Semi-enclosed Sea Research Articles

Energetics of Semienclosed Basins with Two-Layer Flows at the Strait

Abstract Examination of the energy budget for semienclosed seas with two-layer exchange flow at the strait shows that the energy flux at the open portion of the boundary (the strait) is proportional to the surface buoyancy flux integrated over the basin area, with the constant of proportionality given by the interface depth. When the surface buoyancy flux is positive, the energy flux is negative: these types of basins have an estuarine circulation. Antiestuarine basins have a negative surface buoyancy flux, which provides a positive energy flux, augmenting the wind work in powering the circulation. The energy budget for the semienclosed seas with vertically separated flows at the strait is examined using reanalysis products for four major semienclosed basins: the Mediterranean and Red Seas (antiestuarine) and the Black and Baltic Seas (estuarine). Important differences in the relative contribution to the energy budget of the wind work versus the surface buoyancy flux are found within basins of the same type, and these differences help explain some qualitative aspects of the basins’ flow.

Concentrations of mercury in tissues of striped dolphins suggest decline of pollution in Mediterranean open waters

The Mediterranean is a semi-enclosed sea subject to high mercury (Hg) pollution from both natural and anthropogenic sources. With the objective of discerning temporal changes in marine Hg pollution in the oceanic waters of the northwestern Mediterranean Sea, we analysed liver and kidney from striped dolphins (Stenella coeruleoalba) collected during 2007–2009 and compared them with previous results from a similar sample from 1990–1993. The effect of body length and sex on tissue Hg concentrations was investigated to ensure an unbiased comparison between the periods. The Hg concentrations did not show significant sex-related differences in any tissue or period but were correlated positively with body length. Using body length as a covariate, Hg concentrations in liver and kidney were higher in 1990–1993 than in 2007–2009. This result suggests that measures to reduce emissions in Western European countries have been effective in reducing mercury pollution in Mediterranean open waters.

Global Priorities for Marine Biodiversity Conservation

In recent decades, many marine populations have experienced major declines in abundance, but we still know little about where management interventions may help protect the highest levels of marine biodiversity. We used modeled spatial distribution data for nearly 12,500 species to quantify global patterns of species richness and two measures of endemism. By combining these data with spatial information on cumulative human impacts, we identified priority areas where marine biodiversity is most and least impacted by human activities, both within Exclusive Economic Zones (EEZs) and Areas Beyond National Jurisdiction (ABNJ). Our analyses highlighted places that are both accepted priorities for marine conservation like the Coral Triangle, as well as less well-known locations in the southwest Indian Ocean, western Pacific Ocean, Arctic and Antarctic Oceans, and within semi-enclosed seas like the Mediterranean and Baltic Seas. Within highly impacted priority areas, climate and fishing were the biggest stressors. Although new priorities may arise as we continue to improve marine species range datasets, results from this work are an essential first step in guiding limited resources to regions where investment could best sustain marine biodiversity.

Long-term vertical land motion from double-differenced tide gauge and satellite altimetry data

We present a new approach to estimate precise long-term vertical land motion (VLM) based on double-differences of long tide gauge (TG) and short altimetry data. We identify and difference rates of pairs of highly correlated sea level records providing relative VLM estimates that are less dependent on record length and benefit from reduced uncertainty and mitigated biases (e.g. altimeter drift). This approach also overcomes the key limitation of previous techniques in that it is not geographically limited to semi-enclosed seas and can thus be applied to estimate VLM at TGs along any coast, provided data of sufficient quality are available. Using this approach, we have estimated VLM at a global set of 86 TGs with a median precision of 0.7 mm/year in a conventional reference frame. These estimates were compared to previous VLM estimates at TGs in the Baltic Sea and to estimates from co-located Global Positioning System (GPS) stations and Glacial Isostatic Adjustment (GIA) predictions. Differences with respect to the GPS and VLM estimates from previous studies resulted in a scatter of around 0.6 mm/year. Differences with respect to GIA predictions had a larger scatter in excess of 1 mm/year. Until satellite altimetry records reach enough length to estimate precise VLM at each TG, this new approach constitutes a substantial advance in the geodetic monitoring of TGs with major applications in long-term sea level change and climate change studies.

