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111.
Miriam J. Doyle Susan J. Picquelle Kathryn L. Mier Michael C. Spillane Nicholas A. Bond 《Progress in Oceanography》2009,80(3-4):163-187
The present study investigates ecological patterns and relationships to environmental variables among a time-series of larval fish species abundance from late spring surveys (1981–2003) in the northwest Gulf of Alaska (GOA). Links between interannual variation in species abundance and the physical environment were explored using generalized additive modeling (GAM). Trends in larval abundance and connections with physical variables displayed patterns that indicate unique and complex responses among species to environmental forcing during the larval period. In particular, the observed patterns suggest that ontogenetic-specific responses, representing sub-intervals of early life, are important. In addition, a notable degree of synchrony in larval abundance trends, and similarity in links with physical variables, were observed among species with common early life history patterns. The deepwater spawners, northern lampfish, arrowtooth flounder, and Pacific halibut, were most abundant in the study area during the 1990s, in association with enhanced wind-driven onshore and alongshore transport. Years of high abundance for Pacific cod, walleye pollock, and northern rock sole were associated with cooler winters and enhanced alongshore winds during spring. High larval abundance for spring–summer spawning rockfish species and southern rock sole seemed to be favored by warmer spring temperatures later in the time-series. This apparent exposure–response coupling seems to be connected to both local-scale and basin-scale environmental signals, to varying degrees depending on specific early life history characteristics. Understanding such ecological connections contributes to the evaluation of vulnerability and resilience among GOA species’ early life history patterns to fluctuating climate and oceanographic conditions. This investigation also provides crucial information for the identification of “environmental indicators” that may have a broad-spectrum effect on multiple species early life history stages, as well as those that may be more species-specific in exerting control on early life history survival. Of particular interest was the emergence of the EP–NP (East Pacific–North Pacific) teleconnection index as the top-ranked variable in the GAM models exploring the connections between late spring larval abundance and the physical environment. The EP–NP index represents an important and often primary mode of spring–summer atmospheric variability in the northeast Pacific, with a strong expression in the GOA, and its connection with species in this study implies that it may be a climate mode of significant ecological importance. 相似文献
112.
Evidence for current-controlled morphology along the western slope of Hatton Bank (Rockall Plateau, NE Atlantic Ocean) 总被引:1,自引:0,他引:1
Miriam Sayago-Gil David Long Kenneth Hitchen Víctor Díaz-del-Río Luis Miguel Fernández-Salas Pablo Durán-Muñoz 《Geo-Marine Letters》2010,30(2):99-111
A multibeam bathymetric and high- (airgun and sparker) to very high-resolution (Topas) seismic study of the western slope
of Hatton Bank (NE Atlantic), located between 600 m and 2,000 m water depth, has revealed a highly variable range of current-controlled
morphological features. Two major seabed areas can be distinguished: (1) a non-depositional area corresponding to the top
of the bank and (2) a depositional area in which the Hatton Drift has developed. Both areas are characterised by distinct
morphologies associated either with rock outcrops and rocky ridges or with smooth surfaces, slides and bedforms controlled
mainly by bottom currents interacting with the topography of the bank. The water depth separating the morphological areas
probably coincides with the boundary of the Labrador Sea Water and the Lower Deep Water. Morphological features identified
in the study area include contourite channels (moats, furrows and scours), fields of sediment waves, edges of contourite deposits,
ponded deposits, scarps, gullies, ridges, depressions, slides and slide scars. These morphological features do not necessarily
reflect present-day conditions but may have been associated with past current events, consistent with earlier interpretations. 相似文献
113.
Celeste Benham Alison M. Cawood Geoffrey S. Cook Ange Darnell Peter C. Davison Miriam C. Goldstein Ayana Elizabeth Johnson Talina Konotchick Elisa M. Maldonado Alexis L. Pasulka Jennifer C. Prairie Serena M. Moseman Vera Tai Christina A. Tanner Tali Vardi Tara S. Whitty & Lisa A. Levin 《Marine Ecology》2008,29(2):319-320
114.
Testing the utility of structure‐from‐motion photogrammetry reconstructions using small unmanned aerial vehicles and ground photography to estimate the extent of upland soil erosion 总被引:1,自引:0,他引:1
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Miriam Glendell Gareth McShane Luke Farrow Mike R. James John Quinton Karen Anderson Martin Evans Pia Benaud Barry Rawlins David Morgan Lee Jones Matthew Kirkham Leon DeBell Timothy A. Quine Murray Lark Jane Rickson Richard E. Brazier 《地球表面变化过程与地形》2017,42(12):1860-1871
Quantifying the extent of soil erosion at a fine spatial resolution can be time consuming and costly; however, proximal remote sensing approaches to collect topographic data present an emerging alternative for quantifying soil volumes lost via erosion. Herein we compare terrestrial laser scanning (TLS), and both unmanned aerial vehicle (UAV) and ground photography (GP) structure‐from‐motion (SfM) derived topography. We compare the cost‐effectiveness and accuracy of both SfM techniques to TLS for erosion gully surveying in upland landscapes, treating TLS as a benchmark. Further, we quantify volumetric soil loss estimates from upland gullies using digital surface models derived by each technique and subtracted from an interpolated pre‐erosion surface. Soil loss estimates from UAV and GP SfM reconstructions were comparable to those from TLS, whereby the slopes of the relationship between all three techniques were not significantly different from 1:1 line. Only for the TLS to GP comparison was the intercept significantly different from zero, showing that GP is more capable of measuring the volumes of very small erosion features. In terms of cost‐effectiveness in data collection and processing time, both UAV and GP were comparable with the TLS on a per‐site basis (13.4 and 8.2 person‐hours versus 13.4 for TLS); however, GP was less suitable for surveying larger areas (127 person‐hours per ha?1 versus 4.5 for UAV and 3.9 for TLS). Annual repeat surveys using GP were capable of detecting mean vertical erosion change on peaty soils. These first published estimates of whole gully erosion rates (0.077 m a?1) suggest that combined erosion rates on gully floors and walls are around three times the value of previous estimates, which largely characterize wind and rainsplash erosion of gully walls. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
115.
