Interannual variability of the carbon dioxide system in the southern Indian Ocean (20 degrees S-60 degrees S): The impact of a warm anomaly in austral summer 1998

The interannual variations of the carbon dioxide system and air-sea CO(2) fluxes are analyzed in the southwestern Indian Ocean from both in situ (Ocean Indien Service d'Observations cruises in 1998 and 2000) and simulated oceanic CO(2) fugacity f(CO2) dissolved inorganic carbon, total alkalinity, and nutrients. During austral summer of 1998, the ocean was warmer from 20degreesS to 60degreesS. In the Subtropical Zone (20degreesS-37degreesS), the warming, associated with the subtropical dipole pattern, creates an oceanic CO(2) source around 2 mmol m(-2) d(-1) in January 1998 where all previous observations, included in 2000, indicated that this region was a small sink in summer. In the Sub-Antarctic and Polar Front Zones (37degreesS-50degreesS), the f(CO2) interannual signal is not clearly detected because of the complex coupling between the horizontal and vertical dynamics and the biological activity that creates very high mesoscale f(CO2) variability in each summer. For the austral region, south of the Polar Front, we observe large variability in the CO(2) sources and sinks between summer 1998 and 2000. In the Seasonal Ice Zone (south of 58degreesS) the interannual variation of the CO(2) flux was mainly controlled by a warmer ocean, from 1.1degreesC, in summer 1998 (CO(2) source of 3.2 mmol m(-2) d(-1)) and an enhanced primary production occurring during summer 2000 (CO(2) sink of -3.8 mmol m(-2) d(-1)). In the Permanent Open Ocean Zone (POOZ, latitude 50degreesS-57degreesS), despite the half-degree warmer sea surface in 1998, we observe lower f(CO2) (-15 muatm (1 atm = 10(5) x 1.01325 N m(-2)) on average) during this period, and consequently, we estimate a double of the oceanic CO(2) sink in this region in 1998 than 2000, from -3.2 mmol m(-2) d(-1) in 1998 to -1.3 mmol m(-2) d(-1) in 2000. The strong oceanic CO(2) sink in 1998 is associated with a dramatic decrease of nutrients (silicates less than 2 mumol kg(-1)). The enhanced biological activity in summer 1998, probably diatoms bloom, is also apparent in Sea-viewing Wide Field-of-view Sensor (SeaWiFS) chlorophyll a estimates. Using a one-dimensional biogeochemical model applied in the POOZ and SeaWIFS time series, we predict a stronger oceanic sink during summer season than the winter, which is contrary to previous studies. The model suggests that biological activity controls most of the sink anomaly in summer 1998 (for about 70%) and dominates the warming effect

Summer and winter air-sea CO₂ fluxes in the Southern Ocean

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Fire Emissions and Carbon Uptake in Severely Burned Lenga Beech (Nothofagus pumilio) Forests of Patagonia, Argentina

Los incendios forestales son reconocidos como fuentes de emisión de CO2 y otros gases de efecto invernadero (GHG) que, alterando la dinámica del intercambio entre el carbono (C) terrestre y el atmosférico, influencian el clima global. En la región central de la Patagonia Andina Argentina, incendios de características severas han afectado los bosques de lenga (Nothofagus pumilio Poepp. & Endl. Krasser), incrementando de esa manera las emisiones de CO2 a la atmósfera y alterando asimismo sus patrones sucesionales. En este estudio, determinamos las emisiones y el secuestro de C en tres rodales, quemados en 1976 (Lago Guacho), 1983 (La Torta), y 2008 (la Colisión). La estructura forestal, y los compartimientos de biomasa aérea y broza fueron cuantificados en cada rodal quemado y en sus adyacentes sin quemar. El stock de C y de otros GHG (CO2 , CO, CH4 , NO2 , NOx y Ce) emitidos por cada incendio, el CO2 capturado y el C anual incorporado a la biomasa fueron determinados en base a las guías propuestas por el Panel Internacional para el Cambio Climático. El carbono total (biomasa aérea más radical) antes de los incendios fue de 301,8 Mg C ha-1 para La Colisión, 258,13 Mg C ha-1 para La Torta, y 270,7 Mg C ha-1 para Lago Guacho, mientras que las pérdidas de C debido a los incendios fueron de 104,6 Mg C ha-1, 90,7 Mg C ha-1, and 94,7 Mg C ha-1 para cada uno de los sitios, respectivamente. Diferencias en la estructura forestal y en la biomasa de cada sitio previo a los incendios explican los valores de emisión de CO2 y otros GHG observados después de éstos. Al presente, el balance de C es negativo en los tres sitios. Sin ninguna acción de restauración activa y usando las tasas actuales de crecimiento para cada sitio, el tiempo estimado de recuperación del C perdido es de 105,5 años para La Colisión, 94,2 años para La Torta, y 150,2 años para Lago Guacho. Mediante el uso de tasas de captura de C variables (que decrecen a medida que la sucesión avanza), el tiempo de recuperación sería de 182 años para La Colisión, 154 años para La Torta, y 162 para Lago Guacho. El ambiente post-incendio y las condiciones de cada sitio parecen tener una mayor influencia en la recuperación de la vegetación que los efectos primarios del fuego. Tareas de restauración activas aparecen como necesarias para incrementar la tasa de recuperación del C post-fuego y ayudar a re-establecer el paisaje original en bosques de lenga.Forest wildfires are recognized as sources of CO2 and other greenhouse gases (GHG) that, altering the dynamics between terrestrial and atmospheric carbon (C) exchange, influence global climate. In central Andean Patagonia, Argentina, severe wildfires affect temperate lenga beech (Nothofagus pumilio Poepp. & Endl. Krasser) forests, thereby increasing atmospheric CO2 emissions and changing natural succession paths. In this study, we determined fire emissions and C uptake in three lenga beech forests stands burned in 1976 (Lago Guacho site), 1983 (La Torta site), and 2008 (La Colisión site). Forest structure and aboveground biomass and litter compartments in burned and adjacent unburned stands were quantified for each fire. Carbon stocks and GHG (CO2 , CO, CH4 , NO2 , NOx and Ce) released by the fires, CO2 removals, and mean annual C uptake were determined by following the International Panel of Climate Change guidelines. Total (aboveground plus root) C stock before fires was 301.8 Mg C ha-1 for La Colisión, 258.13 Mg C ha-1 for La Torta, and 270.7 Mg C ha-1 for Lago Guacho, while C losses due to the fires were 104.6 Mg C ha-1, 90.7 Mg C ha-1, and 94.7 Mg C ha-1 for the three sites, respectively. Differences in pre-fire forest structures and biomass explained the values observed in CO2 and other GHG emissions after the fires. Currently, the C balance is negative for the three sites. Without any active restoration and using actual growth rates for each site, the estimated C recovery time is 105.5 yr for La Colisión, 94.2 yr for La Torta, and 150.2 yr for Lago Guacho. By using variable rates of C uptake (which decrease as early succession proceeds), this recovery time will take 182 yr for La Colisión, 154 for La Torta, and 162 yr for Lago Guacho. Post-fire environmental and site conditions appeared to have a greater influence in forest recovery than primary fire effects. Active restoration activities may be necessary to increase C recovery rates and help to re-establish former lenga beech forest landscapes.Fil: Bertolin, María Lila. Centro de Investigación y Extensión Forestal Andino Patagónico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Urretavizcaya, María Florencia. Centro de Investigación y Extensión Forestal Andino Patagónico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Defossé, Guillermo Emilio. Centro de Investigación y Extensión Forestal Andino Patagónico; Argentina. Universidad Nacional de la Patagonia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin