On the recent warming of the southeastern Bering Sea shelf   总被引：1，自引：0，他引：1  

P.J. Stabeno  N.A. Bond  S.A. Salo 《Deep Sea Research Part II: Topical Studies in Oceanography》2007,54(23-26):2599

During the last decade, the southeastern Bering Sea shelf has undergone a warming of 3 °C that is closely associated with a marked decrease of sea ice over the area. This shift in the physical environment of the shelf can be attributed to a combination of mechanisms, including the presence over the eastern Bering Sea shelf of a relatively mild air mass during the winter, especially from 2000 to 2005; a shorter ice season caused by a later fall transition and/or an earlier spring transition; increased flow through Unimak Pass during winter, which introduces warm Gulf of Alaska water onto the southeastern shelf; and the feedback mechanism whereby warmer ocean temperatures during the summer delay the southward advection of sea ice during winter. While the relative importance of these four mechanisms is difficult to quantify, it is evident that for sea ice to form, cold arctic winds must cool the water column. Sea ice is then formed in the polynyas during periods of cold north winds, and this ice is advected southward over the eastern shelf. The other three mechanisms can modify ice formation and melt, and hence its extent. In combination, these four mechanisms have served to temporally and spatially limit ice during the 5-year period (2001–2005). Warming of the eastern Bering Sea shelf could have profound influences on the ecosystem of the Bering Sea—from modification of the timing of the spring phytoplankton bloom to the northward advance of subarctic species and the northward retreat of arctic species.  相似文献   

Mineral Geochemical Compositions of Tourmalines and Their Significance in the Gejiu Tin Polymetallic Deposits, Yunnan, China   总被引：4，自引：0，他引：4  

JIA Runxing  FANG Weixuan  and HU Ruizhong 《《地质学报》英文版》2010,84(1):155-166

Abstract: The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines from the deposits. The results indicate a systematic change of mineral geochemical compositions, which might be used as a mineral geochemical tracer for post-magmatic hydrothermal fluid, basin fluid and their mixture. The tourmalines from granite are schorl with Fe/(Fe+Mg) ratios of 0.912-1.00 and Na/(Na+Ca) ratios of 0.892-0.981. Tourmalines as an inclusion in quartz from the ore bodies are dravite with Fe/(Fe+Mg) ratios of 0.212-0.519 and Na/ (Na+Ca) ratios of 0.786-0.997. Tourmalines from the country rocks are dravite with Fe/(Fe+Mg) ratios of 0.313-0.337 and Na/(Na+Ca) ratio of 0.599-0.723. Tourmalines from cassiterite-tourmaline veins that occur in crannies within the country rocks show distinct optical zoning with alternate occurrence of dravite and schorl, Fe/(Fe+Mg)=0.374-0.843, Na/(Na+Ca)=0.538-0.987. It suggests that schorl in granite and dravite in carbonatite are related to magmatic fluid and basin fluid respectively. When magmatic fluid rose up and entered into crannies of the country rocks, consisting mainly of carbonatite, basin fluid would be constantly added to the magmatic fluid. The two types of fluid were mixed in structural crannies of the sedimentary basin accompanied with periodic geochemical oscillations to form material records in chemical composition zonings of tourmalines.  相似文献   

Comparison of coupled and uncoupled models in simulating Monsoon Intraseasonal Oscillation from CMIP6     

Baosheng Li  Dake Chen  Tao Lian  Jianhuang Qin 《海洋学报(英文版)》2022,41(10):100-108

The monsoon intraseasonal oscillation (MISO) is the dominant variability over the Indian Ocean during the Indian summer monsoon (ISM) season and is characterized by pronounced northward propagation. Previous studies have shown that general circulation models (GCMs) still have difficulty in simulating the northward-propagating MISO, and that the role of air-sea interaction in MISO is unclear. In this study, 14 atmosphere-ocean coupled GCMs (CGCMs) and the corresponding atmosphere-only GCMs (AGCMs) are selected from Phase 6 of the Coupled Model Intercomparison Project (CMIP6) to assess their performance in reproducing MISO and the associated vortex tilting mechanism. The results show that both CGCMs and AGCMs are able to well simulate the significant relationship between MISO and vortex tilting. However, 80% of CGCMs show better simulation skills for MISO than AGCMs in CMIP6. In AGCMs, the poor model fidelity in MISO is due to the failure simulation of vortex tilting. Moreover, it is found that failure to simulate the downward motion to the north of convection is responsible for the poor simulation of vortex tilting in AGCMs. In addition, it is observed that there is a significant relationship between the simulated sea surface temperature gradient and simulated vertical velocity shear in the meridional direction. These findings indicate that air-sea interaction may play a vital role in simulating vertical motions in tilting and MISO processes. This work offers us a specific target to improve the MISO simulation and further studies are needed to elucidate the physical processes of this air-sea interaction coupling with vortex tilting.  相似文献   

气候变化对海洋鱼类群落结构的影响研究进展     

李淼  许友伟  孙铭帅  张俊  李佳俊  陈作志  张魁 《海洋科学》2022,46(7):120-129

全球气候变化影响着海洋生态系统的多个方面,而鱼类群落结构对气候变化的响应机制是探索海洋生态系统演变规律的关键点之一。本文结合国内外相关研究成果,概述了气候变化引起的温度、盐度、CO₂浓度、海平面高度、溶解氧以及海流等的改变对鱼类群落结构的影响,并以太平洋十年涛动(Pacific Decadal Oscillation,PDO)和厄尔尼诺−南方涛动(El Niño Southern Oscillation,ENSO)等典型气候现象为例,探讨了鱼类群落对典型气候现象的响应,讨论了需要解决的重点问题,以期为科学应对气候变化和制定海洋生物多样性保护策略提供依据。  相似文献   

陕西降水季节及季节内振荡的气候特征     

黄少妮  许新田  王丹 《干旱气象》2014,(1):46-51

利用谐波分析、功率谱分析的方法,对陕西82个站点1962~2006年逐日降水资料进行气候平均分析,研究气候平均态下陕西降水季节及季节内振荡的时空分布特征。结果表明,陕西大部分地区降水主要以季节变化(年循环)为主,降水准双周振荡在全省范围都比较显著,降水30~60 d季节内振荡的显著分布区域主要集中在关中和陕南,这种地域分布与副热带高压随东亚夏季风南北移动有很大关系;气候平均态下降水的准双周振荡幅度于4月中旬开始逐渐加强,7~9月振幅最强,10~11月开始逐渐减弱;降水准双周振荡显著时期主要在夏季,而30~60 d季节内振荡在全省全年都存在,夏季比冬季振幅大,陕南和关中地区最大振幅出现在7月初。  相似文献   

江淮流域夏季降水的准两年振荡特征及其关联因子分析          下载免费PDF全文

张璟  智协飞  缪锴  罗晓蔚 《大气科学学报》2014,37(5):541-547

利用1951—2010年我国江淮流域11个测站夏季(6—8月)降水资料和NCAR提供的北半球月平均海平面气压场资料以及相关的西太平洋副高指数资料,采用Morlet小波变换、交叉小波变换及相关分析等方法讨论了降水准两年振荡现象的年际变化规律及其与东亚夏季风、副高的关系。结果表明,准两年振荡分量在江淮地区夏季降水场的年际振荡中十分重要,且经历了由强到弱再到强的变化过程;同时降水与夏季风强度及副高脊线位置的准两年变化均存在较好的同期相关,彼此间的相互影响还体现在年际尺度上,并分别在4 a和1 a时间尺度上有明显的滞后、超前关系。  相似文献   

The Second Decadal Leading Mode of East Asian Summer Monsoon Rainfall          下载免费PDF全文

BAO Qing  YU Pei 《大气和海洋科学快报》2014,(5):417-421

The first decadal leading mode of East Asian summer rainfall （EASR） is characterized by rainfall anomalies along the East Asian subtropical rain belt. This study focuses on the second decadal leading mode （2DLM）, accounting for 17.3% of rainfall decadal vari- ance, as distinct from the other two neighboring modes of EAMR, based on the state-of-the-art in-situ rainfall data. This mode is characterized by a South-China-wet-Huaihe- River-dry pattern, and is dominated by a quasi-30-yr pe- riod. Further analysis reveals the 2DLM corresponds to an enhanced lower-level monsoon jet, an eastward extension of the western North Pacific subtropical high, and a weakened East Asian upper-level westerly jet flow. The Tibetan Plateau surface temperature and Pacific Decadal Oscillation （PDO） are closely linked with the 2DLM. The regressed SST pattern indicates the PDO-like pattern of sea surface temperature anomalies may have a telecon- nection relationship with the 2DLM of EASR.  相似文献   