Jos A. Lpez-Sez Antonio Blanco-Gonzlez Lourdes Lpez-Merino M. Blanca Ruiz-Zapata Miriam Dorado-Valio Sebastin Prez-Díaz Ana Valdeolmillos Francesc Burjachs 《Quaternary International》2009,200(1-2):90
Correlations between ecological and cultural changes occurred during a short period between the end of Subboreal and the beginning of Subatlantic in the Amblés Valley (Ávila, central Spain) are analyzed, taking into account palaeopalynological and archaeological data. Plant dynamics from pollen analyses, both from archaeological sites and peat bogs, have been interpreted in relation to human settlements and the transformation of economic practices. These provided a comprehensive hypothesis on human/climate interactions at the beginning of the 1st millennium cal BC. There was an ecological crisis in the region that lasted for a century (ca. 850–760 cal BC). This was especially sharp due to both the geographical constraints of the area and its previous agrarian history. This event implied a sudden and abrupt climatic change from xeric and warm conditions (Subboreal) to more humid and cooler ones (Subatlantic). Environmental stress derived from climatic crisis could be an important factor in the explanation of the historical process, whose main consequences were both the origin of the Iron Age peasant villages and the end of the ‘dehesa’ type landscape. 相似文献
116.
Miriam Pfeiffer Wolf-Christian Dullo Jens Zinke Dieter Garbe-Schönberg 《International Journal of Earth Sciences》2009,98(1):53-66
In order to assess the fidelity of coral Sr/Ca for quantitative reconstructions of sea surface temperature variations, we have generated three monthly Sr/Ca time series from Porites corals from the lagoon of Peros Banhos (71°E, 5°S, Chagos Archipelago). We find that all three coral Sr/Ca time series are well correlated with instrumental records of sea surface temperature (SST) and air temperature. However, the intrinsic variance of the single-core Sr/Ca time series differs from core to core, limiting their use for quantitative estimates of past temperature variations. Averaging the single-core data improves the correlation with instrumental temperature (r > 0.7) and allows accurate estimates of interannual temperature variations (~0.35°C or better). All Sr/Ca time series indicate a shift towards warmer temperatures in the mid-1970s, which coincides with the most recent regime shift in the Pacific Ocean. However, the magnitude of the warming inferred from coral Sr/Ca differs from core to core and ranges from 0.26 to 0.75°C. The composite Sr/Ca record from Peros Banhos clearly captures the major climatic signals in the Indo-Pacific Ocean, i.e. the El Niño–southern oscillation and the Pacific decadal oscillation. Moreover, composite Sr/Ca is highly correlated with tropical mean temperatures (r = 0.7), suggesting that coral Sr/Ca time series from the tropical Indian Ocean will contribute to multi-proxy reconstructions of tropical mean temperatures. 相似文献
117.
Jose Rosas-Elguera Bertha Aguilar Reyes Avto Goguitchaichvili Macario Rocha Margarita López Martínez Miriam M. Tostado-Plascencia Luis M. Alva Valdivia Cecilia Caballero Miranda 《Studia Geophysica et Geodaetica》2011,55(2):265-278
For long time the western-central Mexico has been affected by oblique subduction caused by Farallon plate beneath North America.
As result, smaller plates (e.g. Cocos Plate), several fault systems outlining crustal blocks (e.g. Michoacán block) and magmatic
arcs (e.g. Paleocene-Early Oligocene magmatism and the Trans-Mexican Volcanic Belt) were developed. Still, no paleomagnetic
data are available for Oligocene and Miocene. The principal aim of this study is to evaluate whether the tectonic rotations
and relative motions of these blocks occurred before the Miocene. Here, we report a detailed rock-magnetic and paleomagnetic
results from Tecalitlan area, located in the Michoacán block. Sixteen sites (about 150 oriented samples) were collected including
one radiometrically dated diabase dike (35.0 ± 1.8 Ma). Rock-magnetic experiments permitted identification of magnetic carriers
and assessment of the paleomagnetic stability. Continuous susceptibility measurements vs temperature in most cases yield reasonably
reversible curves with Curie points close to that of magnetite. Reliable paleomagnetic directions were obtained for 12 sites.
