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1.
Relations in year-to-year variability between wintertime Sea-Ice Concentrations (SICs) in the Okhotsk Sea and atmospheric anomalies consisting of zonal and meridional 1000-hPa wind speeds and 850-hPa air temperatures are studied using a singular value decomposition analysis. It is revealed that the late autumn (October–November) atmospheric conditions strongly influence sea-ice variability from the same season (late autumn) through late winter (February—March), in which sea-ice extent is at its maximum. The autumn atmospheric conditions for the positive sea-ice anomalies exhibit cold air temperature anomalies over the Okhotsk Sea and wind anomalies blowing into the Okhotsk Sea from Siberia. These atmospheric conditions yield anomalous ocean-to-atmosphere heat fluxes and cold sea surface temperature anomalies in the Okhotsk Sea. Hence, these results suggest that the atmospheric conditions affect the sea-ice through heat anomalies stored in sea-ice and oceanic fields. The late autumn atmosphere conditions are related to large 700-hPa geopotential height anomalies over the Bering Sea and northern Eurasia, which are related to a stationary Rossby wave propagation over the North Pacific and that from the North Atlantic to Eurasia, respectively. In addition, the late autumn atmospheric preconditioning also plays an important role in the decreasing trend in the Okhotsk sea-ice extent observed from 1980 to the mid-1990s. Based on the lagged sea-ice response to the late autumn atmosphere, a simple seasonal prediction scheme is proposed for the February–March sea-ice extent using four-month leading atmospheric conditions. This scheme explains 45% of the variance of the Okhotsk sea-ice extent.  相似文献   

2.
The cold bottom water, formed in the previous winter on the eastern Bering Sea shelf, remains throughout the summer. in order to examine the mechanism for the formation of the cold bottom water, we used minimum water temperature in the cold bottom water observed over the eastern Bering Sea shelf for 30 years. The interannual variation in the minimum water temperature of the cold bottom water was closely related to that of mean air temperature during cooling period at St. Paul Island. The air temperature in previous winter primarily affects the cold bottom water. We estimated decrement of the water temperature due to ice melting with simple box model. It was found with the box model that decreasing of the water temperature and lowering of the salinity depend on ice melting. To investigate the cause of interannual variation in air temperature in winter, we applied EOF analysis to the 500 hPa height. The Pacific/North American pattern (PNA) was related to mean air temperature at St. Paul Island in cooling season and the cold bottom water temperature. These results suggest the connection between ENSO events and warming or cooling in the Bering Sea shelf in winter.  相似文献   

3.
通过海气耦合模式CCSM3(The Community Climate System Model version 3),研究在北大西洋高纬度淡水强迫下,北太平洋冬季的海表温度SST、风场及流场的响应及其区域性差异。结果表明:淡水的注入使北太平洋整体变冷,但有部分区域异常增暖;在太平洋东部赤道两侧,SST的变化出现北负南正的偶极子型分布。阿留申低压北移的同时中纬度西风减弱,热带附近东北信风增强。黑潮和南赤道流减弱,北太平洋副热带逆流和北赤道流增强,日本海被南向流控制。风场及流场的改变共同导致了北太平洋SST异常出现复杂的空间差异:北太平洋中高纬度SST的降温主要由大气过程决定,海洋动力过程主要影响黑潮、日本海及副热带逆流区域的SST,太平洋热带地区SST异常由大气与海洋共同主导。  相似文献   

