2005 Vol. 24, No. 6
column
Display Method:
2005, (6): 1-11.
Abstract:
The characteristics of current in the Bering Strait and the Chukchi Sea are analyzed based on the two current data on the mooring stations during the Second National Arctic Research Expedition of China in 2003.The tidal currents of the principal diurnal and semidiurnal ellipses rotate clockwise in the upper layer,except for N2,S2,and Q1 at Sta.ST.In the Bering Strait(Sta.ST),the major semiaxis of tidal current constituent M2 is 2.9 cm/s in the upper layer,which is much smaller than that of semi-monthly oscillation(11.8 cm/s); and the mean current flows northwestward at the amplitude of about 20 cm/s and varies a little with depth.During the cruise,the current has significant semi-monthly oscillation at the two mooring stations.The spectra analyses of the air pressure gradient and the wind stress show that there are the semi-monthly oscillations in these two data series.The near-inertial current,approximately 4 cm/s,presents almost the same magnitude of the principal tidal currents in the Bering Strait.
The characteristics of current in the Bering Strait and the Chukchi Sea are analyzed based on the two current data on the mooring stations during the Second National Arctic Research Expedition of China in 2003.The tidal currents of the principal diurnal and semidiurnal ellipses rotate clockwise in the upper layer,except for N2,S2,and Q1 at Sta.ST.In the Bering Strait(Sta.ST),the major semiaxis of tidal current constituent M2 is 2.9 cm/s in the upper layer,which is much smaller than that of semi-monthly oscillation(11.8 cm/s); and the mean current flows northwestward at the amplitude of about 20 cm/s and varies a little with depth.During the cruise,the current has significant semi-monthly oscillation at the two mooring stations.The spectra analyses of the air pressure gradient and the wind stress show that there are the semi-monthly oscillations in these two data series.The near-inertial current,approximately 4 cm/s,presents almost the same magnitude of the principal tidal currents in the Bering Strait.
2005, (6): 12-24.
Abstract:
The upper ocean thermohaline structures in the region of the Chukchi Plateau are analyzed with the hydrographic data collected by the Chinese National Arctic Research Expedition in the summer of 2003. Three types of the Pacific-origin water were found in the upper ocean, Alaska Coastal Water (ACW), summer Bering Sea Water (sBSW) and winter Bering Sea Water (wBSW) are indicated by two maximums temperature and one minimum temperature, piling up from the upper to the lower respectively. The extreme warm ACW with a maximum temperature of 1.62℃ was found in the southwestern Canada Basin at a depth of about 50 m. A pathway of the ACW into the basin from its adjacent area did not existed in the expedition period. So it is speculated that the extreme warm feature of the ACW was formed locally in 2003. The relative weak ACW occurred to the east of the Chukchi Cap and in the southern Chukchi Abyssal Plain. The latter one might originate from a warm downwelling that existed in a small canyon at the shelf break of the Chukchi Sea. The sBSW without the ACW was found only at the southwestern flank of the Chukchi Cap. The ACW and the sBSW were not found in the northernmost station at 81°N,which indicates the north boundary of the upper Pacific-origin water in the Canada Basin. The wBSW, which existed in all deep stations, was exactly uniform at temperature. The difference of the core potential temperature of the wBSW in the deep regions is only 0.08℃.
The upper ocean thermohaline structures in the region of the Chukchi Plateau are analyzed with the hydrographic data collected by the Chinese National Arctic Research Expedition in the summer of 2003. Three types of the Pacific-origin water were found in the upper ocean, Alaska Coastal Water (ACW), summer Bering Sea Water (sBSW) and winter Bering Sea Water (wBSW) are indicated by two maximums temperature and one minimum temperature, piling up from the upper to the lower respectively. The extreme warm ACW with a maximum temperature of 1.62℃ was found in the southwestern Canada Basin at a depth of about 50 m. A pathway of the ACW into the basin from its adjacent area did not existed in the expedition period. So it is speculated that the extreme warm feature of the ACW was formed locally in 2003. The relative weak ACW occurred to the east of the Chukchi Cap and in the southern Chukchi Abyssal Plain. The latter one might originate from a warm downwelling that existed in a small canyon at the shelf break of the Chukchi Sea. The sBSW without the ACW was found only at the southwestern flank of the Chukchi Cap. The ACW and the sBSW were not found in the northernmost station at 81°N,which indicates the north boundary of the upper Pacific-origin water in the Canada Basin. The wBSW, which existed in all deep stations, was exactly uniform at temperature. The difference of the core potential temperature of the wBSW in the deep regions is only 0.08℃.
2005, (6): 25-35.
Abstract:
A year-round halocline is a particular hydrographic structure in the upper Arctic Ocean. On the basis of an analysis of the hydrographic data collected in the Arctic Ocean, it is found that a double-halocline structure exists in the upper layer of the southern Canada Basin,which is absolutely different from the Cold Halocline Layer (CHL) in the Eurasian Basin. The Pacific-origin water is the primary factor in the formation of the double-halocline structure. The upper halocline lies between the summer modification and the winter modification of the Pacific-origin water while the lower halocline results from the Pacific-origin water overlying upon the Atlantic-origin water. Both haloclines are all the year-round although seasonal and interannual variations have been detected in the historical data.
A year-round halocline is a particular hydrographic structure in the upper Arctic Ocean. On the basis of an analysis of the hydrographic data collected in the Arctic Ocean, it is found that a double-halocline structure exists in the upper layer of the southern Canada Basin,which is absolutely different from the Cold Halocline Layer (CHL) in the Eurasian Basin. The Pacific-origin water is the primary factor in the formation of the double-halocline structure. The upper halocline lies between the summer modification and the winter modification of the Pacific-origin water while the lower halocline results from the Pacific-origin water overlying upon the Atlantic-origin water. Both haloclines are all the year-round although seasonal and interannual variations have been detected in the historical data.
2005, (6): 36-45.
Abstract:
The long-term sea-level trend in the Bering Sea is obtained by the analysis of TOPEX/Poseidon altimeter data, including the data of two tide gauges. The averaged sea-level in the Bering Sea rises at a rate of 2.47 mm/a from 1992 to 2002. The mean sea-level is falling in the most part of the Bering Sea, especially in its central basin, and it is rising in the northeastern part of the Bering Sea. During the 1998/99 change, the sea-level anomaly differences exhibit a significant sea-level anomaly fall in the deep basin of the Bering Sea,which is roughly in the same position where a prominent SST fall exists. The maximal fall of sea-level is about 10 cm in the southwestern part of the Bering Sea, and the maximal fall of about 2℃ in the SST also appeared in the same region as the sea level did.The steric sea-level change due to temperature variations is discussed. The results are compared with the TOPEX/Poseidon altimeter data at the different spatial scales. It is indicated that the seasonal amplitude of the steric height is about 35% of the observed TOPEX/Poseidon amplitude, which is much smaller than the 83% in the mid-latitudes area. The systematic difference between the TOPEX/Poseidon data with the range of about 7.5 cm and the thermal contribution with the range of about 2.5 cm is about 5 cm. This indicates that the thermal effect on the sea level is not as important as the case in the mid-latitudes area. In the Bering Sea, the phase of the steric height leads the observed sea level by about three months.
The long-term sea-level trend in the Bering Sea is obtained by the analysis of TOPEX/Poseidon altimeter data, including the data of two tide gauges. The averaged sea-level in the Bering Sea rises at a rate of 2.47 mm/a from 1992 to 2002. The mean sea-level is falling in the most part of the Bering Sea, especially in its central basin, and it is rising in the northeastern part of the Bering Sea. During the 1998/99 change, the sea-level anomaly differences exhibit a significant sea-level anomaly fall in the deep basin of the Bering Sea,which is roughly in the same position where a prominent SST fall exists. The maximal fall of sea-level is about 10 cm in the southwestern part of the Bering Sea, and the maximal fall of about 2℃ in the SST also appeared in the same region as the sea level did.The steric sea-level change due to temperature variations is discussed. The results are compared with the TOPEX/Poseidon altimeter data at the different spatial scales. It is indicated that the seasonal amplitude of the steric height is about 35% of the observed TOPEX/Poseidon amplitude, which is much smaller than the 83% in the mid-latitudes area. The systematic difference between the TOPEX/Poseidon data with the range of about 7.5 cm and the thermal contribution with the range of about 2.5 cm is about 5 cm. This indicates that the thermal effect on the sea level is not as important as the case in the mid-latitudes area. In the Bering Sea, the phase of the steric height leads the observed sea level by about three months.
2005, (6): 46-53.
Abstract:
On the basis of the EOF analysis of global geopotential height anomaly (GHA) field at 10 hPa level, the arctic oscillation (AO) and the means antarctic oscillation (AAO) can be detected more obviously at the upper level of atmosphere than the AO or the AAO in surface layer. Unlike the hemisphere pattern of the AO and the AAO in the surface lager given by previous authors, the AO or the AAO in the stratosphere has its global features. The zonal oscillations-the Southern Oscillation (SO) and the north oscillation (NO) in atmospheric surface layer become less clear in the upper air. The first mode (AO mode, abbreviated to AOM hereafter) and the second mode (AAO mode, abbreviated to AAOM hereafter) respectively have 41.47% and 27.04% of the total variance contribution. The cumulative variance contribution of the first two modes reaches 68.51%. These two modes are the main components for the interdecadal or decadal oscillation in the stratosphere. In addition, there still exist two kinds of oscillation patterns with less probability,namely, the symmetric pattern at mid-high latitudes in the Southern Hemisphere and the asymmetric pattern. Spectral analysis shows that the AOM and the AAOM all have a spectral peak for 22 a period, being consistent with the periodic variations of the solar magnetic field, and a peak for 11 a period, being consistent with the period of the numbers of sunspots. Step filter analysis shows that the influencing factor for the upper atmospheric oscillation is the solar activity. The fluctuation of the solar magnetic field is the more influencing factor than the variation of the sunspot number.
On the basis of the EOF analysis of global geopotential height anomaly (GHA) field at 10 hPa level, the arctic oscillation (AO) and the means antarctic oscillation (AAO) can be detected more obviously at the upper level of atmosphere than the AO or the AAO in surface layer. Unlike the hemisphere pattern of the AO and the AAO in the surface lager given by previous authors, the AO or the AAO in the stratosphere has its global features. The zonal oscillations-the Southern Oscillation (SO) and the north oscillation (NO) in atmospheric surface layer become less clear in the upper air. The first mode (AO mode, abbreviated to AOM hereafter) and the second mode (AAO mode, abbreviated to AAOM hereafter) respectively have 41.47% and 27.04% of the total variance contribution. The cumulative variance contribution of the first two modes reaches 68.51%. These two modes are the main components for the interdecadal or decadal oscillation in the stratosphere. In addition, there still exist two kinds of oscillation patterns with less probability,namely, the symmetric pattern at mid-high latitudes in the Southern Hemisphere and the asymmetric pattern. Spectral analysis shows that the AOM and the AAOM all have a spectral peak for 22 a period, being consistent with the periodic variations of the solar magnetic field, and a peak for 11 a period, being consistent with the period of the numbers of sunspots. Step filter analysis shows that the influencing factor for the upper atmospheric oscillation is the solar activity. The fluctuation of the solar magnetic field is the more influencing factor than the variation of the sunspot number.
