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1.
A global in situ analysis and a global ocean simulation are used jointly to study interannual to decadal variability of temperature in the Bay of Biscay, from 1965 to 2003. A strong cooling is obtained at all depths until the mid-1970's, followed by a sustained warming over ～30 years. Strong interannual fluctuations are superimposed on this slow evolution. The fluctuations are intensified at the surface and are weakest at ～500 m. A good agreement is found between the observed and simulated temperatures, in terms of mean values, interannual variability and time correlations. Only the decadal trend is significantly underestimated in the simulation. A comparison to satellite sea surface temperature (SST) data over the last 20 years is also presented. The first mode of interannual variability exhibits a quasi-uniform structure and is related to the inverse winter North Atlantic Oscillation (NAO) index. Regarding the vertical structure, most cool and warm anomalies are generated at the surface, with the strongest ones penetrating down to 700 m and lasting up to 5 years. The complete heat budget from 1965 to 2004 is presented, including the contributions of vertical transport, freshwater flux and surface elevation. Interannual anomalies are mainly generated by the surface heat flux, while oceanic transports may become more important at longer time scales. 相似文献
2.
Michael M. Whitney 《Continental Shelf Research》2010,30(3-4):305-318
This study quantitatively characterizes annual, interannual, and decadal variability of Middle Atlantic Bight (MAB) river discharges, MAB surface salinities, Long Island Sound (LIS) surface salinities, and LIS salinity stratification via wavelet analysis. Links among rivers, salinities, and standard climate indices are investigated through correlation analysis of the complete data records and low-pass time series (including periods greater than 1.5 years). All rivers and salinities analyzed have strong annual cycles that are distinguishable from random noise. All records have interannual power, but this variability is indistinguishable from the noise background. Some MAB rivers have significant multi-decadal power (near either 18-year or 26-year periods). Correlations are strong among MAB rivers, salinities at different shelf sections, and salinities at LIS stations. Negative correlations between MAB rivers and surface salinities account for a significant part of the observed variance: up to 29% for shelf salinities and 46% for LIS salinities. Shelf and estuary salinities are positively correlated; accounting for at most 61% of the variance. LIS salinity stratification is positively correlated with river discharge (up to 36% of the variance). Interannual variability exhibits similar statistical relationships with higher correlations. Average annual cycles indicate a 1–2-month sequential lag between peak river discharge, minimum estuary salinity, and minimum shelf salinity. Weak but significant correlations indicate a tendency for high discharge, low LIS salinity, and high LIS stratification to coincide with positive intervals of the North Atlantic Oscillation Index. 相似文献
3.
Hydroclimatology of the Upper Madeira River basin: spatio-temporal variability and trends 总被引：1，自引：0，他引：1
Jorge Molina-Carpio Jhan Carlo Espinoza Philippe Vauchel Josyane Ronchail Beatriz Gutierrez Caloir Jean-Loup Guyot 《水文科学杂志》2017,62(6):911-927
Rising in the Andes, the Madeira River drains the southwestern part of the Amazon basin, which is characterized by high geographical, biological and climatic diversity. This study uses daily records to assess the spatio-temporal runoff variability in the Madeira sub-basins. Results show that inter-annual variability of both discharge and rainfall differs between Andean and lowland tributaries. High-flow discharge variability in the Andean tributaries and the Guaporé River is mostly related to sea surface temperature (SST) in the equatorial Pacific in austral summer, while tropical North Atlantic (TNA) SST modulates rainfall and discharge variability in the lowlands. There also is a downward trend in the low-flow discharge of the lowland tributaries which is not observed in the Andes. Because low-flow discharge values at most lowland stations are negatively related to the SST in the tropical North Atlantic, these trends could be explained by the warming of this ocean since the 1970s.
EDITOR A. CastellarinASSOCIATE EDITOR A. Viglione 相似文献
4.
