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Sample records for alboran sea western

  1. New and rare sponges from the deep shelf of the Alboran Island (Alboran Sea, Western Mediterranean).

    PubMed

    Sitjà, Cèlia; Maldonado, Manuel

    2014-01-01

    The sponge fauna from the deep shelf (70 to 200 m) of the Alboran Island (Alboran Sea, Western Mediterranean) was investigated using a combination of ROV surveys and collecting devices in the frame of the EC LIFE+ INDEMARES Grant aimed to designate marine areas of the Nature 2000 Network within Spanish territorial waters. From ROV surveys and 351 examined specimens, a total of 87 sponge species were identified, most belonging in the Class Demospongiae, and one belonging in the Class Hexactinellida. Twenty six (29%) species can be regarded as either taxonomically or faunistically relevant. Three of them were new to science (Axinella alborana nov. sp.; Axinella spatula nov. sp.; Endectyon filiformis nov. sp.) and 4 others were Atlantic species recorded for the first time in the Mediterranean Sea (Jaspis eudermis Lévi & Vacelet, 1958; Hemiasterella elongata Topsent, 1928; Axinella vellerea Topsent, 1904; Gelliodes fayalensis Topsent, 1892). Another outstanding finding was a complete specimen of Rhabdobaris implicata Pulitzer-Finali, 1983, a species only known from its holotype, which had entirely been dissolved for its description. Our second record of the species has allowed a neotype designation and a restitution of the recently abolished genus Rhabdobaris Pulitzer-Finally, 1983, also forcing a slight modification of the diagnosis of the family Bubaridae. Additionally, 12 species were recorded for the first time from the shelf of the Alboran Island, including a few individuals of the large hexactinellid Asconema setubalense Kent, 1877 that provided the second Mediterranean record of this "North Atlantic" hexactinellid. ROV explorations also revealed that sponges are an important component of the deep-shelf benthos, particularly on rocky bottoms, where they make peculiar sponge gardens characterized by a wide diversity of small, erect species forming a dense "undergrowth" among a scatter of large sponges and gorgonians. The great abundance and the taxonomic

  2. Atmospheric patterns driving Holocene productivity in the Alboran Sea (Western Mediterranean): a multiproxy approach.

    NASA Astrophysics Data System (ADS)

    Ausin, Blanca; Flores, Jose-Abel; Sierro, Francisco Javier; Cacho, Isabel; Hernández-Almeida, Iván; Martrat, Belén; Grimalt, Joan

    2014-05-01

    This study is aimed to reconstruct productivity during the Holocene in the Western Mediterranean as well as to investigate what processes account for its short-term variability. Fossil coccolithophore assemblages have been studied along with Mg/Ca and Uk'37-estimated Sea Surface Temperature (SST) and other paleoenvironmental proxies. The study site is located in a semi-permanent area of upwelling in the Alboran Sea. This productive cell is of special interest since is closely related to local hydrological dynamics driven by the entering Atlantic Jet (AJ). The onset of this productive cell is suggested at 7.7 ka cal. B.P. and linked to the establishment of the anticyclonic gyres. From 7.7 ka cal. BP to present, the N ratio and accumulation rate of Florisphaera profunda show successive upwelling and stratification events. This alternation is simultaneous to changes in the Western Mediterranean Deep Water (WMDW) formation rate in the Gulf of Lions [Frigola et al., 2007], along with changes in Mg/Ca-estimated SST, relative abundance of reworked nannoliths, pollen grains record [Fletcher et al., 2012] and n-hexacosan-1-ol index. Two scenarios are proposed to explain short-term climatic and oceanographic variability: [1] Wetter climate and weaker north-westerlies blowing over the Gulf of Lions trigger a slackening of the WMDW formation. Consequently, a minor AJ inflows the Alboran Sea leading to less vertical mixing and a deepening of the nutricline and hence, long-term stratification events. [2] Arid climate and stronger north-westerlies enable WMDW reinforcement. In turn, increased AJ triggers vertical mixing and nutricline shoaling, and therefore, productive periods. Finally, changes in atmospheric patterns (e.g. the winter North Atlantic Oscillation; [Olsen et al., 2012]) prove to be useful in explaining the WMDW formation in the Gulf of Lions and associated short-term productivity variations in the Alboran Sea. References Fletcher, W. J., M. Debret, and M. F

  3. Origin of lipid biomarkers in mud volcanoes from the Alboran Sea, western Mediterranean

    NASA Astrophysics Data System (ADS)

    López-Rodríguez, C.; Stadnitskaia, A.; De Lange, G. J.; Martínez-Ruíz, F.; Comas, M.; Sinninghe Damsté, J. S.

    2013-11-01

    Mud volcanoes (MVs) are the most prominent indicators of active methane/hydrocarbon venting at the seafloor on both passive and active continental margins. Their occurrence in the Western Mediterranean is patent at the West Alboran Basin, where numerous MVs develop overlaying a major sedimentary depocenter containing overpressured shales. Although some of these MVs have been studied, the detailed biogeochemistry of expelled mud so far has not been examined in detail. This work provides the first results on the composition and origin of organic matter, Anaerobic Oxidation of Methane (AOM) processes and general characteristics on MV dynamics using lipid biomarkers as the main tool. Lipid biomarker analysis was performed on MV expelled material (mud breccias) and interbedded hemipelagic sediments from Perejil, Kalinin and Schneider's Heart MVs located in the northwest margin of the Alboran Sea. The n-alkane-distributions and n-alkane-derived indices (CPI and ACL), in combination with the epimerization degree of hopanes (22S/(22S + 22R)) indicate that all studied mud breccia have a similar biomarker composition consisting of mainly thermally immature organic matter with an admixture of petroleum-derived compounds. This concordant composition indicates that common source strata must feed all three studied MVs. The past or present AOM activity was established using lipid biomarkers specific for anaerobic methanotropic archaea (irregular isoprenoids and DGDs) and the depleted carbon isotope composition (δ13C) of crocetane/phytane. The presence of these lipid biomarkers, together with the low amounts of detected GDGTs, is consistent with the dominance of anaerobic methanotrophs of the ANME-2 over ANME-1, at least in mud breccia from Perejil MVs. In contrast, the scarce presence or lack of these AOM-related lipid biomarkers in sediments from Kalinin and Schneider's Heart MVs, suggest no recent active methane seepage has occurred at these sites. Moreover, the observed

  4. Meteorologically-induced mesoscale variability of the North-western Alboran Sea (southern Spain) and related biological patterns

    NASA Astrophysics Data System (ADS)

    Macías, D.; Bruno, M.; Echevarría, F.; Vázquez, A.; García, C. M.

    2008-06-01

    Hydrographic mesoscale structures in the North-western Alboran Sea show a high variability induced by a number of different factors. One of the most important is the differences in atmospheric pressure over the Mediterranean basin when compared to the Gulf of Cádiz. This difference modulates the zonal wind field in the Alboran Sea and the intensity of the Atlantic inflow through the Strait of Gibraltar, also affecting the formation and extension of the Western Alboran Gyre (WAG). When westerly winds are dominant, lower atmospheric pressure in the Mediterranean enhances the inflow of Atlantic waters causing the Atlantic Jet to be located in the vicinity of the Spanish shore, creating a well-defined frontal zone in front of Estepona Cove. In this situation, the coastal upwelling is enhanced, leading to a minimum in sea surface temperature and a maximum of surface nutrient concentrations located in the coastal area. The vertical position of the chlorophyll maximum found in these circumstances appeared to be controlled by the nutrient availability. On the other hand, when easterly winds prevail, higher atmospheric pressure in the Mediterranean leads to a reduced inflow and the oceanographic and biological structures are clearly different. The Atlantic Jet moves southward flowing in a south-eastern direction, changing the structure of the currents, resulting in an enhanced cyclonic circulation extending throughout the North-western Alboran Sea basin. These physical alterations also induce changes in the distribution of biogeochemical variables. Maximum nutrient and chlorophyll concentrations are located further off the coast in the central area of the newly created cyclonic gyre. During these easterlies periods coastal upwelling stops and the distribution of phytoplankton cells seems to be mainly controlled by physical processes such as advection of coastal waters to the open sea.

  5. Origin of lipid biomarkers in mud volcanoes from the Alboran Sea, western Mediterranean

    NASA Astrophysics Data System (ADS)

    López-Rodríguez, C.; Stadnitskaia, A.; De Lange, G. J.; Martínez-Ruíz, F.; Comas, M.

    2014-06-01

    Mud volcanoes (MVs) are the most prominent indicators of active methane/hydrocarbon venting at the seafloor on both passive and active continental margins. Their occurrence in the western Mediterranean is patent at the West Alboran Basin, where numerous MVs develop overlaying a major sedimentary depocentre containing overpressured shales. Although some of these MVs have been studied, the detailed biogeochemistry of expelled mud so far has not been examined in detail. This work provides the first results on the composition and origin of organic matter, anaerobic oxidation of methane (AOM) processes and general characteristics on MV dynamics using lipid biomarkers as the main tool. Lipid biomarker analysis was performed on MV expelled material (mud breccias) and interbedded hemipelagic sediments from Perejil, Kalinin and Schneider's Heart MVs located in the northwest margin of the Alboran Sea. The n alkane distributions and n alkane-derived indices (CPI and ACL), in combination with the epimerization degree of hopanes (22S/(22S+22R)) indicate that all studied mud breccia have a similar biomarker composition consisting of mainly thermally immature organic matter with an admixture of petroleum-derived compounds. This concordant composition indicates that common source strata must feed all three studied MVs. The past or present AOM activity was established using lipid biomarkers specific for anaerobic methanotrophic archaea (irregular isoprenoids and dialkyl glycerol diethers) and the depleted carbon isotope composition (δ13C) of crocetane/phytane. The presence of these lipid biomarkers, together with the low amounts of detected glycerol dialkyl glycerol tetraethers, is consistent with the dominance of anaerobic methanotrophs of the ANME-2 over ANME-1, at least in mud breccia from Perejil MVs. In contrast, the scarce presence or lack of these AOM-related lipid biomarkers in sediments from Kalinin and Schneider's Heart MVs, suggests that no recent active methane seepage

  6. Fueling plankton production by a meandering frontal jet: a case study for the Alboran Sea (Western Mediterranean).

    PubMed

    Oguz, Temel; Macias, Diego; Garcia-Lafuente, Jesus; Pascual, Ananda; Tintore, Joaquin

    2014-01-01

    A three dimensional biophysical model was employed to illustrate the biological impacts of a meandering frontal jet, in terms of efficiency and persistency of the autotrophic frontal production, in marginal and semi-enclosed seas. We used the Alboran Sea of the Western Mediterranean as a case study. Here, a frontal jet with a width of 15-20 km, characterized by the relatively low density Atlantic water mass, flows eastward within the upper 100 m as a marked meandering current around the western and the eastern anticyclonic gyres prior to its attachment to the North African shelf/slope topography of the Algerian basin. Its inherent nonlinearity leads to the development of a strong ageostrophic cross-frontal circulation that supplies nutrients into the nutrient-starved euphotic layer and stimulates phytoplankton growth along the jet. Biological production is larger in the western part of the basin and decreases eastwards with the gradual weakening of the jet. The higher production at the subsurface levels suggests that the Alboran Sea is likely more productive than predicted by the satellite chlorophyll data. The Mediterranean water mass away from the jet and the interiors of the western and eastern anticyclonic gyres remain unproductive. PMID:25372789

  7. Tectonic and stratigraphic evolution of the Western Alboran Sea Basin in the last 25 Myrs

    NASA Astrophysics Data System (ADS)

    Do Couto, Damien; Gorini, Christian; Jolivet, Laurent; Lebret, Noëmie; Augier, Romain; Gumiaux, Charles; d'Acremont, Elia; Ammar, Abdellah; Jabour, Haddou; Auxietre, Jean-Luc

    2016-05-01

    The Western Alboran Basin (WAB) formation has always been the subject of debate and considered either as a back-arc or a forearc basin. Stratigraphic analyses of high-resolution 2D seismic profiles mostly located offshore Morocco, enabled us to clarify the tectonic and stratigraphic history of the WAB. The thick pre-rift sequence located beneath the Miocene basin is interpreted as the topmost Malaguide/Ghomaride complex composing the Alboran domain. The structural position of this unit compared with the HP-LT exhumed Alpujarride/Sebtide metamorphic basement, leads us to link the Early Miocene subsidence of the basin with an extensional detachment. Above the Early Miocene, a thick Serravallian sequence marked by siliciclastic deposits is nearly devoid of extensional structures. Its overall landward to basinward onlap geometry indicates that the WAB has behaved as a sag basin during most of its evolution from the Serravallian to the late Tortonian. Tectonic reconstructions in map view and in cross section further suggest that the basin has always represented a strongly subsiding topographic low without internal deformation that migrated westward together with the retreating slab. We propose that the subsidence of the WAB was controlled by the pull of the dipping subducting lithosphere hence explaining the considerable thickness (10 km) of the mostly undeformed sedimentary infill.

  8. Tectonic and stratigraphic evolution of the Western Alboran Sea basin since the last 25 Myrs

    NASA Astrophysics Data System (ADS)

    Do Couto, Damien; Gorini, Christian; Jolivet, Laurent; Lebret, Noëmie; Augier, Romain; Gumiaux, Charles; D'Acremont, Elia; Ammar, Abdellah; Auxietre, Jean-Luc

    2016-04-01

    The Western Alboran Basin (WAB) formation has always been a matter of debate and was either considered as a backarc or a forearc basin. Based on stratigraphic analysis of high-resolution 2D seismic profiles mostly located offshore Morocco, the tectonic and stratigraphic history of the WAB is clarified. A thick pre-rift sequence is observed beneath the Miocene basin and interpreted as the topmost Malaguide/Ghomaride complex composing the Alboran domain. The structural position of this unit compared with the HP-LT exhumed Alpujarride/Sebtide metamorphic basement, leads us to link the Early Miocene subsidence of the basin with an extensional detachment. Above the Early Miocene, a thick Serravallian sequence marked by siliciclastic deposits is nearly devoid of extensional structures. Its overall landward to basinward onlap geometry indicates that the WAB has behaved as a sag basin during most of its evolution, from the Serravallian to the Late Tortonian. Tectonic reconstructions in map view and cross-section further suggest that the basin has always represented a strongly subsiding topographic low without internal deformation that has migrated westward together with the retreating slab. We propose that the subsidence of the WAB was controlled by the pull of the dipping subducting lithosphere explaining the large thickness (10 km) of the mostly undeformed sedimentary infill.

  9. Seismicity and active tectonics in the Alboran Sea, Western Mediterranean: Constraints from an offshore-onshore seismological network and swath bathymetry data

    NASA Astrophysics Data System (ADS)

    Grevemeyer, Ingo; Gràcia, Eulàlia; Villaseñor, Antonio; Leuchters, Wiebke; Watts, Anthony B.

    2015-12-01

    Seismicity and tectonic structure of the Alboran Sea were derived from a large amphibious seismological network deployed in the offshore basins and onshore in Spain and Morocco, an area where the convergence between the African and Eurasian plates causes distributed deformation. Crustal structure derived from local earthquake data suggests that the Alboran Sea is underlain by thinned continental crust with a mean thickness of about 20 km. During the 5 months of offshore network operation, a total of 229 local earthquakes were located within the Alboran Sea and neighboring areas. Earthquakes were generally crustal events, and in the offshore domain, most of them occurred at crustal levels of 2 to 15 km depth. Earthquakes in the Alboran Sea are poorly related to large-scale tectonic features and form a 20 to 40 km wide NNE-SSW trending belt of seismicity between Adra (Spain) and Al Hoceima (Morocco), supporting the case for a major left-lateral shear zone across the Alboran Sea. Such a shear zone is in accord with high-resolution bathymetric data and seismic reflection imaging, indicating a number of small active fault zones, some of which offset the seafloor, rather than supporting a well-defined discrete plate boundary fault. Moreover, a number of large faults known to be active as evidenced from bathymetry, seismic reflection, and paleoseismic data such as the Yusuf and Carboneras faults were seismically inactive. Earthquakes below the Western Alboran Basin occurred at 70 to 110 km depth and hence reflected intermediate depth seismicity related to subducted lithosphere.

