Alain Poisson

Bio: Alain Poisson is an academic researcher from Pierre-and-Marie-Curie University. The author has contributed to research in topics: Thermohaline circulation & Polar front. The author has an hindex of 31, co-authored 63 publications receiving 5321 citations. Previous affiliations of Alain Poisson include University of Perpignan & Université du Québec à Rimouski.

Global sea-air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects

Abstract: Based on about 940,000 measurements of surface-water pCO2 obtained since the International Geophysical Year of 1956–59, the climatological, monthly distribution of pCO2 in the global surface waters representing mean non-El Nino conditions has been obtained with a spatial resolution of 4°×5° for a reference year 1995. The monthly and annual net sea–air CO2 flux has been computed using the NCEP/NCAR 41-year mean monthly wind speeds. An annual net uptake flux of CO2 by the global oceans has been estimated to be 2.2 (+22% or ?19%) Pg C yr?1 using the (wind speed)2 dependence of the CO2 gas transfer velocity of Wanninkhof (J. Geophys. Res. 97 (1992) 7373). The errors associated with the wind-speed variation have been estimated using one standard deviation (about±2 m s?1) from the mean monthly wind speed observed over each 4°×5° pixel area of the global oceans. The new global uptake flux obtained with the Wanninkhof (wind speed)2 dependence is compared with those obtained previously using a smaller number of measurements, about 250,000 and 550,000, respectively, and are found to be consistent within±0.2 Pg C yr?1. This estimate for the global ocean uptake flux is consistent with the values of 2.0±0.6 Pg C yr?1 estimated on the basis of the observed changes in the atmospheric CO2 and oxygen concentrations during the 1990s (Nature 381 (1996) 218; Science 287 (2000) 2467). However, if the (wind speed)3 dependence of Wanninkhof and McGillis (Res. Lett. 26 (1999) 1889) is used instead, the annual ocean uptake as well as the sensitivity to wind-speed variability is increased by about 70%. A zone between 40° and 60° latitudes in both the northern and southern hemispheres is found to be a major sink for atmospheric CO2. In these areas, poleward-flowing warm waters meet and mix with the cold subpolar waters rich in nutrients. The pCO2 in the surface water is decreased by the cooling effect on warm waters and by the biological drawdown of pCO2 in subpolar waters. High wind speeds over these low pCO2 waters increase the CO2 uptake rate by the ocean waters. The pCO2 in surface waters of the global oceans varies seasonally over a wide range of about 60% above and below the current atmospheric pCO2 level of about 360 ?atm. A global map showing the seasonal amplitude of surface-water pCO2 is presented. The effect of biological utilization of CO2 is differentiated from that of seasonal temperature changes using seasonal temperature data. The seasonal amplitude of surface-water pCO2 in high-latitude waters located poleward of about 40° latitude and in the equatorial zone is dominated by the biology effect, whereas that in the temperate gyre regions is dominated by the temperature effect. These effects are about 6 months out of phase. Accordingly, along the boundaries between these two regimes, they tend to cancel each other, forming a zone of small pCO2 amplitude. In the oligotrophic waters of the northern and southern temperate gyres, the biology effect is about 35 ?atm on average. This is consistent with the biological export flux estimated by Laws et al. (Glob. Biogeochem. Cycles 14 (2000) 1231). Small areas such as the northwestern Arabian Sea and the eastern equatorial Pacific, where seasonal upwelling occurs, exhibit intense seasonal changes in pCO2 due to the biological drawdown of CO2.

International one-atmosphere equation of state of seawater

Abstract: The density measurements by Millero, Gonzalez and Ward (1976, Journal of Marine Research,34, 61–93) and Poisson, Brunet and Brun-Cottan (1980, Deep-Sea Research, 27, 1013–1028), from 0 to 40°C and 0.5 to 43 salinity, have been used to determine a new 1-atm equation of state for seawater. The equation is of the form (t°C; S; ϱ kg m−3) ρ=ρ 0 +AS+BS 3 2 +CS , where A=8.24493×10 −1 −4.0899×10 −3 t+7.6438×10 −5 t 2 −8.2467×10 −7 t 3 +5.3875×10 −9 t 4 B=−5.72466×10 −3 +1.0227×10 −4 t−1.6546×10 −6 t 2 C=4.8314×10 −4 and ϱ0 is the density of water ( Bigg , 1967, British Journal of Applied Physics, 8, 521–537). ρ 0 =999.842594+6.793952×10 −2 t−9.095290× −3 t 2 +1.001685×10 −4 t 3 −1.120083×10 −6 t 4 +6.536336×10 −9 t 5 . The standard error of the equation is 3.6 × 10−3 kg m−3. This equation will become the new 1-atm equation of state of seawater that has been suggested for use by the UNESCO (United Nations Educational, Scientific and Cultural Organization) joint panel on oceanographic tables and standards.

