Ice extent in the Greenland Sea 1978–1995     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(6-7):1237-1254

During the European Subpolar Ocean Programme (ESOP) project from 1993 to 1995, very little ice was formed in the central Greenland Sea. The large-scale ice cover in the area during the period October 1978 to June 1995 has been mapped using passive microwave data from the scanning multichannel microwave radiometer (SMMR) and the special sensor microwave/imager (SSM/I). Special emphasis is put on the last three years of the period (the ESOP years), from the summer of 1992 to the summer of 1995. The results for the three winters compared with the average winter of the previous 12 yr show unusually little ice in the Greenland Sea during the winters of 1993–1995. In particular, the winters of 1994 and 1995 saw no ice (i.e. no Odden) in the central Greenland Sea at all. Another result is an observed upper limit of approximately 250,000 km² to the seasonal ice cover in the study region (the Odden Area) within the central Greenland Sea over the period 1978–1995.  相似文献   

Ice–ocean interactions during shallow convection under conditions of steady winds: three-dimensional numerical studies     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(6-7):1335-1355

A three-dimensional hydrodynamic ocean model coupled to a thermohydrodynamic model for young sea ice is applied to study shallow haline convection in the central Greenland Sea, with an emphasis on sub-mesoscale ice–ocean interactions. Two types of young sea ice are distinguished; i.e., frazil and pancake ice, both acting different on surface heat, salt, and momentum fluxes. Two scenarios are considered: (a) continued frazil-ice production during steady winds, and (b) the same scenario but with the intermittent formation of pancake ice during a short intervening period of low winds. Brine release due to new-ice production creates shallow convection in both cases. Under conditions of continued frazil-ice production, ice streaks develop at the sea surface, finally becoming oriented roughly parallel to the wind. These streaks are the result of convective plumes that induce organized patterns of convergent and divergent surface currents. Frazil-ice is herded into convergence zones where it becomes as thick as 6 m within 24 h. The studies suggest a strong relationship between streak spacing and the penetration depth of convection, given by an aspect ratio in the range of 2–3. After pancake ice has been formed, however, the organized ice streaks vanish, developing into complex patterns of pancake ice. This finding is in agreement with recent field observations in the Greenland Sea Is-Odden ice tongue. With the existence of pancake ice, moreover, the surface-averaged buoyancy flux decreases and is determined from the integral of local sub-mesoscale ice–ocean interactions.  相似文献   

High primary productivity and f-ratio in summer in the Ulleung basin of the East/Japan Sea     

《Deep Sea Research Part I: Oceanographic Research Papers》2013

To better understand the cause of high summer primary productivity in the Ulleung Basin located in the southwest part of the East/Japan Sea, the spatial dynamics of primary, new, and regenerated productivities (PP, NP, and RP) were examined along the path of the Tsushima Warm Current system in summer 2008. We compared hydrographic and chemical parameters in the Ulleung Basin with those of the Kuroshio Current in the Western Pacific Ocean and the East China Sea. In summer, integrated primary productivity (IPP, 0.37–0.96 g C m⁻² d⁻¹) and integrated new productivity (INP, 26–221 mg N m⁻² d⁻¹) within the euphotic zone in the Ulleung Basin were higher than those in the East China Sea and the Western Pacific Ocean (0.17–0.28 g C m⁻² d⁻¹, 2−5 mg N m⁻² d⁻¹, respectively). In contrast, there was no pronounced spatial variation in integrated regenerated productivity (IRP, 43–824 mg N m⁻² d⁻¹). Strong positive correlations between IPP and INP (also the f-ratio), and between nitrate uptake rate in the mixed layer and nitrate upward flux through the top of pycnocline in summer in the Ulleung Basin imply that the high IPP was mainly supported by supply of nitrate from the underlying water in the euphotic zone. Shallowing of the pycnocline depth as the current enters the East/Japan Sea facilitates nitrate supply from the nutrient-replete cold water immediately below the pycnocline through nitrate upward flux. A subsurface maximum in PP at or above the pycnocline and a high f-ratio further support the importance of this source of nitrate for maintaining the high summer PP in the Ulleung Basin. In comparison, the high PP layer was observed at the surface in the following fall and spring in the Ulleung Basin. Our results demonstrate the importance of hydrographic features in enhancing PP in this oligotrophic Tsushima Warm Current system.  相似文献   