  10. Evolution of the Alboran Sea hydrographic structures during July 1993

    NASA Astrophysics Data System (ADS)

    Lafuente, Jesús García.; Cano, Natalio; Vargas, Manuel; Rubín, Juan P.; Hernández-Guerra, Alonso

    1998-01-01

    During the ICTIOALBORAN-0793 multidisciplinary oceanographic survey carried out in July 1993 by the Instituto Español de Oceanografı´a (IEO) in the Alboran Sea, some anomalous features were detected. One was the presence of a small cyclonic eddy in the western Alboran Basin, close to the African coast. The upper layer of the eddy consisted of Mediterranean Surface Water and was separated from its supposed source (the northern Alboran Sea) by the Atlantic Jet. Another feature was the probable temporary interruption of the flow of fresh Atlantic Water (S≈36.5) into the eastern Alboran Basin and its replacement by a modified (saltier) Atlantic Water. These features can be explained assuming a time evolution of the surface circulation in the Alboran Sea forced by speed variations in the inflowing Atlantic Water through the Strait of Gibraltar. A collection of satellite images covering the survey period and across-strait sea level difference data, indicative of the geostrophic velocity of the inflow through the Strait, were used to check this assumption. Both sets of data supplied independent but compatible information in the sense that they complemented each other and gave support to the proposed evolving model. Finally, some speculative ideas attempting to correlate the inferred variability in the Alboran Sea with the state of the baroclinic water exchange through the Strait of Gibraltar (maximal or submaximal) are discussed.

  11. Seismotectonics and Seismic Structure of the Alboran Sea, Western Mediterranean - Constraints from Local Earthquake Monitoring and Seismic Refraction and Wide-Angle Profiling

    NASA Astrophysics Data System (ADS)

    Leuchters, W.; Grevemeyer, I.; Ranero, C. R.; Villasenor, A.; Booth-Rea, G.; Gallart, J.

    2011-12-01

    The Alboran Basin is located in the western-most Mediterranean Sea and is surrounded by the Gibraltar-Betic and Rif orogenic arc. Geological evidence suggests that the most important phase of formation started in the early-to-mid-Miocene. Currently two conflicting models are discussed for its formation: One model proposes contractive tectonics producing strike-slip faults and folds with sedimentation occurring in synclinal basins and in regions of subsidiary extension in transtensional fault segments. A second model proposes slab roll back that caused contraction at the front of the arc and coeval overriding plate bending and extension and associated arc magmatism. However, this phase has been partially masked by late Miocene to present contractive structures, caused by the convergence of Africa and Iberia. Two German/Spanish collaborative research projects provided excellent new seismological and seismic data. Onshore/offshore earthquake monitoring received a wealth of local earthquake data to study seismotectonics and yielded the average 1D velocity structure of the Alboran/Betics/Rif domain. In the Alboran Basin most earthquakes occur below 20 km along a diffuse fault zone, crossing the Alboran Sea from the Moroccan to the Spanish coast. Further, earthquakes along the northern portion of the Alboran Ridge show thrust mechanisms and compression roughly normal to the vector of plate convergence between Africa and Iberia. A 250 km long seismic refraction and wide-angle profile was acquired coincident with the existing multi-channel seismic (MCS) ESCI-Alb2 line using the German research vessel Meteor. Shots fired with a 64-litre airgun array were recorded on 24 ocean-bottom seismometer (OBS) and ocean-bottom hydrophone (OBH) stations. The profile run roughly along the axis of the basin, circa 65 km off the coast of Morocco, north of the Alboran Ridge. It continues in an ENE direction to end north of the Algeria coast. Using seismic tomography we mapped the crustal

  12. Last glacial to Holocene productivity and oxygen changes based on benthic foraminiferal assemblages from the western Alboran Sea

    NASA Astrophysics Data System (ADS)

    Pérez-Asensio, José N.; Cacho, Isabel; Frigola, Jaime; Pena, Leopoldo D.; Asioli, Alessandra; Kuhlmann, Jannis; Huhn, Katrin

    2016-04-01

    Late glacial to Holocene productivity and oxygen changes in the Alboran Sea were investigated analyzing benthic foraminiferal assemblages from the marine sediment core HER-GC-UB06. This 255 cm-long core was recovered at 946 m water depth in the Alboran Sea (western Mediterranean Sea) and includes homogeneous greyish clays from the last 23 ka. Nowadays, the core site is bathed by the Western Mediterranean Deep Water (WMDW) and near the overlying Levantine Intermediate Water (LIW). Benthic foraminifera from the size fraction >63 μm were identified at species level and counted until reaching at least 300 individuals. Q-mode principal component analyses (PCA) was performed to establish benthic foraminiferal assemblages. In addition, benthic foraminifera were classified according to their microhabitat preferences. Diversity was assessed with several diversity indices. Four benthic foraminiferal assemblages have been identified along the core. The distribution of these assemblages records changes in productivity and oxygen conditions during the last 23 ka. The last glacial and deglaciation interval, 23-12.5 ka, shows low diversity and is characterized by the Nonionella iridea assemblage, which includes Cassidulina laevigata, Bolivina dilatata, Nonionoides turgida and Cibicides pachyderma as secondary taxa. This assemblage can be interpreted as a moderately oxygenated mesotrophic environment with episodic pulses of fresh organic matter. Although general mesotrophic conditions prevail, the Last Glacial Maximum shows a more oligotrophic and better oxygenated setting as suggested by higher abundance of epifaunal-shallow infaunal taxa. In contrast, along the Bølling-Allerød eutrophic conditions with higher productivity and lower oxygenation are recorded by a deep infaunal taxa maximum. During the Younger Dryas (YD) and the earliest Holocene (12.5-10.5 ka), the Bolivina dilatata assemblage dominates coinciding with a lower diversity, especially during the YD. This species

  13. Controls of picophytoplankton abundance and composition in a highly dynamic marine system, the Northern Alboran Sea (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Amorim, Ana L.; León, Pablo; Mercado, Jesús M.; Cortés, Dolores; Gómez, Francisco; Putzeys, Sebastien; Salles, Soluna; Yebra, Lidia

    2016-06-01

    The Alboran Sea is a highly dynamic basin which exhibits a high spatio-temporal variability of hydrographic structures (e.g. fronts, gyres, coastal upwellings). This work compares the abundance and composition of picophytoplankton observed across the northern Alboran Sea among eleven cruises between 2008 and 2012 using flow cytometry. We evaluate the seasonal and longitudinal variability of picophytoplankton on the basis of the circulation regimes at a regional scale and explore the presence of cyanobacteria ecotypes in the basin. The maximal abundances obtained for Prochlorococcus, Synechococcus and picoeukaryotes (12.7 × 104, 13.9 × 104 and 8.6 × 104 cells mL- 1 respectively) were consistent with those reported for other adjacent marine areas. Seasonal changes in the abundance of the three picophytoplankton groups were highly significant although they did not match the patterns described for other coastal waters. Higher abundances of Prochlorococcus were obtained in autumn-winter while Synechococcus and picoeukaryotes exhibited a different seasonal abundance pattern depending on the sector (e.g. Synechococcus showed higher abundance in summer in the west sector and during winter in the eastern study area). Additionally, conspicuous longitudinal gradients were observed for Prochlorococcus and Synechococcus, with Prochlorococcus decreasing from west to east and Synechococcus following the opposite pattern. The analysis of environmental variables (i.e. temperature, salinity and inorganic nutrients) and cell abundances indicates that Prochlorococcus preferred high salinity and nitrate to phosphate ratio. On the contrary, temperature did not seem to play a role in Prochlorococcus distribution as it was numerically important during the whole seasonal cycle. Variability in Synechococcus abundance could not be explained by changes in any environmental variable suggesting that different ecotypes were sampled during the surveys. In particular, our data would indicate

  14. Magnetotelluric Measurements in the Alboran Sea

    NASA Astrophysics Data System (ADS)

    Evans, R. L.; Jegen, M. D.; Garcia, X. A.; Matsuno, T.; Elsenbeck, J.; Worzewski, T. W.

    2010-12-01

    The PICASSO program aims to understand the tectonic history of the western Mediterranean, between Spain and Morocco, where conflicting models have suggested that the region is either a relict subduction system or a zone of mantle delamination. As part of this program we successfully deployed 12 seafloor MT instruments in water depths greater than 800m in the Alboran sea. We plan to deploy additional instruments in the fall of 2010. An initial analysis of the data shows complex MT response functions with strong distortion due to seafloor topography and coast effect. This coast effect suggests a fairly resistive lithosphere beneath the seafloor, which is confirmed after inspection of the preliminary responses. We will present the data collected thus far, along with preliminary models of the profiles collected.

  15. Mantle structure beneath the Alboran Sea from shear wave splitting

    NASA Astrophysics Data System (ADS)

    Alpert, L. A.; Becker, T. W.; Miller, M. S.; Allam, A. A.

    2011-12-01

    New seismological investigations in the Alboran domain of the western Mediterranean, as part of the PICASSO experiment, support geodynamic models which constrain the mantle structure beneath the Alboran Sea. We evaluate global circulation models in the context of seismic anistropy as inferred from SKS/SKKS splitting observations. Using instantaneous velocity fields from 3-D flow models with variable mantle density based on several tomography and seismicity based models, we calculate the predicted anisotropy, fast polarization direction (FPD), and delay times in order to explain the complex tectonic and geologic history of the Alboran Sea region. Slab rollback, delamination, and convective removal processes have been invoked to explain the synorogenic extension in the Alboran and recently published splitting measurements show north-east trending FPD across the Iberian margin with a rotation to the southeast that follows the curve of the Gibraltar arc, suggested by the authors as supporting west-directed slab rollback. Our new measurements from 39 stations substantiate the measurements in southern Spain, but we find a striking, nearly 90 degree rotation in azimuth and reduced delay times across the High Atlas Mountains in northern Morocco. These splitting patterns define three distinct regions we attempt to predict with our geodynamic models. Here, we test several differently-oriented subduction, slab break-off, and delamination scenarios. Our preliminary results show that density models which include a curved, northeast trending slab predict the east-northeast oriented measurements along the Iberian margin. Imposing a drip structure beneath the Alboran Sea also predicts these orientations. In order to predict the rotation of the FPD we find in Morocco, however, most models require a stiff keel beneath the African craton.

  16. Interaction between seabed morphology and water masses around the seamounts on the Motril Marginal Plateau (Alboran Sea, Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Palomino, Desirée; Vázquez, Juan-Tomás; Ercilla, Gemma; Alonso, Belén; López-González, Nieves; Díaz-Del-Río, Víctor

    2011-12-01

    The seabed morphology in the vicinity of the seamounts on the Motril Marginal Plateau (northern Alboran Sea) was investigated using high-resolution (sparker) and very high-resolution (TOPAS) seismic reflection profiles and multibeam bathymetry. The aim of the study was to determine the recent geological processes, and in particular those that control the contourite depositional system associated with the intermediate and deep Mediterranean water masses. Six groups of morphological features were identified: structural features (seamount tops, tectonic depressions), fluid escape-related features (pockmarks), mass-movement features (gullies, slides), bottom-current features (moats, scour marks, terraces, elongated and separated drifts, plastered drifts, confined drifts, sheeted drifts), mixed features (ridges) and biogenic features (including evidence of (dead) cold water corals such as Lophelia pertusa and Madrepora oculata). The main processes controlling the formation of these features are recent tectonic activity and the interaction of Mediterranean water masses with the seafloor topography. Seamounts act as topographic barriers that affect the pathway and velocity of the deep Mediterranean water masses, which are divided into strands that interact with the surrounding seafloor. The influence of the intermediate Mediterranean water mass, by contrast, is restricted mainly to the tops of the seamounts. Sediment instability and fluid-escape processes play a minor role, their occurrence being probably related to seismicity.

  17. Looking for long-term changes in hydroid assemblages (Cnidaria, Hydrozoa) in Alboran Sea (South-Western Mediterranean): a proposal of a monitoring point for the global warming

    NASA Astrophysics Data System (ADS)

    González-Duarte, Manuel María; Megina, Cesar; Piraino, Stefano

    2014-12-01

    In the last 20-30 years, the temperature of the Mediterranean Sea has increased and global warming is allowing the establishment of tropical-affinity species into more temperate zones. Sessile communities are particularly useful as a baseline for ecological monitoring; however, a lack of historical data series exists for sessile marine organisms without commercial interest. Hydroids are ubiquitous components of the benthic sessile fauna on rocky shores and have been used as bio-indicators of environmental conditions. In this study on the benthic hydroid assemblages of the Chafarinas Islands (Alboran Sea, South-Western Mediterranean), we characterized the hydroid assemblages, identified the bathymetric gradients, and compared them with a previous study carried out in 1991. Hydroid assemblages showed a significant difference both between year and among depths. Furthermore, eight species not present in 1991 were found, including two possible new species and the tropical and subtropical species Sertularia marginata. Due to its strategic position at the entrance of the Mediterranean and the existence of previous data on hydroid assemblages, the Chafarinas Islands are proposed as a possible monitoring point for entrance of Atlantic tropical species into the Mediterranean Sea.

  18. Distribution of seawater fluorescence and dissolved flavins in the Almeria-Oran front (Alboran Sea, western Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Momzikoff, A.; Dallot, S.; Gondry, G.

    1994-08-01

    Seawater fluorescence in the blue region of the spectrum (excitation at 360 nm) due to fluorescent dissolved organic matter (FDOM), and dissolved flavins were investigated in the Almeria-Oran geostrophic front (western Mediterranean) in the 0-200 m layer. Seawater fluorescence increased with depth from a minimum in the jet divergence, increasing towards the oligotrophic waters located outside the jet zone, and reaching a maximum in the right side of the jet, a convergence zone. Comparisons with other recorded parameters suggested both physical and biological factors were involved in its distribution along the transect. Photodegradation due to light-penetration and seawater enrichment with FDOM due to biological activity appeared as driving factors of fluorescence distribution. Fluorescence increase along the secondary circulation of the jet was attributed to the combined effects of aging of a bloom (where it was suggested that both auto- and heterotrophic populations were involved) and photodegradation. FDOM of deeper waters (found in the divergence zone) was inferred to be less photodegradable than that generated in the productive layers (the convergence zone). From these data fluorescence in the oligotrophic sites was deduced to originate from prevaling biological activity. Three flavins were investigated: riboflavin and its photoproducts (lumichrome and lumiflavin). The vertical distribution of flavins was marked by a stratification into two layers of enhanced concentrations. The upper one was found to coincide with the upper chlorophyll layer (DCM or DCM1), the lower one with the lower chlorophyll layer (DCM2, where it occurred) and/or with the base of the halocline. From these depth coincidences both auto- and heterotrophic populations were inferred to be sources of flavins although their respective contributions were hard to determine. As for fluorescence, an increase of flavins was found in the jet zone. However significant differences were found between the

  19. Scenarios for earthquake-generated tsunamis on a complex tectonic area of diffuse deformation and low velocity: The Alboran Sea, Western Mediterranean

    USGS Publications Warehouse

    Alvarez-Gomez, J. A.; Aniel-Quiroga, I.; Gonzalez, M.; Olabarrieta, M.; Carreno, E.

    2011-01-01

    The tsunami impact on the Spanish and North African coasts of the Alboran Sea generated by several reliable seismic tsunamigenic sources in this area was modeled. The tectonic setting is complex and a study of the potential sources from geological data is basic to obtain probable source characteristics. The tectonic structures considered in this study as potentially tsunamigenic are: the Alboran Ridge associated structures, the Carboneras Fault Zone and the Yusuf Fault Zone. We characterized 12 probable tsunamigenic seismic sources in the Alboran Basin based on the results of recent oceanographical studies. The strain rate in the area is low and therefore its seismicity is moderate and cannot be used to infer characteristics of the major seismic sources. These sources have been used as input for the numerical simulation of the wave propagation, based on the solution of the nonlinear shallow water equations through a finite-difference technique. We calculated the Maximum Wave Elevations, and Tsunami Travel Times using the numerical simulations. The results are shown as maps and profiles along the Spanish and African coasts. The sources associated with the Alboran Ridge show the maximum potential to generate damaging tsunamis, with maximum wave elevations in front of the coast exceeding 1.5. m. The Carboneras and Yusuf faults are not capable of generating disastrous tsunamis on their own, although their proximity to the coast could trigger landslides and associated sea disturbances. The areas which are more exposed to the impact of tsunamis generated in the Alboran Sea are the Spanish coast between Malaga and Adra, and the African coast between Alhoceima and Melilla. ?? 2011 Elsevier B.V.

