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1.
The content and distribution of biogenic silica were investigated in sedi- ment cores from Prydz Bay,Antarctica,during the CHINARE-18/21.cruise.The re- sults show that the content of biogenic silica(BSiO_2) is ranged from 4.89% to 85. 41%,and the average content of biogenic silica is 30.90%,the highest value oc- curred at theⅣ-10 station.The profile of BSiO_2 in sediment is contrast to that of sili- cate in the interstitial water.The content of biogenic silica and organic carbon in the surface sediments in the central area of Prydz Bay gyre were much higher than those in other area,and closely related to the Chla content and primary productivity of phyto- plankton in the surface water column.  相似文献   

2.
The investigation of size-fractionated chlorophyll a and primary productivity were carried out in three longitudinal sections (63°-69°12'S, 70°30'E, 73°E and 75(30'E) at December 18-26, 1998 and January 12-18, 1999 in Prydz Bay and its north sea area, Antarctica. The results showed that surface chlorophyll a concentration were 0. 16 -3. 99 μg dm-3. The high values of chlorophyll a concentration (more than 3.5 μg dm -3) were in Prydz Bay and in the west Ladies Bank. The average chlorophyll a concentration at sub-surface layer was higher than that at surface layer; its concentration at the deeper layers of 50 m decreased with increasing depth and that at 200 m depth was only 0. 01 -0. 95μg dm -3. The results of size-fractionated chlorophyll a showed that the contribution of the netplanktion to total chlorophyll a was 56% , those of the nanoplankton and the picoplankton were 24% and 20% respectively in the surveyed area. The potential primary productivity at the euphotic zone in the surveyed area wa  相似文献   

3.
刘会莲  孙松  吉鹏 《极地研究》2002,13(2):117-128
Antarctic krill (Euphausia superba) were collected from the Prydz Bay region during the austral summer of 1999/2000. The sample - collection was made at 15 sites in 3 longitudinal transects. Although krill were encountered at 14 sites, the abundance was comparatively low in general. The main component of the krill population was of post -larval stages. The mean numerical and weight density of krill integrated for all sampling stations in the survey area were 16. 17 ind. 1000 m -3and 12.02 g 1000 m -3 , respectively. In the survey area, stations with larger krill density are mainly located in the slope zone, except that the largest sample was collected in the open sea zone. No krill occurred in the only station of the shelf zone during our investigation. Krill collected from the slope zone were under better growth condition than those from the open sea zone, but when the survey area is considered as a whole, the growth condition is normal. The results of the comprehensive analysis of the environmental fa  相似文献   

4.
The investigation of phytoplankton standing stock, euphotic layer and photosynthesis rate were carried out in 19 27 of January, 2000 at three longitudinal sections (70°30′E, 73°00′E and 75°30′E). The results showed that the high value of chlorophyll a concentration was in inshore bay, polynya and the continental slope of the investigated sea area. At various investigated stations, average chlorophyll a concentration at sub surface layer (25 m) was higher than that at surface layer; its concentration at the deeper layers of over 50 m decreased with increasing depth. At anchor station, the maximum chlorophyll a concentration appeared at surface layer in Antarctic summer's afternoon while the minimum value appeared in the morning; chlorophyll a concentration at water layer of 0 25 m was obviously higher than that at deep water layer, being related to the releasing of ice algae. High productivity was in inshore bay and polynya of continental shelf. Chlorophyll a concentration at surface layer is closely correlated to the dissolved oxygen concentration in seawater. The sea area with chlorophyll a concentration of over 1.0 μg/dm 3 may be the convergence of CO 2 and that of below 1.0 μg/dm 3 may be the source of CO 2.  相似文献   

5.
Summer sea ice characteristics of the Chukchi Sea   总被引：1，自引：0，他引：1       下载免费PDF全文
During August 1999, we investigated sea ice characteristics; its distribution, surface feature, thickness, ice floe movement, and the temperature field around inter-borders of air/ice/seawater in the Chukchi Sea. Thirteen ice cores were drilled at 11 floe stations in the area of 72°24′ 77°18′N, 153°34′ 163°28′W and the ice core structure was observed. From field observation, three melting processes of ice were observed; surface layer melting, surface and bottom layers melting, and all of ice melting. The observation of temperature fields around sea ice floes showed that the bottom melting under the ice floes were important process. As ice floes and open water areas were alternately distributed in summer Arctic Ocean; the water under ice was colder than the open water by 0.4 2.8℃. The sun radiation heated seawater in open sea areas so that the warmer water went to the bottom when the ice floes move to those areas. This causes ice melting to start at the bottom of the ice floes. This process can balance effectively the temperature fluctuating in the sea in summer. From the crystalline structure of sea ice observed from the cores, it was concluded that the ice was composed of ice crystals and brine-ice films. During the sea ice melting, the brine-ice films between ice crystals melted firstly; then the ice crystals were encircled by brine films; the sea ice became the mixture of ice and liquid brine. At the end of melting, the ice crystals would be separated each other, the bond between ice crystals weakens and this leads to the collapse of the ice sheet.  相似文献   