Mapping of ice in the Odden by satellite and airborne remote sensing     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(6-7):1255-1274

A detailed analysis of the ice conditions in the Odden area of the Greenland Sea was carried out using data from active and passive microwave sensors, supplemented by airborne data. The study focuses on the 1992–1993 winter season, the only winter during the period 1993–1995 in which an Odden feature formed. The analysis is structured as a hierarchy of spatial resolutions where the overview is obtained by the DMSP SSM/I microwave radiometers having spatial resolutions in the 15–50 km range. Further details in cloud-free situations are obtained by data from the NOAA advanced very high resolution radiometer, which is a scanner in the visible, near-infrared and thermal infrared range with a resolution of 1.1 km. The finest resolution of 25 m per pixel is obtained from the synthetic aperture radar on the ERS-1 satellite.  相似文献   

Abundance,biomass and composition of the sea ice biota of the Greenland Sea pack ice     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(6-7):1457-1472

During two cruises to the Greenland Sea, we studied the abundance and biomass of the sea ice biota in summer and late autumn. The mean calculated biomass of the sympagic community was 0.2 g C m⁻² ice. Algae contributed on average 43% to total biomass, followed by bacteria (31%), heterotrophic flagellates (20%), and meiofauna (4%). Diatoms were the main primary producers (60% of total algal biomass), but flagellated cells contributed significantly to the algal biomass. Among the meiofauna, ciliates, nematodes, acoel turbellarians and crustaceans were dominant. Calculated potential ingestion rates of meiofauna (0.6 g C m⁻² (120 d)⁻¹) are on the same order of magnitude as annual primary production estimates for Arctic multi-year sea ice. We therefore assume that grazing can control biomass accumulation of primary producers inside the sea ice.  相似文献   

Fate of biogenic carbon in the upper 200 m of the central Greenland Sea     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(6-7):1497-1509

Sedimentation of particulate carbon from the upper 200–300 m in the central Greenland Sea from August 1993 to June 1995 was less than 2 g C m⁻² yr⁻¹. Daily rates of sedimentation of particulate organic carbon reached highest values of about 18 mg m⁻² d⁻¹ in fall 1994. For total particulate material, maximum rates of sedimentation of about 250 mg m⁻² d⁻¹ were recorded in spring and fall 1994. For chlorophyll equivalent, highest rates of sedimentation of about 140 μg m⁻² d⁻¹ were recorded in spring 1994. As reported in related investigations, the transient accumulation of DOC in surface waters during summer, as well as respiration and mortality of deep overwintering zooplankton stocks, appeared to dominate the fate of photosynthetically fixed organic carbon. The above processes may account for roughly 43 g C m⁻² in the upper 200 m of the central Greenland Sea. For comparison, the seasonal deficit in dissolved inorganic carbon was reported to be about 23 g C m⁻² in the upper 20 m of surface water, and estimates for new annual production were reported to be about 57 g C m⁻². In our investigation, the biological carbon pump was not unusually effective in transporting carbon out of the productive surface layer.  相似文献   

Modelling the carbon export and air–sea flux of CO2 in the Greenland Sea     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(6-7):1511-1530

We have developed a 3D model for the carbon cycle and air–sea flux of CO₂ in the Greenland Sea that consists of three submodels for hydrodynamics, carbon chemistry and plankton ecology. The hydrodynamical model, based on the primitive Navier–Stokes equations, simulates the physical environment that is used for the chemical and biological models. The chemical model calculates the pCO₂ as a function of the total inorganic carbon, alkalinity, temperature and salinity. The ecological model has eight state variables and simulates the transformation of CO₂ into organic carbon, vertical transport, and the respiration processes that convert the organic carbon back into inorganic form. The model gives an average annual primary production of 68 g C m⁻² y⁻¹, of which 44.7 g C m⁻² y⁻¹ is new production. In the eastern part of the Greenland Sea, the average annual new production is above 50 g C m⁻² y⁻¹. Simulated, annual flux of CO₂ from the atmosphere is 53 g C m⁻² y⁻¹, which sums up to 0.026 Gt for the whole Greenland Sea. Of this, 9 g C m⁻² y⁻¹ is exported by sinking particles, 6 g C m⁻² y⁻¹ by migrating zooplankton (mainly Calanus hyperboreus), and 38 g C m⁻² y⁻¹ by advection.  相似文献   

