Visualizing Upwelling at Monterey Bay in an Integrated Environment of GIS and Scientific Visualization

Oceanographic data are complex in that they incorporate multiple measurements and various scales. They are truly three-dimensional, and often vary in time. As the ability to acquire data is constantly being enhanced by the introduction of new and increasingly sophisticated instruments, it is challenging for oceanographers to inspect oceanographic processes by analyzing the complex data conventionally. In this article, we discuss an integrated GIS/visualization approach to visualize oceanographic data in Monterey Bay in order to get a better understanding of upwelling processes. The GIS system performs data interpolation, unifies map projection, and filters the processed data to a computer visualization package. The multidimensional visualization and animation features of the visualization tool are used to gain insight into marine upwelling processes. In such an integrated environment, the water properties (i.e., temperature, salinity, and density) in Monterey Bay during upwelling are visualized, and the characteristics of upwelling are examined. The center of upwelling and the maximum depth of upwelling in Monterey Bay during the 1995 upwelling season are identified. The differences in temperature changing patterns between a typical upwelling year and an El Nino year are shown in this study. The integration of GIS and visualization makes it easier for oceanographers to discover and understand upwelling.     

Diel nitrate cycles observed with in situ sensors predict monthly and annual new production

We report on a direct and autonomous measure of new production based on time series observations with ISUS nitrate sensors deployed for several years on oceanographic moorings offshore of Monterey Bay, California. The amplitude of diel cycles of surface nitrate is correlated with rates of primary production measured by ¹⁴C uptake. The drawdown of nitrate averaged over a year is about 70% of the fixed nitrogen needed for biomass production. Phytoplankton biomass predicted from the diel nitrate uptake and a fixed rate constant for nitrate loss (grazing and export) matched observations over the annual cycle. New production rates determined with the moored sensors are highly correlated with nitrate concentration and the intensity of upwelling. The implication is that arrays of moorings with chemical sensors can now be used to estimate new production of biomass and ecosystem processes over multiple temporal and spatial scales.     

Recruitment of coastal fishes and oceanographic variability in central California

Recruitment of pelagic larval fishes to the nearshore environment is dependent on a suite of biological and physical processes operating at many spatial and temporal scales. Nearshore circulation processes associated with coastal upwelling are widely upheld as major determinants of year class strength for many rockfishes (Sebastes spp.), but the mechanism by which these processes drive recruitment is largely unknown. We used Standard Monitoring Units for the Recruitment of Fishes (SMURFs) to monitor recruitment of two rockfish complexes (Sebastes spp.) and cabezon (Scorpaenichthys marmoratus) from March to September of 2004 and 2005 at 3 sites along the central California coast. We examined the relationship between recruitment of these fishes and measurements of oceanographic variability associated with upwelling dynamics, including in situ water temperature, AVHRR sea surface temperature, the Bakun upwelling index, and an index of alongshore surface water transport. We found that rockfish comprising the KCGB complex (Sebastes atrovirens, Sebastes caurinus, Sebastes carnatus, Sebastes chrysomelas) recruit during early summer, while fishes of the BYO complex (Sebastes melanops, Sebastes flavidus, Sebastes serranoides), as well as cabezon recruit during late summer. Our results provide limited support for an association between the arrival of juvenile pelagic rockfish and cabezon to the nearshore environment and physical processes related to upwelling and relaxation. Beyond the limitations of our bimonthly sampling scheme, the lack of a clear pattern may be related to the near absence of upwelling–relaxation cycles along this stretch of coast during these two study periods. Moreover, the settlement and recruitment of nearshore fishes may be closely tied to processes occurring earlier in the larval stage.     

