Inflow Of Oceanic Water Research Articles

SEASONAL VARIATION IN WATER CIRCULATIONS AND ITS IMPACT ON THERMAL ENVIRONMENT IN A CORAL REEF AREA OF SOUTHWEST JAPAN

Summer and wintertime observations were conducted through deploying horizontal oceanographic time series sensors in a coral reef region of Southwest Japan to assess the existing hydrodynamic and thermal environments in relation to seasonal changes. A significant variation in water circulation and temperature distribution pattern was recorded in Shiraho reef area between two different seasons. During winter, a strong inflow of oceanic water was recorded inside the reef on a semidiurnal pattern that led to significant water temperature rising while in summer, considerable amount of sea water entered the reef area with a diurnal frequency causing water temperature slightly lower. Outside the reef, current was found to flow nearly parallel in direction to the north-south stretch of the reef.

The interplay between plankton and particles in the Isfjorden waters influenced by marine- and land-terminating glaciers.

Climate-induced glacial retreat in the Arctic results in an increased supply of meltwater with suspended terrigenous material into the marine environment. Despite increasing research efforts, effects of glacial retreat on functioning of plankton are not well documented and understood. Thus, we studied a hydro-optical seawater regime along with particle/plankton concentrations and composition structure in a high Arctic fjord (Isfjorden, West Spitsbergen) during mid-summer in 2019. This comprehensive study of the upper 50m water layer presented a sharp distinction between 'muddy' waters influenced by glacial and river runoff and 'clear' open fjordic waters in the form of a notable difference in chlorophyll a concentrations, extent of euphotic zone depth, turbidity, inorganic/organic particle concentrations, and water colour. In this study, we present that the effects of glacial retreat on Arctic pelagial depend not only on different types of glaciers (marine- and land-terminating), but presumably, also on fjord topography and exposure to oceanic water inflow. The contrasting glacial, hydrological, and topographical conditions had different effects on the share of zooplankton and marine snow. Despite adaptation of the planktonic communities in the Arctic to high sediment loads and resultant light limitations, our study shows that continuing retreat of tidewater glaciers will have negative effect on planktonic communities especially in enclosed shallow fjord branches. Moreover, seawater darkening due to high turbidity could negatively affect tactile predators, such as gelatinous zooplankton. Additional division of plankton into functional groups typically used in the biogeochemical models demonstrated that diatoms, flagellates and mesozooplankton are influenced by suspended matter, whereas microzooplankton are highly adaptive to increased sediment loads. Since we investigated the largest Svalbard fjord system and incorporated multiple components of the pelagic realm, the current study delivers important recommendations for including marine snow and gelatinous zooplankton in ecosystem models applied in polar regions.

Arctic multiyear sea ice variability observed from satellites: a review

In comparison with seasonal sea ice (first-year ice, FY ice), multiyear (MY) sea ice is thicker and has more opportunity to survive through the summer melting seasons. Therefore, the variability of wintertime MY ice plays a vital role in modulating the variations in the Arctic sea ice minimum extent during the following summer. As a response, the ice-ocean-atmosphere interactions may be significantly affected by the variations in the MY ice cover. Satellite observations are characterized by their capability to capture the spatiotemporal changes of Arctic sea ice. During the recent decades, many active and passive sensors onboard a variety of satellites (QuikSCAT, ASCAT, SSMIS, ICESat, CryoSat-2, etc.) have been used to monitor the dramatic loss of Arctic MY ice. The main objective of this study is to outline the advances and remaining challenges in monitoring the MY ice changes through the utilization of multiple satellite observations. We summarize the primary satellite data sources that are used to identify MY ice. The methodology to classify MY ice and derive MY ice concentration is reviewed. The interannual variability and trends in the MY ice time series in terms of coverage, thickness, volume, and age composition are evaluated. The potential causes associated with the observed Arctic MY ice loss are outlined, which are primarily related to the export and melting mechanisms. In addition, the causes to the MY ice depletion from the perspective of the oceanic water inflow from Pacific and Atlantic Oceans and the water vapor intrusion, as well as the roles of synoptic weather, are analyzed. The remaining challenges and possible upcoming research subjects in detecting the rapidly changing Arctic MY ice using the combined application of multisource remote sensing techniques are discussed. Moreover, some suggestions for the future application of satellite observations on the investigations of MY ice cover changes are proposed.

