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1.
Paleoceanographic records in the Chukchi Basin, western Arctic Ocean during the late Quaternary 总被引：1，自引：0，他引：1
The late Quaternary paleoceanographic changes in the western Arctic Ocean are revealed by quantitative studies of foraminiferal abundance, ice-rafted detritus (IRD) and its mineralogical and petrological compositions, planktonic Neogloboquadrina pachyderma (sin.) (Nps)-δ18O and -δ13C, biogenic and non-biogenic components in Core M03 token from the Chukchi Basin during the Second Chinese National Arctic Expedition cruise. Seven IRD events appeared at MIS 7, 5, 3 and 1. These IRD were carried in massive icebergs, which were exported to the Beaufort Sea through the M'Clure Strait Ice Stream, Canadian Arctic Archipelago, and then transported into the Chukchi Basin by the Beaufort Gyre. Low IRD deposition occurred during the glacial times when more extended ice cover and weakened Beaufort Gyre, while the open water condition and the intensified Beaufort Gyre during interglacial periods favored the IRD deposition. Therefore, the IRD events not only indicate the provenance of coarser detritus and ice export events, but also reflect the evolutionary histories of the Beaufort Gyre and North American ice sheet. Seven light Nps-δ18O and -δ13C excursions could respond to enhanced rates of sea ice formation resulting in the production and sinking of isotopically light brines, but was irrelevant to the warm Atlantic water and freshwater inputs. Whereas, the heavy Nps-δ18O and -δ13C values separately reflect the lessened Arctic freshwater and Pacific water, and well-ventilated surface water from the continental shelf and halocline water. Variations of CaCO3 content and planktonic foraminiferal abundance during the interglacial and glacial periods can demonstrate the incremental or diminishing input of the Atlantic water, while the total organic carbon (TOC) and opal contents increased and decreased during the glacial and interglacial periods, respectively, which could be related to the TOC degradation, opal dissolution and redox conditions of interface between the bottom water and sediments. 相似文献
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Evidence of shelf-water transfer from temperature, salinity, and 228Ra/226Ra sampling from the nuclear submarine USS L. Mendel Rivers SCICEX cruise in October, 2000 demonstrates the heterogeneity of the Arctic Ocean with respect to halocline ventilation. This likely reflects both time-dependent events on the shelves and the variety of dispersal mechanisms within the ocean, including boundary currents and eddies, at least one of which was sampled in this work. Halocline waters at the 132 m sampling depth in the interior Eurasian Basin are generally not well connected to the shelves, consonant with their ventilation within the deep basins, rather than on the shelves. In the western Arctic, steep gradients in 228Ra/226Ra ratio and age since shelf contact are consistent with very slow exchange between the Chukchi shelf and the interior Beaufort Gyre. These are the first radium measurements from a nuclear submarine. 相似文献
4.
Carin J. Ashjian Scott M. Gallager Stphane Plourde 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3259
A key goal of the Western Arctic Shelf Basin Interactions program is to understand how physical and biological processes together impact shelf–basin exchange of biological, chemical, and physical properties. High-resolution vertical distributions of plankton and particles were obtained using an Auto Video Plankton Recorder from 29 locations on the Chukchi Shelf, in the deep Beaufort Sea, and across the Beaufort–Chukchi Shelf-break during a cruise on the USCGC Healy in July–August, 2002. Coincident velocity estimates were collected using hull-mounted acoustic Doppler current profilers. Images of plankton and particles were extracted automatically and identified manually to taxa and type. Copepods, diatom chains, decaying diatoms, marine snow, and radiolarians were the most abundant categories observed. Distinct regional differences in abundance were observed that were associated with different oceanographic regimes and with the prevailing circulation in the region. Vertical distributions were closely associated with the physical structure of the water column. A sharp horizontal