Upwelling and the distribution of chlorophyll a within the Bay of Concepción,Chile

The influence of upwelling on the distribution of chlorophyll a within the Bay of Concepción, Chile is discussed in light of continuous measurements of surface in vivo chlorophyll fluorescence and temperature taken simultaneously along horizontal transects, and hydrographic stations' data. Results suggest significant temporal variability both in the distribution of in vivo fluorescence, temperature and salinity within the Bay and in the characteristics of the exchange between the Bay and the adjacent shelf waters, induced by variable upwelling. Upwelling is produced by the predominant south-westerly winds during the summer. Significant variations in the wind direction occur with periods from two to seven days. During active upwelling, exchange is characterized by a surface outflow through the mouth of the Bay and an inflow at depth. Low chlorophyll fluorescence is confined to the upwelling areas on the eastern shore either within or outside the Bay; high chlorophyll fluorescence is confined to the central and western Bay. Density data suggest a three-layered circulation pattern at the mouth of the Bay during the upwelling relaxation involving an inflow both at the surface and bottom and outflow at mid-depth. Associated with this exchange is an active high chlorophyll transport from the Bay to the adjacent coastal waters at mid-depth and inflow of low chlorophyll water from the adjacent shelf at the surface and near the bottom.     

Upwelling and ocean structures off Algoa Bay and the south-east coast of South Africa

As the Agulhas Current flows along the south-east coast of South Africa, a number of processes operate that bring cold, deep water up onto the narrow shelf. As a consequence, upwelling along the coastline is enhanced farther southward and downstream. This situation is investigated off Algoa Bay and along the south-east coast to Port Alfred, where measurements demonstrate that marked temperature variability occurs at the coastline, particularly in summer when temperature structures are more intense and easterly-component winds more common. There is no indication that upwelling is more prevalent at Port Alfred; increasing variability farther south is evident at Woody Cape/Cape Padrone, where the coastline veers westwards, forming the eastern boundary of Algoa Bay. Here it is found that, after a wind change to north-easterly, cold water is upwelled along the shoreline between 19 hours and 2.5 days later. Such upwelling progresses north-eastwards with the movement of the wind and weather systems, although colder water also moves south-westwards into Algoa Bay. Winds, currents, sea level and sea temperatures are highly correlated, with fluctuations in sea level measuring >50 cm being associated with coastal trapped waves (CTWs). Such barotropic wind-driven CTWs are frequently active during upwelling, although it is unclear whether there is any interaction between the two phenomena.     

Manganese and iron distributions off central California influenced by upwelling and shelf width

In July 2002, a combination of underway mapping and discrete profiles revealed significant along-shore variability in the concentrations of manganese and iron in the vicinity of Monterey Bay, California. Both metals had lower concentrations in surface waters south of Monterey Bay, where the shelf is about 2.5 km wide, than north of Monterey Bay, where the shelf is about 10 km wide. During non-upwelling conditions over the northern broad shelf, dissolvable iron concentrations measured underway in surface waters reached 3.5 nmol L⁻¹ and dissolved manganese reached 25 nmol L⁻¹. In contrast, during non-upwelling conditions over the southern narrow shelf, dissolvable iron concentrations in surface waters were less than 1 nmol L⁻¹ and dissolved manganese concentrations were less than 5 nmol L⁻¹. A pair of vertical profiles at 1000 m water depth collected during an upwelling event showed dissolved manganese concentrations of 10 decreasing to 2 nmol L⁻¹, and dissolvable iron concentrations of 12–20 nmol L⁻¹ in the upper 100 m in the north, compared to 3.5–2 nmol L⁻¹ Mn and 0.6 nmol L⁻¹ Fe in the upper 100 m in the south, suggesting the effect of shelf width influences the chemistry of waters beyond the shelf.These observations are consistent with current understanding of the mechanism of iron supply to coastal upwelling systems: Iron from shelf sediments, predominantly associated with particles greater than 20 μm, is brought to the surface during upwelling conditions. We hypothesize that manganese oxides are brought to the surface with upwelling and are then reduced to dissolved manganese, perhaps by photoreduction, following a lag after upwelling.Greater phytoplankton biomass, primary productivity, and nutrient drawdown were observed over the broad shelf, consistent with the greater supply of iron. Incubation experiments conducted 20 km offshore in both regions, during a period of wind relaxation, confirm the potential of these sites to become limited by iron. There was no additional growth response when copper, manganese or cobalt was added in addition to iron. The growth response of surface water incubated with bottom sediment (4 nmol L⁻¹ dissolvable Fe) was slightly greater than in control incubations, but less than in the presence of 4 nmol L⁻¹ dissolved iron. This may indicate that dissolvable iron is not as bioavailable as dissolved iron, although the influence of additional inhibitory elements in the sediment cannot be ruled out.     

