Physical and chemical impacts of a major storm on a temperate lake: a taste of things to come?

Extreme weather can have a substantial influence on lakes and is expected to become more frequent with climate change. We explored the influence of one particular extreme event, Storm Ophelia, on the physical and chemical environment of England's largest lake, Windermere. We found that the substantial influence of Ophelia on meteorological conditions at Windermere, in particular wind speed, resulted in a 25-fold increase (relative to the study-period average) in the wind energy flux at the lake-air interface. Following Ophelia, there was a short-lived mixing event in which the Schmidt stability decreased by over 100 Jm-2 and the thermocline deepened by over 10 m during a 12-hour period. As a result of changes to the strength of stratification, Ophelia also changed the internal seiche regime of Windermere with the dominant seiche period increasing from ~17 h pre-storm to ~21 h post-storm. Following Ophelia, there was an upwelling of cold and low-oxygenated waters at the southern-end of the lake. This had a substantial influence on the main outflow of Windermere, the River Leven, where dissolved oxygen concentrations decreased by ~48 %, from 9.3 mg L-1 to 4.8 mg L-1, while at the mid-lake monitoring station in Windermere, it decreased by only ~3%. This study illustrates that the response of a lake to extreme weather can cause important effects downstream, the influence of which may not be evident at the lake surface. To understand the impact of future extreme events fully, the whole lake and downstream-river system need to be studied together

Caravan porters of the Nyika, labour, culture, and society in nineteenth century Tanzania

grantor: University of TorontoCaravan porters were vital to the functioning of trade and transportation throughout precolonial and early colonial Sub-Saharan Africa. In nineteenth century East Africa, the world's largest supplier of ivory. Lens of thousands of caravan porters carried ivory to the coast from all parts of the interior. Porterage was the only form of land transportation because sleeping sickness precluded the use of pack or draft animals. Porters were the first migrant labourers in the region and were transmitters of new ideas. Porterage has received only cursory attention in spite of its centrality to precolonial African labour history, which to date has concentrated on slave studies. This has led to an assumption that free migrant labour emerged only from colonial economies. This view needs to be modified. In Tanzania most porters were wage labourers, and many were professionals. The emergence of the professional porter was an African response to East African conditions rather than a consequence of the decline of indigenous entrepreneurship, or a process of impoverishment caused by outside forces. It is incorrect to imagine rural society everywhere as on the defensive. Some groups, like the Nyamwezi, were at the forefront of change. Entrepreneurship, the market, and wage labour were becoming increasingly familiar to them. Forms of caravan organization and work invented by the Nyamwezi and influenced by others became dominant. Over time, Nyamwezi work norms and leisure activities formed at home and on safari came to constitute the main features of a broad "caravan culture," an integrating way of life along the central caravan routes between Lake Tanganyika and the coast, and along the branch routes. Attention to the subtleleties of culture shows how porters struggled to defend concepts of work derived from their own experience from outsiders determined to impose different working patterns. Porters successfully bargained with employers over conditions, discipline, rations, and payment, which had become standardized by custom. Porters were able to force up wages at crucial junctures. Customary patterns of work survived into the early colonial period. Foreign travellers had little choice but to bow to custom, with some adaptations.Ph.D