discontinuity in abundance of all categories between shelf and basin was observed, located over the shelf break and potentially established and maintained by transport of plankton and particles along-shelf to the east rather than northwards towards the basin. Barrow Canyon and the shelf and shelf-break east of Barrow Canyon had very high concentrations of plankton and particles, especially marine snow, that may have resulted from elevated production on the eastern Chukchi Shelf that subsequently was advected out of Barrow Canyon and to the east. Comparisons of downward flux, estimated from particle sinking rates based on individual marine snow particle size, and horizontal velocities suggested that much of the marine snow carbon was sinking to the benthos of the Chukchi Sea prior to being advected off-shelf. Velocities and plankton concentrations together indicated that little off-shelf flux of plankton or particles to the basin was occurring except in an eddy located off of the Beaufort Shelf. 相似文献
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通过对北冰洋西部(楚科奇海及北部边缘地带、加拿大海盆)34个表层沉积物样品中黏土组分的Sm-Nd同位素分析,结果表明:(1)黏土组分的Sm-Nd同位素分异明显,可将沉积物划分为北部、西部、南部和东部等多个同位素物源区;(2)在楚科奇海,太平洋入流的向北输运自西向东形成了3个不同的同位素物源区,沉积物的c(147Sm)/c(144Nd)比值、εNd(0)值和TDM年龄自西向东呈递减趋势;(3)在研究区北部,顺时针方向流动的波弗特涡流将马更些河物质向西搬运至加拿大海盆和楚科奇高地,使该区沉积物εNd(0)值明显偏低,TDM偏大;(4)在楚科奇海北部外陆架、海台和陆坡区,太平洋水、大西洋水和波弗特涡流的相互作用使该区沉积物TDM年龄的标准偏差大,同时出现了南-北源和西-南源等同位素混合类型。 相似文献
7.
Spatio-temporal distribution of dissolved inorganic carbon and net community production in the Chukchi and Beaufort Seas 总被引：2，自引：0，他引：2
Nicholas R. Bates Margaret H.P. Best Dennis A. Hansell 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3303
As part of the 2002 Western Arctic Shelf–Basin Interactions (SBI) project, spatio-temporal variability of dissolved inorganic carbon (DIC) was employed to determine rates of net community production (NCP) for the Chukchi and western Beaufort Sea shelf and slope, and Canada Basin of the Arctic Ocean. Seasonal and spatial distributions of DIC were characterized for all water masses (e.g., mixed layer, halocline waters, Atlantic layer, and deep Arctic Ocean) of the Chukchi Sea region during field investigations in spring (5 May–15 June 2002) and summer (15 July–25 August 2002). Between these periods, high rates of phytoplankton production resulted in large drawdown of inorganic nutrients and DIC in the Polar Mixed Layer (PML) and in the shallow depths of the Upper Halocline Layer (UHL). The highest rates of NCP (1000–2850 mg C m−2 d−1) occurred on the shelf in the Barrow Canyon region of the Chukchi Sea and east of Barrow in the western Beaufort Sea. A total NCP rate of 8.9–17.8×1012 g for the growing season was estimated for the eastern Chukchi Sea shelf and slope region. Very low inorganic nutrient concentrations and low rates of NCP (<15–25 mg C m−2 d−1) estimated for the mixed layer of the adjacent Arctic Ocean basin indicate that this area is perennially oligotrophic. 相似文献
8.
V. M. Sergeeva I. N. Sukhanova M. V. Flint L. A. Pautova J. M. Grebmeier L. W. Cooper 《Oceanology》2010,50(2):184-197
The phytoplankton community was studied in Bering Strait and over the shelf, continental slope, and deep-water zones of the
Chukchi and Beaufort seas in the middle of the vegetative season (July–August 2003). Its structure was analyzed in relation
to ice conditions and the seasonal patterns of water warming, stratification, and nutrient concentrations. The overall ranges
of variation in phytoplankton abundance and biomass were estimated at 2.0 × 102 to 6.0 × 106 cells/l and 0.1 to 444.1 mg C/m3. The bulk of phytoplankton cells concentrated in the seasonal picnocline, at depths of 10–25 m. The highest values of cell
density and biomass were recorded in regions influenced by the inflow of Bering Sea waters or characterized by intense hydrodynamics,
such as the Bering Strait, Barrow Canyon, and the outer shelf and slope of the Chukchi Sea. In the middle of the vegetative
season, the phytoplankton in the study region of the Western Arctic proved to comprise three successional (seasonal) assemblages,
namely, the early spring, late spring, and summer assemblages. Their spatial distribution was dependent mainly on local features
of hydrological and nutrient regimes rather than on general latitudinal trends of seasonal succession characteristic of arctic
ecosystems. 相似文献
9.
