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1.
Sea surface temperatures (SSTs) in the cold tongue of the eastern equatorial Pacific exert powerful controls on global atmospheric circulation patterns. We examined climate variability in this region from the Last Glacial Maximum (LGM) to the present, using a SST record reconstructed from magnesium/calcium ratios in foraminifera from sea-floor sediments near the Galápagos Islands. Cold-tongue SST varied coherently with precession-induced changes in seasonality during the past 30,000 years. Observed LGM cooling of just 1.2 degrees C implies a relaxation of tropical temperature gradients, weakened Hadley and Walker circulation, southward shift of the Intertropical Convergence Zone, and a persistent El Ni?o-like pattern in the tropical Pacific. This is contrasted with mid-Holocene cooling suggestive of a La Ni?a-like pattern with enhanced SST gradients and strengthened trade winds. Our results support a potent role for altered tropical Pacific SST gradients in global climate variations. 相似文献
2.
The ocean currents connecting the western tropical Pacific Ocean with the eastern tropical Pacific Ocean are driven by surface winds. The surface winds are in turn driven by the sea-surface temperature (SST) differences between these two regions. This dynamic coupling between the atmosphere and ocean may limit the SST in the tropical Pacific Ocean to below 305 kelvin even in the absence of cloud feedbacks. 相似文献
3.
利用常规气象观测资料和国家气候中心的赤道中东太平洋海表温度、850 hPa纬向风距平和副热带高压脊线的数据,使用天气学分析方法,对2010年8月葫芦岛地区高频次暴雨的气候背景及环流形势进行分析。结果表明:2010年7月以来,赤道中东太平洋海表温度较常年同期偏低1.5～2.5℃,快速进入拉尼娜状态;热带地区低层850 hPa赤道中太平洋出现纬向风的强的负趋势,Walker环流有明显增强的正趋势;副高明显偏强,利于西太平洋暖湿的气流沿副高边缘向我国东北地区输送;3次暴雨过程均具有完整的高低空配置,低层辐合、高层辐散,水汽充沛,具有对流不稳定层结。 相似文献
4.
Black DE Peterson LC Overpeck JT Kaplan A Evans MN Kashgarian M 《Science (New York, N.Y.)》1999,286(5445):1709-1713
Climate in the tropical North Atlantic is controlled largely by variations in the strength of the trade winds, the position of the Intertropical Convergence Zone, and sea surface temperatures. A high-resolution study of Caribbean sediments provides a subdecadally resolved record of tropical upwelling and trade wind variability spanning the past 825 years. These results confirm the importance of a decadal (12- to 13-year) mode of Atlantic variability believed to be driven by coupled tropical ocean-atmosphere dynamics. Although a well-defined interdecadal mode of variability does not appear to be characteristic of the tropical Atlantic, there is evidence that century-scale variability is substantial. The tropical Atlantic may also have been involved in a major shift in Northern Hemisphere climate variability that took place about 700 years ago. 相似文献
5.
Legeckis R 《Science (New York, N.Y.)》1977,197(4309):1179-1181
During 1975, westward-moving long waves with a period of about 25 days and a wavelength of 1000 kilometers were observed at a sea surface temperature front in the equatorial Pacific on infrared images obtained by a geostationary environmental satellite system. The absence of these waves during 1976, and the above-average equatorial sea surface temperatures during 1976, may be related to a decrease in the southeasterly trade winds during that year. 相似文献
6.
Interdecadal Climate Fluctuations That Depend on Exchanges Between the Tropics and Extratropics 总被引：14，自引：0，他引：14
The unexpected and prolonged persistence of warm conditions over the tropical Pacific during the early 1990s can be attributed to an interdecadal climate fluctuation that involves changes in the properties of the equatorial thermocline arising as a result of an influx of water with anomalous temperatures from higher latitudes. The influx affects equatorial sea-surface temperatures and hence the tropical and extratropical winds that in turn affect the influx. A simple model demonstrates that these processes can give rise to continual interdecadal oscillations. 相似文献
7.
The role of El Ni?o-Southern Oscillation (ENSO) in greenhouse warming and climate change remains controversial. During the warmth of the early-mid Pliocene, we find evidence for enhanced thermocline tilt and cold upwelling in the equatorial Pacific, consistent with the prevalence of a La Ni?a-like state, rather than the proposed persistent warm El Ni?o-like conditions. Our Pliocene paleothermometer supports the idea of a dynamic "ocean thermostat" in which heating of the tropical Pacific leads to a cooling of the east equatorial Pacific and a La Ni?a-like state, analogous to observations of a transient increasing east-west sea surface temperature gradient in the 20th-century tropical Pacific. 相似文献
8.