Seasonal dynamics of primary and new production in the northern South China Sea: The significance of river discharge and nutrient advection     

《Deep Sea Research Part I: Oceanographic Research Papers》2006,53(6):971-986

Biochemical and productivity measurements and nutrient enrichment experiments were conducted on three cruises in summer and two cruises in winter on the shelf and the basin of the northern South China Sea (SCS) between 2001 and 2004. Phytoplankton production, in terms of depth-integrated new production (INP) or depth-integrated primary production (IPP), was higher in winter than in summer and on the shelf than in the basin. In winter, with deepening of the mixed layer, nitrate from the shallow nitracline that characterized the SCS waters was made available in the surface and supported the highest production of the year. Averaged INP measured in winter (0.25 g C m⁻² d⁻¹) was about twice the summer average (0.12 g C m⁻² d⁻¹) and was 0.19 g C m⁻² d⁻¹ on the shelf compared with 0.15 g C m⁻² d⁻¹ in the basin. In winter, average INP on the shelf was higher than the basin (0.34 versus 0.21 g C m⁻² d⁻¹); whereas in summer, averaged INP on the shelf (0.13 g C m⁻² d⁻¹) and the basin (0.11 g C m⁻² d⁻¹) were similar. While averaged IPP measured in the basin was higher in winter than in summer (0.53 versus 0.35 g C m⁻² d⁻¹), IPP on the shelf showed little temporal variation (0.82 in winter versus 0.84 g C m⁻² d⁻¹ in summer). Considerable spatial and inter-annual variation in production was measured in the shelf waters during summer, which could be linked to discharge volume and plume flow direction of the Zhujiang River. While the shelf waters in summer were mostly nitrogen starved or nitrogen and phosphorus co-limited, excessive river runoff may cause the nutritive state to shift to phosphorus deficiency. Waters with low surface salinities and high fluorescence from riverine mixing could be found extending from the Zhujiang mouth to as far as offshore southern Taiwan after a typhoon passed the northern SCS and brought heavy rainfall. Overall, both nutrient advection in winter and river discharge from the China coast in summer made new nitrogen available and shaped the dynamics of phytoplankton production in these oligotrophic waters.  相似文献   

An inverse modeling study in Fram Strait. Part II: Water mass distribution and transports     

《Deep Sea Research Part II: Topical Studies in Oceanography》1999,46(6-7):1137-1168

A water-mass analysis is carried out in Fram Strait, between 77.15 and 81.15°N, based on three-dimensional large-scale potential temperature and salinity distributions reconstructed from the MIZEX 84 hydrographic data collected in summer 1984. Combining these distributions with the geostrophic flow field derived from the same data in a companion paper (Schlichtholz and Houssais, 1999), the heat, fresh water and volume transports are estimated for each of the water masses identified in the strait. Twelve water masses are selected based on their different origins. Among them, the Polar Water (PW) enters Fram Strait from the Arctic Ocean both over the Greenland Slope and over the western slope of the Yermak Plateau. In the Atlantic Water (AW) range, four modes with distinct geographical distributions are indentified. In the Deep Water range, the Eurasian Basin Deep Water (EBDW) is confined to the Lena Trough and to the Molloy Deep area where it is involved in a cyclonic circulation. The warm and shallower mode of the Norwegian Sea Deep Water (NSDW), concentrated to the west, is mainly seen as an outflow from the Arctic Ocean while the cold and deeper mode, essentially observed to the east, enters the strait from the Greenland Sea. Apart from the EBDW, there is a tendency for all water masses of polar origin to flow along the Greenland Slope. The two most abundant water masses, the AW and the NSDW, occupy as much as 67% of the total water volume. The southward net transport of PW through Fram Strait is about 1 Sv at 78.9°N. At the same latitude, the net transport of AW is southward and equal to about 1.7 Sv. Only the transport of the warm mode (AWw) is northward, amounting to 0.2 Sv. The overall net outflow of the Deep Waters to the Greenland Sea is about 2.6 Sv. Two upper water masses, the fresh (AWf) and the cold (AWc) mode of the AW, and one deep-water mass, the NSDW, appear to be produced in the strait, with production rates, between 77.6 and 79.9°N, of about 0.2, 1.0 and 1.7 Sv, respectively. A southward net fresh-water transport through the strait of about 2000 km³ yr⁻¹ (relative to a salinity of 34.93) is mainly due to the PW. The net heat transport relative to −0.1°C is northward, but undergoes a rapid northward decrease, suggesting an area-averaged surface heat loss of 50–100 W m⁻² in the strait.  相似文献   