对白令海表层海水228Ra的分析表明,白令海表层海水228Ra比活度从低于检测限变化至0.81 Bq/m3,低于西北冰洋陆架区的报道值。表层水228Ra比活度和228Ra/226Ra)A.R.的空间分布均呈现由西南部中心海盆向东北部陆架区增加的趋势。由228Ra/226Ra)A.R.和盐度的关系揭示出白令海环流、白令海陆坡流和阿拉斯加沿岸流对228Ra和228Ra/226Ra)A.R.分布有明显影响。运用一维稳态扩散模型计算出白令海由中心海盆向东北部陆架方向上水体混合的水平涡动扩散系数为1.9×108 m2/d。结合海盆-陆架界面营养盐的水平浓度梯度,估算得硝酸盐、活性磷酸盐和活性硅酸盐由白令海中心海盆向东北部陆架区的水平输送通量,该通量对白令海东北部陆架区新生产力的贡献很小,其他途径输送的营养盐更为重要。 相似文献
10.
1979-2012年北极海冰运动学特征初步分析 总被引：3，自引：3，他引：0
利用美国冰雪数据中心(NSIDC)发布的海冰速度和范围数据,本文分析了1979—2012年间北极海冰的运动学特征,以及北极海冰运动与分布范围演变之间的关系。结合欧洲中期天气预报中心(ECMWF)发布的2007和2012年高分辨率的气压场、风场数据,探讨了北极风场和气压场与海冰运动、辐散辐合和海冰面积的关系。结果表明,在1979-2012年间北极海冰平均运动速度呈显著增强的趋势,冬季海冰平均运动速度增加趋势明显强于夏季;北极、波弗特-楚科奇海域和弗拉姆海峡的冬、夏季海冰平均运动速度的增加率分别为2.1%/a和1.7%/a、2.0%/a和1.6%/a以及4.9%/a和2.2%/a。1979-2012年北极海冰平均运动速度和范围的相关性为-0.77,二者存在显著的负相关关系。北极冬季和夏季风场的长期变化趋势与海冰平均运动速度的变化趋势一致,冬季和夏季的相关系数分别为0.50和0.48。风场和气压场对海冰的运动、辐散及重新分布发挥着重要作用。2007年夏季,第234~273天波弗特海域一直被高压系统控制,波弗特涡旋加强,使得波弗特海域海冰聚集在北极中央区;顺时针的风场促使海冰向格陵兰岛和加拿大北极群岛以北聚合。2012年,白令海峡和楚科奇海域处于低压和高压系统的交界处,盛行偏北风,海冰从北极东部往西部输运,加拿大海盆的多年海冰因离岸运动而辐散,向楚科奇海域的海冰输运增加,受太平洋入流暖水影响,移入此区域的海冰加速融化,从而加剧海冰的减少。 相似文献
11.
白令海、西北冰洋等高生产力海域在北冰洋“生物泵”中起到重要作用；海水升温、海冰消退等北极快速变化，将强烈影响该海域“生物泵”的结构与规模，并在沉积物中有机质的来源与新鲜程度上有所体现，可用脂肪酸加以指征。对第五次、第六次中国北极科学考察在以上海域采集的表层沉积物进行脂肪酸含量（以沉积物干重计）及组成分析，结果显示楚科奇海陆架总脂肪酸含量非常高((97.15± 55.31) μg/g)，白令海盆最低((15.00±1.30) μg/g)，加拿大海盆、楚科奇海陆坡、白令海陆架居中(分别为(88.65 ± 3.52) μg/g，(70.35±11.32) μg/g与(38.28±14.89) μg/g)。海源脂肪酸占总脂肪酸比例最高(86.82%±7.08%)，陆源次之(8.45%±6.62%)，细菌最低(4.63%±2.24%)；硅藻指数(16:1ω9/16:0)在楚科奇海陆架(> 0.82)、白令海陆架边缘(> 0.65)较高，其他区域均较低。脂肪酸结果表明:(1) 该海域沉积有机质主要来自海源，陆源贡献小；在北部、南部楚科奇海陆架、白令海陆架边缘，硅藻生物量占主要优势；细菌脂肪酸比例显著低于温暖海域，指示低温抑制细菌活动。(2) 楚科奇海陆架区硅藻生产力高、细菌活动弱，新鲜有机质沉降效率高，但对未来海水升温、浮游植物群落变化也较为敏感。(3) 加拿大海盆、楚科奇海陆坡的浮游植物群落由绿藻与金藻主导。以上结论说明脂肪酸可指示表层沉积物中有机质的来源与新鲜程度；未来，脂肪酸有望进一步揭示北冰洋“生物泵”对北极快速变化的响应。 相似文献
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对中国第四次北极科学考察期间在白令海北部获取的海水样品进行悬浮体含量及其颗粒组分特征的分析。结果表明,白令海陆架海区悬浮体含量大体呈现出表层浓度低而底层浓度高的特点。表层海水悬浮体含量在白令海峡西侧和陆架东侧靠近阿拉斯加沿岸含量较高,而底层海水中悬浮体含量则在白令海峡西侧,以及白令海陆架西南部的圣马修岛西北侧较高。陆架流系对底床物质的再悬浮作用致使白令海悬浮颗粒物浓度的高值区多位于近底层海水中。受白令陆坡流沿陆架坡折带输运作用,研究区西南部悬浮体浓度较高。白令海陆架水以及阿纳德尔流携带悬浮颗粒向北输运,使得底层悬浮体浓度呈现出自南向北逐渐减弱的模式。圣劳仑斯岛以北靠近楚科奇半岛一侧海域,受高营养盐的阿纳德尔流的影响,悬浮颗粒物以藻类为主;东侧阿拉斯加沿岸流区悬浮颗粒则以陆源的碎屑矿物为主。 相似文献
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Sediment transport by sea ice in the Chukchi and Beaufort Seas: Increasing importance due to changing ice conditions? 总被引：1，自引：0，他引：1
H. Eicken R. Gradinger A. Gaylord A. Mahoney I. Rigor H. Melling 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3281
