An additional deep-water mass in Drake Passage as revealed by 3He data

We present 3He data froma repeat section across Drake Passage, fromthree sections off the South American continent in the Pacific, at 28?S, 35?S, and 43?S, and fromthree sections in the Atlantic, eastward of the Malvinas, close to 35?W, and near the Greenwich Meridian. In Drake Passage, a distinct high-3He signal is observed that is centered just above the boundary of the Lower and the Upper Circumpolar Deep Water (LCDW, UCDW), and is concentrated towards the northern continental slope. 3He concentrations in the Antarctic Circumpolar Current (ACC) upstream of Drake Passage (World Ocean Circulation Experiment section P19 at 88?W) are markedly lower than those found in Drake Passage, and a regional source of primordial helium in the path of the ACC that might cause the high-3He feature can be ruled out. We explain the feature by addition of high-3He waters present at the 43?S Pacific section. This supports a previous, similar interpretation of a low-salinity anomaly in Drake Passage (Naveira Garabato et al., Deep- Sea Research I 49 (2002) 681), that is strongly related to the high-3He feature. Employing multiparameter water mass analysis (including 3He as a parameter), we find that deep waters as met at the 43?S Pacific section, flowing south along the South American continental slope, contribute substantially to the ACC waters in Drake Passage (fractions exceed 50% locally). Lesser, but laterally more extended contributions are found east of the Malvinas, and still smaller ones are present at 35?W and at the Greenwich Meridian. Using velocity measurements from one of the two Drake Passage sections, we estimate the volume transport of these waters to be 7.071.2 Sv, but the average transport may be somewhat lower as the other realization had a less pronounced signal. The enhanced 3He signature in Drake Passage is essentially confined north of the Polar Front. Further downstreamthe signature crosses this front, to the extent that at 35?W the contributions south and north of it are of similar magnitude. At the same time, the 3He levels north of the front are reduced due to a substantial admixture of low-3He North Atlantic Deep Water, such that 3He becomes highest south of the front. The flow of Southeast Pacific deep slope waters entering the ACC constitutes the predominant exit pathway of the primordial helium released in the deep Pacific, and represents a considerable fraction of the deep water return flow fromthe Pacific into the ACC. Therefore and also because the density range of the added deep slope waters is intermediate between those of UCDW and LCDW, they must be considered a distinct water mass. r 2003 Elsevier Ltd. All rights reserved

Population potential in Metropolitan areas

Thesis (M.C.P.) Massachusetts Institute of Technology. Dept. of City and Regional Planning, 1949.Bibliography: leaf 20.by Richard Wellborn Roether.M.C.P

Extensive reuse of soda-lime waste glass in fly ash-based geopolymers

The possibility of extensive incorporation of soda-lime waste glass in the synthesis of fly ash-based geopolymers was investigated. Using waste glass as silica supplier avoids the use of water glass solution as chemical activator. The influence of the addition of waste glass on the microstructure and strength of fly ash-based geopolymers was studied through microstructural and mechanical characterization. Leaching analyses were also carried out. The samples were developed changing the SiO2/Al2O3 molar ratio and the molarity of the sodium hydroxide solution used as alkaline activator. The results suggest that increasing the amount of waste glass as well as increasing the molarity of the solution lead to the formation of zeolite crystalline phases and an improvement of the mechanical strength. Leaching results confirmed that the new geopolymers have the capability to immobilize heavy metal ions

Changes in ventilation of the Mediterranean Sea during the past 25 year

Significant changes in the overturning circulation of the Mediterranean Sea has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transition (WMT) during the mid-2000s. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of low ventilation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation

Interbasin deep water exchange in the western Mediterranean

Owing to its nearly enclosed nature, the Tyrrhenian Sea at first sight is expected to have a small impact on the distribution and characteristics of water masses in the other basins of the western Mediterranean, The first evidence that the Tyrrhenian Sea might, in fact, play an important role in the deep and intermediate water circulation of the entire western Mediterranean was put forward by Hopkins [1988]. There, an outflow of water from the Tyrrhenian Sea into the Algero Provencal Basin was postulated in the depth range 700-1000 m, to compensate for an observed inflow of deeper water into the Tyrrhenian Sea. However, this outflow, the Tyrrhenian Deep Water (TDW), was undetectable since it would have hydrographic characteristics that could also be produced within the Algero-Provencal Basin. A new data set of hydrographic, tracer, lowered Acoustic Doppler Current Profiler (LADCP), and deep float observations presented here allows us now to identify and track the TDW in the Algero-Provencal Basin and to demonstrate the presence and huge extent of this water mass throughout the western Mediterranean. It extends from 600 m to 1600-1900 m depth and thus occupies much of the deep water regime. The outflow from the Tyrrhenian is estimated to be of the order of 0.4 Sv (Sv=10(6) m(3) s(-1)), based on the tracer balances. This transport has the same order of magnitude as the deep water formation rate in the Gulf of Lions. The Tyrrhenian Sea effectively removes convectively generated deep water (Western Mediterranean Deep Water (WMDW)) from the Algero-Provencal Basin, mixes it with Levantine Intermediate water (LIW) above, and reinjects the product into the Algero-Provencal Basin at a level between the WMDW and LIW, thus smoothing the temperature and salinity gradients between these water masses. The tracer characteristics of the TDW and the lowered ADCP and deep float observations document the expected but weak cyclonic circulation and larger flows in a vigorous eddy regime in the basin interio

