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1.
On a transect across the Lomonosov Ridge stratified zooplankton tows were made to the bottom at seven stations. A species inventory was established and compared with earlier observations in the Arctic Ocean. Differences between the Amundsen and Makarov basins are relatively small and correspond well with the general circulation patterns for Atlantic, Pacific, and neritic waters, suggesting slow mixing rates for the different basins. There were no remarkable differences in the species composition or their vertical distribution between the two sides of the Lomonosov Ridge. This indicates effective faunistic exchange across the ridge, although several bathy-pelagic species were almost or completely absent on top of the Ridge. Biomass showed a strong gradient along the transect, with a pronounced peak (9.5 g dry weight m−2) in the core of Atlantic water over the ridge, and minima over the deep basins. These differences were related to the effect of bottom topography for deep-living species, and the dynamics of the Atlantic layer for the meso- and epipelagic species. The maximum was formed mainly by the copepods Calanus hyperboreus and Metridia longa together with chaetognaths and ostracods. The presence of young developmental stages in some of the abundant species (C. hyperboreus, M. longa) suggests successful reproduction at all stations but C. finmarchicus was almost exclusively represented as old stages and adults. Comparison with earlier data on abundance and biomass from the Canada Basin (Russian Drift station “North Pole-22”) shows a pronounced difference with respect to both absolute quantities and relative composition. The copepod C. finmarchicus is completely absent in the central Canada Basin, and the portion of non-copepod zooplankton is dramatically decreased. This points to a reduced advection of Atlantic water or more severe food conditions in this basin.  相似文献   

2.
The distribution of Calanus finmarchicus was studied on a transect across the central Greenland Sea, and on five transects from the Eurasian shelves across the Atlantic Inflow in the Arctic Ocean. Stage composition was used as an indicator for successful growth; gonad maturity and egg production were taken as indicators for reproductive activity. On the Arctic Ocean transects, these parameters were measured simultaneously from the sibling species Calanus glacialis. Response of egg production rate to different temperatures at optimal food conditions was very similar between both species in the laboratory. C. finmarchicus was present at all stations studied, but young developmental stages were only present close to the regions of submergence of Atlantic water under the Polar water. This together with a decreasing abundance and biomass from west to east along the Atlantic Inflow in the Arctic Ocean and reproductive failure indicates that C. finmarchicus is expatriated in the Arctic Ocean. We hypothesize that the late availability of food in the Arctic Ocean, rather than low temperature per se, limits reproductive success. Better reproductive success in the very low temperature regions of the Return Atlantic Current and the marginal ice zone in the Greenland Sea supports this hypothesis. The possibility for a replacement of C. glacialis by C. finmarchicus and consequences for the ecosystem after increasing warming of the Arctic are discussed.  相似文献   

3.
北冰洋浮游生物空间分布及其季节变化的模拟   总被引：3，自引：1，他引：2  
低营养级浮游生物生态动力过程对环境变化的响应非常敏感。随着全球气候变化加剧,北冰洋正在经历快速的环境变化。厘清北冰洋低营养级浮游生物季节分布与变化特征是探究北冰洋生态系统对环境快速变化响应的前提,也是评估北极海区固碳能力的重要依据。基于此,本文构建了海洋–海冰–生物地球化学循环模型,并对北冰洋叶绿素浓度以及浮游生物结构的时空变化特征进行了模拟,结果表明:(1)北冰洋表层叶绿素浓度的峰值主要出现在5月,且太平洋一侧叶绿素浓度高于大西洋一侧;随着海水层化,表层受营养盐限制的海区呈现次表层叶绿素浓度最大值现象,且由陆架向海盆,次表层叶绿素浓度最大值层逐渐加深;9月,叶绿素浓度高值重回水体上层,太平洋一侧海区表层叶绿素浓度呈现较为明显的次峰值。(2)由于太平洋和大西洋入流营养盐浓度及结构的不同,北冰洋表层浮游生物群落结构存在明显空间差异。太平洋一侧,硅藻和中型浮游动物占优,硅藻在5月和9月出现生物量峰值,微型浮游植物在3月、5月和6月维持相对较高生物量;而大西洋一侧,在早春－春末夏初－夏秋经历了微型浮游植物－硅藻－微型浮游植物的演替,总体而言,微型浮游植物和微型浮游动物占优。此外,两侧海区浮游动物浓度峰值相较浮游植物滞后约半月。  相似文献   

