Part of the global DOC versus AOU (dissolved organic carbon/apparent oxygen utilization) data compilation, Pacific Ocean

Total organic carbon (TOC) was analyzed on four transects along 140°W in 1992 using a high temperature combustion/discrete injection (HTC/DI) analyzer. For two of the transects, the analyses were conducted on-board ship. Mixed-layer concentrations of organic carbon varied from about 80 µM C at either end of the transect (12°N and 12°S) to about 60 µM C at the equator. Total organic carbon concentrations decreased rapidly below the mixed-layer to about 38-40 µM C at 1000 m across the transect. Little variation was observed below this depth; deep water concentrations below 2000 m were virtually monotonic at about 36 µM C. Repeat measurements made on subsequent cruises consistently found the same concentrations at 1000 m or deeper, but substantial variations were observed in the mixed-layer and the upper water column above 400 m depth. Linear mixing models of total organic carbon versus sigmaT exhibited zones of organic carbon formation and consumption. TOC was found to be inversely correlated with apparent oxygen utilization (AOU) in the region between the mixed-layer and the oxygen minimum. In the mixed-layer, TOC concentrations varied seasonally. Part of the variations in TOC at the equator was driven by changes in the upwelling rate in response to variations in physical forcing related to an El Niño and to the passage of tropical instability waves. TOC export fluxes, calculated from simple box models, averaged 8±4 mmol C/m**2/day at the equator and also varied seasonally. These export fluxes account for 50-75% of the total carbon deficit and are consistent with other estimates and model predictions.

Part of the global DOC versus AOU (dissolved organic carbon/apparent oxygen utilization) data compilation, WOCE14

Total organic carbon (TOC) samples were collected at 6 stations spaced ~800 km apart in the eastern South Atlantic, from the Equator to 45°S along 9°W. Analyses were performed by high temperature catalytic oxidation (HTCO) in the base laboratory. Despite the complex advection and mixing patterns of North Atlantic and Antarctic waters with extremely different degrees of ventilation, TOC levels below 500 m are quasi-constant at 55±3 µmol C/l, pointing to the refractory nature of deep-water TOC. On the other hand, a TOC excess from 25 to 38 g C/m**2 is observed in the upper 100 m of the permanently stratified nutrient-depleted Equatorial, Subequatorial and Subtropical upper ocean, where vertical turbulent diffusion is largely prevented. Conversely, TOC levels in the nutrient-rich upper layer of the Subantarctic Front only exceeds 9 g C/m**2 the deep-water baseline. As much as 70% of the TOC variability in the upper 500 m is due to simple mixing of reactive TOC formed in the surface layer and refractory TOC in deep ocean waters, with a minor contribution (13%) to oxygen consumption in the prominent subsurface AOU maximum at 200-400 m depth.

Carlos Mayo y la historiografía argentina

La labor de Carlos Mayo se distingue por su originalidad y excelencia académica. Nuestro objetivo ha sido reseñar brevemente sus valiosas contribuciones a la historiografía argentina, particularmente aquella referida a la historia agraria del Río de la Plata

Carlos Altamirano, Intelectuales. Notas de investigación

Fil: Ferrero, Adrián Marcelo. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Porque lo extrañaremos tanto : Carlos Alberto Mayo (1947-2009)

Fil: Troisi Meleán, Jorge Cristian. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación. Instituto de Investigaciones en Humanidades y Ciencias Sociales (UNLP-CONICET); Argentina.

Un relato sobre los 'miserables' : Para una tumba sin nombre de Juan Carlos Onetti

En el interior del proyecto fundacional de Onetti es posible leer tanto sus elecciones como sus exclusiones, su apuesta a la invención ficcional y su rechazo de las estéticas que califica de "nativistas" y "criollistas" así como su crítica al "compromiso literario". Tracé un itinerario de las huellas de estas exclusiones en sus textos, trayecto que se inicia en El pozo (1939) y en sus escritos contemporáneos de Marcha para articularse en Para una tumba sin nombre (1959). Propongo leer esta última nouvelle a partir de la siguiente pregunta: ¿cómo es posible armar un relato sobre "los miserables" en contra del relato realista y fuera de los mandatos del compromiso político?

Part of the global DOC versus AOU (dissolved organic carbon/apparent oxygen utilization) data compilation, BATS

The contributions of total organic carbon and nitrogen to elemental cycling in the surface layer of the Sargasso Sea are evaluated using a 5-yr time-series data set (1994-1998). Surface-layer total organic carbon (TOC) and total organic nitrogen (TON) concentrations ranged from 60 to 70 µM C and 4 to 5.5 µM N seasonally, resulting in a mean C : N molar ratio of 14.4±2.2. The highest surface concentrations varied little during individual summer periods, indicating that net TOC production ceased during the highly oligotrophic summer season. Winter overturn and mixing of the water column were both the cause of concentration reductions and the trigger for net TOC production each year following nutrient entrainment and subsequent new production. The net production of TOC varied with the maximum in the winter mixed-layer depth (MLD), with greater mixing supporting the greatest net production of TOC. In winter 1995, the TOC stock increased by 1.4 mol C/m**2 in response to maximum mixing depths of 260 m. In subsequent years experiencing shallower maxima in MLD (<220 m), TOC stocks increased <0.7 mol C/m**2. Overturn of the water column served to export TOC to depth (>100 m), with the amount exported dependent on the depth of mixing (total export ranged from 0.4 to 1.4 mol C/m**2/yr). The exported TOC was comprised both of material resident in the surface layer during late summer (resident TOC) and material newly produced during the spring bloom period (fresh TOC). Export of resident TOC ranged from 0.5 to 0.8 mol C/m**2/yr, covarying with the maximum winter MLD. Export of fresh TOC varied from nil to 0.8 mol C/m**2/yr. Fresh TOC was exported only after a threshold maximum winter MLD of ~200 m was reached. In years with shallower mixing, fresh TOC export and net TOC production in the surface layer were greatly reduced. The decay rates of the exported TOC also covaried with maximum MLD. The year with deepest mixing resulted in the highest export and the highest decay rate (0.003 1/d) while shallow and low export resulted in low decay rates (0.0002 1/d), likely a consequence of the quality of material exported. The exported TOC supported oxygen utilization at dC : dO2 molar ratios ranging from 0.17 when TOC export was low to 0.47 when it was high. We estimate that exported TOC drove 15-41% of the annual oxygen utilization rates in the 100-400 m depth range. Finally, there was a lack of variability in the surface-layer TON signal during summer. The lack of a summer signal for net TON production suggests a small role for N2 fixation at the site. We hypothesize that if N2 fixation is responsible for elevated N : P ratios in the main thermocline of the Sargasso Sea, then the process must take place south of Bermuda and the signal transported north with the Gulf Stream system.