Local Climate Parameters Research Articles

Distribution patterns of different age classes and sexes in a Tyrrhenian population of Talitrus saltator (Montagu)

Temporal and spatial distribution patterns of a population of Talitrus saltator living on the Tyrrhe- nian coast of Tuscany (Italy) were studied. Bimonthly surveys were performed from March 1991 to January 1992 along transects using a standard system of pitfall traps and sieves for surface-active and burrowed indi- viduals, respectively. Captured individuals were subdi- vided into sex and age classes (on the basis of the number of articles of the flagellum of the second an- tenna). Abundances were calculated for each sampling period and sex ratios were determined. For each sampling period the mean hour of surface activity was calculated together with the mean zonation of both surface-active and burrowing sandhoppers belonging to the different sex and age classes. Shifts in mean zonation between the resting and active phase were also deter- mined. For each category of sex, age, and reproductive phase, simple and multiple regression analyses were used to find relationships of the mean zonation of surface- active animals with climatic data, and of the number of burrowed individuals with surface sand parameters recorded in correspondence to the sieves. On the whole, the results show that this Tyrrhenian population of T. saltator exhibited a bivoltine reproductive cycle and that the sex ratios of active sandhoppers were male or female biased according to the season. The variations in the mean hour of surface activity and in the zonation patterns of sandhoppers depended more on the age than on the sex. Furthermore distribution patterns were generally related to seasonal changes in the local climatic and substrate parameters. The observed differences be- tween burrowing and activity zonations were interpreted on the basis of the nocturnal migrations of the different categories.

GCM analysis of local influences on ice core δ signals

A high resolution GCM is used to examine the effect of changes in local surface climate parameters on the ice sheets that can influence the interpretation of the isotopic signal of the ice from deep cores. The model suggests that the 10°C difference between the LGM surface temperature deduced from borehole thermometry and that deduced from the water isotope analysis to a great extent may be due to a modification of the precipitation seasonality in central Greenland. For central East Antarctica, the model tends to suggest a weak opposite bias.

Small scale secondary CaCO 3 accumulations in selected sections of the European loess belt. Morphological forms and potential for paleoenvironmental reconstruction

Eighteen important Quaternary loess paleosoil sites have been studied across the European loess belt. They included approximately 50 buried soils, the over and/or underlying loess and the present-day surface soils (where possible). From the numerous types of secondary CaCO 3 accumulations recognized, only the small scale accumulations are discussed in this paper, including calcified root cells, CaCO 3 hypocoatings, needle-fiber calcite, powdery calcite coatings, earthworm biospheroliths, and calcite pseudomorphs on gypsum. Most of the features studied are found in the rhizosphere microecosystem. Each of these features showed a unique relationship with organic matter, micro-organism and plant distribution, moisture and leaching processes. For example, the exceptional abundance of calcified root cells is an indicator of a long stability of soil surface during favorable climatic conditions. Needle-fiber calcite is related to biomineralization of saprophytes in soils with sufficient moisture and decomposing organic matter. The presence of powdery calcite coatings covering clay and Mn coatings in non-calcareous soils indicates a change from leaching to non-leaching soil moisture regimes. Earthworm biospheroids provide arguments for a relative stability of the soil surface, without rapid burial processes or drastic, prolonged water stress. Finally, gypsum pseudomorphs are indicators of changes in local climatic parameters. In addition to a discussion of the genesis and the dynamics of the various accumulations, several examples are given to show how these accumulations can be used as indicators of a changing environment, such as renewed loess deposition, the extent of drought or varying intensity of leaching during the year. To conclude, various forms of small scale secondary CaCO 3 accumulations are common in the loess paleosoils and each type has the potential to contribute to a better understanding of the evolution of the paleoenvironment. Therefore, it is proposed that their individual presence or absence throughout the pedostratigraphical levels and throughout the (paleo)topography should be recorded at all scales of observation.

Bioclimatic impacts of the 1994 smoke haze event in Southeast Asia

A smoke haze event of unprecedented magnitude which occurred in southeast Asia 1994 is statistically evaluated for its impact on regional and global climate using climatic and air quality data from Singapore, and by comparison with the better-known smoke pollution episode resulting from the Kuwait oil fires of 1991. Several local climatic parameters were found to be closely related to air quality on a daily basis. Mean data for the haze period in 1994 appeared to differ significantly from the long-term means for the same period in previous years, with the exception of daily mean air temperature and mean Global Solar Radiation (GSR). The latter is in spite of the inverse relationship between daily GSR and pollution levels. An ENSO-related influence on regional climate (masking some of the perceived regional impacts of the haze) is invoked to explain the apparent contradiction. The significance of the smoke haze at global scale is considered for its impact on the global carbon budget, especially due to the combustion of peat in the coastal lowlands of Sumatra and Kalimantan. The scarcity of available ecological data is regretted and recommendations are made for future cooperation over monitoring and research between scientists and government bodies from the countries in the southeast Asian region.

Rhythmic bedding produced in Cretaceous pelagic carbonate environments: Sensitive recorders of climatic cycles

Various types of rhythmic bedding are prominent features of Cretaceous pelagic carbonates. These bedding rhythms are the primary depositional result of variations in carbonate productivity, terrigenous dilution, redox conditions and/or the energy of bottom currents. Each bedding cycle type is different in its expression in the stratigraphic record but ultimately was caused by rhythmic climatic variations related to variations in receipt of solar insolation as the result of the earth's orbital characteristics, the so‐called Milankovitch cycles. Stratigraphic sequences may contain a single bedding cycle type or a composite of several types. Although sediment type and sedimentary structures were influenced by variations in local climatic, oceanographic, tectonic, and diagenetic parameters, pelagic carbonate environments during the Cretaceous were particularly sensitive recorders of orbitally induced changes in worldwide climate.