Outer Ocean Research Articles

Distribution of blue and sei whale vocalizations, and temperature - salinity characteristics from glider surveys in the Northern Chilean Patagonia mega-estuarine system

Northern Chilean Patagonia is a mega-estuarine system where oceanic waters mix with freshwater inputs in the coastal fjords, channels and gulfs. The aim of this study was to examine the distribution of blue and sei whales with respect to oceanographic conditions of the study area from the estuarine inner sea to the outer ocean. Ocean gliders were used, mounted with a hydrophone to determine acoustic presence of whales (Southeast Pacific and Antarctic blue whale song calls, and blue whales D-calls; sei whale downsweeps and upsweeps), and a temperature and salinity instrument. Four glider deployments were carried out in April 2018 and April-June 2019 navigating a total of 2817 kilometers during 2110 hours. To examine interannual variation, the average percentage of day with presence of calls was compared between years using the adjusted p-values for one-way ANOVA and descriptive statistics. To examine spatial variation between the hourly acoustic presence of blue whales and sei whales and temperature and salinity conditions, Generalized Linear Models (GLMs) were used. Salinities were higher in 2019 compared to 2018. Southeast Pacific blue whales produced song calls throughout the study area in both years, across estuarine and oceanic areas, but percentage of day with presence was higher in 2019 vs 2018. Percentage of day with presence of D-calls was similar between years, but higher in oceanic areas during both study periods. In contrast, the spatial pattern of sei whale acoustic presence was ambiguous and interannual variability was high, suggesting that sei whales preferred estuarine areas in 2018 and oceanic areas in 2019. We discuss possible explanations for observed acoustic presence in relation to foraging behavior and prey distribution.

Evaluation of origin-depended nitrogen input through atmospheric deposition and its effect on primary production in coastal areas of western Kyusyu, Japan

Long term monitoring of atmospheric wet and dry depositions and associated nutrients fluxes was conducted on the coast of Japan facing the East China Sea continuously for 1 year and 2 months, with the origin of air mass investigated based on isotope analyses (Sr, Nd, and NO3). During the same period, intensive observations of ocean conditions and the chemical composition of sinking particles collected using sediment traps were conducted to investigate the effects of atmospheric deposition-derived nutrients on phytoplankton blooms. Dry-deposition-derived nutrient inputs to the surface ocean were larger during autumn to spring than in summer due to the effect of continental air mass occasionally carrying Asian dust (yellow sand). However, these nutrients fluxes were limited (1.1–1.5 mg-N m−2 day−1 on average) and didn't appear to cause phytoplankton blooms through the year. Although average dissolved inorganic nitrogen (DIN) concentrations in rainwater were lower in oceanic air masses compared to continental air masses, wet-deposition-derived nutrient inputs to the surface ocean on rainy days during the summer (26.0 mg-N m−2 day−1 on average) were large due to higher precipitation from oceanic air masses. Wet-deposition-derived nutrients significantly increased nutrient concentrations in the surface ocean and seemed to cause phytoplankton blooms in the warm rainy season when nutrients in the surface were depleted due to increased stratification. The increase in phytoplankton biomass was reflected in increased particle sinking into the bottom layer, as well as changing chemical characteristics. The supply of flesh phytoplankton-derived labile organic matter into the bottom layer could be expected to promote rapid bacterial decomposition and contribute to the formation of hypoxic water masses in early summer when the ocean was strongly stratified. Atmospheric deposition-derived nutrients in East Asia will have important impacts on not only the oligotrophic outer ocean but also surrounding coastal areas in the warm rainy season.