Organic carbon flux and remineralization in surface sediments from the northern North Atlantic derived from pore-water oxygen microprofiles     

《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(2):529-553

Organic carbon fluxes through the sediment/water interface in the high-latitude North Atlantic were calculated from oxygen microprofiles. A wire-operated in situ oxygen bottom profiler was deployed, and oxygen profiles were also measured onboard (ex situ). Diffusive oxygen fluxes, obtained by fitting exponential functions to the oxygen profiles, were translated into organic carbon fluxes and organic carbon degradation rates. The mean C_org input to the abyssal plain sediments of the Norwegian and Greenland Seas was found to be 1.9 mg C m⁻² d⁻¹. Typical values at the seasonally ice-covered East Greenland continental margin are between 1.3 and 10.9 mg C m⁻² d⁻¹ (mean 3.7 mg C m⁻² d⁻¹), whereas fluxes on the East Greenland shelf are considerably higher, 9.1–22.5 mg C m⁻² d⁻¹. On the Norwegian continental slope C_org fluxes of 3.3–13.9 mg C m⁻² d⁻¹ (mean 6.5 mg C m⁻² d⁻¹) were found. Fluxes are considerably higher here compared to stations on the East Greenland slope at similar water depths. By repeated occupation of three sites off southern Norway in 1997 the temporal variability of diffusive O₂ fluxes was found to be quite low. The seasonal signal of primary and export production from the upper water column appears to be strongly damped at the seafloor. Degradation rates of 0.004–1.1 mg C cm⁻³ a⁻¹ at the sediment surface were calculated from the oxygen profiles. First-order degradation constants, obtained from C_org degradation rates and sediment organic carbon content, are in the range 0.03–0.6 a⁻¹. Thus, the corresponding mean lifetime of organic carbon lies between 1.7 and 33.2 years, which also suggests that seasonal variations in C_org flux are small. The data presented here characterize the Norwegian and Greenland Seas as oligotrophic and relatively low organic carbon deep-sea environments.  相似文献   

Community respiration/production and bacterial activity in the upper water column of the central Arctic Ocean     

《Deep Sea Research Part I: Oceanographic Research Papers》2003,50(4):529-542

Community metabolism (respiration and production) and bacterial activity were assessed in the upper water column of the central Arctic Ocean during the SHEBA/JOIS ice camp experiment, October 1997–September 1998. In the upper 50 m, decrease in integrated dissolved oxygen (DO) stocks over a period of 124 d in mid-winter suggested a respiration rate of ∼3.3 nM O₂ h⁻¹ and a carbon demand of ∼4.5 gC m⁻². Increase in 0–50 m integrated stocks of DO during summer implied a net community production of ∼20 gC m⁻². Community respiration rates were directly measured via rate of decrease in DO in whole seawater during 72-h dark incubation experiments. Incubation-based respiration rates were on average 3-fold lower during winter (11.0±10.6 nM O₂ h⁻¹) compared to summer (35.3±24.8 nM O₂ h⁻¹). Bacterial heterotrophic activity responded strongly, without noticeable lag, to phytoplankton growth. Rate of leucine incorporation by bacteria (a proxy for protein synthesis and cell growth) increased ∼10-fold, and the cell-specific rate of leucine incorporation ∼5-fold, from winter to summer. Rates of production of bacterial biomass in the upper 50 m were, however, low compared to other oceanic regions, averaging 0.52±0.47 ngC l⁻¹ h⁻¹ during winter and 5.1±3.1 ngC l⁻¹ h⁻¹ during summer. Total carbon demand based on respiration experiments averaged 2.4±2.3 mgC m⁻³ d⁻¹ in winter and 7.8±5.5 mgC m⁻³ d⁻¹ in summer. Estimated bacterial carbon demand based on bacterial productivity and an assumed 10% gross growth efficiency was much lower, averaging about 0.12±0.12 mgC m⁻³ d⁻¹ in winter and 1.3±0.7 mgC m⁻³ d⁻¹ in summer. Our estimates of bacterial activity during summer were an order of magnitude less than rates reported from a summer 1994 study in the central Arctic Ocean, implying significant inter-annual variability of microbial processes in this region.  相似文献   