4.
The distribution and demography of Calanus finmarchicus, C. glacialis and C. hyperboreus were studied throughout their growth season on a basin scale in the Norwegian Sea using ordination techniques and generalized additive models. The distribution and demographic data were related to the seasonal development of the phytoplankton bloom and physical characteristics of water masses. The resulting quantified relationships were related to knowledge on life cycle and adaptations of Calanus species. C. finmarchicus was the numerically dominant Calanus species in Coastal, Atlantic and Arctic waters, showing strong association with both Atlantic and Arctic waters. C. hyperboreus and C. glacialis were associated with Arctic water; however, C. glacialis was occasionally observed in the Norwegian Sea and is probably an expatriate advected into the area from various origins. Demography indicated one generation per year of C. finmarchicus, a two-year life cycle of C. hyperboreus, and both one- and two-year life cycles for C. glacialis in the water masses where they were most abundant. For the examined Calanus species, young copepodites of the new generation seemed to be tuned to the phytoplankton bloom in their main water mass. The development of C. finmarchicus was delayed in Arctic water, and mis-match between feeding stages and the phytoplankton bloom may reduce survival and reproductive success of C. finmarchicus in Arctic water. Based on low abundances of C. hyperboreus CI–III in Atlantic water and main recruitment to CI prior to the phytoplankton bloom, we suggest that reproduction of C. hyperboreus in Atlantic water is not successful.  相似文献   

5.
We collected mesozooplankton samples in the upper 100 m in spring or early summer each year between 1995 and 2000 along a section from Hamilton Bank (Labrador) to Cape Desolation (Greenland), and along additional sections in spring 1997 and early summer 1995. The North Atlantic waters of the central basin were characterised by the presence of the copepods Calanus finmarchicus, Euchaeta norvegica and Scolecithrocella minor and euphausiids. Calanus glacialis, Calanus hyperboreus and Pseudocalanus spp. were associated with the Arctic waters over the shelves. Amongst the other enumerated groups larvaceans were concentrated over the shelves and around the margins. Amphipods, pteropods and the copepods Oithona spp. and Oncaea spp. showed no definable relationships with water masses or bathymetry, while the diel migrant ostracods and chaetognaths were confined to deep water. Metrida longa, also a strong diel migrant, and Microcalanus spp., a mainly deep water species and possible diel migrant, were both sometimes quite abundant on the shelves as well as in the central basin, consistent with their likely Arctic origins.Analysis of community structure along the section across the Labrador Sea indicated that stations could be grouped into five different zones corresponding to: the Labrador Shelf; the Labrador Slope; the western and central Labrador Sea; the eastern Labrador Sea and Greenland Slope; and, the Greenland Shelf. The boundaries between zones varied spatially between years, but community composition was relatively consistent within a given zone and a given season (spring versus early summer). The relationship between community composition and water masses was not entirely straightforward. For example, Labrador Shelf water was generally confined to the shelf, but in spring 2000 when it also dominated the adjacent slope zone, the community in the Labrador Slope zone was similar to those found in other years. Conversely, in spring 1997, when Arctic organisms were unusually abundant in the Labrador Slope zone, there was no increased contribution of shelf water. In addition, North Atlantic organisms were often found on the shelves when no slope or central basin water was present.Although other organisms were sometimes very abundant, the mesozooplankton preserved dry weight biomass was dominated everywhere by the three species of Calanus, which together always accounted for ≥70%. One species, C. finmarchicus, comprised >60% of the total mesozooplankton biomass and >80% of the abundance of large copepods in spring and summer throughout the central Labrador Sea. In western and central regions of the central basin average C. finmarchicus biomass was ca 4 g dry weight m−2 and average abundance, ca 17?000 m−2 over both seasons. Highest levels (ca 7 g dry weight m−2, >100?000 m−2) occurred in the northern Labrador Sea in spring and in eastern and southwest regions in early summer. C. hyperboreus contributed ca 20% of the total mesozooplankton biomass in the central basin in spring and <5% in early summer, while C. glacialis accounted for <1%. Over the shelves, C. hyperboreus contributed a maximum of 54% and 3.6 g dry weight m−2, and C. glacialis, a maximum of 29% and 1 g dry weight m−2, to the total mesozooplankton biomass.  相似文献   

