Holocene coastal change in the ancient harbor of Yenikap?-?stanbul and its impact on cultural history

An extensive rescue excavation has been conducted in the ancient harbor of ?stanbul (Yenikap?) by the Sea of Marmara, revealing a depositional sequence displaying clear evidence of transgression and coastal progradation during the Holocene. The basal layer of this sequence lies at 6 m below the present sea level and contains remains of a Neolithic settlement known to have been present in the area, indicating that the sea level at ~ 8-9 cal ka BP was lower than 6 m below present. Sea level advanced to its maximum at ~ 6.8-7 cal ka BP, drowning Lykos Stream and forming an inlet at its mouth. After ~ 3 cal ka BP, coastal progradation became evident. Subsequent construction of the Byzantine Harbor (Theodosius; 4th century AD) created a restricted small basin and accumulation of fine-grained sediments. The sedimentation rate was increased due to coastal progradation and anthropogenic factors during the deposition of coarse-grained sediments at the upper parts of the sequence (7th-9th centuries AD). The harbor was probably abandoned after the 11th century AD by filling up with Lykos Stream detritus and continued seaward migration of the coastline.     

Revisiting the Climatology of Atmospheric Blocking in the Northern Hemisphere

In addition to the occurrence of atmospheric blocking,the climatology of the characteristics of blocking events,including duration,intensity,and extension,in four seasons over the Northern Hemisphere was analyzed for the period 1950-2009.The seasonality and spatial variations of these characteristics were studied according to their longitudinal distributions.In general,there were sharp discrepancies in the blocking characteristics between winter and summer,and these differences were more prominent over the Atlantic and Pacific Oceans.The blocking not only occurred more frequently but also underwent stronger amplification in winter;likewise,the blocking occurred less frequently and underwent weaker amplification in summer.There are very strong interrelationships among different blocking characteristics,suggesting that they are supported by similar physical factors.In addition,the relationship between blocking over different regions and East Asian circulation was examined.Ural-Siberia is a major blocking formation region in all seasons that may exert a downstream impact on East Asia.The impact is generally weak in summer,which is due to its lower intensity and smaller duration.However,the extratropical circulation over East Asia in summer can be disturbed persistently by the frequent occurrence of blocking over the Asian continent or the Western Pacific.In particular,the blocking frequency over the Western Pacific significantly increased during the study period.This climatological information provides a background for studying the impact of blocking on East Asian circulation under both present and future climate conditions.     

Electron density and temperature in the Io plasma torus from Ulysses thermal noise measurements

During the Ulysses flyby of Jupiter, the spacecraft crossed the outer part of the Io plasma torus along a basically North-to-South trajectory at a Jovicentric distance of about 8R_J. The quasi-thermal noise measured by the Unified Radio and Plasma Wave (URAP) experiment is used to deduce the electron density and temperature along the trajectory. The density is deduced from the upper hybrid frequency line and the temperature from the spin modulation of Bernstein waves. These results are used to build a simplified Gaussian model of the torus. The density profile is roughly symmetric with respect to the centrifugal equator, with a scale height of about 0.9R_J. The density at equator crossing is twice as large as that expected from the Divine-Garrett Voyager-based model at the same radial distance. The density scale height is lower than that found by Voyager 1; it is consistent with an ion temperature of about 5 × 10⁵K, assuming an effective mass of about 20 proton masses. The fitting of the pressure distribution, symmetric with respect to the centrifugal equator, yields a cold electron temperature of about 1.4 × 10⁵K at the equator, which is of the same order of magnitude as found by Voyager 1.     

Characteristics of easterly-induced snowfall in Yeongdong and its relationship to air-sea temperature difference

Characteristics of snowfall episodes have been investigated for the past ten years in order to study its association with lowlevel stability and air-sea temperature difference over the East Sea. In general, the selected snowfall episodes have similar synoptic setting such as the Siberian High extended to northern Japan along with the Low passing by the southern Korean Peninsula, eventually resulting in the easterly flow in the Yeongdong region. Especially in the heavy snowfall episodes, convective unstable layers have been identified over the East sea due to relatively warm sea surface temperature (SST) about 8～10°C and specifically cold pool around 1～2 km above the surface level (ASL), which can be derived from Regional Data Assimilation and Prediction System (RDAPS), but that have not been clearly exhibited in the weak snowfall episodes. The basic mechanism to initiate snowfall around Yeongdong seems to be similar to that of lake-effect snowstorms around Great Lakes in the United States (Kristovich et al., 2003). Difference of equivalent potential temperature (θ _e ) between 850 hPa and surface as well as difference between air and sea temperatures altogether gradually began to increase in the pre-snowfall period and reached their maximum values in the course of the period, whose air (850 hPa) — sea temperature difference and snowfall intensity in case of the heavy snowfall episodes are almost larger than 20°C and 6 tims greater than the weak snowfall episodes, respectively. Interestingly, snowfall appeared to begin in case of an air-sea temperature difference exceeding over 15°C. The current analysis is overall consistent with the previous finding (Lee et al., 2012) that an instabilityinduced moisture supply to the lower atmosphere from the East sea, being cooled and saturated in the lower layer, so to speak, East Sea-Effect Snowfall (SES), would make a low-level ice cloud which eventually moves inland by the easterly flow. In addition, a longlasting synoptic characteristics and convergence-induced invigoration also appear to play the important roles in the severe snowstorms. Improvements in our understanding of mesoscale sea-effect snowstorms require detailed in-situ and remote sensing observations over and around East Sea since observations of the concurrent thermodynamic and microphysical characteristics have not been available there and this study emphasizes the importance of low level stability as quantitative estimation of moist static energy generation over the East Sea.     

Thermochronology of the PoSen complex,northern Vietnam: Implications for tectonic evolution in SE Asia

The PoSen complex, located closely adjacent to the southwestern margin of the Red River shear zone represents the uplifted basement of north Vietnam and may record the motion of the shear zone. However, its thermochronological history has not been fully examined yet. Here we applied U–Pb and ⁴⁰Ar/³⁹Ar dating methods to reveal its thermochronological history. U–Pb analysis of composite zircon grains by TIMS yielded an average age of 760 ± 25 Ma, clustering on the concordia line. Twelve SHRIMP U–Pb analyses also yielded a consistent result of 751 ± 7 Ma. Along with the geochemical features, the U–Pb dating results suggest the PoSen complex was a late Proterozoic magmatic complex, which could correspond to the Chengjiang orogeny, a widespread thermal event in southwest China. Results of ⁴⁰Ar/³⁹Ar dating of micas and K-feldspars were in the range of 36–30 Ma, revealing a rapid cooling and exhumation history of the PoSen complex during the late Paleogene. The time span of cooling and exhumation of the PoSen complex is slightly older than the main cooling phases of the Ailao Shan–Red River (ASRR) metamorphic massifs (28–17 Ma), but is synchronous with the early igneous activity stage in the eastern Indo-Asian collision zone of southeast China and north Vietnam. Owing to the ongoing debate about the initiation and offset of the ASRR shear zone, the tectonic force for the late Paleogene cooling of the PoSen complex is still inconclusive. The rapid exhumation of the PoSen complex could be in response to either the detachment of the Neo-Tethyan slab or a transpressional phase of continental subduction along the ASRR shear system in the eastern Indo-Asian collision zone.     

Terrestrial low-frequency bursts: Escape paths of radio waves through the bow shock

