The carbon isotope biogeochemistry of the individual hydrocarbons in bat guano and the ecology of the insectivorous bats in the region of Carlsbad,New Mexico

The structures and ¹³C contents of individual alkanes extracted from bat guano found in the Carlsbad region of New Mexico can be related to both the photosynthetic pathways of the local plants and the feeding habits of the insects that support the bats.Carbon isotopic analyses show that equivalent numbers of C₃ and C₄ native plant species occupy the Pecos River Valley, a very significant feeding area for the Carlsbad bats. During the seasons when bats frequent the area, the agricultural crops consist principally of alfalfa and cotton, both C₃ plants.The molecular composition of the bat guano hydrocarbons is fully consistent with an insect origin. Two isotopically distinct groups of insect branched alkanes were discerned. These two groups of alkanes derived from two chemotaxonomically distinct populations of insects possessing distinctly different feeding habits. It is possible that one population grazes predominantly on crops whereas the other population prefers native vegetation. This and other isotopic evidence suggests that crop pests constitute a major percentage of the bats' diet.Because the guano sample was less than 40 years old, this material reflects the present day plant community in the Pecos River Valley. Future studies of more ancient guano deposits should reveal a measurable influence of both natural and man-induced vegetative changes with time upon the ¹³C content of the bat guano hydrocarbons.     

Correlation of δ<Superscript>18</Superscript>O and initial<Superscript>87</Superscript>Sr/<Superscript>86</Superscript>Sr ratios in Kirkpatrick basalt on Mt. Falla,transantarctic mountains

Theδ¹⁸O (SMOW) values of the Kirkpatrick Basalt (Jurassic) on Mt. Falla, Queen Alexandra Range, vary between +6.3‰ and +8.6‰ The apparent enrichment of these rocks in¹⁸O excludes the possibility that they were altered by interaction with aqueous solutions of meteoric origin. Theδ¹⁸O values of the flows correlate significantly with the initial⁸⁷Sr/⁸⁶Sr ratios and all major elements. These correlations confirm the hypothesis that the basalt magma was contaminated by rocks of the continental crust through which it was extruded. Estimates of the chemical composition of the basalt magma and the contaminant, based on extrapolations of the new oxygen data, generally confirm earlier estimates based on extrapolations of initial⁸⁷Sr/⁸⁶Sr ratios. The⁸⁷Sr/⁸⁶Sr ratio of the uncontaminated basalt was 0.7093 which indicates that magma may have originated by melting either in old Rb-enriched lithospheric mantle under Antarctica or in the overlying crust, or both.     

Geothermal investigations in the Bohus granite area in southwestern Sweden

Heat generation and heat flow were determined for the Bohus granite massif in western Sweden. This is the start of a major program concerning geothermal energy in Sweden. Neutron activation analyses, temperature measurements, thermal conductivity measurements have been carried out. As was expected the result, 76 mW m⁻², shows that even old Precambrian shields locally exhibit much higher values than normal.     

Melt density and the average composition of basalt

Densities of residual liquids produced by low pressure fractionation of olivine-rich melts pass through a minimum when pyroxene and plagioclase joint the crystallization sequence. The observation that erupted basalt compositions cluster around the degree of fractionation from picritic liquids corresponding to the density minimum in the liquid line of descent may thus suggest that the earth's crust imposes a density filter on the liquids that pass through it, favoring the eruption of the light liquids at the density minimum over the eruption of denser more fractionated and less fractionated liquids.     

Observations on the asexual reproductive activities of the sessile stages of the sea nettleChrysaora quinquecirrha (Scyphozoa)

Twenty-seven colonies of wild scyphistomae ofChrysaora quinquecirrha were observed for a period of ten weeks during the summer. Asexual activities of individual organisms were recorded several times each week. Polyps most often proceeded to strobilate in mid-June and then strobilate a second time 18 days later. They then detached and changed position by means of stolons and then produced podocysts. Initial cysts first excysted and the resulting polyps then strobilated. A second strobilation was not generally observed. The developmental implications of these activities are discussed.     