2005, (6): 54-61.
Abstract:
On the basis of the investigated data for sea ice physical processes during the Second Chinese National Arctic Research Expedition (CHINARE-2003) in the summer of 2003, the sea ice dynamical characteristics were analyzed and the parameters describing these characteristics were given. The new findings discovered from these parameters are:(1) The ice concentration obtained from the investigation is two tenths to three tenths lower compared with that from the NOAA Ice Chart; and the ice thickness in the summer is 2 m less compared with the results obtained during the First Chinese National Arctic Research Expedition in 1999 (CHINARE-1999),(2) the standard deviation of the ice bottom fluctuation is 3.8 times that of the snow surface on the ice sheet; (3) the maximum speed of the ice floe on which camp CHIS7 is located (CHIS7 floe) is 1 300 m/h with rotation and oscillation. The rotation angle increased stepwise, the maximum being 37.8°, while the CHIS7 floe moved toward the north-east, and its rotation angle decreased stepwise.While the CHIS7 floe moved south-eastward. The oscillation period of CHIS7 floe is 12.45 h, which is consistent with that of the inertial current at the same latitude, showing the contribution of the inertial current to the ice floe movement.
On the basis of the investigated data for sea ice physical processes during the Second Chinese National Arctic Research Expedition (CHINARE-2003) in the summer of 2003, the sea ice dynamical characteristics were analyzed and the parameters describing these characteristics were given. The new findings discovered from these parameters are:(1) The ice concentration obtained from the investigation is two tenths to three tenths lower compared with that from the NOAA Ice Chart; and the ice thickness in the summer is 2 m less compared with the results obtained during the First Chinese National Arctic Research Expedition in 1999 (CHINARE-1999),(2) the standard deviation of the ice bottom fluctuation is 3.8 times that of the snow surface on the ice sheet; (3) the maximum speed of the ice floe on which camp CHIS7 is located (CHIS7 floe) is 1 300 m/h with rotation and oscillation. The rotation angle increased stepwise, the maximum being 37.8°, while the CHIS7 floe moved toward the north-east, and its rotation angle decreased stepwise.While the CHIS7 floe moved south-eastward. The oscillation period of CHIS7 floe is 12.45 h, which is consistent with that of the inertial current at the same latitude, showing the contribution of the inertial current to the ice floe movement.
2005, (6): 62-67.
Abstract:
On the basis of aerial photos of sea ice in the Second Chinese National Arctic Research Expdition during July and September 2003 in the area of 74.11°~79.56°N and 144.17°~169.95°W, image processing techniques are used to acquire some geometric parameters of floes, such as fractal dimension, roundness and mean caliper diameter. Latitudinal variation of morphology of arctic ice floes is then obtained, after comparing fractal dimension and roundness which represent geometry of floe edge, the latter is found to show a more obvious tendency with latitude but still not enough to describe floe abrasion. Then mean caliper diameter of ice floe is used as charac-teristic size to analyze floe size distribution, the result reveals that cumulative probabilities of floe sizes agree well with a power-law function, and distribution dimension is generally in the range of 1.05~1.25 and slightly increases as the latitude increases. However slight curvatures are still observed in the plots of cumulative probabilities as in former researches, which can be attributed to both the limitation of sampling area and effect of thermodynamic process.
On the basis of aerial photos of sea ice in the Second Chinese National Arctic Research Expdition during July and September 2003 in the area of 74.11°~79.56°N and 144.17°~169.95°W, image processing techniques are used to acquire some geometric parameters of floes, such as fractal dimension, roundness and mean caliper diameter. Latitudinal variation of morphology of arctic ice floes is then obtained, after comparing fractal dimension and roundness which represent geometry of floe edge, the latter is found to show a more obvious tendency with latitude but still not enough to describe floe abrasion. Then mean caliper diameter of ice floe is used as charac-teristic size to analyze floe size distribution, the result reveals that cumulative probabilities of floe sizes agree well with a power-law function, and distribution dimension is generally in the range of 1.05~1.25 and slightly increases as the latitude increases. However slight curvatures are still observed in the plots of cumulative probabilities as in former researches, which can be attributed to both the limitation of sampling area and effect of thermodynamic process.
2005, (6): 68-79.
Abstract:
The NASA Goddard Institute for Space Studies (GISS) coupled global climate model was used to investigate the sensitivity of sea ice to improved representations of sea-ice radiative processes:(1) a more sophisticated surface albedo scheme and (2) the penetration of solar radiation in sea ice. The results show that the large-scale sea-ice conditions are very sensitive to the aforementioned parameterizations. Although the more sophisticated surface albedo scheme produces a more realistic seasonal cycle of the surface albedo as compared with the baseline simulation, the resulting higher albedo relative to the baseline simulation generates much more and thicker ice in the arctic. The penetration of solar radiation in sea-ice itself tends to reduce the ice cover and thickness in the entire arctic and the western antarctic, and increase the ice cover and thickness in the eastern antarctic. The combination of (1) and (2) significantly improves the simulations of the average ice thickness and its spatial distribution in the arctic. The atmospheric responses associated with sea-ice changes were also discussed. While improvements are seen, particularly of the ice thickness distribution, there are still some unrealistic aspects that will require further improvements to the sea-ice component.