6.
The biomass, species and chemical composition of the mesozooplankton and their impact on lower food levels were estimated along a transect across the Arctic Ocean. Mesozooplankton biomass in the upper 200 m of the water column was significantly higher (19–42 mg DW m-3) than has previously been reported for the Arctic Ocean, and it reached a maximum at ca. 87°N in the Amundsen Basin. The lowest values were recorded in the Chukchi Sea and Nansen Basin, where ice cover was lower (50–80%) than in the central Arctic Ocean. In the deeper strata (200–500 m) of the Canadian and Eurasian Basins, the biomass was always much lower (4.35–16.44 mg DW m-3). The C/N (g/g) ratio for the mesozooplankton population was high (6.5–8.5) but within the documented range. These high values (when compared to 4.5 at lower latitudes) may be explained by the high lipid content. Mesozooplankton accounted for approximately 40% of the total particulate organic carbon in the upper 100 m of the water column. Mesozooplankton species composition was homogeneous along the transect, consisting mainly of copepods (70–90% of the total number). It was dominated by four large copepod species (Calanus hyperboreus, C. glacialis, C. finmarchicus and Metridia longa), which together accounted for more than 80% of the total biomass. According to measurements of gut pigment and gut turnover rates, the mesozooplankton on average ingested between 6 and 30% of their body carbon per day as phytoplankton. Microzooplankton may have provided an additional source of energy for the mesozooplankton community. These data emphasize the importance of mesozooplankton in the arctic food web and reinforce the idea that the Arctic Ocean should no longer be considered to be a “biological desert”.  相似文献   

7.
At interannual to multidecadal time scales, much of the oceanographic and climatic variability in the North Atlantic Ocean can be associated with the North Atlantic Oscillation (NAO). While evidence suggests that there is a relationship between the NAO and zooplankton dynamics in the North Atlantic Ocean, the phytoplankton response to NAO-induced changes in the environment is less clear. Time series of monthly mean phytoplankton colour values, as compiled by the Continuous Plankton Recorder (CPR) survey, are analysed to infer relationships between the NAO and phytoplankton dynamics throughout the North Atlantic Ocean. While a few areas display highly significant (p < 0.05) trends in the CPR colour time series during the period 1948–2000, nominally significant (p < 0.20) positive trends are widespread across the basin, particularly on the continental shelves and in a transition zone stretching across the Central North Atlantic. When long-term trends are removed from both the NAO index and CPR colour time series, the correlation between them ceases to be significant. Several hypotheses are proposed to explain the observed variability in the CPR colour and its relationship with climate in the North Atlantic.  相似文献   

8.
The saturation of calcite and aragonite in the Arctic Ocean   总被引：1，自引：0，他引：1  
We report on the chemical saturation of CaCO3 in the waters of the Arctic Ocean calculated from total alkalinity (AT) and total dissolved inorganic carbon (CT). Data based on four different expeditions are presented: International Arctic Ocean Expedition (IAOE-91), Arctic Ocean Section 94 (AOS94), Polarstern Arctic '96 expedition (ACSYS 96), and Joint Ocean Ice Study 97 (JOIS 97). The results show a lysocline at around 3500 m for aragonite and that most of the Arctic Ocean sea floor lies above the lysocline for calcite. The only anomaly is the low degree of saturation at the shelf break depth in the Canadian Basin seen in the sections of the AOS94 and JOIS 97 cruises, correlated with nutrient maxima and very low O2 concentration, suggesting decomposition of organic matter. The insignificant variability in degree of saturation between the deep waters of the different basins in the Arctic Ocean indicates a very low sedimentation/remineralisation of organic soft matter.  相似文献   

9.
Evidence of shelf-water transfer from temperature, salinity, and 228Ra/226Ra sampling from the nuclear submarine USS L. Mendel Rivers SCICEX cruise in October, 2000 demonstrates the heterogeneity of the Arctic Ocean with respect to halocline ventilation. This likely reflects both time-dependent events on the shelves and the variety of dispersal mechanisms within the ocean, including boundary currents and eddies, at least one of which was sampled in this work. Halocline waters at the 132 m sampling depth in the interior Eurasian Basin are generally not well connected to the shelves, consonant with their ventilation within the deep basins, rather than on the shelves. In the western Arctic, steep gradients in 228Ra/226Ra ratio and age since shelf contact are consistent with very slow exchange between the Chukchi shelf and the interior Beaufort Gyre. These are the first radium measurements from a nuclear submarine.  相似文献   

