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"Perry, J. E."
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Wetlands In a Changing Climate: Science, Policy and Management
Part 1 of this review synthesizes recent research on status and climate vulnerability of freshwater and saltwater wetlands, and their contribution to addressing climate change (carbon cycle, adaptation, resilience). Peatlands and vegetated coastal wetlands are among the most carbon rich sinks on the planet sequestering approximately as much carbon as do global forest ecosystems. Estimates of the consequences of rising temperature on current wetland carbon storage and future carbon sequestration potential are summarized. We also demonstrate the need to prevent drying of wetlands and thawing of permafrost by disturbances and rising temperatures to protect wetland carbon stores and climate adaptation/resiliency ecosystem services. Preventing further wetland loss is found to be important in limiting future emissions to meet climate goals, but is seldom considered. In Part 2, the paper explores the policy and management realm from international to national, subnational and local levels to identify strategies and policies reflecting an integrated understanding of both wetland and climate change science. Specific recommendations are made to capture synergies between wetlands and carbon cycle management, adaptation and resiliency to further enable researchers, policy makers and practitioners to protect wetland carbon and climate adaptation/resiliency ecosystem services.
Journal Article
Rapid and Extensive Surface Changes Near Titan's Equator: Evidence of April Showers
Although there is evidence that liquids have flowed on the surface at Titan's equator in the past, to date, liquids have only been confirmed on the surface at polar latitudes, and the vast expanses of dunes that dominate Titan's equatorial regions require a predominantly arid climate. We report the detection by Cassini's Imaging Science Subsystem of a large low-latitude cloud system early in Titan's northern spring and extensive surface changes (spanning more than 500,000 square kilometers) in the wake of this storm. The changes are most consistent with widespread methane rainfall reaching the surface, which suggests that the dry channels observed at Titan's low latitudes are carved by seasonal precipitation.
Journal Article
The Second Warning to Humanity – Providing a Context for Wetland Management and Policy
The Second Warning to Humanity provides a clarion call for wetland researchers and practitioners given the loss and degradation of wetlands, the declining availability of fresh water, and the likely consequences of climate change. A coordinated response and approach to policies has the potential to prevent further degradation and support resilient wetlands that can provide a range of ecosystem services, including buffering wetlands from climate impacts, and avoiding major climate amplification from temperature-induced release of additional carbon dioxide and methane while addressing the causes and consequences of global climate change. The Warning to Humanity also provides an opportunity for organisations such as the Society of Wetland Scientists to raise the profile of wetlands and to initiate a discussion on how to respond and change direction from the destructive development trajectory that led to wetland loss and degradation. It also provides a signal for a reappraisal of the effectiveness of the implementation of the Ramsar Convention on Wetlands as an international mechanism for ensuring the sustainability of wetlands.
Journal Article
Cassini imaging of Titan's high-latitude lakes, clouds, and south-polar surface changes
Cassini's Imaging Science Subsystem (ISS) has been observing Titan since April 2004, compiling a nearly global surface map and monitoring the surface and atmosphere for activity. Early images of the south‐polar region revealed numerous dark surface features and contemporaneous convective cloud systems, suggesting the presence of hydrocarbon lakes similar to those later detected at Titan's North Pole. Intriguingly, repeated south‐polar imaging by ISS revealed differences consistent with ponding of hydrocarbon liquids on the surface due to precipitation from a large storm. More recent ISS images of high northern latitudes illustrate the full extents (>500,000 km2) of hydrocarbon seas, sections of which have been observed by Cassini's RADAR. These observations demonstrate dynamic processes at work on Titan and that the poles harbor liquid‐hydrocarbon reservoirs, the extents of which differ from pole to pole and which may be coupled to seasonally varying circulation.
