829 resultados para Southeast Asia - Foreign relations - Australia


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We investigated changes in tropical climate and vegetation cover associated with abrupt climate change during Heinrich Event 1 (HE1, ca. 17.5 ka BP) using two different global climate models: the University of Victoria Earth System-Climate Model (UVic ESCM) and the Community Climate System Model version 3 (CCSM3). Tropical South American and African pollen records suggest that the cooling of the North Atlantic Ocean during HE1 influenced the tropics through a southward shift of the rain belt. In this study, we simulated the HE1 by applying a freshwater perturbation to the North Atlantic Ocean. The resulting slowdown of the Atlantic Meridional Overturning Circulation was followed by a temperature seesaw between the Northern and Southern Hemispheres, as well as a southward shift of the tropical rain belt. The shift and the response pattern of the tropical vegetation around the Atlantic Ocean were more pronounced in the CCSM3 than in the UVic ESCM simulation. For tropical South America, opposite changes in tree and grass cover were modeled around 10° S in the CCSM3 but not in the UVic ESCM. In tropical Africa, the grass cover increased and the tree cover decreased around 15° N in the UVic ESCM and around 10° N in the CCSM3. In the CCSM3 model, the tree and grass cover in tropical Southeast Asia responded to the abrupt climate change during the HE1, which could not be found in the UVic ESCM. The biome distributions derived from both models corroborate findings from pollen records in southwestern and equatorial western Africa as well as northeastern Brazil.

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In this study we present a sea surface temperature (SST) record from the western Arabian Sea for the last 20,000 years. We produced centennial-scale d18O and Mg/Ca SST time series of core NIOP929 with focus on the glacial-interglacial transition. The western Arabian Sea is influenced by the seasonal NE and SW monsoon wind systems. Lowest SSTs occur during the SW monsoon season because of upwelling of cold water, and highest SSTs can be found in the low-productivity intermonsoon season. The Mg/Ca-based temperature record reflects the integrated SST of the SW and NE monsoon seasons. The results show a glacial-interglacial SST difference of ~2°C, which is corroborated by findings from other Arabian Sea cores. At 19 ka B.P. a yet undescribed warm event of several hundred years duration is found, which is also reflected in the d18O record. A second centennial-scale high SST/low d18O event is observed at 17 ka B.P. This event forms the onset of the stepwise yet persistent trend toward Holocene temperatures. Highest Mg/Ca-derived SSTs in the NIOP929 record occurred between 13 and 10 ka B.P. Interglacial SST is ~24°C, indicating influence of upwelling. The onset of Arabian Sea warming occurs when the North Atlantic is experiencing minimum temperatures. The rapid temperature variations at 19, 17, and 13 ka B.P. are difficult to explain with monsoon changes alone and are most likely also linked to regional hydrographic changes, such as trade wind induced variations in warm water advection.

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At head of title: 93d Congress, 1st session. Committee print.

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At head of title: 93d Congress, 1st session, Senate, Executive report ; no. 93-16.

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At head of title: 93d Congress, 2d session. Committee print.

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Prepared by G. J. Pagliano and others.

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Mode of access: Internet.

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"International coffee agreement, 1962": p. 6-38.

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Mode of access: Internet.

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"The first to appear in a special series of Foreign Relations volumes on World War II."

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Mode of access: Internet.