Geology topics

D.A. Stow

Publications and source records attributed to D.A. Stow.

4 recordsLinked to original sources

USGS2010

Interannual growth dynamics of vegetation in the Kuparuk River watershed, Alaska based on the Normalized Difference Vegetation Index

Interannual above-ground production patterns are characterized for three tundra ecosystems in the Kuparuk River watershed of Alaska using NOAA-AVHRR Normalized Difference Vegetation Index (NDVI) data. NDVI values integrated over each growing season (SINDVI) were used to represent seasonal production patterns between 1989 and 1996. Spatial differences in ecosystem production were expected to follow north-south climatic and soil gradients, while interannual differences in production were expected to vary with variations in seasonal precipitation and temperature. It was hypothesized that the increased vegetation growth in high latitudes between 1981 and 1991 previously reported would continue through the period of investigation for the study watershed. Zonal differences in vegetation production were confirmed but interannual variations did not covary with seasonal precipitation or temperature totals. A sharp reduction in the SINDVI in 1992 followed by a consistent increase up to 1996 led to a further hypothesis that the interannual variations in SINDVI were associated with variations in stratospheric optical depth. Using published stratospheric optical depth values derived from the SAGE and SAGE-II satellites, it is demonstrated that variations in these depths are likely the primary cause of SINDVI interannual variability.

International Journal of Remote Sensing↗

USGS2005

Evidence and implications of recent climate change in Northern Alaska and other Arctic regions

The Arctic climate is changing. Permafrost is warming, hydrological processes are changing and biological and social systems are also evolving in response to these changing conditions. Knowing how the structure and function of arctic terrestrial ecosystems are responding to recent and persistent climate change is paramount to understanding the future state of the Earth system and how humans will need to adapt. Our holistic review presents a broad array of evidence that illustrates convincingly; the Arctic is undergoing a system-wide response to an altered climatic state. New extreme and seasonal surface climatic conditions are being experienced, a range of biophysical states and processes influenced by the threshold and phase change of freezing point are being altered, hydrological and biogeochemical cycles are shifting, and more regularly human sub-systems are being affected. Importantly, the patterns, magnitude and mechanisms of change have sometimes been unpredictable or difficult to isolate due to compounding factors. In almost every discipline represented, we show how the biocomplexity of the Arctic system has highlighted and challenged a paucity of integrated scientific knowledge, the lack of sustained observational and experimental time series, and the technical and logistic constraints of researching the Arctic environment. This study supports ongoing efforts to strengthen the interdisciplinarity of arctic system science and improve the coupling of large scale experimental manipulation with sustained time series observations by incorporating and integrating novel technologies, remote sensing and modeling. ?? Springer 2005.

Climatic Change↗

USGS1985

Classification of deep-sea, fine-grained sediments

Most deep-sea sediments contain one or more biogenic components and one dominant nonbiogenic component, usually clay or silty clay. The authors present a descriptive classification scheme in which deep-sea, fine-grained sediments are placed within a three-components system of calcareous-biogenic, siliceous-biogenic, and nonbiogenic components. In a three-procedure the user assesses whether the dominant component is biogenic or nonbiogenic, whether the dominant biogenic component is siliceous or calcareous, and what the relative abundances of the biogenic components are within limits of 10, 25, and 50%. The terminology proposed is that commonly used by many sedimentologists, with some refinements and greater precision in the use of terms.

Journal of Sedimentary Petrology↗

USGS1984

Middle Cretaceous black shales at Site 530 in the southeastern Angola Basin

The middle Cretaceous black shale interval at Site 530 is 170 m thick and late Albian to Coniacian in age. The organic-carbon-rich sediments occur as 260 separate beds (average 4 cm, maximum 60 cm thick) and make up less than 10% of the recovered section. Associated lithologies are greenish, grayish, and reddish mudstones, marlstones, and rare limestones. Organic-carbon contents of the black shales average about 5% (maximum 16%), and of the interbedded sediments, less than 0.5%. Careful study of the sedimentary and biogenic structures and composition and review of paleoceanographic conditions in the Angola Basin indicate that a complex interplay of processes controlled black shale accumulation. Relatively low oxygen concentrations in sediment and bottom waters occurred periodically, and conditions locally may have been anoxic or near anoxic both in the basin and on the continental margin. Pelagic, hemipelagic, and turbiditic depositional processes all operated to varying degrees at different times.

Initial Reports of the D.S.D.P.↗