Experiences and perspective in compiling long-term remote sensing data sets on landscapes and biospheric processes

Remote sensing has been employed to study the Earth's landscapes for more than a century. Over the last thirty years major changes in all aspects of the technology, as well as scientific understanding of the measurements, have revolutionized use of these data for terrestrial research. The emergence of biophysical interpretations of land remotely sensed data has created great interest in the potential of these data to study the dynamics of landscapes and biospheric processes as contributors to global change. However, the evolutionary history of land remote sensing, particularly in the Landsat era, has in many ways worked against this use of the data. Until recently, there was little appreciation of the need to compile long-term historical records of these observations. There are currently no formal scientific institutional systems dedicated to preserving and distributing the long-term record of Earth observations acquired by Landsat, AVHRR or other land observing systems. As the International Geosphere-Biosphere Program begins, this issue should be one of the first priorities of the participants.     

Climate change in southern Illinois, USA, based on the age and δC of organic matter in cave sediments

Matrix-supported diamicton and uniform to laminated, silty, fine-grained sediment deposited from about 42,500 to 27,600 cal yr B.P. under slackwater conditions nearly filled two caves in southwestern Illinois. At some point, most of the sediment was flushed from the caves and from about 22,700 to 4000 cal yr B.P., floods deposited a drape of sandy and silty sediment on remnant slackwater successions, cobbly alluvium, and bedrock (especially from 7700 to 4000 cal yr B.P.). Clay mineral analyses of the slackwater cave sediment reveal a provenance of chiefly Petersburg Silt, a smectite- and illite-rich proglacial lacustrine unit present in the overlying Illinois Episode glacial succession. Today, remnants of the ancient subterranean slackwater deposits nearly fill several secondary passages and, in at least two locations, cover a cobble-mantled strath terrace 1.3 to 1.5 m above active stream channels. Slumping and sinkhole formation appear to have been important mechanisms for deposition of the ancient subterranean deposits. Slumping of these surficial deposits and associated vegetation can occur along the flanks of sinkholes (in addition to sinkhole formation) and enter caves; however, the finer organics, some of them comminuted during transport into the caves, become part of the cave alluvium. This finer organic fraction is the modern analog of the humified organic matter disseminated in slackwater sediment dated in this investigation by radiocarbon methods. Twenty-four ¹⁴C ages on humified organic matter provide chronologic control. The δ¹³C values of the organic matter reflect the proportion of C₄-type to C₃-type vegetation growing in and around swallets and sinkholes at the time of redeposition. Drought-tolerant C₄-type vegetation was more prevalent relative to C₃-type vegetation from 42,500 to 31,200 cal yr B.P. compared to conditions from 28,800 cal yr B.P. to the present. The δ¹³C values are consistent with the results from other investigations of speleothems and organic matter from loessial paleosols.     

Spatial Patterns of Migration and Income Change in the Mountain West: The Dominance of Service‐Based,Amenity‐Rich Counties

One of the most recognizable and important changes occurring in the West is rapid population growth. This article intends to address questions associated with whether patterns of population growth and income migration are associated with “new” and “old” West economies. Rural restructuring in the U.S. has created a group of counties with service‐based economies. In the Mountain West, a number of counties with service‐based economies are located in areas with high levels of environmental or natural amenities, creating what has been termed the “New West.” Migration to the rural parts of the Mountain West, and the income transfers associated with migration, are increasingly concentrated within these New West counties. Rapid population growth, the changing characteristics of in‐migrants, and their spatial concentration in New West counties provide a basis for conflicts over what the rural West is becoming.     