The net water circulation in the far Northern Great Barrier Reef

The 500 km long Far Northern Great Barrier Reef (FNGBR) is a semi-enclosed sea with little connectivity with the rest of the GBR further South. Its mean circulation is controlled by the prevailing southeasterly (northwestward) wind that generates a wind-driven mean longshore flow that is enabled by an inflow of oceanic water in the South. From an examination of single-point, mid-depth current meter data at ten sites over one year, it appears that there is no net current during calm weather, which implies that the northward North Queensland Coastal Current in the adjoining Coral Sea does not intrude in the FNGBR. Only about 20–40% of the wind-driven longshore transport continues northward to exit the FNGBR through Torres Strait because of blockage by reefs, shoals and islands and by the tidal friction effect in shallow waters. The remaining 60–80% of the flow appears to be deflected seaward to the Coral Sea in the North, an observation that appears to be supported by oceanographic modelling. This situation differs from that in the central and southern Great Barrier Reef where the southward flowing East Australian Current intrudes on the shelf and generates a net current even during calm weather.

The influence of ocean heat transport in the Barents Sea on the regional sea ice and the atmospheric static stability

The influence of the oceanic heat inflow into the Barents Sea on the sea ice concentration and atmospheric characteristics, including the atmospheric static stability during winter months, is investigated on the basis of the results of ensemble simulations with the regional climate model HIRHAM/NAOSIM for the Arctic. The static stability of the atmosphere is the important indicator of the spatial and temporal variability of polar mesocyclones in the Arctic region. The results of the HIRHAM/NAOSIM regional climate model ensemble simulations (RCM) for the period from 1979 to 2016 were used for the analysis. The initial and lateral boundary conditions for RCM in the atmosphere were set in accordance with the ERA-Interim reanalysis data. An analysis of 10 ensemble simulations with identical boundary conditions and the same radiation forcing for the Arctic was performed. Various realizations of ensemble simulations with RCM were obtained by changing the initial conditions for integrating the oceanic block of the model. Different realizations of ensemble simulations with RCM are obtained by changing the initial conditions of the model oceanic block integration. The composites method was used for the analysis, i.e. the difference between the mean values for years with the maximum and minimum inflow of oceanic water into the Barents Sea. The statistical significance of the results (at a significance level of p < 0.05) was estimated using Student's t-test. In general, the regional climate model reproduces the seasonal changes in the inflow of the oceanic water and heat into the Barents Sea reasonably well. There is a strong relationship between the changes in the oceanic water and ocean heat inflow, sea ice concentration, and surface air temperature in the Barents Sea. Herewith, the increase in the oceanic water inflow into the Barents Sea in winter leads to a decrease in static stability, which contributes to changes in regional cyclonic activity. The decrease of the static stability is most pronounced in the southern part of the Barents Sea and also to the west of Svalbard.

Improvement in the dissolved oxygen concentration and water exchange in Ofunato Bay, Japan, after the collapse of the bay‐mouth breakwater by the 2011 Tohoku Earthquake and tsunami

