Source, density and composition of sympagic fauna in the Barents Sea

The sympagic fauna (= ice fauna) of the Barents Sea was investigated on nine different cruises in 1982-1988. Each cruise lasted from two to five weeks. Sampling techniques were based on scuba diving. The abundant sympagic organisms were the polar cod ( Boreogadus saida ) and the three amphipods Apherusa glacialis, Onisimus sp. and Gammarus wilkitzkii .
Mean biomass-values (wet weight) of the invertebrate sympagic fauna ranged from 0 to 2 g/m². Values above 0.001 g/m² were not recorded in five of the nine cruises. This is orders of magnitude lower than mean values recorded in multi-year ice north of Svalbard and in the Fram Strait where values between 1-10g/m² are quite common.
Apherusa glacialis seemed to have the best spreading capacity of the three most conspicuous amphipods. Gammarus wilkitzkii was most dependent on a passive transport with the ice.
Sympagic amphipods play an important part in a food chain from microalgae to polar cod and marine birds in areas covered with ice, especially in areas with multi-year ice.     

Numerical stabilization of Keplerian motion

The time transformation dt/ds=r is studied in detail and numerically stablized differential equations are obtained for =1,2, and 3/2. The case =1 corresponds to Baumgarte's results.     

Poisson distribution of the Iranian declustered earthquake catalog

Two main goals are considered in this paper: (1) modification and computation of the local coefficients of the space-time windows in the well-known declustering algorithm introduced by Gardner and Knopoff (1974) and (2) checking the independence of the Iranian mainshocks obtained from applying the new modified model. First, 21 of the well-documented earthquake sequences of Iran in the time period of 1972 to 2008 with the mainshock magnitude ranged from M _w = 5.4–7.1 were used to define the new local space-time windows of declustering. Generally, using these Iranian earthquake sequences led to introduce bigger space-time windows for the new model in comparison to the Gardner and Knopoff’s (1974) windows. In the next step, to control the independence of Iranian mainshocks, the events of the Iranian earthquake catalog in the time span of 1964–2010 with moment magnitude of M _w = 3.5–7.4 were used. In this respect, dependent events corresponding to the seven seismotectonic zones of Iran were removed using the new modified space-time windows. After declustering, the mainshock catalog was examined by the Kolmogorov–Smirnov goodness-of-fit test, and it was found to follow a Poisson distribution in all the studied seismotectonic zones of Iran. The same test on times between successive declustered events shows that the inter-event times of all catalogs follow an exponential distribution.     

Water leakage paths in the Doosti Dam,Turkmenistan and Iran

The Doosti Dam, with a reservoir capacity of 1,250 million cubic meters, was constructed on the Harirood River at the border of Turkmenistan and Iran. The reservoir is in direct contact with permeable formations on the right abutment of the dam including the Neyzar Sandstone, the Kalat Limestone and the Pesteleigh alternative layers of marlstone and sandstone. After the reservoir impoundment, several new springs and seepages emerged from these formations and the alluvium. The amount of leakage increased with the rise in reservoir water level. Fifteen kilograms of sodium fluorescein were injected into a 113-m deep borehole intersecting three permeable sandstone layers of the Pesteleigh formation. Dye was detected downstream of the grout curtain in boreholes and springs that were in direct contact with parts of the Pesteleigh formation having the same sandstone layers as the injection borehole. The dye velocity was in the range of diffuse flow, confirming the good performance of the grout curtain in the Pesteleigh formation. No dye was detected in the other formations because the injection borehole was not in direct contact with these formations. The hydraulic relation of the other formations with the reservoir was determined by considering direct contact of the formations with the reservoir, emergence of new springs and seepages after reservoir impoundment, correlation of time variations of the springs discharge and the borehole’s water level with the reservoir water level, and in some cases the hydrochemistry of the water. The results show that the Kalat and Neyzar formations are hydraulically connected to the reservoir, but the small amounts of leakage from these formations at a hydraulic gradient of 24% indicates good performance of the built grout curtain. The total reservoir leakage at maximum reservoir water level was 100 l/s which is insignificant compared with the 15 m³/s average annual release of the reservoir.     

Delineation of groundwater salinization in a coastal aquifer, Bousheher, South of Iran

The geochemical processes controlling chemical composition of groundwater are studied using hydrochemical and isotopic data in Abdan-Dayer coastal plain, south of Iran. The salinity of groundwater in the coastal plain ranges from 1,000, a fresh end-member, to more than 50,000 μS cm^?1, a saline end-member. Groundwater salinity increases from the recharge area toward areas with a shallow water table close to the Persian Gulf coast due to direct evaporation and sea water intrusion as confirmed by mixing binary diagrams, stable isotope content, and Br^?/Cl^? ratio. Groundwater flow pattern in the study area has been modified due to over-pumping of groundwater in recent years which resulted in further saline water migration toward fresh water and their mixing. The maximum mixing ratio is estimated about 15% in different parts of the study area according to chloride concentration.     

Anatomy and sedimentary model of a hooked spit (Sylt,southern North Sea)

A sedimentary model for hooked spit depositional systems based on ground‐penetrating radar and sedimentological data is presented. The recurved main spit of Sylt Island (southern North Sea) is dominated by migrating sand dunes; the investigated hooked spit exhibits a system of foredune ridges, oriented perpendicular to the dunes of the recurved spit. The development of the hooked spit is related closely to the presence of an adjacent tidal inlet, where strong tidal currents and a steep bathymetry prevent a further northward progradation of the main spit and trigger a deflection from northerly‐directed to easterly‐directed net sediment transport. Ground‐penetrating radar data and shallow sediment cores reveal the sedimentary architecture of the hooked spit in high resolution and allow the proposition of a genetic stratigraphic model. It is shown that the growth of the hooked spit is controlled by the interplay of alongshore migrating foreshore beach drifts under fair‐weather conditions and strong erosional events, interpreted as the result of rare severe storms. These storms may excavate scarps in the backshore, which play an important role in the development of foredune ridges. Accelerator mass spectrometry ¹⁴C ages indicate an absolute age of at least 1300 years for the hooked spit, which possibly correlates with strengthened erosion of the main spit. In contrast to the main spit, where the sediment budget is negative nowadays, growth of the hooked spit beach accelerated significantly during the last decades. This effect can probably be attributed to enhanced beach‐nourishments updrift along the main spit and makes the investigated hooked spit a natural laboratory to study the influence of increasing sediment supply into a system developing under the conditions of sea‐level rise. The study shows that the same external forces lead to distinct progradational processes along one barrier‐spit system.     

A study of the climatic system in the Barents Sea

The climatic conditions in the Barents Sea are mainly determined by the influx of Atlantic Water. A homogeneous wind-driven numerical current model was used to calculate the fluctuations in the volume flux of Atlantic Water to the Barents Sea which are caused by local wind forcing. The study period is from 1970 to 86. When compared with observed variations in temperature, ice coverage, and air pressure, the results show remarkably good agreement between all three parameters. The climate system of the Barents Sea is discussed with emphasis on the interrelations and feedback mechanisms between air, sea, and ice.