ISTANBUL'S BOSTANS: A MILLENNIUM OF MARKET GARDENS*

ABSTRACT. For centuries, a network of market gardens throughout Istanbul provisioned the city with fresh vegetables. These bostans and their gardeners held a respected place in Istanbul life, contributing to the city's food and employment needs. Today, only fragments remain. Massive urban development, intense competition for metropolitan space, modernization, changing institutions and laws, and the global industrialization of food have threatened this tradition with extinction. But in spite of the overwhelming forces behind their demise, some of Istanbul's bostans persist. Efforts to support and promote the gardens, and to draw from the expertise and experience of their gardeners, are emerging. From a historical perspective, this article examines Istanbul's bostans to understand their meaning and contribution to the city's people and landscape.     

Interannual variation of Gulf Stream heat transport in a high-resolution model forced by reanalysis data

The variability present in a 1/6th degree Atlantic ocean simulation forced by analysed wind stress and heat flux over a 20-year period is investigated by means of heat transport diagnostics. A section is defined which follows the Gulf Stream and its seaward extension, and transport of heat across this section is analysed to reveal the physical mechanisms responsible for intergyre heat exchanges on a variety of time scales. Heat transport across another section that crosses the Gulf Stream is also diagnosed to reveal the temporal behaviour of the gyre circulation. The Ekman response to wind stress variations accounts for the annual cycle and much of the interannual variability in both measures. For the intergyre heat transports, cancellation by transient-mean flow terms leads to a very weak annual cycle. Transient eddies account for approximately half the total intergyre transport of 0.7 Petawatts. They also account for a significant fraction of the interannual variability, but separate experiments with repeated-annual-cycle forcing indicate that the transient eddy component of the heat transport variability is internally generated. Links between the intergyre transport, the wind-driven gyre circulation, the surface heat budget and the atmospheric North Atlantic Oscillation are discussed.     

Linking the northern hemisphere sea-ice reduction trend and the quasi-decadal arctic sea-ice oscillation

The nature of the reduction trend and quasi-decadal oscillation in Northern Hemisphere sea-ice extent is investigated. The trend and oscillation that seem to be two separate phenomena have been found in data. This study examines a hypothesis that the Arctic sea-ice reduction trend in the last three decades amplified the quasi-decadal Arctic sea-ice oscillation (ASIO) due to a positive ice/ocean-albedo feedback, based on data analysis and a conceptual model proposed by Ikeda et al. The theoretical, conceptual model predicts that the quasi-decadal oscillation is amplified by the thinning sea-ice, leading to the ASIO, which is driven by the strong positive feedback between the atmosphere and ice-ocean systems. Such oscillation is predicted to be out-of-phase between the Arctic Basin and the Nordic Seas with a phase difference of 3/4, with the Nordic Seas leading the Arctic. The wavelet analysis of the sea ice data reveals that the quasi-decadal ASIO occurred actively since the 1970s following the trend starting in the 1960s (i.e., as sea-ice became thinner and thinner), as the atmosphere experienced quasi-decadal oscillations during the last century. The wavelet analysis also confirms the prediction of such out-of-phase feature between these two basins, which varied from 0.62 in 1960 to 0.25 in 1995. Furthermore, a coupled ice-ocean general circulation model (GCM) was used to simulate two scenarios, one without the greenhouse gas warming and the other having realistic atmospheric forcing along with the warming that leads to sea-ice reduction trend. The quasi-decadal ASIO is excited in the latter case compared to the no-warming case. The wavelet analyses of the simulated ice volume were also conducted to derive decadal ASIO and similar phase relationship between the Arctic Ocean and the Nordic Seas. An independent data source was used to confirm such decadal oscillation in the upper layer (or freshwater) thickness, which is consistent with the model simulation. A modified feedback loop for the sea-ice trend and ASIO was proposed based on the previous one by Mysak and Venegas and the ice/albedo and cloud/albedo feedabcks, which are responsible for the sea ice reduction trend.     