RS与GIS在海洋地质调查中的应用

近几十年来,海洋的重要性愈来愈明显,海洋地质调查作为获取海洋数据的重要手段逐渐受到关注。海洋数据与陆地数据相比,具有多样性和时空复杂性的特点。近年来遥感技术和地理信息系统技术发展迅速,遥感的实时性、大面积监测性的特点以及地理信息系统对空间数据的有序管理及支持辅助决策的功能为海洋地质调查开辟了新的前景。笔者结合遥感和地理信息系统的特点、发展趋势,介绍了其在海洋地质调查领域中的应用,并对其应用前景做出展望。     

福建北部沿岸与台湾北面海域的水化学特性

根据１９８８年夏季台湾海峡海域的调查资料讨论福建北部沿岸和台湾北面海域水化学的区域性特征。结果表明，福建沿岸上升流是西部海域诸化学要素分布的控制因素。台湾北面海域（２５°５０′－２６°４０′Ｎ，１２１°４５′－１２２°３０′Ｅ）水体下层出现局部冷水抬升，福建沿岸和台湾北面海域都具有低溶解氧且不饱和、高营养盐、低温、高盐的特征，溶解氧、诸营养盐与温度、盐度分别有良好的相关关系。     

The influence of mesoscale physical processes on the larval fish community in the Canaries CTZ, in summer

We have studied the relation between the hydrography, the composition and horizontal structure of the larval fish community, and the horizontal distribution patterns of larval fish abundances in an area characterised by strong mesoscale oceanographic activity, located between the Canary Islands and the African coast (the Canaries Coastal Transition Zone), during August 1999. Upwelling, upwelling filaments, cyclonic and anticyclonic eddies and island wakes are typical mesoscale features of the northwest African coast in summer. A single upwelling filament off Cabo Juby was joined in mid-August by a second that originated about 100 km to the north. The two filaments flowed together and merged 100 km offshore. The merged filament was partially entrained around a cyclonic eddy, trapped between the Canary Islands and the African coast, and interacted with cyclonic and anticyclonic eddies shed from Gran Canaria. Mesoscale oceanographic features strongly influenced the horizontal distributions of fish larvae. Eddies acted as a mechanism of concentration, while upwelling filaments were dispersive, transporting larvae from the African neritic zone into oceanic areas and towards the Canary archipelago. This transport was the major cause of the predominance of neritic larvae in the composition of the larval fish community of the area. The results also suggest: (1) that anchovy larvae are good indicators of the offshore displacement of upwelled water; (2) that the alternation between anchovy and sardine as species dominant in the larval fish community of the area during summer depends upon the water temperature in the African upwelling region, anchovy dominating at higher temperature; (3) that a coupling of anchovy and sardine spawning with the mesoscale oceanographic structure formed by the upwelling filaments and trapped eddy overcomes the negative effect that Ekman transport has on their populations.     

The role of internal tides in the nutrient enrichment of Monterey Bay,California

Semidiurnal internal tides in Monterey Canyon are shown to be partially responsible for macronutrient enrichment of surface waters in Monterey Bay, California. CTD time series at five stations in the canyon revealed the presence of semidiurnal internal tides with heights between 50 and 120 m. p Thermistor data demonstrated an internal tidal bore at the head of the canyon. Data and theory suggest that internal tidal bores may be breaking, due to either shear instability or direct overturning, thereby enriching the immediate area near the canyon head.Transects normal to Monterey Canyon showed a 20-m thick lens of 12 °C water moving out of the canyon at high internal tide. This lens was then pinched off from the canyon, and led to a density-induced divergence. The nutrient transport associated with the internal tidal divergence could support as much as 30% of the daily primary productivity in the northern part of Monterey Bay during non-upwelling periods.     