The NASA Goddard Institute for Space Studies (GISS) coupled global climate model was used to investigate the sensitivity of sea ice to improved representations of sea-ice radiative processes:(1) a more sophisticated surface albedo scheme and (2) the penetration of solar radiation in sea ice. The results show that the large-scale sea-ice conditions are very sensitive to the aforementioned parameterizations. Although the more sophisticated surface albedo scheme produces a more realistic seasonal cycle of the surface albedo as compared with the baseline simulation, the resulting higher albedo relative to the baseline simulation generates much more and thicker ice in the arctic. The penetration of solar radiation in sea-ice itself tends to reduce the ice cover and thickness in the entire arctic and the western antarctic, and increase the ice cover and thickness in the eastern antarctic. The combination of (1) and (2) significantly improves the simulations of the average ice thickness and its spatial distribution in the arctic. The atmospheric responses associated with sea-ice changes were also discussed. While improvements are seen, particularly of the ice thickness distribution, there are still some unrealistic aspects that will require further improvements to the sea-ice component.
2005, (6): 80-87.
Abstract:
Summer pack ice biotic community of the Canada Basin was characterized during the Second Chinese National Arctic Research Expedition (CHINARE-2003, 20 August-5 September 2003). Bacteria, ice algae (diatoms and autotrophic flagellates) and protozoa (mainly heterotrophic flagellates) were observed throughout the whole ice column. The vertical distribufon of biotic taxa varied among sites.The integrated biomass ranged from 48.4 and 58.1 mg/m2, with an average of 55.2 mg/m2. Bacteria were the dominant of the assem-blage in pack ice, accounted for 84.1% of the integrated, and ice algae, which usually dominate the ice biotic community, constituted only 3.5% of the total. Considering the quick environmental changes of the Arctic Ocean in recent years, we suggested that quick melting of pack ice in summer was suggested, which caused such change of pack ice biotic community. The low salinity throughout the whole ice column and the continuous melting of the pack ice cumbered the formation of ice algae bloom in summer, finally resulting in the dominance of microbial food web with bacteria and heterotrophic flagellates as the most obvious characteristics. Considering the high ratio of pack ice primary production to the total found in previous studies, the quick change of pack ice community structure in summer would deeply influence the marine ecosystem of the high Arctic Ocean.
Summer pack ice biotic community of the Canada Basin was characterized during the Second Chinese National Arctic Research Expedition (CHINARE-2003, 20 August-5 September 2003). Bacteria, ice algae (diatoms and autotrophic flagellates) and protozoa (mainly heterotrophic flagellates) were observed throughout the whole ice column. The vertical distribufon of biotic taxa varied among sites.The integrated biomass ranged from 48.4 and 58.1 mg/m2, with an average of 55.2 mg/m2. Bacteria were the dominant of the assem-blage in pack ice, accounted for 84.1% of the integrated, and ice algae, which usually dominate the ice biotic community, constituted only 3.5% of the total. Considering the quick environmental changes of the Arctic Ocean in recent years, we suggested that quick melting of pack ice in summer was suggested, which caused such change of pack ice biotic community. The low salinity throughout the whole ice column and the continuous melting of the pack ice cumbered the formation of ice algae bloom in summer, finally resulting in the dominance of microbial food web with bacteria and heterotrophic flagellates as the most obvious characteristics. Considering the high ratio of pack ice primary production to the total found in previous studies, the quick change of pack ice community structure in summer would deeply influence the marine ecosystem of the high Arctic Ocean.
2005, (6): 88-96.
Abstract:
The phenomenon of nutrient maximums at 70~200 m occurred only in the region of the Canada Basin among the world oceans. The prevailing hypothesis was that the direct injection of the low-temperature high-nutrient brines from the Chukchi Sea shelf (<50 m) in winter provided the nutrient maximums. However, we found that there are five problems in the direct injection process. Formerly Jin et al. considered that the formation of nutrient maximums can be a process of locally long-term regeneration. Here we propose a regeneration-mixture process. Data of temperature, salinity, oxygen and nutrients were collected at three stations in the southern Canada Basin during the summer 1999 cruise. We identified the cores of the surface, near-surface, potential temperature maximum waters and Arctic Bottom Water by the diagrams and vertical profiles of salinity, potential temperature, oxygen and nutrients. The historical 129Ⅰ data indicated that the surface and near-surface waters were Pacific-origin, but the waters below the potential temperature maximum core depth was Atlantic-origin. Along with the correlation of nutrient maximums and very low oxygen contents in the near-surface water, we hypothesize that, the putative organic matter was decomposed to inorganic nutrients; and the Pacific water was mixed with the Atlantic water in the transition zone. The idea of the regeneration-mixture process agrees with the historical observations of no apparent seasonal changes, the smooth nutrient profiles, the lowest saturation of CaCO3 above 400 m, low rate of CFC-11 ventilation and 3H-3He ages of 8~18 a around the nutrient maximum depths.
The phenomenon of nutrient maximums at 70~200 m occurred only in the region of the Canada Basin among the world oceans. The prevailing hypothesis was that the direct injection of the low-temperature high-nutrient brines from the Chukchi Sea shelf (<50 m) in winter provided the nutrient maximums. However, we found that there are five problems in the direct injection process. Formerly Jin et al. considered that the formation of nutrient maximums can be a process of locally long-term regeneration. Here we propose a regeneration-mixture process. Data of temperature, salinity, oxygen and nutrients were collected at three stations in the southern Canada Basin during the summer 1999 cruise. We identified the cores of the surface, near-surface, potential temperature maximum waters and Arctic Bottom Water by the diagrams and vertical profiles of salinity, potential temperature, oxygen and nutrients. The historical 129Ⅰ data indicated that the surface and near-surface waters were Pacific-origin, but the waters below the potential temperature maximum core depth was Atlantic-origin. Along with the correlation of nutrient maximums and very low oxygen contents in the near-surface water, we hypothesize that, the putative organic matter was decomposed to inorganic nutrients; and the Pacific water was mixed with the Atlantic water in the transition zone. The idea of the regeneration-mixture process agrees with the historical observations of no apparent seasonal changes, the smooth nutrient profiles, the lowest saturation of CaCO3 above 400 m, low rate of CFC-11 ventilation and 3H-3He ages of 8~18 a around the nutrient maximum depths.
