct measurements of changes in the oceanic inventory of dissolved inorganic carbon (DIC). Recognizing the need to constrain the oceanic uptake, transport, and storage of Anthropogenic CO 2 for the anthropocene and to provide a baseline for future estimates of oceanic CO 2 uptake, two international ocean research programs, the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS), jointly conducted a comprehensive survey of inorganic carbon distributions in the global ocean in the 1990s (4). After completion of the U.S. field program in 1998, a 5-year effort was begun to compile and rigorously quality-control the U.S. and international data sets, in

Christopher L Sabine - One of the best experts on this subject based on the ideXlab platform.

  • agreement of cmip5 simulated and observed ocean Anthropogenic CO2 uptake
    Geophysical Research Letters, 2017
    Co-Authors: Christopher L Sabine, Benjamin Bronselaer, Michael Winton, Joellen L Russell, Samar Khatiwala
    Abstract:

    NSF's Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) under NSF [PLR-1425989]; NOAA; NASA

  • decadal changes in the aragonite and calcite saturation state of the pacific ocean
    Global Biogeochemical Cycles, 2012
    Co-Authors: Richard A Feely, Andrew G. Dickson, Lisa A Miller, Robert H. Byrne, Akihiko Murata, Frank J. Millero, Rik Wanninkhof, Christopher L Sabine, Dana Greeley
    Abstract:

    [1] Based on measurements from the WOCE/JGOFS global CO2 survey, the CLIVAR/CO2 Repeat Hydrography Program and the Canadian Line P survey, we have observed an average decrease of 0.34% yr−1 in the saturation state of surface seawater in the Pacific Ocean with respect to aragonite and calcite. The upward migrations of the aragonite and calcite saturation horizons, averaging about 1 to 2 m yr−1, are the direct result of the uptake of Anthropogenic CO2 by the oceans and regional changes in circulation and biogeochemical processes. The shoaling of the saturation horizon is regionally variable, with more rapid shoaling in the South Pacific where there is a larger uptake of Anthropogenic CO2. In some locations, particularly in the North Pacific Subtropical Gyre and in the California Current, the decadal changes in circulation can be the dominant factor in controlling the migration of the saturation horizon. If CO2 emissions continue as projected over the rest of this century, the resulting changes in the marine carbonate system would mean that many coral reef systems in the Pacific would no longer be able to sustain a sufficiently high rate of calcification to maintain the viability of these ecosystems as a whole, and these changes perhaps could seriously impact the thousands of marine species that depend on them for survival.

  • estimation of Anthropogenic CO2 inventories in the ocean
    [Talk] In: International Carbon Dioxide Conference 8 14.-18.09 Jena ., 2009
    Co-Authors: Christopher L Sabine, Toste Tanhua
    Abstract:

    A significant impetus for recent ocean biogeochemical research has been to better understand the ocean's role as a sink for Anthropogenic CO2. In the 1990s the global carbon survey of the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS) inspired the development of several approaches for estimating Anthropogenic carbon inventories in the ocean interior. Most approaches agree that the total global ocean inventory of Cant was around 120 Pg C in the mid-1990s. Today, the ocean carbon uptake rate estimates suggest that the ocean is not keeping pace with the CO2 emissions growth rate. Repeat occupations of the WOCE/JGOFS survey lines consistently show increases in carbon inventories over the last decade, but have not yet been synthesized enough to verify a slowdown in the carbon storage rate. There are many uncertainties in the future ocean carbon storage. Continued observations are necessary to monitor changes and understand mechanisms controlling ocean carbon uptake and storage in the future.

