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

It happened during the long dark, polar night just over a year ago. It wasn't noticed until months later. Its climatic significance isn't clear yet, but it provides new insight into the process by which the Antarctic ice sheet periodically launches massive icebergs from around its perimeter and heightens concern that this area of Earth's largest frozen continent is changing.

“It” is the sudden formation of a large rift nearly three-fourths of the distance across the Pine Island Glacier (75°S, 102°W), a major outlet glacier of the West Antarctic ice sheet. The long rift was observed independently by researchers reviewing images collected in two separate mappings of Antarctica with two different sensors. The initial analysis of this dramatic event, including a prognosis of the rift's future growth and impending iceberg formation, incorporates recently collected data from no less than six sensors on five satellites operated by three space agencies.This study illustrates beautifully the new power of multisensor monitoring of the Earth from space.

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“Crack!” in the polar night

Previous research has documented a close association between high-resolution snow-pit profiles of hydrogen and oxygen stable-isotope ratios and multi-year Special Sensor Microwave/lmager (SSM/I) 37 GHz brightness temperature data in central Greenland Comparison of the SSM/I data to profiles obtained during the 1989-91 field seasons indicated that δ D and δ 18 O data from the near-surface snow at the Greenland summit are a reliable, high-resolution temperature proxy To test this new technique further, additional stable-isotope data were obtained from a 2 m snow pit constructed during late-June 1995 near the GISP2 site
 This new profile, supported by pit stratigraphy and chemistry data, confirms the utility of comparing stable-isotope records with SSM/I brightness temperatures The sub-annual variation of the δD record at the GISP2 site was determined using 15 match points, from approximately December 1991 through June 1995 and was guided in part by time-constrained hoar layers The close association of these temperature proxies supports the assertion that snow accumulation occurs frequently through the year and that the isotope record initially contains temperature information from many times of the year This is also independently confirmed by analysis of H 2 O 2 data The slope of the multi-year T vs δ correlation was evaluated along with the sub-annual variation in the amount, rate and timing of accumulation These new results are consistent with those from the previous study and they also demonstrate that the snow in this area initially contains temperature and chemical records with sub-annual resolution This encourages confident interpretation of the paleoclimatic signal variations in the GISP2 and GRIP deep cores

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Temperature history and accumulation timing for the snowpack at GISP2, central Greenland

Results are presented from two years of field data collected along the Siple Coast region of West Antarctica. Measurements were made in the vicinities of base camps which were established in the mouths of ice streams B and C and at the upstream edge of Crary Ice Rise. The annual rate of ice deformation in Ice Stream C is very small, generally less than 10−5 yr−1. Reoccupation of an 11 year old stake network permitted ice motion (6.1 m/yr) and grounding-line retreat (41 m/yr) to be measured. Visable strand cracks were used to map the grounding line. Its location differed from the grounding-line position determined from radar soundings by Scott Polar Research Institute (SPRI) by as much as 10 km but these differences are not believed to have dynamic significance. In contrast, Ice Stream B has no obvious grounding line near the position mapped by SPRI. The surface topography exhibits elongated ridges instead of the smoother surface of Ice Stream C. Regions of Ice Stream B with a lower surface elevation move faster than higher elevation regions, presumably because the lower-elevation ice is thinner and experiences less basal friction. Surface strain rates at Ice Stream B vary on a scale similar to the topographic relief but transverse differences in downstream velocity are only 1 to 2% of the 527 ± 50 m/yr ice motion. This value is slightly higher than predictions of the balance velocity which range between 450 and 480 m/yr. Near Crary Ice Rise, surface strain rates show increasing compression of the ice as it approaches the ice rise. The upstream boundary of Crary Ice Rise has been accurately determined based on a combination of surface measurements, aerial photography and radar-sounding data.

Robert Bindschadler

Papers

“Crack!” in the polar night

Temperature history and accumulation timing for the snowpack at GISP2, central Greenland

Ice Stream-Ice Shelf Interaction in West Antarctica

The Importance of Pressurized Subglacial Water in Separation and Sliding at the Glacier Bed (Abstract only)

Response of Antarctic Sea Ice to Uniform Atmospheric Temperature Increases