The variability of Antarctic sea ice (ASI) has great potential to affect atmospheric circulation, with impacts that can extend from the surface to the middle and high levels of troposphere. The ...present study has evaluated the response of South Atlantic tropospheric circulation to increased coverage in area and volume of ASI. Monthly data of air temperature, zonal and meridional wind and mean sea level pressure were obtained from two ensemble simulations performed with the GDFL/CM2.1 model, covering the period from July 2020 to June 2030. In general, the response of South Atlantic tropospheric circulation to increased ASI showed that the climatic signal extended up from the surface to the high levels, propagating as a South Pole-Tropics teleconnection. The results show a general cooling of the southern troposphere, which for instance lead to the strengthening and northward shift of the polar jet and the southward shift of the subtropical jet and to an inversion from the positive to negative phase of the Southern Annular Mode. This study has great relevance for understanding the global climate changes in short term, by assessing the sensitivity of South Atlantic tropospheric circulation to extreme variations in ASI.
The formation of dense water masses at polar regions has been largely influenced by climate changes arising from global warming. In this context, based on ensemble simulations with a coupled model we ...evaluate the meridional shift of a climate signal (i.e., a cold and fresh water input pulse generated from melting of positive Antarctic sea ice (ASI) extremes) towards the Tropical Atlantic Ocean (TAO). This oceanic signal propagated from Southern Ocean towards the equator through the upper layers due to an increase in its buoyance. Its northward shift has given by the Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) flows, that inject cold and fresh mode/intermediate waters from into subtropical basin. The signal has reached low latitudes through the equatorial upwelling and spreads out southwards, through the upper branch of southern subtropical gyre. We concluded that 10 years of coupled simulations was enough time to propagate the climate signal generated by ASI positive extremes melting, which reached TOA around 2 year later. The oceanic connection between Southern Ocean and TAO is indeed established within the timescale analyzed in the study (10 years). Nonetheless, the period needed to completely dissipate the disturbance generated from ASI seems to be longer.
We present an interdisciplinary review of the observed and projected variations in atmospheric and oceanic circulation within the southwestern South Atlantic focused on basin-scale processes driven ...by climate change, and their potential impact on the regional fisheries. The observed patterns of atmospheric circulation anomalies are consistent with anthropogenic climate change. There is strong scientific evidence suggesting that the Brazil Current is intensifying and shifting southwards during the past decades in response to changes in near-surface wind patterns, leading to intense ocean warming along the path of the Brazil Current, the South Brazil Bight, and in the Río de la Plata. These changes are presumably responsible for the poleward shift of commercially important pelagic species in the region and the long-term shift from cold-water to warm-water species in industrial fisheries of Uruguay. Scientific and traditional knowledge shows that climate change is also affecting small-scale fisheries. Long-term records suggest that mass mortalities decimated harvested clam populations along coastal ecosystems of the region, leading to prolonged shellfishery closures. More frequent and intense harmful algal blooms together with unfavorable environmental conditions driven by climate change stressors affect coastal shellfisheries, impact economic revenues, and damage the livelihood of local communities. We identify future modelling needs to reduce uncertainty in the expected effects of climate change on marine fisheries. However, the paucity of fisheries data prevents a more effective assessment of the impact of climate change on fisheries and hampers the ability of governments and communities to adapt to these changes.
The influence of the cross‐shelf oceanographic front occurring between the Brazil Current (BC) and the Brazilian Coastal Current (BCC) on the local Marine Atmospheric Boundary Layer (MABL) is ...investigated here. This front is typical of wintertime in the Southern Brazilian Continental Shelf (SBCS) and this is the first time that its effects are investigated over the above MABL. Here we analyze variability, vertical structure, and stability of MABL as well as heat fluxes at air‐sea interface, across five oceanographic transects in the SBCS made during a winter 2012 cruise. Local thermal gradients associated with mixing between distinct water masses, play an essential role on MABL modulation and stability. Although weaker when compared with other frontal regions, the cross‐shelf thermal gradients reproduce exactly what is expected for open ocean regions: Stronger (weaker) winds, lower (higher) sea level pressure, and a more unstable (stable) MABL are found over the warm (cold) side of the oceanographic front between the BC (warm) and coastal (cold) waters. Our findings strongly support the coexistence of both known MABL modulation mechanisms: the static and hydrostatic MABL stability. This is the first time that these modulation mechanisms are documented for this region. Turbulent fluxes were found to be markedly dependent on the cross‐shelf SST gradients resulting in differences of up to 100 W.m−2 especially in the southernmost region where the gradients were more intense.
Key Points
The strong cross‐shelf thermal gradients of the southern Brazilian Continental shelf are a key seasonal feature in the area
The gradients and the presence of the La Plata Plume waters are known to affect the biology of the area
The effects of these gradients on the local marine atmospheric boundary layer and the air‐sea fluxes of heat are first investigated here using in situ observations.
This paper presents a description of marine atmospheric boundary layer (MABL) and oceanic boundary layer (OBL) interactions at the Brazil‐Malvinas Confluence. Although this region is known as one of ...the most energetic zones of the World Ocean, very few studies have addressed the mechanisms of OA interaction there. Based upon novel, direct in situ simultaneous OA observations, our results show that the OBL‐MABL exchanges are closely correlated with the sea surface temperature (SST) field. The heat fluxes range from 110 W.m−2 over warm waters down to 18 W.m−2 over cold waters. Higher heat fluxes and air‐sea temperature differences are associated with stronger near‐surface winds. This suggests that the MABL is modulated at the synoptic temporal and spatial scale by the strong surface thermal gradients between the (warm) Brazil and the (cold) Malvinas (Falklands) currents.