4.
The paper presents the records of several paleoproductivity proxies (PP) (biogenic opal and Ba (Si_bio, Ba_bio), organic carbon (C_org) and carbonate Ca_carb, chlorin and benthic foraminifera abundance (BFA)) in sediments of the Okhotsk Sea for the last 80 kyr with a resolution of ∼100–300 years. The sediment age model was based on the AMS 14C data, records of benthic foraminifera δ18O, paleointensity of the Earth’s geomagnetic field and magnetic susceptibility. PP values demonstrate series of severe prolonged productivity drops in the Okhotsk Sea followed by a sharp increase during the last glaciation. On the basis of quantitative estimations of the paleoproductivity in the Okhotsk Sea during the cold MIS 2 and warm Holocene (Gorbarenko and Goldberg, 2005), it is suggested that the millennium scale relationship in productivity-climate changes of this basin was similar: an increase in the sea’s productivity was related with regional climate warming and vice-versa. The PP records of productivity/climate oscillations in the Okhotsk Sea during MIS 2–4 occurred contemporaneously with the North Atlantic cold Heinrich events (HE) and Greenland Dansgaard-Oyeshger interstadial (DOI). Observed successions of prolonged climate cooling events followed by rapid, abrupt warming are similar to climate and environmental oscillations in the N. Atlantic and Greenland, that confirms the millennium-scale climate changes synchronicities in the Northern Hemisphere including the far NW Pacific, the hydrology and climate conditions of which are close to those of the Okhotsk Sea. Synchronism of the N. Hemisphere severe cooling (including the Okhotsk Sea) with the Antarctic warming suggests that mechanisms of the “seesaw” effect (Blunier and Brook, 2001) in the low latitude heat redistribution between high latitudes of both hemispheres were more complicated than direct NADW formation forcing and encompasses the global atmospheric reorganization. Within the PP used a closer connection in the Okhotsk Sea millennium oscillations was observed for the C_org, BFA and chlorin; Ba_bio increases more closely to DOI. Si_bio variability does not show any evident correlation with productivity changes.  相似文献   

5.
杨颖玥  刘海龙 《海洋与湖沼》2023,54(6):1564-1572
卫星记录以来,南极海冰范围发生5次快速下降事件,研究这5次事件的时空特征,对进一步认识海冰快速下降事件的物理机制具有重要意义。基于海冰范围和海冰密集度的卫星数据,从时间和空间两个维度总结5次南极海冰快速下降事件的特征,再结合大气和海洋各项环境因素的再分析数据,探讨海冰快速下降的影响因素及其驱动过程。结果显示:南极海冰快速下降的空间分布存在季节性差异, 2021年8～12月以及2016年8～12月的春季南极海冰快速下降由别林斯高晋海、威德尔海、印度洋和西太平洋区域的海冰减少所主导; 2010年12月至2011年4月以及1985年12月至1986年4月的夏季南极海冰快速下降由威德尔海、罗斯海沿岸和西太平洋区域的海冰减少所主导;2008年4～8月的冬季南极海冰快速下降则由别林斯高晋海和西太平洋的部分区域的海冰减少所主导。探究影响海冰的环境因素发现,海表面温度和海表面净热通量对海冰减少的热力效应影响具有区域性差异。此外,南极海冰快速下降受阿蒙森低压的影响,相应的海表面风异常既通过经向热输运的热力效应导致海冰减少,也通过风的动力效应驱动海冰漂移使得海冰密集度降低。  相似文献   

6.
通过谐波分析的方法,对东亚31个冬季(1980—2010年)的气温提取年际变化分量(周期小于8a部分)进行EOF分析。结果发现:在年际变化的时间尺度上,东亚冬季气温表现为高纬模态和低纬模态2个主要模态,它们一起可以解释总方差73%的变化。进一步分析表明,在年际变化尺度上,与气温变化的高纬模态相联系的大气环流表现为显著的北极涛动(AO)负位相分布,海平面气压场上西伯利亚高压和阿留申低压北移,对流层中层东亚大槽西移,高层西风急流向西北方向移动;副热带北太平洋和阿拉斯加湾的海表面温度(SST)变化呈偶极子振荡分布,这种准两年的周期振荡对这一模态的出现有一定的预示意义。而与气温变化的低纬模态相联系的大气环流表现为类AO正位相分布,与之相关的西伯利亚高压和阿留申低压南移,对流层中层东亚大槽东移,高层的西风急流则是向东南方向移动;赤道东太平洋的SST异常可能对这一模态的形成有一定的作用,而东亚近海的SST则更多是被动地改变。此外,海冰异常变化与东亚冬季气温变化的联系主要体现在:在前夏和前秋,东西伯利亚海-波弗特海海冰异常减少(增加)对应着随后东亚冬季气温变化的高纬模态(低纬模态),而冬季东亚气温变化的高纬模态(低纬模态)又与后期春季北极东半球的海冰异常增加(减少)具有较好的相关性,此外白令海和鄂霍次克海的海冰异常变化是伴随东亚冬季气温变化产生的。  相似文献   

