Publicações

The lower Miocene Pirabas Formation in the North of Brazil was deposited under influence of the proto-Amazon River and is characterized by large changes in the ecological niches from the early Miocene onwards. To evaluate these ecological changes, the elasmobranch fauna of the fully marine, carbonate-rich beds was investigated. A diverse fauna with 24 taxa of sharks and rays was identified with the dominant groups being carcharhiniforms and myliobatiforms. This faunal composition is similar to other early Miocene assemblages from the proto-Carribbean bioprovince. However, the Pirabas Formation has unique features compared to the other localities; being the only Neogene fossil fish assemblage described from the Atlantic coast of Tropical Americas. Phosphate oxygen isotope composition of elasmobranch teeth served as proxies for paleotemperatures and paleoecology. The data are compatible with a predominantly tropical marine setting with recognized inshore and offshore habitats with some probable depth preferences (e.g., Aetomylaeus groups). Paleohabitat of taxa particularly found in the Neogene of the Americas (Carcharhinus ackermannii, Aetomylaeus cubensis) are estimated to have been principally coastal and shallow waters. Larger variation among the few analyzed modern selachians reflects a larger range for the isotopic composition of recent seawater compared to the early Miocene. This probably links to an increased influence of the Amazon River in the coastal regions during the Holocene.

COMUNICAÇÃO NACIONAL DO BRASIL À CONVENÇÃO-QUADRO DAS NAÇÕES UNIDAS SOBRE MUDANÇA DO CLIMA

A compilação destes estudos setoriais para a TCN evidenciou não só a robustez técnica dos trabalhos elaborados, mas, igualmente, a relevância dos re-sultados alcançados para os gestores e tomadores de decisão no âmbito de políticas públicas. Tal constatação motivou o MCTI a organizar a publicação que ora se apre-senta, dedicando o devido espaço à exposição do relevante salto dado neste campo do conhecimento no Brasil.

An understanding of variations in morphophysiological leaf traits of plant models in dry tropical forests is essential for quantifying C fluxes from forest ecosystems in response to climate changes. The present study evaluated the influences of seasonal rainfall and different light conditions on the gas exchange, nutrients, organic compounds and morphological traits in Croton blanchetianus Baill. trees within a fragment of Caatinga forest. Stomatal conductance (gs) and net photosynthesis (PN) demonstrated variations within the diurnal cycle, with maximum values at approximately midday and minimum values at predawn. The PN and the diurnal integrated CO2 assimilation were lower during the dry season than in the rainy season. Water use efficiency was positively correlated with PN (r = 0.73) during the dry season only. However, the correlation between PN and gs was observed during the rainy season only (r = 0.60). Thus we demonstrated that C. blanchetianus has a remarkable ability to adapt to global climatic changes and could be considered a model in studies exploring water relationships in woody plants; consequently, this species may be important in future reforestation studies.

The Brazilian Scientific Mobility Program – Science without Borders (SwB) – saw the concession of over 101 thousand scholarships for Brazilian STEM students and education professionals to attend universities worldwide. As the first phase of this program ends, it is time to take a first look at its impacts, mainly on the undergraduate student body (79% of total scholarships implemented). Benefits included a 6-month language course (optional), a one year undergraduate course and optional 2 month internship in a university, government laboratory or technology company. Positive impacts have been seen on entrance into postgraduate programs (>20% of SwB students compared to <5% of the overall student body of similar fields), as well as high representation of lower income families (>50% from families with less than 6 minimum wages per month). The impact of the program will need to be evaluated over the next years, but innovation on the part of the students is already apparent. Any new SwB program needs to take into account the lessons learned from this first experience and therefore recommendations are presented.

Agricultural production risk is getting increasing attention in the science and the policy domain due to its strong connection with food security and its potential to trigger systemic risks. Particularly in semi-arid regions, weather and environmental conditions can seriously affect agricultural production. Brazil stands out exceptionally as it has one of the most populated semi-arid areas globally. Nevertheless, risk assessment of crop production for these regions is lacking, but essentially needed for policy and risk management purposes. To fill part of this gap, this paper provides first estimates of crop yield risk for the semi-arid in Brazil on the municipality level from an empirical perspective. It was found that many highly vulnerable municipalities are located in states such as Ceará, Piauí, Pernambuco, and Paraíba. These hotspot regions may be prioritized in terms of public investments in order to help them decrease current and future vulnerability related to crop production. Especially climate change impacts may worsen the situation considerably in the future and should be included already in current adaptation strategies.

One of the clear signals of the ongoing climate change is sea level rise (SLR). Normal oceanic tides superimposed on a rising sea level and coastal flooding will affect many coastal communities. An international collaboration among Brazil, the United Kingdom, and the United States was designed to evaluate local decision making processes and to open space for local urban managers to reflect on possible actions toward adaption to sea level rise given the historical constraints imposed by administrative and institutional structures. This project focused on the processes that shape adaptation of three coastal communities in three countries. It worked jointly with these communities in defining the problem, examining risks, and understanding the benefits and obstacles that may hinder implementation of adaptation options. The framework was co-designed by an interdisciplinary team that incorporated social and natural scientists from the three countries, including local government officials. The study addressed 1) evaluation of adaptive capacity through participant surveys and 2) physical and cost impact simulations using geospatial models of the built infrastructure and implementation of adaptation options under different hazard scenarios, including 50 and 100-year sea level rise projections and severe storms. Based on the surveys results, there is a clear sense of the awareness of each community of the risk of floods due to intense storms, and of the usefulness of engaging early in a process that promotes the understanding of risks, impacts, and costs. A majority of workshop participants prioritized pursuing physical and green infrastructure actions now or within coming years or decades. A positive common aspect of the three sites was the commitment shown by the stakeholders in taking part in the process and evaluating which adaptation measures could be more effective in their cities. While in the US and UK structural solutions and voluntary buyouts were prioritized for the future, Brazil prioritized structural solutions and ecosystems restoration and not voluntary buyouts. All of these are choices to increase resiliency against sea level rise that have a high benefit-cost ratio. The Adaptive Capacity Index (ACI) results illustrate barriers to adaptation action, including technical, economic and political issues that reveal inequalities in adaptive capacity among case studies.