Turbulent air–sea heat fluxes were computed from in situ high‐frequency micrometeorological data during two research cruises performed in the southwestern Atlantic Ocean (SWAO) occurring in June 2012 ...and October 2014. Two different and dynamical areas were covered by the cruises: the Brazil‐Malvinas Confluence (BMC) and the Southern Brazilian Continental Shelf (SBCS). The eddy covariance (EC) method was used to estimate the air–sea sensible‐ and latent‐heat fluxes. This article compares these novel high‐frequency estimates of heat fluxes with bulk parametrizations made at the same location and time from independent measurements taken on board the ships. When comparing the EC and bulk‐estimated time series of sensible‐heat fluxes, we found a good agreement both in their magnitude and variability, with small bias (generally <20 W·m−2) between the datasets from the two study areas in the SWAO. However, the EC and bulk latent‐heat flux comparisons show large biases ranging from 75 W·m−2 to 100 W·m−2 in the SBCS and BMC, respectively. These biases were always associated with short‐term, high‐frequency environmental perturbations occurring either in the atmosphere or in the ocean with the majority related to strong wind burst events and large air–sea temperature gradients. The short period changes in atmospheric conditions were mostly related to the passage of transient synoptic systems over the two study areas. The large air–sea temperature gradients were mostly linked to the surface characteristics of the BMC and SBCS regions, where sharp oceanographic fronts are located. Our results are able to contribute to improving weather and climate simulations of the mid‐ to high latitudes of South America, a region largely influenced by the sea‐surface temperature patterns of the SWAO in combination with the frequent propagation of transient atmospheric systems.
Novel data from two research cruises performed in the southwestern Atlantic Ocean were used to describe the ocean–atmosphere latent‐ and sensible‐heat fluxes. We found that these heat fluxes were modulated by high‐frequency environmental changes in the atmosphere or in the ocean such as episodes of strong wind bursts, transient systems passage, or large differences between the SST and the air temperature at sea level.
Monolithic tin oxide aerogels synthesized using the epoxide technique were characterized with X-ray diffraction, diffusive reflectance spectroscopy, infrared spectroscopy, particle induced X-ray ...emission and photoluminescence. Our results indicate that the resulting aerogel is an electrical semi-insulator. This happens due to an incomplete chemical reaction that leaves chloride and hydroxide ions unreacted. These ions form complexes with oxygen vacancy sites producing electron trapping. Furthermore, ions of Cu, Zn and Fe were identified as naturally occurring impurities in the gel matrix, substituting Sn+4 ions.
•High surface area tin oxide aerogel was grown using the epoxide technique.•We study the electronic structure of the material using spectroscopy and photoluminescence.•The absence of electrical conductivity is a consequence of high electron trapping.•Ions of Cu, Fe and Zn were identified by PIXE as naturally occurring impurities.
Abstract
The Observing Air–Sea Interactions Strategy (OASIS) is a new United Nations Decade of Ocean Science for Sustainable Development programme working to develop a practical, integrated approach ...for observing air–sea interactions globally for improved Earth system (including ecosystem) forecasts, CO2 uptake assessments called for by the Paris Agreement, and invaluable surface ocean information for decision makers. Our “Theory of Change” relies upon leveraged multi-disciplinary activities, partnerships, and capacity strengthening. Recommendations from >40 OceanObs’19 community papers and a series of workshops have been consolidated into three interlinked Grand Ideas for creating #1: a globally distributed network of mobile air–sea observing platforms built around an expanded array of long-term time-series stations; #2: a satellite network, with high spatial and temporal resolution, optimized for measuring air–sea fluxes; and #3: improved representation of air–sea coupling in a hierarchy of Earth system models. OASIS activities are organized across five Theme Teams: (1) Observing Network Design & Model Improvement; (2) Partnership & Capacity Strengthening; (3) UN Decade OASIS Actions; (4) Best Practices & Interoperability Experiments; and (5) Findable–Accessible–Interoperable–Reusable (FAIR) models, data, and OASIS products. Stakeholders, including researchers, are actively recruited to participate in Theme Teams to help promote a predicted, safe, clean, healthy, resilient, and productive ocean.
In principle, the depth distribution of the different chemical elements near the surface of solids can be determined quantitatively and absolutely with subnanometric depth resolution using medium ...energy ion scattering (MEIS), which is a refined version of Rutherford backscattering spectrometry (RBS). The energy resolution of current MEIS analyzers reveals spectral features that cannot be resolved using conventional RBS detectors. Thus, the usual data analysis framework based on a standard Gaussian approximation for the ion energy distribution in the target is applicable to regular RBS, but not generally to MEIS, in particular if one aims at subnanometric depth resolution. The observed asymmetry in the ion energy loss distributions is a direct consequence of the asymmetric character of inelastic energy transfers during individual atomic collisions and of the stochastic character of the resulting energy losses. We propose a model that accounts for the proper statistics of the small energy loss events and for an approximate electronic energy loss distribution during the backscattering event. The validity of this model is discussed and applied to the determination of HfO
2 and TiO
2 film thicknesses as well as to detect Al
2O
3 and HfO
2 intermixing. This final application case also illustrates the potentialities as well as some inherent limitations of MEIS. The model developed here has been made available to the public in the form of a software for MEIS data analysis.
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