AbstractOyster and scallop aquaculture has flourished in Ofunato Bay, on the Sanriku Coast of Japan. Between 1967 and 2011, this bay was a highly enclosed area by a bay‐mouth breakwater, and while the breakwater provided calm conditions suitable for aquaculture, there was concern about water quality deterioration. The Tohoku Earthquake off the Pacific coast and the subsequent major tsunami on 11 March 2011 caused extensive damage to the Sanriku Coast, resulting in the collapse of the breakwater of Ofunato Bay. We analyzed the monthly hydrographic observational data that were collected between 1996 and 2015, supplemented with hydrographic observations and direct current measurements that were carried out after the earthquake. The historical hydrographic observational data showed the lowest dissolved oxygen (DO) concentrations were observed near the bottom in the bay. The average and standard deviation of the lowest DO concentrations of each monthly observation during the period before and after the earthquake were 5.81 ± 3.72 and 7.22 ± 1.49 mg L−1, respectively, and are significantly different. The oceanic water inflow and water exchange rate estimated by a box model based on the salt budget under the steady‐state estuarine circulation were also significantly different before and after the earthquake. An increase in the inflow of oceanic water and the more rapid water exchange in the bay after the earthquake induced marked improvements in the bottom DO concentration. These changes are considered to be attributable to the improved circulation of oceanic water in the bay that resulted from the collapse of the bay‐mouth breakwater.

Fortnightly switching of residual flow drivers in a tropical semiarid estuary

Current velocity and hydrographic measurements were obtained in Mossoró estuary, a tropical semiarid estuary in Northeastern Brazil, to explore the hydrodynamic regime associated with marked seasonal variability in evaporation and precipitation. Measurement campaigns were performed during dry conditions in October 2012 and wet conditions in May 2013. Dry season observations showed along-estuary density gradients of order 0.001 kg/m4 with salinity increasing upstream in the first 20 km up to a value of 70 g/kg. Salinity then decreased to a value of 48 g/kg at the upstream limit of the section. During this dry season, the residual flow structure changed drastically from spring to neap tides. Neap tide residual flows showed inflow of oceanic water at the surface and outflow of hypersaline water underneath. Spring tide residual flows showed net inflow throughout the water column in the middle of the section and outflow over the flanks, a laterally sheared structure consistent with tidally induced residual flows. In the wet season, along-estuary density gradients were of similar magnitude to the dry season but in the opposite direction. Residual flows in neap tides were as expected for density-driven flows: outflow at surface and inflow underneath. During spring tides, residual flows were dominated by outflows over the flanks and inflow in the middle of the section, once again consistent with tidally driven residuals. Advective accelerations from tides were compared to baroclinic pressure gradients, in the non-dimensional tidal Froude number (Fr0), to explore the changes from tidally driven to density-driven residual flows. Results indicated that residual flows in this estuary were driven by tidal rectification (Fr0 >> 1) in spring tides and by density-gradients (Fr0 << 1) in neap tides. Thus, estuarine residual flows switch from density-driven in neaps to tidally driven in springs. In general, it is proposed that the switch can be diagnosed with Fr0.

鹿児島湾への外洋水の流入に及ぼす大隅分枝流の影響について

Properties of the current velocity index of the Osumi Branch Current (OBC) in the Osumi Strait south of Kyushu were re-examined using sea-level data during 1971-2003. The high correlation with the current velocity measured in the Osumi Strait confirmed that the sea-level difference between Nishino-omote and Odomari is a good index to monitor the current velocity of the OBC. Using daily values of the index and water temperature measured in Kagoshima Bay in 1999, it is found that the current velocity fluctuations of the OBC with periods less than about 8 days significantly contribute to oceanic water inflow into Kagoshima Bay. Moreover, the oceanic water is shown to reach to the central part of Kagoshima Bay about 1.3 day after it enters into the bay along the Osumi Peninsula.

2004년 7월 봇돌바다의 영양염과 chlorophyll-a의 단기 변동

In order to study the temporal variations of nutrients and chlorophyll-a in the Bottol Bada, three field observations were carried out on 20, 23 and 26 July, 2004. The low N:P values exhibit nitrogen deficiency during the periods of observation. This result is not representative of typical summer environment in the southern coast of Korea. The possible mechanisms are as follows: 1) The freshwater inflow was not sufficient for the supply of nitrogen because the total precipitation was 11.9 mm in July, 2004. This amount is no more than in normal precipitation in July. 2) There was an inflow of oceanic water under the subsurface into the Bottol Bada. Even though the oceanic water comprises more nutrients, it produces the stratification between the surface and the subsurface water and seems to prevent the supply of nutrinets to the surface layer. 3) The high chlorophyll-a concentration of was shown near the narrow channel between Gae-do and Geumo-do. This seems to be resulted from the inflow of water from Gamak Bay.