  • the oceanic sink for Anthropogenic CO2
    Science, 2004
    Co-Authors: Christopher L Sabine, Richard A Feely, Rik Wanninkhof, Nicolas Gruber, Kitack Lee, Robert M Key, John L Bullister, C S Wong, Douglas W R Wallace, Bronte Tilbrook
    Abstract:

    Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic Anthropogenic carbon dioxide (CO2) sink for the period from 1800 to 1994 of 118 19 petagrams of carbon. The oceanic sink accounts for48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO 2 to the atmosphere of about 39 28 petagrams of carbon for this period. The current fraction of total Anthropogenic CO2 emissions stored in the ocean appears to be about one-third of the long-term potential. Since the beginning of the industrial period in the late 18th century, i.e., over the anthropocene (1), humankind has emitted large quantities of CO2 into the atmosphere, mainly as a result of fossil-fuel burning, but also because of land-use practices, e.g., deforestation (2). Measurements and reconstructions of the atmospheric CO2 history reveal, however, that less than half of these emissions remain in the atmosphere (3). The Anthropogenic CO2 that did not accumulate in the atmosphere must have been taken up by the ocean, by the land biosphere, or by a combination of both. The relative roles of the ocean and land biosphere as sinks for Anthropogenic CO2 over the anthropocene are currently not known. Although the Anthropogenic CO2 budget for the past two decades, i.e., the 1980s and 1990s, has been investigated in detail (3), the estimates of the ocean sink have not been based on direct measurements of changes in the oceanic inventory of dissolved inorganic carbon (DIC). Recognizing the need to constrain the oceanic uptake, transport, and storage of Anthropogenic CO 2 for the anthropocene and to provide a baseline for future estimates of oceanic CO 2 uptake, two international ocean research programs, the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS), jointly conducted a comprehensive survey of inorganic carbon distributions in the global ocean in the 1990s (4). After completion of the U.S. field program in 1998, a 5-year effort was begun to compile and rigorously quality-control the U.S. and international data sets, in

  • impact of Anthropogenic CO2 on the caco3 system in the oceans
    Science, 2004
    Co-Authors: Richard A Feely, Christopher L Sabine, Kitack Lee, William M Berelson, Joanie Kleypas, Victoria J Fabry, Frank J. Millero
    Abstract:

    Rising atmospheric carbon dioxide (CO 2 ) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed the saturation state ofthe oceans with respect to calcium carbonate (CaCO3) particles. 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. CaCO 3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO 3 dissolution rate for the global oceans is approximately 0.5 0.2 petagrams ofCaCO 3-C per year, which is approximately 45 to 65% ofthe export production ofCaCO 3 . Atmospheric CO 2 concentrations oscillated be

Keith Lindsay - One of the best experts on this subject based on the ideXlab platform.

  • carbon nitrogen interactions regulate climate carbon cycle feedbacks results from an atmosphere ocean general circulation model
    Biogeosciences, 2009
    Co-Authors: Peter E Thornton, Scott C Doney, Keith Lindsay, J K Moore, Natalie M Mahowald, J T Randerson, Inez Fung, Jeanfrancois Lamarque, Johannes J Feddema
    Abstract:

    Inclusion of fundamental ecological interactions between carbon and nitrogen cycles in the land component of an atmosphere-ocean general circulation model (AOGCM) leads to decreased carbon uptake associated with CO2 fertil- ization, and increased carbon uptake associated with warm- ing of the climate system. The balance of these two oppos- ing effects is to reduce the fraction of Anthropogenic CO2 predicted to be sequestered in land ecosystems. The primary mechanism responsible for increased land carbon storage un- der radiatively forced climate change is shown to be fertiliza- tion of plant growth by increased mineralization of nitrogen directly associated with increased decomposition of soil or- ganic matter under a warming climate, which in this partic- ular model results in a negative gain for the climate-carbon feedback. Estimates for the land and ocean sink fractions of recent Anthropogenic emissions are individually within the range of observational estimates, but the combined land plus ocean sink fractions produce an airborne fraction which is too high compared to observations. This bias is likely due in part to an underestimation of the ocean sink frac- tion. Our results show a significant growth in the airborne fraction of Anthropogenic CO2 emissions over the coming

  • impact of ocean carbon system variability on the detection of temporal increases in Anthropogenic CO2
    Journal of Geophysical Research, 2008
    Co-Authors: Naomi M Levine, Rik Wanninkhof, Scott C Doney, Keith Lindsay, Inez Fung
    Abstract:

    [1] Estimates of temporal trends in oceanic Anthropogenic carbon dioxide (CO2) rely on the ability of empirical methods to remove the large natural variability of the ocean carbon system. A coupled carbon-climate model is used to evaluate these empirical methods. Both the ΔC* and multiple linear regression (MLR) techniques reproduce the predicted increase in dissolved inorganic carbon for the majority of the ocean and have similar average percent errors for decadal differences (24.1% and 25.5%, respectively). However, this study identifies several regions where these methods may introduce errors. Of particular note are mode and deep water formation regions, where changes in air-sea disequilibrium and structure in the MLR residuals introduce errors. These results have significant implications for decadal repeat hydrography programs, indicating the need for subannual sampling in certain regions of the oceans in order to better constrain the natural variability in the system and to robustly estimate the intrusion of Anthropogenic CO2.

  • inverse estimates of Anthropogenic CO2 uptake transport and storage by the ocean
    Global Biogeochemical Cycles, 2006
    Co-Authors: Nicolas Gruber, Scott C Doney, Mikaloff Fletcher, A R Jacobson, Stephanie Dutkiewicz, Markus Gerber, Michael J Follows, Fortunat Joos, Keith Lindsay
    Abstract:

    deviation of the models weighted by a CFC-based model skill score, which reduces the error range and emphasizes those models that have been shown to reproduce observed tracer concentrations most accurately. The greatest Anthropogenic CO2 uptake occurs in the Southern Ocean and in the tropics. The flux estimates imply vigorous northward transport in the Southern Hemisphere, northward cross-equatorial transport, and equatorward transport at high northern latitudes. Compared with forward simulations, we find substantially more uptake in the Southern Ocean, less uptake in the Pacific Ocean, and less global uptake. The large-scale spatial pattern of the estimated flux is generally insensitive to possible biases in the data and the models employed. However, the global uptake scales approximately linearly with changes in the global Anthropogenic CO2 inventory. Considerable uncertainties remain in some regions, particularly the Southern Ocean.

  • evolution of carbon sinks in a changing climate
    Proceedings of the National Academy of Sciences of the United States of America, 2005
    Co-Authors: Inez Fung, Scott C Doney, Keith Lindsay, Jasmin G John
    Abstract:

    Climate change is expected to influence the capacities of the land and oceans to act as repositories for Anthropogenic CO2 and hence provide a feedback to climate change. A series of experiments with the National Center for Atmospheric Research–Climate System Model 1 coupled carbon–climate model shows that carbon sink strengths vary with the rate of fossil fuel emissions, so that carbon storage capacities of the land and oceans decrease and climate warming accelerates with faster CO2 emissions. Furthermore, there is a positive feedback between the carbon and climate systems, so that climate warming acts to increase the airborne fraction of Anthropogenic CO2 and amplify the climate change itself. Globally, the amplification is small at the end of the 21st century in this model because of its low transient climate response and the near-cancellation between large regional changes in the hydrologic and ecosystem responses. Analysis of our results in the context of comparable models suggests that destabilization of the tropical land sink is qualitatively robust, although its degree is uncertain.

Douglas W R Wallace - One of the best experts on this subject based on the ideXlab platform.

  • ventilation of the arctic ocean mean ages and inventories of Anthropogenic CO2 and cfc 11
    Journal of Geophysical Research, 2009
    Co-Authors: Toste Tanhua, Douglas W R Wallace, Peter E Jones, Emil Jeansson, Sara Jutterstrom, William M Smethie, Leif G Anderson
    Abstract:

    The Arctic Ocean constitutes a large body of water that is still relatively poorly surveyed because of logistical difficulties, although the importance of the Arctic Ocean for global circulation and climate is widely recognized. For instance, the concentration and inventory of Anthropogenic CO2 (C ant) in the Arctic Ocean are not properly known despite its relatively large volume of well-ventilated waters. In this work, we have synthesized available transient tracer measurements (e.g., CFCs and SF6) made during more than two decades by the authors. The tracer data are used to estimate the ventilation of the Arctic Ocean, to infer deep-water pathways, and to estimate the Arctic Ocean inventory of C ant. For these calculations, we used the transit time distribution (TTD) concept that makes tracer measurements collected over several decades comparable with each other. The bottom water in the Arctic Ocean has CFC values close to the detection limit, with somewhat higher values in the Eurasian Basin. The ventilation time for the intermediate water column is shorter in the Eurasian Basin (∼200 years) than in the Canadian Basin (∼300 years). We calculate the Arctic Ocean C ant inventory range to be 2.5 to 3.3 Pg-C, normalized to 2005, i.e., ∼2% of the global ocean C ant inventory despite being composed of only ∼1% of the global ocean volume. In a similar fashion, we use the TTD field to calculate the Arctic Ocean inventory of CFC-11 to be 26.2 ± 2.6 × 106 moles for year 1994, which is ∼5% of the global ocean CFC-11 inventory

  • use of sf6 to estimate Anthropogenic CO2 in the upper ocean
    Journal of Geophysical Research, 2008
    Co-Authors: Toste Tanhua, Darryn W Waugh, Douglas W R Wallace
    Abstract:

    [1] The highest concentrations of Anthropogenic carbon (Cant) are found in the upper layers of the world ocean. However, this is where seasonal variability of inorganic carbon and related parameters due to thermal and biological effects complicates use of back-calculation approaches for Cant. Tracer based approaches to Cant estimation are unaffected by biological variability and have found wide application. However, slow-down, even reversal, of the atmospheric growth of chlorofluorocarbons (CFCs) restricts use of these tracers for Cant estimation for waters ventilated since the mid 1990s. Here we apply SF6, a tracer that continues to increase in the atmosphere, as a basis for the Cant estimation, using samples collected in the midlatitude North Atlantic in 2004. Cant estimates derived from water mass transit time distributions (TTDs) calculated with SF6 are compared to those based on CFC-12. For recently ventilated waters (pCFC-12 > ∼450 ppt), the uncertainty of SF6 based estimates of Cant is ∼6 μmol kg−1 less than that of CFC-12 based estimates. CFC-12 based estimates remain more reliable for older (deeper) water masses, as a result of the longer input history and more readily detectable concentrations of CFC-12. Historical data suggest that the near-surface saturation of CFC-12 has increased over time, in inverse proportion to its atmospheric growth rate. Use of a time-dependent saturation of CFC-12 in TTD calculations appears to provide more reliable estimation of Cant.

  • an estimate of Anthropogenic CO2 inventory from decadal changes in oceanic carbon content
    Proceedings of the National Academy of Sciences of the United States of America, 2007
    Co-Authors: Toste Tanhua, Arne Körtzinger, Darryn W Waugh, Karsten Friis, Douglas W R Wallace
    Abstract:

    Increased knowledge of the present global carbon cycle is important for our ability to understand and to predict the future carbon cycle and global climate. Approximately half of the Anthropogenic carbon released to the atmosphere from fossil fuel burning is stored in the ocean, although distribution and regional fluxes of the ocean sink are debated. Estimates of Anthropogenic carbon (Cant) in the oceans remain prone to error arising from (i) a need to estimate preindustrial reference concentrations of carbon for different oceanic regions, and (ii) differing behavior of transient ocean tracers used to infer Cant. We introduce an empirical approach to estimate Cant that circumvents both problems by using measurement of the decadal change of ocean carbon concentrations and the exponential nature of the atmospheric Cant increase. In contrast to prior approaches, the results are independent of tracer data but are shown to be qualitatively and quantitatively consistent with tracer-derived estimates. The approach reveals more Cant in the deep ocean than prior studies; with possible implications for future carbon uptake and deep ocean carbonate dissolution. Our results suggest that this approachs applied on the unprecedented global data archive provides a means of estimating the Cant for large parts of the world's ocean.