Hydrothermal formation of iron-oxyhydroxide chimney mounds in a shallow semi-enclosed bay at Satsuma Iwo-Jima Island, Kagoshima, Japan

Abstract Hydrothermal iron-oxyhydroxide chimney mounds (iron mounds) have been discovered in a fishing port in Nagahama Bay, located on the southwest coast of Satsuma Iwo-Jima Island, south of Kyushu Island, Japan. In the fishing port, uncovered ∼1.0-m-high iron mounds in shallow waters formed under relatively calm conditions. Typically, the fishing port has orange-colored turbid waters that mix with outer ocean waters during high tide. Colloidal iron-oxyhydroxides form due to the oxidation of ferrous iron in hydrothermal waters (pH = 5.5; temperature = 55 °C) as they mix with seawater. The mounds are made of two types of material: hard, dark brown–orange, high-density material; and soft, brownish orange–yellow, low-density material. Computed tomography scans of the harder iron mound material revealed a cabbage-like structure consisting of micropipe structures with diameters of 2–5 mm. These micropipes have relatively hard walls made of iron oxyhydroxides (FeOH) and are identified as discharge pipes. Nucleic acid staining genetic sequencing and scanning electron microscope observations suggest that the mounds formed mainly from bacterial stalks with high concentrations of FeOH colloidal matter. In the harder parts of the mounds, these “fat stalks,” which contain oxyhydroxide colloidal aggregates, are entwined and concentrated. The softer material contains twisted stalk-like structures, which are coated with FeOH colloidal particles. Deoxyribonucleic acid (DNA) examination of the iron mounds revealed the presence of iron-oxidizing bacteria, especially at the mound surface. We estimate that the iron mounds accumulated at a rate of ∼1700 tons/1000 m2/yr. This is an order of magnitude higher than the rate of FeOH sedimentation via chemical precipitation of FeOH colloids within the fishing port. This suggests that biogenic activity, resulting in the production of entwined FeOH stalks, leads to the rapid accumulation of FeOH beds and that biogenic activity within the water mass rich in FeOH colloids is an efficient means of generating thick iron-rich sedimentary sequences. As such, we propose that some ancient iron formations may have also formed through the biogenic production of FeOH stalks rather than solely through chemical sedimentation in a water mass rich in FeOH colloids. It appears that these rapidly forming biogenic FeOH iron mounds, distributed over a wide area of ocean floor, are also relatively protected from erosion and diagenetic alteration (reduction). Previous studies have reported that ancient iron formations were commonly deposited in deeper environments via direct iron oxidation from the water column in a ferruginous ocean. However, there are several hydrothermal vent inflows preserved with FeOH that would have formed appropriate redox boundary conditions in an otherwise anoxic ocean. Under these conditions, iron mound mat-type sedimentary deposits might have formed and been well preserved and affected by early diagenesis where higher heat flow occurred in the Archean ocean. The FeOH mounds in Nagahama Bay provide an example of the iron formation sedimentary environment and important information for estimating the past depositional state of iron formations.

Post-release behaviors and movements of cultured and wild Japanese eels (Anguilla japonica) in a shallow brackish water lagoon in northeastern Japan

A total of 30 cultured [610.6 ± 24.0 mm total length (TL)] and six wild Japanese eels Anguilla japonica collected on site (622.2 ± 133.1 mm TL) were tagged with acoustic transmitters and released into a shallow brackish water lagoon in northeastern Japan in June 2014 and July–October 2014, respectively; their post-release movements in the entire lagoon were monitored by acoustic receivers. We found that the cultured and wild eels had some common features, such as nocturnal activity and the exploitation of a wide range of brackish environments and occasionally river excursions at night from the lagoon. However, the total periods of detection and seaward movement behaviors differed between the cultured and wild eels, with 26 cultured eels no longer being detected within 6 months, whereas four wild eels were detected for >6 months. In total, 12 cultured eels moved into the outer ocean (potentially seaward migration) in October after typhoons passed and in November after the water temperature decreased (13.8 ± 1.2 °C), as opposed to the wild eels. While the contribution of the cultured eels to reproduction after the seaward movement remains unknown, these findings showed that they remained in the lagoon only for a limited time.

Response of an Antarctic Peninsula Fjord to Summer Katabatic Wind Events

AbstractFjords along the western Antarctic Peninsula are episodically exposed to strong winds flowing down marine-terminating glaciers and out over the ocean. These wind events could potentially be an important mechanism for the ventilation of fjord waters. A strong wind event was observed in Andvord Bay in December 2015, and was associated with significant increases in upper-ocean salinity. We examine the dynamical impacts of such wind events during the ice-free summer season using a numerical model. Passive tracers are used to identify water mass pathways and quantify exchange with the outer ocean. Upwelling and outflow in the model fjord generate an average salinity increase of 0.3 in the upper ocean during the event, similar to observations from Andvord Bay. Down-fjord wind events are a highly efficient mechanism for flushing out the upper fjord waters, but have little net impact on deep waters in the inner fjord. As such, summer episodic wind events likely have a large effect on fjord phytoplankton dynamics and export of glacially modified upper waters, but are an unlikely mechanism for the replenishment of deep basin waters and oceanic heat transport toward inner-fjord glaciers.

