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1.
本文通过对阿蒙森海西北部陆隆AMS01岩心沉积物颜色、粒度及地球化学等多种指标分析，重建了该地区氧同位素9期(MIS9，大约距今34万年)以来冰盖与古生产力演变历史，结果表明:(1)岩心沉积物粒度与古生产力替代指标表现出明显的冰期–间冰期旋回变化特征；(2)MIS9、MIS7和MIS5等间冰期沉积速率较小，沉积物呈褐色，冰筏碎屑含量低，生源组分含量高，反映出该时期阿蒙森海地区气候温暖，冰盖发生了大规模退缩，冰盖–冰架–冰山等陆源冰对沉积物的影响减弱，海冰覆盖减弱，有利于浮游植物的生长和繁殖；(3)MIS8c、MIS8a、MIS6、MIS2等冰期沉积速率大，沉积物呈灰色，沉积物随之变粗，冰筏碎屑含量高，生源组分含量低，说明该时期冰盖大幅扩张，陆隆区成为近冰盖/冰架沉积环境，海冰和冰山密集，海洋生产力显著降低；(4)冰期、间冰期内，冰盖与古生产力也有不同程度的波动；特别是MIS8b期发育浅褐色间冰阶沉积，冰筏碎屑含量低，生产力水平与间冰期基本持平，说明阿蒙森海地区冰盖、海洋对气候变化的响应比东南极地区敏感。  相似文献   

2.
Benthic foraminiferal and sediment biogeochemical data (total organic carbon, calcium carbonate and biogenic opal contents) in two cores (1265 and 1312 m water depths) from the southeastern Sakhalin slope and one core (839 m water depth) from the southwestern Kamchatka slope were investigated to reconstruct variations of the oxygen minimum zone during the last 50 ka in the Okhotsk Sea. The oxygen minimum zone was less pronounced during cooling in the MIS 2 that is suggested to be caused by a maximal expansion of sea ice cover, decrease of marine productivity and increase of production of the oxygenated Okhotsk Sea Intermediate Water (OSIW). A two-step-like strengthening of oxygen minimum zone during the warmings in the Termination 1a and 1b was linked to (1) enhanced oxygen consumption due to degradation of large amount of organic matter in the water column and bottom sediments, originated from increased marine productivity and supply of terrigenous material from the submerged northern shelves; (2) sea ice cover retreat and reduction of OSIW production; (3) freely inflow of the oxygen-depleted intermediate water mass from the North Pacific.  相似文献   

3.
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   

4.
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   

5.
从20世纪80年代以来古生产力的重建研究一直是国内外海洋生态学研究的热点,但已有的大多数研究是在深海区;而陆架区的特点是来自陆源物质的影响往往比较明显,因此,研究难度远较深海区大。利用现代沉积物中的有机碳稳定同位素组成来估算海源碳的含量,在此基础上,结合调查区域表层沉积物中的几个初级生产力的代表性指标(浮游植物总量、叶绿素a浓度以及硅藻含量)的调查资料,寻求岩心中海源碳与古生产力指标的相关关系,再由南黄海冷涡沉积区3个典型柱状沉积物中海源碳重建了200a以来高分辨率的古生产力记录,这对陆架海生态环境演变规律的研究有重要意义。对重建所得到的南黄海近代初级生产演化因素的初步探讨表明,近200a来初级生产力波动升高与海水表层温度的升高趋势是一致的,但其最主要的控制因素还是营养盐的供应,其中陆源营养物质和污染物质的影响起到了重要的作用。  相似文献   