6.
In this paper, the 18 O distribution of surface water from the central sea areas of the Bering Sea and the Chukchi Sea was studied. The δ 18 O value of surface water from the Bering Sea is averagely -0.5‰; the δ 18 O contents of the Chukchi Sea are distributionally lower in northeast and higher in southwest; the δ 18 O value at the margin of Canadian Basin is -2.8‰, and averagely -0.8‰ in the southern area of the Chukchi Sea. The δ 18 O vertical distribution in some deep water stations from the Chukchi Sea and the Bering Sea is also studied. In the southern margin of Canadian Basin, the δ 18 O value is -2‰ -3‰ for surface layer and rises to 0 at 100 m depth layer. In the Bering Sea, the δ 18 O is about -0.5‰ for surface layer and increases to 0 at the depth of 300 m. The NO tracer can reflect obviously three water masses vertically distributed in the central Bering Sea: the upper Bering water mass, the middle Bering water mass and the deep Pacific water mass. The distributive ranges of NO and temperature for the various water masses are T<7℃, NO>780 μmol/dm 3 and T≥7℃, NO>650 μmol/dm 3 for upper Bering water mass, T<4℃, 550相似文献   

7.
Based on the field data acquired in the program of fast ice observation off Zhongshan Station,Prydz Bay,East Antarctica during the austral summer 2005/ 2006,physical properties evolution of fast ice during the ice ablation season is ana- lyzed in detail.Results show that the annual maximum ice thickness in 2005 occurred in later November,and then ice started to melt,and the ablation duration was 62 days;sea water under the ice became warmer synchronously;corresponding to the warming sea ice temperature,a"relative cold mid-layer"appeared in sea ice;the fast ice marginal line recoiled back to the shore observably,and the recoil distance was 20.9 km from 18 December 2005 through 14 January 2006.In addition,based on the data of sea ice thickness survey along the investigation course of MV Xuelong on December 18 of 2005,the ice thickness distribution paten in the marginal ice zone have been described:sea ice thickness increased,but the diversity of floe ice thick- ness decreased from open water to fast ice zone distinctly.  相似文献   

8.
Climate change is now evident in the Qinghai-Tibet Plateau(QTP), with impacts on the alpine ecosystem, particularly on water and heat balance between the active layer and the atmosphere. Thus, we document the basic characteristics of changes in the water and heat dynamics in response to experimental warming in a typical alpine swamp meadow ecosystem. Data sets under open top chambers(OTC) and the control manipulations were collected over a complete year. The results show that annual(2008) air temperatures of OTC-1 and OTC-2 were 6.7 °C and 3.5 °C warmer than the control. Rising temperature promotes plant growth and development. The freeze-thaw and isothermal days of OTCs appeared more frequently than the control, owing to comparably higher water and better vegetation conditions. OTCs soil moisture decreased with the decrease of soil depth; however, there was an obviously middle dry aquifer of the control, which is familiar in QTP. Moreover, experimental warming led to an increase in topsoil water content due to poorly drained swamp meadow ecosystem with higher organic matter content and thicker root horizons. The results of this study will have some contributions to alpine cold ecosystem water-heat process and water cycle under climate change.  相似文献   

9.
During the CHINARE ⅩⅤ cruise in austral summer of 1998/1999, the abundance and feeding activity of Salpa thompsoni were investigated in the Prydz Bay region. Salps samples were collected by vertical tows from the depth of 200 m to the surface with a conical net of 330 μm mesh size. At ⅤⅠ 3 station, the grazing rates were studied by the gut fluorescence method and culture experiments. S. Thompsoni was mainly distributed in the northern part of the survey area, and its maximum densities reached to 2795 ind.·1000 m -3 . A dramatic decrease in salp stock was observed at the Marginal Ice Zone. The results of the feeding experiments at the ⅤⅠ 3 show that the gut pigment contents of S. thompsoni ranged from (0.14 1.27) μg ind. -1 (average 0.98 μg ind. -1 ). The individual ingestion rate is 7.9 μg ind. -1 ·day -1 , and the filtration rate is 28 L ind. -1 ·day -1 . Through the daily grazing rate of S. thompsoni , which takes account of less than 1% of the phytoplankton standing stock, it shows a relatively higher grazing impress on the primary production (72.2%).  相似文献   