Studies of hydrophysical processes during monitoring of the anthropogenic impact on coastal basins using the example of Mamala Bay of Oahu Island in Hawaii

This paper presents the main results of processing the data obtained in the study of hydrophysical processes during multidisciplinary monitoring of the anthropogenic impact on the coastal basin of Mamala Bay (Oahu Island, Hawaii). The results of the hydrophysical measurements carried out in August–September of 2002–2004 using stationary moorings and dropped and towed ship sensors were analyzed as the initial data. On the basis of these measurements, spatiotemporal, statistical, and spectral characteristics of different hydrophysical parameters of the marine envrionement in the basin of Mamala Bay were calculated, including three-dimensional components of the velocity vectors, the spectra of different components of velocities, the spectra of temperature fluctuations, and the characteristics of internal waves. The variability of the temperature fields and the correlation of the tidal phenomena with the temperature measurements and fluctuations caused by internal waves were analyzed. The materials and methods of the oceanographic studies and the results of the analysis of the meteorological and hydrological conditions are presented. The results obtained are used for a multidisciplinary analysis of the satellite and sea truth data.     

Applications of Geographic Information Systems (GIS) to habitat assessment and marine resource management

Marine scientists often assess habitats to understand the distribution and relative abundance of marine resources. Due to the spatial nature of habitats and associated temporal changes, however, assimilating data using traditional analytical methods is often difficult. Geographic Information Systems (GIS) are proving to be effective tools to help address problems inherent in the analysis of spatial data, GIS can be used to effectively collate, archive, display, analyze, and model spatial and temporal data. Additionally, by combining dissimilar data types, such as socio-political boundaries, bottom types, and fish distributions, for example, resource managers can use GIS to make informed management decisions. In this way, GIS provides resource managers with a means to integrate scientific data with prevailing cultural values and traditions. We have developed a working GIS for the Monterey Bay National Marine Sanctuary that allows interpretation of many terrestrial and marine data sets, including inter-tidal monitoring data, permit locations, seabird strandings, fisheries catch data, habitat types, marine political boundaries, as well as land cover classification from satellite imagery, watersheds, streams, roads, and political boundaries. We have linked terrestrial and marine data to create a broad spatial and temporal database that will be used in a variety of ways such as evaluating natural processes, permitting and monitoring coastal development and assessing environmental impacts (e.g. oil spills).     

Changes in the cetacean assemblage of a coastal upwelling ecosystem during El Niño 1997–98 and La Niña 1999

We report results of ecosystem studies in Monterey Bay, California, during the summer upwelling periods, 1996–99, including impacts of El Niño 1997–98 and La Niña 1999. Random-systematic line-transect surveys of marine mammals were conducted monthly from August to November 1996, and from May to November 1997–99. CTDs and zooplankton net tows were conducted opportunistically, and at 10 predetermined locations. Hydroacoustic backscatter was measured continuously while underway to estimate prevalence of zooplankton, with emphasis on euphausiids, a key trophic link between primary production and higher trophic level consumers.The occurrences of several of the California Current’s most common cetaceans varied among years. The assemblage of odontocetes became more diverse during the El Niño with a temporary influx of warm-water species. Densities of cold-temperate Dall’s porpoise, Phocoenoides dalli, were greatest before the onset of El Niño, whereas warm-temperate common dolphins, Delphinus spp., were present only during the warm-water period associated with El Niño. Rorqual densities decreased in August 1997 as euphausiid backscatter was reduced. In 1998, as euphausiid backscatter slowly increased, rorqual densities increased sharply to the greatest observed values. Euphausiid backscatter further increased in 1999, whereas rorqual densities were similar to those observed during 1998. We hypothesize that a dramatic reduction in zooplankton biomass offshore during El Niño 1997–98 led to the concentration of rorquals in the remaining productive coastal upwelling areas, including Monterey Bay. These patterns exemplify short-term responses of cetaceans to large-scale changes in oceanic conditions.     