6.
东亚边缘海区浮游植物春华的纬向与年际变化   总被引：1，自引：1，他引：0  
Combined studies of latitudinal and interannual variations of annual phytoplankton bloom peak in East Asian marginal seas(17°–58°N, including the northern South China Sea(SCS), Kuroshio waters, the Sea of Japan and the Okhotsk Sea) are rarely. Based on satellite-retrieved ten-year(2003–2012) median timing of the annual Chlorophyll a concentration(Chl a) climax, here we report that this annual spring bloom peak generally delays from the SCS in January to the Okhotsk Sea in June at a rate of(21.20±2.86) km/d(decadal median±SD). Spring bloom is dominant feature of the phytoplankton annual cycle over these regions, except for the SCS which features winter bloom. The fluctuation of the annual peak timing is mainly within ±48 d departured from the decadal median peak date, therefore this period(the decadal median peak date ±48 d) is defined as annual spring bloom period. As sea surface temperature rises, earlier spring bloom peak timing but decreasing averaged Chl a biomass in the spring bloom period due to insufficient light is evident in the Okhotsk Sea from 2003 to 2012. For the rest of three study domains, there are no significant interannual variance trend of the peak timing and the averaged Chl a biomass. Furthermore this change of spring phytoplankton bloom timing and magnitude in the Okhotsk Sea challenges previous prediction that ocean warming would enhance algal productivity at high latitudes.  相似文献   

7.
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   

8.
1Introduction TheBeringSea,locatedinthesub-arcticNorth Pacific,playsanimportantroleininfluencingtheevo- lutionaryprocessoftheglobalclimaticsystembecause itsseasonalseaiceisformedinrelativelowerlatitudes (Takahashi,1999).ItisalsoasinkofatmosphericCO2, whichisoriginatedfromtheeffectivebiologicalpump inthissea.Particulatefluxdatameasuredinthesea overthelast10aindicatethattheorganic/inorganic carbonratiowasalwaysgreaterthan1,whichexplains thattheBeingSeaoccupiesasignificantpositionin theproces…  相似文献   

9.
Accumulation rates of (marine) organic carbon and estimates of paleoproductivity from organic carbon data indicate distinct late Quaternary glacial/interglacial cycles at Ocean Drilling Program (ODP) Site 646. During the last 240,000 years, surface-water productivity was significantly higher in the northern Labrador Sea during interglacial than during glacial times (70 to 170 gC/m2/yr vs. 30 to 70 gC/m2/yr). The reduced glacial productivity is probably caused by a closed sea-ice cover dominating the northern Labrador Sea during glacial intervals.  相似文献   

10.
Biomarkers had been widely used to reconstruct phytoplankton productivity,and this method was applied in the East China Sea and the Huanghai Sea (Yellow Sea).In this study,Biologic Silicon (BSi) was used as productivity proxy to reconstruct productivity change of phytoplankton during last 200 years.The results show that the BSi contents of surficial sediments were in the range of 0.018%-2.516%,averaging 0.726%,and had a similar variation trend with phytoplankton biomass.The vertical distribution profiles revealed that BSi contents were relatively stable,in accordance with the variations of the contemporary phytoplankton standing crop index.According to the stability analysis of BSi in sediments,BSi was not degradaded for the past two hundred years and remained in sediments steadily.Thus,BSi in sediments had the potential to invert paleoproductivity.To conduct further survey,the linear regression equation between BSi contents and phytoplankton biomass index could be used to calculate the phytoplankton productivity by BSi,so that paleoproductivity may be reconstructed during last 200 years.  相似文献   

11.
通过对南海北部MD05-2904岩心进行有机地球化学分析,以长链不饱和烯酮作为颗石藻生产力的替代性指标,讨论颗石藻生产力的变化及其影响因素。结果显示,260ka以来,颗石藻生产力有着明显的冰期/间冰期变化:冰期高,间冰期低;冰阶高,间冰阶低;在轨道尺度上岁差周期明显,反映出太阳辐射、东亚季风对颗石藻生产力在长期尺度上起调控作用;而由于特殊的地理位置,河流输送的营养盐对本区海洋初级生产力的影响可能也较大;与前人研究结果一致,同时认为,在地质历史上沉积速率变化大的区域,对生物标记物的含量和堆积速率的对比讨论,更有利于反映生产力的变化。  相似文献   