The effects of seasonal variability and weather on microbial fecal pollution and enteric pathogens in a subtropical estuary

The Charlotte Harbor estuary in southwest Florida was sampled monthly for one year at twelve stations, in the lower reaches of the Myakka and Peace Rivers. The objectives of the study were to address the distribution and seasonal changes in microbial indicators and human pathogen levels in Charlotte Harbor shellfish and recreational waters, and to determine those factors that may be important in the transport and survival of pathogens. Monthly water samples and quarterly sediment samples were analyzed for fecal coliform bacteria, enterococci,Clostridium perfringens, and coliphage. Quarterly samples also were analyzed for the enteric human pathogens,Cryptosporidium spp.,Giardia spp., and enteroviruses. Fecal indicator organisms were generally concentrated in areas of low salinity and high densities of septic systems; however, pollution became widespread during wet weather in, the late fall and winter of 1997–1998, coincident with a strong El Nino event. Between, December 1997 and February 1998, enteroviruses were detected at 75% of the sampling stations; none were detected in other months. Enteric protozoa were detected infrequently and were not related to seasonal influences. Fecal indicators and enteroviruses were each significantly associated with rainfall, streamflow, and temperature. Regression models suggest that temperature and rainfall can predict the occurrence of enteroviruses in 93.7% of the cases. Based on findings in this watershed, factors such as variability in precipitation, streamflow, and temperature show promise in modeling and forecasting periods of poor coastal water quality.     

The global distribution of long-term total ozone variations during the period 1957–1975

Total ozone observations in the international network have been used as a basis for the analysis of the mean monthly ozone distribution over the globe for the period 1957–75. It has been found that during the period 1961–70 the total ozone amount increased in the Northern Hemisphere by about 12 percent and that this increase seems to be significant at all latitudes. Although the data were sparse for the Southern Hemisphere, there did not appear to be any significant ozone changes during the 10 year period. Relatively large geographic variations were found in the ozone trends and it is suggested that these variations are related to large scale changes in the atmospheric circular pattern.     

Stable isotope geochemistry of deep sea cherts

Seventy four samples of DSDP recovered cherts of Jurassic to Miocene age from varying locations, and 27 samples of on-land exposed cherts were analyzed for the isotopic composition of their oxygen and hydrogen. These studies were accompanied by mineralogical analyses and some isotopic analyses of the coexisting carbonates. δ¹⁸O of chert ranges between 27 and 39%. relative to SMOW, δ¹⁸O of porcellanite—between 30 and 42%.. The consistent enrichment of opal-CT in porcellanites in ¹⁸O with respect to coexisting microcrystalline quartz in chert is probably a reflection of a different temperature (depth) of diagenesis of the two phases.δ¹⁸O of deep sea cherts generally decrease with increasing age, indicating an overall cpoling of the ocean bottom during the last 150 m.y. A comparison of this trend with that recorded by benthonic foraminifera (Douglas and Savin, 1975) indicates the possibility of δ¹⁸O in deep sea cherts not being frozen in until several tens of millions of years after deposition. Cherts of any Age show a spread of δ¹⁸O values, increasing diagenesis being reflected in a lowering of δ¹⁸O. Drusy quartz has the lowest δ¹⁸O values.On-land exposed cherts are consistently depleted in ¹⁸O in comparison to their deep sea time equivalent cherts.Water extracted from deep sea cherts ranges between 0.5 and 1.4 wt %. δD of this water ranges between ?78 and ?95%. and is not a function of δ¹⁸O of the cherts (or the temperature of their formation).     

Shock-induced devolatilization of calcite

The amounts of CO₂ and CO evolved upon shock compression and decompression of calcite to 18 GPa (180 kbar) have been determined using a new gas phase shock recovery technique and gas source mass spectrometry. The data demonstrate that from ～0.03 to 0.3 mole percent of calcite is devolatilized at shock pressures significantly lower than those predicted (30 GPa) for the onset of volatilization by continuum thermodynamic theory and are in qualitative agreement with release adiabat data for calcite and aragonite. Carbon and oxygen isotope ratios in the shock-released CO₂ are the same as those in the unshocked (hydrothermal) calcite, demonstrating that the CO₂ comes from the calcite rather than other potential sources.