  • on the temporal increase of Anthropogenic CO2 in the subpolar north atlantic
    Deep Sea Research Part I: Oceanographic Research Papers 52 . pp. 681-698., 2005
    Co-Authors: Karsten Friis, Arne Körtzinger, Johannes Patsch, Douglas W R Wallace
    Abstract:

    Abstract The subpolar North Atlantic (NA) plays a key role in the oceanic uptake of Anthropogenic CO 2 . The availability of a historical high quality data set from the Transient Tracers in the Ocean North Atlantic Study (TTO-NAS) in 1981, together with data from recent studies in 1997 and 1999, makes it possible to assess the temporal increase of Anthropogenic CO 2 ( C T ant ) in the region. We introduce an extension of a previous published empirical approach for estimating temporal increases of C T ant , which is known as multiple linear regression approach (MLR). The method is based on a multiple linear-regression model employing hydrographic and chemical parameters. The accuracy of the extended MLR calculation (eMLR) proposed here is estimated to be ±3 μmol/kg for a parameterization based on potential temperature, total alkalinity, silicate, and phosphate. Calculated increases of C T ant ( Δ C T ant ( PO 4 ) ) for the time period 1981–1997 are 1–20 μmol/kg at depths greater than 100 m. The distribution corresponds well to silicate and CFC-12 distributions. Open ocean profiles show a relative minimum between 300 and 1000 m, which is not apparent in profiles of the total C T ant concentration. The Δ C T ant ( PO 4 ) inventory calculation for the northern NA region (40–65°N) yields a change in Anthropogenic CO 2 storage of 4.2 (±1) pg C over the 16-yr time period 1981–1997. This is equivalent to a mean annual C T ant increase of 0.27 (±0.06) pg C/yr or more than 10% of the global ocean uptake for this period.

  • the oceanic sink for Anthropogenic CO2
    Science, 2004
    Co-Authors: Christopher L Sabine, Richard A Feely, Rik Wanninkhof, Nicolas Gruber, Kitack Lee, Robert M Key, John L Bullister, C S Wong, Douglas W R Wallace, Bronte Tilbrook
    Abstract:

    Using inorganic carbon measurements from an international survey effort in the 1990s and a tracer-based separation technique, we estimate a global oceanic Anthropogenic carbon dioxide (CO2) sink for the period from 1800 to 1994 of 118 19 petagrams of carbon. The oceanic sink accounts for48% of the total fossil-fuel and cement-manufacturing emissions, implying that the terrestrial biosphere was a net source of CO 2 to the atmosphere of about 39 28 petagrams of carbon for this period. The current fraction of total Anthropogenic CO2 emissions stored in the ocean appears to be about one-third of the long-term potential. Since the beginning of the industrial period in the late 18th century, i.e., over the anthropocene (1), humankind has emitted large quantities of CO2 into the atmosphere, mainly as a result of fossil-fuel burning, but also because of land-use practices, e.g., deforestation (2). Measurements and reconstructions of the atmospheric CO2 history reveal, however, that less than half of these emissions remain in the atmosphere (3). The Anthropogenic CO2 that did not accumulate in the atmosphere must have been taken up by the ocean, by the land biosphere, or by a combination of both. The relative roles of the ocean and land biosphere as sinks for Anthropogenic CO2 over the anthropocene are currently not known. Although the Anthropogenic CO2 budget for the past two decades, i.e., the 1980s and 1990s, has been investigated in detail (3), the estimates of the ocean sink have not been based on direct measurements of changes in the oceanic inventory of dissolved inorganic carbon (DIC). Recognizing the need to constrain the oceanic uptake, transport, and storage of Anthropogenic CO 2 for the anthropocene and to provide a baseline for future estimates of oceanic CO 2 uptake, two international ocean research programs, the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS), jointly conducted a comprehensive survey of inorganic carbon distributions in the global ocean in the 1990s (4). After completion of the U.S. field program in 1998, a 5-year effort was begun to compile and rigorously quality-control the U.S. and international data sets, in