New determination of carbonic acid dissociation constants in seawater as a function of temperature and salinity

Abstract: The apparent dissociation constants of carbonic acid (K1∗, K2∗) were determined at atmospheric pressure by potentiometric titrations in artificial seawater. Constants (K1∗, K2∗) were extracted from the experimental titration curves both by a non-linear curve-fitting procedure, and by using the Gran functions. There is good agreement between the two mathematical calculations for both constants. Throughout the salinity range of 10 < S < 50 and the temperature range of −1°C < T < 40°C this new data set agrees closely with the previous set of Hansson (1972). His results, combined with ours and fitted as a function of temperature and salinity, satisfy the following relationships: pK1∗=812.27T+3.356−0.00171 x S x ln(T)+0.000091 x S2 pK1∗=1450.87T+4.604−0.00385 x S x ln(T)+0.000182 x S2 where the constants K1∗ are expressed in moles per kilogram of solution.

Changes in the δ13C of surface water particulate organic matter across the subtropical convergence in the SW Indian Ocean

Abstract: We have measured the carbon isotopic composition of particulate organic matter suspended in surface waters (POM) between 59°S and 30°S in the SW Indian Ocean during the austral summer. In an attempt to further document the pattern and causes of covariance between POC-δ13C and [CO2aq], we concurrently measured surface water pCO2, temperature, salinity, nitrate concentration, POM concentration, chlorophyll a and the δ13C of total dissolved inorganic carbon. While we found the previously reported general negative correlation between POC-δ13C and [CO2aq], we also observed a prominent maximum in POC-δ13C in the region immediately north of the Subtropical Convergence, coinciding with a maximum in [POM] and chlorophyll a, and with a minimum in pCO2. The increase in POC-δ13C between 59°S and the Subtropical Convergence is consistent with the trend expected if [CO2aq] were the main factor controlling the isotopic composition of POM. In contrast, data from the region north of the Subtropical Convergence clearly illustrate that POC-δ13C can also vary independently of [CO2aq] as a 5 per mil decrease in POC-δ13C was found in a region characterized by nearly constant [CO2aq]. We review several physiological factors which may account for these observations and discuss their implications for paleoceanographic reconstruction of [CO2aq] from the carbon isotopic composition of sedimentary organic matter.

Seasonal and interannual variability of CO2 in the equatorial Pacific

Abstract: As part of the JGOFS field program, extensive CO2 partial-pressure measurements were made in the atmosphere and in the surface waters of the equatorial Pacific from 1992 to 1999. For the first time, we are able to determine how processes occurring in the western portion of the equatorial Pacific impact the sea–air fluxes of CO2 in the central and eastern regions. These 8 years of data are compared with the decade of the 1980s. Over this period, surface-water pCO2 data indicate significant seasonal and interannual variations. The largest decreases in fluxes were associated with the 1991–94 and 1997–98 El Nino events. The lower sea–air CO2 fluxes during these two El Nino periods were the result of the combined effects of interconnected large-scale and locally forced physical processes: (1) development of a low-salinity surface cap as part of the formation of the warm pool in the western and central equatorial Pacific, (2) deepening of the thermocline by propagating Kelvin waves in the eastern Pacific, and (3) the weakening of the winds in the eastern half of the basin. These processes serve to reduce pCO2 values in the central and eastern equatorial Pacific towards near-equilibrium values at the height of the warm phase of ENSO. In the western equatorial Pacific there is a small but significant increase in seawater pCO2 during strong El Nino events (i.e., 1982–83 and 1997–98) and little or no change during weak El Nino events (1991–94). The net effect of these interannual variations is a lower-than-normal CO2 flux to the atmosphere from the equatorial Pacific during El Nino. The annual average fluxes indicate that during strong El Ninos the release to the atmosphere is 0.2–0.4 Pg C yr−1 compared to 0.8–1.0 Pg C yr−1 during non-El Nino years.

Climate Change 2007: The Physical Science Basis.

Abstract: Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

The oceanic sink for anthropogenic CO2.