10.
The principal features of the marine ecosystems in the Barents and Norwegian Seas and some of their responses to climate variations are described. The physical oceanography is dominated by the influx of warm, high-salinity Atlantic Waters from the south and cold, low-salinity waters from the Arctic. Seasonal ice forms in the Barents Sea with maximum coverage typically in March–April. The total mean annual primary production rates are similar in the Barents and Norwegian Seas (80–90 g C m−2), although in the Barents, the production is higher in the Atlantic than in the ice covered Arctic Waters. The zooplankton is dominated by Calanus species, C. finmarchicus in the Atlantic Waters of the Norwegian and Barents Seas, and C. glacialis in the Arctic Waters of the Barents Sea. The fish species in the Norwegian Sea are mostly pelagics such as herring (Clupea harengus) and blue whiting (Micromesistius poutassou), while in the Barents Sea there are both pelagics (capelin (Mallotus villosus Müller), herring, and polar cod (Boreogadus saida Lepechin)) and demersals (cod (Gadus morhua L.) and haddock (Melanogrammus aeglefinus)). The latter two species spawn in the Norwegian Sea along the slope edge (haddock) or along the coast (cod) and drift into the Barents Sea. Marine mammals and seabirds, although comprising only a relatively small percentage of the biomass and production in the region, play an important role as consumers of zooplankton and small fish. While top-down control by predators certainly is significant within the two regions, there is also ample evidence of bottom-up control. Climate variability influences the distribution of several fish species, such as cod, herring and blue whiting, with northward shifts during extended warm periods and southward movements during cool periods. Climate-driven increases in primary and secondary production also lead to increased fish production through higher abundance and improved growth rates.  相似文献   

11.
The Fram Strait is very important with regard to heat and mass exchange in the Arctic Ocean, and the large quantities of heat carried north by the West Spitsbergen Current (WSC) influence the climate in the Arctic region as a whole. A large volume of water and ice is transported through Fram Strait, with net water transport of 1.7–3.2 Sv southward in the East Greenland Current and a volume ice flux in the range of 0.06–0.11 Sv. The mean annual ice flux is about 866,000 km2 yr−1. The Kongsfjorden–Krossfjorden fjord system on the coast of Spitsbergen, or at the eastern extreme of Fram Strait, is mainly affected by the northbound transport of water in the WSC. Mixing processes on the shelf result in Transformed Atlantic Water in the fjords, and the advection of Atlantic water also carries boreal fauna into the fjords. The phytoplankton production is about 80 g C m−2 yr−1 in Fram Strait, and has been estimated both below and above this for Kongsfjorden. The zooplankton fauna is diverse, but dominated in terms of biomass by calanoid copepods, particularly Calanus glacialis and C. finmarchicus. Other important copepods include C. hyperboreus, Metridia longa and the smaller, more numerous Pseudocalanus (P. minutus and P. acuspes), Microcalanus (M. pusillus and M. pygmaeus) and Oithona similis. The most important species of other taxa appear to be the amphipods Themisto libellula and T. abyssorum, the euphausiids Thysanoessa inermis and T. longicaudata and the chaetognaths Sagitta elegans and Eukrohnia hamata. A comparison between the open ocean of Fram Strait and the restricted fjord system of Kongsfjorden–Krossfjorden can be made within limitations. The same species tend to dominate, but the Fram Strait zooplankton fauna differs by the presence of meso- and bathypelagic copepods. The seasonal and inter-annual variation in zooplankton is described for Kongsfjorden based on the record during July 1996–2002. The ice macrofauna is much less diverse, consisting of a handful of amphipod species and the polar cod. The ice-associated biomass transport of ice-amphipods was calculated, based on the ice area transport, at about 3.55 × 106 ton wet weight per year or about 4.2 × 105 t C yr−1. This represents a large energy input to the Greenland Sea, but also a drain on the core population residing in the multi-year pack ice (MYI) in the Arctic Ocean. A continuous habitat loss of MYI due to climate warming will likely reduce dramatically the sympagic food source. The pelagic and sympagic food web structures were revealed by stable isotopes. The carbon sources of particulate organic matter (POM), being Ice-POM and Pelagic-POM, revealed different isotopic signals in the organisms of the food web, and also provided information about the sympagic–pelagic and pelagic–benthic couplings. The marine food web and energy pathways were further determined by fatty acid trophic markers, which to a large extent supported the stable isotope picture of the marine food web, although some discrepancies were noted, particularly with regard to predator–prey relationships of ctenophores and pteropods.  相似文献   