Inflow of oceanic water into Tokyo Bay and generation of a subsurface hypoxic water mass

Temporal and spatial variations in the inflow of oceanic water into Tokyo Bay and the accompanying changes in circulation within the bay have been studied by repeated measurement of the longitudinal distributions of hydrographic parameters and oxygen concentration from the bay head to off the bay mouth. Data collection took place in summer 1998 with the particular aim of tracking the movement of a hypoxic water mass. Density changes in the upper ocean induce inflow and outflow of oceanic water in the bay so that when water density increased in the upper ocean, heavy saline water intruded into the lower layer of the bay. This inflow forced a “bottom hypoxic water mass” to the bay head and, finally, lifted it up to form a “subsurface hypoxic water mass,” which then moved out as a thin layer just under the pycnocline, reaching beyond the bay mouth. When the intruding heavier deep water retreated and an intrusion of oceanic water at intermediate depth occurred, the hypoxic water mass was displaced from the center to the mouth of the bay. The bottom hypoxic water mass dominates in the northern half of the bay, while the subsurface oxygen minimum appears frequently in the southern half.

Water renewal time for classification of atoll lagoons in the Tuamotu Archipelago (French Polynesia)

The feasibility of using hydrodynamic renewal time as the basis for a classification of atoll lagoons is tested for atolls of the Tuamotu Archipelago, French Polynesia. Renewal time depends on the inflow of oceanic water through the rim of the atoll, on a daily time scale, due to wave forcing. Renewal time is computed for a large set of morphologically diverse atolls, according to significant wave height (satellite altimetry data), morphometric indicators (high-resolution satellite images), and in-situ flow measurements. Renewal times with respect to wave height are presented for a variety of atolls. Renewal times range from less than 1 day for very open and shallow atolls, to several tens of days for semi-open moderately deep atolls, and to several years for closed or very large and deep atolls. Comparisons between phytoplanktonic biomass (in the range 0.1 to 1 µg l–1 for total chlorophyll) and renewal time (0.1 to 130 days) leads to the identification of two groups of atolls. We obtain a significant relationship between biomass and renewal time, but only for atolls with lagoon surface areas greater than 25 km2.

Is there a connection between high transport of water through the Rockall Trough and ecological changes in the North Sea?

Changes in the ecosystem of the North Sea may occur as pronounced inter-annual and step-wise shifts as well as gradual trends. Marked inter-annual shifts have occurred at least twice in the last two decades, the late 1980s and the late 1990s, that appear to reflect an increased inflow of oceanic water and species. Numerical modelling has demonstrated a link between altered rates of inflow of oceanic water into the northern North Sea and a regime shift after 1988. In 1989 and 1997 oceanic species not normally found in the North Sea were observed there, suggesting pulses of oceanic water had entered the basin and triggered the subsequent ecosystem change. The oceanic water has origins mainly west of Britain in the Rockall Trough, where the long-term mean volume transport is around 3.7 Sv northwards (1 Sv=10 6 m3s-1), but in early 1989 and early 1998 was observed to be more than twice the mean value, reaching over 7 Sv. These periods of high transport coinciding with the inferred pulses of oceanic water into the North Sea suggest a connection through the continental shelf edge current.

Late Holocene palaeoceanography in Van Mijenfjorden, Svalbard

Based on detailed stratigraphical analysis of sediment cores spanning the last ca. 4000 calendar years, we reconstruct the palaeoceanograhic changes in the fiord Van Mijenfjorden, western Svalbard. Benthic foraminiferal ?18O indicate a gradual reduction in bottom water salinities between 2200 BC and 500 BC. This reduction was probably mainly a function of reduced inflow of oceanic water to the fiord, due to isostatic shallowing of the outer fiord sill. Stable salinity conditions prevailed between 500 BC and. 1300 AD. After the onset of a major glacial surge of the tidewater Paulabreen (Paula Glacier) system (PGS) around 1300 AD, there was a foraminiferal faunal change towards glacier proximal conditions, associated with a slight bottom water salinity depletion. During a series of glacial surges occuring from 1300 AD up the present salinity in the fiord has further decreased, corresponding to a ?18O depletion of 0.5 %o. This salinity decrease corresponds to the period when the PGS lost an equivalent of 30 – 40 % of its present ice volume, mainly through calving in the fiord.