7.
A comparative analysis was conducted on climate variability in four sub-arctic seas: the Sea of Okhotsk, the Bering Sea shelf, the Labrador Sea, and the Barents Sea. Based on data from the NCEP/NCAR reanalysis, the focus was on air–sea interactions, which influence ice cover, ocean currents, mixing, and stratification on sub-seasonal to decadal time scales. The seasonal cycles of the area-weighted averages of sea-level pressure (SLP), surface air temperature (SAT) and heat fluxes show remarkable similarity among the four sub-arctic seas. With respect to variation in climate, all four seas experience changes of comparable magnitude on interannual to interdecadal time scales, but with different timing. Since 2000 warm SAT anomalies were found during most of the year in three of the four sub-arctic seas, with the exception of the Sea of Okhotsk. A seesaw (out of phase) pattern in winter SAT anomalies between the Labrador and the Barents Sea in the Atlantic sector is observed during the past 50 years before 2000; a similar type of co-variability between the Sea of Okhotsk and the Bering Sea shelf in the Pacific is only evident since 1970s. Recent positive anomalies of net heat flux are more prominent in winter and spring in the Pacific sectors, and in summer in the Atlantic sectors. There is a reduced magnitude in wind mixing in the Sea of Okhotsk since 1980, in the Barents Sea since 2000, and in early spring/late winter in the Bering Sea shelf since 1995. Reduced sea-ice areas are seen over three out of four (except the Sea of Okhotsk) sub-arctic seas in recent decades, particularly after 2000 based on combined in situ and satellite observations (HadISST). This analysis provides context for the pan-regional synthesis of the linkages between climate and marine ecosystems.  相似文献   

8.
We survey the recent progress in studies of North Pacific Intermediate Water (NPIW) in SAGE (SubArctic Gyre Experiment), including important results obtained from related projects. Intensive observations have provided the transport distributions relating to NPIW and revealed the existence of the cross-wind-driven gyre Oyashio water transport that flows directly from the subarctic to subtropical gyres through the western boundary current as well as the diffusive contribution across the subarctic front. The anthropogenic CO2 transport into NPIW has been estimated. The northern part of NPIW in the Transition Domain east of Japan is transported to the Gulf of Alaska, feeding the mesothermal (intermediate temperature maximum) structure in the North Pacific subarctic region where deep convection is restricted by the strong halocline maintained by the warm and salty water transport originating from NPIW. This heat and salt transport is mostly balanced by the cooling and freshening in the formation of dense shelf water accompanied by sea-ice formation and convection in the Okhotsk Sea. Intensive observational and modeling studies have substantially altered our view of the intermediate-depth circulation in the North Pacific. NPIW circulations are related to diapycnal-meridional overturning, generated around the Okhotsk Sea due to tide-induced diapycnal mixing and dense shelf water formation accompanied by sea-ice formation in the Okhotsk Sea. This overturning circulation may possibly explain the direct cross-gyre transport through the Oyashio along the western boundary from the subarctic to subtropical gyres. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

9.
Processes relating to the formation of dense shelf water and intermediate water in the Okhotsk Sea were studied by examining oxygen isotope ratios (δ18O), salinity, and temperature. The salinity and δ18O of the cold dense shelf water on the northern continental shelf showed peculiar relationship. The relationship indicates that 3% of the mixed-layer water, having salinity of 32.6, froze and the remaining 97% became dense shelf water of salinities of more than 33.2 (σθ>26.7) during the sea ice formation. The salinity–δ18O relationship also shows that 20% of the Okhotsk Sea Intermediate Water at the σθ=26.8 level was derived from the dense shelf water. The remaining 80% came from the Western Subarctic Pacific water modified by diapycnal mixing of water affected by the surface cooling and freshening within the Okhotsk Sea. The mixing with dense shelf water contributes to only 26% of the temperature difference or 8% of the salinity difference between the original Pacific water and the Okhotsk Sea Intermediate Water at σθ=26.8. This result suggests that the cold and less saline properties of the Okhotsk Sea Intermediate Water are produced mainly by diapycnal mixing, rather than by mixing of the Pacific water with the dense shelf water.  相似文献   