Sediment-laden sea ice is widespread over the shallow, wide Siberian Arctic shelves, with off-shelf export from the Laptev and East Siberian Seas contributing substantially to the Arctic Ocean's sediment budget. By contrast, the North American shelves, owing to their narrow width and greater water depths, have not been deemed as important for basin-wide sediment transport by sea ice. Observations over the Chukchi and Beaufort shelves in 2001/02 revealed the widespread occurrence of sediment-laden ice over an area of more than 100,000 km2 between 68 and 74°N and 155 and 170°W. Ice stratigraphic studies indicate that sediment inclusions were associated with entrainment of frazil ice into deformed, multiple layers of rafted nilas, indicative of a flaw-lead environment adjacent to the landfast ice of the Chukchi and Beaufort Seas. This is corroborated by buoy trajectories and satellite imagery indicating entrainment in a coastal polynya in the eastern Chukchi Sea in February of 2002 as well as formation of sediment-laden ice along the Beaufort Sea coast as far eastward as the Mackenzie shelf. Moored upward-looking sonar on the Mackenzie shelf provides further insight into the ice growth and deformation regime governing sediment entrainment. Analysis of Radarsat Synthetic Aperture (SAR) imagery in conjunction with bathymetric data help constrain the water depth of sediment resuspension and subsequent ice entrainment (>20 m for the Chukchi Sea). Sediment loads averaged at 128 t km–2, with sediment occurring in layers of roughly 0.5 m thickness, mostly in the lower ice layers. The total amount of sediment transported by sea ice (mostly out of the narrow zone between the landfast ice edge and waters too deep for resuspension and entrainment) is at minimum 4×106 t in the sampling area and is estimated at 5–8×106 t over the entire Chukchi and Beaufort shelves in 2001/02, representing a significant term in the sediment budget of the western Arctic Ocean. Recent changes in the Chukchi and Beaufort Sea ice regimes (reduced summer minimum ice extent, ice thinning, reduction in multi-year ice extent, altered drift paths and mid-winter landfast ice break-out events) have likely resulted in an increase of sediment-laden ice in the area. Apart from contributing substantially to along- and across-shelf particulate flow, an increase in the amount of dirty ice significantly impacts (sub-)ice algal production and may enhance the dispersal of pollutants. 相似文献
14.
