ALBERT

Description: Δ14Catm has been estimated as 420 ± 80% (IntCal09) during the Last Glacial Maximum (LGM) compared to preindustrial times (0%), but mechanisms explaining this difference are not yet resolved. Δ14Catm is a function of both cosmogenic production in the high atmosphere and of carbon cycling and partitioning in the Earth system. 10Be-based reconstructions show a contribution of the cosmogenic production term of only 200 ± 200% in the LGM. The remaining 220% have thus to be explained by changes in the carbon cycle. Recently, Bouttes et al. (2010, 2011) proposed to explain most of the difference in pCO2atm and Δ13C between glacial and interglacial times as a result of brine-induced ocean stratification in the Southern Ocean. This mechanism involves the formation of very saline water masses that contribute to high carbon storage in the deep ocean. During glacial times, the sinking of brines is enhanced and more carbon is stored in the deep ocean, lowering pCO2atm. Moreover, the sinking of brines induces increased stratification in the Southern Ocean, which keeps the deep ocean well isolated from the surface. Such an isolated ocean reservoir would be characterized by a low Δ14C signature. Evidence of such 14C-depleted deep waters during the LGM has recently been found in the Southern Ocean (Skinner et al. 2010). The degassing of this carbon with low Δ14C would then reduce Δ14Catm throughout the deglaciation. We have further developed the CLIMBER-2 model to include a cosmogenic production of 14C as well as an interactive atmospheric 14C reservoir. We investigate the role of both the sinking of brine and cosmogenic production, alongside iron fertilization mechanisms, to explain changes in Δ14Catm during the last deglaciation. In our simulations, not only is the sinking of brine mechanism consistent with past Δ14C data, but it also explains most of the differences in pCO2atm and Δ14Catm between the LGM and preindustrial times. Finally, this study represents the first time to our knowledge that a model experiment explains glacial-interglacial differences in pCO2atm, Δ13C, and Δ14C together with a coherent LGM climate.

Description: From October 2010 to November 2011, the urban atmospheric CO2 concentration in Guangzhou ranged from 550 to 460 ppm, with mean monthly concentration fluctuating between 530 and 470 ppm. A lower concentration was observed in summer and autumn, while a higher concentration occurred in spring and winter. The urban atmospheric CO2 δ13C value varied between −9.00 and −13.10%, with mean monthly value fluctuating between −9.60 and −11.80%. There was no significant relationship between the CO2 concentration and δ13C value, reflecting the influence from the fossil-fuel-derived CO2 on the urban atmospheric CO2. The urban atmospheric CO2 Δ14C value fluctuated dramatically from 29.1 ± 2.5% to −85.2 ± 3. 1%, with a mean annual value of −16.4 ± 3.0%. A similar seasonal variation of Δ14C value with the concentrations was observed: the higher Δ14C values mainly appeared in summer and autumn (July to September), with a mean value of about −5.2 ± 2.9%, while lower Δ14C values occurred in spring and winter (December to April), about −27.1 ± 3.2% average. Based on the atmospheric Δ14C values, the calculated fossil-fuel-derived CO2 concentrations range between 1 and 58 ppm, with the mean annual concentration around 24 ppm. Similarly, a lower fossil-fuel-derived CO2 concentration appeared in summer and autumn (July to September) with a mean value of ∼17 ppm, while the higher fossil-fuel-derived CO2 concentration occurred in spring and winter (December to April) with an average value of ∼29 ppm. A comparison of the CO2 concentrations before and after the Guangzhou Asian Games (in November 2010) and the Spring Festival of 2011 confirmed that human activities can greatly decrease the fossil-fuel-derived CO2 emissions to the urban atmosphere in Guangzhou.

Description: The stability of a viscous liquid film flowing under gravity down an inclined wall with periodic corrugations is investigated. A long-wave model equation valid at near-critical Reynolds numbers is used to study the film dynamics, and calculations are performed for either sinusoidal or rectangular wall corrugations assuming either a fixed flow rate in the film or a fixed volume of fluid within each wall period. Under the two different flow assumptions, steady solution branches are delineated including subharmonic branches, for which the period of the free surface is an integer multiple of the wall period, and the existence of quasi-periodic branches is demonstrated. Floquet-Bloch theory is used to determine the linear stability of steady, periodic solutions and the nature of any instability is analysed using the method of exponentially weighted spaces. Under certain conditions, and depending on the wall period, the flow may be convectively unstable for small wall amplitudes but undergo transition to absolute instability as the wall amplitude increases, a novel theoretical finding for this class of flows; in other cases, the flow may be convectively unstable for small wall amplitudes but stable for larger wall amplitudes. Solutions with the same spatial period as the wall become unstable at a critical Reynolds number, which is strongly dependent on the period size. For sufficiently small wall periods, the corrugations have a destabilizing effect by lowering the critical Reynolds number above which instability occurs. For slightly larger wall periods, small-amplitude corrugations are destabilizing but sufficiently large-amplitude corrugations are stabilizing. For even larger wall periods, the opposite behaviour is found. For sufficiently large wall periods, the corrugations are destabilizing irrespective of their amplitude. The predictions of the linear theory are corroborated by time-dependent simulations of the model equation, and the presence of absolute instability under certain conditions is confirmed. Boundary element simulations on an inverted substrate reveal that wall corrugations can have a stabilizing effect at zero Reynolds number. © 2013 Cambridge University Press.