Temporal and spatial stability of bacterioplankton biomass and productivity in an atoll lagoon

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 11:251-261 (1996) - doi:10.3354/ame011251 Temporal and spatial stability of bacterioplankton biomass and productivity in an atoll lagoon Torréton JP, Dufour P Spatial and temporal variations of bacterioplankton biomass, production and growth rates were investigated 6 times from 1991 to 1994 in Tikehau lagoon (Tuamotu, French Polynesia). The water column was homogeneous from the surface to the bottom (20 m) at the reference station but some horizontal variations were detected, with biomass and production increasing from the reef-flat spillways (oceanic water inflow) to the main part of the lagoon and decreasing from the relatively eutrophic shore (near the village) to the main part of the lagoon. However, both of these perturbations were limited to the immediate vicinity of these areas. Diel fluctuations of bacterial biomass and growth rate were slight (coefficient of variation, CV < 20%) and showed no significant pattern. Day-to-day variations recorded over periods of up to 20 consecutive days appeared also to be limited (CV < 25%). A significant correlation between wind and total abundance of bacteria in the water column suggested that these day-to-day variations may be in part explained by wind, probably inducing resuspension of sediments. No significant pattern appeared from comparison of the 6 cruises spread over different seasons. Cruise averages differed slightly from each other, with CV for all cruises averaging 34, 10 and 41% for bacterioplankton biomass, production and growth rate, respectively. Tikehau lagoon appears to be a very stable ecosystem for bacterioplankton processes and therefore differs strongly from other reef water column systems. This untypical stability might be explained by the long residence time of water (170 d), the strong stability of the oceanic surrounding water (South Pacific Gyre), the weak seasonality of primary producers and the limited inputs from corals, bordering islands and sediments. Bacterioplankton · Bacterial production · Thymidine incorporation · Leucine incorporation · Atoll lagoon · Pacific Ocean Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 11, No. 3. Publication date: December 31, 1996 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 1996 Inter-Research.

Wind-dependent formation of phytoplankton spring bloom in Otsuchi Bay, a ria in Sanriku, Japan

Spring blooms of phytoplankton composed of centric diatoms developed in late February, March, and April in Otsuchi Bay on Sanriku ria coast, Japan. During this period, associated with prolonged seasonal west wind (>1 day), intense exchange of waters occurred between inside and outside the bay: outflow of nearsurface brackish water over inflow of oceanic water at depth. This circulation interrupted formation of the blooms, and transported phytoplankton populations seaward. By such water movements, a significant amount of nutrients in the bay was carried out, otherwise replenished into the bay, depending on water masses located outside the bay. Owing to irregular features of wind events, a bloom lasted from several days to a week. From February to April, supply of nutrients seemed to be replete except for the latter half of the bloom period, and estimates of the critical depth exceeded the depth of the bottom consistently. Thus, net growth of phytoplankton was expected throughout the observation period, and potentially blooms could be formed. However, the blooms were only formed under calm weather. We hypothesize that the exchange of waters dilutes populations in the bay, and that formation of the bloom, that is, accumulation of biomass depends on a balance between the growth of phytoplankton and the dilution of bay water.