Projecting of wave height and water level on reef-lined coasts due to intensified tropical cyclones and sea level rise in Palau to 2100

Abstract. Tropical cyclones (TCs) and sea level rise (SLR) cause major problems including beach erosion, saltwater intrusion into groundwater, and damage to infrastructure in coastal areas. The magnitude and extent of damage is predicted to increase as a consequence of future climate change and local factors. Upward reef growth has attracted attention for its role as a natural breakwater, reducing the risks of natural disasters to coastal communities. However, projections of change in the risk to coastal reefs under conditions of intensified TCs and SLR are poorly quantified. In this study we projected the wave height and water level on Melekeok reef in the Palau Islands by 2100, based on wave simulations under intensified TCs (significant wave height at the outer ocean: SWHo = 8.7–11.0 m; significant wave period at the outer ocean: SWPo = 13–15 s) and SLR (0.24–0.98 m). To understand effects of upward reef growth on the reduction of the wave height and water level, the simulation was conducted for two reef condition scenarios: a degraded reef and a healthy reef. Moreover, analyses of reef growth based on a drilled core provided an assessment of the coral community and rate of reef production necessary to reduce the risk from TCs and SLR on the coastal areas. According to our calculations under intensified TCs and SLR by 2100, significant wave heights at the reef flat (SWHr) will increase from 1.05–1.24 m at present to 2.14 m if reefs are degraded. Similarly, by 2100 the water level at the shoreline (WLs) will increase from 0.86–2.10 m at present to 1.19–3.45 m if reefs are degraded. These predicted changes will probably cause beach erosion, saltwater intrusion into groundwater, and damage to infrastructure, because the coastal village is located at ∼ 3 m above the present mean sea level. These findings imply that even if the SWHr is decreased by only 0.1 m by upward reef growth, it will probably reduce the risks of costal damages. Our results showed that a healthy reef will reduce a maximum of 0.44 m of the SWHr. According to analysis of drilled core, corymbose Acropora corals will be key to reducing the risks, and 2.6–5.8 kg CaCO3 m−2 yr−1, equivalent to > 8 % of coral cover, will be required to keep a healthy reef by 2100. This study highlights that the maintaining reef growth (as a function of coral cover) in the future is effective in reducing the risk of coastal damage arising from wave action. Although the present study focuses on Melekeok fringing reef, many coral reefs are in the same situation under conditions of intensified TCs and SLR, and therefore the results of this study are applicable to other reefs. These researches are critical in guiding policy development directed at disaster prevention for small island nations and for developing and developed countries.

Horizontal movement and emigration of juvenile spotted halibut Verasper variegatus released in a shallow brackish lagoon: Matsukawa-ura, northeastern Japan, revealed by acoustic telemetry

To elucidate the post-release movement and emigration of juvenile spotted halibut Verasper variegatus, ten hatchery-reared age-0 individuals (10 months old, 17.0–19.7 cm total length) surgically implanted with acoustic transmitters were released near the center of Matsukawa-ura, a shallow brackish lagoon, on 25 November 2009 (water temperature 13.8 °C). They were monitored by ten acoustic receivers for 5 months. Of ten individuals, eight left the release site during December–March. Three of these emigrated to the outer ocean on 17 and 29 January and 30 March 2010, respectively. Juveniles probably started wintering migration in December and January when water temperatures decreased considerably in the lagoon (mean 9.5 and 6.0 °C, respectively). They stopped their migration in the coldest month, February (mean 5.7 °C), and restarted it in March when water temperatures frequently exceeded a plausible threshold for movement (≥6 °C). Statistical analyses revealed that the fish started migration significantly more frequently at nighttime. The migration track of an individual recorded from 11 to 30 March showed gradual nocturnal movements and a slow migration speed (estimated maximum speed 2.2 m/min). Our results revealed that water temperature primarily governed the seasonal timing of nocturnal migratory movements of juvenile spotted halibut.

