3 resultados para Baccalaureate addresses--Harvard College (1636-1780)--17th century

em Aquatic Commons


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The Arctic charr of the British Isles are all non-migratory and are near their most southernmost range. Windermere is one of the few lowland lakes at southerly latitudes to contain a substantial proportion of Arctic charr. The first recorded mention of charr in Windermere was made around 1540 but it was not till the 17th century that different "sons" of charr were recognized, based on differences in their breeding behaviour. In the 1960's, the presence of two distinct populations, autumn spawners and spring spawners were discovered. In the 1980's it was shown that there were at least four races of charr in Windermere, based on genetic characteristics. Recently, the lake has changed due to inputs of phosphorus from treated sewage released into the lake resulting in eutrophication particularly in the south basin. Since the mid-1980's the numbers of charr caught in the south basin have declined.

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A distinct, 1- to 2-cm-thick flood deposit found in Santa Barbara Basin with a varve-date of 1605 AD ± 5 years testifies to an intensity of precipitation that remains unmatched for later periods when historical or instrumental records can be compared against the varve record. The 1605 AD ± 5 event correlates well with Enzel's (1992) finding of a Silver Lake playa perennial lake at the terminus of the Mojave River (carbon-14-dated 1560 AD ± 90 years), in relative proximity to the rainfall catchment area draining into Santa Barbara Basin. According to Enzel, such a persistent flooding of the Silver Lake playa occurred only once during the last 3,500 years and required a sequence of floods, each comparable in magnitude to the largest floods in the modern record. To gain confidence in dating of the 1605 AD ± 5 event, we compare Southern California's sedimentary evidence against historical reports and multi-proxy time-series that indicate unusual climatic events or are sensitive to changes in large-scale atmospheric circulation patterns. The emerging pattern supports previous suggestions that the first decade of the 17th century was marked by a rapid cooling of the Northern Hemisphere, with some indications for global coverage. A burst of volcanism and the occurrence of El Nino seem to have contributed to the severity of the events. The synopsis of the 1605 AD ± 5 years flood deposit in Santa Barbara Basin, the substantial freshwater body at Silver Lake playa, and much additional paleoclimatic, global evidence testifies for an equatorward shift of global wind patterns as the world experienced an interval of rapid, intense, and widespread cooling.