12.
Perhaps more than in any other ocean, our understanding of the continental shelves of the Arctic Mediterranean is decidedly disciplinary, regional and fractured, and this shortcoming must be addressed if we are to face and prepare for climate change. A fundamental flaw is that while excellent process studies exist, and while recent ship-based expeditions have added greatly to our collective body of knowledge, an integrated and fully pan-Arctic perspective on the structure and function of food webs on Arctic shelves is lacking. Based on the collective overviews given in Progress in Oceanography xx, xx–xx, we attempt to address this issue. To build a perspective that inter-connects the various shelf regions we suggest three unifying typologies affecting food webs that will hopefully allow inter-comparison of regional investigations. The first is for shelf geography, wherein shelves are classified according to their role in the Arctic throughflow. The second is for ice climate, wherein the various ice regimes are examined for their specific impacts on food web dynamics. The third is for stratification where it is argued that the source of buoyancy, thermal or haline, impacts production and the vertical carbon flux. We then address the connection between physical habitat and biota on pan-Arctic (and global climate) scales. This discussion begins with the recognition that the Arctic Ocean is integral to the World Ocean via its thermohaline (“estuarine”) exchanges with the Atlantic and Pacific. As such the Arctic and its shelves act as a double estuary, wherein incoming waters become both lighter (positive estuary), by mixing with freshwater sources, and heavier (negative estuary) by cooling and brine release. Shelves are central to such transformations. This complex interconnectivity coupling of the Arctic Ocean to its sub-Arctic (and more productive) neighbors demands that food webs be considered through a macroecological view that includes an ecology of advection. We argue that the macroecological view is required if we are to understand and model food webs under forcing along climate gradients. To aid this effort we introduce the concept of contiguous domains, wherein physical habitats are joined by common features that will allow inter-comparisons of existing and future food webs over large scales and climatic gradients. Finally, we speculate on the range of possible futures for Arctic shelves based on the palaeo-record.  相似文献   

13.
Christoph Vogt  Jochen Knies   《Marine Geology》2008,250(3-4):211-222
This study focuses on sedimentological investigations of sediment cores recovered during the international Arctic′91, expeditions with the German research ice breaker RV “Polarstern” to the European sector of the Arctic Ocean. Here, we deduce the last glacial/interglacial changes in transport mechanism and sedimentation from the clay mineral group smectite. We choose the smectites as an example of how sediment mineralogy can be linked with particular source regions (the Kara and Laptev seas), distinct transport mechanism (sea ice and surface currents) and sedimentation processes. Smectite contents in Arctic sediments discussed for two time slices, including the Last Glacial Maximum (LGM), and the last deglaciation (Termination I), reveal the highest variability subsequent to the retreat of the Eurasian ice sheets. Our results show that smectite anomalies in the Eurasian Basin are associated with distinct meltwater pulses and occurred around 13.5–13.0 14C ka B.P. Compelling evidence is provided that these anomalies are deduced from sea-ice entrained sediments from the eastern Kara Sea that entered the Arctic Ocean after ice-sheet break-up and eventually flooding of the Kara Sea. We propose that smectite anomalies in sediments of the eastern Arctic Ocean can be utilized to identify deglacial events and to help decipher configurations of the Eurasian ice sheets. The identification of smectite maxima along the modern sea-ice edge in the Eurasian Basin further indicates biologically enhanced sedimentation from melting sea ice allowing the reconstruction of seasonally open water in the region. Hence, considering the poor preservation conditions of primary paleoceanographic proxies in the Arctic Ocean, the clay mineral contents, particularly the smectite group, may be one alternative tool for paleoclimatic reconstruction in the Eurasian Basin.  相似文献   