10.
根据渤海6个海洋站的海冰监测及气温观测数据统计,终冰日及冰期可用来表征当年渤海冰情严重程度,在大多数年份冰情与终冰日早晚和冰期长短呈负相关。根据2006/2016年的辽东湾海冰面积及外缘线资料,分析了11年间辽东湾冰情的年变化特征,分析结果显示,辽东湾海冰受局地气温影响明显,两者呈较显著的负相关关系。分析结果发现,辽东湾海冰年际变化除受局地气候的影响外,还受太平洋副热带高压(简称副高)、极涡、东亚槽和欧亚环流等气候因子的共同调控,其中受太平洋副高北界位置指数、极涡面积指数、东亚槽强度指数、欧亚纬向环流指数影响最为显著,可作为辽东湾海冰预测的重要因子,此外北极海冰密集度也可以为预测当年冬季辽东湾每月冰情提供依据。  相似文献   

11.
20世纪90年代后期南海上层海温变化趋势的转折   总被引：1，自引：1，他引：0  
In this paper, the interdecadal variability of upper-ocean temperature in the South China Sea(SCS) is investigated based on several objectively analyzed data sets and two reanalysis data sets. The trends of the SCS sea surface temperature(SST) have changed from warming to cooling since the late 1990 s. A heat budget analysis suggests that the warming of the surface mixed layer during 1984–1999 is primarily attributed to the horizontal heat advection and the decrease of upward long wave radiation, with the net surface heat flux playing a damping role due to the increase of upward latent and sensible heat fluxes. On the other hand, the cooling of the surface mixed layer during 2000–2009 is broadly controlled by net surface heat flux, with the radiation flux playing the dominant role. A possible mechanism is explored that the variation of a sea level pressure(SLP) over the North Pacific Ocean may change the prevailing winds over the SCS, which contributes to the change of the SST in the SCS through the horizontal heat advection and heat fluxes.  相似文献   

12.
In the southwestern part of the Okhotsk Sea, oceanographic and sea-ice observations on board the icebreaker Soya were carried out in February 1997. A mixed layer of uniform temperature nearly at the freezing point extending down to a depth of about 300 m was observed. This is much deeper than has previously been reported. It is suggested that this deep mixed layer originated from the north (off East Sakhalin), being advected along the shelf slope via the East Sakhalin Current, accompanied with the thick first-year ice (average thickness 0.6 m). This vertically uniform winter water, through mixing with the surrounding water, makes the surface water more saline (losing a characteristic of East Sakhalin Current Water) and the water in the 100–300 m depth zone less saline, colder, and richer in oxygen (a characteristic of the intermediate Okhotsk Sea water). The oceanographic structure and a heat budget analysis suggest that new ice zone, which often appears at ice edges, can be formed through preconditioning of thick ice advection and subsequent cooling by the latent heat release due to its melting. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

13.
The objective of this research is to describe physical processes which are the cause of the recent variability of the Pacific western subarctic waters. Rapid thermohaline changes have occurred within the Oyashio and Kamchatka Current during the last decade. This variability has included a warming of the Kamchatka Current warm intermediate layer, but a cooling and freshening of the upper layer in the Oyashio and Sea of Okhotsk. The example presented here uses data obtained during the Canada/Russia INPOC and WOCE projects, as well as the new Russian studies with high resolution station grid.The possible physical mechanism that generated the upper layer freshening during the thermohaline transition is examined. Major components of the fresh water budget of the Okhotsk Sea are considered in order to describe the dramatic changes in salinity which have recently occurred in the Pacific subarctic. Significant changes in precipitation and other fresh water inputs are demonstrated. It is suggested that upper layer of the Oyashio and Kamchatka Current became cooler and fresher because of the export of cold, fresher waters from the Bering and Okhotsk seas. These waters from the marginal seas have cooled the bottom of the halocline, reducing evaporation and acting as a feedback that has kept the upper layer of the western subarctic boundary currents fresh. It is also shown that the outflow of the cold Sea of Okhotsk water has changed its path during this recent thermohaline transition.  相似文献   