On the basis of the CTD data obtained within the Bering Sea shelf by the Second to Sixth Chinese National Arctic Research Expedition in the summers of 2003, 2008, 2010, 2012 and 2014, the classification and interannual variation of water masses on the central Bering Sea shelf and the northern Bering Sea shelf are analyzed. The results indicate that there are both connection and difference between two regions in hydrological features. On the central Bering Sea shelf, there are mainly four types of water masses distribute orderly from the slope to the coast of Alaska: Bering Slope Current Water(BSCW), MW(Mixed Water), Bering Shelf Water(BSW) and Alaska Coastal Water(ACW). In summer, BSW can be divided into Bering Shelf Surface Water(BSW_S) and Bering Shelf Cold Water(BSW_C). On the northern Bering Sea shelf near the Bering Strait,it contains Anadyr Water(AW), BSW and ACW from west to east. But the spatial-temporal features are also remarkable in each region. On the central shelf, the BSCW is saltiest and occupies the west of 177°W, which has the highest salinity in 2014. The BSW_C is the coldest water mass and warmest in 2014; the ACW is freshest and mainly occupies the east of 170°W, which has the highest temperature and salinity in 2012. On the northern Bering Sea shelf near the Bering Strait, the AW is saltiest with temperature decreasing sharply compared with BSCW on the central shelf. In the process of moving northward to the Bering Strait, the AW demonstrates a trend of eastward expansion. The ACW is freshest but saltier than the ACW on the central shelf,which is usually located above the BSW and is saltiest in 2014. The BSW distributes between the AW and the ACW and coldest in 2012, but the cold water of the BSW_C on the central shelf, whose temperature less than 0°C, does not exist on the northern shelf. Although there are so many changes, the respond to a climate change is synchronized in the both regions, which can be divided into the warm years(2003 and 2014) and cold years(2008, 2010 and 2012). The year of 2014 may be a new beginning of warm period. 相似文献
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白令海峡夏季流量的年际变化及其成因 总被引：1，自引：1，他引：0
白令海峡是连接太平洋和北冰洋的唯一通道,穿过海峡的海水体积通量在年际尺度上的变化主要取决于海峡南北两侧的海面高度差,白令海峡的入流对北冰洋海洋过程有重要的意义。利用SODA资料计算夏季白令海峡海水体积通量,对其年际变化及成因进行分析。结果表明夏季白令海峡的体积通量主要是正压地转的;当体积通量为正距平时,楚科奇海、东西伯利亚海、拉普捷夫海以及波弗特海南部海面高度为负距平,同时,白令海陆架海面高度为正距平;对这些海域的Ekman运动、上层海洋温度、盐度和垂直流速进行分析,发现海面高度异常与海峡体积通量的这种关系主要是与海面气压异常分布所产生的Ekman运动有关。当白令海峡的体积通量为正距平时,北冰洋中央海面气压为正距平,白令海海盆海面气压为负距平。这种气压的异常分布在一定程度上解释了上层海洋运动、海水温盐结构与白令海峡入流的关系,从而把夏季大尺度大气环流和白令海峡体积通量的年际变化联系了起来。 相似文献
16.