2005, (6): 97-108.
Abstract:
In order to elucidate the regional export variation of particulate organic carbon in the western Arctic Ocean, samples vertically integrated between 0 and 100 m depth or between 0and 30 m/40 m depth were collected for total 234Th measurements and those from 30 m/40 m or 100 m depth were collected for particulate 234Th measurements during the Second Chinese Arctic Expedition in July-September 2003. The removal fluxes and residence time of 234Th in the upper water column were calculated by using irreversible steady-state scavenging model. The results showed that, total 234Th was deficit relative to its parent 238U in the western Arctic Ocean except in the western Chukchi shelf and the slope regions around 160°W, indicating that scavenging and removal processes play an important role in element biogeochemical cycle in the Arctic Ocean. In the western Chukchi shelfand the slope regions around 160°W,total 234Th was excess relative to 238U, ascribing to the horizontal input of 234Th adsorbed by ice-rafted sediments. Thorinm-234 removal fluxes decreased from the shelf to the deep ocean, while the residence time of 234Th increased from shelf to offshore, demonstrating that particle scavenging and removal processes are more active in the shelfregions. The estimated POC export fluxes from 40 m in the shelf regions and from 100 m in the slope and deep ocean varied between 1.6 and 27.5 mmol/(m2·d), and between 1.8 and 14.4 mmol/(m2·d), respectively. The averaged POC export fluxes over the entire water column decreased from the shelf to the deep ocean, indicating that the Chukchi shelf is an important region for organic carbon sequestration. The high ThE ratios (ratio of POC export flux derived from 234Th/238U disequilibria to primary production) in the western Arctic Ocean suggested that the biological pump runs actively in high-latitudes.
In order to elucidate the regional export variation of particulate organic carbon in the western Arctic Ocean, samples vertically integrated between 0 and 100 m depth or between 0and 30 m/40 m depth were collected for total 234Th measurements and those from 30 m/40 m or 100 m depth were collected for particulate 234Th measurements during the Second Chinese Arctic Expedition in July-September 2003. The removal fluxes and residence time of 234Th in the upper water column were calculated by using irreversible steady-state scavenging model. The results showed that, total 234Th was deficit relative to its parent 238U in the western Arctic Ocean except in the western Chukchi shelf and the slope regions around 160°W, indicating that scavenging and removal processes play an important role in element biogeochemical cycle in the Arctic Ocean. In the western Chukchi shelfand the slope regions around 160°W,total 234Th was excess relative to 238U, ascribing to the horizontal input of 234Th adsorbed by ice-rafted sediments. Thorinm-234 removal fluxes decreased from the shelf to the deep ocean, while the residence time of 234Th increased from shelf to offshore, demonstrating that particle scavenging and removal processes are more active in the shelfregions. The estimated POC export fluxes from 40 m in the shelf regions and from 100 m in the slope and deep ocean varied between 1.6 and 27.5 mmol/(m2·d), and between 1.8 and 14.4 mmol/(m2·d), respectively. The averaged POC export fluxes over the entire water column decreased from the shelf to the deep ocean, indicating that the Chukchi shelf is an important region for organic carbon sequestration. The high ThE ratios (ratio of POC export flux derived from 234Th/238U disequilibria to primary production) in the western Arctic Ocean suggested that the biological pump runs actively in high-latitudes.
2005, (6): 109-116.
Abstract:
Radium-224 activities in the western Arctic Ocean were measured via ship-board 220Rn emanation technique during the Second Chinese National Arctic Expedition. The results showed that the 224Ra activities in the study areas ranged from being less than 0.08 to 3.58 Bq/m3, with an average of 0.23 Bq/m3. The low 224Ra concentration in the surface water was attributed to the influence of sea ice melted water. The horizontal distribution of surface 224Ra in the western Arctic Ocean showed a high 224Ra characteristics occurred along the slope around 160°W, providing evidence for the importance of ice-rafted sediments to controlling the distribution of radium isotopes in the Arctic Ocean. Mostly, 224Ra concentrations increased with the depth in the shelf region and reached a maximum at 75 m at the central Canada Basin, which further confirms the importance of the transport of shelf bottom water to maintaining the upper halocline layer in the Canada Basin.
Radium-224 activities in the western Arctic Ocean were measured via ship-board 220Rn emanation technique during the Second Chinese National Arctic Expedition. The results showed that the 224Ra activities in the study areas ranged from being less than 0.08 to 3.58 Bq/m3, with an average of 0.23 Bq/m3. The low 224Ra concentration in the surface water was attributed to the influence of sea ice melted water. The horizontal distribution of surface 224Ra in the western Arctic Ocean showed a high 224Ra characteristics occurred along the slope around 160°W, providing evidence for the importance of ice-rafted sediments to controlling the distribution of radium isotopes in the Arctic Ocean. Mostly, 224Ra concentrations increased with the depth in the shelf region and reached a maximum at 75 m at the central Canada Basin, which further confirms the importance of the transport of shelf bottom water to maintaining the upper halocline layer in the Canada Basin.
2005, (6): 117-126.