12.
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   

13.
A new grid data set for the southwestern part of the Okhotsk Sea was compiled by using all the available hydrographic data from the Japan Oceanographic Data Center, World Ocean Atlas 1994 and the other additional data sources with the resolution of about 10 km. We examine the seasonal variations of areas and volumes of Soya Warm Current Water (SWCW) and East Sakhalin Current Water (ESCW) and show that the exchanges of these water masses drastically occur in April and November. The peculiar variation of sea level in this region is also related with the water mass exchange. Sea level at the Hokkaido coast of the Okhotsk Sea reaches its minimum in April about two months later than in the case of ordinary mid-latitude ocean, and its maximum in December besides the summer peak. The winter peak of sea level in December is caused by the advent of fresh and cold ESCW which is accumulated at the subsurface layers (20–150 m) through the Ekman convergence by the prevailing northerly wind. Sea level minimum in April is caused by the release of the convergence and the recovery of dense SWCW that is saline and much colder than that in summer.  相似文献   

14.
Subinertial and seasonal variations in the Soya Warm Current (SWC) are investigated using data obtained by high frequency (HF) ocean radars, coastal tide gauges, and a bottom-mounted acoustic Doppler current profiler (ADCP). The HF radars clearly captured the seasonal variations in the surface current fields of the SWC. Almost the same seasonal cycle was repeated in the period from August 2003 to March 2007, although interannual variations were also discernible. In addition to the annual and interannual variations, the SWC exhibited subinertial variations with a period of 5–20 days. The surface transport by the SWC was significantly correlated with the sea level difference between the Sea of Japan and Sea of Okhotsk for both the seasonal and subinertial variations, indicating that the SWC is driven by the sea level difference between the two seas. The generation mechanism of the subinertial variation is discussed using wind data from the European Centre for Medium-range Weather Forecasts (ECMWF) analyses. The subinertial variations in the SWC were significantly correlated with the meridional wind stress component over the region. The subinertial variations in the sea level difference and surface current delay from the meridional wind stress variations by one or two days. Sea level difference through the strait caused by wind-generated coastally trapped waves (CTWs) along the east coast of Sakhalin and west coast of Hokkaido is considered to be a possible mechanism causing the subinertial variations in the SWC.  相似文献   

15.
对取自热带西太平洋暖池核心区的WP7岩心进行了底栖有孔虫和钙质超微化石研究。在利用氧同位素曲线对比和AMS14C测年数据进行地层划分的基础上,依据底栖有孔虫和钙质超微化石指标,分析了距今近250ka以来区域生产力和上层海水结构的演变特征,探讨了其控制因素和所指示的古海洋学意义。计算结果显示WP7岩心所在的暖池核心区约在距今250ka以来初级生产力在冰期(MIS6期、4期和2期)高,在间冰期(MIS7期、5期、3期和1期)低,表明该区古生产力在长的轨道时间尺度上受北半球高纬度冰量变动的影响。钙质超微化石下透光带属种Flori-sphaera profunda百分含量指示的温跃层深度变化表明冰期温跃层浅、间冰期温跃层加深,这说明类ENSO式变化导致的冰期—间冰期温跃层深度波动可能是MIS7期以来暖池核心区古生产力在冰期高而在间冰期显著降低的直接控制因素。  相似文献   

16.
Abundant evidences of higher sea levels from Jiangsu and Fujian coasts have proved a marine transgression event during 30–40 ka BP, suggesting that there was a stage with high sea level and a warm climate when ice sheets shrank in the Northern Hemisphere. The duration of 30–40 ka BP spanned a period in the late Marine Isotope Stage 3(MIS 3) and was in nature an interstadial epoch during the Last Glacial period of the Quaternary. Different from the glacial period with a cold climate, this marine transgression considered as a penultimate higher sea level during the Quaternary remains a puzzle that why the evidence is contrary to the Quaternary glacial theory. It is important to understand sea level rise for these areas sensitively responding to the global changes in the future. To recognize the key issues on sea level changes, the eustatic sea level(H_S) was defined as the glaciation-climateforced sea levels, and the relative sea level change(H_R) was defined as that a sea level record was preserved in sediment that experienced multiple secondary actions of land and sea effects. On the basis as defined above, we constructed multi-level models of climate-driven glacio-eustatic changes and land-sea systems. By integrating data sets from eight borehole cores and prescribing the boundary conditions, we simulated the changes of HS and HR in the East China Sea and southern Yellow Sea areas in the late MIS 3. The marine transgression strata from the borehole core data was identified at ca. 30 m below present sea level as a result of the collective influence of ice melting water, neotectonic subsidence, sediment compaction and terrestrial sediment filling since ca. 35 ka ago,whereas the simulated relative sea-levels turned out to be –26.3––29.9 m a.s.l. The small error involved in the simulation results of ±(2.5–4.5) m demonstrated the credibility of the results. Our results indicated that sea level change in the late MIS 3 was dominated by glacial effects, in which the eustatic sea-level was between –19.2––22.1m a.s.l. The study sheds light on the nature of sea-level changes along the east coast of China in the late MIS 3 and contributes to understanding the characteristics of marine transgression under the effects of multiple complex land-sea interactions.  相似文献   

