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81.
全球海气耦合模式中热盐环流对大气强迫的响应 总被引:16,自引:4,他引:16
大气环流与热盐环流 (THC)变化之间的因果关系 ,是海气相互作用研究领域的一个悬而未决的问题。作者利用一个全球海气耦合模式 -挪威卑尔根气候模式 (BCM)的 3 0 0a积分结果 ,讨论了冬季北大西洋涛动 (NAO)对海洋的强迫与热盐环流的年际调整之间的关系。结果发现 ,在NAO活动的正位相 ,伴随着中纬度西风带的加强 ,北大西洋拉布拉多海热通量损失剧增 ,同时海表盐度出现正距平 ,二者的共同作用 ,令表层海水变沉、密度增大 ,海洋层结出现不稳定 ,导致深对流发生。在NAO活动达到最强劲状态之后 3个月 ,拉布拉多海对流也达到最深。北大西洋热盐环流强度变化对拉布拉多海对流活动的响应 ,要滞后 3a左右。而在年际尺度上 ,大西洋的极向热输送变化和热盐环流的变化则基本是同步的。对流活动对大气存在明显的反馈作用。在对流活动深度达到最大之后 1~4个月 ,对流热释放令拉布拉多海表层气温明显升高 相似文献
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云南省东北部拱王山第四纪冰川遗迹研究 总被引:7,自引:6,他引:7
云南省东北部的拱王山海拔3100m以上的山地发生过第四纪冰川作用,典型的冰川遗迹集中分布在轿子山峰附近和妖精塘-牛洞坪两个地区,遗存的冰川地貌主要有冰斗,冰蚀岩盆和侧碛堤。根据冰川地貌的组合特征,以及它们生成的先后顺序,将拱王山第四纪冰川作用划分为末次冰期的倒数第二期冰期。 相似文献
84.
Using the data of ECMWF (European Center for Medium-range Weather Forecasts) to undertake composite diagnoses of 16 explosive cyclones occurring at the Atlantic and the Pacific Oceans,it is found that there are a lot of obvious discrepancies on the basic fields between these strong and weak explosive cyclones.The major reasons why the explosive cyclones over the Atlantic are stronger than those over the Pacific Ocean are that the non-zonal upper jet and the low-level warm moist flow over the Atlantic are stronger.The non-zonal upper jet offers stronger divergence,baroclinicity and baroclinic instability fields for explosive cyclones.Anticyclonic curvature at the high level of strong explosive cyclones is easy to make the inertia-gravitational wave developing at the moment of northward transfer of energy and stimulate the cyclones deepening quickly.Warm advection and diabatic heating can cause the upper isobaric surface lifting,as a result,the anticyclone curvature of cyclones enlarges,and wave energy develops easily as well.The most powerful period of the development of explosive cyclones is just the time when the positive vorticity advection center is located over the low vortex.At the upper level,when the distribution of potential vorticity contours changes suddenly from rareness to denseness,and the large values of the potential vorticity both in the west and north sides of cyclones extend downwards together,then cyclones are easy to explosively develop.The formation of strong explosive cyclones is closely related with the non-zonality of upper jet and the anticyclonic curvature. 相似文献
85.
Abstract. Recent discoveries of seafloor hydrothermal mineralization in submarine volcanic centers of felsic magma in western Pacific island arcs are regarded as modern analogues of Kuroko type deposits. Studies of these deposits and their surrounding geology raised question whether the exploration activity for the Kuroko deposits on land which peaked in the 1960's was adequate or not. However, such an evaluation is not easy because the exploration data are about to be lost as a result of the closure of all the Kuroko mines in the area since 1994.
The Metal Mining Agency of Japan (MMAJ), therefore, decided to compile existing data on about 180 Kuroko deposits and related mineral occurrences in northeast Japan as a new Kuroko database.
This study extends a concept called "exploration indices" which was developed based on a case study of the thoroughly surveyed Hokuroku district to draw a potential map of the Kuroko occurrences for the entire northeast Japan quantitatively with a Geographical Information System (GIS). Effective exploration indices include: 1) distribution of dacitic-rhy-olitic submarine volcanic rocks of the Nishikurosawa and Onnagawa stages, 2) distribution of intrusive rocks of pre- and post-Kuroko horizon, 3) low aeromagnetic anomaly caused by hydrothermal alteration of magnetite, 4) low gravity anomaly which suggests depressions in the basement rocks such as a tectonic basin and/or caldera, and 5) nearby existence of vein type deposits. It is concluded that about 33 % of known Kuroko deposits fall within the high potential zone (score=4 and 5) that occupies only 4 % of the entire northeast Japan arc. The Kuroko potential map is, therefore, useful for limiting the target area for Kuroko type deposits in an island arc setting. 相似文献
The Metal Mining Agency of Japan (MMAJ), therefore, decided to compile existing data on about 180 Kuroko deposits and related mineral occurrences in northeast Japan as a new Kuroko database.