Dispersion Relation for Continental Shelf Waves When the Shallow Shelf Part Has an Arbitrary Width: Application to the Shelf West of Norway

AbstractThe dispersion relation for continental shelf waves (CSWs) in a shelf region with an unbounded flat outer ocean, a convex-upward exponential shelf, and an interior flat region of arbitrary width D is derived. The calculations allow for a nonzero divergence of the wave motion. Some consequences of these findings are discussed for the shelf west of Norway, where the shelf at mid-Norway is quite wide, while at Lofoten it is much narrower. Furthermore, north of Lofoten, along the opening to the Barents Sea, the shelf becomes extremely wide. In this region the conditions are nearly met for a double Kelvin wave. The paper discusses how CSWs generated along the common storm track outside southwest Norway modify as they travel along the shelf. The analytical results are compared with results from a numerical barotropic ocean model with realistic shelf topography.

Developing a flow control strategy to reduce nutrient load in a reclaimed multi-reservoir system using a 2D hydrodynamic and water quality model

Blocking the natural bi-directional flow in an estuarine system using an artificial dyke has commonly caused serious water quality problems. In the southwestern part of South Korea, a parallel triple-reservoir system was constructed by blocking the mouth of three different rivers (Yeongsan, Okcheon, and Kumja), which were then interconnected using two open channels. This system has experienced a deterioration in water quality due to pollutants accumulated from the upper watershed, and has continually discharged pollutant loads to the outer ocean. Therefore, the objective of this study is to establish an effective dam operation plan for reducing nutrient loads released from the integrated reservoir. In this study, the CE-QUAL-W2 model, which is a 2-dimentional hydrodynamic and water quality model, was applied to predict the pollutant load released from each reservoir in response to different flow scenarios for the interconnecting channel. The model was calibrated using two novel methods: a sensitivity analysis to determine meaningful model parameters, and a pattern search to optimize the parameters. From the scenario analysis using flow control, it was determined that the total nitrogen (TN) and total phosphorus (TP) loadings could be reduced by 27.2% and 6.6%, respectively, under the optimal channel flow scenario by regulating the chlorophyll-a concentration in the reservoir. The results confirm that effective dam operation could contribute to a decrease in pollutant loads in the receiving seawater body. As such, this study suggests operational strategies for a multi-reservoir system that can be used to reduce the nutrient load being discharged from reservoirs.

Environmental controls at multiple scales for the western Pacific: An Okinawan case study

In this study, the principal controls on the coastal environment around the Pacific island of Okinawa, typical of the many mountainous islands of the sub-tropical and tropical northwest Pacific in the arc from Melanesia to the Ryukyu Islands, are investigated. Two principal satellite remote sensing data products were used to observe properties at regional-scale and in the Okinawan coastal zone: (1) AVHRR sea surface temperature (SST) for 1985–2006 and (2) a SeaWiFS ocean colour variable to estimate combined sediment and chlorophyll-a loadings for 1998–2006, along with direct observations (e.g. climatological data, river discharge, suspended sediment and typhoon tracks). Analysis suggested that coastal SST is strongly influenced by the outer ocean SST, indicating a regional control. However, the local winds, with associated summer rainfall and copious sediment-laden run-off, had a significant secondary impact. Typhoons are also an important factor leading to ocean colour variation. Along the western coastal zone of Okinawa, the winter East Asian Monsoon causes significant upwelling and seafloor sediment removal, while terrestrial impact is a significant secondary control in summer on ocean colour variability via sediment-laden river run-off. Previously noted changes in the magnitude of extreme rainfall events in the area suggest that sediment delivery to the coastal zones of islands in the region has been increasing in recent decades, providing a combined climate and terrestrial impact on the coastal environment. Although typhoons and heavy rainfall are episodic events, appropriate land management on the many hilly and mountainous islands of the sub-tropical northwestern Pacific is needed if such events are not to lead to deterioration, and decrease of resilience, of coastal ecosystems.