The uptake of atmospheric carbon dioxide in the water transported over the Bering–Chukchi shelves has been assessed from the change in carbon-related chemical constituents. The calculated uptake of atmospheric CO2 from the time that the water enters the Bering Sea shelf until it reaches the northern Chukchi Sea shelf slope (1 year) was estimated to be 86±22 g C m−2 in the upper 100 m. Combining the average uptake per m3 with a volume flow of 0.83×106 m3 s−1 through the Bering Strait yields a flux of 22×1012 g C year−1. We have also estimated the relative contribution from cooling, biology, freshening, CaCO3 dissolution, and denitrification for the modification of the seawater pCO2 over the shelf. The latter three had negligible impact on pCO2 compared to biology and cooling. Biology was found to be almost twice as important as cooling for lowering the pCO2 in the water on the Bering–Chukchi shelves. Those results were compared with earlier surveys made in the Barents Sea, where the uptake of atmospheric CO2 was about half that estimated in the Bering–Chukchi Seas. Cooling and biology were of nearly equal significance in the Barents Sea in driving the flux of CO2 into the ocean. The differences between the two regions are discussed. The loss of inorganic carbon due to primary production was estimated from the change in phosphate concentration in the water column. A larger loss of nitrate relative to phosphate compared to the classical ΔN/ΔP ratio of 16 was found. This excess loss was about 30% of the initial nitrate concentration and could possibly be explained by denitrification in the sediment of the Bering and Chukchi Seas. 相似文献
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J.L. Clement W. Maslowski L.W. Cooper J.M. Grebmeier W. Walczowski 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3509
We have developed and run a model with sufficiently high resolution (9 km and 45 levels) and a large enough spatial domain to allow for realistic representation of flow through the narrow and shallow straits in the northern Bering Sea. This is potentially important for quantification of long-term mean and time-dependent ocean circulation, and water mass and property exchanges between the Pacific and Arctic Oceans. Over a 23 year interval (1979–2001), mean transport through Bering Strait is estimated to be 0.65 Sv. Comparison of our model results with published observations indicates that ocean circulation is not only variable at seasonal to interdecadal scales but it is also responsive to short-term atmospheric forcing. One of such events occurred during the winter of 2000–2001 with reversed oceanic flow in some areas and much reduced sea-ice cover. Analyses of eddy kinetic energy fields identify some high biological productivity regions of the Chirikov Basin coincident with persistent high energy (up to 2700 cm2 s−2 in the surface layer and up to 2600 cm2 s−2 at mid-depth) throughout the annual cycle. Model output in the Bering Strait region is validated against several time series of moored observations of water mass properties. Comparison with shipboard observations of near-bottom salinity from late winter through autumn indicates that the model reasonably represents the major water-mass properties in the region. The modeled vertical water-column structure in the northern Bering Sea allows increased understanding of the mechanisms of water transformation and transport northward through Bering Strait into the Chukchi and Beaufort Seas. We conclude that the long-term model results for the northern Bering Sea provide important insights into the ocean circulation and fluxes and they are a useful frame of reference for limited observations that are short-term and/or cover only a small geographic region. 相似文献
19.
1 IntroductionTheBeringStrait, with them aximum depth lessthan 60 m , isthe uniquepassagebetween the ArcticOcean and the North Pacific Ocean, and links twoshelfseas:theBeringSeainthesouthandtheChukchiSea in the north. The background flow field oftheBering… 相似文献
20.
Circulation on the north central Chukchi Sea shelf 总被引：8，自引：0，他引：8
Thomas Weingartner Knut Aagaard Rebecca Woodgate Seth Danielson Yasunori Sasaki Donald Cavalieri 《Deep Sea Research Part II: Topical Studies in Oceanography》2005,52(24-26):3150
Mooring and shipboard data collected between 1992 and 1995 delineate the circulation over the north central Chukchi shelf. Previous studies indicated that Pacific waters crossed the Chukchi shelf through Herald Valley (in the west) and Barrow Canyon (in the east). We find a third branch (through the Central Channel) onto the outer shelf. The Central Channel transport varies seasonally in phase with Bering Strait transport, and is 0.2 Sv on average, although some of this might include water entrained from the outflow through Herald Valley. A portion of the Central Channel outflow moves eastward and converges with the Alaskan Coastal Current at the head of Barrow Canyon. The remainder appears to continue northeastward over the central outer shelf toward the shelfbreak, joined by outflow from Herald Valley. The mean flow opposes the prevailing winds and is primarily forced by the sea-level slope between the Pacific and Arctic oceans. Current variations are mainly wind forced, but baroclinic forcing, associated with upstream dense-water formation in coastal polynyas might occasionally be important.Winter water-mass modification depends crucially on the fall and winter winds, which control seasonal ice development. An extensive fall ice cover delays cooling, limits new ice formation, and results in little salinization. In such years, Bering shelf waters cross the Chukchi shelf with little modification. In contrast, extensive open water in fall leads to early and rapid cooling, and if accompanied by vigorous ice production within coastal polynyas, results in the production of high-salinity (>33) shelf waters. Such interannual variability likely affects slope processes and the transport of Pacific waters into the Arctic Ocean interior. 相似文献