Primary productivity,differential size fraction and pigment composition responses in two Southern Ocean in situ iron enrichments     

《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(5):747-773

Two in situ iron-enrichment experiments were conducted in the Pacific sector of the Southern Ocean during summer 2002 (SOFeX). The “north patch,” established within the Subantarctic Zone (∼56°S), was characterized by high nitrate (∼21 mmol m⁻³) but low silicic acid (2 mmol m⁻³) concentrations. North patch iron enrichment increased chlorophyll (Chl) by 12-fold to 2.1 mg m⁻³ and primary productivity (PP_EU) by 8-fold to 188 mmol C m⁻² d⁻¹. Surprisingly, despite low silicic acid concentrations, diagnostic pigment and size-fraction composition changes indicated an assemblage shift from prymnesiophytes toward diatoms. The “south patch,” poleward of the Southern Boundary of the Antarctic Circumpolar Current (SBACC) (∼66°S), had high concentrations of nitrate (∼27 mmol m⁻³) and silicic acid (64 mmol m⁻³). South patch iron enrichment increased Chl by 9-fold to 3.8 mg m⁻³ and PP_EU 5-fold to 161 mmol C m⁻² d⁻¹ but, notably, did not alter the phytoplankton assemblage from the initial composition of ∼50% diatoms. South patch iron addition also reduced total particulate organic carbon:Chl from ∼300 to 100; enhanced the presence of novel non-photosynthetic, but fluorescent, compounds; and counteracted a decrease in photosynthetic performance as photoperiod decreased. These experiments show unambiguously that in the contemporary, high nitrate Southern Ocean increasing iron supply increases primary productivity, confirming the initial premise of the Martin Iron Hypothesis. However, despite a 5-fold increase in PP_EU under iron-replete conditions in late summer, the effect of iron on annual productivity in the Southern Ocean poleward of the SBACC is limited by seasonal ice coverage and the dark of polar winter.  相似文献   

Microbial respiration in the Levantine Sea: evolution of the oxidative processes in relation to the main Mediterranean water masses     

《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(10):2147-2159

First data on microbial respiration in the Levantine Sea are reported with the aim of assessing the distribution of oxidative processes in association with the main Mediterranean water masses and the changing physical structure determined by the Eastern Mediterranean Transient. Respiratory rates, in terms of metabolic carbon dioxide production, were estimated from measured electron transport system activities in the polygonal area of the Levantine Sea (32.5–36.5 N Latitude, 26.0–30.25 E Longitude) and at Station Geo’95, in the Ionian Sea (35°34.88 N; 17°14.99 E). At the Levantine Sea, the mean carbon dioxide production rate decreased from the upper to the deeper layers and varied from 22.0±12.4 μg C h⁻¹ m⁻³ in the euphotic layer to 1.30±0.5 μg C h⁻¹ m⁻³ in the depth range between 1600 and 3000 m. Significant differences were found among upper, intermediate and bottom layers. The euphotic zone supported a daily carbon dioxide production of 96.6 mg C d⁻¹ m⁻² while the aphotic zone (between 200 and 3000 m) sustained a 177.1 mg C d⁻¹ m⁻² carbon dioxide production. In Station Geo’95, the carbon dioxide production rates amounted to 170.4 and 102.2 mg C d⁻¹ m⁻² in the euphotic and aphotic zones, respectively. The rates determined in the identified water masses showed a tight coupling of respiratory processes and Mediterranean circulation patterns. The increasing respiratory rates in the deep layers of the Levantine Sea are explained by the introduction of younger waters recently formed in the Aegean Sea.  相似文献   

