There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Quantification of global forest change has been lacking despite the recognized importance of forest ecosystem services. In this study, Earth observation satellite data were used to map global forest loss (2.3 million square kilometers) and gain (0.8 million square kilometers) from 2000 to 2012 at a spatial resolution of 30 meters. The tropics were the only climate domain to exhibit a trend, with forest loss increasing by 2101 square kilometers per year. Brazil's well-documented reduction in deforestation was offset by increasing forest loss in Indonesia, Malaysia, Paraguay, Bolivia, Zambia, Angola, and elsewhere. Intensive forestry practiced within subtropical forests resulted in the highest rates of forest change globally. Boreal forest loss due largely to fire and forestry was second to that in the tropics in absolute and proportional terms. These results depict a globally consistent and locally relevant record of forest change.

High-Resolution Global Maps of 21st-Century Forest Cover Change

Google Earth Engine: Planetary-scale geospatial analysis for everyone

Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

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Climate Change 2007: The Physical Science Basis.

Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristic of the surface. By exploiting the phase of the coherent radar signal, interferometry has transformed radar remote sensing from a largely interpretive science to a quantitative tool, with applications in cartography, geodesy, land cover characterization, and natural hazards. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

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Synthetic aperture radar interferometry

This report summarizes the results of a nine-week summer project examining all Declassified Intelligence Satellite Photography (DISP) of Antarctica. It was discovered that the data were collected in three separate missions during 1962 and 1963. The first two missions covered only the coastal areas, while the third mission covered the entire continent. Many of the 1782 frames collected were cloudy. This is especially true of West Antarctica. An optimal set of photographs covering the entire Antarctic coastline is identified along with some examples that show changes in the coastline which have occurred since the early 1960s.

https://ntrs.nasa.gov/api/citations/19990009049/downloads/19990009049.pdf

Declassified Intelligence Satellite Photography (DISP) Coverage of Antarctica

Correction to: Force, mass, and energy budgets of the Crary Ice Rise complex, Antarctica

Glaciological applications of a satellite laser altimeter system with a range precision of approximately 10 cm and a footprint diameter of 70 m are discussed. Available data on ice-sheet dynamics are reviewed, and the measurement errors associated with the laser altimeter are examined. It is shown that information collected with the system could make it possible to detect changes in average elevation (i.e., in average ice thickness) of less than 15 cm for areas of hundreds of sq km to a few thousand sq km. Other possible applications of the system are briefly considered, including the mapping of the positions of ice-sheet margins, the mapping of the junction between a grounded ice sheet and a floating ice shelf, and the estimation of iceberg calving rates.

Ice-sheet dynamics by satellite laser altimetry

Ice thickness measurements have been carried out at the mouths of ice streams D and E, West Antarctica using a surface-based impulse radar. These studies have been undertaken as a part of the continuing effort to understand the state of the West Antarctic Ice Sheet and its response to climate change. Thickness measurements will be used in the mass balance calculation currently in progress and to better understand features in the surface topography seen at low angle sun illumination in the satellite imagery. Results show that the discharge areas of ice streams D and E are thickening by approximately one meter per year, and thus that these ice streams are likely loosing mass. Aperiodic wavelike features in the surface topography are described which pose interesting questions about migration of the grounding line and ice stream dynamics.

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Radar studies at the mouths of Ice Streams D and E, Antarctica

Distribution of drumlins on the Ontario Lowlands and the northern Appalachian Plateau of New York State are utilized in a glaciological model that estimates thicknesses of the Late Wisconsin Ice Sheet along five glacial flowlines over the central section of the Finger Lakes Dynamics of the model are based upon a force balance approach that incorporates variable width of a flowband, bedslope, radius of curvature, and center of outflow location Drumlin axes along five hydrostatic isograms were projected northward Points of axes convergence define the center of outflow in the eastern Ontario Basin Flowlines along the axial trace of the major Seneca and Cayuga Troughs and bordering interfluves were constructed southward to the Valley Heads Moraine System Calculation of flowline geometry for any assumed basal shear stress requires neither information on ice temperature nor the flow law of ice Ice thicknesses for each flow line were calculated for τ b values of 5, 10, and 15 bar Ice thicknesses at 1 bar range from a minimum of 1,932 m for the Seneca Trough flowline to a maximum of 2,093 m at the Keuka-Seneca interfluve flowline Raising or lowering τ b by 5 bar results in maximum thickness differences of +21% and -26%, respectively Simulating ice recession, a series of ice-marginal, terminal positions were plotted for a basal shear stress of 1 bar These predicted terminal positions agree well with locations of mapped moraine deposits These probable values of basal shear stress support the presence of glacial flow representative of internal deformation rather than basal sliding Although recent interpretations of the formation of the Finger Lakes focus on ice streams facilitated by large volumes of subglacial meltwater, our evidence discounts the presence of ice streams and supports the existence of outlet glaciers in the troughs of the Finger Lakes

Robert Bindschadler

Papers

Declassified Intelligence Satellite Photography (DISP) Coverage of Antarctica

Correction to: Force, mass, and energy budgets of the Crary Ice Rise complex, Antarctica

Ice-sheet dynamics by satellite laser altimetry

Radar studies at the mouths of Ice Streams D and E, Antarctica

Reconstruction and dynamics of the Late Wisconsin Ontario ice dome in the Finger Lakes region, New York