A reported early-man site adjacent to southern Alaska's continental shelf: A geologic solution to an archeologic enigma

An extensive ancient archeologic site containing lithic artifacts and associated with mammoth remains was reported at Chinitna Bay, southern Alaska in 1943. The presence of such a site adjacent to the continental shelf at the base of the rugged Aleutian Range suggested that humans may have inhabited the inner shelf environment during the late Pleistocene at times of lowered sea level. Because of the site's potential significance, an interdisciplinary research team relocated and reinvestigated the area in 1978, but failed to find evidence of prehistoric human habitation. Geologic studies and radiocarbon dating indicate that the strata reported at the site are intertidal in origin, very late Holocene in age, and have undergone significant tectonic movement in the recent past. These observations indicate that the previously published observations of the Chinitna Bay site are probably invalid.     

Evaluation of Weather Catastrophe Data for Use in Climate Change Investigations

A 1950–1994 data set of major weather losses developed by the property insurance industry was examined to assess its potential utility in climate change research and use in assessing the relevance of recent extreme losses in the United States. A process for adjusting these historical storm losses to ever-changing factors including dollar values, amount of insurance coverage per area, and the sensitivity of society to damaging storms was developed by the industry. Analysis of the temporal frequency and losses of these adjusted weather catastrophes revealed differences according to the amount of loss. Temporal changes since 1975 in the catastrophes causing $35 to $100 million in loss were strongly related to changes in U.S. population, whereas catastrophes that created insured losses greater than $100 million appear related to both shifting weather conditions and to regional population changes. This evaluation revealed that the industry's catastrophe adjustment technique did not adequately allow for changes in various demographic and social factors affecting damage; however, results suggest use of population values for normalizing the adjusted catastrophe database to allow meaningful studies of their temporal variability.     

The Cartesian method for solving partial differential equations in spherical geometry

Cartesian coordinates are used to solve the nonlinear shallow-water equations on the sphere. The two-dimensional equations, in spherical coordinates, are first embedded in a three-dimensional system in a manner that preserves solutions of the two-dimensional system. That is, solutions of the three-dimensional system, with appropriate initial conditions, also solve the two-dimensional system on the surface of the sphere. The higher dimensional system is then transformed to Cartesian coordinates. Computations are limited to the surface of the sphere by projecting the equations, gradients, and solution onto the surface. The projected gradients are approximated by a weighted sum of function values on a neighboring stencil. The weights are determined by collocation using the spherical harmonics in trivariate polynomial form. That is, the weights are computed from the requirement that the projected gradients are near exact for a small set of spherical harmonics. The method is applicable to any distribution of points and two test cases are implemented on an icosahedral geodesic grid. The method is both vectorizable and parallelizable.     

Mean Profiles of Moisture Fluxes in Snow-Filled Boundary Layers

Profiles of moisture fluxes have been examined for convective boundary layers containing clouds and snow, using data derived from aircraft measurements taken on four dates during the 1983/1984 University of Chicago lake-effect snow project. Flux profiles were derived from vertical stacks of aircraft cross-wind flight legs taken at various heights over Lake Michigan near the downwind shore. It was found that, if ice processes are taken into account, profiles of potential temperature and water content were very similar to those presented in past studies of convective boundary layers strongly heated from below. Profiles of total water content and equivalent potential temperature adjusted for ice were nearly invariant with height, except very near the top of the boundary layer, suggesting that internal boundary-layer mixing processes were rapid relative to the rates at which heat and vapour were transported into the boundary layer through entrainment and surface fluxes. Ice was found to play a significant, measurable role in boundary-layer moisture fluxes. It was estimated that 40 to 57% of the upward vapour flux was returned to the surface in the form of snow, converting about 45 to 64% of the surface latent heat flux into sensible heat in the snow-producing process. Assuming advective fluxes are relatively small (thought to be appropriate after the first few tens of km over the lake as suggested by past studies), the boundary layer was found to warm at a rate faster than could be explained by surface heat fluxes and latent heat releases alone, the remainder of the heating presumably coming from radiational processes and entrainment. Discussions of moisture phase change processes throughout the boundary layer and estimates of errors of these flux measurements are presented.