Sea-ice algae: Major contributors to primary production and algal biomass in the Chukchi and Beaufort Seas during May/June 2002     

《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(17):1201-1212

Sea-ice and water samples were collected at 14 stations on the shelves and slope regions of the Chukchi and Beaufort Seas during the spring 2002 expedition as part of the Shelf–Basin Interaction Studies. Algal pigment content, particulate organic carbon and nitrogen, and primary productivity were estimated for both habitats based on ice cores, brine collection and water samples from 5-m depth. The pigment content (0.2–304.3 mg pigments m⁻²) and primary productivity (0.1–23.0 mg C m⁻³ h⁻¹) of the sea-ice algae significantly exceeded water-column parameters (0.2 and 1.0 mg pigments m⁻³; <0.1–0.4 mg C m⁻³ h⁻¹), making sea ice the habitat with the highest food availability for herbivores in early spring in the Chukchi and Beaufort Seas. Stable isotope signatures for ice and water samples did not differ significantly for δ¹⁵N, but for δ¹³C (ice: −25.1‰ to −14.2‰; water: −26.1‰ to −22.4‰). The analysis of nutrient concentrations and the pulse-amplitude-modulated fluorescence signal of ice algae and phytoplankton indicate that nutrients were the prime limiting factor for sea-ice algal productivity. The estimated spring primary production of about 1–2 g C m⁻² of sea-ice algae on the shelves requires the use of substantial nutrient reservoirs from the water column.  相似文献   

Net community production in the northeastern Chukchi Sea     

《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(17):1213-1222

To assess the magnitude, distribution and fate of net community production (NCP) in the Chukchi Sea, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), and particulate organic carbon (POC) and particulate organic nitrogen (PON) were measured during the spring and summer of 2004 and compared to similar observations taken in 2002. Distinctive differences in hydrographic conditions were observed between these two years, allowing us to consider several factors that could impact NCP and carbon cycling in both the Chukchi Shelf and the adjacent Canada Basin. Between the spring and summer cruises high rates of phytoplankton production over the Chukchi shelf resulted in a significant drawdown of DIC in the mixed layer and the associated production of DOC/N and POC/N. As in 2002, the highest rates of NCP occurred over the northeastern part of the Chukchi shelf near the head of Barrow Canyon, which has historically been a hotspot for biological activity in the region. However, in 2004, rates of NCP over most of the northeastern shelf were similar and in some cases higher than rates observed in 2002. This was unexpected due to a greater influence of low-nutrient waters from the Alaskan Coastal Current in 2004, which should have suppressed rates of NCP compared to 2002. Between spring and summer of 2004, normalized concentrations of DIC in the mixed layer decreased by as much as 280 μmol kg⁻¹, while DOC and DON increased by ∼16 and 9 μmol kg⁻¹, respectively. Given the decreased availability of inorganic nutrients in 2004, rates of NCP could be attributed to increased light penetration, which may have allowed phytoplankton to increase utilization of nutrients deeper in the water column. In addition, there was a rapid and extensive retreat of the ice cover in summer 2004 with warmer temperatures in the mixed layer that could have enhanced NCP. Estimates of NCP near the head of Barrow Canyon in 2004 were ∼1500 mg carbon (C) m⁻² d⁻¹ which was ∼400 mg C m⁻² d⁻¹ higher than the same location in 2002. Estimates of NCP over the shelf-break and deep Canada Basin were low in both years, confirming that there is little primary production in the interior of the western Arctic Ocean due to near-zero concentrations of inorganic nitrate in the mixed layer.  相似文献   

