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排序方式： 共有331条查询结果，搜索用时 15 毫秒
271.
Jeroen Ingels Richard B. Aronson Craig R. Smith Amy Baco Holly M. Bik James A. Blake Angelika Brandt Mattias Cape David Demaster Emily Dolan Eugene Domack Spencer Fire Heidi Geisz Michael Gigliotti Huw Griffiths Kenneth M. Halanych Charlotte Havermans Falk Huettmann Scott Ishman Sven A. Kranz Amy Leventer Andrew R. Mahon James McClintock Michael L. McCormick B. Greg Mitchell Alison E. Murray Lloyd Peck Alex Rogers Barbara Shoplock Kathryn E. Smith Brittan Steffel Michael R. Stukel Andrew K. Sweetman Michelle Taylor Andrew R. Thurber Martin Truffer Anton van de Putte Ann Vanreusel Maria Angelica Zamora‐Duran 《Wiley Interdisciplinary Reviews: Climate Change》2021,12(1)
The calving of A‐68, the 5,800‐km2, 1‐trillion‐ton iceberg shed from the Larsen C Ice Shelf in July 2017, is one of over 10 significant ice‐shelf loss events in the past few decades resulting from rapid warming around the Antarctic Peninsula. The rapid thinning, retreat, and collapse of ice shelves along the Antarctic Peninsula are harbingers of warming effects around the entire continent. Ice shelves cover more than 1.5 million km2 and fringe 75% of Antarctica's coastline, delineating the primary connections between the Antarctic continent, the continental ice, and the Southern Ocean. Changes in Antarctic ice shelves bring dramatic and large‐scale modifications to Southern Ocean ecosystems and continental ice movements, with global‐scale implications. The thinning and rate of future ice‐shelf demise is notoriously unpredictable, but models suggest increased shelf‐melt and calving will become more common. To date, little is known about sub‐ice‐shelf ecosystems, and our understanding of ecosystem change following collapse and calving is predominantly based on responsive science once collapses have occurred. In this review, we outline what is known about (a) ice‐shelf melt, volume loss, retreat, and calving, (b) ice‐shelf‐associated ecosystems through sub‐ice, sediment‐core, and pre‐collapse and post‐collapse studies, and (c) ecological responses in pelagic, sympagic, and benthic ecosystems. We then discuss major knowledge gaps and how science might address these gaps. This article is categorized under:
- Climate, Ecology, and Conservation > Modeling Species and Community Interactions
272.
Ingo Leya Jean‐Christophe David Thomas Faestermann Michaela Froehlich Niko Kivel Dominik Koll Gunther Korschinek Sarah McIntyre Silke Merchel Stefan Pavetich Georg Rugel Dorothea Schumann Thomas Smith Anton Wallner 《Meteoritics & planetary science》2020,55(4):818-831
We measured specific activities of the long‐lived cosmogenic radionuclides 60Fe in 28 iron meteorites and 53Mn in 41 iron meteorites. Accelerator mass spectrometry was applied at the 14 MV Heavy Ion Accelerator Facility at ANU Canberra for all samples except for two which were measured at the Maier‐Leibnitz Laboratory, Munich. For the large iron meteorite Twannberg (IIG), we measured six samples for 53Mn. This work doubles the number of existing individual 60Fe data and quadruples the number of iron meteorites studied for 60Fe. We also significantly extended the entire 53Mn database for iron meteorites. The 53Mn data for the iron meteorite Twannberg vary by more than a factor of 30, indicating a significant shielding dependency. In addition, we performed new model calculations for the production of 60Fe and 53Mn in iron meteorites. While the new model is based on the same particle spectra as the earlier model, we no longer use experimental cross sections but instead use cross sections that were calculated using the latest version of the nuclear model code INCL. The new model predictions differ substantially from results obtained with the previous model. Predictions for the 60Fe activity concentrations are about a factor of 2 higher, for 53Mn, they are ~30% lower, compared to the earlier model, which gives now a better agreement with the experimental data. 相似文献
273.
Robert Pincus Anton Beljaars Stefan A. Buehler Gottfried Kirchengast Florian Ladstaedter Jeffrey S. Whitaker 《Surveys in Geophysics》2017,38(6):1399-1423
This paper addresses the representation of lower tropospheric water vapor in the meteorological analyses—fully detailed estimates of atmospheric state—providing the wide temporal and spatial coverage used in many process studies. Analyses are produced in a cycle combining short forecasts from initial conditions with data assimilation that optimally estimates the state of the atmosphere from the previous forecasts and new observations, providing initial conditions for the next set of forecasts. Estimates of water vapor are among the less certain aspects of the state because the quantity poses special challenges for data assimilation while being particularly sensitive to the details of model parameterizations. Over remote tropical oceans observations of water vapor come from two sources: passive observations at microwave or infrared wavelengths that provide relatively strong constraints over large areas on column-integrated moisture but relatively coarse vertical resolution, and occultations of Global Positioning System provide much higher accuracy and vertical resolution but are relatively spatially coarse. Over low-latitude oceans, experiences with two systems suggest that current analyses reproduce much of the large-scale variability in integrated water vapor but have systematic errors in the representation of the boundary layer with compensating errors in the free troposphere; these errors introduce errors of order 10% in radiative heating rates through the free troposphere. New observations, such as might be obtained by future observing systems, improve the estimates of water vapor but this improvement is lost relatively quickly, suggesting that exploiting better observations will require targeted improvements to global forecast models. 相似文献
274.
275.
