Browsing by Author "Rouault, M"
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- ItemOpen AccessEstimation of sea-surface temperature around southern Africa from satellite-derived microwave observations(2003) Rouault, M; Lutjeharms, J R ESea-surface temperatures may give strong indications of the location of fronts, currents, eddies and other components of ocean circulation. This has been recognized in particular for the seas around southern Africa. Almost all studies using this property have employed measurements of thermal infrared radiation from orbiting satellites. This has distinct disadvantages due to the shading effect of persistent cloud cover. Another option is to use microwave observations, which are not affected by cloud cover. Until recently, however, the spatial resolution of microwave data was far too coarse for the purpose of studying ocean circulation in detail. We describe here a new set of microwave data that does not have this disadvantage, and show how useful it is by describing examples of local applications.
- ItemOpen AccessMonitoring the oceanic flow between Africa and Antarctica: Report of the first GoodHope cruise(2005) Ansorge, I J; Speich, S; Lutjeharms, J R E; Goni, G J; Rautenbach, C J de W; Froneman, P W; Rouault, M; Garzoli, S LThe southern ocean plays a major role in the global oceanic circulation role in the global oceanic circulation, as a component of the Meridional Overturning Circulation, and it is postulated that it has a great influence on present-day climate. However, our understanding of its complex three-dimensional dynamics and of the impact of its variability on the climate system is rudimentary. The newly constituted, international GoodHope research venture aims to address this knowledge gap by establishing a programme of regular observations across the Southern Ocean between the African and Antarctic continents. The objectives of this programme are fivefold: (1) to improve understanding of Indo-Atlantic inter-ocean exchanges and their impact on the global thermohaline circulation and thus on global climate change; (2) to understand in more detail the influence these exchanges have on the climate variability of the southern African subcontinent; (3) to monitor the variability of the main Southern Ocean frontal systems associated with the Antarctic Circumpolar Current; (4) to study air–sea exchanges and their role on the global heat budget, with particular emphasis on the intense exchanges occurring within the Agulhas Retroflection region south of South Africa, and (5) to examine the role of major frontal systems as areas of elevated biological activity and as biogeographical barriers to the distribution of plankton. We present here preliminary results on the physical and biological structure of the frontal systems using the first GoodHope transect that was completed during February–March 2004.
- ItemOpen AccessSea-surface temperatures at the sub-Antarctic islands Marion and Gough during the past 50 years(2003) Mélice, J-L; Lutjeharms, J R E; Rouault, M; Ansorge, I JSea-surface temperatures (SSTs) have been measured at Marion and Gough islands for nearly 50 years. These are some of the longest records of their kind in the sub-Antarctic. We present the trend, the seasonal cycle, and the time-frequency characteristics of the SST for both islands, which rose by 1.4°C at Marion Island and by 0.5°C at Gough Island over the 50-year period. Intermittent temperature oscillations, with periods of between 1 and 5 years, were observed throughout the record. A 5-year periodicity, compatible with an Antarctic CircumpolarWave signature, dominated after 1990 in both records. We also observed a strong low-frequency component with a period varying from 9.3 to 11.4 years at Marion Island, and a much weaker component with a period varying from 9.9 to 11.8 years at Gough Island.