  20. A new diagnosis of the genus Delectona (Porifera, Demospongiae), with a description of a new species from the Alboran Sea (western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Rosell, D.

    1996-12-01

    A redescription of the genus Delectona is provided, based on information gained by the finding of a new species, D. alboransis, from the Alboran Sea (southwestern Mediterranean Sea). Up to now, this genus contained only one species: Delectona higgini, from the Indian Ocean, which has not been recorded since 1880. The presence of megascleres in the new species and the different ranges of amphiaster lengths of the two species are the main features allowing a differentiation. In addition, the excavating capability of sponges of this genus is questioned, following the observations on the external morphology of D. alboransis. Our results support the hypothesis of other authors that some areas of the circalittoral level of the Alboran Sea may represent a redoubt of relict species with Indo-Pacific affinities.

  1. Modeling the impact of tidal flows on the biological productivity of the Alboran Sea

    NASA Astrophysics Data System (ADS)

    Sánchez-Garrido, José C.; Naranjo, C.; Macías, D.; García-Lafuente, J.; Oguz, T.

    2015-11-01

    The control of phytoplankton production by tidal forcing in the Alboran Sea is investigated with a high-resolution ocean circulation model coupled to an ecosystem model. The aim of the modeling efforts was to elucidate the role of tides in sustaining the high biological productivity of the Alboran Sea, as compared with the rest of the Mediterranean subbasins. It is shown that tidal forcing accounts for an increase of phytoplankton biomass and primary productivity in the basin of about 40% with respect to a nontidal circulation, and about 60% in the western Alboran Sea alone. The tidal dynamics of the Strait of Gibraltar is shown to be the primary factor in determining the enhancement of productivity, pumping nutrients from depth to the photic zone in the Alboran Sea. Model results indicate that the biological implications of the propagating internal tides are small. These results imply that nutrient transports through the Strait of Gibraltar have to be parametrized in ocean models that do not resolve tides in order to properly represent the biochemical budgets of the Alboran Sea.

  2. Rapid changes in temperature and hydrology in the western Mediterranean during the last climatic cycle from the high resolution record ODP Site 976 (Alboran Sea)

    NASA Astrophysics Data System (ADS)

    Combourieu-Nebout, Nathalie; Peyron, Odile; Bout-Roumazeille, Viviane

    2013-04-01

    High-resolution pollen record, pollen-inferred climate reconstructions and clay mineralogy records were performed over the last climatic cycle from the ODP Site 976 located in the Alboran Sea Continental paleoenvironment proxies were provided on the same samples to depict the short and long term variability of Mediterranean vegetation and climate during the two last terminations and the last two interglacials. Pollen record highlights the vegetation changes associated to climate variability while clay mineralogy informs about the terrigenous inputs related to wind and/or river transport. During the last cycle, both vegetation and clay minerals data have recorded the response of continental ecosystems to all the climate events which characterized the last 135000 years. The Dansgaard/Oeschger oscillations and the rapid cold events evidenced in the North Atlantic (Bond et al., 1993; McManus et al., 1994) are well evidenced in the ODP sequence. Thus, warm interstadials show a strong colonisation of temperate Mediterranean forest while cold events are particularly well expressed by correlative increases in dry steppic to semi-desert formation with enhanced input from African desert dust (Bout-Roumazeilles et al, 2007 and in progress). A special attention has been paid on the two last glacial/interglacial transitions 1 and 2 that occurred before the interglacial inception in order to better understand what happened during these key-periods in continental areas and also better understand how reacts the Mediterranean climate regime through these two periods. The two high resolution records from the Terminaison 2/ Stage 5 and Terminaison 1/ Holocene are compared especially with regards to the wind regime modifications through atmospheric supply, and to hydrological and temperature changes reconstructed from pollen data. Therefore for these two key-periods, we aim to produce a robust climate reconstruction pollen-inferred precipitation and temperature from the 0DP 976 marine

  3. Geotechnical properties and preliminary assessment of sediment stability on the continental slope of the northwestern Alboran Sea

    USGS Publications Warehouse

    Baraza, J.; Ercilla, G.; Lee, H.J.

    1992-01-01

    Laboratory analysis of core samples from the western Alboran Sea slope reveal a large variability in texture and geotechnical properties. Stability analysis suggests that the sediment is stable under static gravitational loading but potentially unstable under seismic loading. Slope failures may occur if horizontal ground accelerations greater than 0.16 g are seismically induced. The, Alboran Sea is an active region, on which earthquakes inducing accelerations big enough to exceed the shear strength of the soft soil may occur. Test results contrast with the apparent stability deduced from seismic profiles. ?? 1992 Springer-Verlag New York Inc.

  4. Miocene magmatism and tectonics within the Peri-Alboran orogen (western Mediterranean)

    NASA Astrophysics Data System (ADS)

    El Azzouzi, M.; Bellon, H.; Coutelle, A.; Réhault, J.-P.

    2014-07-01

    The aim of this paper concerns Miocene igneous activity in the Alboran Sea and Peri-Alboran area (northern Morocco, western Algeria and Betic Cordilleras in Spain), considering its age and its location with regard to major tectonics structures. We have compiled previous K-Ar isotopic ages of lavas and plutonic boulders and intrusives with an error of ±1σ and completed this set by a new K-Ar isotopic age for andesitic tuffites from Alboran Island. Geochemistry of most of these samples has been considered after previous analyses completed with new data for Spain magmatism. These two sets of data allow us to place the magmatic activity within the regional stratigraphy and tectonics and their chronological framework of the three major tectonic phases of the Maghrebian orogen, at 17 Ma (Burdigalian), 15 Ma (Langhian) and 9 Ma (Tortonian). Petro-geochemical characteristics are compared through time and geographical locations. A major goal of this coupled approach is to help the elaboration of possible geodynamical processes. As an application, we present the case study of the Dellys, Djinet and Thenia region (east of Algiers) where the successive magmatic events between 19.4 ± 1 and 11.6 ± 0.5 Ma are closely related to the local tectonics and sedimentation. The Peri-Alboran igneous activity is placed in a multidisciplinary framework. Timing of activity is defined according to the ages of the neighbouring sedimentary units and the K-Ar ages of igneous rocks. In Spain, the Cabo de Gata-Carboneras magmatic province displays late Oligocene and early Miocene leucogranitic dikes, dated from 24.8 ± 1.3 to 18.1 ± 1.2 Ma; three following andesitic to rhyolitic events took place around 15.1 ± 0.8 to 14.0 ± 0.7 Ma, 11.8 ± 0.6 to 9.4 ± 0.4 Ma, 8.8 ± 0.4 to 7.9 ± 0.4 Ma; this last event displays also granitic rocks. Lamproitic magmas dated between 8.4 ± 0.4 and 6.76 ± 0.04 Ma were emplaced after the Tortonian phase. In Morocco, after the complex building of the Ras Tarf

  5. Surface mesoscale pico-nanoplankton patterns at the main fronts of the Alboran Sea

    NASA Astrophysics Data System (ADS)

    León, P.; Blanco, J. M.; Flexas, M. M.; Gomis, D.; Reul, A.; Rodríguez, V.; Jiménez-Gómez, F.; Allen, J. T.; Rodríguez, J.

    2015-03-01

    The mesoscale (10-100 km, days-weeks) plays a key role in the Ocean's ecosystem structure and dynamics. This work compares the pico-nanoplankton patterns observed in the Alboran Sea (Western Mediterranean) during three oceanographic cruises. We analyse its response to different expressions of mesoscale circulation associated with the three major hydrodynamic features in the basin; namely the Northwestern Alboran Front (NWAF, surveyed in OMEGA-1 cruise), the Almeria-Oran Front (AOF, surveyed in OMEGA-2 cruise) and the Western Alboran Gyre (WAG, surveyed in BIOMEGA cruise). The first two surveys were carried out under the most typical quasi-stationary twin gyre conditions of the Alboran Sea, whereas the third cruise was performed after an eastward migration of the WAG. The analysis of pico and nanoplankton populations was carried out using flow cytometry. The patchiness observed in the three cruises indicates an association of phytoplankton peaks with the main frontal structures: abundances were higher in the NWAF/upwelling area in OMEGA-1, at the Mediterranean side of the AOF in OMEGA-2, and at a tongue of recent Atlantic Water west of the WAG in BIOMEGA. However, a more detailed analysis reveals that different factors explain the origin of the phytoplankton biomass in each front/cruise. Mixing processes at the Strait of Gibraltar and the subsequent advection of water properties into the Western Alboran Sea were the mechanisms responsible for the abundances observed in the NWAF. The highest concentrations observed in the AOF were related to the intrusion of Mediterranean Surface Waters to the north of the front. During the migrating WAG the phytoplankton distribution was influenced by the formation of a new gyre. The relation between phytoplankton and mesoscale dynamics is further explored in terms of vertical velocity diagnosis. In all cases, intense vertical motion is negatively correlated with the abundance of phytoplankton populations. This resulted from the

  6. Impacts of reprocessed altimetry on the surface circulation and variability of the Western Alboran Gyre

    NASA Astrophysics Data System (ADS)

    Juza, Mélanie; Escudier, Romain; Pascual, Ananda; Pujol, Marie-Isabelle; Taburet, Guillaume; Troupin, Charles; Mourre, Baptiste; Tintoré, Joaquín

    2016-08-01

    New altimetry products in semi-enclosed seas are of major interest given the importance of the coastal-open ocean interactions. This study shows how reprocessed altimetry products in the Mediterranean Sea from Archiving, Validation and Interpolation of Satellite Oceanographic data (AVISO) have improved the representation of the surface circulation over the 1993-2012 period. We focus on the Alboran Sea, which is the highest mesoscale activity area of the western Mediterranean. The respective impacts of the new mean dynamic topography (MDT) and mapped sea level anomaly (MSLA) on the description of the Western Alboran Gyre (WAG) are quantitatively evaluated. The temporal mean and variability of the total kinetic energy have been significantly increased in the WAG considering both the new MDT and MSLA (by more than 50%). The new MDT has added 39% to the mean kinetic energy, while the new MSLA has increased the eddy kinetic energy mean (standard deviation) by 53% (30%). The new MSLA has yielded higher variability of total (eddy) kinetic energy, especially in the annual frequency band by a factor of 2 (3). The MDT reprocessing has particularly increased the low-frequency variability of the total kinetic energy by a factor of 2. Geostrophic velocities derived from the altimetry products have also been compared with drifter data. Both reprocessed MDT and MSLA products intensify the velocities of the WAG making them closer to the in situ estimations, reducing the root mean square differences and increasing the correlation for the zonal and meridional components. The results obtained using refined coastal processing of altimetry products and new observational data are very encouraging to better understand the ocean circulation variability and coastal-open ocean interactions, and for potential improvements in other sub-basins, marginal seas and coastal global ocean.

  7. The depiction of Alboran Sea Gyre during Donde Va? using remote sensing and conventional data

    NASA Technical Reports Server (NTRS)

    Laviolette, P. E.

    1984-01-01

    Experienced oceanographic investigators have come to realize that remote sensing techniques are most successful when applied as part of programs of integrated measurements aimed at solving specific oceanographic problems. A good example of such integration occurred during the multi-platform international experiment, Donde Va? in the Alboran Sea during the period June through October, 1982. The objective of Donde Va? was to derive the interrelationship of the Atlantic waters entering the Mediterranean Sea and the Alboran Sea Gyre. The experimental plan conceived solely with this objective in mind consisted of a variety of remote sensing and conventional platforms: three ships, three aircraft, five current moorings, two satellites and a specialized beach radar (CODAR). Integrated analyses of these multiple-data sets are still being conducted. However, the initial results show detailed structure of the incoming Atlantic jet and Alboran Sea Gyre that would not have been possible by conventional means.

  8. Identification of T-Waves in the Alboran Sea

    NASA Astrophysics Data System (ADS)

    Carmona, Enrique; Almendros, Javier; Alguacil, Gerardo; Soto, Juan Ignacio; Luzón, Francisco; Ibáñez, Jesús M.

    2015-11-01

    Analyses of seismograms from ~1,100 north-Moroccan earthquakes recorded at stations of the Red Sísmica de Andalucía (Southern Spain) reveal the systematic presence of late phases embedded in the earthquake codas. These phases have distinctive frequency contents, similar to the P and S spectra and quite different to the frequency contents of the earthquake codas. They are best detected at near-shore stations. Their amplitudes decay significantly with distance to the shoreline. The delays with respect to the P-wave onsets of the preceding earthquakes are consistently around 85 s. Late phases are only detected for earthquakes located in a small region of about 100 × 60 km centered at 35.4°N, 4.0°W near the northern coast of Morocco. Several hypotheses could, in principle, explain the presence of these late phases in the seismograms, for example, the occurrence of low-energy aftershocks, efficient wave reflections, or Rayleigh waves generated along the source-station paths. However, we conclude that the most-likely origin of these phases corresponds to the incidence of T-waves (generated by conversion from elastic to acoustic energy in the north-Moroccan coast) in the southern coast of the Iberian Peninsula. T-waves are thought to be generated by energy trapping in low-velocity channels along long oceanic paths; in this case, we demonstrate that they can be produced in much shorter paths as well. Although T-waves have been already documented in other areas of the Mediterranean Sea, this is the first time that they have been identified in the Alboran Sea.

  9. Evolution of the continental margin of southern Spain and the Alboran Sea

    USGS Publications Warehouse

    Dillon, William P.; Robb, James M.; Greene, H. Gary; Lucena, Juan Carlos

    1980-01-01

    Seismic reflection profiles and magnetic intensity measurements were collected across the southern continental margin of Spain and the Alboran basin between Spain and Africa. Correlation of the distinct seismic stratigraphy observed in the profiles to stratigraphic information obtained from cores at Deep Sea Drilling Project site 121 allows effective dating of tectonic events. The Alboran Sea basin occupies a zone of motion between the African and Iberian lithospheric plates that probably began to form by extension in late Miocene time (Tortonian). At the end of Miocene time (end of Messinian) profiles show that an angular unconformity was cut, and then the strata were block faulted before subsequent deposition. The erosion of the unconformity probably resulted from lowering of Mediterranean sea level by evaporation when the previous channel between the Mediterranean and Atlantic was closed. Continued extension probably caused the block faulting and, eventually the opening of the present channel to the Atlantic through the Strait of Gibraltar and the reflooding of the Mediterranean. Minor tectonic movements at the end of Calabrian time (early Pleistocene) apparently resulted in minor faulting, extensive transgression in southeastern Spain, and major changes in the sedimentary environment of the Alboran basin. Active faulting observed at five locations on seismic profiles seems to form a NNE zone of transcurrent movement across the Alboran Sea. This inferred fault trend is coincident with some bathymetric, magnetic and seismicity trends and colinear with active faults that have been mapped on-shore in Morocco and Spain. The faults were probably caused by stresses related to plate movements, and their direction was modified by inherited fractures in the lithosphere that floors the Alboran Sea.