Eberhard Gischler J. Harold Hudson Marc Humblet Juan C. Braga Anton Eisenhauer Anja Isaack Flavio S. Anselmetti Gilbert F. Camoin 《Sedimentology》2016,63(6):1522-1549
The universally known subsidence theory of Darwin, based on Bora Bora as a model, was developed without information from the subsurface. To evaluate the influence of environmental factors on reef development, two traverses with three cores, each on the barrier and the fringing reefs of Bora Bora, were drilled and 34 uranium‐series dates obtained and subsequently analysed. Sea‐level rise and, to a lesser degree, subsidence were crucial for Holocene reef development in that they have created accommodation space and controlled reef architecture. Antecedent topography played a role as well, because the Holocene barrier reef is located on a Pleistocene barrier reef forming a topographic high. The pedestal of the fringing reef was Pleistocene soil and basalt. Barrier and fringing reefs developed contemporaneously during the Holocene. The occurrence of five coralgal assemblages indicates an upcore increase in wave energy. Age–depth plots suggest that barrier and fringing reefs have prograded during the Holocene. The Holocene fringing reef is up to 20 m thick and comprises coralgal and microbial reef sections and abundant unconsolidated sediment. Fringing reef growth started 8780 ± 50 yr bp ; accretion rates average 5·65 m kyr?1. The barrier reef consists of >30 m thick Holocene coralgal and microbial successions. Holocene barrier‐reef growth began 10 030 ± 50 yr bp and accretion rates average 6·15 m kyr?1. The underlying Pleistocene reef formed 116 900 ± 1100 yr bp , i.e. during marine isotope stage 5e. Based on Pleistocene age, depth and coralgal palaeobathymetry, the subsidence rate of Bora Bora was estimated to be 0·05 to 0·14 m kyr?1. In addition to subsidence, reef development on shorter timescales like in the late Pleistocene and Holocene has been driven by glacioeustatic sea‐level changes causing alternations of periods of flooding and subaerial exposure. Comparisons with other oceanic barrier‐reef systems in Tahiti and Mayotte exhibit more differences than similarities. 相似文献
276.
Irina V. Kirillova Johannes van der Plicht Stanislav V. Gubin Oksana G. Zanina Olga F. Chernova Elena G. Lapteva Svetlana S. Trofimova Eugeny V. Zinovyev Anton A. Zharov Elena O. Fadeeva Thijs Van Kolfschoten Fedor K. Shidlovskiy Alexey A. Kotov 《Boreas: An International Journal of Quaternary Research》2016,45(3):455-469
An accumulation of mammoth hair, discovered in the Bol'shaya Chukochya River valley (northeast Yakutia, Russia), was found to contain remains of terrestrial and aquatic organisms, including plants, insects, crustaceans, birds and mammals. Radiocarbon dating indicated that this post‐mortem taphocoenosis represented multiple time periods. The mammoth hair was dated to older than 45 ka BP, the plants were dated to 12 750±50 a BP (which corresponds to a shift in the environmental conditions and landscapes during the formation of thermokarst in northeastern Russia) and the bird feathers were dated to 4115±40 a BP. A scenario of the formation of this fossil assemblage is proposed, covering the MIS 3‐1 time range. The hair also yielded various Arctic branchiopod crustaceans, which inhabit shallow temporary water bodies and therefore are important for reconstruction of palaeoenvironments. The cladoceran subgenus Daphnia (Ctenodaphnia), currently absent from the Asian part of Beringia, is reported from this region for the first time. The study demonstrates that the discovered permafrost‐preserved hair is a unique repository of Ice Age organisms. 相似文献
277.
278.
The best strategy to cope with natural hazards is the integral risk management, which involves all participants, decides on the basis of risks and also accepts a residual risk. Therefore, a substantial risk dialogue is essential not only to encourage self-responsibility. Even if throughout the Alpine perimeter this is accepted by the administration and the experts, the difficulties lie in the detail on the way to a full implementation of the effective risk management into practice. Therefore, a series of expert hearings and workshops was carried out in Bavaria to highlight the status of risk dialogue and point out the need for further development. In the beginning, an expert hearing dealt with the status of torrential risk management and worked out recommendations, focusing on the phases of reconstruction, preparation and prevention. On this basis, a practitioner workshop developed solution concepts for two case studies regarding all elements of the integral risk management. One of these was further regarded in a final workshop together with the municipality to encourage risk awareness, risk dialogue and to estimate the benefit of the measures. The activities and the results are described and summarized in the following article. 相似文献
279.
While hotspots of alcohol-related incidents have been associated with alcohol outlet density, few studies have considered other environmental factors. We aimed to characterise the environment of hotspots outside of outlet density areas in Amsterdam. Using geographical information systems, we identified hotspots of alcohol-related health incidents outside of outlet density areas based on the registry of alcohol related ambulance attendances. While quantitative data and methods were used to analyse victim profiles (including age, sex and home address) and temporal profiles (time of incident), we combined quantitative and qualitative information to develop environmental profiles of these hotspots. We identified 11 hotspots with 242 incidents outside outlet density areas. Results indicate substantial differences between incidents in these hotspots and incidents in high outlet density areas. Victims in these hotspots are older, more often male and live closer to the incident location compared to victims in high outlet density hotspots. Incidents are less likely to take place during the night and at weekends. In-depth analysis of four hotspots showed different combinations of contributing environmental factors, including (a) public parks bordering deprived neighbourhoods, (b) dance event facilities close to a traffic black spot, and (c) residential services for disadvantaged groups near ‘hang-outs’. The study shows that hotspots of alcohol-related incidents can arise outside outlet density areas at locations where several other environmental factors cluster, particularly in more deprived areas. Such hotspots can be addressed in urban planning and urban design. 相似文献
280.