Inclination I and declination D of the mean paleomagnetic direction obtained in this study are I = 33.1°, D = 345.0°, and
Fisherian statistical parameters are k = 25, α95 = 8.9°. The corresponding mean paleomagnetic pole position is Plat = 75.7°, Plong = 166.6°, K = 31, A95 = 8.0°. The mean inclination is in reasonably good agreement with the expected value, as derived from reference poles for
the stable North America. Magnetic declination is not significantly different from that expected which is in disagreement
with a counterclockwise tectonic rotation of about 20° previously reported for the studied area. Based on paleomagnetic results
obtained in this study compiled with those currently available from the Michoacán Block, we propose a simple model suggesting
that sometime in Eocene epoch the convergence vector of the Farallon plate relative to North America plate was normal to the
trench before reaching an actual oblique convergence. 相似文献
118.
Application of groundwater sustainability indicators to the carbonate aquifer of the Sierra de Becerrero (Southern Spain) 总被引:3,自引:1,他引:2
L. J. Lambán S. Martos M. Rodríguez-Rodríguez J. C. Rubio 《Environmental Earth Sciences》2011,64(7):1835-1848
The objective of this study was to test the applicability of groundwater sustainability indicators defined by UNESCO, together
with the International Academy of Environmental Sciences (IAES), the International Association of Hydrogeology (IAH) Group
on Groundwater Indicators and the Geological Survey of Spain (IGME), to the aquifer scale. We selected four main indicators
based on their relevance in the field of groundwater sustainability and because they proved to be the most reliable, based
on the data collection and methodology utilized. These indicators were applied to a small—26 km2 of permeable outcrops—carbonate aquifer situated in the province of Seville (southern Spain), which has semi-arid climate
conditions (500 mm/year). The integral application of all these indicators in this particular groundwater body leads us to
conclude that, at present, the aquifer is undergoing intensive use. Therefore, the exploitation of its water resources is
surpassing the threshold of sustainability when both the quantity and the quality of the groundwater are taken into consideration.
The continued increase in exploitation generates a descending trend in the evolution of the piezometric levels, a consequence
of adaptation to the new hydrodynamic situation, and also results in exhaustion of the springs that drain the aquifer in undisturbed
conditions. At the same time, there is a trend of increasing salinity in the groundwater and a risk of contamination by nitrate
which, according to the EU Water Framework Directive and the Groundwater Daughter Directive (EU Official Journal of the European
Communities L327, 2000; EU Official Journal of the European Communities L372/19, 2006), should be controlled and reduced. In the future, application of the methodology described here may prove useful for the
evaluation of similar systems, either in southern Spain or in other countries with semi-arid climates. 相似文献
119.
Miriam Peña Manuel Peimbert Silvia Torres-Peimbert Maria Teresa Ruiz Jose Maza 《Astrophysics and Space Science》1996,238(1):55-58
The recent evolution of the central star of the planetary nebula LMC-N66 is presented. Before 1987, it showed a weak continuum with aT
eff120 000 K andL
bol25 000L
and in a few years it developed strong WR features (P Cygni line profiles in N v at 124.0 nm and C IV at 155.0 nm, wide Heii emission, etc.) typical of a WN 4.5. Additionally the stellar continuum increased by a large factor and the absolute visual magnitude of the star changed from + 1.24 in 1987 to–2.57 in January, 1995. The WR features and enhanced continuum, evidencing a powerful mass-loss event remained with small variations for more than 5 years. Recent ultraviolet and optical data shows that the mass-loss seems to have diminished abruptly in the last three months. 相似文献
120.
Sri Yudawati Cahyarini Miriam Pfeiffer Oliver Timm Dieter Garbe Schönberg 《Geochimica et cosmochimica acta》2008,72(12):2841-2853
We compare several statistical routines that may be used to calculate δ18Osw and SSS from paired coral Sr/Ca and δ18O measurements. Typically, the δ18Ocoral-SST relationship is estimated by linear regression of coral δ18O vs. SST. If this method is applied, evidence should be given that at a particular site SST and SSS do not co-vary. In the tropical oceans, SST and δ18Osw (SSS) often co-vary, and this will bias the estimate of the regression slope of δ18Ocoral-SST. Using a stochastic model, we show that covariance leads to a bias in the coefficients of the univariate regression equations. As the slope of the δ18Ocoral-SST relationship has known, we propose to insert this value for γ1 in the regression models. This requires that the constants of the regression equations are removed. To omit the constants, we propose to center the regression equations (i.e., to remove the mean values from the variables). The statistical error propagation is calculated to assess our ability to resolve past variations in δ18Osw (SSS). At Tahiti, we find that the combined analytical uncertainties of coral δ18O and Sr/Ca equal the amplitude of the seasonal cycle of δ18Osw (SSS). Therefore, we cannot resolve the seasonal cycle of SSS at Tahiti. At Timor, the error of reconstructed δ18Osw (SSS) is lower than the magnitude of seasonal variations of δ18Osw (SSS), and the seasonal cycle of δ18Osw (SSS) can be resolved. 相似文献