Recent studies suggest that Antarctica has the potential to contribute up to ~15 m of sea-level rise over the next few centuries. The evolution of the Antarctic Ice Sheet is driven by a combination ...of climate forcing and non-climatic feedbacks. In this review we focus on feedbacks between the Antarctic Ice Sheet and the solid Earth, and the role of these feedbacks in shaping the response of the ice sheet to past and future climate changes. The growth and decay of the Antarctic Ice Sheet reshapes the solid Earth via isostasy and erosion. In turn, the shape of the bed exerts a fundamental control on ice dynamics as well as the position of the grounding line-the location where ice starts to float. A complicating issue is the fact that Antarctica is situated on a region of the Earth that displays large spatial variations in rheological properties. These properties affect the timescale and strength of feedbacks between ice-sheet change and solid Earth deformation, and hence must be accounted for when considering the future evolution of the ice sheet.
Conservation biology and restoration ecology share a common interest in maintaining or enhancing populations, communities, and ecosystems. Much could be gained by more closely integrating the ...disciplines, but several challenges stand in the way. Goals differ, reflecting different origins and agendas. Because resources are insufficient to meet all needs, priorities must be established. Rapid environmental changes create uncertainties that compromise goals and priorities. To realize the benefits of integration, goals should be complementary, acknowledging the uncertainties that stem from temporal and spatial dynamics. Priorities should be established using clearly defined criteria, recognizing that not everything can be conserved or restored; some form of triage is inevitable. Because goals and priorities are societal concerns, conservation and restoration must include people as part of—rather than separate from—nature. A more meaningful and integrated approach will blur disciplinary boundaries, focus on outcomes rather than approaches, and use the tools of both disciplines.
As the rate and magnitude of climate change accelerate, understanding the consequences becomes increasingly important. Species distribution models (SDMs) based on current ecological niche constraints ...are used to project future species distributions. These models contain assumptions that add to the uncertainty in model projections stemming from the structure of the models, the algorithms used to translate niche associations into distributional probabilities, the quality and quantity of data, and mismatches between the scales of modeling and data. We illustrate the application of SDMs using two climate models and two distributional algorithms, together with information on distributional shifts in vegetation types, to project fine-scale future distributions of 60 California landbird species. Most species are projected to decrease in distribution by 2070. Changes in total species richness vary over the state, with large losses of species in some "hotspots" of vulnerability. Differences in distributional shifts among species will change species co-occurrences, creating spatial variation in similarities between current and future assemblages. We use these analyses to consider how assumptions can be addressed and uncertainties reduced. SDMs can provide a useful way to incorporate future conditions into conservation and management practices and decisions, but the uncertainties of model projections must be balanced with the risks of taking the wrong actions or the costs of inaction. Doing this will require that the sources and magnitudes of uncertainty are documented, and that conservationists and resource managers be willing to act despite the uncertainties. The alternative, of ignoring the future, is not an option.
The geothermal heat flux (GHF) is an important boundary condition for modeling the movement of the Antarctic ice sheet but is difficult to measure systematically at a continental scale. Earlier GHF ...maps suffer from low resolution and possibly biased assumptions in tectonism and crustal heat generation, resulting in significant uncertainty. We present a new GHF map for Antarctica constructed by empirically relating the upper mantle structure to known GHF in the continental United States. The new map, compared with previously seismologically determined one, has improved resolution and lower uncertainties. New features in this map include high GHF in the southern Transantarctic Mountains where warmer uppermost mantle is introduced by lithospheric removal and in the Thwaites Glacier region. Additionally, a modest GHF in the central West Antarctic Rift system near the Siple Coast and an absence of large‐scale regions with GHF greater than 90 mW/m2 are found.
Plain Language Summary
The flow of the heat from Earth's interior into the ice sheet of Antarctica, or geothermal heat flux, has been poorly constrained but is important for understanding the movement of the ice sheet. In this study, we present a new map of the geothermal heat flux estimated from the latest studies of the seismic structure of Antarctica. This is accomplished by directly relating seismic wave speeds with heat flux for the continental United States, a place where many local heat flux measurements have been collected. The new map contains features that have not been reported before. For example, we find that more heat is coming out from the base of the southern Transantarctic Mountains, which is perhaps related to the missing thick and cold lithosphere beneath that region. We also report that part of West Antarctica may have lower geothermal heat flux than previously reported. The new map will help model the movement of the Antarctic ice sheet and predict its future.