17.
古海洋生产力的研究方法   总被引：7，自引：0，他引：7  
海洋的初级生产力控制了温室气体CO2在海洋和大气中的分配,进而影响着全球气候变迁,只有通过运用不同的生产力标志物才能探讨地质历史上海洋初级生产力的变迁及其对气候的影响。介绍了国内外在古海洋生产力研究领域内使用的主要方法和动态,并分别对生源物质累积率、底栖有孔虫标志物和地球化学标志物等研究方法进行了全面的分析和评述,指出在运用生产力标志物研究古生产力时应充分考虑不同标志物的适用性和局限性。  相似文献   

18.
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   

19.
The magnitude and geographical distribution of the error in the Archiving, Validation and Interpretation of Satellite Oceanographic data (AVISO) altimetry data associated with tidal correction around Asian marginal seas has been revealed. The errors were evaluated by harmonic analysis of the AVISO corrected sea surface heights data (CorSSH). Errors of more than 15 cm of tidal correction were recognized in the western and northern parts of the Yellow Sea, Celebes Sea, Kuril Islands, and the northwestern part of the Okhotsk Sea. It was found that the CorSSH and sea level anomaly (SLA) data downloaded from the AVISO are not available for direct use in those marginal seas. To reduce the tidal correction error, the harmonic constants calculated from the latest tide model and regional tide model were applied as the tidal correction of the Altimetry data. The tidal errors in the Yellow Sea and the northwestern part of the Okhotsk Sea were reduced by approximately 20 cm and 10 cm, respectively. Root mean square differences between the harmonic constants derived from tide models and those derived from altimetry data were calculated. The root mean square differences were large in the Yellow and the Okhotsk Seas. Root sum squares for four principal tidal constituents in the Yellow and East China Seas and Okhotsk Sea were 7.72 cm and 8.36 cm, respectively.  相似文献   

20.
The distribution of diatoms, radiolarians, planktonic and benthic foraminifers, and sediment components in the fraction >0.125 mm was analyzed in the core obtained from the central Sea of Okhotsk within the frameworks of the Russian-German KOMEX project. The core section characterizes the period 190–350 ka, which corresponds to marine-isotopic stages (MIS) 7 to 10. During glacial MIS 10 and MIS 8, the basin accumulated terrigenous material lacking microfossils or containing them in low abundance, which reflects, along with their composition, heavy sea-ice conditions, suppressed bioproductivity, and bottom environments aggressive toward calcium carbonate. Interglacial MIS 9 was characterized by elevated bioproductivity with accumulation of diatomaceous ooze during the climatic optimum (328 to 320 ka). The water exchange with the Pacific was maximal from 328 to 324 ka ago. Environments became moderate and close to the present-day ones at the end of the optimum exhibiting the possible existence of a dichothermal layer with substantial amounts of the surface Pacific water still flowing into the basin. Similar to interglacial MIS 5e and MIS 1, the “old” Pacific water determined near-bottom environments in the central Sea of Okhotsk during that period, although the influx of terrigenous material was higher, probably reflecting a more humid climate of the region. Slight warming marked the terminal MIS 8 (approximately 260 ka ago). The paleoceanographic situation during interglacial MIS 7 was highly variable: from warm-water to almost glacial. The main climatic optimum of MIS 7 occurred within 220–210 ka, when the subsurface stratification increased and the dichothermal layer developed. Bottom environments during the studied time interval, except for the optimum of interglacial MIS 9, resembled those characteristic of glacial periods: the actively formed “young” Okhotsk water displaced the “old” Pacific deep water.  相似文献   

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