Developing twenty-first century skills: insights from an intensive interdisciplinary workshop Mosaic of Life

The Baltic Sea, one of the world’s largest semi-enclosed seas, which, with its very low salinity and quasi-isolation from the big oceans cannot decide whether it is a sea or a large lake. This geologically-unique environment supports an even more surprising and delicate marine ecosystem, where a complex community of fishes, marine mammals and important microscopic organisms creates a magical mosaic of life. Humans have enjoyed the abundance of life in the Baltic Sea for thousands of years, and major Scandinavian and Baltic cities have oriented themselves towards this geo-ecosystem in order to develop and seek ecological, economical and cultural inspiration and wealth. The ‘Mosaic of Life’ workshop aimed at going beyond the obvious in examining the meaning of the Baltic Sea by gathering together a selection of young, creative minds from different backgrounds ranging from the arts and economics to geology and life sciences. This intensive workshop was designed as a unique training opportunity to develop essential twenty-first century skills – to introduce and develop creative, critical and interdisciplinary thinking and collaborative teamwork, as well as to foster a visual and scientific literacy, using project-based learning and hands-on activities. Our final goal has been to be inspired by the resulting connections, differences and unifying concepts, creating innovative, interdisciplinary projects which would look further than the sea – further than the eye can see and further into the future.

Spatial variations of sea-level rise and impacts: An application of DIVA

Due to complexities of creating sea-level rise scenarios, impacts of climate-induced sea-level rise are often produced from a limited number of models assuming a global uniform rise in sea level. A greater number of models, including those with a pattern reflecting regional variations would help to assure reliability and a range of projections, indicating where models agree and disagree. This paper determines how nine new patterned-scaled sea-level rise scenarios (plus the uniform and patterned ensemble mean rises) influence global and regional coastal impacts (wetland loss, dry land loss due to erosion and the expected number of people flooded per year by extreme sea levels). The DIVA coastal impacts model was used under an A1B scenario, and assumed defences were not upgraded as conditions evolved. For seven out of nine climate models, impacts occurred at a proportional rate to global sea-level rise. For the remaining two models, higher than average rise in sea level was projected in northern latitudes or around populated coasts thus skewing global impact projections compared with the ensemble global mean. Regional variability in impacts were compared using the ensemble mean uniform and patterned scenarios: The largest relative difference in impacts occurred around the Mediterranean coast, and the largest absolute differences around low-lying populated coasts, such as south, south-east and east Asia. Uniform projections of sea-level rise impacts remain a useful method to determine global impacts, but improved regional scale models of sea-level rise, particularly around semi-enclosed seas and densely populated low-lying coasts will provide improved regional impact projections and a characterisation of their uncertainties.

The Mediterranean Sea system: a review and an introduction to the special issue

Abstract. The Mediterranean Sea is a semi-enclosed sea characterized by high salinities, temperatures and densities. The net evaporation exceeds the precipitation, driving an anti-estuarine circulation through the Strait of Gibraltar, contributing to very low nutrient concentrations. The Mediterranean Sea has an active overturning circulation, one shallow cell that communicates directly with the Atlantic Ocean, and two deep overturning cells, one in each of the two main basins. It is surrounded by populated areas and is thus sensitive to anthropogenic forcing. Several dramatic changes in the oceanographic and biogeochemical conditions have been observed during the past several decades, emphasizing the need to better monitor and understand the changing conditions and their drivers. During 2011 three oceanographic cruises were conducted in a coordinated fashion in order to produce baseline data of important physical and biogeochemical parameters that can be compared to historic data and be used as reference for future observational campaigns. In this article we provide information on the Mediterranean Sea oceanographic situation, and present a short review that will serve as background information for the special issue in Ocean Science on "Physical, chemical and biological oceanography of the Mediterranean Sea". An important contribution of this article is the set of figures showing the large-scale distributions of physical and chemical properties along the full length of the Mediterranean Sea.