Decadal modes of sea surface salinity and the water cycle in the tropical Pacific Ocean: The anomalous late 1990s     

《Deep Sea Research Part I: Oceanographic Research Papers》2014

Limitations in sea surface salinity (SSS) observations and timescale separation methods have led to an incomplete picture of the mechanisms of SSS decadal variability in the tropical Pacific Ocean, where the El Niño Southern Oscillation (ENSO) dominates. Little is known regarding the roles of the North Pacific Gyre Oscillation (NPGO) and the Pacific Decadal Oscillation (PDO) in the large-scale SSS variability over the tropical basin. A self-organizing map (SOM) clustering analysis is performed on the intrinsic mode function (IMF) maps, which are decomposed from SSS and other hydrological fields by ensemble empirical mode decomposition (EEMD), to extract their asymmetric features on decadal timescales over the tropical Pacific. For SSS, an anomalous pattern appeared during 1997 to 2004, a period referred to as the anomalous late 1990s, when strong freshening prevailed in large areas over the southwestern basin and moderate salinization occurred in the western equatorial Pacific. During this period, the precipitation and surface currents were simultaneously subjected to anomalous fluctuations: the precipitation dipole and zonal current divergence along the equator coincided with the SSS increase in the far western equatorial Pacific, while the weak zonal current convergence in the southwestern basin and large-scale southward meridional currents tended to induce SSS decreases there. The dominant decadal modes of SSS and sea surface temperature (SST) in the tropical Pacific both resemble the NPGO but occur predominantly during the negative and positive NPGO phases, respectively. The similarities between the NPGO and Central Pacific ENSO (CP-ENSO) in their power spectra and associated spatial patterns in the tropics imply their dynamical links; the correspondence between the NPGO-like patterns during negative (positive) phases and the CP La Niña (CP El Niño) patterns for SSS is also discussed.  相似文献   

The Relationship between the El Nin o/La Nin a Cycle and the Transition Chains of Four Atmospheric OscillationsPart I: The Four Oscillations简     

PENG Jingbei  CHEN Lieting  ZHANG Qingyun 《大气科学进展》2014,31(2):468-479

The first leading modes of the interannual variations in low-level circulation over the North and South Pacific are the Northern Oscillation （NO） and Southern Oscillation （SO）,which are oscillations in sea level pressure anomalies （SLPAs）between the eastern and western Pacific Ocean.The second leading modes are the North Pacific Oscillation （NPO） and the Antarctic Oscillation （AAO）,which reflect oscillations between the subtropics and the high and middle latitudes.The transition chains of these four oscillations were investigated using the National Centers for Environmental Prediction-National Center for Atmospheric Research （NCEP-NCAR） reanalysis data.The general pattern of the transition chain between the NO and NPO was from the negative phase of the NO （NO-） to the positive phase of the NPO （NPO＋）,then from NO＋ to NPO-to NO-.The whole transition chain took about 4-6 years.The general pattern and period of the transition between the SO and AAO were similar to those between the NO and NPO.In addition,the transition chains between the NO and NPO,and the SO and AAO,were almost simultaneous.The transition chains of the four oscillations were found to be closely connected,with the eastward propagations of SLPAs occurring along both sides of the Equator.  相似文献   

The 30–60-day Intraseasonal Oscillations over the Subtropical Western North Pacific during the Summer of 1998简     

LU Riyu  DONG Huilin  SU Qin  Hui DING 《大气科学进展》2014,31(1):1-7

The features of 30-60-day convection oscillations over the subtropical western North Pacific （WNP） were investigated, along with the degree of tropical-subtropical linkage between the oscillations over the WNP during summer 1998. It was found that 30-60-day oscillations were extremely strong in that summer over both the subtropical and tro]~ical WNP, providing a unique opportunity to study the behavior of subtropical oscillations and their relationship to tropical oscillations. Further analyses indicated that 30-60-day oscillations propagate westwards over the subtropical WNP and reach eastern China. In addition, 30-60-day oscillations in the subtropics are affected by those over the South China Sea （SCS） and tropical WNP through two mechanisms： （1） direct propagation from the tropics into the subtropics; and （2） a seesaw pattern between the tropics and subtropics, with the latter being predominant.  相似文献