3,342 research outputs found
Briefing: Auditor/company interactions in the 2007 UK regulatory environment
No abstract availabl
Non-local dispersal
We consider a model of spatial spread that has applications in both material science and biology. The classical models are based upon partial differential equations, in particular reaction-diffusion equations. Here the dispersal term is given in terms of an integral operator and we restrict ourselves to the scalar case
Time-restricted feeding of pigs: social and feeding behavior
Twenty finishing pigs were used to evaluate effects of time-restricted feeding on social interactions and feeding patterns of pigs at feeding time. Correlation analysis for pairs of traits, involving feeding activities, social interactions, and rate of gain indicate that more aggressive pigs went first to the feeder, fed more frequently, and gained faster. Although on continuous artificial lighting, timed-fed pigs displayed more feeding and aggressive behavior during day light hours.; Swine Day, Manhattan, KS, November 15, 198
The role of the Southern Ocean in abrupt transitions and hysteresis in glacial ocean circulation
Highālatitude Northern Hemisphere climate during the last glacial period was characterized by a series of abrupt climate changes, known as DansgaardāOeschger (DO) events, which were recorded in Greenland ice cores as shifts in the oxygen isotopic composition of the ice. These shifts in inferred Northern Hemisphere highālatitude temperature have been linked to changes in Atlantic meridional overturning strength. The response of ocean overturning circulation to forcing is nonālinear and a hierarchy of models have suggested that it may exist in multiple steady state configurations. Here, we use a timeādependent coarseāresolution isopycnal model with four density classes and two basins, linked by a Southern Ocean to explore overturning states and their stability to changes in external parameters. The model exhibits hysteresis in both the steadyāstate stratification and overturning strength as a function of the magnitude of North Atlantic Deep Water (NADW) formation. Hysteresis occurs as a result of two nonālinearities in the modelāāāthe surface buoyancy distribution in the Southern Ocean and the vertical diffusivity profile in the Atlantic and IndoāPacific basins. We construct a metric to assess circulation configuration in the model, motivated by observations from the Last Glacial Maximum, which show a different circulation structure from the modern. We find that circulation configuration is primarily determined by NADW density. The model results are used to suggest how ocean conditions may have influenced the pattern of DO events across the last glacial cycle
A high-resolution record of Southern Ocean intermediate water radiocarbon over the past 30,000 years
The circulation of intermediate waters plays an important role in global heat and carbon transport in the ocean and changes in their distribution are closely tied to glacialāinterglacial climate change. Coupled radiocarbon and U/Th measurements on deep-sea Desmophyllum dianthus corals allow for the reconstruction of past intermediate water ventilation. We present a high-resolution time series of Antarctic Intermediate Water radiocarbon from 44 corals spanning 30 ka through the start of the Holocene, encompassing the transition into the Last Glacial Maximum (LGM) and the last deglaciation. Corals were collected south of Tasmania from water depths between 1430 and 1950 m with 80% of them between 1500 and 1700 m, giving us a continuous record from a narrow depth range. The record shows three distinct periods of circulation: the MIS 3ā2 transition, the LGM/Heinrich Stadial 1 (extending from ā¼22 to 16 kyr BP), and the Antarctic Cold Reversal (ACR). The MIS 3ā2 transition and the ACR are characterized by abrupt changes in intermediate water radiocarbon while the LGM time period generally follows the atmosphere at a constant offset, in support of the idea that the LGM ocean was at steady state for its ^(14)C distribution. Closer inspection of the LGM time period reveals a 40ā° jump at ā¼19 ka from an atmospheric offset of roughly 230ā° to 190ā°, coincident with an observed 10ā15 m rise in sea level and a southward shift of the Subantarctic and Polar Fronts, an abrupt change not seen in deeper records. During the ACR time period intermediate water radiocarbon is on average less offset from the atmosphere (ā¼110ā°ā¼110ā°) and much more variable. This variability has been captured within the lifetimes of three individual corals with changes of up to 35ā° over ā¼40 yr, likely caused by the movement of Southern Ocean fronts. This surprising result of relatively young and variable intermediate water radiocarbon during the ACR seems to go against the canonical idea of reduced circulation and ventilation in the south during this time period. However comparisons with other records from the Southern Ocean highlight zonal asymmetries, which can explain the deviation of our Tasmanian record from those in Drake Passage and the eastern Pacific. These signals seen in Tasmanian intermediate water Ī^(14)C can also be found in Greenland ice core Ī“^(18)O and East Asian monsoon strength. Throughout the LGM and the deglaciation, our Tasmanian intermediate water record is sensitive to times when the upper and lower cells of the meridional overturning circulation are more or less interconnected, which has important implications for the global climate system on glacialāinterglacial time scales
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