The South China Sea Maritime Dispute: Legality, Power, and Conflict Prevention

Tensions in the South China Sea have risen in recent years for reasons related to conflicting territorial claims and rivalry, competition for access to fish stocks as well as oil and gas fields, and in China`s case, emerging strategic interests. Because international law largely excludes it from an area it regards as historically Chinese, China has recently become more assertive in pushing its claim, resorting to power projection, particularly against smaller claimants, such as Vietnam and the Philippines. China`s actions have drawn in external powers, including the United States, Japan, and India, a development that exacerbates the problem. The danger is not that the United States and China may come into a direct conflict, but that through error or miscalculation a clash may escalate into a conflict involving external powers. Proposals to prevent conflict and stabilize the area include an agreement to avoid incidents at sea. Also a UN-sponsored conference on the South China Sea could contribute to a long-term resolution of the issue by dealing with competing claims in a semi-enclosed sea and other outstanding issues.

The UNCLOS and the US-China Hegemonic Competition over the South China Sea

The South China Sea is a semi-enclosed sea with a complex set of territorial claims by a number of Southeast Asian nations and China being the dominant claimant country. The United States is not a party to such claims. However, the US has great concerns pertaining to peace and stability of the region as far as freedom of navigation in the SCS is concerned, which has significant repercussions for its strategic interests. In addition to the utilization of the SCS as an important international trade route, the US is also committed to protect the interests of its allies in the region, as well as those of its companies involved in offshore hydrocarbon activities. In the aftermath of the September 11 terrorist attack, the dynamics of a new world order push the US to strengthen its presence in the region in order to combat any security threats against its interests. This article investigates China-US relations in the SCS and highlights the law of the sea prescriptions that facilitate the understanding of the legal nature of the tensions between China and the US.

Holocene evolution of depositional processes off southwest Japan: Response to the Tsushima Warm Current and sea-level rise

An understanding of the characteristics and evolution of shelf sediments is crucial for reconstructing ancient shelves from stratigraphic records. Oceanic currents have a major influence on shelf sediments. However, the evolution of sediments in narrow strait/seaway settings influenced by oceanic currents, especially in response to sea-level change, is still unclear compared with open shelf settings. The Tsushima Strait is the only gateway for the Tsushima Warm Current (TWC) into the semi-enclosed Sea of Japan. The evolution of depositional processes in the strait during the Holocene is not well documented, and this makes it difficult to develop a depositional model for this strait environment. To remedy this, we investigated marine sediments off Fukuoka, southwest Japan, adjacent to the eastern channel of the Tsushima Strait. A vibrocorer allowed us to collect 1.5–4.9m long cores from 11 sites on the coarse-grained sandy shelf (38–66m water depth). As a result, 10 lithofacies are recognized, and radiocarbon dating results indicate that these deposits formed mainly at two times, from 11.6 to 8.4calkyrBP and since 6.6calkyrBP. The main temporal changes recorded in the depositional environment off Fukuoka include (1) coastal and shallow-marine environments before the Last Glacial Maximum, (2) an embayment during the period 11.6–8.4calkyrBP, (3) a period of non-deposition from 8.4 to 6.6calkyrBP (apart from a few tidal channel deposits), and (4) TWC-influenced shelf deposition after 6.6calkyrBP. The formation of the TWC-influenced deposits shifted towards shallower water regions during postglacial sea-level rise. Overall, the evolution of the TWC-influenced deposits suggests that the strait/seaway environment was controlled mainly by water depth, but also by sediment supply from the proximal region in the strait.

Cooperation in the South China Sea: From Dispute Management to Ocean Governance

The South China Sea has long been of interest to scholars of international law and international relations. But attention has been paid almost exclusively to the simmering territorial disputes in the South China Sea. While this is justified by the concern that such disputes pose a threat to regional peace and stability, that the management of the territorial disputes in the South China Sea dominates existing literature may belie the fact that the South China Sea is a large semi-enclosed sea and boasts crucial sea lines of communication. This paper canvasses for a more comprehensive approach to cooperation in the South China Sea through the prism of ocean governance. In this vein, the management of territorial disputes is but an important element of cooperation in the South China Sea.