This study extends a concept called "exploration indices" which was developed based on a case study of the thoroughly surveyed Hokuroku district to draw a potential map of the Kuroko occurrences for the entire northeast Japan quantitatively with a Geographical Information System (GIS). Effective exploration indices include: 1) distribution of dacitic-rhy-olitic submarine volcanic rocks of the Nishikurosawa and Onnagawa stages, 2) distribution of intrusive rocks of pre- and post-Kuroko horizon, 3) low aeromagnetic anomaly caused by hydrothermal alteration of magnetite, 4) low gravity anomaly which suggests depressions in the basement rocks such as a tectonic basin and/or caldera, and 5) nearby existence of vein type deposits. It is concluded that about 33 % of known Kuroko deposits fall within the high potential zone (score=4 and 5) that occupies only 4 % of the entire northeast Japan arc. The Kuroko potential map is, therefore, useful for limiting the target area for Kuroko type deposits in an island arc setting. 相似文献
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M. Roy-Barman C. Jeandel M. Souhaut M. Rutgers van der Loeff I. Voege N. Leblond R. Freydier 《Earth and Planetary Science Letters》2005,240(3-4):681-693
230Th, 232Th and 234Th were analyzed in sinking particles collected by moored and drifting sediment traps in the NE Atlantic Ocean (POMME experiment) in order to constrain the phase(s) carrying Th isotopes in the water column. It reveals a contrasted behaviour between 234Th and 230Th. 234Th is correlated to the particulate organic carbon suggesting that it is primarily scavenged by organic compounds in the surface waters. 230Thxs is correlated with Mn, Ba and the lithogenic fraction that are enriched in small suspended particles and incorporated in the sinking particulate flux throughout the water column. The lack of correlation between 230Thxs and CaCO3 or biogenic silica (bSi) indicates that CaCO3 and bSi are not responsible for 230Th scavenging in the deep waters of this oceanic region. 230Th is generally correlated with the lithogenic content of the trapped material but this correlation disappears in winter during strong atmospheric dust inputs suggesting that lithogenic matter is not directly responsible for 230Th scavenging in the deep waters or that sufficient time is required to achieve particle–solution equilibration. MnO2 could be the prevalent 230Thxs-bearing phase. The narrow range of Kd_MnO2Th obtained for very contrasted oceanic environments supports a global control of 230Thxs scavenging by MnO2 and raises the possibility that the 230Th–231Pa fractionation is controlled by the amount of colloidal MnO2 in seawater. 相似文献
89.
J.-M. Gherardi L. Labeyrie J.F. McManus R. Francois L.C. Skinner E. Cortijo 《Earth and Planetary Science Letters》2005,240(3-4):710-723
A first study from the subtropical western Atlantic, using 231Pa/230Th ratios as a kinematic proxy for deep water circulation, provided compelling evidence for a strong link between climate and the rate of Meridional Overturning Circulation (MOC) over the last deglaciation. However, these results warrant confirmation from additional locations and water depths because the interpretation of the sedimentary 231Pa/230Th ratio in terms of circulation vigor can be biased by variations in particle flux and composition. We have measured 231Pa/230Th in a core from the Iberian margin, in the Northeastern Atlantic basin, and have compared these new results to the data from the western Atlantic basin. We find that the reduction in the circulation during H1 and YD and the subsequent increases first recognized in the sediment deposited on Bermuda Rise are also evident in the eastern basin, in a totally different sedimentary regime, confirming that sedimentary 231Pa/230Th ratios record basin-wide changes in deep water circulation. However, some differences between the eastern and western records are also recognized, providing preliminary evidence to differentiate between renewal rates in the two North Atlantic basins and between shallower and deeper overturning. Our results suggest the possible existence of two sources of Glacial North Atlantic Intermediate Deep Water (GNAIW), one in the south Labrador Sea and another west of Rockall Plateau. Both sources contributed to the meridional overturning but the two had different sensitivity to meltwater from the Laurentide and the Fennoscandian ice sheets during the deglaciation. These results indicate that additional information on the geometry and strength of the ventilation of the deep Atlantic can be obtained by contrasting the evolution of sediment 231Pa/230Th in different sections of the Atlantic Ocean. 相似文献
90.