14.
Dissolved aluminium and the silicon cycle in the Arctic Ocean   总被引：1，自引：0，他引：1  
Concentrations of dissolved (0.2 µm filtered) aluminium (Al) have been determined for the first time in the Eurasian part of the Arctic Ocean over the entire water column during expedition ARK XXII/2 aboard R.V. Polarstern (2007). An unprecedented number of 666 samples was analysed for 44 stations along 5 ocean transects. Dissolved Al in surface layer water (SLW) was very low, close to 1 nM, with lowest SLW concentrations towards the Canadian part of the Arctic Ocean and higher values adjacent to and in the shelf seas. The low SLW concentrations indicate no or little influence from aeolian dust input. Dissolved Al showed a nutrient-type increase with depth up to 28 nM, but large differences existed between the different deep Arctic basins. The differences in concentrations of Al between water masses and basins could largely be related to the different origins of the water masses. In the SLW and intermediate water layers, Atlantic and Pacific inflows were of importance. Deep shelf convection appeared to influence the Al distribution in the deep Eurasian Basin. The Al distribution of the deep Makarov Basin provides evidence for Eurasian Basin water inflow into the deep Makarov Basin. A strong correlation between Al and Silicon (Si) was observed in all basins. This correlation and the nutrient-like profile indicate a strong biological influence on the cycling and distribution of Al. The biological influence can be direct by the incorporation of Al in biogenic silica, indirect by preferential scavenging of Al onto biogenic siliceous particles, or by a combination of both processes. From the slope of the overall Al–Si relationship in the intermediate water layer (AIDW; ~ 200–2000 m depth), an Al/Si ratio of 2.2 atoms Al per 1000 atoms Si was derived. This ratio is consistent with the range of previously reported Al/Si uptake ratio in biogenic opal frustules of diatoms. In the deepest waters (>2000 m depth) a steeper slope of the Al–Si relationship of 7.4 to 13 atoms Al per 1000 atoms Si likely results from entrainment of cold shelf water into the deep basins, carrying the signal of dissolution of terrigenous particles with a much higher Al:Si ratio of crustal abundance. Only a small enrichment with such crustal Al and Si component may readily account for the higher Al:Si slope in the deepest waters.  相似文献   

15.
The depth distributions of the radiolarian fauna in the Chukchi and Beaufort Seas, marginal seas of the western Arctic Ocean, were examined quantitatively in depth-stratified plankton tows from 4 or 5 intervals above 500 m and in surface sediments from various depths between 163 and 2907 m. The radiolarian assemblage from the water column in September 2000 was dominated by Amphimelissa setosa and followed by the Actinomma boreale/leptoderma group, Pseudodictyophimus gracilipes and Spongotrochus glacialis. These species are related to the Arctic Surface Water shallower than 150 m. This assemblage is similar to that in the Greenland Sea relating to the ice edge, but did not contain typical Pacific radiolarians in spite of the flow of water of Pacific origin in this region. The living depth of Ceratocyrtis historicosa was restricted to the relatively warm water between 300 and 500 m corresponding to the upper Arctic Intermediate Water (AIW) originating from the Atlantic Ocean. Radiolarian assemblages in the surface sediments are similar to those in the plankton tows, except for common Cycladophora davisiana in sediment samples below 500 m. C. davisiana is probably a deep-water species adapted to the lower AIW or the Canadian Basin Deep Water ventilated from the shelves.  相似文献   

16.
The biological pump is a central process in the ocean carbon cycle, and is a key factor controlling atmospheric carbon dioxide (CO2). However, whether the Arctic biological pump is enhanced or reduced by the recent loss of sea ice is still unclear. We examined if the effect was dependent on ocean circulation. Melting of sea ice can both enhance and reduce the biological pump in the Arctic Ocean, depending on ocean circulation. The biological pump is reduced within the Beaufort Gyre in the Canada Basin because freshwater accumulation within the gyre limits nutrient supply from deep layers and shelves hence inhibits the growth of large-bodied phytoplankton. Conversely, the biological pump is enhanced outside the Beaufort Gyre in the western Arctic Ocean because of nutrient supply from shelves and greater light penetration, enhancing photosynthesis, caused by the sea ice loss. The biological pump could also be enhanced by sea ice loss in the Eurasian Basin, where uplifted isohaline surfaces associated with the Transpolar Drift supply nutrients upwards from deep layers. New data on nitrate uptake rates are consistent with the pattern of enhancement and reduction of the Arctic biological pump. Our estimates indicate that the enhanced biological pump can be as large as that in other oceans when the sea ice disappears. Contrary to a recent conclusion based on data from the Canada Basin alone, our study suggests that the biological CO2 drawdown is important for the Arctic Ocean carbon sink under ice-free conditions.  相似文献   