Abstract:
Quantitative analytic results of the biogenic components in Core B2-9 from the northern Bering Sea slope indicate that the coarse fraction and opal content, serving as proxies of surface productivity, have increased stepwise since the marine isotope stage(MIS)5.3, reflecting periodic enhancement in surface productivity. The surface productivity attained its highest level during the Holocene, followed by MIS 3.2 to 2 and then MIS 5.3 to 3.3 with a lowest level. High total organic carbon(TOC) contents, together with high C/N ratios,which stand mostly between 7 and 20, show that the TOC was deposited from mixing sources. Therefore,one has to be cautious to use TOC as a proxy of surface productivity. The high TOC and C/N ratio during MIS 5.1, 3.3 to 3.2 and the Holocene reflect that the terrigenous organic matter input increased during interglacial periods. Increases in the fine-and silt-grained terrigenous components from MIS 5.3 to the middle Holocene imply that with the cooling climate, sea ice on the Bering Sea slope extended continuously. Ice-rafted and charcoal detritus increased during glacial, interstadial and the last deglaciation periods and decreased during interglacial periods,suggesting that sea ice on the slope increased and melted, respectively, during glacial and interglacial periods. The extension of sea ice during glacial periods,which was linked with the climate over the North American Continent, responded to global climate change during late Quaternary glacial and interglacial cycles.
Quantitative analytic results of the biogenic components in Core B2-9 from the northern Bering Sea slope indicate that the coarse fraction and opal content, serving as proxies of surface productivity, have increased stepwise since the marine isotope stage(MIS)5.3, reflecting periodic enhancement in surface productivity. The surface productivity attained its highest level during the Holocene, followed by MIS 3.2 to 2 and then MIS 5.3 to 3.3 with a lowest level. High total organic carbon(TOC) contents, together with high C/N ratios,which stand mostly between 7 and 20, show that the TOC was deposited from mixing sources. Therefore,one has to be cautious to use TOC as a proxy of surface productivity. The high TOC and C/N ratio during MIS 5.1, 3.3 to 3.2 and the Holocene reflect that the terrigenous organic matter input increased during interglacial periods. Increases in the fine-and silt-grained terrigenous components from MIS 5.3 to the middle Holocene imply that with the cooling climate, sea ice on the Bering Sea slope extended continuously. Ice-rafted and charcoal detritus increased during glacial, interstadial and the last deglaciation periods and decreased during interglacial periods,suggesting that sea ice on the slope increased and melted, respectively, during glacial and interglacial periods. The extension of sea ice during glacial periods,which was linked with the climate over the North American Continent, responded to global climate change during late Quaternary glacial and interglacial cycles.
2005, (6): 127-134.
Abstract:
Investigations of chlorophyll a and primary productivity were carried out in the Bering Sea along the BR line and the BS line during the Second Chinese National Arctic Research Expedition in the summer of 2003. The results showed that the surface chlorophyll a concentrations were 0.199~1.170 μg/dm3, and the average value was 0.723 μg/dm3 on the BR line. For the BS line, the surface chlorophyll a concentrations were 0.519~4.644 μg/dm3 (average 1.605 μg/dm3) and 0.568~14.968 μg/dm3 (average 5.311 μg/dm3)during the early and late summer, respectively. The average value in the late summer was much higher than that in the early summer.The high values (more than 4.0 μg/dm3) occurred at stations of the BS line in the southern Bering Strait. The chlorophyll a concentrations in the subsurface layer were higher than those in the surface layer. The results of the size-fractionated chlorophyll a showed that the contribution of the picoplankton to total chlorophyll a was the predominance at the early summer and the contribution of the netplankton was the predominance at the late summer. The carbon potential primary productivities varied between 0.471 and 1.147 mg/(m3·h) on the BR line, with average rates of 0.728 mg/(m3·h). The primary productivities on the BS line were much higher than those of the BR line, ranging from 1.227 mg/(m3·h) at the early summer to 19.046 mg/(m3·h) at the late summer. The results of 1.147 mg/(m3·h) on the BR line, with average rates of 0.728 mg/(m3·h). The primary productivities on the BS line were much higher than those of the BR line, ranging from 1.227 mg/(m3·h) at the early summer to 19.046 mg/(m3·h) at the late summer. The results of the size-fractionated primary productivity showed that the contribution of the nanoplankton to total productivity was the predominance at the early summer and the contribution of the netplankton was predominance at the late summer. The assimilation number of photosynthesis was 0.45~2.80 mg/(mg·h) in the surveyed stations.
Investigations of chlorophyll a and primary productivity were carried out in the Bering Sea along the BR line and the BS line during the Second Chinese National Arctic Research Expedition in the summer of 2003. The results showed that the surface chlorophyll a concentrations were 0.199~1.170 μg/dm3, and the average value was 0.723 μg/dm3 on the BR line. For the BS line, the surface chlorophyll a concentrations were 0.519~4.644 μg/dm3 (average 1.605 μg/dm3) and 0.568~14.968 μg/dm3 (average 5.311 μg/dm3)during the early and late summer, respectively. The average value in the late summer was much higher than that in the early summer.The high values (more than 4.0 μg/dm3) occurred at stations of the BS line in the southern Bering Strait. The chlorophyll a concentrations in the subsurface layer were higher than those in the surface layer. The results of the size-fractionated chlorophyll a showed that the contribution of the picoplankton to total chlorophyll a was the predominance at the early summer and the contribution of the netplankton was the predominance at the late summer. The carbon potential primary productivities varied between 0.471 and 1.147 mg/(m3·h) on the BR line, with average rates of 0.728 mg/(m3·h). The primary productivities on the BS line were much higher than those of the BR line, ranging from 1.227 mg/(m3·h) at the early summer to 19.046 mg/(m3·h) at the late summer. The results of 1.147 mg/(m3·h) on the BR line, with average rates of 0.728 mg/(m3·h). The primary productivities on the BS line were much higher than those of the BR line, ranging from 1.227 mg/(m3·h) at the early summer to 19.046 mg/(m3·h) at the late summer. The results of the size-fractionated primary productivity showed that the contribution of the nanoplankton to total productivity was the predominance at the early summer and the contribution of the netplankton was predominance at the late summer. The assimilation number of photosynthesis was 0.45~2.80 mg/(mg·h) in the surveyed stations.