Abnormal storm waves in the East Sea (Japan Sea) in April 2012

ABSTRACT Lee, H.S., 2013. Abnormal storm waves in the East Sea (Japan Sea) in April 2012 The winter East Sea, a semi-enclosed sea surrounded by Korea in the west, Japan in the east and south and Russia in the north, normally experiences rough sea conditions due to East Asian monsoon and winter storms. In April 2012, record-breaking abnormally high waves, significant wave heights of 11.21 m and 12.39 m and significant wave periods of 13.6 sec and 14.3 sec at Akita and Yamagata GPS buoy sites, respectively, were observed along the Tohoku coast in the East Sea side of Japan. It was due to a well- and fast-developed low pressure passing through the East Sea. This paper describes how a low pressure could be grown so rapidly to tropical cyclone level in this time and numerical hindcast results for future forecast and engineering purpose. With respect to the meteorological condition, it is found that strong convective motion due to latent heat and water vapor from Tsushima Warm Current together with an accompani...

Coupling of Shoreline Erosion and Biodiversity Loss: Examples from the Black Sea

The shoreline zone is an area where the sea and land contact and plays a very important role in integrating a sea and its watershed in a whole system. Among the main environmental problems of the coastal zones, two critical ones are - coastal erosion and a biodiversity loss. Problems are most pronounced in semi-enclosed seas as the Black sea. Using results of the long-term studies in different parts of the Black Sea shoreline this paper attempts to make some steps to deepen our understanding of interactions between biodiversity loss and shoreline erosion. An analysis of the results from several case studies was done. Some mechanisms of interrelations between coastal erosion and biodiversity changes are also discussed. The increased concentration of mineral particles, especially hydrophilic ones, as a result of coastal erosion, is a threat not only to benthic organisms, but also to planktonic microalgae and copepods. This negative impact sharply decreases total productivity of coastal waters. De-vegetation of the beaches and cliffs increases movement of sand and soil particles from beaches and cliffs due to high acceleration of wind and water erosion. This also leads to an increased turbidity of marine waters and an associated decrease in their productivity. Other results suggest there is a decrease in mollusk shell production leading to acceleration of a beach degradation which may also increase cliff abrasion. Coastal de-vegetation, marine community degradation and coastline erosion interrelate through a network of chains of cause-and-effect that forms the positive feed-forward and feed-back loops. This creates a self-acceleration mechanism of a development of coastal erosion and biodiversity loss.

Fisheries in the South China Sea: A Centrifugal or Centripetal Force?

The present paper intends to have a look at fisheries in the South China Sea in order to find out whether this particular issue is a problem solver or rather a problem creator in this region characterized by tense inter-State relationships at present. In this part of the world's ocean, dominated by maritime features such as the Paracels and the Spratleys, i.e. shallow areas, sometimes drying only at low tide, and sometimes at high tide as well, fish is a plentiful resource relied upon by many fishermen of the surrounding countries as a source of income. If we take Europe as an example, fisheries seem to have the dual capability to either trigger disputes between States, resulting sometimes in outright fish wars, or to provide a means of furthering integration between States, such as has been accomplished by the European Common Fisheries Policy. In the South China Sea a similar duality can be witnessed. At times, fishermen have dramatically influenced the relations between certain States to the point of suddenly straining diplomatic relations totally disproportionately to the event which had triggered a particular incident. But fisheries are also used as a vehicle for trying to further co-operation on both bilateral and regional levels. Indeed, very often fisheries are seen as a more “neutral” area able to stimulate co-operation more easily than, for instance, co-operation in the military field or on sovereignty-related issues. This paper will conclude by determining whether Article 123 of the 1982 United Nations Convention on the Law of the Sea adds any legal obligation to the riparian States of a semi-enclosed sea in this respect.