  10. Mesoscale high-frequency variability in the Alboran Sea and its influence on fish larvae distributions

    NASA Astrophysics Data System (ADS)

    Vargas-Yáñez, Manuel; Sabatés, Ana

    2007-12-01

    This work analyses a multidisciplinary data set including hydrological and meteorological data, satellite images, and fish larvae abundance from a high-frequency experiment conducted along a north-south transect across the Western Alboran Sea anticyclonic gyre. Four consecutive occupations of the transect, crossing the frontal area, evidenced the high-frequency variability of hydrological structures and its influence on the latitudinal and vertical distribution of fish larvae in a period of a few days. The influence of dynamical processes on fish larvae depends on the location of the spawning as well as on the larval fish position in the water column. Wind induced upwelling and/or the southward drift of the Atlantic current transport larvae of neritic species, such as Sardina pilchardus and Engraulis encrasicolus to open sea areas. At the same time, these events bring about alterations in the latitudinal and vertical distributions of mesopelagic fish larvae. The species with a relatively surface distribution, as Ceratoscopelus maderensis, were transported and accumulated to the south of the Atlantic Jet (AJ), while those with a deeper distribution in the water column, as Maurolicus muelleri or Benthosema glaciale, would be upwelled and concentrated to the north. This study shows that it is difficult to extract conclusions about the mean or preferential distributions of fish larvae when one single/synoptic survey is considered and that time evolution of hydrological structures has to be considered in order to conclude.

  11. Structural record of Lower Miocene westward motion of the Alboran Domain in the Western Betics, Spain

    NASA Astrophysics Data System (ADS)

    Frasca, Gianluca; Gueydan, Frédéric; Brun, Jean-Pierre

    2015-08-01

    In the framework of the Africa-Europe convergence, the Mediterranean system presents a complex interaction between subduction rollback and upper-plate deformation during the Tertiary. The western end of the system shows a narrow arcuate geometry across the Gibraltar arc, the Betic-Rif belt, in which the relationship between slab dynamics and surface tectonics is not well understood. The present study focuses on the Western Betics, which is characterized by two major thrusts: 1) the Internal/External Zone Boundary limits the metamorphic domain (Alboran Domain) from the fold-and-thrust belts in the External Zone; 2) the Ronda Peridotites Thrust allows the juxtaposition of a strongly attenuated lithosphere section with large bodies of sub-continental mantle rocks on top of upper crustal rocks. New structural data show that two major E-W strike-slip corridors played a major role in the deformation pattern of the Alboran Domain, in which E-W dextral strike-slip faults, N60° thrusts and N140° normal faults developed simultaneously during dextral strike-slip simple shear. Olistostromic sediments of Lower Miocene age were deposited and deformed in this tectonic context and hence provide an age estimate for the inferred continuous westward translation of the Alboran Domain that is accommodated by an E-W lateral (strike-slip) ramp and a N60° frontal thrust. The crustal emplacement of large bodies of sub-continental mantle may occur at the onset of this westward thrusting in the Western Alboran domain. At lithosphere-scale, we interpret the observed deformation pattern as the subduction upper-plate expression of a lateral slab tear and its westward propagation since the Lower Miocene.

  12. Atmospheric-induced variability of hydrological and biogeochemical signatures in the NW Alboran Sea. Consequences for the spawning and nursery habitats of European anchovy

    NASA Astrophysics Data System (ADS)

    Macías, D.; Catalán, I. A.; Solé, J.; Morales-Nin, B.; Ruiz, J.

    2011-12-01

    The north-western Alboran Sea is a highly dynamic region in which the hydrological processes are mainly controlled by the entrance of the Atlantic Jet (AJ) through the Strait of Gibraltar. The biological patterns of the area are also related to this variability in which atmospheric pressure distributions and wind intensity and direction play major roles. In this work, we studied how changes in atmospheric forcing (from high atmospheric pressure over the Mediterranean to low atmospheric pressure) induced alterations in the physical and biogeochemical environment by re-activating coastal upwelling on the Spanish shore. The nursery area of European anchovy ( Engraulis encrasicolus) in the NW Alboran Sea, confirmed to be the very coastal band around Malaga Bay, did not show any drastic change in its biogeochemical characteristics, indicating that this coastal region is somewhat isolated from the rest of the basin. Our data also suggests that anchovy distribution is tightly coupled to the presence of microzooplankton rather than mesozooplankton. Finally, we use detailed physical and biological information to evaluate a hydrological-biogeochemical coupled model with a specific hydrological configuration to represent the Alboran basin. This model is able to reproduce the general circulation patterns in the region forced by the AJ movements only including two variable external forcings; atmospheric pressure over the western Mediterranean and realistic wind fields.

  13. The Climatological Annual Cycle of Satellite-derived Phytoplankton Pigments in the Alboran Sea: A Physical Interpretation

    NASA Technical Reports Server (NTRS)

    Garcia-Gorriz, E.; Carr, M. E.

    1998-01-01

    The circulation and upwelling processes (coastal and gyre-induced) that control the phytoplankton distribution in the Alboran sea are examined by analyzing monthly climatological patterns of Coastal Zone Color Scanner (CZCS) pigment concentrations, sea surface temperatures, winds, and seasonal geostrophic fields.

  14. Role of structural inheritances and major transfer fault-zones in the tectonic history of the Alboran Basin (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Comas, Menchu; Crespo-Blanc, Ana; Balanya, Juan Carlos

    2014-05-01

    The geodynamic evolution of the Gibraltar Arc System (GAS), which involves the origin and development of the Alboran back-arc basin, occurred during the Neogene related to the westward moving of the Alboran Domain (the Betic-Rifean hinterland) within a context of NNW-SSE plate-tectonic convergence. In this contribution we document shallow-crustal structures, deformation partitioning, and the different structural domains from the tectonic framework beneath the Alboran Sea. Furthermore, we focus the critical role of inherited crustal structures and major transfer faults within a coherent sequence of Miocene to Recent deformation phases. Early Miocene extensional processes conditioned substantial thinning and the exhumation of the metamorphic Alboran Domain before the opening of the Alboran Basin. Beneath the Alboran Sea, an ENE-SSW directed back-arc extension (from about 16 to 8.5 Ma, late Burdigalian to late Tortonian) affected both the metamorphic basement (the crustal Alboran Domain) and the overlying Miocene sedimentary units. This extension resulted in major low-angle normal faults, and NNW-SSE trending grabens connected by ENE-SSW transtensional transfer-faults, both happening in concomitance with the westward migration (around 200 km) of the Alboran Domain. The geometry of the extensional structures constrains the manner, timing and amount of the coeval crustal thinning. In the late Tortonian (about 8.5 Ma) a dominant N-S directed compressional phase caused inversions of former extensional faults, discrete folding, and strike-slip faulting. This compressional event triggered the spectacular West Alboran shale-diapirism from over-pressured basal units. At the South and Eastern Alboran and at the transition to the Algeria basins, a pervasive period of NW-SE directed compressional deformation (from about 7 Ma onwards) that affected the whole basin is patent. Long lasting compressional conditions since the late Tortonian resulted in a dramatic structural

  15. Role of the Alboran Sea volcanic arc choking the Mediterranean to the Messinian salinity crisis and foundering biota diversification in North Africa and Southeast Iberia

    NASA Astrophysics Data System (ADS)

    Booth-Rea, Guillermo; Ranero, Cesar R.; Grevemer, Ingo

    2016-04-01

    The Mediterranean Sea desiccated ~5.96 million years ago when it became isolated from the world oceans during the Messinian salinity crisis. This event permitted the exchange of terrestrial biota between Africa and Iberia contributing to the present rich biodiversity of the Mediterranean region. The cause chocking the Mediterranean has been proposed to be tectonic uplift and dynamic topography but the driving mechanism still remains debated. We present a new wide-angle seismic profile that provides a detailed image of the thickness and seismic velocity distribution of the crust in the eastern Alboran basin. The velocity model shows a characteristic structure of a subduction-related volcanic arc with a high-velocity lower crust and a 16-18 km total-thickness igneous crust that magmatic accreted mostly between ~10-6 Ma across the eastern Alboran basin. Estimation of the isostatically corrected depth of the arc crust taking into account the original thermal structure and sediment-loading subsidence since 6 Ma places a large area of the eastern Alboran basin above sea level at the time. This estimation is supported by geophysical data showing subaereal erosional unconformities for that time. This model may explain several up-to-now-disputed features of the Messinian salinity crisis, including: the progressive isolation of the Mediterranean since 7.1 Ma with the disappearance of open marine taxa, the existence of evaporites mostly to the east of the volcanic arc, the evidence that the Gibraltar straits were not a land bridge offered by continuous Messinian open marine sediments at ODP site 976 in the western Alboran basin, the importance of southeastern Iberia and North Africa as centres of biota diversification since before the salinity crisis, and patterns of speciation irradiating from SE Iberia and the eastern Rif in some taxons.

  16. Seafloor morphology related to recent tectonics in the Alboran Sea Basin

    NASA Astrophysics Data System (ADS)

    Vázquez, Juan-Tomás; Estrada, Ferran; Vegas, Ramon; Ercilla, Gemma; Medialdea, Teresa; d'Acremont, Elia; Alonso, Belen; Fernández-Salas, Luis-Miguel; Gómez-Ballesteros, María; Somoza, Luis; Bárcenas, Patricia; Palomino, Desirée; Gorini, Christian

    2014-05-01

    A detailed geomorphological study of the northern part of the Alboran Sea Basin has been realized based on the combined analysis of multibeam swath bathymetric data and medium to very high resolution seismic profiles (singled Sparker, Airgun, TOPAS and Atlas PARASOUND P35). This has enabled us to define several tectonic-related seafloor features and their role in the recent tectonics. The observed morpho-tectonic features correspond to: i) lineal scarps with a wide range of dimensions and following several trends ,WNW-ESE, NE-SW, NNE-SSW and N-S; ii) NE-SW to NNE-SSW-oriented compressive ridges; iii) ENE-WSW to NE-SW-striking antiforms; iv) NNE-SSW-oriented lineal depressions; v) rhomb-shaped depressions; vi) lineal valleys, canyons and gullies with WNW-ESE, and N-S orientations; and vii) N-S directed dissected valleys, canyons and gullies. Three families of faults and related folds, with NE-SW, WNW-ESE and NNE-SSW to N-S have been interpreted within this geomorphological scheme. The NE-SW family corresponds to: a) major scarps in both flanks of the Alboran Ridge and b) the offshore prolongation of La Serrata Fault, and both have been considered as a set of sinistral strike-slip faults. To this family, some compressive ridges, antiforms and occasionally reverse faults have been correlated. The WNW-ESE family corresponds to a set of faulted valleys (occasionally with rhomb-shaped depressions), fault scarps and linear inflection points occurring in the northern Alboran margin and the Yusuf-Habibas corridor. This family has been interpreted as transtensive dextral strike-slip faults. The NNE-SSW to N-S family corresponds to a penetrative system of linear fault scarps and tectonic depressions that cross-cut the Alboran Ridge and the Djibouti-Motril marginal plateau. This family can be considered as more recent since it offsets the other two families and shows a minor importance with regard to the main reliefs. This communication is a contribution to the Spanish R + D

  17. Architectures of the Moroccan continental shelf of the Alboran Sea: insights from high-resolution bathymetry and seismic data.

    NASA Astrophysics Data System (ADS)

    Lafosse, Manfred; Gorini, Christian; Leroy, Pascal; d'Acremont, Elia; Rabineau, Marina; Ercilla, Gemma; Alonso, Belén; Ammar, Abdellah

    2016-04-01

    The MARLBORO and the SARAS oceanographic surveys have explored the continental shelf in the vicinity of the transtensive Nekor basin (South Alboran Sea, Western Mediterranean) and over three submarine highs located at several tens of kilometers from the shelf. Those surveys have produced high-resolution (≤29m²/pixel) bathymetry maps. Simultaneously, seismic SPARKER and TOPAS profiles were recorded. To quantify and understand Quaternary vertical motions of this tectonically active area, we searched for morphological and sedimentary paleobathymetric or paleo-elevations markers. Shelf-edge wedges associated marine terraces and paleo-shorelines have been identified on the bathymetry and on seismic cross-sections. These features reflect the trends of long term accommodation variations. Along the Moroccan continental shelf the lateral changes of shelf-edges geometries and the spatial distribution of marine landforms (sedimentary marine terraces, sediment wave fields, marine incisions) reflect the interaction between sea level changes and spatial variations of subsidence rates. Positions of paleo-shorelines identified in the studied area have been correlated with the relative sea-level curve (Rohling et al., 2014). Several still stands or slow stands periods have been recognized between -130-125m, -100-110m and -85-80m. The astronomical forcing controls the architecture of Mediterranean continental shelves. Marine landforms distribution also reveals the way sea level changed since the LGM. The comparison with observations on other western Mediterranean margins (e.g. the Gulf of Lion, the Ionian-Calabrian shelf) allowed a first order access to vertical motion rates.

  18. Highly diverse molluscan assemblages of Posidonia oceanica meadows in northwestern Alboran Sea (W Mediterranean): Seasonal dynamics and environmental drivers

    NASA Astrophysics Data System (ADS)

    Urra, Javier; Mateo Ramírez, Ángel; Marina, Pablo; Salas, Carmen; Gofas, Serge; Rueda, José L.

    2013-01-01

    The seasonal dynamics of the molluscan fauna associated with the westernmost populations of the Mediterranean seagrass Posidonia oceanica, has been studied throughout an annual cycle in the northwestern coasts of the Alboran Sea. Samples were collected seasonally (5 replicated per season) using a non-destructive sampling technique (airlift sampler) on quadrats of 50 × 50 cm at 2 sites located 7 km apart. Several environmental variables from the water column (temperature, chlorophyll a), the sediment (percentage of organic matter) and the seagrass meadows (shoot density, leaf height and width, number of leaves per shoot) were also measured in order to elucidate their relationships with the dynamics of the molluscan assemblages. In these meadows, a total of 17,416 individuals of molluscs were collected, belonging to 71 families and 171 species, being Rissoidae, Pyramidellidae and Trochidae the best-represented families, and Mytilidae, Nassaridae and Trochidae the dominant ones in terms of abundance. The assemblages were dominated by micro-algal grazers, filter feeders and ectoparasites (including those feeding on sessile preys). The species richness and the abundance displayed significant maximum values in summer, whereas evenness and diversity displayed maximum values in spring, being significant for the evenness. Both abundance and species richness values were positively correlated to seawater temperature and percentage organic matter, only for the latter, and negatively to leaf width. Significant seasonal groupings were obtained with multivariate analyses (MDS, Cluster, ANOSIM) using qualitative and quantitative data that could be mainly related to biological aspects (i.e. recruitment) of single species. The molluscan assemblages are influenced by the biogeographical location of the area (Alboran Sea), reflected in the absence or scarcity of most Mediterranean species strictly associated with P. oceanica (e.g. Tricolia speciosa, Rissoa ventricosa) and by the

  19. Consequences of a future climatic scenario for the anchovy fishery in the Alboran Sea (SW Mediterranean): A modeling study

    NASA Astrophysics Data System (ADS)

    Macías, D.; Castilla-Espino, D.; García-del-Hoyo, J. J.; Navarro, G.; Catalán, I. A.; Renault, L.; Ruiz, J.

    2014-07-01

    The Alboran basin is one of the most productive areas of the Mediterranean Sea and supports an anchovy fishery with a history of remarkably variable landings. Past and present anchovy recruitment levels are highly sensitive to changes in the strength and direction of the incoming jet of Atlantic waters, which modulate the hydrographic features of the basin. Here, we analyze plausible consequences for the anchovy fisheries in the region based on a projected physical scenario for the end of the century obtained using a coupled hydrological-biogeochemical model. Our model predicts a substantial increase in horizontal water velocity and a negligible change in the associated biological production, which likely indicates reductions in anchovy stock, catches and revenues. Alternative policies are analyzed here for the economic scenario that is expected to emerge under future conditions of oceanographic features, pelagic ecosystem dynamics and anchovy landings in the Alboran Sea.

  20. New insights from seismic tomography on the complex geodynamic evolution of two adjacent domains: Gulf of Cadiz and Alboran Sea

    NASA Astrophysics Data System (ADS)

    Monna, S.; Cimini, G. B.; Montuori, C.; Matias, L.; Geissler, W. H.; Favali, P.