2005, (6): 135-142.
Abstract:
Actinomycetes in five marine sediments collected from the Arctic Ocean at depths of 43 to 3 050 m were cultivated using a variety of media. A total of 61 actinomycete colonies with substrate mycelia only were observed, and no colonies with aerial mycelia were observed under aerobic conditions at 15℃. From these colonies, 28 were selected to represent different morphological types.Denaturing gradient gel electrophoresis (DGGE) was used to check the purity of isolates and select representatives for subsequent sequencing. Phylogentic analyses based on nearly full-length 16S ribosomal RNA gene (rDNA) sequences indicated that the actinomycetes isolated were accommodated within genus Rhodococcus of family Nocardiaceae, genus Dietzia of family Dietziaceae,genera Janibacter and Terrabacter of family Instrasporangiaceae and genera Kocuria and Arthrobacter of family Micrococcaceae. One of the strains (P27-24) from the deep-sea sediment at depth of 3 050 m was found to be identical in 16S rDNA sequence(1474/1474)with the radiation-resistant Kocuria rosea ATCC 187T isolated from air. More than halfofthe isolates showed the similarities ranging from 99.5% to 99.9% in 16S rDNA sequence to dibenzofran-degrading, butyl 2-ethylhexanoate-hydrolysising and nitrile-metabolizing actinomycetes. All the strains isolated were psychrotolerant bacteria and grew better on the media prepared with natural seawater than on the media prepared with deionized water. Three of them (Dietzia sp. P27-10, Rhodococcus sp. S11-3 and Rhodococcus sp.P11-5)had an obligate growth requirement for salt, confirming that these strains are indigenous marine actinomycetes.
Actinomycetes in five marine sediments collected from the Arctic Ocean at depths of 43 to 3 050 m were cultivated using a variety of media. A total of 61 actinomycete colonies with substrate mycelia only were observed, and no colonies with aerial mycelia were observed under aerobic conditions at 15℃. From these colonies, 28 were selected to represent different morphological types.Denaturing gradient gel electrophoresis (DGGE) was used to check the purity of isolates and select representatives for subsequent sequencing. Phylogentic analyses based on nearly full-length 16S ribosomal RNA gene (rDNA) sequences indicated that the actinomycetes isolated were accommodated within genus Rhodococcus of family Nocardiaceae, genus Dietzia of family Dietziaceae,genera Janibacter and Terrabacter of family Instrasporangiaceae and genera Kocuria and Arthrobacter of family Micrococcaceae. One of the strains (P27-24) from the deep-sea sediment at depth of 3 050 m was found to be identical in 16S rDNA sequence(1474/1474)with the radiation-resistant Kocuria rosea ATCC 187T isolated from air. More than halfofthe isolates showed the similarities ranging from 99.5% to 99.9% in 16S rDNA sequence to dibenzofran-degrading, butyl 2-ethylhexanoate-hydrolysising and nitrile-metabolizing actinomycetes. All the strains isolated were psychrotolerant bacteria and grew better on the media prepared with natural seawater than on the media prepared with deionized water. Three of them (Dietzia sp. P27-10, Rhodococcus sp. S11-3 and Rhodococcus sp.P11-5)had an obligate growth requirement for salt, confirming that these strains are indigenous marine actinomycetes.
2005, (6): 143-152.
Abstract:
Abundance and biomass of heterotrophic microbes were investigated using epifluorescense microscopy in August 2004 along a transect in the Kongsfjorden, a glacial fjord in the high arctic, located in the north-western part of Svalbard. A bacterial abundance was low at outer fjord stations (on average 2.29×108 ind./dm3) and was higher at inner fjord stations (on average 3.52×108 ind./dm3).The biomass of bacteria ranged from 3.69 to 8.01 mg/m3.The abundance of bacteria was low at the surface of water(0 m), whereas the higher abundances often occurred at depths of 30~50 m. The abundance of heterotrophic flagellates varied from 2.785 to 8.891×104 ind./dm3.The assemblage was numerically dominated by less than 5 μm heterotrophic flagellates (78.67%~94.80%).The biomass of heterotrophic flagellates varied from 0.37 to 2.30 mg/m3.The mean biomass distribution for all stations was 4.91% for less than 5 μm heterotrophic flagellates, 86.74% for 6~20 μm flagellates and 8.35% for greater than 20 μm sized flagellates.The lowbiomass of heterotrophic flagellates often occurred at the surface of water (0 m),while the maximum value of biomass occurred at different depths.The biomass of total heterotrophic microbial community ranged from 4.20 to 10.03 mg/m3.The mean biomass distribution for all stations was 82.58% for bacteria, 15.77% for flagellates and 1.66% for ciliates.