New chronological constraints for Cryogenian to Cambrian rocks in the Three Gorges, Weng'an and Chengjiang areas, South China

The Neoproterozoic and Cambrian were two of the most dramatic periods in the history of the Earth, because large multi-cellular animals first appeared then in the so-called “Cambrian Explosion”. To better understand this event, many paleontological and geochemical studies now focus on rocks in South China, because of the fossiliferous succession and good exposure. Since the recognition of the Yangtze Gorges and Chengjiang area as type localities of the Sinian (Ediacaran) and Meishucunian (Early Cambrian) Systems, both sections have been intensively investigated. In order to decipher the relationships between the evolution of life and surface environmental changes, it is necessary to understand their paleontological, geochemical and geo-chronological constraints.This study presents new chronological constraints for the Cryogenian to Cambrian rocks in the Three Gorges, Weng'an and Chengjiang areas, South China. We discovered two tuff layers, one at the base of the Shuijingtuo Fm at Three Gorges and the other at the bottom of the Dahai Member in Chengjiang. In addition, we collected sandstones from Neoproterozoic strata in the Three Gorges, Chengjiang and Weng'an areas for provenance analysis. Zircons, separated from the tuff layers, provide new Nano-SIMS U–Pb ages of 526.4±5.4Ma at the base of the Shuijingtuo Fm, and 523.9±6.7Ma at the bottom of the Dahai Member. The tuffaceous beds occur at an unconformity, and nodules are common in the Three Gorges, Meishucun and Taoying sections, indicating that major and relatively wide-scale volcanic and sedimentological events occurred at ca. 525Ma. Moreover, carbonate carbon isotope chemostratigraphies at Morocco, Siberia, Three Gorges and Meishucun display different characteristics during the Tommotian. One possibility is that the South China Ocean was separated from an outer ocean at that time. Detrital zircons in sandstones have age populations at ca. 2.7, 1.8, 1.6, 1.0 and from 0.9 to 0.75Ga. indicating that the paleo-hinterland of the Nanhua and Kangdian rift basins was geologically complex. Despite the lack of ca. 1.6Ga rocks in the Yangtze and Cathaysia Blocks, these data are nevertheless interpreted to indicate derivation of the zircons from basement rocks in the Yangtze craton.

Seasonality of intermediate waters hydrography west of the Iberian Peninsula from an 8 yr semiannual time series of an oceanographic section

Abstract. Seasonality of hydrographical properties at depth in the western Iberian margin (eastern North Atlantic) is analysed from a 2003–2010 time series of a semiannual oceanographic section extending ∼200 nm off Cape Finisterre (43° N). All water masses down to the permanent thermocline (2000 dbar) show a consistent seasonal signature in their thermohaline properties and there is a notable asymmetry between the slope region and the outer ocean (in the surroundings of the Galicia Bank). There is overall cooling and freshening of eastern North Atlantic central waters in summertime, which is larger and deeper-reaching on the slope. In summertime, Mediterranean Water (MW) gets tightly attached against the slope and is uplifted, reinforcing its thermohaline signature and diminishing its presence at the outer ocean. In wintertime the situation reverses, MW seems to detach from the slope and spreads out to the open ocean, even being observed a secondary branch around the Galicia Bank. Thermohaline seasonality at depth shows values up to 0.4 °C and 0.08 in salinity at the lower MW, of the order of 20% of the overall interannual variability observed during the whole period. Decomposition of thermohaline changes at isobaric levels to changes along isoneutral surfaces and changes due to vertical displacements help analyse the physical processes behind the observed seasonality in terms of (1) the large-scale seasonality of the subtropical gyre in response to the seasonal migration of the subtropical high pressure system and subsequent anomalies in Ekman transport and wind stress curl, (2) the continental slope dynamics, characterized by summer upwelling, winter development of the Iberian Poleward Current and Mediterranean water spreading, and (3) the possible influence of seasonal changes of water mass properties at their formation sources.