ECOSUPPORT: A Pilot Study on Decision Support for Baltic Sea Environmental Management

The Baltic Sea is a semi-enclosed sea with limited water exchange with the world ocean and with a freshwater surplus resulting in a brackish water body with strong vertical and horizontal stratifications (e.g., Lepparanta and Myrberg 2009). The discharge of large rivers causes a wide range of sea surface salinities between 2 g kg in the north (Bothnian Bay) or east (Gulf of Finland) and 20 g kg in the south (Kattegat) (Fig. 1). Also, the vertical gradients of salinity are large. For instance, the vertical salinity gradient in the eastern Gotland Basin amounts to about 4 g kg. This specific hydrography prevents a sufficient ventilation of the deep water with the consequence of oxygen depletion. In addition to this natural factor, the anthropogenic impact of 85 million people, living in the catchment area of the Baltic Sea, is significant. Inter alia, intensive agriculture and inadequately treated sewage water result in eutrophication, reinforcing oxygen depletion. The latter effect is today so pronounced that large areas of the sea bottom are covered by hypoxia or even anoxia, i.e. by bottom water with a dissolved oxygen concentration below *2 ml O2 l , or completely depleted, respectively (Hansson et al. 2011). To counteract the consequences of eutrophication, the Baltic Sea Action Plan (BSAP) by the Helsinki Commission (HELCOM) was designed to improve the environmental conditions of the Baltic Sea (Backer et al. 2010). Nutrient load reductions at country level were calculated to fulfil scientifically based environmental targets (Wulff et al. 2007). However, the original figures of the BSAP were estimated without taking climate change into account. To overcome this shortcoming, the ECOSUPPORT project (Advanced modelling tool for scenarios of the Baltic ECOsystem to SUPPORT decision making) was initiated to investigate the combined impacts of changing climate and changing human activity (anthropogenic nutrient load changes, coastal management, fisheries) on the marine ecosystem.

Od mora koja razdvajaju do arena za suradnju: primjena režima zatvorenog i poluzatvorenog mora na Jadran

The law of the sea provides the international legal basis for the coastal states of the Adriatic Sea to claim zones of maritime jurisdiction off their shores and divide the Adriatic Sea between them. The same international law of the sea obligates the Adriatic littoral states to cooperate in a variety of ways, notably by establishing a special regime applicable to enclosed and semi-enclosed seas such as the Adriatic. This paper explores the maritime jurisdictional claims allowed under international law and claimed in the Adriatic in particular. The implementation of the regime of enclosed and semi-enclosed seas in the Adriatic context is then explored.

Three-dimensional distribution of larval fish assemblages in an anticyclonic eddy in a semi-enclosed sea (Gulf of California)

Transects of CTD (to 1000 m) and zooplankton stations (to 200 m in 50 m strata) were made across an anticyclonic eddy in the southern Gulf of California during October 2007 to determine its influence upon the three-dimensional distribution of larval fish assemblages. The eddy was 90 km in diameter and 70 m deep. A larval fish assemblage, representing a mix of oceanic and coastal species, was defined mainly in the eddy from 200 m depth to the surface. Mesopelagic species, such as Vinciguerria lucetia, were dominant. Coastal reef (Diplectrum sp.) and pelagic (Auxis spp.) species were found mainly in the surface layer. This suggests that, because of the Gulf ’s relative narrowness, the eddy trapped coastal fish larvae during its formation and trajectory southward, retaining larvae of different adult habits. Another larval fish assemblage was defined off the eastern coast; its high larval abundance and specific richness was probably associated with coastal upwelling. Mesopelagic species (e.g. Triphoturus mexicanus) dominated this assemblage, and coastal demersal species that were absent from the eddy (e.g. Symphurus williamsi) were recorded in the surface layer, suggesting that the thermocline was a vertical boundary in this assemblage. The 3D differentiation of planktonic habitats was the result of the mesoscale hydrodynamics in the area sampled, in particular that associated to the eddy life history and characteristics (radius, depth and velocity), and to coastal upwelling, promoting larval retention of a mix of species of different adult habits.

