Distribution of calcareous nannoplankton in surface sediments along the northern KwaZulu-Natal Bight,South Africa

The coccolith assemblages from seafloor sediments over the inner shelf in the northern region of the KwaZulu- Natal Bight on the east coast of South Africa were identified and their distribution determined. In all, 29 Recent species and taxonomic groups, as well as 29 reworked species were recorded. The distribution of the Recent species appears to be governed by environmental features that have been documented in other studies: temperature, salinity, nutrient concentration and water circulation pattern, which reveals the long-term existence of a circulation cell in the sector between Durban Bay and the Thukela River. The outer edge of the cell consists of nutrient-enriched mixed layers and is characterised by an enhanced abundance of Gephyrocapsa oceanica, whereas the central region consists of a stratified nutrient-depleted water mass with elevated abundance of Umbilicosphaera sibogae, Florisphaera profunda, and a group of umbelliform species. The elevated levels of G. oceanica, coupled with the rarity of U. sibogae, F. profunda and the umbelliform species, confirm the presence of a permanent upwelling cell off Richards Bay. The maximum abundance of F. profunda found between Richards Bay and Lake Nhlabane indicates a region of nutrient-depleted (except for nitrite) conditions.     

Abundance and degree of residency of humpback dolphins Sousa plumbea in Mossel Bay,South Africa

Indian Ocean humpback dolphins Sousa plumbea inhabit nearshore waters from South Africa to eastern India. Humpback dolphins are vulnerable to conservation threats due to their naturally small population sizes and use of nearshore habitats, where human activities are highest. We investigated the abundance and residency of this species inhabiting Mossel Bay, South Africa, using photographic mark-recapture. Data were collected during 81 surveys in Mossel Bay between 2011 and 2013. Open population modelling using the POPAN parameterisation produced a ‘super-population’ estimate of 125 individuals (95% CI: 61–260) and within-year estimates of between 33 and 86 individuals (2011: 71 [95% CI: 30–168]; 2012: 33 [15–73], 32 [15–70]; 2013: 46 [20–108]). Although less appropriate, closed capture models were also run for comparison with previous studies in the region and generated similar, but slightly smaller, population estimates within each year. We compared our catalogue with opportunistic data collected from East London, Plettenberg Bay, De Hoop and Gansbaai. The only catalogue matches attained were between Plettenberg Bay (n = 44 identified) and Mossel Bay (n = 67 identified), separated by 140?km. Population exchange was moderate, with nine individuals resighted in multiple years between these two areas. This study supports previous findings of long-range movements for this species and provides a baseline from which to assess future impacts on the population.     

Sea level changes induced by local winds on the west coast of India

The contribution of atmospheric pressure and local wind to sea level variability at Goa (West coast of India) for the period 2007–2008 is investigated. Sea level data from a tide gauge are compared with measured local surface meteorological as well as oceanographic data. Multilinear regression analysis is used to resolve the dependence of sea level on various forcing parameters. The multilinear regression analysis performed over approx. 2-year data shows that the local surface meteorological data and water temperature account for the sea level variability only up to 6%. The accounted sea level variability increases to 25%, when the local wind and the surface currents obtained from satellite altimetry in the near vicinity of the study area are incorporated in the regression analysis. The contribution of local wind increases substantially when the regression is performed over a 2-month duration, and it is variable within the year. During the summer monsoon season (May–September), the sea level variability attributable to wind is up to 47% and 75%, respectively, for 2007 and 2008; however, it reduces to <20% during the winter monsoon (November–February) season. A significant part of the variability observed in sea level remains unaccounted for and is attributed to remote forcing.     

Estimation of the transports through the Strait of Gibraltar

An acoustic doppler current profiler (ADCP) is used to measure the currents and estimate the transports over the Camarinal Sill at the Strait of Gibraltar. The deepest measurements of the ADCP compare well with an underlying conventional current meter. The exchange interface between the Atlantic and the Mediterranean water is defined as the depth of the maximum vertical shear. The mean depth of the shear interface is 147 m. The time series of the depth of the interface and the currents are used to estimate the transports across the Strait. The resulting values are 0.78 Sv for the Atlantic inflow and −0.67 Sv for the Mediterranean outflow. The time series of the shear interface include fortnightly oscillations of 19 m. The time series of the transports are compared with the pressure and sea level difference records across the Strait. Linear multiple regression is used to estimate the (statistical) contribution of each parameter on the variation of transports. The cross strait sea level difference is well correlated with the Atlantic inflow and accounts for 57% of the variability of the transport records which improves to 78% when the fortnightly and monthly cycles are included in the linear regression. The Mediterranean outflow is best correlated with the along strait sea level difference which accounts for only 10% of the variability of the transport record. Again the addition of the M_sf and the MM cycles improves the percentage of the variance accounted for to 37%. The local, along strait wind component is significantly correlated with, both the Atlantic inflow and the across strait sea level difference.     