Models for circulation patterns in epicontinental seas applied to Paleozoic facies of North America craton

Circulation in epicontinental seas develops in response to thermohaline, wind‐driven, and tidal motions in various climatic, geographic, and bathymetric settings. Mass balance relations in a seaway are established by the relative rates of outflow, inflow (freshwater and ocean water), and evaporation, which constrain two contrasting styles of epicontinental circulation. Quasietuarine circulation (QEC) is established where rates of freshwater influx exceeds evaporation. Surface outflow from a seaway with QEC typically is balanced by inflow of oceanic water at depth. A density stratification can be established below the limits of vertical mixing. A bottom layer of oxygen poor or anoxic water may develop in a seaway with or without an entrance sill if the bottom waters are derived from the oxygen minimum zone of the open ocean or if organic productivity exceeds the limits of aerobic respiration. Upwelling may be promoted in specific epicontinental settings with QEC. Antiestuarine circulation (AEC) is developed in arid climates where evaporation exceeds freshwater influx. Evaporative concentration in the surface layer causes oxygenated water to sink. Bottom outflow of denser, more saline water is balanced by surface inflow from the open ocean. A sill or barrier may inhibit bottom circulation in seas with AEC, permitting development of a basal brine layer. Stagnation in the brine layer may lead to oxygen depletion. Seas with AEC commonly are characterized by extensive carbonate‐evaporite facies. Geographic and stratigraphic syntheses of lithofacies and biofacies provide the empirical basis for interpretations of seaway dynamics in ancient epicontinental settings. Examples from the Upper Ordovician (Maquoketa formation) and Upper Devonian (Lime Creek‐Sweetland Creek formations) of cratonic North America are interpreted in the context of stratified QEC patterns. In each case, oxygen poor to anoxic waters appear to have impinged along the basin slope below the margin of an oxygenated carbonate shelf. Upwelling along the shelf margin in the Maquoketa example helps explain the distribution of phosphatic sediments. A stratified AEC pattern is interpreted for the Gower formation (Silurian) of eastern Iowa. A barrier to bottom circulation at the mouth of an embayment in the epicontinental sea resulted in a basal layer of hypersaline water devoid of shelly benthos. Surface water salinities increased progresively shoreward within the embayment, but benthic organisms flourished where carbonate mounds built upward into the oxygenated layer.

Caractéristiques générales du milieu liquide lagonaire de l'atoll de Takapoto

Caractéristiques générales du milieu liquide lagunaire de l'atoll de Takapoto. As the lagoon of the Takapoto atoll is not linked with the ocean, its waters have different physicochemical properties from those of the Pacific ocean. The local hydroclimatical measures since 1974, indicate that the important variation of the salinity of the lagoon waters is in close relation to the precipitation-evaporation ratio; the inflow of oceanic water by some shallow passes (hoa) restitutes the level of the lagoon sporadically, but the lagoon — ocean transfers are practically negligible. The atoll being in an area of strong evaporation, the excess of salt is evacuated through the porous coral mass by a liquid junction as explained in the proposed diagram.

Wind-driven circulation in a Spanish estuary

The Ría de Arosa, located on the Atlantic coast of northwest Spain (Galicia), is highly productive of mussels. The nutrients required to support this fishery apparently are supplied to the estuary by an inflow of oceanic water ( S ∼- 35·6‰) along the bottom while surface waters are being blown out to sea by northeasterly winds. Salinity, which has been observed (K. R. Tenore, personal communication) to correlate positively with the abundance of nutrients within the estuary, is used as a tracer. The salinities observed in two seasons at various locations in the estuary are shown to vary with the wind flow as indicated by weather maps and by an assessment of topographical influence.

The distribution of some plankton animals in the English Channel and approaches: ii. Surveys with the Gulf iii high-speed sampler, 1958-60

SUMMARYComparison of the recent surveys with investigations back to 1903 confirms earlier suggestions of a general tendency towards an increase in southern forms (including south-western species) and a decrease in northern forms (including north-western species) in the western English Channel, although there has been considerable fluctuation from time to time. These and other biological changes in the area during the past 58 years are believed to be largely a result of rising temperatures and a consequent general shifting of boundaries of distribution. There appears to be no real evidence that the changes in plankton distribution are due to a change in fertility in the water or of variation in strength of inflow of oceanic water. However, these aspects cannot be separated from the changes that have taken place in populations of fish, and will be discussed further in a later paper.