Quasi-periodic fluctuations in the Greenland–Iceland–Norwegian Seas region in a coupled climate model 总被引：1，自引：1，他引：0
We report an analysis of the mechanisms responsible for interannual variability in the Greenland–Iceland–Norwegian (GIN) Seas
in a control integration of the HadCM3 coupled climate model. Interannual variability in sea surface temperature (SST) and
sea surface salinity (SSS) is dominated by a quasi-periodic ∼7-year signal. Analyses show that the mechanism involves a competition
between convection and advection. Advection carries cold, fresh, Arctic water over warm, salty, Atlantic water, while convection
periodically mixes these two water masses vertically, raising SST. Convection is able to raise SST because of the presence
of a subsurface temperature maximum. The GIN Seas convection in HadCM3 is forced by wind stress anomalies related to the North
Atlantic Oscillation (NAO). The consequent SST anomalies feedback positively to force the atmosphere, resulting in a weak
spectral peak (at ∼7 years) in GIN Seas sea level pressure. Although there is no evidence of a similar oscillation in reality,
key aspects of the simulated mechanism may be relevant to understanding variability in the real GIN Seas. In particular, the
potential for increases in convection to raise SST offers a possible new explanation for increases in SST that occurred between
the 1960s and the late 1980s/early 1990s. These SST increases may have contributed to the observed sea-ice retreat. In addition,
a positive feedback between GIN Seas SST and the atmosphere could contribute to the persistence of the NAO, potentially helping
to explain its red spectrum or recent northeastward shift.
相似文献
| Sonia R. Gamiz-FortisEmail: |
5.
A new algorithm for microwave radiometer remote sensing of sea surface salinity and temperature 总被引：1，自引：0，他引：1
The microwave radiation of the sea surface, which is denoted by the sea surface brightness temperature, is not only related with sea surface salinity (SSS) and temperature (SST), but also influenced by sea surface wind. The errors of wind detected by satellite sensor have significant influences on the accuracy of SSS and SST retrieval. The effects of sea surface wind on sea surface brightness temperature, i.e. △Th,v, and the relations among △Th,v, wind speed, sea surface tempera- ture, sea surface salinity and incidence angle of observation are investigated. Based on the investi- gations, a new algorithm depending on the design of a single radiometer with double polarizations and multi-incidence angles is proposed. The algorithm excludes the influence of sea surface wind on SSS and SST retrieval, and provides a new method for remote sensing of SSS and SST. 相似文献
6.
Nikolaos Skliris Sarantis Sofianos Athanasios Gkanasos Anneta Mantziafou Vasilis Vervatis Panagiotis Axaopoulos Alex Lascaratos 《Ocean Dynamics》2012,62(1):13-30
Twenty-four years of AVHRR-derived sea surface temperature (SST) data (1985–2008) and 35 years of NOCS (V.2) in situ-based
SST data (1973–2008) were used to investigate the decadal scale variability of this parameter in the Mediterranean Sea in
relation to local air–sea interaction and large-scale atmospheric variability. Satellite and in situ-derived data indicate
a strong eastward increasing sea surface warming trend from the early 1990s onwards. The satellite-derived mean annual warming
rate is about 0.037°C year–1 for the whole basin, about 0.026°C year–1 for the western sub-basin and about 0.042°C year–1 for the eastern sub-basin over 1985–2008. NOCS-derived data indicate similar variability but with lower warming trends for
both sub-basins over the same period. The long-term Mediterranean SST spatiotemporal variability is mainly associated with
horizontal heat advection variations and an increasing warming of the Atlantic inflow. Analysis of SST and net heat flux inter-annual
variations indicates a negative correlation, with the long-term SST increase, driving a net air–sea heat flux decrease in
the Mediterranean Sea through a large increase in the latent heat loss. Empirical orthogonal function (EOF) analysis of the
monthly average anomaly satellite-derived time series showed that the first EOF mode is associated with a long-term warming
trend throughout the whole Mediterranean surface and it is highly correlated with both the Eastern Atlantic (EA) pattern and
the Atlantic Multidecadal Oscillation (AMO) index. On the other hand, SST basin-average yearly anomaly and NAO variations
show low and not statistically significant correlations of opposite sign for the eastern (negative correlation) and western
(positive correlation) sub-basins. However, there seems to be a link between NAO and SST decadal-scale variations that is
particularly evidenced in the second EOF mode of SST anomalies. NOCS SST time series show a significant SST rise in the western
basin from 1973 to the late 1980s following a large warming of the inflowing surface Atlantic waters and a long-term increase
of the NAO index, whereas SST slowly increased in the eastern basin. In the early 1990s, there is an abrupt change from a
very high positive to a low NAO phase which coincides with a large change in the SST spatiotemporal variability pattern. This
pronounced variability shift is followed by an acceleration of the warming rate in the Mediterranean Sea and a change in the
direction (from westward to eastward) of its spatial increasing tendency. 相似文献
7.