Sea level forcing in the Mediterranean Sea between 1960 and 2000

Sea level trends and inter-annual variability in the Mediterranean Sea for the period 1960–2000 is explored by comparing observations from tide gauges with sea level hindcasts from a barotropic 2D circulation model, and two full primitive equation 3D ocean circulation models, a regional one and the Mediterranean component of a global one,. In the 2D model, 50% of the sea level variance was found to result from the wind and atmospheric pressure forcing. In the 3D models, 20% of the sea level variance was explained by the steric effects. The sea level residuals at the tide gauges locations, calculated by subtraction of the 2D model output from the sea level observations are significantly correlated (r = 0.4) with the steric signals from the 3D models. After the removal of the atmospheric and the steric contributions the tide-gauge sea level records indicate a period where sea level was stable (1960–1975) and a period where sea level was rising (1975–2000) with rates in the range 1.1–1.8 mm/yr. A part of the residual trend can be explained by the contribution of local land movements (0.3 mm/yr) while its major part indicates a global signal, probably mass addition, appearing after 1975.     

On the effect of the sampling frequency of sea level measurements on return period estimate of extremes—Southern European examples

Estimates of extreme sea levels and return periods have been based mainly on hourly sampling rates. Technological development has enabled the sampling rates to increase and sampling rates of 5–10 min are becoming increasingly common. In this paper we explore the relationship between extreme sea levels and estimated return periods based on hourly and shorter sampling periods in three tide-gauges one at the Atlantic coasts of Spain (Coruña), one in the western Mediterranean (Malaga) and one in the N. Adriatic (Trieste). Significant differences of several centimetres are found in the hourly and 5 min extremes. These reflect in significant underestimation of the 50-year return levels which in Trieste reach 38 cm. A theoretical relationship between the high and the low sampling rate of extremes is also tested. Thus updated 50-year return levels for the Mediterranean and the coasts of the Iberian peninsula are produced assuming that the differences identified in the various stations generalise to other tide-gauge (hourly) records for which hourly values have been analysed earlier.     

A review of the trends observed in British Isles mean sea level data measured by tide gauges

This report presents an up-to-date review of the British Isles (BI) Mean Sea Level (MSL) data set obtained from tide gauges, and of the long-term secular trends in BI MSL. The data are of mixed quality, and not as copious as one would like for scientific analysis given the complexity of long-term sea and land level changes around BI coasts. Nevertheless, the small number of very long records can be studied effectively, and indicate that twentieth century secular trends in BI MSL are consistent with those obtained from NW Europe as a whole and with the bottom range of estimates for global average MSL change during the past 100 years. Century-timescale low-frequency 'accelerations' in MSL of the order of 0.4–0.8  mm  yr⁻¹  century⁻¹ are obtained from the three longest records, which are also similar to estimates from mainland Europe. 'Sea level indices' for the BI are constructed which can provide responsible agencies with a guide to the 'average state' of BI sea level. Combined ocean tide and storm surge ('tide + surge') numerical modelling is demonstrated to be a valuable tool in understanding part of the variability of MSL around the BI, although modelling of long-term changes is limited at present by the lack of adequate meteorological data sets from before 1955. Nevertheless, it is shown that, even if a complete meteorological modelling data set were available, it would not be able to account for all of the MSL variability. Finally, recommendations are made for the development of tide gauge and Global Positioning System (GPS) recording in the BI for the purpose of long-term MSL monitoring in the next century.     

Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies

We present an efficient,robust computational method for modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies.With appropriate mathematical treatments,the apparent numerical difficulties associated with singularities in computing elliptic integrals are completely removed.Using a boundary element discretization procedure,the governing equations are transformed into a linear algebra matrix equation that can be solved by straightforward Gauss elimination in one step without further ...     

用于自然灾害监测和减灾的低费用小卫星网

自然和人为的灾害每年都使远东的中国和她的周边国家蒙受了巨大的经济损失。为了能快速地对这些灾害作出反应以减少损失,有效和及时地从外层空间监测灾害已成为了一项迫切的国家需要。为了改进现行系统的覆盖范围和覆盖周期,曾建议采用地球观测卫星网。然而,常规遥感卫星的高成本至今还使得这项建议难以实施。萨瑞大学的萨瑞卫星技术有限公司(SSTL)已经研制了一套性能高、寿命长的微型卫星,该卫星利用先进的对地观测有效载荷,具有较强的星载处理能力。利用该套卫星就可以极低的成本获得从空中对地球的常规观测。每颗微型卫星只需费用约250万美元,因此,投资不到1800万美元就能构建由7颗卫星组成的卫星网(星座)。微型卫星重量轻、体积小,只需一个小的发射器就可以把整个网发射到低地球轨道中。