From the analysis of 119 low-frequency (LF) burst spectra observed onboard the Wind spacecraft, we propose an interpretation of the frequency-time characteristics including the low frequency cutoff of the LF burst spectra, and we use these characteristics to sound the bow shock structure at large tailward distances from Earth. When observed from within the solar wind, LF bursts appear to be made of two spectral components. The high frequency one is bursty and observed above twice the solar wind plasma frequency f_psw. The low frequency one is diffuse (ITKR) and its spectrum extends from about 2f_psw to a cutoff frequency f_c not much higher than f_psw; its onset time δt(f) increases as the frequency f decreases. For each of the 119 events observed from near the Lagrange point L1, the solar wind density variations were measured and the variations of the density jump across the shock calculated from plasma data all along a shock model over more than 2000R_E. But, except for a few events, neither the solar wind overdensities nor the shock density barrier can prevent waves with frequencies below f_c from reaching the spacecraft. Scattering on plasma density inhomogeneities was then introduced to account for the propagation of the LF burst waves in the magnetosheath, from near Earth to their escape point through the bow shock at a frequency-dependent distance |X_esc(f)| (GSE), and then in the solar wind to the spacecraft. In such media, at frequencies between 2f_psw and f_psw, the bulk speed of the scattered waves decreases rapidly as f decreases, and this accounts for the observed variations of the onset time δt(f). Angular scattering can also account for the observed cutoff at f_c if the distance |X_esc(f)| increases exponentially when f/f_psw decreases. As the shock model we used meets that requirement, we consider that this model is valid, which implies that the bow shock still exists beyond 1000R_E from the Earth. The observed decrease of the average spectral intensity of the LF burst between about 1.5f_psw and 2f_psw can also be explained by the scattering in the solar wind if we take into account the angular distribution of the rays when they leave the bow shock.     

A semi‐analytical solution for groundwater responses to stream‐stage variations and tidal fluctuations in a coastal aquifer

A two‐dimensional semi‐analytical solution to analyse stream–aquifer interactions in a coastal aquifer where groundwater level responds to tidal effects is presented. The conceptual model considered is a two‐dimensional subsurface system with stream and coastline boundaries at right angles. The dimensional and non‐dimensional boundary value problems were solved for water level in the aquifer by successive application of Laplace and Fourier transform techniques, and the results were obtained by numerical inversion of the transformed solution. The solution was then verified by reducing the solutions to one‐dimensional known problems and comparing the results with those from previous studies. Hypothetical examples were used to examine the characteristics of water‐level variations due to the variations in stream stage and the fluctuations in tide level. Sensitivity analysis indicated that streambed leakance has no influence over the amplitude of groundwater fluctuations, but that the effect of stream stage increases with increasing leakance. Little difference was observed in the water level for different aquifer penetration ratios with narrow stream width. Increases in streambed leakance caused increases in the effect of aquifer penetration by the stream on the water level. An increased specific yield value resulted in decreased amplitude of water fluctuations and mean water level, and showed that water‐level variations due to stream and tidal boundaries are sensitive to specific yield. Copyright © 2006 John Wiley & Sons, Ltd.     

Carbon co-benefits of tighter SO2 and NOx regulations in China

Air pollution has been recognized as a significant problem in China. In its Twelfth Five Year Plan, China proposes to reduce SO₂ and NO_x emissions significantly, and here we investigate the cost of achieving those reductions and the implications of doing so for CO₂ emissions. We extend the analysis through 2050, and either hold emissions policy targets at the level specified in the Plan, or continue to reduce them gradually. We apply a computable general equilibrium model of the Chinese economy that includes a representation of pollution abatement derived from detailed assessment of abatement technology and costs. We find that China's SO₂ and NO_x emissions control targets would have substantial effects on CO₂ emissions leading to emissions savings far beyond those we estimate would be needed to meet its CO₂ intensity targets. However, the cost of achieving and maintaining the pollution targets can be quite high given the growing economy. In fact, we find that the near term pollution targets can be met while still expanding the use of coal, but if they are, then there is a lock-in effect that makes it more costly to maintain or further reduce emissions. That is, if firms were to look ahead to tighter targets, they would make different technology choices in the near term, largely turning away from increased use of coal immediately.     

Valuing direct use values of wetlands: A case study of Tam Giang–Cau Hai lagoon wetland in Vietnam

Tam Giang–Cau Hai lagoon wetland directly or indirectly provides the likelihoods for about 300,000 persons living around as well as on the lagoon. Due to expansion of aquacultures, intensive fishing, and lack of an appropriate management scheme, the biological resources in the lagoon are degraded. This study provides information on the direct use values of the lagoon wetland, using market price approach. This information on economic values can be used for designing new policies and making trade-offs among alternative management options for the lagoon wetland.