921 resultados para annual speed change
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Tese de doutoramento, Biologia (Biologia Marinha e Aquacultura), Universidade de Lisboa, Faculdade de Ciências, 2016
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Long-term ecological data are essential for conservation and to monitor and evaluate the effects of environmental change. Bird populations have been routinely assessed on islands off the British coast for many years and here long term data for one such island, Skokholm, is evaluated for robustness in the light of some 20 changes in observers (wardens) on the island over nearly eight decades. It was found that the dataset was robust when compared to bootstrap data with no species showing significant changes in abundance in years when wardens changed. It is concluded that the breeding bird populations on Skokholm and other British offshore islands are an important scientific resource and that protocols should be enacted to ensure the archiving of records, the continuance of data collection using standardised protocols into the future, and the recognition of such long-term data for science in terms of an appropriate conservation designation.
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Photogrammetric reanalysis of 1985 aerial photos has revealed substantial submarine melting of the floating ice tongue of Jakobshavn Isbrae, west Greenland. The thickness of the floating tongue determined from hydrostatic equilibrium tapers from ~940 m near the grounding zone to ~600 m near the terminus. Feature tracking on orthophotos shows speeds on the July 1985 ice tongue to be nearly constant (~18.5 m/d), indicating negligible dynamic thinning. The thinning of the ice tongue is mostly due to submarine melting with average rates of 228 ± 49 m/yr (0.62 ± 0.13 m/d) between the summers of 1984 and 1985. The cause of the high melt rate is the circulation of warm seawater (thermal forcing of up to 4.2°C) beneath the tongue with convection driven by the substantial discharge of subglacial freshwater from the grounding zone. We believe that this buoyancy-driven convection is responsible for a deep channel incised into the sole of the floating tongue. A dramatic thinning, retreat, and speedup began in 1998 and continues today. The timing of the change is coincident with a 1.1°C warming of deep ocean waters entering the fjord after 1997. Assuming a linear relationship between thermal forcing and submarine melt rate, average melt rates should have increased by ~25% (~57 m/yr), sufficient to destabilize the ice tongue and initiate the ice thinning and the retreat that followed.
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Mode of access: Internet.
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"March 1991."--P.1.
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Public Act 93:248 requires the Property Tax Appeal Board to file an annual report that contains the following information for each county: (1) the total number of cases for commercial and industrial property requesting a reduction in assessed value of $100,000 or more for each of the last 5 years; (2) the total number of cases for commercial and industrial property decided by the Property Tax Appeal Board for each of the last 5 years; and (3) the total change in assessed value based on the Property Tax Appeal Board decisions for commercial property and industrial property for each of the last 5 years.
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"February 1965."
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"June 1965."
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"March 1972."
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"April 1972."
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"January 1975."
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"12 November 1980"--Change no. 3.
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Includes index.
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"September 1965."