Impact of copper smelting on lakes in the southern Ural Mountains,Russia, inferred from chironomids

Karabash (52°2 N, 60°10 E) is a copper smelting town in the southern Ural Mountains of Russia. The town is affected by sulphur dioxide emissions and deposition of metal-rich particulates from the smelter, acid drainage from old mine workings, and leachates from disused waste dumps and tailings dams. The close proximity of houses to these sources of pollution is of concern to human health and has devastated terrestrial vegetation in the environs. The environmental impact of the smelter on lakes in the area has been assessed using chironomids. Short sediment cores were taken from 16 lakes within a 50 km radius of the smelter and the composition of the chironomid fauna from the bottom of each core, representing conditions prior to the commissioning of the smelter in 1910, was compared with the present chironomid fauna in the surface sediments. Redundancy analysis (RDA) showed that changes in the chironomid fauna of most lakes were driven by trophic change, independent of the industrial activity. Lakes and ponds adjacent to the smelter and waste dumps, which directly receive contaminated waters were devoid of macro- and mesofauna and flora, but there is no evidence that other lakes have been severely impacted by smelter emissions. Local geology ensures that the lakes are well-buffered to the effects of acid deposition which will limit the bioavailability of metals in the water column and sediment.     

Dynamic modelling of passive margin salt tectonics: effects of water loading, sediment properties and sedimentation patterns

We investigate the evolution of passive continental margin sedimentary basins that contain salt through two‐dimensional (2D) analytical failure analysis and plane‐strain finite‐element modelling. We expand an earlier analytical failure analysis of a sedimentary basin/salt system at a passive continental margin to include the effects of submarine water loading and pore fluid pressure. Seaward thinning sediments above a weak salt layer produce a pressure gradient that induces Poiseuille flow in the viscous salt. We determine the circumstances under which failure at the head and toe of the frictional–plastic sediment wedge occurs, resulting in translation of the wedge, landward extension and seaward contraction, accompanied by Couette flow in the underlying salt. The effects of water: (i) increase solid and fluid pressures in the sediments; (ii) reduce the head to toe differential pressure in the salt and (iii) act as a buttress to oppose failure and translation of the sediment wedge. The magnitude of the translation velocity upon failure is reduced by the effects of water. The subsequent deformation is investigated using a 2D finite‐element model that includes the effects of the submarine setting and hydrostatic pore pressures. The model quantitatively simulates a 2D approximation of the evolution of natural sedimentary basins on continental margins that are formed above salt. Sediment progradation above a viscous salt layer results in formation of landward extensional basins and listric normal growth faults as well as seaward contraction. At a later stage, an allochthonous salt nappe overthrusts the autochthonous limit of the salt. The nature and distribution of major structures depends on the sediment properties and the sedimentation pattern. Strain weakening of sediment favours landward listric growth faults with formation of asymmetric extensional depocentres. Episodes of low sediment influx, with partial infill of depocentres, produce local pressure gradients in the salt that result in diapirism. Diapirs grow passively during sediment aggradation.     

Dynamics of mule deer forage in the Sonoran Desert

Forage availability for mule deer (Odocoileus hemionus) in the Sonoran Desert depends on plant biomass, which is influenced by rainfall. We determined how rainfall, temperature and plant characteristics affected biomass of deer forage. We measured forage biomass, rainfall and temperature every 3 months from April 2000 to December 2002. Quarterly rainfall ranged from <1 to 57 mm, and forage biomass in desert washes fluctuated between 6 and 34 g m⁻². There was a positive relationship between forage biomass and rainfall the previous six months (p<0.001), and a negative relationship between biomass and average temperature the previous 3 months (p<0.001). Quarterly forage growth was positively influenced by rainfall (p<0.001) and negatively influenced by forage biomass (p<0.001). The relationships between deer forage and environmental factors established here will be useful in understanding population ecology of mule deer as part of an interactive model of plant–herbivore dynamics in arid environments.