Structure of potential upwelling areas in the Philippines     

《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(6):1499-1518

The three-dimensional structure of two potential mesoscale upwelling areas that are located in the external waters of the Philippine archipelago (i.e. northwest of Luzon and east of Mindanao) were constructed by analysis of historical data. A unique characteristic of both upwelling sites is that they can be identified by their anomalously cold subsurface temperatures rather than sea surface temperature distributions. As such, they cannot be observed in sea surface temperature fields derived by satellite imagery. The data used in the analysis were obtained from the National Oceanographic Data Center hydrographic database. Objective analysis was performed to produce monthly temperature fields at several standard depths within the upper 500 m of the region 0–30°N and 100–140°E with a horizontal grid resolution of 0.5°. The extent and timing of these upwelling areas are described. A review of existing hypothesis on the mechanisms for their evolution and seasonal modulation are presented. The change in heat content during the upwelling season is greater than 300 W m⁻² in both areas. Based on the excursion of isotherms, vertical velocities of 83 cm day⁻¹ and 26 cm day⁻¹ were obtained for upwelling northwest of Luzon and east of Mindanao, respectively.  相似文献   

Resuspension and particle transport in the benthic nepheloid layer in and near Fram Strait in relation to faunal abundances and 234Th depletion     

《Deep Sea Research Part I: Oceanographic Research Papers》2002,49(11):1941-1958

The West Spitsbergen Current, flowing northward through Fram Strait, causes a benthic nepheloid layer (BNL) on the western slope of the Yermak Plateau. This BNL is weaker on the eastern side of the Plateau and absent on the Greenland side of the Fram Strait, where the East Greenland Current flows south. In this BNL we find throughout a depletion of ²³⁴Th relative to its parent ²³⁸U, and we use this to study the particle dynamics in the BNL. The export flux from the ice-covered surface ocean and from a young bloom found in the ice-free waters off NE Greenland is shown to be negligible, allowing us to explain the ²³⁴Th depletion by interaction with the sediment alone. The depletion, balanced by a similar excess in the surface layer of the sediment, implies the existence of a settling-resuspension loop with an average particle residence time of 1–2 months. The asymmetry with a stronger resuspension loop on the western (80–120 mg m⁻² d⁻¹) than on the eastern side of the Yermak Plateau (1–15 mg m⁻² d⁻¹) is reflected in the numbers of species and individuals of suspension feeders in box core samples, and in epifauna densities estimated from video observations. The suspension feeders thus contribute to deposition of particles that are advected from more productive ice-free regions. This explanation is in agreement with the east–west asymmetry in the input of organic material to the sediments of the Yermak Plateau, which has been concluded from the distribution of pigments, bacterial activity and meiofauna abundances, observed in a concurrent study at the same stations. On the West Spitsbergen shelf, a very intensive BNL was monitored over 1 month with a moored filtration system. A part of the sustained high suspended load may be advected over long distances. This study illustrates how the tracer ²³⁴Th can help to determine the extent to which suspended particles are in continuous exchange with the seafloor, and where biological mediation and chemical modification can be expected.  相似文献   

Phytoplankton of the western Arctic in the spring and summer of 2002: Structure and seasonal changes     

《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(17):1223-1236

We analyzed the taxonomic structure and spatial variability of phytoplankton abundance and biomass in the Chukchi and Beaufort Seas during spring and summer seasons of the SBI program. Phytoplankton samples were collected during two surveys from May 10 to June 13 and from July 19 to August 21 of 2002. In May and June, ice cover exceeded 80% over most of the study area and there was no vertical stratification, indicating that the successional state of the phytoplankton corresponded to the end of the winter biological season. The phytoplankton abundance ranged from a few tens to a few thousands of cells per liter, while biomass varied from 0.1 to 3.0 mg C m⁻³. Small areas of high phytoplankton abundance (0.13–1.3×10⁶ cells L⁻¹) and biomass (22–536 mg C m⁻³), dominated by early spring diatoms Pauliella taeniata and Fragilariopsis oceanica in the surface waters, which indicated the beginning of the spring bloom, were observed only in the southeastern part of the Chukchi shelf and off Point Barrow. In July and August summer period, more than a half of the study area had <50% ice cover and the water column was stratified by temperature and salinity. Over the Chukchi shelf and continental slope of the Beaufort Sea, the phytoplankton abundance and biomass were an order of magnitude higher in July–August than in May–June. The taxonomic diversity of algae also increased due to the appearance of late-spring and summer diatoms, dinoflagellates, and coccolithophorids (Emiliania huxleyi). Interestingly, the seasonal differences between phytoplankton abundance and taxonomic composition in the spring and summer periods varied the least over the Chukchi Sea slope and in the deep-water area of the Arctic Ocean. High algae concentrations in summer were located in the lower layers of the euphotic zone, suggesting that the spring bloom on both the Chukchi shelf and in the western part of the Beaufort Sea occurred in late June/early July. In the spring and summer, the microalgal community was characterized by a high abundance of 4–10 μm flagellates, which exceeded the abundance of all other taxonomic groups. In both seasons studied, phytoplankton reached its maximum abundance within restricted areas in the southern part of the Chukchi Sea southwest of Point Hope, in the northern part of the Chukchi shelf between the 50- and 100-m isobaths, on the shelf northwest of Point Barrow, and over the continental slope in the Beaufort Sea. The pronounced spatial difference in the seasonal state was a characteristic feature of the phytoplankton community in the western Arctic.  相似文献   