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

Couplings between changes in the climate system and biogeochemistry

Abstract: Couplings Between Changes in the Climate System and Biogeochemistry Coordinating Lead Authors: Kenneth L. Denman (Canada), Guy Brasseur (USA, Germany) Lead Authors: Amnat Chidthaisong (Thailand), Philippe Ciais (France), Peter M. Cox (UK), Robert E. Dickinson (USA), Didier Hauglustaine (France), Christoph Heinze (Norway, Germany), Elisabeth Holland (USA), Daniel Jacob (USA, France), Ulrike Lohmann (Switzerland), Srikanthan Ramachandran (India), Pedro Leite da Silva Dias (Brazil), Steven C. Wofsy (USA), Xiaoye Zhang (China) Contributing Authors: D. Archer (USA), V. Arora (Canada), J. Austin (USA), D. Baker (USA), J.A. Berry (USA), R. Betts (UK), G. Bonan (USA), P. Bousquet (France), J. Canadell (Australia), J. Christian (Canada), D.A. Clark (USA), M. Dameris (Germany), F. Dentener (EU), D. Easterling (USA), V. Eyring (Germany), J. Feichter (Germany), P. Friedlingstein (France, Belgium), I. Fung (USA), S. Fuzzi (Italy), S. Gong (Canada), N. Gruber (USA, Switzerland), A. Guenther (USA), K. Gurney (USA), A. Henderson-Sellers (Switzerland), J. House (UK), A. Jones (UK), C. Jones (UK), B. Karcher (Germany), M. Kawamiya (Japan), K. Lassey (New Zealand), C. Le Quere (UK, France, Canada), C. Leck (Sweden), J. Lee-Taylor (USA, UK), Y. Malhi (UK), K. Masarie (USA), G. McFiggans (UK), S. Menon (USA), J.B. Miller (USA), P. Peylin (France), A. Pitman (Australia), J. Quaas (Germany), M. Raupach (Australia), P. Rayner (France), G. Rehder (Germany), U. Riebesell (Germany), C. Rodenbeck (Germany), L. Rotstayn (Australia), N. Roulet (Canada), C. Sabine (USA), M.G. Schultz (Germany), M. Schulz (France, Germany), S.E. Schwartz (USA), W. Steffen (Australia), D. Stevenson (UK), Y. Tian (USA, China), K.E. Trenberth (USA), T. Van Noije (Netherlands), O. Wild (Japan, UK), T. Zhang (USA, China), L. Zhou (USA, China) Review Editors: Kansri Boonpragob (Thailand), Martin Heimann (Germany, Switzerland), Mario Molina (USA, Mexico) This chapter should be cited as: Denman, K.L., G. Brasseur, A. Chidthaisong, P. Ciais, P.M. Cox, R.E. Dickinson, D. Hauglustaine, C. Heinze, E. Holland, D. Jacob, U. Lohmann, S Ramachandran, P.L. da Silva Dias, S.C. Wofsy and X. Zhang, 2007: Couplings Between Changes in the Climate System and Biogeochemistry. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Impact of Anthropogenic CO2 on the CaCO3 System in the Oceans

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

Carbon and Other Biogeochemical Cycles

Abstract: For base year 2010, anthropogenic activities created ~210 (190 to 230) TgN of reactive nitrogen Nr from N2. This human-caused creation of reactive nitrogen in 2010 is at least 2 times larger than the rate of natural terrestrial creation of ~58 TgN (50 to 100 TgN yr−1) (Table 6.9, Section 1a). Note that the estimate of natural terrestrial biological fixation (58 TgN yr−1) is lower than former estimates (100 TgN yr−1, Galloway et al., 2004), but the ranges overlap, 50 to 100 TgN yr−1 vs. 90 to 120 TgN yr−1, respectively). Of this created reactive nitrogen, NOx and NH3 emissions from anthropogenic sources are about fourfold greater than natural emissions (Table 6.9, Section 1b). A greater portion of the NH3 emissions is deposited to the continents rather than to the oceans, relative to the deposition of NOy, due to the longer atmospheric residence time of the latter. These deposition estimates are lower limits, as they do not include organic nitrogen species. New model and measurement information (Kanakidou et al., 2012) suggests that incomplete inclusion of emissions and atmospheric chemistry of reduced and oxidized organic nitrogen components in current models may lead to systematic underestimates of total global reactive nitrogen deposition by up to 35% (Table 6.9, Section 1c). Discharge of reactive nitrogen to the coastal oceans is ~45 TgN yr−1 (Table 6.9, Section 1d). Denitrification converts Nr back to atmospheric N2. The current estimate for the production of atmospheric N2 is 110 TgN yr−1 (Bouwman et al., 2013).