    2013-04-01

    In this study, we present a three-dimensional P wave upper-mantle tomography model of the southwest Iberian margin and Alboran Sea based on teleseismic arrival times recorded by Iberian and Moroccan land stations and by a seafloor network deployed for 1 year in the Gulf of Cadiz area during the European Commission Integrated observations from NEAR shore sourcES of Tsunamis: towards an early warning system (EC NEAREST) project. The three-dimensional model was computed down to 600 km depth. The tomographic images exhibit significant velocity contrasts, as large as 3%, confirming the complex evolution of this plate boundary region. Prominent high-velocity anomalies are found beneath Betics-Alboran Sea, off-shore southwest Portugal, and north Portugal, at sublithospheric depths. The transition zones between high- and low-velocity anomalies in southwest and south Iberia are associated to the contact of oceanic and continental lithosphere. The fast structure below the Alboran Sea-Granada area depicts an L-shaped body steeply dipping from the uppermost mantle to the transition zone where it becomes less curved. This anomaly is consistent with the results of previous tomographic investigations and recent geophysical data such as stress distribution, GPS measurements of plate motion, and anisotropy patterns. In the Atlantic domain, under the Horseshoe Abyssal Plain, the main feature is a high-velocity zone found at uppermost mantle depths. This feature appears laterally separated from the positive anomaly recovered in the Alboran domain by the interposition of low-velocity zones which characterize the lithosphere beneath the southwest Iberian peninsula margin, suggesting that there is no continuity between the high-velocity anomalies of the two domains west and east of the Gibraltar Strait.

  1. Characterization of the sub-mesoscale energy cascade in the Alboran Sea thermocline from spectral analysis of multichannel seismic data

    NASA Astrophysics Data System (ADS)

    Sallares, Valenti; Moncada, Jhon F.; Biescas, Berta; Klaeschen, Dirk

    2016-04-01

    Large-scale ocean dynamics is linked to small-scale mixing by means of turbulence, which enables the exchange of kinetic energy across the scales. At equilibrium, the energy flux that is injected at the production range must be balanced by mixing at the dissipation range. While the physics of the different ranges is now well established, an observational gap exists at the 103-101 m scale that prevents to characterize the transition from the anisotropic internal wave motions to isotropic turbulence. This lack of empirical evidence limits our understanding of the mechanisms governing the downward energy cascade, hampering the predictive capability of ocean circulation models. Here we show that this observational gap can be covered using high-resolution multichannel seismic (HR-MCS) data. Spectral analysis of acoustic reflectors imaged in the Alboran Sea (Western Mediterranean) thermocline evidences that this transition is caused by shear instabilities. In particular, we show that the averaged horizontal wavenumber (kx) spectra of the reflector's vertical displacements display three subranges that reproduce theoretical spectral slopes of internal waves [λx>100 m, with λx=kx‑1], Kelvin-Helmholtz (KH)-type shear instabilities[100 m> λx>33 m], and turbulence[λx<33 m]. The presence of the transitional subrange in the averaged spectrum indicates that the whole chain of events is occurring continuously and simultaneously in the surveyed area. The availability of a system providing observational data at the appropriate scales opens new perspectives to incorporate small-scale mixing in predictive ocean modelling research.

  2. ALBOREX: an intensive multi-platform and multidisciplinary experiment in the Alboran Sea

    NASA Astrophysics Data System (ADS)

    Ruiz, Simón; Pascual, Ananda; Allen, John; Olita, Antonio; Tovar, Antonio; Oguz, Temel; Mahadevan, Amala; Poulain, Pierre; Tintoré, Joaquín

    2015-04-01

    An intensive multi-platform and multidisciplinary experiment was completed in May 2014 as part of PERSEUS EU Project. 25 drifters, 2 gliders, 3 Argo floats and one ship were dedicated to sample an area of about 50x50 km in the eastern Alboran Sea during one week. The experiment, which also includes 66 CTD stations and 500 water samples (salinity, chlorophyll and nutrients), was designed to capture the intense but transient vertical exchanges associated with mesoscale and submesoscale features. The vertical motion associated with mesoscale and submesoscale features such as ocean eddies, filaments and fronts plays a major role in determining ocean productivity, due to the exchange of properties between the surface and the ocean interior. Understanding the relationship between these physical and biological processes is crucial for predicting the marine ecosystems response to changes in the climate system and to sustainable marine resource management. However, to understand the links between mesoscale and submesoscale features and ecosystem responses, it is necessary to collect data at a range of temporal and spatial scales, and then combine these data with coupled physical and biochemical models. Data from thermosalinograph revealed a sharp surface salinity front with values ranging from 36.6 (Atlantic Waters) to 38.2 (Mediterranean Waters) in conjunction with a filament in temperature. Drifters followed a massive anticyclonic gyre. Near real time data from ADCP showed coherent patterns with currents up to 1m/s. Gliders detected a subduction of chlorophyll located in areas adjacent to the front. We also present results on the horizontal strain rate, relative vorticity and quasi-geostrophic vertical motion to understand the dynamics of this intense ocean front.

  3. Spatial patterns of macrophyte composition and landscape along the rocky shores of the Mediterranean-Atlantic transition region (northern Alboran Sea)

    NASA Astrophysics Data System (ADS)

    Bermejo, Ricardo; Ramírez-Romero, Eduardo; Vergara, Juan J.; Hernández, Ignacio

    2015-03-01

    The Alboran Sea is the westernmost ecoregion of the Mediterranean Sea. It is located in the vicinity of Strait of Gibraltar, the only natural connection of the Mediterranean Sea with global circulation. This ecoregion presents steep and highly variable environmental gradients, thus acting as a natural filter for Mediterranean and Atlantic species. This study aimed to analyse spatial patterns of littoral and upper sublittoral communities and their relationship with oceanographic conditions and coastal geomorphology, and to quantify littoral and upper sublittoral rocky shore communities at landscape scale. The results suggest that oceanographic conditions are the main factor to explain landscape patterns along the studied area, while geomorphological features should be related with local-scale variability. In this sense, three biogeographic subregions, matching with oceanographic patterns, were identified: western, central and eastern. These subregions showed significant differences in the structure and the composition of the littoral and upper sublittoral community, which can be explained by regional oceanographic dynamics. Posidonia oceanica, Cystoseira ericaefolia group and Mytilus spp. were the species that most contributed to landscape dissimilarity between the three subregions identified. The central oceanographic region, where the environmental conditions were more variable, showed the poorer and less differentiated flora, suggesting the existence of a divergent boundary between the Atlantic and the Mediterranean Sea.

  4. Microfossils, a Key to Unravel Cold-Water Carbonate Mound Evolution through Time: Evidence from the Eastern Alboran Sea.

    PubMed

    Stalder, Claudio; Vertino, Agostina; Rosso, Antonietta; Rüggeberg, Andres; Pirkenseer, Claudius; Spangenberg, Jorge E; Spezzaferri, Silvia; Camozzi, Osvaldo; Rappo, Sacha; Hajdas, Irka

    2015-01-01

    Cold-water coral (CWC) ecosystems occur worldwide and play a major role in the ocean's carbonate budget and atmospheric CO2 balance since the Danian (~65 m.y. ago). However their temporal and spatial evolution against climatic and oceanographic variability is still unclear. For the first time, we combine the main macrofaunal components of a sediment core from a CWC mound of the Melilla Mounds Field in the Eastern Alboran Sea with the associated microfauna and we highlight the importance of foraminifera and ostracods as indicators of CWC mound evolution in the paleorecord. Abundances of macrofauna along the core reveal alternating periods dominated by distinct CWC taxa (mostly Lophelia pertusa, Madrepora oculata) that correspond to major shifts in foraminiferal and ostracod assemblages. The period dominated by M. oculata coincides with a period characterized by increased export of refractory organic matter to the seafloor and rather unstable oceanographic conditions at the benthic boundary layer with periodically decreased water energy and oxygenation, variable bottom water temperature/density and increased sediment flow. The microfaunal and geochemical data strongly suggest that M. oculata and in particular Dendrophylliidae show a higher tolerance to environmental changes than L. pertusa. Finally, we show evidence for sustained CWC growth during the Alleröd-Younger-Dryas in the Eastern Alboran Sea and that this period corresponds to stable benthic conditions with cold/dense and well oxygenated bottom waters, high fluxes of labile organic matter and relatively strong bottom currents. PMID:26447699

  5. Microfossils, a Key to Unravel Cold-Water Carbonate Mound Evolution through Time: Evidence from the Eastern Alboran Sea

    PubMed Central

    Stalder, Claudio; Vertino, Agostina; Rosso, Antonietta; Rüggeberg, Andres; Pirkenseer, Claudius; Spangenberg, Jorge E.; Spezzaferri, Silvia; Camozzi, Osvaldo; Rappo, Sacha; Hajdas, Irka

    2015-01-01

    Cold-water coral (CWC) ecosystems occur worldwide and play a major role in the ocean's carbonate budget and atmospheric CO2 balance since the Danian (~65 m.y. ago). However their temporal and spatial evolution against climatic and oceanographic variability is still unclear. For the first time, we combine the main macrofaunal components of a sediment core from a CWC mound of the Melilla Mounds Field in the Eastern Alboran Sea with the associated microfauna and we highlight the importance of foraminifera and ostracods as indicators of CWC mound evolution in the paleorecord. Abundances of macrofauna along the core reveal alternating periods dominated by distinct CWC taxa (mostly Lophelia pertusa, Madrepora oculata) that correspond to major shifts in foraminiferal and ostracod assemblages. The period dominated by M. oculata coincides with a period characterized by increased export of refractory organic matter to the seafloor and rather unstable oceanographic conditions at the benthic boundary layer with periodically decreased water energy and oxygenation, variable bottom water temperature/density and increased sediment flow. The microfaunal and geochemical data strongly suggest that M. oculata and in particular Dendrophylliidae show a higher tolerance to environmental changes than L. pertusa. Finally, we show evidence for sustained CWC growth during the Alleröd-Younger-Dryas in the Eastern Alboran Sea and that this period corresponds to stable benthic conditions with cold/dense and well oxygenated bottom waters, high fluxes of labile organic matter and relatively strong bottom currents PMID:26447699

  6. Geochemical proxies for reconstructing climate variability in marginal basins: the Alboran Sea record

    NASA Astrophysics Data System (ADS)

    Martinez-Ruiz, Francisca; Kastner, Miriam; Gallego-Torres, David; Rodrigo-Gámiz, Marta; Nieto-Moreno, Vanesa; Jiménez-Espejo, Francisco J.; Ortega-Huertas, Miguel

    2014-05-01

    High sedimentation rate sediment sections in the Alboran Sea basin (westernmost Mediterranean) have provided excellent paleoarchives for reconstructing past climate variability. The following diverse proxies have been used for such reconstruction, molecular biomarkers, stable and radiogenic isotopes, microfossil assemblages, sediment grain size, and mineral and chemical composition of marine sediments. The elemental ratios have revealed to be reliable paleoclimate proxies. Al-normalized concentrations of detrital elements have allowed to characterize the terrigenous inputs into this basin. Ti/Al, Zr/Al and Si/Al ratios have served as proxies for eolian dust input, and Mg/Al, K/Al and Rb/Al ratios have provided information on fluvial contribution. An in-depth interpretation of these terrigenous element proxies requires knowledge of the mineral composition. Redox sensitive elements have also provided a reliable reconstruction of oxygen conditions at the time of deposition, though these elements are particularly susceptible to diagenetic remobilization, and certain elements, such as U, may also be linked to organic matter, which affects bulk U concentrations. Regarding productivity, even though most of the paleoproductivity reconstructions are based on Ba proxies, the biogeochemistry of Ba is not fully understood and the mechanisms for barite precipitation in the water column are not yet known. Over the past 20,000 cal yr BP, ratios mirroring eolian input indicate a major input of dust from the end of the Last Glacial Maximum to the Oldest Dryas. Mg/Al, K/Al and Rb/Al ratios record humid conditions during the subsequent Bölling-Alleröd warm period, further supported by the decrease in the Zr/Al ratio. These ratios have also allowed a detailed reconstruction of paleoclimate conditions during the Younger Dryas and the Holocene. Ratios of redox sensitive elements such as U/Th, Zn/Al, Cu/Al, and V/Al ratios also show significant fluctuations in oxygen conditions over

  7. Seasonal and inter-annual changes in the planktonic communities of the northwest Alboran Sea (Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Mercado, Jesús M.; Cortés, Dolores; García, Alberto; Ramírez, Teodoro

    2007-08-01

    The response of the northwestern Alboran Sea pelagic ecosystem to temporal changes in hydrological conditions has been examined for the time period of 1992-2002. In addition, the bottom-up linkages between the lower trophic levels and the growth and nutritional status of sardine larvae were examined using quarterly data from 1992 to 2002 within the frame of the monitoring Project ECOMALAGA. The study area was characterised by the almost permanent presence of an upwelling which was intensified in the spring period. Consequently, an annual peak of nutrients was usually found during this season when the nitrate concentration averaged 1.35 μM. Accordingly, chlorophyll- a concentration and cell abundance of micro- plus nano-phytoplankton increased in that season (1.51 μg L -1 and 446 cell mL -1 compared to 0.85 μg L -1 and 225 cell mL -1 obtained from summer to fall). Despite these seasonal changes, the analysis of the taxonomic composition of the phytoplankton communities did not reveal a clear annual succession pattern. Contrastingly, peaks of zooplankton abundance were obtained in summer (1964 ind m -3) due to the increased presence of brachiopods with respect to copepods (which dominated from fall to spring). Significant inter-annual changes were obtained in the phytoplankton and zooplankton communities. Thus, dinoflagellate and coccolitophorid abundances relative to diatom abundances tended to increase from 1997 to 2002. This trend matched the progressive reduction of the upwelling intensity. These inter-annual changes significantly affected the larval growth of Sardine pilchardus and their nutritional condition, as higher growth rates in terms of body length coupled to higher somatic mass increases (expressed by DNA content) occurred in spring, matching with the higher chlorophyll- a concentration. Furthermore, the highest larval growth was obtained in 2001, coinciding with the change observed in the composition of phytoplankton community.

  8. The electrical Lithosphere of the Alboran Domain

    NASA Astrophysics Data System (ADS)

    Garcia, X. A.; Evans, R. L.; Elsenbeck, J.; Jegen, M. D.; Matsuno, T.

    2011-12-01

    On the Western edge of the Mediterranean, the slow convergence of the Iberian and African plates is marked by very intricate tectonic activity, marked by a combination of small-scale subduction and sub-lithospheric downwelling. Delamination or convective instability has also been proposed to have occurred beneath this domain during the past 25 My. And different geodynamic models have been proposed to explain the lithospheric structure of the arc-shaped belt (Betic and Rif orogenies) and the opening of the Alboran Basin. As part of several international projects carried out in this area, magnetotelluric (MT) methods have been used to explore the crust and upper mantle. The measurements of mantle electrical conductivity are a well known complement to measurements of seismic velocity. Conductivity is sensitive to temperature, composition and hydration of the mantle, and therefore MT is widely used to provide constraints on mantle processes. We present results of electromagnetic studies in the Western Mediterranean, focusing specially in the recently work on the Alboran sea as part of a marine MT survey. Land MT studies have already imaged an area of low resistivity coincident with an area of low velocities without earthquake hypocenters, interpreted as asthenospheric material intruded by the lateral lithospheric tearing and breaking-off of the east-directed subducting Ligurian slab under the Alboran Domain. The model suggests that the most likely scenario for the opening of the Alboran Basin is related to the westward rollback of the Ligurian subducting slab. The marine data show complex MT response functions with strong distortion due to seafloor topography and coast effect, suggesting a fairly resistive lithosphere beneath the seafloor.

  9. Crustal and upper mantle shear velocities of Iberia, the Alboran Sea, and North Africa from ambient noise and ballistic finite-frequency Rayleigh wave tomography

    NASA Astrophysics Data System (ADS)

    Palomeras, I.; Villasenor, A.; Thurner, S.; Levander, A.; Gallart, J.; mimoun, H.

    2013-12-01

    The complex Mesozoic-Cenozoic Alpine deformation in the western Mediterranean extends from the Pyrenees in northern Spain to the Atlas Mountains in southern Morocco. The Iberian plate was accreted to the European plate in late Cretaceous, resulting in the formation of the Pyrenees. Cenozoic African-European convergence resulted in subduction of the Tethys oceanic plate beneath Europe. Rapid Oligocene slab rollback from eastern Iberia spread eastward and southward, with the trench breaking into three segments by the time it reached the African coast. One trench segment moved southwestward and westward creating the Alboran Sea, floored by highly extended continental crust, and building the encircling Betics Rif mountains comprising the Gibraltar arc, and the Atlas mountains, which formed as the inversion of a Jurassic rift. A number of recent experiments have instrumented this region with broad-band arrays (the US PICASSO array, Spanish IberArray and Siberia arrays, the University of Munster array), which, including the Spanish, Portuguese, and Moroccan permanent networks, provide a combined array of 350 stations having an average interstation spacing of ~60 km. Taking advantage of this dense deployment, we have calculated the Rayleigh waves phase velocities from ambient noise for short periods (4 s to 40 s) and teleseismic events for longer periods (20 s to 167 s). Approximately 50,000 stations pairs were used to measure the phase velocity from ambient noise and more than 160 teleseismic events to measure phase velocity for longer periods. The inversion of the phase velocity dispersion curves provides a 3D shear velocity for the crust and uppermost mantle. Our results show differences between the various tectonic regions that extend to upper mantle depths (~200 km). In Iberia we obtain, on average, higher upper mantle shear velocities in the western Variscan region than in the younger eastern part. We map high upper mantle velocities (>4.6 km/s) beneath the

  10. Tectono-sedimentary evolution of the peripheral basins of the Alboran Sea in the arc of Gibraltar during the latest Messinian-Pliocene

    NASA Astrophysics Data System (ADS)

    Guerra-Merchán, Antonio; Serrano, Francisco; Hlila, Rachid; El Kadiri, Khalil; Sanz de Galdeano, Carlos; Garcés, Miguel

    2014-07-01

    In the peripheral basins of the Alboran Sea, five stratigraphic units (latest Messinian-Pliocene) separated by discontinuities and representing transgressive-regressive cycles have been recognized. The first unit (LM) is latest Messinian in age and precisely characterizes the Lago-Mare event at the end of the Messinian Salinity Crisis, i.e. just before the opening of the Strait of Gibraltar at the beginning of the Pliocene. The three following units (Pl-1, Pl-2 and Pl-3) are Zanclean in age, whereas the last one (Pl-4) is Piacenzian. These four Pliocene units consist of alluvial, deltaic, and littoral deposits in the marginal areas, changing to open marine deposits with planktonic components in the basinal areas, although their extension varies in each basin. Regionally, these units do not necessarily stack in a single stratigraphic succession because of tectonics that controlled their hosting basins. Thus, the LM and Pl-1 units occur only in the Malaga and Estepona-Marbella basins, revealing that the onset of the sedimentation after the Messinian evaporitic stage and the Pliocene transgression was not a single and synchronous event in the western Alboran Sea. Moreover, the Pl-3 and Pl-4 units do not appear in all basins, so that the subsequent continentalization process of these Alboran peripheral areas during the Pliocene was also diachronous. The sedimentary evolution of the peripheral basins was controlled mainly by tectonics. During the latest Messinian-early Pliocene, the sedimentation took place in a context marked by a NNW-SSE compression and ENE-WSW perpendicular tension. The onset of the sedimentation (LM and Pl-1 units) could be linked to preexisting E-W faults that mark part of the borders of the Malaga basin and the Estepona-Marbella sector. During the deposition of the Pl-2 unit, the movements of E-W, NW-SE, and NE-SW normal faults determined a continuous subsidence in several basins, resulting in the accumulation of thick clastic marine sequences (i

  11. Tectono-sedimentary evolution of the peripheral basins of the Alboran Sea in the arc of Gibraltar during the latest Messinian-Pliocene

    NASA Astrophysics Data System (ADS)

    Guerra-Merchán, Antonio; Serrano, Francisco; Hlila, Rachid; El Kadiri, Khalil; Sanz de Galdeano, Carlos; Garcés, Miguel

    2014-07-01

    In the peripheral basins of the Alboran Sea, five stratigraphic units (latest Messinian-Pliocene) separated by discontinuities and representing transgressive-regressive cycles have been recognized. The first unit (LM) is latest Messinian in age and precisely characterizes the Lago-Mare event at the end of the Messinian Salinity Crisis, i.e. just before the opening of the Strait of Gibraltar at the beginning of the Pliocene. The three following units (Pl-1, Pl-2 and Pl-3) are Zanclean in age, whereas the last one (Pl-4) is Piacenzian. These four Pliocene units consist of alluvial, deltaic, and littoral deposits in the marginal areas, changing to open marine deposits with planktonic components in the basinal areas, although their extension varies in each basin. Regionally, these units do not necessarily stack in a single stratigraphic succession because of tectonics that controlled their hosting basins. Thus, the LM and Pl-1 units occur only in the Malaga and Estepona-Marbella basins, revealing that the onset of the sedimentation after the Messinian evaporitic stage and the Pliocene transgression was not a single and synchronous event in the western Alboran Sea. Moreover, the Pl-3 and Pl-4 units do not appear in all basins, so that the subsequent continentalization process of these Alboran peripheral areas during the Pliocene was also diachronous. The sedimentary evolution of the peripheral basins was controlled mainly by tectonics. During the latest Messinian-early Pliocene, the sedimentation took place in a context marked by a NNW-SSE compression and ENE-WSW perpendicular tension. The onset of the sedimentation (LM and Pl-1 units) could be linked to preexisting E-W faults that mark part of the borders of the Malaga basin and the Estepona-Marbella sector. During the deposition of the Pl-2 unit, the movements of E-W, NW-SE, and NE-SW normal faults determined a continuous subsidence in several basins, resulting in the accumulation of thick clastic marine sequences (i

  12. Atmospheric forcing and Sea Surface Temperature response in the Gulf of Cadiz-Alboran Sea system in a 20 years simulation

    NASA Astrophysics Data System (ADS)

    Boutov, D.; Peliz, A.

    2012-04-01

    In the frame of MedEX ("Inter-basin exchange in the changing Mediterranean Sea") Project a 20 years (1989-2008) simulation at 2km resolution covering Gulf of Cadiz and Alboran Sea, forced by 9 km winds (WRF downscaling of ERA-Interim reanalysis), is analyzed and compared with observations. Statistical methods, EOF techniques and two harmonic (including annual and semi-annual frequencies) data fit were performed for the analysis. Modeled SST fields are also compared with long-term (1996-2008) in-situ buoy observations provided by Puertos del Estado (Spain) and satellite derived Pathfinder SST database. Model SSTs generally follow observations data at annual and inter-annual scales with a global error not exceeding 0.17°C (model warmer than SST). No significant warming tendency was observed in both basins during the 20 years and the Interanual variability dominates, with the series showing a cooling period from 1991 to 1993 followed by a warming period started from 1994. In particular we show that SST cooling observed in the early 1990's in the Gulf of Cadiz - Alboran system is associated with the 1991 catastrophic eruption of Pinatubo volcano (Philippines).

  13. The seasonal cycle of the Atlantic Jet dynamics in the Alboran Sea: direct atmospheric forcing versus Mediterranean thermohaline circulation

    NASA Astrophysics Data System (ADS)

    Macias, Diego; Garcia-Gorriz, Elisa; Stips, Adolf

    2016-02-01

    The Atlantic Jet (AJ) is the inflow of Atlantic surface waters into the Mediterranean Sea. This geostrophically adjusted jet fluctuates in a wide range of temporal scales from tidal to subinertial, seasonal, and interannual modifying its velocity and direction within the Alboran Sea. At seasonal scale, a clearly defined cycle has been previously described, with the jet being stronger and flowing towards the northeast during the first half of the year and weakening and flowing more southwardly towards the end of the year. Different hypothesis have been proposed to explain this fluctuation pattern but, up to now, no quantitative assessment of the importance of the different forcings for this seasonality has been provided. Here, we use a 3D hydrodynamic model of the entire Mediterranean Sea forced at the surface with realistic atmospheric conditions to study and quantify the importance of the different meteorological forcings on the velocity and direction of the AJ at seasonal time scale. We find that the direct effects of local zonal wind variations are much more important to explain extreme collapse events when the jet dramatically veers southward than to the seasonal cycle itself while sea level pressure variations over the Mediterranean seem to have very little direct effect on the AJ behavior at monthly and longer time scales. Further model results indicate that the annual cycle of the thermohaline circulation is the main driver of the seasonality of the AJ dynamics in the model simulations. The annual cycles in local wind forcing and SLP variations over the Mediterranean have no causal relationship with the AJ seasonality.

  14. Controls of plankton production by pelagic fish predation and resource availability in the Alboran and Balearic Seas

    NASA Astrophysics Data System (ADS)

    Oguz, Temel; Macias, Diego; Renault, Lionel; Ruiz, Javier; Tintore, Joaquin

    2013-05-01

    A one-dimensional coupled physical and intermediate-complexity biochemical model comprising large and small phytoplankton and zooplankton groups, particulate organic nitrogen, ammonium and nitrate was developed to study the physical-biogeochemical interactions and parameters that control plankton production in the Alboran and Balearic Sea ecosystems. The model findings suggest that pelagic fish predation and resource availability through lateral and vertical nutrient inputs jointly characterize the plankton community structures. In agreement with previous observations, a typical annual plankton structure of the mesotrophic systems involves a vertically homogeneous biomass of large groups of phytoplankton and zooplankton within the upper 50-to-100 m layer from mid-November to April and a subsurface biomass accumulation distributed roughly within 25-75 m depths in the following months. Their light and temperature limitations constrain the smaller groups into the thermocline zone (25-50 m) during late spring and summer. These obtained results were dependent on the zooplankton actively switching between preys (i.e., the food preference coefficients dependent on prey biomass). In the case of no switching, spurious dynamic equilibrium solutions may arise in the case of a constant and weak fish predation rate and using the quadratic predation formulation. The choice of a Holling Type II (i.e., hyperbolic) predation function may, however avoid ambiguous representation of the annual plankton structure in the case of a constant food preference choice under relatively weak predation pressures.

  15. Deep Chlorophyll Maximum distribution in the Alboran sea and its relationship with mesoscale and frontal features through syncronous glider observations.

    NASA Astrophysics Data System (ADS)

    Olita, Antonio; Ribotti, Alberto; Ruiz, Simon; Pascual, Ananda

    2015-04-01

    May 25 2014, two gliders were launched in the framework of the multiplatform and multidisciplinary experiment in the Alboran sea named ALBOREX (a PERSEUS project sampling) and of the JERICO TNA FRIPP project. The two instruments glided for 6 days, during which ADCP, ship based CTD, ARGO floats and surface drifters also sampled surface to deep waters allowing, togheter with bottle water samples, to collect a comprehensive dataset of oceanographic multidisciplinary quasi-synoptic data at (sub-)mesoscale. This preliminary work presents the results related to the two glider launched at approximatively 20 km each other. The two gliders intercepted in their pathway a frontal structure belonging to the northern margin of a quite large and strong anticyclonic structure originating by the meandering of Atlantic Waters entering in Mediterranean through Gibraltar. The vertical structure of Chlorophyll-a (as derived by fluorimeter measurements) shows the area of subsidence across the front and the deepening of isolines in the eddy interior. The analysis of the relatively low-cost glider data, combined with synoptic satellite measurements, shed light on the dynamics determining the re-distribution of the phytoplanktonic biomass and provide pretious hints, combined with dissolved oxygen data also collected by the unmanned autonomous vehicles, about the influence of such dynamical features on Primary Production.

  16. Characterization of the submesoscale energy cascade in the Alboran Sea thermocline from spectral analysis of high-resolution MCS data

    NASA Astrophysics Data System (ADS)

    Sallares, Valenti; Mojica, Jhon F.; Biescas, Berta; Klaeschen, Dirk; Gràcia, Eulàlia

    2016-06-01

    Part of the kinetic energy that maintains ocean circulation cascades down to small scales until it is dissipated through mixing. While most steps of this downward energy cascade are well understood, an observational gap exists at horizontal scales of 103-101 m that prevents characterizing a key step in the chain: the transition from anisotropic internal wave motions to isotropic turbulence. Here we show that this observational gap can be covered using high-resolution multichannel seismic (HR-MCS) data. Spectral analysis of acoustic reflectors imaged in the Alboran Sea thermocline shows that this transition is likely caused by shear instabilities. In particular, we show that the averaged horizontal wave number spectra of the reflectors vertical displacements display three subranges that reproduce theoretical spectral slopes of internal waves (λx > 100 m), Kelvin-Helmholtz-type shear instabilities (100 m > λx > 33 m), and turbulence (λx < 33 m), indicating that the whole chain of events is occurring continuously and simultaneously in the surveyed area.

  17. Imaging the Alboran Domain from a marine MT survey

    NASA Astrophysics Data System (ADS)

    Garcia, X.; Evans, R.; Elsenbeck, J.; Jegen, M.

    2012-04-01

    On the Western edge of the Mediterranean, the slow convergence of the Iberian and African plates is marked by very intricate tectonic activity, marked by a combination of small-scale subduction and sub-lithospheric downwelling. Delamination or convective instability has also been proposed to have occurred beneath this domain during the past 25 My. And different geodynamic models have been proposed to explain the lithospheric structure of the arc-shaped belt (Betic and Rif orogenies) and the opening of the Alboran Basin. As part of several international projects carried out in this area, magnetotelluric (MT) methods have been used to explore the crust and upper mantle. The measurements of mantle electrical conductivity are a well known complement to measurements of seismic velocity. Conductivity is sensitive to temperature, composition and hydration of the mantle, and therefore MT is widely used to provide constraints on mantle processes. We present results of electromagnetic studies in the Western Mediterranean, focusing specially in the recently work on the Alboran sea as part of a marine MT survey. Land MT studies have already imaged an area of low resistivity coincident with an area of low velocities without earthquake hypocenters, interpreted as asthenospheric material intruded by the lateral lithospheric tearing and breaking-off of the east-directed subducting Ligurian slab under the Alboran Domain. The marine data show complex MT response functions with strong distortion due to seafloor topography and coast effect, suggesting a fairly resistive lithosphere beneath the seafloor. The marine MT data also shows an anomalous conductive slab towards the Eastern Alboran basin, suggesting a possible hydration of mantle material from an Eastward subducting slab. Both the land and marine MT data suggest that the most likely scenario for the opening of the Alboran Basin is related to the westward rollback of the Ligurian subducting slab.

  18. The Messinian erosional surface and early Pliocene reflooding in the Alboran Sea: New insights from the Boudinar basin, Morocco

    NASA Astrophysics Data System (ADS)

    Cornée, Jean-Jacques; Münch, Philippe; Achalhi, Mohammed; Merzeraud, Gilles; Azdimousa, Ali; Quillévéré, Frédéric; Melinte-Dobrinescu, Mihaela; Chaix, Christian; Moussa, Abdelkhalak Ben; Lofi, Johanna; Séranne, Michel; Moissette, Pierre

    2016-03-01

    New investigations in the Neogene Boudinar basin (Morocco) provide new information about the Messinian Salinity Crisis (MSC) and Zanclean reflooding in the southern part of the Alboran realm (westernmost Mediterranean). Based on a new field, sedimentological and palaeontological analyses, the age and the geometry of both the Messinian erosional surface (MES) and the overlying deposits have been determined. The MES is of late Messinian age and was emplaced in subaerial settings. In the Boudinar basin, a maximum of 200 m of Miocene sediments was eroded, including late Messinian gypsum blocks. The original geometry of the MES is preserved only when it is overlain by late Messinian continental deposits, conglomeratic alluvial fans or lacustrine marly sediments. These sediments are interpreted as indicators of the sea-level fall during the MSC. Elsewhere in the basin, the contact between late Messinian and early Pliocene deposits is a low-angle dipping, smooth surface that corresponds to the early Pliocene transgression surface that subsequently re-shaped the regressive MES. The early Pliocene deposits are characterized by: (i) their onlap onto either the basement of the Rif chain or the late Miocene deposits; (ii) lagoonal deposits at the base to offshore marls and sands at the top (earliest Pliocene; 5.33-5.04 Ma interval; foraminifer zone PL1); (iii) marine recovery occurring in the 5.32-5.26 Ma interval; and (iv) the change from lagoonal to offshore environments occurring within deposits tens of metres thick. This information indicates that at least the end of the reflooding period was progressive, not catastrophic as previously thought.

