Effect of sea-level lowering on ELA depression during the LGM     

Brian Hanson  Roger LeB. Hooke 《Quaternary Research》2011,75(3):406-410

Decreases in equilibrium-line altitudes (ELAs) varied geographically during the last glacial maximum (LGM), with a mid-range value of ~ 900 m commonly deduced from altitude ratio and accumulation–area ratio calculations. Sea level, however, was 120 m lower during the LGM, so the ELA lowering relative to sea level would only be 780 m for a 900-m absolute lowering. With a lapse rate of 0.006°C m⁻¹, this implies a 4.7°C lowering of global temperature. It has been argued that this correction for sea-level change is unnecessary, but the logic on which this is based requires adiabatic compression to apply over much longer time scales than is typically invoked. We find that the correction is necessary. In addition, geometric changes in the atmosphere during the LGM, pointed out by Osmaston (2006), could lead to 0.4°C decrease in the average temperature of the troposphere. Additionally, orographic effects could significantly change the snow distribution on mountain masses near sea level.  相似文献   

Carbonate Mineral Saturation State as the Recruitment Cue for Settling Bivalves in Marine Muds     

Mark A. Green  George G. Waldbusser  Lane Hubazc  Eric Cathcart  Joshua Hall 《Estuaries and Coasts》2013,36(1):18-27

After a pelagic larval phase, infaunal bivalves undergo metamorphosis and transition to the underlying sediments to begin the benthic stage of their life history, where they explore and then either accept or reject sediments. Although the settlement cues used by juvenile infaunal bivalves are poorly understood, here we provide evidence that carbonate saturation state is a significant chemical cue in both direct observation laboratory studies and field manipulations. In the laboratory, plantigrade-stage Mercenaria mercenaria (200 μm shell height) showed a significant positive relationship between percent burrowed and Ω_aragonite, with an increasing probability of settlement with increasing saturation state. In the field, we increased bivalve recruitment by a factor of three in a 30-day field study by raising the pH (～0.3) and saturation state of surface sediments by buffering sediments with crushed shell (CaCO₃). The susceptibility of infaunal bivalves to dissolution mortality and the tight coupling of other sedimentary biogeochemical processes with carbonate dynamics suggest that mineral thermodynamics may be an overarching cue new settlers are responding to.  相似文献   

Constructing logbook-like statistics for coastal fisheries using coastal surveillance radar and fish market data     

《Marine Policy》2014

As catch and effort statistics including fishing time and location are essential for producing abundance indices for utilized fish stocks, fishing states are encouraged under the FAO Code of Conduct for Responsible Fisheries to collect and maintain such statistics. However, for coastal fisheries (including artisanal fisheries) that are mainly composed of small-sized vessels which are usually too numerous to monitor, fisheries statistics collection systems are often either lacking or of insufficient quality (e.g. incomplete or inaccurate). Vessel monitoring system (VMS) data are commonly used to construct or improve estimation of fishing effort and fishing location in large-scale fisheries. Most coastal fisheries lack VMS but their countries do have coastal surveillance radar systems (CSRS) for security and enforcement purposes. This study illustrates and recommends opportunistic use of CSRS data to provide similar scientific benefits to VMS data for coastal fisheries. CSRS in combination with market landings data can construct logbook-like catch and effort statistics. This study introduces a method and demonstrates its usefulness for scientific research and management purposes, including the potential to obtain a higher accuracy and precision, particularly for fishing location and catch amount. Limitations of the CSRS data and challenges to managers involved in its application are also discussed.  相似文献   

An algebraic approach to automated geospatial information fusion     

M. Duckham Corresponding author  M. Worboys 《International journal of geographical information science》2013,27(5):537-557

This paper presents a new technique for information fusion. Unlike most previous work on information fusion, this paper explores the use of instance‐level (extensional) information within the fusion process. This paper proposes an algorithm that can be used automatically to infer the schema‐level structure necessary for information fusion from instance‐level information. The approach is illustrated using the example of geospatial land‐cover data. The method is then extended to operate under uncertainty, such as in cases where the data are inaccurate or imprecise. The paper describes the implementation of the fusion method within a software prototype. Finally, the paper discusses several key topics for future research, including applications of this work to spatial‐data mining and the semantic web.  相似文献   

A timely opportunity to protect North Atlantic right whales in Canada     

《Marine Policy》2017

The survival of federally protected North Atlantic right whales (Eubalaena glacialis) requires an immediate reduction in the risk of entanglement in commercial fishing gear. This paper argues that at least a 30% reduction in risk is needed to meaningfully contribute to the conservation of right whales. The argument follows from risk estimates calculated using time and space intersections of right whales and fishing gear in Canadian waters. Almost all the risk occurs during July, August and September (12%, 50%, 37% respectively) and the groundfish fishery contributed the greatest proportion (86%) of annual risk. Given that efforts in the USA to reduce entanglement risk through modified fishing gear have been unsuccessful to date, we address the alternative option of restricting certain fishing gear at times and locations where entanglement risk is elevated. There are many options that Canada could employ to achieve the above risk reduction and our results clearly point to the most effective and efficient action being seasonally restricted fishing in two relatively small regions; the Grand Manan Basin and the Roseway Basin. Fully a third (34%±4%) of the annual risk is associated with these two basins, though fishery catch estimates in the basins are relatively small and declining.  相似文献   