Statistical downscaling of the French Mediterranean climate: assessment for present and projection in an anthropogenic scenario

Abstract. The Mediterranean basin is a particularly vulnerable region to climate change, featuring a sharply contrasted climate between the North and South and governed by a semi-enclosed sea with pronounced surrounding topography covering parts of the Europe, Africa and Asia regions. The physiographic specificities contribute to produce mesoscale atmospheric features that can evolve to high-impact weather systems such as heavy precipitation, wind storms, heat waves and droughts. The evolution of these meteorological extremes in the context of global warming is still an open question, partly because of the large uncertainty associated with existing estimates produced by global climate models (GCM) with coarse horizontal resolution (~200 km). Downscaling climatic information at a local scale is, thus, needed to improve the climate extreme prediction and to provide relevant information for vulnerability and adaptation studies. In this study, we investigate wind, temperature and precipitation distributions for past recent climate and future scenarios at eight meteorological stations in the French Mediterranean region using one statistical downscaling model, referred as the "Cumulative Distribution Function transform" (CDF-t) approach. A thorough analysis of the uncertainty associated with statistical downscaling and bi-linear interpolation of large-scale wind speed, temperature and rainfall from reanalyses (ERA-40) and three GCM historical simulations, has been conducted and quantified in terms of Kolmogorov-Smirnov scores. CDF-t produces a more accurate and reliable local wind speed, temperature and rainfall. Generally, wind speed, temperature and rainfall CDF obtained with CDF-t are significantly similar with the observed CDF, even though CDF-t performance may vary from one station to another due to the sensitivity of the driving large-scale fields or local impact. CDF-t has then been applied to climate simulations of the 21st century under B1 and A2 scenarios for the three GCMs. As expected, the most striking trend is obtained for temperature (median and extremes), whereas for wind speed and rainfall, the evolution of the distributions is weaker. Mean surface wind speed and wind extremes seem to decrease in most locations, whereas the mean rainfall value decreases while the extremes seem to slightly increase. This is consistent with previous studies, but if this trend is clear with wind speed and rainfall data interpolated from GCM simulations at station locations, conversely CDF-t produces a more uncertain trend.

The Legality of Foreign Military Activities in the Exclusive Economic Zone under UNCLOS

During negotiations for the United Nations Convention on the Law of the Sea (UNCLOS), military activities in another state's Exclusive Economic Zone (EEZ) were a point of contention. Currently, the issue remains controversial in state practice. UNCLOS attempts to balance the differing interests of coastal and maritime states, but is silent or ambiguous on the legality of military operations in foreign EEZs. Coastal states seek to assert increasing control over their maritime zones while maritime states prioritize the freedom of navigation. This article examines the competing views on these issues in the context of the 2009 Impeccable incident between China and the United States that occurred in the South China Sea. The issue of military activities in the EEZ will continue to be a complex subject, without clear definitions in the nature and scope of permissible activity. As state practice evolves, the potential for hostilities is high, particularly in semi-enclosed sea areas such as the South China Sea. This article concludes that states should create dialogues and form agreements to help clarify the contours of military activity in the EEZ, focusing on mutual interests, interdependence, and coexistence rather than perceiving the ocean as a zero-sum resource.

Acidification in Arabian Gulf – Insights from pH and temperature measurements

The detrimental effects of increasing atmospheric levels of carbon dioxide (CO(2)) and other greenhouse gases since the industrial revolution has led to a concerted international effort to control their release and abate the environmental and human health impacts. CO(2) is removed from the atmosphere by photosynthesis of plants in the terrestrial environment and by aquatic sequestration. In the Middle East and other arid countries, terrestrial removal is minimal. The most likely removal pathway for CO(2) in arid regions around the world is by aquatic sequestration. In the Middle East the major sink is the Arabian Gulf which leads to acidification of the marine environment. Biweekly pH concentration measurements in surface waters of the northern Arabian Gulf over a four year period in this study suggest that the Arabian Gulf waters are becoming increasingly acidic with time. Supporting evidence for increased CO(2) sequestration comes from increased marine primary productivity over the past decade. Biological effects, such as coral bleaching, observed during this period suggest that urgent action is required to reverse the trend and protect marine life. The data highlight the fact that this semi-enclosed sea is undergoing a rapid degradation which may affect the oceanic chemistry and biogeochemical cycle much earlier than predicted for most oceanic waters.