  19. Cold-water coral carbonate mounds and associated habitats of the Chella Seamount (Alboran Sea - SW Mediterranean)

    NASA Astrophysics Data System (ADS)

    Lo Iacono, C.; Bartolomé, R.; Gràcia, E.; Monteys, X.; Perea, H.; Gori, A.; Event-Shelf Team

    2009-04-01

    This study focuses on the characterization of cold-water carbonate mounds and of the associated habitats detected and mapped in the Chella Seamount, off the Almeria Margin, along the eastern Alboran Sea (SW Mediterranean). The study has been carried out by means of an integrated geophysical dataset, comprising large-scale sidescan sonar (TOBI), high resolution swath-bathymetry, TOPAS and Sparker high-resolution seismics. The acoustic dataset has been ground-truthed by images from an ROV and a deep-towed video-camera. Carbonate mounds range from 10 to 60 m in height and from 150 to 250 m in width, typically displaying a sub-circular shape. They are found within a depth range of 80-400 m and generally occur along the structural ridges of the Chella Seamount. Some of the mounds are distributed NW-SE and N-S, coinciding with the orientation of the active fault lineations observed North and West of the study area. On the other hand, the orientation of some other mounds suggests that the presence of strong bottom currents and reduced sedimentary fluxes are environmental factors suitable for their development. The images obtained from video inspections have been key for the characterization of the benthic communities and abundance of the species identified along the mounds. Video stills suggest that most of the mounds are in a "sub-fossil" stage and are mainly composed of patchy distributed Madrepora oculata and Lophelia pertusa. Additionally, other environments have been detected, in which sponges, boulders, coarse sands and bedforms prevail. Wide and dense patches of gorgonian (Callogorgia verticillata) have been observed along the top of the Chella Seamount. The integration of different marine geophysical methods supported by ground-truthing calibrations, allowed to recognize in detail the structural, sedimentary and hydrodynamic constrains suitable for the development of cold-water coral carbonate mounds in the Chella Seamount and to recognize and map some of the

  20. Spatial variability and response to anthropogenic pressures of assemblages dominated by a habitat forming seaweed sensitive to pollution (northern coast of Alboran Sea).

    PubMed

    Bermejo, Ricardo; de la Fuente, Gina; Ramírez-Romero, Eduardo; Vergara, Juan J; Hernández, Ignacio

    2016-04-15

    The Cystoseira ericaefolia group is conformed by three species: C. tamariscifolia, C. mediterranea and C. amentacea. These species are among the most important habitat forming species of the upper sublittoral rocky shores of the Mediterranean Sea and adjacent Atlantic coast. This species group is sensitive to human pressures and therefore is currently suffering important losses. This study aimed to assess the influence of anthropogenic pressures, oceanographic conditions and local spatial variability in assemblages dominated by C. ericaefolia in the Alboran Sea. The results showed the absence of significant effects of anthropogenic pressures or its interactions with environmental conditions in the Cystoseira assemblages. This fact was attributed to the high spatial variability, which is most probably masking the impact of anthropogenic pressures. The results also showed that most of the variability occurred on at local levels. A relevant spatial variability was observed at regional level, suggesting a key role of oceanographic features in these assemblages. PMID:26892204

  1. The last glacial-interglacial transition and dinoflagellate cysts in the western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Rouis-Zargouni, Imene; Turon, Jean-Louis; Londeix, Laurent; Kallel, Néjib; Essallami, Latifa

    2012-02-01

    Using the analysis of dinoflagellate cysts in three deep-sea sediments cores situated in the Sicilian-Tunisian Strait, in the Gulf of Lions and in the Alboran Sea, we reconstruct the paleoenvironmental changes that took place during the last glacial-interglacial transition in the western Mediterranean Sea. The development of the warm microflora Impagidinium aculeatum and especially Spiniferites mirabilis appears to be an important proxy for recognizing warm periods as the Bölling/Alleröd and the Early Holocene. Bitectatodinium tepikiense, Spiniferites elongatus and Nematosphaeropsis labyrinthus mark the end of the Heinrich event 1 and the Younger Dryas. This cold microfloral association confirms the drastic climate changes in the western Mediterranean Sea synchronous to the dry and cold climate which occurred in the South European margin. The dinocyst N. labyrinthus shows high percentages in all studied regions during the Younger Dryas. Its distribution reveals a significant increase from the South to the North of this basin during this cold brief event. Thus, we note that this species can be considered as a new eco-stratigraphical tracer of the Younger Dryas in the western Mediterranean Sea.

  2. Development of coccolithophore-based transfer functions in the western Mediterranean sea: a sea surface salinity reconstruction for the last 15.5 kyr

    NASA Astrophysics Data System (ADS)

    Ausín, B.; Hernández-Almeida, I.; Flores, J.-A.; Sierro, F.-J.; Grosjean, M.; Francés, G.; Alonso, B.

    2015-12-01

    A new data set of 88 marine surface sediment samples and related oceanic environmental variables (temperature, salinity, chlorophyll a, oxygen, etc.) was studied to quantify the relationship between assemblages of coccolithophore species and modern environmental conditions in the western Mediterranean Sea and the Atlantic Ocean, west of the Strait of Gibraltar. Multivariate statistical analyses revealed that coccolithophore species were primarily related to sea surface salinity (SSS), explaining an independent and significant proportion of variance in the coccolithophore data. A quantitative coccolithophore-based transfer function to estimate SSS was developed using the modern analog technique (MAT) and weighted-averaging partial least square regression (WA-PLS). The bootstrapped regression coefficient (R2boot) was 0.85MAT and 0.80WA-PLS, with a root-mean-square error of prediction (RMSEP) of 0.29MAT and 0.30WA-PLS (psu). The resulting transfer function was applied to fossil coccolithophore assemblages in the highly resolved (~ 65 years) sediment core CEUTA10PC08 from the Alboran Sea (western Mediterranean) in order to reconstruct SSS for the last 25 kyr. The reliability of the reconstruction was evaluated by assessing the degree of similarity between fossil and modern coccolithophore assemblages and by a comparison of reconstructions with fossil ordination scores. Analogs were poor for the stadials associated with Heinrich events 2 and 1 and part of the Last Glacial Maximum. Good analogs indicate a more reliable reconstruction of the SSS for the last 15.5 kyr. During this period, several millennial and centennial SSS changes were observed and associated with sea-level oscillations and variations in the Atlantic Water entering the Alboran.

  3. Assessment and intercomparison of numerical simulations in the Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Juza, Mélanie; Mourre, Baptiste; Renault, Lionel; Tintoré, Joaquin

    2014-05-01

    The Balearic Islands Coastal Observing and Forecasting System (SOCIB, www.socib.es) is developing high resolution numerical simulations (hindcasts and forecasts) in the Western Mediterranean Sea (WMOP). WMOP uses a regional configuration of the Regional Ocean Modelling System (ROMS, Shchepetkin and McWilliams, 2005) with a high spatial resolution of 1/50º (1.5-2km). Thus, theses simulations are able to reproduce mesoscale and in some cases sub-mesoscale features that are key in the Mediterranean Sea since they interact and modify the basin and sub-basin circulation. These simulations are initialized from and nested in either the Mediterranean Forecasting System (MFS, 1/16º) or Mercator-Océan simulations (MERCATOR, 1/12º). A repeated glider section in the Ibiza Channel, operated by SOCIB, has revealed significant differences between two WMOP simulations using either MFS or MERCATOR (hereafter WMOP-MFS and WMOP-MERC). In this study, MFS, MERCATOR, WMOP-MFS and WMOP-MERC are compared and evaluated using available multi-platform observations such as satellite products (Sea Level Anomaly, Sea Surface Temperature) and in situ measurements (temperature and salinity profiles from Argo floats, CTD, XBT, fixed moorings and gliders; velocity fields from HF radar and currentmeters). A quantitative comparison is necessary to evaluate the capacity of the simulations to reproduce observed ocean features, and to quantify the possible simulations biases. This will in turn allow to improve the simulations, so as to produce better ocean forecast systems, to study and better understand ocean processes and to address climate studies. Therefore, various statistical diagnostics have been developed to assess and intercompare the simulations at various spatial and temporal scales, in different sub-regions (Alboran Sea, Western and Eastern Algerian sub-basins, Balearic Sea, Gulf of Lion), in different dynamical zones (coastal areas, shelves and "open" sea), along key sections (Ibiza and

  4. 40Ar/ 39Ar dating of the pre-evaporitic Messinian marine sequences of the Melilla basin (Morocco): a proposal for some biosedimentary events as isochrons around the Alboran Sea

    NASA Astrophysics Data System (ADS)

    Roger, S.; Münch, Ph.; Cornée, J. J.; Saint Martin, J. P.; Féraud, G.; Pestrea, S.; Conesa, G.; Ben Moussa, A.

    2000-06-01

    In the Mediterranean region, the Melilla basin (NE Morocco) represents a key area that recorded biosedimentary events and environmental changes relative to the pre-evaporitic Messinian times. 40Ar/ 39Ar dating of volcanic tuffs interbedded all along the Melilla Messinian shelf carbonates and coeval basin deposits has been performed in order to date accurately three main pre-evaporitic biosedimentary events: the prograding bioclastic deposition and the oligospecific prograding Porites coral reef buildings with coeval Halimeda blooms, both within the platform, and the diatomite deposition basinward. The new age data allow a precise chronological framework to be established for the pre-evaporitic sequence of Melilla basin demonstrating that diatomitic deposits are coeval with both prograding bioclastic and reefal units. The prograding bioclastic carbonate unit related to boreal influences in coeval basinal diatomites, began at least at 6.73±0.02 Ma and ended at 6.46±0.03 Ma. The oligospecific prograding Porites coral-reefs and Halimeda beds and coeval warm-water diatomites began at least at 6.46±0.03 Ma. Previous 40Ar/ 39Ar ages indicate that they ended prior to 6.0±0.1 Ma. Both biosedimentological similarities and chronological accordance within several platforms and adjacent basins all around the Alboran Sea show that these main bioevents, dated in Melilla, are synchronous over the Alboran realm. This accurate time scale for these pre-evaporitic biosedimentary events (6.9-6.0 Ma) is in accordance with the most recent work on the latter period corresponding to the Messinian Salinity Crisis.

  5. Monitoring the mesoscale circulation of the Western Mediterranean Sea using SSS derived from SMOS

    NASA Astrophysics Data System (ADS)

    Olmedo, Estrella; Isern-Fontanet, Jordi; Turiel, Antonio; Portabella, Marcos; Ballabrera-Poy, Joaquim

    2016-04-01

    The circulation in the Mediterranean Sea is characterized by the inflow of fresh waters from the Atlantic Ocean through the Strait of Gibraltar. These waters, characterized by their lower salinity, create baroclinic instabilities that spawn eddies with sizes of the order of 100 km. These eddies have been widely analyzed using Sea Surface Temperature (SST) observations. Recent improvements in the Sea Surface Salinity (SSS) retrieval and bias correction methodologies applied to the Soil Moisture and Ocean Salinity (SMOS) satellite data have led, for the first time, to the generation of SSS maps that capture the signature of these structures. This opens the door for the generation of high spatial and temporal density maps in the Mediterranean, which can be used in a wide variety of oceanographic applications. In particular, the signature of the Alboran gyre and the eddy propagation across the Algerian coast are well reproduced, allowing for the first time to characterize the baroclinicity of the flow. The SMOS data are strongly affected by Radio Frequency Interference (RFI) and land-sea contamination in the Mediterranean Sea. Two important SSS retrieval algorithm improvements are proposed in this study. First, with more than six years of SMOS data acquisitions, there is enough data to empirically characterize and correct systematic biases. Second, the filtering criterion has been modified to account for the statistical distributions of SSS at each ocean grid point. This allows retrieving a value of SSS which is less affected by outliers originated from RFI and other effects. In this study, high level (spatio-temporally consistent) SSS maps are obtained by averaging the SMOS SSS retrievals using a classical objective analysis scheme and then combining the resulting maps with Sea Surface Temperature (SST) maps by means of multifractal fusion. The SSS fused maps contain well-defined spatial structures, suitable for studying the mesoscale activity in the Western

  6. Plio-Quaternary tectonic evolution off Al Hoceima, Moroccan Margin of the Alboran Basin.

    NASA Astrophysics Data System (ADS)

    Lafosse, Manfred; d'Acremont, Elia; Rabaute, Alain; Mercier de Lépinay, Bernard; Gorini, Christian; Ammar, Abdellah; Tahayt, Abdelilah

    2015-04-01

    We use data from a compilation of industrial and academic 2D surveys and recent data from MARLBORO-1 (2011), MARLBORO-2 (2012), and SARAS (2012) surveys, which provide high resolution bathymetry and 2D seismic reflexion data. We focus on the key area located south of the Alboran Ridge and the Tofiño Bank, and encompassing the Nekor and Boudinar onshore-offshore basins on the Moroccan side of the Alboran Sea. The Nekor basin is a present pull-apart basin in relay between inherited N050° sinistral strike-slip faults. We consider that these faults define the Principal Displacement Zones (PDZ). The northern PDZ marks the position of the crustal Bokkoya fault, which is connected to the Al-Idrisi Fault Zone en relais with the Adra and Carboneras Fault Zones. On the seabed, right-stepping non-coalescent faults characterize the sinistral kinematics of the northern PDZ and give a general N050° azimuth for the crustal discontinuity. The southern PDZ corresponds to the Nekor fault Zone, a Miocene sinistral strike-slip fault acting as the structural limit of the External Rif. On its eastern edge, the Nekor basin is bounded by the N-S onshore-offshore Trougout fault, connecting the northern and the southern PDZ. The western boundary of the Nekor basin is marked by the Rouadi and El-Hammam Quaternary active N-S normal faults. In the offshore Nekor basin, recent N155° conjugated normal faults affect the seabed. Further east, the Boudinar basin is a Plio-Quaternary uplifted Neogene basin. The northeastern segment of the Nekor fault bounds this basin to the south but is inactive in the Quaternary. Normal east-dipping N150° faults are visible offshore in the continuity of the Boudinar fault. From our perspective, the orientation of major tectonic structures (Bokkoya, Nekor and Carboneras faults and the Alboran ridge) under the present compressive regime due to the Europe/Africa convergence is not compatible with a strike-slip motion. The orientation of the most recent Plio

  7. Neogene tectonic evolution of the southwestern Alboran Basin as inferred from seismic data off Morocco

    SciTech Connect

    Chalouan, A.; Saji, R.; Michard, A.; Bally, A.W.

    1997-07-01

    The southwestern part of the western Mediterranean Alboran Basin, including part of the Alboran ridge (Xaouen Bank), was investigated through the analysis of 28 intersecting multichannel seismic lines. The seismic stratigraphy is tied to the Amoco well El-Jebha 1. Five seismic units or subunits are described from the Quaternary to the middle (and lower?) Miocene. The acoustic basement is interpreted to be mainly Paleozoic and Triassic metamorphic rocks of the Alboran Domain nappes, and, in places, middle Miocene-Messinian calc-alkalic volcanics. In the depocenters, the thickness of the sedimentary infill (mostly clays and turbidites) exceeds 9 km. Normal faults of middle Miocene-Tortonian age are broadly parallel to the coast, and dip either seaward or landward. They were mostly inverted during pre- and post-Messinian episodes of compression, which formed a set of en echelon, north-verging faulted folds in the Alboran ridge area, in relation with sinistral movement along the offshore projection of the Jebha fault. After Pliocene subsidence, a final episode of compression reactivated the earlier folds and pushed the Alboran ridge onto the Moroccan slope. The complex structural history suggests many structural and stratigraphic potential hydrocarbon traps. A high-resolution seismic survey could lead to the definition of new exploration plays.

  8. Gulf Stream eddies - Recent observations in the western Sargasso Sea.

    NASA Technical Reports Server (NTRS)

    Richardson, P. L.; Knauss, J. A.; Strong, A. E.