Longterm increases in western Mediteranean salinities and temperatures: a mixture of anthropogenic and climate sources

The deep water of the western Mediterranean Sea is known to have become warmer and saltier since about the 1950s. The causes of these changes have, however, not yet been sactisfactorily determined. Previous studies speculated on decreasing precipitation, greenhouse warming and/or anthropogenic reduction of the freshwater flux into the eastern Mediterranean. Here we report on results from a new oceanographic database of the western Mediterranean Sea together with determinations of longterm changes of the fresh water budget. We analyzed temperature and salinity data of the past 40 years to detect deviations from the longterm average. Certain areas and depth ranges are showing increases in temperature or salinity some of which have been found earlier and some which are new. From the regional and vertical distribution we conclude that the observed increases of temperature and salinity in the western Mediterranean Sea are caused both by changes in atmospheric conditions as described by the NAO‐index and by the regulation of Spanish rivers

Surface modifcation of SPIONs in PHBV microspheres for biomedical applications

Surface modification of superparamagnetic iron oxide nanoparticles (SPIONs) has been introduced with lauric acid and oleic acid via co-precipitation and thermal decomposition methods, respectively. This modification is required to increase the stability of SPIONs when incorporated in hydrophobic, biodegradable and biocompatible polymers such as poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). In this work, the solid-in-oil-in-water (S/O/W) emulsion-solvent extraction/evaporation method was utilized to fabricate magnetic polymer microspheres incorporating SPIONs in PHBV. The prepared magnetic PHBV microspheres exhibited particle sizes <1 µm. The presence of functional groups of lauric acid, oleic acid and iron oxide in the PHBV microspheres was confirmed by Fourier Transform Infrared spectroscopy (FTIR). X-ray diffraction (XRD) analysis was performed to further confirm the success of the combination of modified SPIONs and PHBV. Thermogravimetric analysis (TGA) indicated that PHBV microspheres were incorporated with SPIONsLauric as compared with SPIONsOleic. This was also proven via magnetic susceptibility measurement as a higher value of this magnetic property was detected for PHBV/SPIONsLauric microspheres. It was revealed that the magnetic PHBV microspheres were non-toxic when assessed with mouse embryotic fibroblast cells (MEF) at different concentrations of microspheres. These results confirmed that the fabricated magnetic PHBV microspheres are potential candidates for use in biomedical applications

Circulation and oxygen cycling in the Mediterranean Sea: Sensitivity to future climate change

Climate change is expected to increase temperatures and decrease precipitation in the Mediterranean Sea (MS) basin, causing substantial changes in the thermohaline circulation (THC) of both the Western Mediterranean Sea (WMS) and Eastern Mediterranean Sea (EMS). The exact nature of future circulation changes remains highly uncertain, however, with forecasts varying from a weakening to a strengthening of the THC. Here we assess the sensitivity of dissolved oxygen (O2) distributions in the WMS and EMS to THC changes using a mass balance model, which represents the exchanges of O2 between surface, intermediate, and deep water reservoirs, and through the Straits of Sicily and Gibraltar. Perturbations spanning the ranges in O2 solubility, aerobic respiration kinetics, and THC changes projected for the year 2100 are imposed to the O2 model. In all scenarios tested, the entire MS remains fully oxygenated after 100 years; depending on the THC regime, average deep water O2 concentrations fall in the ranges 151–205 and 160–219 µM in the WMS and EMS, respectively. On longer timescales (>1000 years), the scenario with the largest (>74%) decline in deep water formation rate leads to deep water hypoxia in the EMS but, even then, the WMS deep water remains oxygenated. In addition, a weakening of THC may result in a negative feedback on O2 consumption as supply of labile dissolved organic carbon to deep water decreases. Thus, it appears unlikely that climate-driven changes in THC will cause severe O2 depletion of the deep water masses of the MS in the foreseeable future