17.
Distribution of 230Th and 231Pa in the water column was measured in the Eurasian basins of the Arctic Ocean, i.e. the Makarov, Amundsen and Nansen basins. The profiles obtained were compared to one previously published from the Alpha Ridge (Bacon et al., Earth and Planetary Science Letters, 95 (1989) 15–22. The Amundsen and Nansen basins are similar in their 23OTh and 231Pa distribution, whereas in the Makarov Basin and at the Alpha Ridge these radionuclides are comparatively enriched in the deep basin. This may be due to low particle flux in conjunction with low water mass renewal rates. The 230Th concentration in water depth < 1000 m in the Makarov Basin is relatively low compared with the Alpha Ridge, which may be caused by an exchange of water masses between the Amundsen and Makarov basins.In the Eurasian Basin Deep Water, 230Th profiles can be explained both by a scavenging model and by a mixing-scavenging model. Enhanced particle load caused by resuspension may explain the increased scavenging in the Eurasian Basin Bottom Water. The differences in scavenging between the Norwegian-Greenland Sea and the Eurasian basins at present are not large enough to cause significant fractionation between 230Th and 231Pa.  相似文献   

18.
Surface distribution (0–100 m) of zooplankton biomass and specific aminoacyl-tRNA synthetases (AARS) activity, as a proxy of structural growth, were assessed during winter 2002 and spring 2004 in the Labrador Sea. Two fronts formed by strong boundary currents, several anticyclonic eddies and a cyclonic eddy were studied. The spatial contrasts observed in seawater temperature, salinity and fluorescence, associated with those mesoscale structures, affected the distributions of both zooplankton biomass and specific AARS activity, particularly those of the smaller individuals. Production rates of large organisms (200–1000 μm) were significantly related to microzooplankton biomass (63–200 μm), suggesting a cascade effect from hydrography through microzooplankton to large zooplankton. Water masses defined the biomass distribution of the three dominant species: Calanus glacialis was restricted to cold waters on the shelves while Calanus hyperboreus and Calanus finmarchicus were widespread from Canada to Greenland. Zooplankton production was up to ten-fold higher inside anticyclonic eddies than in the surrounding waters. The recent warming tendency observed in the Labrador Sea will likely generate weaker convection and less energetic mesoscale eddies. This may lead to a decrease in zooplankton growth and production in the Labrador basin.  相似文献   

19.
The Atlantic inflow in the Fram Strait(78°50′N) has synoptic scale variability based on an array of moorings over the period of 1998–2010. The synoptic scale variability of Atlantic inflow, whose significant cycle is 3–16 d, occurs mainly in winter and spring(from January to April) and is related with polar lows in the Barents Sea. On the synoptic scale, the enhancement(weakening) of Atlantic inflow in the Fram Strait is accompanied by less(more)polar lows in the Barents Sea. Wind stress curl induced by polar lows in the Barents Sea causes Ekman-transport,leads to decrease of sea surface height in the Barents Sea, due to geostrophic adjustment, further induces a cyclonic circulation anomaly around the Barents Sea, and causes the weakening of the Atlantic inflow in the Fram Strait. Our results highlight the importance of polar lows in forcing the Atlantic inflow in the Fram Strait and can help us to further understand the effect of Atlantic warm water on the change of the Arctic Ocean.  相似文献   

20.
基于PHC3.0极地科学中心水文气候数据集(简称PHC3.0数据集)的温度和盐度资料,使用聚类分析和Bayes判别分析的方法,对北纬70°以北海域的水团结构进行了分析,在北冰洋区域划分出4个水团:北冰洋表层水(ASW)、大西洋中层水(AIW)、太平洋水(PW)和北冰洋深层水(ADW)。北冰洋表层水(ASW)遍布于欧亚海盆和加拿大海盆,以低温低盐为特征。大西洋中层水(AIW)位于约200～900m深度,在北冰洋环极边界流的作用下,其影响可达到加拿大海盆。太平洋水(PW)受经白令海峡进入北冰洋的海水影响,相对高温低盐,夏季时影响显著。北冰洋深层水(ADW)在海盆中相当均匀,几乎没有季节变化,盐度约在34.95psu,温度在加拿大海盆约为-0.3℃,欧亚海盆约为-0.7℃。  相似文献   

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