Key Points
A new geothermal heat flux map for the continental Antarctica is presented
Based on the latest seismic structure of Antarctica, the new map has improved resolution and reduced uncertainties
New features of the map include high GHF in the Thwaites Glacial region and southern Transantarctic Mountains
Landscape ecology and conservation share a common focus on places, but they differ in their perspectives about what is important about those places, and the integration of landscape ecology into ...conservation is far from complete. I consider four ways in which landscape ecology can contribute to conservation. First, protected areas that are established for conservation are not stand-alone isolates. They exist in the context of broader landscape mosaics, which may encourage or discourage movements of individuals into and out of an area. Second, the landscape surroundings of a preserve may contain threats to the biodiversity within the preserve, many of them consequences of human activities. In combination, these relationships with the surroundings may make the “effective area” of a preserve different from that shown on a map. Third, the scale of an administrative area or of management action may not coincide with the scales of populations, disturbances, or ecological processes, creating challenges to both landscape ecology and conservation. Finally, landscapes encompass people and their activities; sustainability of conservation requires consideration of the tradeoffs between human uses and the biodiversity values of a landscape. I illustrate these four themes with a case study of the management of prairie dogs (Cynomys ludovicianus) in the Great Plains of North America, where the tensions between conservation and human land uses are particularly high. Ecologists and conservationists consider prairie dogs as keystone species in these grassland ecosystems and primary targets for conservation, but many private landowners regard them as varmints that consume valuable livestock forage and degrade rangeland condition. Effective conservation of functioning grasslands must include prairie dogs, and this in turn requires that the issues be addressed in terms of the biological, social, and cultural features of entire landscapes. Important as they are, areas protected for conservation cannot by themselves stem the tide of global biodiversity loss. The perspective must be broadened to include the landscapes where people live and work, recognizing the dynamic nature of landscapes and the factors driving land-use change. Landscape ecologists must work together to overcome the cultural differences between their disciplines, and between academic science and conservation practice and management. It can, and must, be done.
We estimate the upper mantle temperature of the Antarctic Plate based on the thermoelastic properties of mantle minerals and S velocities using a new 3‐D shear velocity model, AN1‐S. Crustal ...temperatures and surface heat fluxes are then calculated from the upper mantle temperature assuming steady state thermal conduction. The temperature at the top of the asthenosphere beneath the oceanic region and West Antarctica is higher than the dry mantle solidus, indicating the presence of melt. From the temperature values, we generate depth maps of the lithosphere‐asthenosphere boundary and the Curie temperature isotherm. The maps show that East Antarctica has a thick lithosphere similar to that of other stable cratons, with the thickest lithosphere (~250 km) between Domes A and C. The thin crust and lithosphere beneath West Antarctica are similar to those of modern subduction‐related rift systems in East Asia. A cold region beneath the Antarctic Peninsula is similar in spatial extent to that of a flat‐subducted slab beneath the southern Andes, indicating a possible remnant of the Phoenix Plate, which was subducted prior to 10 Ma. The oceanic lithosphere generally thickens with increasing age, and the age‐thickness correlation depends on the spreading rate of the ridge that formed the lithosphere. Significant flattening of the age‐thickness curves is not observed for the mature oceanic lithosphere of the Antarctic Plate.
Key Points
High‐resolution crust/lithosphere temperature model covering the Antarctic Plate
A fossil slab of the Phoenix Plate is found beneath the Antarctic Peninsula
The age‐thickness relation of oceanic lithosphere depends on ridge spreading rate
Subduction zones are a key link between the surface water cycle and the solid Earth, as the incoming plate carries pore water and hydrous minerals into the subsurface. However, water fluxes from ...surface to subsurface reservoirs over geologic time are highly uncertain because the volume of water carried in hydrous minerals in the slab mantle is poorly constrained. Estimates of slab mantle hydration based on seismic tomography assume bulk serpentinization, representing an upper bound on water volume. We measure azimuthal seismic anisotropy near the Marianas Trench, use spatial variations in anisotropy to constrain the extent and geometry of bend‐related faulting, and place a lower bound on slab mantle water content for the case where serpentinization is confined within fault zones. The seismic observations can be explained by a minimum of ∼0.85 wt% water in the slab mantle, compared to the upper bound of ∼2 wt% obtained from tomography.
Plain Language Summary
The global water cycle extends into Earth's interior at subduction zones, where tectonic plates carrying water chemically bound in rocks and minerals descend into the mantle. The amount of water cycled into the mantle by subduction is not well known. Part of the water flux can be estimated by measuring seismic velocities in the subducting plate, since the water‐bearing minerals tend to have slower seismic velocities, but this is an upper bound because it assumes that the water‐bearing minerals are evenly distributed when in reality they are more likely to be localized within fault zones. We use seismic anisotropy, variations in wavespeed with propagation direction, to study the degree of faulting near the Marianas Trench and estimate a lower bound on the water flux from surface to subsurface assuming that water‐bearing minerals are only within faults.
Key Points
We measure spatial variations in upper mantle anisotropy that indicate bend‐faulting near the Marianas Trench
Hydration localized to bend‐faults places a lower bound on the amount of water carried in the subducting slab mantle
Synthetic seismograms compared to the observed anisotropy indicate a minimum of 0.85 wt% water in the slab mantle
Drugs have been associated with the development of delirium in the elderly. Successful treatment of delirium depends on identifying the reversible contributing factors, and drugs are the most common ...reversible cause of delirium. Anticholinergic medications, benzodiazepines, and narcotics in high doses are common causes of drug induced delirium. This article provides an approach for clinicians to prevent, recognise, and manage drug induced delirium. It also reviews the mechanisms for this condition, especially the neurotransmitter imbalances involving acetylcholine, dopamine, and gamma aminobutyric acid and discusses the age related changes that may contribute to altered pharmacological effects which have a role in delirium. Specific interventions for high risk elderly with the goal of preventing drug induced delirium are discussed.
Gravity waves impacting ice shelves illicit a suite of responses that can affect ice shelf integrity. Broadband seismometers deployed on the Ross Ice Shelf, complemented by a near‐icefront seafloor ...hydrophone, establish the association of strong icequake activity with ocean gravity wave amplitudes (AG) below 0.04 Hz. The Ross Ice Shelf‐front seismic vertical displacement amplitudes (ASV) are well correlated with AG, allowing estimating the frequency‐dependent transfer function from gravity wave amplitude to icefront vertical displacement amplitude (TGSV(f)). TGSV(f) is 0.6–0.7 at 0.001–0.01 Hz but decreases rapidly at higher frequencies. Seismicity of strong icequakes exhibits spatial and seasonal associations with different gravity wave frequency bands, with the strongest icequakes observed at the icefront primarily during the austral summer when sea ice is minimal and swell impacts are strongest.
Key Points
Rift and icefront icequakes were identified
Icefront icequakes are most frequent during the austral summer when swell forcing is greatest in the absence of sea ice
An empirical ocean‐to‐ice shelf displacement transfer function is obtained
1. Landscape ecology deals with the influence of spatial pattern on ecological processes. It considers the ecological consequences of where things are located in space, where they are relative to ...other things, and how these relationships and their consequences are contingent on the characteristics of the surrounding landscape mosaic at multiple scales in time and space. Traditionally, landscape ecologists have focused their attention on terrestrial ecosystems, and rivers and streams have been considered either as elements of landscape mosaics or as units that are linked to the terrestrial landscape by flows across boundaries or ecotones. Less often, the heterogeneity that exists within a river or stream has been viewed as a `riverscape' in its own right.
2. Landscape ecology can be unified about six central themes: (1) patches differ in quality (2) patch boundaries affect flows, (3) patch context matters, (4) connectivity is critical, (5) organisms are important, and (6) the importance of scale. Although riverine systems differ from terrestrial systems by virtue of the strong physical force of hydrology and the inherent connectivity provided by water flow, all of these themes apply equally to aquatic and terrestrial ecosystems, and to the linkages between the two.
3. Landscape ecology therefore has important insights to offer to the study of riverine ecosystems, but these systems may also provide excellent opportunities for developing and testing landscape ecological theory. The principles and approaches of landscape ecology should be extended to include freshwater systems; it is time to take the `land' out of landscape ecology.
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