Centennial-to-millennial-scale periodicities of Holocene climate and sediment injections off the western Barents shelf, 75°N

At the western continental margin of the Barents Sea, 75°N, hemipelagic sediments provide a record of Holocene climate change with a time resolution of 10-70 years. Planktic foraminifera counts reveal a very early Holocene thermal optimum 10.7-7.7 kyr BP, with summer sea surface temperatures (SST) of 8°C and a much enhanced West Spitsbergen Current. There was a short cooling between 8.8 and 8.2 kyr BP. In the middle and late Holocene summer, SST dropped to 2.5°-5.0°C, indicative of reduced Atlantic heat advection, except for two short warmings near 2.2 and 1.6 kyr BP. Distinct quasi-periodic spikes of coarse sediment fraction (with large portions of lithic grains, benthic and planktic foraminifera) record cascades of cold, dense winter water down the continental slope as a result of enhanced seasonal sea ice formation and storminess on the Barents shelf over the entire Holocene. The spikes primarily cluster near recurrence intervals of 400-650 and 1000-1350 years, when traced over the entire Holocene, but follow significant 885-/840- and 505-/605-year periodicities in the early Holocene. These non-stationary periodicities mimic the Greenland-[Formula: See Text]Be variability, which is a tracer of solar forcing. Further significant Holocene periodicities of 230, (145) and 93 years come close to the deVries and Gleissberg solar cycles.     

Time-Series Modeling and Prediction of Global Monthly Absolute Temperature for Environmental Decision Making

A generalized,structural,time series modeling framework was developed to analyze the monthly records of absolute surface temperature,one of the most important environmental parameters,using a deterministicstochastic combined(DSC) approach.Although the development of the framework was based on the characterization of the variation patterns of a global dataset,the methodology could be applied to any monthly absolute temperature record.Deterministic processes were used to characterize the variation patterns of the global trend and the cyclic oscillations of the temperature signal,involving polynomial functions and the Fourier method,respectively,while stochastic processes were employed to account for any remaining patterns in the temperature signal,involving seasonal autoregressive integrated moving average(SARIMA) models.A prediction of the monthly global surface temperature during the second decade of the 21st century using the DSC model shows that the global temperature will likely continue to rise at twice the average rate of the past 150 years.The evaluation of prediction accuracy shows that DSC models perform systematically well against selected models of other authors,suggesting that DSC models,when coupled with other ecoenvironmental models,can be used as a supplemental tool for short-term(～10-year) environmental planning and decision making.     

Juvenile CO2 in enderbites of Tromøy near Arendal, southern Norway: a fluid inclusion and stable isotope study

The enderbites from Tromøy in the central, granulite facies part of the Proterozoic Bamble sector of southern Norway contain dominantly CO₂ and N₂ fluid inclusions. CO₂ from fluid inclusions in quartz segregations in enderbites was extracted by mechanical (crushing) and thermal decrepitation and the δ¹³C measured. Measurement was also made on samples washed in 10% HCl, oxidized with CuO at high temperatures, and step-wise extracted with progressive heating. Results between the different techniques are systematic. The main results show δ¹³C of -4.5±1.5% for crushing and -7±2% for thermal decrepitation. δ¹³C is about constant for CO₂ extracted at different temperatures and points to a homogeneous isotopic composition. Due to the presence of carbonate particles and/or induced contaminations for the extraction by thermal decrepitation, the results for the crushing experiments are assumed the most reliable for fluid-inclusion CO₂. Very low values of δ¹³C have not been found in enderbite samples and δ¹³C combined with δ¹⁸O of the host quartzes (8-11%) indicates juvenile values. In addition, the fluid inclusions were examined by microthermometry and Raman analysis and host quartz by acoustic emission and cathodoluminescence. CO₂ fluid inclusions have varying densities with a frequency maximum of 0.92 g cm^-3 and generally do not concur with trapping densities at granulite conditions. Textures show that CO₂ must have been trapped in fluid inclusions in one early event, but transformed to different extents during late isothermal uplift without important fractionation of isotope compositions. The present data support a model of intrusion and crystallization of a CO₂-rich enderbitic magma at granuiite conditions.     

In situ produced 14C by cosmic ray muons in ablating Antarctic ice

Samples of a core (52 m) of ablating Antarctic ice were analysed for ¹⁴CO and ¹⁴CO₂ by accelerator mass spectrometry. The data were compared with a ¹⁴C in situ production model that includes muon capture in addition to oxygen spallation by neutrons. The analysis reveals significant in situ ¹⁴C at depths below 10 m, which we attribute to ¹⁴C production by cosmic ray muons. The age of the ice was determined as 9.3±0.4 ¹⁴C ka BP.     

RUNOFF GENERATION AND SOIL EROSION IN SMALL AGRICULTURAL CATCHMENTS WITH LOESS-DERIVED SOILS

Over a two-year period, rainfall, runoff and sediment output were measured in six small agricultural catchments (3–10 ha) in south Limburg (The Netherlands). These measurements were needed for validation of an erosion model for South Limburg (LISEM). In this paper, results of the measurements are presented and processes that determine surface runoff and sediment yield during winter and summer rainfall are identified. Before the start of the measurement programme, surface slaking and crust formation on the erodible loess soils were thought to be the main cause of overland flow and soil erosion in South Limburg. This was the starting point for soil conservation measures in the area. The measurement results discussed in this paper show that in some catchments much runoff occurred in winter and that soil moisture storage capacity may be just as important for runoff generation as infiltration capacity. Therefore, when modelling soil erosion and optimizing erosion control measures for South Limburg, runoff generation through Hortonian as well as through saturation overland flow must be considered.     

Integration of smallholder wetland aquaculture–agriculture systems (fingerponds) into riparian farming systems on the shores of Lake Victoria, Kenya: socio-economics and livelihoods

This paper presents the results of experimental fingerponds: an integrated flood recession aquaculture–agriculture production system in the Lake Victoria wetlands in Kenya. The overall aim of the study is to assess the potential of fingerponds as a sustainable wetland farming system for improving food security at the subsistence level and within the context of the existing livelihood activities. The contribution of this new activity to rural household livelihoods is evaluated. Since it is a sustainable technology, based on natural events, the production level is intermediate and the benefits may not be high in the short term. Economic analysis shows that the gross margin and net income of fingerponds is about 752 and 197 Euros per hectare per year, respectively. This is about an 11% increase in the annual gross margin of an average rural household around Lake Victoria. The additional per capita fish supply is 3 kg per season or more from a 192 m² pond. The potential fish protein supply of 200 kg/ha is high compared with most existing terrestrial protein production systems. Fingerponds have the potential to contribute to household food security and to improve livelihoods. Sensitivity analysis indicates that biophysical variations, which may occur from one wetland to another, have implications for the functioning, and consequently the economic performance, of fingerponds. This reinforces the need for the integration of these systems into other household activities to buffer the household against potential risk.