Description: Mangrove ecosystems are highly productive and play an important role in tropical and global coastal carbon (C) budgets. However, sedimentary organic carbon (SOC) storage and turnover in mangrove forests are still poorly understood. Based on C isotopic measurements of sediment cores of 2 mangrove stands in southern China, SOC density was 431.77 Mg ha−1 at site 1 (a Aegiceras corniculatum-dominated high tidal stand) and 243.65 Mg ha−1 in site 2 (a Bruguiera gymnorrhiza + Kandelia candel-dominated middle tidal stand). SOC δ13C values at both mangrove sites ranged from -29.4% to −26.0%. SOC δ13C was enriched with depth at 20–50 cm at site 1, which possibly resulted from preferential microbial decomposition. SOC δ13C at site 2 experienced frequent tidal flushing, and presented relatively stable values with depth. A bomb-14C-based SOC turnover model indicated that turnover times of SOC at 20–50 cm at site 1 were 4.44–26.04 yr. Modern C input from abundant roots might account for the very short SOC turnover times at these subsurface layers. As a result, our study suggested that tidal processes had a great influence on SOC storage and turnover in mangrove forests.

Description: The Laboratoire des Sciences du Climat et de l'Environnement (LSCE) research program on prehistoric art conducts chronological studies of parietal representations with their associated archaeological context. This multidisciplinary approach provides chronological arguments about the creation period of parietal representations. This article presents chronological investigations carried out in several decorated caves in France (La Grande Grotte, Labastide, Lascaux, La Tête-du-Lion, Villars) and Spain (La Garma, Nerja, La Pileta, Urdiales). Several types of organic materials, collected from different areas of the caves close to the walls and in connection with parietal art, were dated to determine the periods of human presence in the cave, a presence that may have been related to artistic activities. These new radiocarbon results range from 33,000–29,000 (La Grande Grotte) to 16,000–14,000 cal BP (Urdiales).

Description: After 22 yr of the low-level liquid scintillation counting 14C laboratory at the Center for Nuclear Energy in Agriculture (CENA) at São Paulo University (USP), Piracicaba, Brazil, and several collaborative projects with Brazilian and international researchers from distinct scientific areas, the first 14C accelerator mass spectrometry (AMS) laboratory in Latin America was installed at the Physics Institute of the Universidade Federal Fluminense (UFF), Niterói, Brazil. A 250kV single stage accelerator produced by National Electrostatics Corporation began its operation in 2012. In this work, we compare measurements performed at the AMS Radiocarbon Laboratory at UFF (LAC-UFF) with those performed at CENA and the University of Georgia (UGAMS), Georgia, USA. All the results obtained from distinct inorganic and organic samples were in very good agreement.

Description: SummaryEnvironmental policy integration is an acknowledged principle of sustainable development. Spatial planning may be a useful means of integrating two policies with differing objectives. The Birds and Habitats Directives of the European Union (EU) aim at preserving biodiversity through the conservation of the Natura 2000 protected areas network, while the EU's Environmental Noise Directive aims at improving human health and wellbeing by controlling environmental noise, through the preservation of Quiet Areas (QAs). Using Greece as an example, an integrated network of Natura 2000 sites and QAs permitted the identification of potential spatial overlaps. The established Natura 2000 network incorporates more than 30% of the QAs located in the open countryside of Greece, and the combined network includes 17 out of the 19 conservation priority habitat types. Flagship species (like bear, wolf and wild goat) show a preference for sites containing QAs. It may be possible to combine these two EU policies efficiently, as protected and quiet areas appear to be mutually beneficial.

Description: SUMMARYThe environmental concern about diffuse pollution from nitrogen (N) fertilizers has led to increased research on the diagnosis of crop N status. The SPAD chlorophyll (Chl) meter is the most commonly used tool for rice (Oryza sativa L.) N status diagnosis, but measurements are conducted at a specific point and readings are affected by different leaf positions. Many measurements per plant must be taken in order to increase the accuracy of N status diagnosis, which limits its application. The present paper attempts to determine rice N status at the canopy level using Multiplex®, a new hand-held optical fluorescence sensor. The fluorescence emission of rice leaves under light excitation was utilized by Multiplex® to non-destructively assess rice leaf Chl and phenolic compound content. A field experiment was conducted in 2011 using a completely randomized split-plot design, with main-plot treatments being six N fertilizer application rates and subplot treatments being different plant densities. Leaf Chl and phenolic compounds were evaluated using the ratio of far-red fluorescence (FRF) to red fluorescence (RF) emission under red light excitation (simple fluorescence ratio, SFR_R) (R2 = 0·35, P 

Description: Recent acceleration and thinning of Thwaites Glacier, West Antarctica, motivates investigation of the controls upon, and stability of, its present ice-flow pattern. Its eastern shear margin separates Thwaites Glacier from slower-flowing ice and the southern tributaries of Pine Island Glacier. Troughs in Thwaites Glacier’s bed topography bound nearly all of its tributaries, except along this eastern shear margin, which has no clear relationship with regional bed topography along most of its length. Here we use airborne ice-penetrating radar data from the Airborne Geophysical Survey of the Amundsen Sea Embayment, Antarctica (AGASEA) to investigate the nature of the bed across this margin. Radar data reveal slightly higher and rougher bed topography on the slower-flowing side of the margin, along with lower bed reflectivity. However, the change in bed reflectivity across the margin is partially explained by a change in bed roughness. From these observations, we infer that the position of the eastern shear margin is not strongly controlled by local bed topography or other bed properties. Given the potential for future increases in ice flux farther downstream, the eastern shear margin may be vulnerable to migration. However, there is no evidence that this margin is migrating presently, despite ongoing changes farther downstream.