Open and coastal seas interactions south of Japan represented by an ensemble Kalman filter

We investigated the feasibility of the ensemble Kalman filter (EnKF) to reproduce oceanic conditions south of Japan. We have adopted the local ensemble transformation Kalman filter algorithm based on 20 members’ ensemble simulations of the parallelized Princeton Ocean Model (the Stony Brook Parallel Ocean Model) with horizontal resolution of 1/36°. By assimilating satellite sea surface height anomaly, satellite sea surface temperature, and in situ temperature and salinity profiles, we reproduced the Kuroshio variation south of Japan for the period from 8 to 28 February 2010. EnKF successfully reproduced the Kuroshio path positions and the water mass property of the Kuroshio waters as observed. It also detected the variation of the steep thermohaline front in the Kii Channel due to the intrusion of the Kuroshio water based on the observation, suggesting efficiency of EnKF for detection of open and coastal seas interactions with highly complicated spatiotemporal variability.     

Effects of onshore and offshore topography on sea breeze circulation: An observational study at eastern Attica,Greece

Field measurements of wind, air temperature and humidity were taken at the eastern part of the Attika district in June 1991, to examine the topographic influences exerted on the local sea breezes. These influences are due either to the elongated Evia island, faced by the northern half of Attica coastline some tens of kilometers offshore, or to the coast-parallel range of Hymettos mountain, rising steeply 12 km onshore. The instrumentation consisted mainly of three tethered meteorological balloons released at characteristic sires (i.e., the coast, a location between shoreline and mountain foot and the mountain top) and three autographic ground-based anemometers operating at selected locations. Data from the ground-based and upper air stations of the Hellenic National Meteorological Service, as well as the diurnal weather maps were also obtained and analyzed. Observations were made under different synoptic wind and the latter was found to determine remarkably the significance of the topographic effects. A preliminary two-dimensional numerical approach was also made concerning the sea breeze capability to reach the Hymettos mountain top in the case of a weak opposing geostrophic flow.     

Mechanical shaking and soil water affect the growth of Psammochloa villosa in the Mu Us Sandland

The Mu Us Sandland is basically characterized by water shortage and high wind. Thus, wind-induced mechanical perturbation (MP) and soil water availability are likely to interact to affect plant growth. Since high water availability and MP can induce responses that are in the opposite direction, we hypothesized that MP effects on perennial grasses might be mitigated by increased soil water availability in the Mu Us Sandland. We counducted an experiment in which seedlings of Psammochloa villosa were subjected to two levels of MP (non-MP vs. MP 1 min d⁻¹) and two levels of water availability (200 ml d⁻¹vs. 400 ml d⁻¹) and measured three plant traits. MP significantly decreased plant height, total biomass, and root/shoot ratio. There were significant interactions between MP and soil water availability on plant height and root/shoot ratio. These findings imply that MP alone is a stressful factor for P. villosa and MP effects on its growth can be partially mitigated by increased soil water availability, and also suggest that P. villosa may respond to MP in a way that allows plants to survive in the windy semiarid environments.     

ESR dating in Song Terus cave (East Java, Indonesia)

Electron spin resonance (ESR) dating on teeth has been used to determine the antiquity of the human presence in the area of Gunung Sewu (East Java, Indonesia). The Song Terus cave is one of the archaeological sites located in this area, which has yielded an important collection of fossil bones and prehistoric lithic industry. ESR dating shows that this cave belongs to a karstic system which has been in place since Middle Pleistocene. The results of coupled ESR/Uranium-series dating indicates closed system for uranium in tooth tissues yielding ages of between 216 and 392 ka for the oldest archaeological levels, confirming the possibility of finding Middle Pleistocene human occupations in such karstic sites in Java.     

The effect of long-term aerial exposure on intertidal mudflat erodibility

Intertidal zones by definition are exposed to air at low tide, and the exposure duration can be weeks (e.g. during neap tides) depending on water level and bed elevation. Here we investigated the effect of varying exposure duration (6 h to 10 days) on intertidal mudflat erosion (measured using the EROMES device), where the effects of water content and biofilm biomass (using chlorophyll-a content as a proxy, Chl-a μg g⁻¹) were taken into account. Sediments were collected between spring and summer (in October 2018, January 2019 and February 2019) from an intertidal site in the Firth of Thames, New Zealand. Longer exposure duration resulted in more stable sediments [higher erosion threshold (Ƭ_cr, N m⁻²) and lower erosion rate (ER, g m⁻² s⁻¹)]. After 10 days, exposure increased Ƭ_cr by 1.7 to 4.4 times and decreased ER by 11.6 to 21.5 times compared with 6 h of exposure. Chl-a and water content changed with exposure duration and were significantly correlated with changes in Ƭ_cr and ER. The stability of sediments after two re-submersion periods following exposure was also examined and showed that the stabilizing effect of exposure persisted even though water content had increased to non-exposure levels. Re-submersion was associated with an increase in Chl-a content, which likely counteracted the destabilizing influence of increased water content. A site-specific model, which included the interplay between evaporation and biofilm biomass, was developed to predict water content as a function of exposure duration. The modelled water content (W_Mod.) explained 98% of the observed variation in water content (W_Obs.). These results highlight how the exposure period can cause subtle changes to erosion regimes of sediments. An understanding of these effects (e.g. in sediment transport modelling) is critical to predicting the resilience of intertidal zones into the future, when sea-level rise is believed to exacerbate erosion in low-lying areas. © 2020 John Wiley & Sons, Ltd.     