14.
The sea-surface bioproductivity changes over the last 25 kyr were inferred from published data on 30 sediment cores from the open Northwest Pacific (NWP), Sea of Okhotsk, Bering Sea and Sea of Japan accounting for the glacioeustatic sea-level changes. A novel method was developed to compare the variations of several independent productivity proxies relative to the present-day values. During the Last Glacial Maximum, the bioproductivity in the Sea of Okhotsk and the western Bering Sea (BS) was lower than at present, whereas the southern and southeastern Bering Sea and the open NWP are characterized by enhanced bioproductivity. During the early deglacial stage, an increase in bioproductivity was estimated only for the southeastern Bering Sea. High and fairly high bioproductivity was estimated for Heinrich 1 in the open NWP, above the Umnak Plateau and on the Shirshov and Bowers Ridges in the Bering Sea. The high productivity in the Bering Sea, Sea of Okhotsk and NWP during the Bølling/Allerød was caused by the global warming and enhanced nutrient supply by meltwater from the continent. During the Early Holocene, high productivity was estimated for almost the entire NWP. The Late Holocene sea-surface bioproductivity was generally lower than that of the Early Holocene. Proposed factors that have controlled the sea-surface bioproductivity during the last 25 kyr include: the location of the sea ice margin, the river runoff, gradual flooding of the Bering Sea and the Sea of Okhotsk shelf areas, the water mass exchange between the marginal seas and the open NWP, the eolian supply and the deep vertical mixing of the water column.  相似文献   

15.
日本海、鄂霍次克海和白令海的古海洋学研究进展   总被引：2，自引：0，他引：2  
边缘海的存在使大陆和大洋之间的物质和能量交换变得相当复杂。在构造运动和海平面升降的控制下,边缘海和大洋之间时而连通时而隔绝,各种古气候变化信号都在一定程度上被放大。基于近期有关西北太平洋边缘海的古海洋学研究成果,简要概述了日本海、鄂霍次克海、白令海以及北太平洋地区自中新世以来的古气候和古海洋环境演化特征,并认为它们与全球其它地区一样也受控于因地球轨道参数变化引起的太阳辐射率的变化,大尺度的气候变化具有与地球轨道偏心率周期相对应的100ka周期,而41ka的小尺度周期则受地球自转轴斜率变化的控制。一些突发性的气候变化则是由气候不稳定性、海峡的关闭与开启和其它一些地球气候系统的非线性活动所驱动。但同时作为中高纬度边缘海,它们的古海平面、古海水温度、古洋流等古海洋环境因子的变化特征还受到冰盖扩张和退缩、构造运动、冰川性地壳均衡补偿、东亚季风等因素的影响,具有一定的区域特点。  相似文献   

16.
In January to April, floating ice drifts from the Sea of Okhotsk via the Kuril straits to the northwestern part of the Pacific Ocean. In its turn, ice from the Bering Sea moves southwestward along the eastern coast of the Kamchatka Peninsula. The amount of the ice supplied to the ocean features a significant interannual variability. In this paper, we use the data for the period from 1958 to 2005. During the years with the heaviest ice conditions, floating ice from the Bering Sea moved to the south along Kamchatka Peninsula down the latitude of the Fourth Kuril Strait forming a tongue 30–50 miles wide. The ice drifting from the Sea of Okhotsk to the northwestern part of the Pacific Ocean may move via the passages from the Kunashir to the Kruzenshtern straits and form a band with a width of 30–40 miles depending of the severity of the winter.  相似文献   