Production and bacterial decomposition of dissolved organic matter in a fringing coral reef

The concentrations of dissolved organic carbon and nitrogen (DOC and DON, respectively) were measured in Shiraho fringing reef (Japan), using a high-temperature catalytic-oxidation method. When the seawater on the reef flat (shallow lagoon) was isolated from the surrounding ocean due to the low tide, the concentrations of DOC and DON on the reef flat were 66–75 and 4.8–5.7 μmol l−1, respectively. The DOC and DON concentrations were higher than those of the adjacent outer ocean (57–58 and 3.8 μmol l−1, respectively), suggesting that the coral reef functioned as a net source of dissolved organic matter for the surrounding ocean. In order to investigate long-term bacterial decomposition of the reef-derived DOC (RF-DOC), the seawater samples collected on the reef flat and at the adjacent ocean were incubated in the dark for 1 year. Regression analysis using an exponential curve that considered two degradability pools (labile and refractory) fitted the mineralization of the RF-DOC very well (r 2 > 0.89). According to the regression analysis, the DOC produced on the reef flat was composed of the labile fraction of 63–94% (average 77%) and the refractory fraction of 6–37% (average 23%). It was concluded that some of the DOC that was produced in the coral reef ecosystem was exported to the surrounding ocean if the reef flat had a water residence time less than several months. The exported organic matter may support microbial communities in the ocean as an energy source.

Water Mass Analysis of Coastal Sea Waters in and around Osaka Bay using Stable Isotope Ratio

In Osaka Bay, water pollution phenomena such as red tide and blue tide still occur frequently, in spite of the efforts to improve water qualities for years. To make a decision about effective environmental measures in the bay, it is necessary to clarify the budget and cycle of nutrients in the waters. In this study, focusing on the water mass intruding from the outer ocean, a cluster analysis using salinity, nutrient concentrations, and stable isotope ratio δ18O and δD is conducted. The cluster analysis divides the coastal sea waters in and around Osaka Bay into six groups, including the clusters related to Kuroshio surface water and sub-surface ocean water, and the results show that the sub-surface ocean water had intruded into the Kii Channel due to off-shore migration of the Kuroshio Current in spring 2009.

Processes that influence the mixed layer deepening during winter in the North Pacific

The contribution of various forcing sources to the mixed layer depth (MLD) growth during winter in the North Pacific was investigated by analyzing the Simple Ocean Data Assimilation and NCEP/NCAR reanalysis data during 1959–2004. It was found that the MLD growth can be mainly estimated from the heat budget analysis in the mixed layer, in which both the surface heat flux and the ocean heat transport are included. The remaining difference is explained in terms of the effects of entrainment by wind stress and the error in determining MLD due to a diffused thermocline. The contribution to the heat budget from the ocean heat transport is positive in the Kuroshio region owing to geostrophic advection and eddy diffusion, but in the outer ocean it is negative north of 27°N and positive south of it, influenced by Ekman advection. It was also found that the transition to the stronger ocean heat transport and smaller MLD growth in the Kuroshio Extension region occurs in 1985.

IMPACT ANALYSIS OF RAINFALL ON WATER QUALITY AND PRIMARY PRODUCTION IN THE OSAKA BAY

Water quality and primary production in an enclosed bay are dependent on inflow loads from rivers and outer ocean, and nutrients released from sea bottom. A nutrient load by rainfall also has an important role in the primary production. We here focused on the influence of the precipitation on the water quality and primary production in the Osaka Bay, and then conducted water quality analyses of rainwater and river water.The rainwater had high concentration of dissolved inorganic nitrogen, and the ratio of rainfall load to Yodo River load was about 20% on average for observation period. This result suggests that the precipitation make phytoplankton biomass increase in the surface layer with nitrogen limitation. Furthermore we examined the changes of water quality and primary production using a system dynamics model to make a quantitatively evaluation of precipitation effect.

Distribution and partitioning of nitrogen and phosphorus in a fringing reef lagoon of Ishigaki Island, northwestern Pacific