10.
<正> Hydrological character and Sea-current profiles structure are studied andanalyzed in sea-area of the front of Amery Ice Shelf,Prydz Bay with LADCP,CTDdata.These LADCP,CTD data were acquired during the 19th Chinese Antarctic Sci-entific Expedition.Results of this study agree with that,there exist four differentkinds of water masses in the area of the front of Amery Ice Shelf in the summer of Ant-arctica.Current distribution presents a semi-circumfluence which flows in at the eastand flows out in the west.Moreover,clockwise and anti-clockwise vortices werefound in upper layer and mid-layer in the Prydz Bay.Western areas of these anti-clockwise vortices are positions of inflows from Prydz Bay to Amery Ice Shelf.Thesource of these inflows is the coastal westward current originated in the east of PrydzBay.All these characteristics come down to the pattern of circumfluence,ice meltrate under Ice Shelf,scale of Ice Shelf water production and form of water exchangesbetween area of Ice Shelf and area of Prydz Bay.  相似文献   

11.
Laboratory experiments were carried out to investigate the effect of freezing and thawing processes on wet aggregate stability （WAS） of black soil. Wet aggregate stability was determined by different aggregate size groups, different water contents, various freeze-thaw cycles, and various freezing temperatures. The results showed that, when at suitable water content, aggregate stability was enhanced, aggregate sta-bility will be disrupted when moisture content is too high or too low, especially higher water content. Temperature also had a significant ef-fect, but moisture content determined the suitable freezing temperatures for a given soil. Water-stable aggregate （WSA〉0.5）, the total aggre-gate content, and mean weight diameter decreasing with the freeze-thaw cycles increase, reached to 5 percent significance level. The reason for crumbing aggregates is the water and air conflict, thus raising the hypothesis that water content affects the aggregate stability in the process of freezing and thawing.  相似文献   

12.
The sea ice core (1.6m) and lake ice core (1.5m) were taken respectively from sea sampling site and Ace Lake near Davis Station, Vestfold Hills, Antarctica in November and October, 1988. The concentrations of amino acids in each 10cm of ice cores were determined by High Pressure Liquid Chromatography (HPLC). The results showed that the concentrations of amino acids revealed seasonal variation during the year. The highest concentration of amino acids, which was 30. 92μmol/ml, were found in the bottom of sea ice core, and it was approximately 45 μmol/ml in the lake ice core. The lowest concentration was approximately 8.0μmol/ml which is presented in surface of the sea ice core, but it was 14.0μmol/ml which was found in 60cm section of lake ice core. The seasonal variation process of concentration of amino acids were much similar to that of phytoplankton cells number in sea ice core, and the distribution and seasonal variation rate of individual amino acids were also much similar in each ice core secti  相似文献   

13.
郭井学  孙波 《极地研究》2007,18(1):36-46
As an important component of the cryosphere,sea ice is very sensitive to the climate change.The study of the sea ice physics needs accurate sea ice thickness.This paper presents an electromagnetic-induction(EM) technique which can be used to measure the sea ice thickness distribution efficiently,and the successful application in Bothnian Bay.Based on the electromagnetic field theory and the electrical properties of sea ice and seawater,EM technique can detect the distance between the instrument and the ice/water interface accurately,than the sea ice thickness is obtained.Contrastive analysis of the apparent conductivity data obtained by EM and the value of drill-hole at same positions allows a construction of a transformable formula of the apparent conductivity to sea ice thickness.The verification of the sea ice thickness calculated by this formula indicates that EM technique is able to get reliable sea ice thickness with average relative error of only 12%.The statistic of all ice thickness profiles shows that the level ice distribution in Bothnian Bay was 0.4-0.6 m.  相似文献   