《Earth and Planetary Science Letters》2006,241(3-4):699-706
A sediment core from the western tropical Atlantic covering the last 21,000 yr has been analysed for centennial scale reconstruction of sea surface temperature (SST) and ice volume-corrected oxygen isotopic composition of sea water (δ18Oivc-sw) using Mg / Ca and δ18O of the shallow dwelling planktonic foraminifer Globigerinoides ruber (white). At a period between 15.5 and 17.5 kyr BP, the Mg / Ca SST and δ18Oivc-sw, a proxy for sea surface salinity (SSS), reveals a warming of around 2.5 °C along with an increase in salinity. A second period of pronounced warming and SSS increase occurred between 11.6 and 13.5 kyr BP. Within age model uncertainties, both warming intervals were synchronous with air temperature increase over Antarctica and ice retreat in the southern South Atlantic and terminated with abrupt centennial scale SSS decrease and slight SST cooling in conjunction with interglacial reactivation of the meridional overturning circulation (MOC). We suggest that during these warm intervals, production of saline and warm water of the North Brazil Current resulted in pronounced heat and salt accumulation, and was associated with warming in the southern Atlantic, southward displacement of the intertropical convergence zone and weakened MOC. At the termination of the Younger Dryas and Heinrich event 1, intensification of cross-equatorial heat and salt transport caused centennial scale cooling and freshening of the western tropical Atlantic surface water. This study shows that the western tropical Atlantic served as a heat and salt reservoir during deglaciation. The sudden release of accumulated heat and salt at the end of Younger Drays and Heinrich event 1 may have contributed to the rapid reinvigoration of the Atlantic MOC. 相似文献
8.
The long-term variability of sea level and surface flows in the Gulf of Mexico (GOM) is studied using global monthly sea level reconstruction (RecSL) for 1900–2015. The study explored the long-term relation between the dynamics of the GOM and inflows/outflows through the Yucatan Channel (YC) and the Florida Straits (FS). The results show a century-long trend of increased mean velocity and variability in the Loop Current (LC); however, no significant upward trend was found in the YC and FS flows, only increased variability. Empirical orthogonal function (EOF) analysis of sea surface height found spatial patterns dominated by variations in the LC and temporal variations on time scales ranging from a few months to multidecadal. The time evolution of each EOF mode of sea level is correlated with the velocity of either the LC, the YC, or the FS or some combination of the different flows. The mean sea level difference between the GOM and the northwestern Caribbean Sea was found to be influenced by the North Atlantic Oscillation (NAO), with unusually high differences during the 1970s when the NAO index was low and the Atlantic Ocean circulation was weak. Extreme peaks in SL difference coincide with the extension of the LC and the seasonal eddy shedding pattern. The observed seasonal cycle in the extension area of the LC as obtained from 20 years of altimeter data is significantly correlated (R = 0.63; confidence level = 98%) with the seasonal YC flow obtained from 116 years of the RecSL data. However, the same LC extension record had lower correlation (R = 0.45; confidence level = 90%) with the observed YC transport obtained from direct moored measurements over ~ 5 years, indicating the need for much longer measurements, since the LC extension and the YC flow are strongly affected by interannual and decadal variations. The study demonstrates the usefulness of even a coarse-resolution reconstruction for studies of regional ocean variability and climate change over longer time scales than current direct observations allow.
相似文献9.