Large-scale, westward-extending tongues of warm (Pacific) and cold (Atlantic) water are found between 2000 and 3000 meters both north and south of the equator in the Pacific and Atlantic oceans. They are centered at 5 degrees to 8 degrees north and 10 degrees to 15 degrees south (Pacific) and 5 degrees to 8 degrees north and 15 degrees to 20 degrees south (Atlantic). They are separated in both oceans by a contrasting eastward-extending tongue, centered at about 1 degrees to 2 degrees south, in agreement with previous helium isotope observations (Pacific). Thus, the indicated deep tropical westward flows north and south of the equator and eastward flow near the equator may result from more general forcing than the hydrothermal forcing previously hypothesized. 相似文献
9.
Since 1968 a significant increase in total chlorophyll a in the water column during the summer in the central North Pacific Ocean has been observed. A concomitant increase in winter winds and a decrease in sea surface temperature suggest that long-period fluctuations in atmospheric characteristics have changed the carrying capacity of the central Pacific epipelagic ecosystem. 相似文献
10.
Modulation of hurricane activity in the gulf of mexico by the madden-julian oscillation 总被引：4，自引：0，他引：4
The Madden-Julian oscillation (MJO) is a large-scale episodic modulation of tropical winds and precipitation that travels eastward from Asia to America, with a characteristic repeat time of 30 to 60 days. Here it is shown that when MJO wind anomalies in the lower troposphere of the eastern Pacific are westerly, Gulf of Mexico and western Caribbean hurricane genesis is four times more likely than when the MJO winds are easterly. Accurate predictions of the MJO may lead to improved long-range forecasts of tropical cyclone activity. 相似文献
11.
Easterly trade winds from near-equatorial islands in the central Pacific weakened before each El Ni?o between 1950 and 1978, except for the 1963 El Ni?o. The weakening of the easterlies and their later collapse did not occur uniformly over several months, but rather through a series of strong westerly wind bursts lasting 1 to 3 weeks. The bursts may force equatorial Kelvin waves in the ocean that can both initiate and sustain the sea surface warming characteristics of El Ni?o events. 相似文献
12.
DT Rodbell GO Seltzer DM Anderson MB Abbott DB Enfield JH Newman 《Science (New York, N.Y.)》1999,283(5401):516-520
Debris flows have deposited inorganic laminae in an alpine lake that is 75 kilometers east of the Pacific Ocean, in Ecuador. These storm-induced events were dated by radiocarbon, and the age of laminae that are less than 200 years old matches the historic record of El Nino events. From about 15,000 to about 7000 calendar years before the present, the periodicity of clastic deposition is greater than or equal to 15 years; thereafter, there is a progressive increase in frequency to periodicities of 2 to 8.5 years. This is the modern El Nino periodicity, which was established about 5000 calendar years before the present. This may reflect the onset of a steeper zonal sea surface temperature gradient, which was driven by enhanced trade winds. 相似文献
13.
The equatorial Pacific is the largest oceanic source of carbon dioxide to the atmosphere and has been proposed to be a major site of organic carbon export to the deep sea. Study of the chemistry and biology of this area from 170 degrees to 95 degrees W suggests that variability of remote winds in the western Pacific and tropical instability waves are the major factors controlling chemical and biological variability. The reason is that most of the biological production is based on recycled nutrients; only a few of the nutrients transported to the surface by upwelling are taken up by photosynthesis. Biological cycling within the euphotic zone is efficient, and the export of carbon fixed by photosynthesis is small. The fluxes of carbon dioxide to the atmosphere and particulate organic carbon to the deep sea were about 0.3 gigatons per year, and the production of dissolved organic carbon was about three times as large. The data establish El Ni?o events as the main source of interannual variability. 相似文献
14.
El nino-southern oscillation displacements of the Western equatorial pacific warm pool 总被引：1，自引：0，他引：1
The western equatorial Pacific warm pool (sea-surface temperatures >29 degrees C) was observed to migrate eastward across the date line during the 1986-1987 El Ni?o-Southern Oscillation event. Direct velocity measurements made in the upper ocean from 1986 to 1988 indicate that this migration was associated with a prolonged reversal in the South Equatorial Current forced by a large-scale relaxation ofthe trade winds. The data suggest that wind-forced zonal advection plays an important role in the thermodynamics of the western Pacific warm pool on interannual time scales. 相似文献
15.
Bernstein RL 《Science (New York, N.Y.)》1974,183(4120):71-72
A set of subsurface temperature measurements in the trade wind region northeast of Hawaii reveals large perturbations about the mean state, with zonal wavelengths of 480 kilometers. The perturbations are identified as mesoscale baroclinic eddies, and they appear to drift westward at a rate of 4.7 +/- 2.0 centimeters per second. The large-scale ( 1000 kilometers) baroclinic flow at a depth of 200 meters is 1.5 +/- 0.7 centimeters per second, also toward the west, and comparable in magnitude with the eddy drift velocity; this finding suggests that the eddy drift is strongly influenced by the large-scale flow. Mesoscale eddies have been discovered in the tropical and subtropical Atlantic Ocean. Their existence in the Pacific Ocean is now confirmed. 相似文献
16.