14.
Vegetation water content is an important indicator of the degree of stress experienced by plants. This paper explored the potential of using the remote sensing data of MERIS (Medium Resolution Imaging Spectrometer) and AATSR (Advanced Along-Track Scanning Radiometer) collected during the Loess Plateau land surface process field Experiment 2005 (LOPEX05) to map and monitor vegetation water content for corn canopies. By comparing with the daily ground observation to validate the satellite reflectance data, we established relationships between the vegetation water content and satellite remotely sensed indices. The two indices studied were the NDVI (Normalized Different Vegetation Index) from MERIS and the NDWI (Normalized Different Water Index) from AATSR. We used the daily ground observation to demonstrate that the NDVI was saturated during the study period while the NDWI continued to reflect the changes in VWC. We found that NDWI, based on near infrared channel (0.855-0.875μm) and short wave infrared wavelength channel (1.58-1.64μm), is suggested to be more suitable and robust approach for retrieval of vegetation water content. The proposed method was validated with experimental field data with biases that are 1.0314 kg/m2 and 0.9413 kg/m2 respectively. Therefore the NDWI was recommended to retrieval the vegetation water content.  相似文献   

15.
珠江广州河段微表层与次表层水环境质量比较(英文)   总被引：1，自引：0，他引：1  
The water quality in the surface microlayer(SML) and subsurface water(SSW) in the Guangzhou segment of Pearl River, a eutrophic urban river section in China, were analyzed. The spatial and temporal dynamics of nutrient concentrations, heavy metals and bacteria were examined from two sampling sites in monthly samples throughout 2010. The mean concentrations of total nitrogen, ammonia, nitrate and nitrite were higher than 7.0 mg/L, 3.1 mg/L, 1.1 mg/L and 0.3 mg/L, while total phosphorus and orthophosphate were 0.5 mg/L and 0.1 mg/L, respectively. These results indicated that the water quality was rich in minerals and eutrophic. The mean concentrations of Mn and Fe were higher than 0.013 mg/L; and Ni, Cr and Pb were higher than 0.001 mg/L. The mean concentrations were in the order of Mn Fe Ni Pb Cr. The concentrations of heavy metals in the Guangzhou segment were lower than the limit of the surface water quality standards in China and the World Health Organization(WHO), but higher than the median values in the world's freshwater. The density of bacteria ranged from 3.30×105 to 5.23×106 cells/mL, and the amount of cultivable heterotrophic bacteria ranged from 1.30×10 3 to 1.89×10 6 cfu/mL. Fecal coliform levels were beyond the V class of China water quality standard. The SML was enriched in nutrients, heavy metals and bacteria, with the maximum enrichment factor of 3.84 for nutrients, 8.00 for heavy metals, and 3.04 for bacteria, suggesting that the water quality of the SML of the Guangzhou segment of the Pearl River was more serious than in the SSW.  相似文献   

16.
李超伦  孙松  张光涛  吉鹏 《极地研究》2001,12(2):153-159
Metabolic rates (oxygen consumption and ammonia excretion) of two dominant copepods, Calanoides acutus and Metridia gerlachei, were measured during the austral summer (December 1998 January 1999), in the marginal ice zone of the Prydz Bay. Their elemental compositions (C and N) were also analysed through these metabolic experiments. The results showed that C. acutus was 48.4% 48.6% of dry weight in carbon content and 6.1% 6.5% of dry weight in nitrogen content. Metridia gerlachei was 47.1% 50.1% and 5.9% 7.4%, relatively. Oxygen consumption rates of C. acutus were variant in the different areas (0.226 to 0.774 μlO 2mg -1h -1). And its ammonia excretion rates ranged from 0.014 to 0.105 μgNmg -1h -1. The ratio between the rates (O∶N) exhibited a large difference(5 6 times). For Metridia gerlachei, oxygen consumption rates were 0.488 0.644 μlO 2mg -1 and ammonia excretion rates were 0.015 0.034 μgNmg -1h -1. From the results of metabolic rate measurements and elemental analyses, daily losses of body carbon and nitrogen were estimated to be 0.59% 1.99% and 0.44% 3.27%, respectively. The metabolic carbon requirements accounted for 0 6% 29 2% of primary production per day, and their excretion of ammonia occupied 0.2% 38.0% of daily phytoplankton nitrogen demand.  相似文献   