Effects of the 1997–1999 El Niño and La Niña events on zooplankton abundance and euphausiid community composition within the Monterey Bay coastal upwelling system

Zooplankton abundance and euphausiid community composition were sampled seasonally (spring, summer, fall) within Monterey Bay, California, between 1997 and 1999. Measurements of sea surface temperature (SST), mixed layer depth, and upwelling indices provided concurrent data on physical oceanographic parameters. Both total zooplankton and krill abundance dramatically declined in the summer of 1997 coincident with a rapid increase in SST and mixed layer depth. Changes in euphausiid community composition occurred in concert with the decline in overall abundance. The relative abundance of the southern neritic Nyctiphanes simplex increased from August to November in 1997, the abundance of cold temperate Euphausia pacifica decreased significantly, and that of the northern neritic Thysanoessa spinifera declined dramatically. The sudden appearance of an adult cohort of N. simplex in July 1997 suggests that rapid poleward flow characteristic of coastally trapped Kelvin waves occurred between June and July of 1997. The persistent presence of warm temperate and subtropical taxa in samples collected between August 1997 and October 1998 indicates that this poleward flow continued in 1998. Zooplankton abundance, euphausiid community composition, and physical oceanographic parameters gradually returned to a more typical upwelling-dominated state in the spring and summer of 1998. E. pacifica and T. spinifera abundances gradually increased during the summer and fall of 1998, while N. simplex abundance abruptly declined in the spring of 1998. However, this recovery was confined to a narrow coastal band as a result of the onshore movement of the oceanic waters of the California Current. This was reflected by higher than normal numbers of the oceanic Nematoscelis difficilis within samples collected during the spring and summer of 1998. By the spring and summer of 1999, both zooplankton and euphausiid abundance had increased to the highest levels recorded during the 3-year study. Both E. pacifica and T. spinifera abundance increased relative to 1998 while N. simplex was completely absent in all samples. These changes reflected the cooler, highly productive environmental conditions associated with the 1998/1999 La Niña.     

普里兹湾水文特征与变化

根据澳大利亚学者分别在１９８２年１２月和１９８７年２月普里兹湾的调查资料,并结合中国＂极地＂号南极考察船１９９０～１９９１年间的调查资料印证,提出在中国＂中山站＂所在地普里兹湾在初夏与晚夏期间的水文特征。     

Effects of the Wind and Ice Conditions on the Upwelling along the Western Kamchatka Coast (Sea of Okhotsk) Based on the Satellite Data

The variability of the upwelling along the western coast of the Kamchatka Peninsula (northeastern part of the Sea of Okhotsk) has been studied based on an analysis of the multisensor satellite data. The intensity of upwelling is estimated on the basis of wind-forced offshore Ekman transport (upwelling index). The wind data for studying the seasonal variation of upwelling were collected in 1999–2009 using a Quik-SCAT/SeaWinds scatterometer. The upwelling events along the western Kamchatka coast were observed in December at the beginning of the winter monsoon period. During the period of strong winter monsoon northern winds from January to the middle of March, the drifting ice prevents the upwelling of the deep water at the western Kamchatka shelf edge under the mean conditions. The oceanographic data show that upwelling in the western coastal zone of Kamchatka was also observed during the transitional periods from winter to the summer monsoon (April). In summer, upwelling events are rarely observed in this region. The main cause of the summer upwelling is the propagation of the atmospheric cyclones over the Kamchatka Peninsula.     

Multi-platform remote sensing of new production in central California during the 1997–1998 El Niño

The effects of the 1997–1999 El Niño/La Nina event on new primary production are examined using a physiologically based algorithm of nitrate uptake by phytoplankton for the Monterey Bay, California region. Primary inputs for the model come from temperature and phytoplankton biomass (chlorophyll) using both moorings and satellite observations, providing estimates of new production with higher spatial and temporal resolution as compared to traditional shipboard measurements. We observed significant decrease in new production values during the El Niño event, and a corresponding enhancement during La Niña as compared to the values during the El Niño period. The observed interannual changes in new production varied as a function of distance from shore, consistent with the hypothesis that productivity offshore from the upwelling center was impacted because of the suppression of the thermocline and nitracline associated with the ENSO event. There was less evidence for a significant downstream trend in new production values, suggesting that distance from shore is the predominant variable in spatial estimates of new production.     