Climate impact of late quaternary equatorial pacific sea surface temperature variations 总被引：3，自引：0，他引：3
Magnesium/calcium data from planktonic foraminifera in equatorial Pacific sediment cores demonstrate that tropical Pacific sea surface temperatures (SSTs) were 2.8 degrees +/- 0.7 degrees C colder than the present at the last glacial maximum. Glacial-interglacial temperature differences as great as 5 degrees C are observed over the last 450 thousand years. Changes in SST coincide with changes in Antarctic air temperature and precede changes in continental ice volume by about 3 thousand years, suggesting that tropical cooling played a major role in driving ice-age climate. Comparison of SST estimates from eastern and western sites indicates that the equatorial Pacific zonal SST gradient was similar or somewhat larger during glacial episodes. Extraction of a salinity proxy from the magnesium/calcium and oxygen isotope data indicates that transport of water vapor into the western Pacific was enhanced during glacial episodes. 相似文献
17.
A tropical Pacific climate state resembling that of a permanent El Ni?o is hypothesized to have ended as a result of a reorganization of the ocean heat budget approximately 3 million years ago, a time when large ice sheets appeared in the high latitudes of the Northern Hemisphere. We report a high-resolution alkenone reconstruction of conditions in the heart of the eastern equatorial Pacific (EEP) cold tongue that reflects the combined influences of changes in the equatorial thermocline, the properties of the thermocline's source waters, atmospheric greenhouse gas content, and orbital variations on sea surface temperature (SST) and biological productivity over the past 5 million years. Our data indicate that the intensification of Northern Hemisphere glaciation approximately 3 million years ago did not interrupt an almost monotonic cooling of the EEP during the Plio-Pleistocene. SST and productivity in the eastern tropical Pacific varied in phase with global ice volume changes at a dominant 41,000-year (obliquity) frequency throughout this time. Changes in the Southern Hemisphere most likely modulated most of the changes observed. 相似文献
18.
Hendy EJ Gagan MK Alibert CA McCulloch MT Lough JM Isdale PJ 《Science (New York, N.Y.)》2002,295(5559):1511-1514
A 420-year history of strontium/calcium, uranium/calcium, and oxygen isotope ratios in eight coral cores from the Great Barrier Reef, Australia, indicates that sea surface temperature and salinity were higher in the 18th century than in the 20th century. An abrupt freshening after 1870 occurred simultaneously throughout the southwestern Pacific, coinciding with cooling tropical temperatures. Higher salinities between 1565 and 1870 are best explained by a combination of advection and wind-induced evaporation resulting from a strong latitudinal temperature gradient and intensified circulation. The global Little Ice Age glacial expansion may have been driven, in part, by greater poleward transport of water vapor from the tropical Pacific. 相似文献
19.
2010年10月海南一次持续性暴雨的特点和成因分析 总被引：1，自引：0，他引：1
使用常规气象资料、NCEP／GFS资料、高空和地面探测及卫星云图等资料对2010年9月30日20时至10月9日20时海南持续性暴雨的特点和可能成因进行分析．结果表明：200hPa对流层顶南亚高压持续控制海南、南海及中南半岛上空．南海热带低压系统和3个反气旋环流（即大陆冷高压、西太平洋副热带高压和赤道反气旋）对峙为此次暴雨提供有利的环流背景：冷空气东风回流影响华南西部和中南半岛北部．使低层冷平流侵入热带低压系统致使海南东部出现大暴雨到特大暴雨：低空偏东急流、东南急流与西南急流是此次暴雨主要的水汽输送通道．3股急流在海南东部及东北部汇合给当地持续强降水提供了有力的水汽条件：高空形势预报∞方程涡度平流和假相当位温平流的差动项为热带低压系统的发展和维持提供动力和热力强迫作用致使热带低压呈东强西弱不对称结构．以及海南东半部降水强于西部的分布不均的特征。 相似文献
20.
应用NCEP再分析资料、常规观测资料及多普勒雷达探测资料,对2011年6月25～27日台风"米雷"影响威海期间的环流形势、暴雨形成的水汽和动力热力条件及其他相关要素场进行了综合分析。结果表明,此次的强降水及大风是由强热带风暴北上直接影响山东半岛地区造成的;强降水的水汽主要来自"米雷"东部和北部以及副高边缘的低空急流;东北高压同副高合并加强,对阻挡"米雷"东移,引导其北上起重要作用;由于此次过程没有伴随明显的冷空气入侵,整个降水过程主要以层状云降水为主,并未产生较强的对流活动;"米雷"中心靠近时存在风速减弱的"台风眼效应"。 相似文献