Concentration of dissolved and particulate carbon (C), nitrogen (N), and phosphorus (P) were measured daily and seasonally in the water column of a coral reef lagoon at Ishigaki Island. Concentrations of dissolved inorganic N and P (DIN, DIP), dissolved organic C and N (DOC, DON), particulate organic C, and particulate N and P (POC, PN, PP) were usually higher in the lagoon than at offshore stations, while dissolved organic P (DOP) was higher at the offshore stations than in the lagoon. Concentration ratios of DIN:DIP and PN:PP were near 16:1 in winter and >20:1 in summer. DON:DOP was always ≥30. Total P (DIP + DOP + PP) was fairly constant around 0.177 ± 0.025 μmol l–1 (mean ± SD), suggesting conservative behavior of water-column P around this reef. DIP and PP seemed to be produced at the expense of DOP, and PP rather than DIP increased when gross primary production (GPP) was high. In contrast, total N (DIN + DON + PN) showed large spatial and seasonal variation from 4.3 to 12.4 μmol l–1. DON and PN increased when GPP and DIN:DIP were high, which suggests that export production of organic N by the lagoon biota was enhanced by primary production and the availability of N relative to P. Estimation of C, N, and P exchange fluxes between the lagoon and the outer ocean using a simple hydrodynamic model showed that the lagoon ecosystem released N (especially DIN) but not P to the surrounding ocean. Oceanic DOP could be the major source for the P budget of the lagoon. While the lagoon was a net source of organic C to the outer ocean, the net export was only a minor fraction (<5%) of gross exchange of organic C between these 2 ecosystems.

The Only Mappamundi in a Bestiary Context: Cambridge, MS Fitzwilliam 254

The mappamundi in MS Fitzwilliam 254 folio 1v, which dates from approximately 1220–1230, is the only one to appear in a medieval Latin bestiary. It does not fit well in any of the established classifications of mappaemundi. This paper will account for the map's unusual features and also for its presence in a Third Family bestiary. The prominence of the islands in the map's Outer Ocean suggests that the mapmaker wanted to represent the most distant parts of the world as objects of the Christian mission to bring the Gospel ‘to the ends of the earth’. Accounting for the presence of a mappamundi in Fitzwilliam 254 requires an examination of the composition of Third Family bestiaries. Chet Van Duzer is a writer on historical geography living in California; Ilya Dines is finishing his doctorate at the Hebrew University of Jerusalem.

Self‐adapting open boundaries for a sigma coordinate model of the eastern North Atlantic

A regional non‐eddy‐resolving configuration of the SPEM5.1 primitive equation model is used to study the dynamics of the eastern North Atlantic. Along most of the domain perimeter, extensive open boundaries (OBs) evacuate outgoing perturbations, while the outer ocean is simulated by lateral relaxation of some of the model variables. Unlike in existing regional models, this lateral constraint only concerns the tracers and the baroclinic velocities, for which good climatological estimates exist. Along the OBs, the barotropic stream function is entirely determined by the model response to the inner dynamics, without relaxation to any questionable a priori estimate. The adjustment processes and their interaction with the open boundaries are described. The final solution is remarkably stable and quite realistic. The net transports crossing the boundaries are prescribed; we therefore investigated the impact of these parameters. We first show that the prescribed mass exchange between the basin and the rest of the Atlantic has almost no influence on the interior circulation since the western and southern lateral conditions naturally adjust to the interior dynamics. The net circulation constrained around Iceland, however, has large‐scale consequences: Through the intensity of the overflow above the Iceland‐Scotland Ridge (ISR), this parameter affects the stratification north and south of the Rockall Plateau, the subpolar dynamics, and finally the North Atlantic Current path up to the Charlie Gibbs Fracture Zone. This slowly propagating dynamical effect, already noticed in previous studies, is shown to be forced baroclinically near the ISR.

Numerical Simulation of Currents and Density in a Bay Considering Variable Conditions of Outer Ocean

When the phenomena in a bay are calculated, the open boundary is often located around the mouth of the bay. On the other hand, the effect of physical conditions of outer ocean is essential for such phenomena as thermohaline front or intrusion of warm water mass into the bay. However, it is difficult to elucidate the mechanism of such phenomena if the constant conditions are applied for the open boundary. In the present study, the influences of outer ocean state on the phenomena in the bay were investigated by numerical simulations. At first, the effects of fresh water discharge, surface cooling and outer ocean condition on the structure of thermohaline front was examined for an idealized model basin. Next, the numerical simulations were carried out for Tokyo Bay and the influence of water temperature distribution of Sagami bay was discussed. In the calculation considering the effects of outer bay region, the satellite remote sensing data was used for determining the sea surface temperature.