Abundance and biomass of heterotrophic microbes were investigated using epifluorescense microscopy in August 2004 along a transect in the Kongsfjorden, a glacial fjord in the high arctic, located in the north-western part of Svalbard. A bacterial abundance was low at outer fjord stations (on average 2.29×108 ind./dm3) and was higher at inner fjord stations (on average 3.52×108 ind./dm3).The biomass of bacteria ranged from 3.69 to 8.01 mg/m3.The abundance of bacteria was low at the surface of water(0 m), whereas the higher abundances often occurred at depths of 30~50 m. The abundance of heterotrophic flagellates varied from 2.785 to 8.891×104 ind./dm3.The assemblage was numerically dominated by less than 5 μm heterotrophic flagellates (78.67%~94.80%).The biomass of heterotrophic flagellates varied from 0.37 to 2.30 mg/m3.The mean biomass distribution for all stations was 4.91% for less than 5 μm heterotrophic flagellates, 86.74% for 6~20 μm flagellates and 8.35% for greater than 20 μm sized flagellates.The lowbiomass of heterotrophic flagellates often occurred at the surface of water (0 m),while the maximum value of biomass occurred at different depths.The biomass of total heterotrophic microbial community ranged from 4.20 to 10.03 mg/m3.The mean biomass distribution for all stations was 82.58% for bacteria, 15.77% for flagellates and 1.66% for ciliates.
2005, (6): 153-161.
Abstract:
PCR-DGGE approach was used to analyze bacterial diversity in the bottom section of seven arctic sea ice samples colleted from the Canada Basin. Thirty-two 16S rDNA sequences were obtained from prominent DGGE bands. The closest relatives of these sequences are found to be those of cultivated or uncultured bacteria from antarctic or arctic sea ice. Phylogenetic analysis clustered these sequences or phylotypes within α-proteobacteria, γ-proteobacteria and CFB (cytophaga-flexibacter-bacteroides) group. Sequences belonging to γ-proteobacteria were dominant and members of the CFB group were highly abundant. It was suggested that the CFB group was the representative of the bottom section of sea ice samples.
PCR-DGGE approach was used to analyze bacterial diversity in the bottom section of seven arctic sea ice samples colleted from the Canada Basin. Thirty-two 16S rDNA sequences were obtained from prominent DGGE bands. The closest relatives of these sequences are found to be those of cultivated or uncultured bacteria from antarctic or arctic sea ice. Phylogenetic analysis clustered these sequences or phylotypes within α-proteobacteria, γ-proteobacteria and CFB (cytophaga-flexibacter-bacteroides) group. Sequences belonging to γ-proteobacteria were dominant and members of the CFB group were highly abundant. It was suggested that the CFB group was the representative of the bottom section of sea ice samples.
2005, (6): 162-171.
Abstract:
Aerosol samples were collected on board the research vessel Xuelong during the Fifteenth Chinese Antarctic Research Expedition (CHINARE XV) in November 1998-April 1999 and the First Chinese Arctic Research Expedition in July-September 1999.The areas traversed by the expeditionary cruises include the Arctic Ocean, the western North Pacific Ocean and the eastern Indian Ocean,covering 75°N-69°S and 75°E-133°W. Aerosol samples were also taken at the Chinese Zhongshan Station in East Antarctica during the CHINARE XV. Analysis of the samples yielded concentrations of non-sea-salt sulfate and other soluble chemical species in the marine boundary layer. The data suggest that the chemical composition of the marine aerosols is influenced by three major sources:continental air masses, primary oceanic emissions, and secondary marine aerosols originated from oceanic emissions. The results show that, awing to strong anthropogenic sulfur emissions from the Asian continent, non-sea-salt sulfate concentrations in the Northern Hemisphere (the western North Pacific) marine aerosol are significantly higher than those in the Southern Hemisphere (the eastern Indian Ocean). Aerosol non-sea-salt sulfate concentrations appear to be inversely correlated with aerosol non-sea-salt chloride which shows significantly negative values, indicating the loss of chloride by sea salts, in most aerosol samples. Since gaseous HCl may be involved in chemical reactions that deplete atmospheric ozone in the marine boundary layer (MBL), high levels of acidic non-sea-salt-sulfate released by human activities in the low and mid-latitudes of the Northern Hemisphere may become an important potential contributor to the loss of atmospheric ozone in the MBL.
Aerosol samples were collected on board the research vessel Xuelong during the Fifteenth Chinese Antarctic Research Expedition (CHINARE XV) in November 1998-April 1999 and the First Chinese Arctic Research Expedition in July-September 1999.The areas traversed by the expeditionary cruises include the Arctic Ocean, the western North Pacific Ocean and the eastern Indian Ocean,covering 75°N-69°S and 75°E-133°W. Aerosol samples were also taken at the Chinese Zhongshan Station in East Antarctica during the CHINARE XV. Analysis of the samples yielded concentrations of non-sea-salt sulfate and other soluble chemical species in the marine boundary layer. The data suggest that the chemical composition of the marine aerosols is influenced by three major sources:continental air masses, primary oceanic emissions, and secondary marine aerosols originated from oceanic emissions. The results show that, awing to strong anthropogenic sulfur emissions from the Asian continent, non-sea-salt sulfate concentrations in the Northern Hemisphere (the western North Pacific) marine aerosol are significantly higher than those in the Southern Hemisphere (the eastern Indian Ocean). Aerosol non-sea-salt sulfate concentrations appear to be inversely correlated with aerosol non-sea-salt chloride which shows significantly negative values, indicating the loss of chloride by sea salts, in most aerosol samples. Since gaseous HCl may be involved in chemical reactions that deplete atmospheric ozone in the marine boundary layer (MBL), high levels of acidic non-sea-salt-sulfate released by human activities in the low and mid-latitudes of the Northern Hemisphere may become an important potential contributor to the loss of atmospheric ozone in the MBL.