Contrasting life-histories,secondary production,and trophic structure of Peracarid assemblages of the bathyal suprabenthos from the Bay of Biscay (NE Atlantic) and the Catalan Sea (NW Mediterranean)     

《Deep Sea Research Part I: Oceanographic Research Papers》2001,48(10):2209-2232

The life-histories and the secondary production of four dominant peracarid crustaceans (the mysids Boreomysis arctica and Parapseudomma calloplura, the amphipod Rhachotropis caeca, and the isopod Ilyarachna longicornis) in bathyal depths of the Bay of Biscay (NE Atlantic; between 383 and 420 m) and the Catalan Sea (Northwestern Mediterranean; between 389 and 1355 m) were established. Both the Atlantic and the Mediterranean populations of the major part of the target-species had two generations/year with mean cohort-production intervals (CPI) ranging from 5.5 mo for Ilyarachna longicornis to 6.3 mo for Parapseudomma calloplura. The Hynes method showed secondary production to vary in the Bay of Biscay between 0.113 mg DW m⁻² yr⁻¹ for I. longirostris and 3.069 mg DW m⁻² yr⁻¹ for P. calloplura, with P/B ratios between 4.57 (I. longirostris) and 7.93 (Boreomysis arctica). In the Catalan Sea, production varied between 0.286 mg DW m⁻² yr⁻¹ for I. longirostris and 1.096 mg DW m⁻² yr⁻¹ for P. calloplura, with P/B between 5.72 (I. longirostris) and 6.66 (P. calloplura). Application of two different empiric models to the whole peracarid assemblage gave similar levels of secondary production in both study areas (between 29.26 and 32.14 mgDWm⁻² yr⁻¹ in the Bay of Biscay; between 26.23 and 26.54 mg DW m⁻² yr⁻¹ in the Catalan Sea). From the analysis of gut contents of 22 species the dominant species in each study area were assigned to two basic trophic levels, detritus feeders and predators. Also, cumulative curves of dominance showed high diversity (low dominance) for peracarid assemblages distributed at mid-bathyal depths (524–693 m) both in the Bay of Biscay off Arcachon and in the Catalan Sea off Barcelona. We also discuss and compare, both within and between areas, how environmental features may explain the observed diversity patterns, the trophic structure, and the production results obtained for the suprabenthos assemblages.  相似文献   

Hydrographic and hydrodynamic characteristics of the eastern basin of the Bransfield Strait (Antarctica)     

《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(10):1755-1778

Hydrographic station and current meter data are used to estimate circulation and transport in the eastern basin of the Bransfield Strait. The short distance between adjacent hydrographic stations (20 km) allows evaluation of structures at scales seldom addressed in previous studies. The main feature of the derived circulation is the Bransfield Front and its associated baroclinic jet (the Bransfield Current). This frontal current crosses the northern half of the basin in a generally SW–NE direction, has maximum geostrophic speeds of 22 cm s^−l (at the jet entrance), and has geostrophic transport relative to 500 dbar estimated to be 1 Sv. Dynamically significant mesoscale features associated with the Bransfield Current are seen to be relevant down to 500 dbar. Specific aspects inferred from our analysis are the apparent high degree of stationarity of the described circulation, the shallow intrusions of Circumpolar Deep Water through the northern boundary of the domain (from the Drake Passage), and the northward sinking of Weddell Sea water over most of the domain.  相似文献