北极海冰的急剧消融在近年来欧亚大陆频发的低温事件中扮演着关键角色.秋季北极海冰的偏少对应着冬季欧亚大陆的低温天气,然而二者的联系在年代际和年际两种时间尺度上存在显著区别.本文运用1979—2012年哈德莱中心第一套海冰覆盖率(HadISST1)、欧洲中心(ERA_Interim)的2m温度、风场、海平面气压场、高度场等资料,分别研究了年代际和年际时间尺度上前期秋季北极海冰与欧亚冬季气温的联系.结果表明,欧亚和北极地区(0°—160°E,15°N—90°N)的冬季气温具有显著的年代际和年际变化.在年代际尺度上,温度异常分布在21世纪初由北极冷-大陆暖转为北极暖-大陆冷.这一年代际转折与前期秋季整个北极地区的海冰年代际减少联系密切.秋季北极全区海冰年代际偏少对应冬季欧亚大陆中高纬地区的高压异常,有利于北大西洋的暖湿气流北上和北极的冷空气南侵,造成北极暖-大陆冷的温度分布;在年际时间尺度上,温度异常分布主要由第一模态的年际变化部分和第二模态组成,且第一模态包含的年际变率信号也存在显著的年代际变化.年际尺度上全区北极海冰对欧亚冬季气温的影响远不及位于北冰洋西南边缘的巴伦支海、喀拉海和拉普捷夫海西部(30°E—120°E,75°N—85°N)的关键区海冰影响显著.关键区内海冰的偏少会引发冬季的北大西洋涛动负位相,导致北大西洋吹往欧亚大陆的暖湿气流减弱和欧亚大陆中高纬地区的气温偏低. 相似文献
10.
Philip Sura 《Ocean Dynamics》2010,60(1):155-170
This paper examines the physics of observed non-Gaussian sea surface temperature (SST) anomaly variability in the Gulf Stream
system in a recently developed stochastic framework. It is first shown from a new high-resolution observational data set that
the Gulf Stream system is very clearly visible as a band of negative skewness all the way from Florida, over Cape Hatteras,
to the central North Atlantic. To get an idea about the detailed non-Gaussian variability along the Gulf Stream, probability
density functions are calculated at several locations. One important observational result of this study is that the non-Gaussian
tails of SST variability in the Gulf Stream system follow a power-law distribution. The study then shows that the observed
non-Gaussianity is consistent with stochastic advection of SST anomalies in an idealized zonal current. In addition, stochastic
advection is compatible with the observed northward eddy heat flux in the Gulf Stream, providing a new dynamical view at the
heat balance in strong currents. 相似文献
11.
12.
Evgeny A. Jadin Ke Wei Yulia A. Zyulyaeva Wen Chen Lin Wang 《Journal of Atmospheric and Solar》2010,72(16):1163-1170
Using the monthly mean NCEP/NCAR reanalysis and NOAA Extended Reconstructed sea surface temperature (SST) datasets, strong correlations between the SST anomalies in the North Pacific and calculated three-dimensional Eliassen–Palm vertical fluxes are indicated in December 1958–1976 and 1992–2006. These correlations between the interannual variations of the SST anomalies and the penetration of planetary waves into the stratosphere are much less during the decadal sub-period 1976–1992 in the positive phase of the Pacific Decadal Oscillation (PDO) and the decadal cold SST anomalies in the North Pacific. Interannual variations of the polar jet in the lower stratosphere in January are strongly associated with SST anomalies in the Aleutian Low region in December for the years with positive PDO index. This sub-period corresponds well with that of the violation of the Holton–Tan relationship between the equatorial Quasi-Beinnial Oscillation (QBO) and the stratospheric circulation in the extra-tropics. It is shown that interannual and interdecadal variations of stratospheric dynamics, including stratospheric warming occurrences in January, depend strongly on changes of the upward propagation of planetary waves from the troposphere to the stratosphere over North Eurasia in preceding December. These findings give evidences of a large impact of the decadal SST variations in the North Pacific on wave activity in early winter due to changes of thermal excitation of planetary waves during distinct decadal periods. Possible causes of the decadal violation of the Holton–Tan relationship, its relation to the PDO and an influence of the 11-year solar cycle on the stratosphere are discussed. 相似文献
13.
年代际预测是近年来气候变化研究的一个迅速发展的新兴热点领域,其首要步骤是进行初始化,目的是为年代际预测提供包含观测变率信息的初值.发展效果好且省时的初始化方法是年代际预测的重大挑战之一,目前国际上主流的初始化方法是耦合资料同化,即在耦合模式框架下进行同化.在年代际预测时,由于模式偏差和初始化方法性能的限制会产生初始冲击问题.目前国际上的各模式机构普遍对北大西洋、热带东西太平洋和印度洋海表温度的年代际预测水平高,而对全球平均近地面气温和北太平洋海表温度的年代际预测水平相对较差.本文主要从初始化方法和年代际预测这两方面的研究现状进行全面回顾,指出存在的问题并讨论未来的发展趋势和挑战. 相似文献
14.
Long-term variability of heat content (HC) in the upper 1,000 m of the Arctic Ocean is investigated using surface and subsurface
temperature and current data during 1958–2005 compiled by Simple Ocean Data Assimilation. Annual cycle of the Arctic Ocean
HC is controlled primarily by the negative and positive excursions in net upper ocean heat flux, while the inter-annual variability
is mainly associated with meridional thermal advection from the North Atlantic Ocean. Variability in HC is experienced as
a basin-wide cooling/warming in association with the Arctic Oscillation on a decadal time scale. In the first three dominant
modes of Empirical Orthogonal Function, the maximum amplitude of HC variability occurs in the Greenland–Norwegian Sea and
Eurasian Basin. In general, HC showed increasing trend during 1958–2005 indicating continuous warming with regional variations
in magnitude. 相似文献
15.
Interannual variability of Gulf Stream warm-core rings in response to the North Atlantic Oscillation
Analysis of a quality-controlled database of Gulf Stream warm-core rings (WCRs) between 75° and 50°W during 1978–1999 demonstrates a significant correlation between WCR occurrences and variations in large-scale atmospheric forcing related to the state of the North Atlantic Oscillation (NAO). The mechanisms for linking the NAO with the rate of WCR occurrences are two-fold: (1) the influence of the NAO on Gulf Stream (GS) position, which could affect the interaction of the Gulf Stream with the New England Seamounts chain and thus allow for a higher/lower number of WCR occurrences; (2) the NAO-induced eddy kinetic energy (EKE) variability in the Gulf Stream region (GSR), which is indicative of the baroclinic instability processes necessary for WCR formation. Variability in GS movement is studied by analyzing annual mean positions of the Gulf Stream North Wall obtained from satellite-derived sea surface temperature (SST) frontal charts. Response of GSR EKE to fluctuations in the state of the NAO is examined with a numerical simulation of the North Atlantic basin from 1980–1999. The North Atlantic basin is simulated using a 1/6°-resolution eddy-resolving Regional Ocean Modeling System (ROMS) model that spins up with Southampton Oceanography Center (SOC) ocean-atmosphere atlas-derived atmospheric forcing fields. Model-derived EKE estimates are observed to be in good agreement with TOPEX/Poseidon altimeter-based EKE estimates as well as with results from other modeling studies for the North Atlantic basin. We suggest that lateral movement of the GS may not be the primary mechanism causing variation in the rate of WCR occurrences, because GS position is observed to respond at a lag of one year, whereas annual rates of WCR occurrences respond at 0-year lag to the NAO. Based on results from numerical simulations of the North Atlantic basin, adjustment to NAO-induced wind forcing is seen to impact the GSR EKE intensity and possibly the related baroclinic instability structure of the GS at 0-year lag. These results suggest that NAO-induced interannual variability in GSR EKE is the most likely mechanism affecting WCR occurrences. Numerical simulations show that high (low) phases in the state of the NAO exhibit higher (lower) EKE in the GSR, providing a greater (lesser) source of baroclinic instability to the GS front, possibly resulting in higher (lower) occurrences of WCRs. 相似文献
16.
The inter-annual variability of the sea surface temperature (SST) was analyzed along the western Iberian Peninsula in the region ranging from 9.5 °W to 21.5 °W and from 37.5 °N to 42.5 °N with a spatial resolution of 1°×1° from 1900 to 2008. Both coastal and oceanic SST showed an overall increase with warming and cooling cycles similar to those observed in the North Atlantic region and in previous regional studies. In addition, the evolution of coastal and ocean water has been observed to be different. In general, ocean water is more affected by the different warming–cooling cycles than coastal water. In spite of coast and ocean are highly influenced by global changes affecting the whole North Atlantic region, near shore SST has been observed to be correlated with local wind regime, which is itself a manifestation of the Eastern Atlantic (EA) teleconnection pattern. 相似文献
17.