Journal Article
Seasonal changes in Titan's meteorology
The Cassini Imaging Science Subsystem has observed Titan for ∼1/4 Titan year, and we report here the first evidence of seasonal shifts in preferred locations of tropospheric methane clouds. South‐polar convective cloud activity, common in late southern summer, has become rare. North‐polar and northern mid‐latitude clouds appeared during the approach to the northern spring equinox in August 2009. Recent observations have shown extensive cloud systems at low latitudes. In contrast, southern mid‐latitude and subtropical clouds have appeared sporadically throughout the mission, exhibiting little seasonality to date. These differences in behavior suggest that Titan's clouds, and thus its general circulation, are influenced by both the rapid temperature response of a low‐thermal‐inertia surface and the much longer radiative timescale of Titan's cold thick troposphere. North‐polar clouds are often seen near lakes and seas, suggesting that local increases in methane concentration and/or lifting generated by surface roughness gradients may promote cloud formation.
Journal Article
Io Volcanism Seen by New Horizons: A Major Eruption of the Tvashtar Volcano
Jupiter's moon lo is known to host active volcanoes. In February and March 2007, the New Horizons spacecraft obtained a global snapshot of lo's volcanism. A 350-kilometer-high volcanic plume was seen to emanate from the Tvashtar volcano (62°N, 122°W), and its motion was observed. The plume's morphology and dynamics support nonballistic models of large lo plumes and also suggest that most visible plume particles condensed within the plume rather than being ejected from the source. In images taken in Jupiter eclipse, nonthermal visible-wavelength emission was seen from individual volcanoes near lo's sub-Jupiter and anti-Jupiter points. Near-infrared emission from the brightest volcanoes indicates minimum magma temperatures in the 1150- to 1335-kelvin range, consistent with basaltic composition.
Journal Article
A Perspective on Solid-State Additive Manufacturing of Aluminum Matrix Composites Using MELD
MELD, previously known as additive friction stir, is an emerging solid-state process that enables additive manufacturing of a broad range of metals and metal matrix composites. Here, we discuss its potential for fabricating aluminum matrix composites by showing examples of Al-SiC, Al 6061-Mo, and Al 6061-W composites. Thanks to its solid-state nature, MELD is uniquely suited for the use of high-strength aluminum alloys as matrix material, which would suffer from hot cracking problems in liquid-state processes. Using complementary characterization tools, we show that this process results in aluminum matrix composites with no observed porosity and homogeneous particle distribution. These properties stem from the extensive material flow and mixing during the deposition process. In addition to the high quality of produced composites, its ease of use, versatility of feed materials, and scalability all make MELD an attractive tool for additive manufacturing of aluminum matrix composites. We also discuss the limitations of MELD for composite fabrication, with issues related to maximum reinforcement loading, tool wear, and in-plane resolution. Finally, we compare the benefits and limitations of MELD with other composite fabrication processes such as powder bed fusion, friction stir processing, stir casting, and powder processing.
Journal Article
The Paraguay-Paraná Hidrovía: Protecting the Pantanal with Lessons from the Past
The Pantanal, an immense floodplain in the upstream basin of the Paraguay River, is a key hydrologic resource in South America. Gottgens et al assess the environmental impact of several small-scale actions in the area, such as extensive dredging and channel straightening.
Journal Article
Using a Floristic Quality Assessment Technique to Evaluate Plant Community Integrity of Forested Wetlands in Southeastern Virginia
Given the continuing degradation of freshwater wetland ecosystems throughout the Southeast, there has been significant interest in developing methods and indices to evaluate and monitor wetland biological integrity. The purpose of this study was to adapt and test the ability of a vegetation-based assessment technique known as Floristic Quality Assessment to detect the level of human impact in hardwood flat wetlands of Southeastern Virginia. We measured plant species diversity and composition within each vertical stratum [herbaceous, woody understory (shrub and sapling), and canopy] of 11 wetlands. We calculated a Floristic Quality Index (FQI) for each layer, and tested for relationship to land use disturbance patterns within defined site buffer and watershed areas. We found floristic quality of the herbaceous layer and the sapling portion of the woody understory layer to be negatively correlated with level of land use disturbance at both buffer and watershed scales, suggesting that FQI scores within these strata reflect current anthropogenic stress. While FQI of the canopy layer and the shrub portion of the woody understory layer were not reliable indicators of current land use disturbance, we found that a comparison of sapling and canopy layer FQIs gave insights into historic vs. recent floristic integrity of sites. Overall, our findings support the use of floristic quality assessments in evaluating wetland biological integrity when sampling and index calculation methodology are carefully adapted to local flora and community types.
Journal Article