17.
近60年黄河水沙变化及其对三角洲沉积的影响   总被引：1，自引：1，他引：0  
In order to find out the variation process of water-sediment and its effect on the Yellow River Delta, the water discharge and sediment load at Lijin from 1950 to 2007 and the decrease of water discharge and sediment load in the Yellow River Basin caused by human disturbances were analyzed by means of statistics. It was shown that the water discharge and sediment load into the sea were decreasing from 1950 to 2007 with serious fluctuation. The human activities were the main cause for decrease of water discharge and sediment load into the sea. From 1950 to 2005, the average annual reduction of water discharge and sediment load by means of water-soil conservation practices were 2.02×109 m3 and 3.41×108 t respectively, and the average annual volume by water abstraction for industry and agriculture were 2.52×1010 m3 and 2.42×108 t respectively. The average sediment trapped by Sanmenxia Reservoir was 1.45×108 t from 1960 to 2007, and the average sediment retention of Xiaolangdi Reservoir was 2.398×108 t from 1997 to 2007. Compared to the data records at Huanyuankou, the water discharge and sediment load into the sea decreased with siltation in the lower reaches and increased with scouring in the lower reaches. The coastline near river mouth extended and the delta area increased when the ratio of accumulative sediment load and accumulative water discharge into the sea (SSCT) is 25.4–26.0 kg/m3 in different time periods. However, the sharp decrease of water discharge and sediment load into the sea in recent years, especially the Yellow River into the sea at Qing 8, the entire Yellow River Delta has turned into erosion from siltation, and the time for a reversal of the state was about 1997.  相似文献   

18.
The spatial distribution of snow cover on the central Arctic sea ice is investigated here based on the observations made during the Third Chinese Arctic Expedition. Six types of snow were observed during the expedition: new/recent snow, melt-freeze crust, icy layer, depth hoar, coarse-grained, and chains of depth hoar. Across most measurement areas, the snow surface was covered by a melt-freeze crust 2-3 cm thick, which was produced by alternate strong solar radiation and the sharp temperature decrease over the summer Arctic Ocean. There was an intermittent layer of snow and ice at the base of the snow pack. The mean bulk density of the snow was 304.01±29.00 kg/m3 along the expedition line, and the surface values were generally smaller than those of the subsurface, confirming the principle of snow densification. In addition, the thicknesses and water equivalents of the new/recent and total-layer snow showed a decreasing trend with latitude, suggesting that the amount of snow cover and its spatial variations were mainly determined by precipitation. Snow temperature also presented significant variations in the vertical profile, and ablation and evaporation were not the primary factors in the snow assessment in late summer. The mean temperature of the surface snow was 2.01±0.96°C, which was much higher than that observed in theinterface of snow and sea ice.  相似文献   

19.
To provide a safe transportation system in an extremely cold region,evaluation needs to be conducted of the thickness and the volumetric water content of the active layer,as they significantly affect frost heave.The objective of this study was to evaluate the dielectric constant(κ)of the active layer using ground-penetrating radar(GPR)and a dynamic cone penetrometer(DCP);this evaluation was then used to estimate the thickness and the volumetric water content of the active layer.A field located in midwest Alaska was selected as the study site.A GPR survey and two DCP tests were conducted on the surface of the ground,and the ground temperature was measured.From the GPR survey,travel times of the electromagnetic wave in the active layer were obtained.In addition,the thickness of the active layer was determined by using the dynamic cone penetration index(DCPI)and ground temperature.By using the travel time and travel distance of the electromagnetic wave in the active layer,dielectric constants were calculated as 26.3 and 26.4 for two DCP points.From the mean dielectric constant,the volumetric water content was estimated to be 40%~43%,and the thickness of the active layer was evaluated along the GPR survey line.The spatial-scaled GPR image showed that the thickness of the active layer varied from 520 mm to 700 mm due to the presence of a puddle,which accelerated the heat exchange.The results show that evaluation of the dielectric constant using the GPR survey and the DCP test can be effectively used to estimate the thickness and the volumetric water content of the active layer.  相似文献   

20.
The desert plant Hedysarum scoparium uses leaflets and rachises as its photosynthetic organs. The abundance of leaflets was lower under unfavorable environmental conditions and higher with improved water conditions. To examine the characteristics associated with the adaptation of H. scoparium to its environment, we selected plants with both compound leaves and rachis without leaflets to study the anatomical structures and gas exchange characteristics of the two organs. The results show that the water storage tissues in rachises were more developed compared with the leaflets. The diurnal courses of the net photosynthetic rate for the rachis and the leaflet were both in a bimodal pattern. Meanwhile, both two peak values of the rachis were significantly higher than those of the leaflet. The daily average transpiration rate was significantly higher in the rachis than in the leaflet in order to lower the temperature of the rachises. It was concluded that under desert drought conditions, the leaflets of H. scoparium were partially or completely degraded to reduce the transpiration area as an adaptive response to water deficit, and only the rachises were retained as photosynthetic organ. The rachises were found to be better suited to a desert habitat than the leaflets.  相似文献   

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