Determining tidal turbine farm efficiency in the Western Passage using the disc actuator theory     

Shivanesh Rao  Huijie Xue  Min Bao  Simon Funke 《Ocean Dynamics》2016,66(1):41-57

Tidal power potential is determined across the Western Passage in Passamaquoddy Bay using the Finite Volume Community Ocean Model (FVCOM). The tidal turbines are implemented in FVCOM using the disc actuator theory method to determine the power potential for different densities and arrangements of tidal turbines. At the most efficient setting for 10 turbines across the Western Passage, the optimal turbine drag coefficient is 2.0 and the average power output, in a 2-week period, is ～819 kW. Results suggest that for a single row of turbines, the addition of turbines decreases the efficiency of the turbine farm, but this decrease in efficiency is less than 7 %. A parallel distribution of turbines in an array diminishes the average power for turbines in the shadow of other turbines, while staggered distribution in an array increases the average power extraction for some turbines, due to the speed gains in the gaps between turbines. A simple tidal farm optimization using the OpenTidalFarm (OTF) model suggests a similar tidal farm distribution.  相似文献   

Resistance to oxidative stress is not associated with the exceptional longevity of the freshwater pearl mussel,Margaritifera margaritifera nor three unionid species     

Iain Ridgway  T. J. Bowden  A. Roman-Gonzalez  C. A. Richardson 《Aquatic Sciences - Research Across Boundaries》2014,76(2):259-267

Bivalve molluscs are newly discovered models of successful ageing. Here, we test the hypothesis that extreme longevity of freshwater mussels is associated with an enhanced resistance to oxidative stress. We assess whether resistance to oxidative stress might be causally involved in the exceptional longevity exhibited by the freshwater pearl mussel Margaritifera margaritifera. We compared resistance to oxidative stress and total haemocyte counts, a health status biomarker in M. margaritifera (maximum lifespan potential 190 years) with three other freshwater bivalve species spanning a range of longevities. Previous studies of the comparative stress resistance and longevity of marine bivalves provide evidence for the hypothesis that an association exists between longevity and not only an enhanced resistance to oxidative stress but also a general resistance to multiplex stressors. We compared baseline total haemocyte counts, age-related changes, and responses to exposure to the oxidative stressor tert-butyl hydroperoxide (TBHP). Surprisingly our data does not support the premise that extreme longevity in M. margaritifera is associated with enhanced resistance to oxidative stress. In comparison with its shorter-lived counter parts M. margaritifera was the least resistance to oxidative stress. Following TBHP exposure, no association between longevity and resistance to oxidative stress-induced mortality nor a marked resistance to oxidative stress-induced declines in total haemocyte counts were observed. The results suggest longevity evolved separately in freshwater mussels and this group warrants further attention from biogerontologists because such study may provide novel insights not detected through the study of the marine members of the class, where most attention is currently focused.  相似文献   

Investigations on 3D effects and correlation between wave height and lip submergence of an offshore stationary OWC wave energy converter     

《Applied Ocean Research》2017

Understanding the hydrodynamic interactions between ocean waves and the oscillating water column (OWC) wave energy converter is crucial for improving the device performance. Most previous relevant studies have focused on testing onshore and offshore OWCs using 2D models and wave flumes. Conversely, this paper provides experimental results for a 3D offshore stationary OWC device subjected to regular waves of different heights and periods under a constant power take–off (PTO) damping simulated by an orifice plate of fixed diameter. In addition, a 3D computational fluid dynamics (CFD) model based on the RANS equations and volume of fluid (VOF) surface capturing scheme was developed and validated against the experimental data. Following the validation stage, an extensive campaign of computational tests was performed to (1) discover the impact of testing such an offshore OWC in a 2D domain or a wave flume on device efficiency and (2) investigate the correlation between the incoming wave height and the OWC front wall draught for a maximum efficiency via testing several front lip draughts for two different rear lip draughts under two wave heights and a constant PTO damping. It is found that the 2D and wave flume modelling of an offshore OWC significantly overestimate the overall power extraction efficiency, especially for wave frequencies higher than the chamber resonant frequency. Furthermore, a front lip submergence equal to the wave amplitude affords maximum efficiency whilst preventing air leakage, hence it is recommended that the front lip draught is minimized.  相似文献   

A 1/8° coupled biochemical-physical Indian Ocean Regional Model: Physical results and validation   总被引：1，自引：1，他引：0  

Ke Huang  Sergio Derada  Huijie Xue  Peng Xiu  Fei Chai  Qiang Xie  Dongxiao Wang 《Ocean Dynamics》2015,65(8):1121-1142

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Impacts of mesoscale eddies in the South China Sea on biogeochemical cycles   总被引：1，自引：1，他引：0  

Mingxian Guo  Fei Chai  Peng Xiu  Shiyu Li  Shivanesh Rao 《Ocean Dynamics》2015,65(9-10):1335-1352

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