The limnogeology-ETH coring system

Various methods are available for coring in lakes. We have developed an integrated coring system based on a modified Kullenberg poston-corer principle which is particularly useful for multiple coring in deep lakes. The selection of sites is guided by concurrent high-resolution (3.5 kHz) continuous seismic profiling. The system is modular for simple transport, and includes a very reliable tripweight gravity corer which uses the same plastic liners as the piston corer. Piston-core lengths are variable in 2, 4, or 5 m sections up to 16 m. This system has been successfully deployed in glacially deepened perialpine lakes (Lakes Zürich, Zug, Greifensee, Lucerne, Walensee, Constance, Murten, Neuchâtel, Geneva, Thun, Brienz, Maggiore, Lugano, Iseo, Garda, d'Annecy, Bourget and Ammersee), deep rift lakes of Africa (Turkana, Albert, Edward, Kiwu), Lake Ohrid (Jugoslavia), Lake Van (Turkey), Qinghai Lake (China), and in very shallow hypersaline lakes Urmia (Iran) and Great Salt Lake (USA). Following numerous requests, this paper describes the system concept and constructional features that have been refined over the last 12 years. Development has stressed increasing simplification and increased reliability.     

High order discontinuous Galerkin method for simulating miscible flooding in porous media

We present a high-order method for miscible displacement simulation in porous media. The method is based on discontinuous Galerkin discretization with weighted average stabilization technique and flux reconstruction post processing. The mathematical model is decoupled and solved sequentially. We apply domain decomposition and algebraic multigrid preconditioner for the linear system resulting from the high-order discretization. The accuracy and robustness of the method are demonstrated in the convergence study with analytical solutions and heterogeneous porous media, respectively. We also investigate the effect of grid orientation and anisotropic permeability using high-order discontinuous Galerkin method in contrast with cell-centered finite volume method. The study of the parallel implementation shows the scalability and efficiency of the method on parallel architecture. We also verify the simulation result on highly heterogeneous permeability field from the SPE10 model.     

The slow rotation of 253 Mathilde

CCD photometry of the NEAR mission fly-by target 253 Mathilde is presented. Measurements taken during 52 nights of observations, from February to June 1995, allow a rotation period of 17.406±0.010 days and a lightcurve amplitude of 0.45±0.02 mag to be determined. A B-V color index of 0.67±0.02 and a V-R of 0.35±0.02 are measured, which are compatible with C-type membership. The determination of the phase relation results in H = 10.28±0.03 and G = 0.12±0.06. Indications that the lightcurve is not strictly singly-periodic are found. A power-spectrum analysis detects a secondary frequency f₂ = 0.0322±0.0010 d⁻¹, which is interpreted as evidence for a complex rotation state.     

Middlemen,a critical social-ecological link in coastal communities of Kenya and Zanzibar

This paper analyzes the middlemen–fishermen link in coastal communities along the coast of southern Kenya and Zanzibar, and explores effects of reciprocal agreements and credit arrangements on social-ecological feedbacks of coastal systems. The existence and generality of such arrangements are mapped and their effect on resource use and ecosystem dynamics is then explored. Data show that credit arrangements are widespread and that fishermen are bound by reciprocal agreements and financial guarantees during periods of lower catches that provide short-term stabilizing social effects. These arrangements create incentives which disconnect resource extraction from ecosystem dynamics and impede development of sustainable use practices. The role of middlemen is seldom accounted for in fisheries governance. Scenarios for the development of small-scale fisheries in the region are outlined and the function of middlemen is discussed considering the influence of external drivers. Policies that incorporate middlemen are recommended to improve the governance of fish stocks and coastal ecosystems in East Africa.     

Variation of hydrogeochemical characteristics of water in surface flows,shallow wells,and boreholes in the coastal city of Douala (Cameroon)

ABSTRACT

Groundwater is used by 3?million inhabitants in the coastal urban city of Douala, Cameroon, but comprehensive data are too sparse for it to be managed in a sustainable manner. Hence this study aimed to (1) assess the potability of the groundwater; (2) evaluate the spatial variation of groundwater composition; and (3) assess the interaction and recharge mechanisms of different water bodies. Hydrogeochemical tools and methods revealed the following results in the Wouri and Nkappa formations of the Douala basin, which is beneath Douala city: 30% of water samples from hand-dug wells in the shallow Pleistocene alluvium aquifer were saline and highly mineralized. However, water from boreholes in the deeper (49–92 m depth) Palaeocene aquifer was saline-free, less mineralized and potable. Water in the shallow aquifer (0.5–22 m depth) was of Na⁺-K⁺-Cl^?-NO₃^? type and not potable due to point source pollution, whereas Ca⁺-HCO₃^? unpolluted water dominates in the deeper aquifer. Water in the deep and shallow aquifers indicates the results of preferential flow pass and evaporative recharge, respectively. Possible hydrogeochemical processes include point source pollution, reverse ion exchange, remote recharge areas and mixing of waters with different chemical signatures.

EDITOR D. Koutsoyiannis ASSOCIATE EDITOR M.D. Fidelibus     

Perceptions of climate change: Linking local and global perceptions through a cultural knowledge approach

Understanding public perceptions of climate change is fundamental to both climate science and policy because it defines local and global socio-political contexts within which policy makers and scientists operate. To date, most studies addressing climate change perceptions have been place-based. While such research is informative, comparative studies across sites are important for building generalized theory around why and how people understand and interpret climate change and associated risks. This paper presents a cross-sectional study from six different country contexts to illustrate a novel comparative approach to unraveling the complexities of local vs global perceptions around climate change. We extract and compare ‘cultural knowledge’ regarding climate change using the theory of ‘culture as consensus’. To demonstrate the value of this approach, we examine cross-national data to see if people within specific and diverse places share ideas about global climate change. Findings show that although data was collected using ethnographically derived items collected through place-based methods we still find evidence of a shared cultural model of climate change which spans the diverse sites in the six countries. Moreover, there are specific signs of climate change which appear to be recognized cross-culturally. In addition, results show that being female and having a higher education are both likely to have a positive effect on global cultural competency of individuals. We discuss these result in the context of literature on environmental perceptions and propose that people with higher education are more likely to share common perceptions about climate change across cultures and tentatively suggest that we appear to see the emergence of a ‘global’, cross-cultural mental model around climate change and its potential impacts which in itself is linked to higher education.     

Reconstructing mid-to-recent Holocene paleoenvironments in the vicinity of ancient Amarynthos (Euboea,Greece)

This article examines the shoreline evolution and human occupation in the vicinity of the important archeological site of Amarynthos (Euboea Island, Greece) over the last six millennia. Archeological evidence indicates a continuous occupation of the site from the Bronze Age to the Roman period and the site is well-known, thanks to the existence of a sanctuary dedicated to the goddess Artemis. Based on the study of four boreholes, a paleogeographic reconstruction of the coastal landscape is proposed. Facies were determined based on mollusc identification, and sedimentology based on grain-size measurements (hand sieving for the fraction above 2?mm and LASER technique for particles below 2?mm) and loss-on-ignition. In addition, a series of 12 AMS radiocarbon dates define a reliable chronostratigraphy. Results suggest the presence of a fully marine environment from the early Holocene to ca. 2600–2400?cal. BC, which developed into a brackish environment from ca. 2600–2400?cal. BC to ca. 750?cal. BC due to the deltaic progradation of the nearby stream (Sarandapotamos River). From ca. 750?cal. BC onward, coastal swamps prevailed in the study area. Human-environmental interaction is discussed and particular attention is paid to the paleolandscape configuration of Amarynthos.