Toxicity of antifouling biocides to the intertidal harpacticoid copepod Tigriopus japonicus (Crustacea, Copepoda): effects of temperature and salinity

Intertidal harpacticoid copepods are commonly used in eco-toxicity tests worldwide. They predominately live in mid-high shore rock pools and often experience a wide range of temperature and salinity fluctuation. Most eco-toxicity tests are conducted at fixed temperature and salinity and thus the influence of these environmental factors on chemical toxicity is largely unknown. This study investigated the combined effect of temperature and salinity on the acute toxicity of the copepod Tigriopus japonicus against two common biocides, copper (Cu) and tributyltin (TBT) using a 2 × 3 × 4 factorial design (i.e. two temperatures: 25 and 35 °C; three salinities: 15.0‰, 34.5‰ and 45.0‰; three levels of the biocide plus a control). Copper sulphate and tributyltin chloride were used as the test chemicals while distilled water and acetone were utilised as solvents for Cu and TBT respectively. 96h-LC50s of Cu and TBT were 1024 and 0.149 μg l⁻¹ respectively (at 25 °C; 34.5‰) and, based on these results, nominal biocide concentrations of LC0 (i.e. control), LC30, LC50 and LC70 were employed. Analysis of Covariance using ‘concentration’ as the covariate and both ‘temperature’ and ‘salinity’ as fixed factors, showed a significant interaction between temperature and salinity effects for Cu, mortality increasing with temperature but decreasing with elevated salinity. A similar result was revealed for TBT. Both temperature and salinity are, therefore, important factors affecting the results of acute eco-toxicity tests using these marine copepods. We recommend that such eco-toxicity tests should be conducted at a range of environmentally realistic temperature/salinity regimes, as this will enhance the sensitivity of the test and improve the safety margin in line with the precautionary principle.     

Passive Seismic Experiment Mosaic - A Pilot Study of Mantle Lithosphere Anisotropy of the Bohemian Massif

We present results of an array study of seismic anisotropy beneath the Bohemian Massif (BM) showing distinct lateral and directional variations of the fast shear-wave polarization and split-delay time consistent with variations in the P-residual spheres, in which directional means of relative residuals are subtracted. Our analysis of the S- and P-wave anisotropy suggests that the mantle lithosphere of the BM consists of at least three large domains with different orientation of the large-scale fabric separated by sutures cutting most likely the whole lithosphere. Boundaries of the units are characterised by a null or small shear-wave splitting, as well as by smaller values in the P-residual spheres. We present self-consistent 3D anisotropic models of the lithosphere domains of the BM resulting from joint inversion of anisotropic parameters searching for a 3D orientation of mantle fabric. While in the Saxothuringian and Sudetes parts of the BM the (a, c) foliations dip prevailingly to the N-NW, they dip to the S and SW in the southern and eastern parts of the Moldanubian.     

Estimating the elastic parameters of anisotropic media using a joint inversion of P-wave and SV-wave traveltime error

A method is presented to estimate the elastic parameters and thickness of media that are locally laterally homogeneous using P‐wave and vertically polarized shear‐wave (SV‐wave) data. This method is a ‘layer‐stripping’ technique, and it uses many aspects of common focal point (CFP) technology. For each layer, a focusing operator is computed using a model of the elastic parameters with which a CFP gather can be constructed using the seismic data. Assuming local homogeneity, the resulting differential time shifts (DTSs) represent error in the model due to anisotropy and error in thickness. In the (τ?p) domain, DTSs are traveltimes Δτ that connect error in layer thickness z, vertical slowness q, and ray parameter p. Series expansion is used to linearize Δτ with respect to error in the elastic parameters and thickness, and least‐squares inversion is used to update the model. For stability, joint inversion of P and SV data is employed and, as pure SV data are relatively rare, the use of mode‐converted (PSV) data to represent SV in the joint inversion is proposed. Analytic and synthetic examples are used to demonstrate the utility and practicality of this inversion.