Based on Argo sea surface salinity(SSS) and the related precipitation(P), evaporation(E), and sea surface height data sets, the climatological annual mean and low-frequency variability in SSS in the global ocean and their relationship with ocean circulation and climate change were analyzed. Meanwhile, together with previous studies, a brief retrospect and prospect of seawater salinity were given in this work. Freshwater flux(E-P) dominated the mean pattern of SSS, while the dynamics of ocean circulation modulated the spatial structure and low-frequency variability in SSS in most regions. Under global warming, the trend in SSS indicated the intensification of the global hydrological cycle, and featured a decreasing trend at low and high latitudes and an increasing trend in subtropical regions. In the most recent two decades, global warming has slowed down, which is called the"global warming hiatus". The trend in SSS during this phase, which was different to that under global warming, mainly indicated the response of the ocean surface to the decadal and multi-decadal variability in the climate system, referring to the intensification of the Walker Circulation. The significant contrast of SSS trends between the western Pacific and the southeastern Indian Ocean suggested the importance of oceanic dynamics in the cross-basin interaction in recent decades. Ocean Rossby waves and the Indonesian Throughflow contributed to the freshening trend in SSS in the southeastern Indian Ocean, while the increasing trend in the southeastern Pacific and the decreasing trend in the northern Atlantic implied a long-term linear trend under global warming. In the future, higher resolution SSS data observed by satellites, together with Argo observations, will help to extend our knowledge on the dynamics of mesoscale eddies, regional oceanography, and climate change. 相似文献
18.
Eight years of AVHRR-derived sea surface temperature (SST) and SeaWiFS-derived surface chlorophyll (Chl) data (1998–2005) are used to investigate key processes affecting the spatial and temporal variability of the two parameters in the Aegean Sea. Seasonal mean SST and Chl maps are constructed using daily data to study seasonal dynamics whereas empirical orthogonal function (EOF) and correlational analysis is applied to the 8-day composite SST and Chl anomaly time-series in order to study the variability and co-variability of the two parameters from subseasonal to interannual time-scales. The seasonal mean fields show that Black Sea cold and chlorophyll-rich waters enter through the Dardanelles Strait and they are accumulated in the north-eastern part of the Aegean Sea, steered by the Samothraki anticyclone. Large chlorophyll concentrations are encountered in the hydrological front off the Dardanelles Strait as well as in coastal areas affected by large riverine/anthropogenic nutrient loads. The SST seasonal mean patterns reveal strong cooling that is associated with upwelling along the eastern boundary of the basin during summer due to strong northerly winds, a process which is not present in the surface chlorophyll climatology. The Chl dataset presents much stronger sub-seasonal variability than SST, with large variations in the phase and strength of the phytoplankton seasonal cycles. EOF analysis of the anomaly time-series shows that SST non-seasonal variability is controlled by synoptic weather variations and anomalies in the north–south wind-stress component regulating the summer coastal upwelling regime. Mean SST and Chl patterns, and their associated variations, are not closely linked implying that Black Sea and riverine inputs mainly control the intra-annual and interannual variability of the surface chlorophyll in the Aegean Sea rather than mixing and/or upwelling processes. 相似文献
19.
The Bay of Biscay is part of the North Atlantic Ocean, the most important sink of CO2, and a subduction zone of mode waters that favours the entry of carbon to the ocean interior. To investigate the seasonal and interannual variability of CO2 uptake, continuous underway measurements of the partial pressure of CO2 at sea surface were performed along a commercial route between Vigo (Spain) and St. Nazaire (France). An unattended measuring system of CO2 fugacity (fCO2), with meteorological station, and temperature, salinity, oxygen and fluorescence sensors, was installed on board of ships of opportunity (RO-RO L’Audace and RO-RO Surprise). 相似文献
20.
利用NCEP/NCAR再分析风场资料和NOAA海表温度(SST)资料,分析了冬、夏季Hadley环流的变化特征及其与热带海温在年际、年代际尺度上的关系. 结果表明,冬季北半球Hadley环流强度具有明显的年际和年代际变化,同时还呈现出明显的增强趋势. 伴随着Hadley环流的加强,环流中心位置南移,高度上升;夏季南半球Hadley环流变化主要表现为强、弱、强的年代际振动,没有明显的线性趋势. 研究还显示冬季Hadley环流与Nino3区SST正相关,这种相关性具有年代际变化特征. 年际尺度上,冬季北半球Hadley环流与Nino3区SST正相关;夏季南半球Hadley环流与Nino3区SST负相关,即当赤道中东太平洋SST异常偏暖(冷)时,冬、夏季Hadley环流变强(弱). 相似文献