以各形态磷存量研究上升流水体老化变性指标

闽南-台湾浅滩渔场上升流区研究(1987年12月至1988年11月)及台湾海峡上升流区研究(1987年7月至1988年7月)结果表明,各种形态磷含量变化对上升流生态系具有重要作用.因此,提出以涌升水体中有机、颗粒形态磷和溶解无机态磷的相对比率来表示上升流水体的老化程度,即上升流水体老化指标(AIU)为(DOP+PP)与(DIP＋DOP＋PP)之比值.研究资料表明AIU这一表达式对于上述两上升流区是合适的,海域AIU的季节性变化与其近岸上升流的消长变化规律相一致.AIU较小的区域,其水体为新涌升水,与上升流中心位置相吻合.     

The circulation, water masses and sea-ice of Baffin Bay

The oceanographic, meteorological and sea-ice conditions in Baffin Bay are studied using historical hydrographic, satellite and meteorological data, and a set of current meter data from a mooring program of the Bedford Institute of Oceanography. Baffin Bay is partially covered by sea-ice all year except August and September. The interannual variation of the ice extent is shown to be correlated with winter air temperature. Available hydrographic data were used to study the water masses and the horizontal and vertical distribution of temperature/salinity. Three water masses can be identified – Arctic Water in the upper 100–300 m of all regions except the southeast, West Greenland Intermediate Water at 300–800 m in most of the interior of Baffin Bay, and Deep Baffin Bay Water in all regions below 1200 m. The temperature and salinity in Baffin Bay have limited seasonal variability except in the upper 300 m of eastern Davis Strait, northern Baffin Bay and the mouth of Lancaster Sound. Summer data have a temperature minimum at 100 m, which suggests winter convection does not penetrate deeper than this depth. Current meter data and results of a circulation model indicate that the mean circulation is cyclonic. The seasonal variation of the currents is complex. Overall, summer and fall tend to have stronger currents than winter and spring at all depths. Among the different regions, the largest seasonal variation occurs at the mouth of Lancaster Sound and the Baffin Island slope. Model generated velocity fields show a basic agreement with the observed currents, and indicate strong topographic control in the vicinity of Davis Strait and on the Greenland shelves. The model also produces a southward counter current on the Greenland slope, which may explain the observed high horizontal shears over the Greenland slope. Estimates of the volume and fresh water transports through Lancaster, Jones and Smith Sounds are reviewed. Transports through Davis Strait are computed from the current meter data. The balance of freshwater budget and sensitivity of the thermohaline circulation to freshwater transport are discussed.     

南黄海物理-生物地球化学过程的时空异质性及内在关联和机制

研究多重物理过程控制下陆架边缘海生物地球化学过程的时空异质性及其生态响应，对于深入认识海洋生态系统具有重要的意义。基于相关历史观测资料和卫星遥感海表温度，本文综合分析了南黄海物理-生物地球化学过程的时空变化和空间异质性特征，探讨了该海域内部典型地理单元之间的内在关联和机制。结果显示，冷季沿岸流南向输送和暖季锋面上升流垂向输运的季节性交替是影响石岛外海与海州湾外侧海域生物地球化学和初级生产的重要物理过程。夏季苏北沿岸水的东北向扩展可形成浒苔离岸/跨区域输送的动力驱动。暖季水体层化显著影响着南黄海中部冷水团海域的生物地球化学过程，春至秋季冷水团海域底层水体中的营养盐逐渐累积，形成了营养盐的重要贮库；层化季节黄海冷水团边界锋区上升流系统的存在使得南黄海叶绿素a和初级生产力高值区位置同海表低温涌升流区总体相一致。冷季南黄海西部南下的冷水与中部北向入侵的暖水共同导致了“S”型锋面的形成；暖季黄海冷水团边界锋区的上升流系统是连接层化海域和近岸区的纽带，可实现对冷水团内部营养盐的提取，从而将冷水团内部和边界区的生物地球化学过程形成有机连接，并在成山角-石岛外海、海州湾外侧、苏北浅滩东部形成三个典型的物理-生物地球化学相互作用区。本研究细化和整合了南黄海区域海洋学研究，揭示了该海域物理-生物地球化学过程的空间异质性特征和不同地理单元之间的关联性及机制，获得了对南黄海水文-生物地球化学-生态过程的综合、系统认知。