17.
北冰洋中心区海冰漂流与大气过程   总被引：3，自引：3，他引：0  
利用北冰洋中心区漂流自动气象站(DAWS)2012年9月—2013年2月的观测数据,分析了北极点周围海冰漂流轨迹和速度及相关大气过程。结果显示,北冰洋中心区海冰具有不稳定漂流过程。2012年9月1日—2013年1月6日,DAWS所在海冰从西向西北方向漂流,2013年1月6日以后稳定地向东南方向漂流,平均移速为0.06m/s,最大达到0.4m/s。海冰漂流方向的突变和加速与穿极气旋和急流的影响有关。净辐射常出现短期突变过程,导致海冰从大气吸收能量,减缓了海冰的辐射冷却。爆发性增温过程的最大幅度达到30℃,是由强穿极气旋和伴随的暖湿气流向北极中心区输送引起,这种现象在中低纬度十分罕见。增温过程的作用是高空大气向冰面输送热量,导致海冰破裂,海冰硬度的脆变,减缓海冰厚度的增长,这种过程可能是北极海冰面积和厚度减少重要过程。  相似文献   

18.
鄂霍次克海南部晚第四纪的古海洋学记录   总被引：1，自引：0，他引：1  
鄂霍次克海是太平洋第二大边缘海,在西北太平洋水文环境中扮演重要角色。综合分析了鄂霍次克海南部T00孔沉积物的多种替代性指标,揭示了鄂霍次克海晚第四纪以来的环境变化受季节性海冰变化、大气循环模式、陆源物质通量和表层生产力的共同影响。对比放射虫Cycladophora davisiana的含量曲线与LR04氧同位素记录,该孔沉积物可划分为氧同位素1-7期,底部年龄约为250ka。C.davisiana在间冰期的高含量表明鄂霍次克海中层水是北太平洋中层水的主要源区。蛋白石和有机碳的分析显示鄂霍次克海表层生产力在冰消期突然增大,随后在间冰期逐渐下降,冰期普遍较低。C/N比值曲线的分析说明鄂霍次克海的有机质沉积物主要来源于海洋。沉积物粒度的分析揭示鄂霍次克海冰期时陆源粗颗粒含量较低,至冰消期粗颗粒含量突然增加,而在间冰期陆源粗颗粒含量较高。  相似文献   

19.
海冰消融背景下北极增温的季节差异及其原因探讨   总被引：7，自引：2，他引：5  
运用哈德莱中心第一套海冰覆盖率(HadISST1)、欧洲中心(ERA_Interim)的温度以及NCEP第一套地表感热通量、潜热通量等资料,研究了1979—2011年33a来北极海冰消融的季节特点和空间特征,并从反照率——温度正反馈与地表感热通量、潜热通量等方面分析了海冰减少对北极增温影响的季节差异。结果表明,北极海冰在秋季和夏季的减少范围明显大于冬季和春季,而北极地表升温却在秋季和冬季最显著,夏季最为微弱,且夏季的增温趋势廓线也与秋冬季显著不同。这主要是因为夏季是融冰季,海冰融化将吸收潜热。且此时北极低空大气温度高于海表温度,海水相当于大气的冷源。随着海冰的消融,更多的热量由大气传入海洋用于融冰和加热上层海水,这使得夏季的低空大气不能显著升温。而在秋冬季,海冰凝结释放潜热,且此时低空大气温度远低于海水温度,海冰的减少使得海水将更多热量释放到大气中导致低空大气显著增暖。海水对大气的这种延迟放热机制是北极低空在夏季增温不显著而在秋冬季增温显著的主要原因。此外,秋冬季的海冰减少与北极近地面升温具有非常一致的空间分布,北冰洋东南边缘和巴伦支海北部分别是秋季和冬季海气相互作用的关键区域。  相似文献   

20.
Okhotsk Sea Intermediate Water (OSIW), the source water for ventilation of North Pacific Intermediate Water, exhibits a multidecadal warming trend. Historical data show that OSIW temperatures increased by 0.28, 0.57, 0.31 and 0.10°C during 1955 to 2003 at potential densities of 26.8, 27.0, 27.2 and 27.4σ θ , at depths of approximately 250, 500, 700 and 900 m, respectively. This rate of warming is much faster than that of the global ocean. This OSIW warming is likely linked to the reduced ventilation of cold Dense Shelf Water associated with brine rejection during sea ice formation.  相似文献   

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