The pattern and size of the Earths atmospheric circulation cells determine regional climates and challenge theorists. Here the authors present a theoretical framework that relates the size of meridional cells to the kinetic energy generation within them. Circulation cells are considered as heat engines (or heat pumps) driven by surface gradients of pressure and temperature. This approach allows an analytical assessment of kinetic energy generation in the meridional cells from the known values of surface pressure and temperature differences across the cell, and . Two major patterns emerge. First, the authors find that kinetic energy generation in the upper and lower atmosphere respond in contrasting ways to surface temperature: with growing , kinetic energy generation increases in the upper atmosphere but declines in the lower. A requirement that kinetic energy generation must be positive in the lower atmosphere can limit the poleward cell extension of the Hadley cells via a relationship between and . The limited extent of the Hadley cells necessitates the appearance of heat pumps (Ferrel cells) circulation cells with negative work output. These cells consume the positive work output of the Hadley cells (heat engines) and can in theory drive the global efficiency of an axisymmetric atmospheric circulation down to zero. Second, the authors show that, within a cell, kinetic energy generation is largely determined by in the upper atmosphere, and by in the lower. By absolute magnitude, the temperature contribution is about 10 times larger. However, since the heat pumps act as sinks of kinetic energy in the upper atmosphere, the net kinetic energy generation in the upper atmosphere, as well as the net impact of surface temperature, is reduced. The authors use NCAR/NCEP and MERRA data to verify the obtained theoretical relationships. These observations confirm considerable cancellation between the temperature-related sources and sinks of kinetic energy in the upper atmosphere. Both the theoretical approach and observations highlight a major contribution from surface pressure gradients, rather than temperature, in the kinetic energy budget of meridional circulation. The findings urge increased attention to surface pressure gradients as determinants of the meridional circulation patterns.

The power of atmospheric circulation is a key measure of the Earths climate system. The mismatch between predictions and observations under a warming climate calls for a reassessment of how atmospheric power W is defined, estimated and constrained. Here we review published formulations for W and show how they differ when applied to a moist atmosphere. Three factors, a non-zero source/sink in the continuity equation, the difference between velocities of gaseous air and condensate, and interaction between the gas and condensate modifying the equations of motion, affect the formulation of W. Starting from the thermodynamic definition of mechanical work, we derive an expression for W from an explicit consideration of the equations of motion and continuity. Our analyses clarify how some past formulations are incomplete or invalid. Three caveats are identified. First, W critically depends on the boundary condition for gaseous air velocity at the Earths surface. Second, confusion between gaseous air velocity and mean velocity of air and condensate in the expression for W results in gross errors despite the observed magnitudes of these velocities are very close. Third, W expressed in terms of measurable atmospheric parameters, air pressure and velocity, is scale-specific; this must be taken into account when adding contributions to W from different processes. We further present a formulation of the atmospheric power budget, which distinguishes three components of W: the kinetic power associated with horizontal pressure gradients (WK), the gravitational power of precipitation (WP ) and the condensate loading (Wc). This formulation is valid with an accuracy of the squared ratio of the vertical to horizontal air velocities. Unlike previous approaches, it allows evaluation of WP + Wc without knowledge of atmospheric moisture or precipitation. This formulation also highlights that WP and Wc are the least certain terms in the power budget as they depend on vertical velocity; WK depending on horizontal velocity is more robust. We use MERRA and NCAR/NCEP re-analyses to evaluate the atmospheric power budget at different scales. Estimates of WK are found to be consistent across the re-analyses, while estimates for W and WP drastically differ. We then estimate independent precipitation-based values of WP and discuss how such estimates could reduce uncertainties. Our analyses indicate that WK increases with temporal resolution approaching our theoretical estimate for condensation-induced circulation when all convective motion is resolved. Implications of these findings for constraining global atmospheric power are discussed.

How phase transitions affect the motion of moist atmospheric air remains controversial. In the early 2000s two distinct differential equations of motion were proposed. Besides their contrasting formulations for the acceleration of condensate, the equations differ concerning the presence/absence of a term equal to the rate of phase transitions multiplied by the difference in velocity between condensate and air. This term was interpreted in the literature as the reactive motion associated with condensation. The reasoning behind this reactive motion was that when water vapor condenses and droplets begin to fall the remaining gas must move upward to conserve momentum. Here we show that the two contrasting formulations imply distinct assumptions about how gaseous air and condensate particles interact. We show that these assumptions cannot be simultaneously applicable to condensation and evaporation. Reactive motion leading to an upward acceleration of air during condensation does not exist. The reactive motion term can be justified for evaporation only; it describes the downward acceleration of air. We emphasize the difference between the equations of motion (i.e., equations constraining velocity) and those constraining momentum (i.e., equations of motion and continuity combined). We show that owing to the imprecise nature of the continuity equations, consideration of total momentum can be misleading and that this led to the reactive motion controversy. Finally, we provide a revised and generally applicable equation for the motion of moist air.