    1973-01-01

    A cyclonic Gulf Stream eddy was observed in the western Sargasso Sea by satellite infrared measurements and later confirmed by ship measurements. Fourteen months of observations indicate that the eddy moved southwestward at an average rate of 1 mile per day. The evidence suggests that the eddy was absorbed by the Gulf Stream off Florida.

  9. Locating the Caledonian Deformation Front in the Western Barents Sea

    NASA Astrophysics Data System (ADS)

    Shulgin, Alexey; Aarseth, Iselin; Faleide, Jan-Inge; Mjelde, Rolf; Huismans, Ritske

    2016-04-01

    The crustal architecture of the Paleozoic sedimentary basins and the underlying basement is still not fully understood in the Western Barents Sea region. It has been proposed that the major basins have developed along the structural framework inherited from the early Devonian Caledonian orogeny. However, the location of the Caledonian suture zone and its orientation and the extent of the deformation front are still poorly constrained and are ambiguous in the Barents Sea. Two orientations of the Caledonian Deformation Front (CDF) have been proposed earlier: north-south (from the potential fields data) and southwest-northeast (from seismic data). Knowledge of the spatial extent and orientation of the CDF has a major effect on our understanding of the evolution of the Barents Sea and provides important constrains on the basin-basement interaction. In 2014 a marine seismic experiment was conducted in the Western Barents Sea. One of the goals of the experiment is to discriminate between two proposed models and to constrain the location of the Caledonian Deformation front offshore northern Norway. We present the joint interpretation of collocated newly collected wide-angle seismic data (Ocean Bottom Seismometers) and reprocessing of the reflection seismic dataset (Multi-channel seismics) collected in the mid 80's, using modern computational techniques. The two seismic methods provide best resolution at different depth ranges, and in our modeling we combine the results from the two methods to constrain the location of the CDF along transect running Northwest-Southeast across the Western Barents Sea.

  10. Changes in sediment processes across the western Irish Sea front

    NASA Astrophysics Data System (ADS)

    Trimmer, M.; Gowen, R. J.; Stewart, B. M.

    2003-04-01

    Sediment characteristics, sediment respiration (oxygen uptake and sulphate reduction) and sediment-water nutrient exchange, in conjunction with water column structure and phytoplankton biomass were measured at five stations across the western Irish Sea front in August 2000. The transition from thermally stratified (surface to bottom temperature difference of 2.3 °C) to isothermal water (14.3 °C) occurred over a distance of 13 km. The influence of the front on phytoplankton biomass was limited to a small region of elevated near surface chlorophyll (2.23 mg m -3; 50% > biomass in mixed waters). The front clearly marked the boundary between depositional sediments (silt/clays) with elevated sediment pigment levels (≈60 mg m -2) on the western side, to pigment impoverished (<5 mg m -2) sand, through to coarse sand and shell fragments on the eastern side. Maximal rates of sedimentary respiration on the western stratified side of the front e.g. oxygen uptake S2 (852 μmol O 2 m -2 h -1) and sulphate reduction at S1 (149 μmol SO 42- m -2 h -1), coupled to significant efflux of nitrate and silicate at the western stations indicate closer benthic-pelagic coupling in the western Irish Sea. Whether this simply reflects the input of phytodetritus from the overlying water column or entrapment and settlement of pelagic production from other regions of the Irish Sea cannot yet be resolved.

  11. Severe rainfall events over the western Mediterranean Sea: A case study

    NASA Astrophysics Data System (ADS)

    Riesco Martín, Jesús; Mora García, Manuel; de Pablo Dávila, Fernando; Rivas Soriano, Luis

    2013-06-01

    A study of severe rainfall (≥ 100 mm in 24 h) over the Spanish provinces of Malaga, Granada y Almeria (close to the Alboran Sea, the westernmost part of the Mediterranean Sea) has been performed using 5 years (2006-2010) of data. The episodes of heavy rainfall were classified using the moisture flux at the 850 hPa pressure level and the lifted index. This gave three types, associated with situations of intense moisture flux and little static instability, moderate moisture flux and static instability, and moderate moisture flux and strong static instability. Representative cases of each type were analyzed, and it was found that both non-convective (41% of cases) and convective (59% of cases) systems caused the episodes of severe precipitation considered in this study. The convective structures included isolated and persistent convective systems, multicellular convective systems, and mesoscale convective systems.

  12. Simulation of Coastal Polynyas in the Western Weddell Sea

    NASA Astrophysics Data System (ADS)

    Haid, Verena; Timmermann, Ralph

    2010-05-01

    Coastal polynyas play a prominent role in the formation and modification of water masses in the polar oceans. A coastal polynya is usually kept open mechanically, primarily by winds, and the ocean surface is at freezing point. Thus a major fraction of the annual ice production of the high-latitude oceans occurs in polynyas and hence the duration and extent of their appearance has a substantial effect on bottom water formation. In the western Weddell Sea, recurring coastal polynyas are formed in front of the Filchner-Ronne Ice Shelf and in the area of the decayed Larsen A/B Ice Shelf. Simulations to study polynya formation and their impact on ice production and bottom water formation in the western Weddell Sea were performed with the Finite Element Sea ice-Ocean Model (FESOM) of Alfred-Wegener-Institute (AWI). FESOM is a fully coupled system of a primitive-equation, hydrostatic ocean model and a dynamic-thermodynamic sea ice model. The simulations were conducted on a global grid with a resolution varying between roughly 300 km in tropical latitudes and <5 km along the coast of the southwestern Weddell Sea. In vertical direction, the grid uses terrain-following coordinates. The model results give insight into the mechanisms governing the formation of transient and persistent polynyas and their influence on ice production and deep water formation. Water mass formation and ice export rates are quantified and compared to observation-based estimates.

  13. Bathymetry and Canyons of the western Solomon Sea

    NASA Astrophysics Data System (ADS)

    Davies, H. L.; Keene, J. B.; Hashimoto, K.; Joshima, M.; Stuart, J. E.; Tiffin, D. L.

    1986-12-01

    The floor of the western Solomon Sea (for new bathymetric map see inside back cover of this issue) is dominated by the arched and ridged basement of the Solomon Sea Basin, the partly-sediment-filled New Britain Trench, and a more completely filled trench, the Trobriand Trough. There is a deep basin where the trenches join (149° Embayment), and a silled basin west of the New Britain Trench (Finsch Deep). Submarine canyons descend from the west and south to the 149° Embayment. Abyssal fans and plains are structurally defined and locally disturbed by young faults. Probable submerged pinnacle reefs stand in water depths as great as 1,200 m.

  14. Observations of sea ice and icebergs in the western Barents Sea during the winter of 1987

    SciTech Connect

    Loeset, S.; Carstens, T.

    1995-12-31

    A multisensor ice data acquisition program for the western Barents Sea was carried out during three field campaigns in the mid winter and fall of 1987. The main purpose of the program was to obtain comprehensive information about the ice in the area at that time. The reasoning was that prior to any oil/gas exploration and production in the Barents Sea, the physical environment has to be quantitatively surveyed in order to ensure safe operations related to human safety, the regular operability and safety of the structure and protection of the environment. Prior to this field investigation program in 1987 data on sea ice and icebergs for engineering purposes for the western Barents Sea were meager. The present paper highlights some of the findings with emphasis on ice edge speeds, ice edge displacement and ice drift. For icebergs, the paper focuses on population, size distributions and geometric parameters.

  15. Per- and polyfluoroalkyl substances in the Western Mediterranean Sea waters.

    PubMed

    Brumovský, Miroslav; Karásková, Pavlína; Borghini, Mireno; Nizzetto, Luca

    2016-09-01

    The spatial and temporal distribution of per- and polyfluoroalkyl substances (PFASs) in the open Western Mediterranean Sea waters was investigated in this study for the first time. In addition to surface water samples, a deep water sample (1390 m depth) collected in the center of the western basin was analyzed. Perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorooctanoic acid (PFOA), perfluorohexanesulfonate (PFHxS) and perfluorooctanesulfonate (PFOS) were detected in all samples and were the dominant PFASs found. The sum of PFAS concentrations (ΣPFASs) ranged 246-515 pg/L for surface water samples. PFASs in surface water had a relatively homogeneous distribution with levels similar to those previously measured in the Atlantic near the Strait of Gibraltar, in water masses feeding the inflow to the Mediterranean Sea. Higher concentrations of PFHxA, PFHpA and PFHxS were, however, found in the present study. Inflowing Atlantic water and river/coastal discharges are likely the major sources of PFASs to the Western Mediterranean basin. Slightly lower (factor of 2) ΣPFASs was found in the deep water sample (141 pg/L). Such a relatively high contamination of deep water is likely to be linked to recurring deep water renewal fed by downwelling events in the Gulf of Lion and/or Ligurian Sea. PMID:27314632

  16. The diet of whiting Merlangius merlangus in the western Baltic Sea.

    PubMed

    Ross, S D; Gislason, H; Andersen, N G; Lewy, P; Nielsen, J R

    2016-05-01

    The diet of whiting Merlangius merlangus in the western Baltic Sea was investigated and compared to the diet in the southern North Sea. Clupeids were important prey in both areas, but especially in the western Baltic Sea where they constituted up to 90% of the diet of larger individuals. Gobies, brown shrimps and polychaetes were the main prey of juveniles in the western Baltic Sea, while a wider range of species were consumed in the North Sea. The shift to piscivory occurred at smaller sizes in the western Baltic Sea and the fish prey consumed was proportionately larger than in the southern North Sea. Estimates of prey abundance and food intake of M. merlangus are required to evaluate its predatory significance in the western Baltic Sea, but its diet suggests that it could be just as significant a fish predator here as in the southern North Sea. PMID:27005681

  17. Seimic Images and Wide-angle Velocity constrains of the structure and geodynamic origin of the Gibraltar Arc system: A geological interpretation of the Gulf of Cadiz imbricated wedge, the western and eastern Alboran basins, and the South-Balearic basin.

    NASA Astrophysics Data System (ADS)

    Gracia, E.; Ranero, C. R.; Grevemeryer, I.; WestMed, TopoMed, , T. h. e.; cruise parties, Geomargen-1

    2012-04-01

    The current geodynamics of the region between north Africa and the Iberian Peninsula are dominated by the collision between the Eurasian and African plates. The ongoing deformation is mainly driven by the NW-SE, slow 4-5 mm/yr convergence that is partitioned across numerous faults and diffused through a broad region with no clear plate boundary defined. However, this region is characterized by the a series of geological structures that appear unrelated to the current dominant plate kinematics. The region is formed by the Gibraltar Arc system, an arcuate structure that is fronted by a large imbricated wedge of tectonically piled sediment slices in the Gulf of Cadiz, and a series of basins in the Mediterranean part of the region. The western, little deformed Alboran basin is located on the rear of the Gibraltar stacked units. The eastern Alboran basin is characterized by numerous volcanic ridges and is transitional to the South Balearic - North Algerian basin that displays a generally lower topography. The different tectonic elements are floored by a poorly known crystalline basement and their age, evolution and geodynamic origin is still strongly debated. Part of the uncertainty arises from the lack of deep penetrating modern geophysical data in much of the region. In the last 5 years, 3 successive cruise in the region have produced an extensive coverage of the different tectonic elements collection a series of wide angle seismic profiles in 2006 during the WestMed cruise with German R/V Meteor and two multichannel seismic reflection cruises with the R/V Sarmiento de Gamboa from mid September to late October (TopoMed-Gassis cruise) and late October to late November (Geomargen-1 cruise) 2011. In this contribution we present the new images of the tectonic structures and sedimentary basin and the wide-angle seismic velocity models across key regions of the system. We also present an interpretation of the entire system in the context of a geodynamic model of eastward

  18. Recent trends in Sea ice in the southern and western Baltic and the North Sea

    NASA Astrophysics Data System (ADS)

    Holfort, Jürgen; Schmelzer, Natalija; Schwegmann, Sandra

    2016-04-01

    We analyzed sea ice charts and observations of a 50 year long period starting in 1961 to produce two climatological ice atlases, one for the western and southern Baltic and one for the German Bight and Limfjord. As the year to year variability is large we subdivided the 50 year into three overlapping 30 year periods (1961-1990, 1971-2000 and 1981-2010) to look for trends in the sea ice. In the southern and western Baltic as well as in the North Sea there was a clear decrease in the total frequency of ice occurrence. Other parameters like begin and end of the ice season, ice thickness, etc. did not show such clear signal and also showed larger regional differences. The ice conditions mainly changed in accordance with the changes in air temperature in the same period, although some more regional changes in some parameters were most probably also influenced by other factors like the deepening of fairways.

  19. Changes in sea-ice cover and temperature in the Western Ross Sea during the Holocene

    NASA Astrophysics Data System (ADS)

    Fleury, Sophie; Kim, Jung-Hyun; Gal, Jong-Ku; Mezgec, Karin; Belt, Simon; Smik, Lukas; Stenni, Barbara; Melis, Romana; Crosta, Xavier; Shin, Kyung-Hoon

    2016-04-01

    Although changes in sea-ice cover contribute to global climatic variations, they are poorly constrained for periods earlier than the last decades. More records are especially required around Antarctica, where the formation of Antarctic Bottom Waters participates to global thermohaline circulation. However, this region provided only a few marine sediment cores spanning the entire Holocene, especially because of generally low sedimentation rates. This study focuses on marine sediment core ANTA99-CJ5 (73°49'S; 175°39'E), located in the open sea ice zone (OSIZ) of the western Ross Sea. We analyzed several lipid biomarkers: highly branched isoprenoids (HBIs), sterols, diols and GDGTs. The combination of several biomarkers and the comparison of these results with a diatom record previously published on the same core enabled us to trace past changes in temperatures as well as in sea-ice condition over the last 11,600 years.

  20. Structure of the mantle beneath the Alboran Basin from magnetotelluric soundings

    NASA Astrophysics Data System (ADS)

    Garcia, X.; Seillé, H.; Elsenbeck, J.; Evans, R. L.; Jegen, M.; Hölz, Sebastian; Ledo, J.; Lovatini, A.; Marti, A.; Marcuello, A.; Queralt, P.; Ungarelli, C.; Ranero, C. R.

    2015-12-01

    We present results of marine MT acquisition in the Alboran sea that also incorporates previously acquired land MT from southern Spain into our analysis. The marine data show complex MT response functions with strong distortion due to seafloor topography and the coastline, but inclusion of high resolution topography and bathymetry and a seismically defined sediment unit into a 3-D inversion model has allowed us to image the structure in the underlying mantle. The resulting resistivity model is broadly consistent with a geodynamic scenario that includes subduction of an eastward trending plate beneath Gibraltar, which plunges nearly vertically beneath the Alboran. Our model contains three primary features of interest: a resistive body beneath the central Alboran, which extends to a depth of ˜150 km. At this depth, the mantle resistivity decreases to values of ˜100 Ohm-m, slightly higher than those seen in typical asthenosphere at the same depth. This transition suggests a change in slab properties with depth, perhaps reflecting a change in the nature of the seafloor subducted in the past. Two conductive features in our model suggest the presence of fluids released by the subducting slab or a small amount of partial melt in the upper mantle (or both). Of these, the one in the center of the Alboran basin, in the uppermost-mantle (20-30 km depth) beneath Neogene volcanics and west of the termination of the Nekkor Fault, is consistent with geochemical models, which infer highly thinned lithosphere and shallow melting in order to explain the petrology of seafloor volcanics.

  1. The deepwater demersal ichthyofauna of the western Coral Sea.

    PubMed

    Last, Peter R; Pogonoski, John J; Gledhill, Daniel C; White, William T; Walker, Chris J

    2014-01-01

    The highly diverse deepwater demersal ichthyofauna of the western Coral Sea was first systematically surveyed in two exploratory voyages in 1985 and 1986, and these fish assemblages have not been investigated at the same level since. Only recently have catch data and specimens, obtained from these first voyages almost 3 decades ago, been rigorously investigated and analysed. Some 393 species of fishes from 125 families were collected during the 1985 voyage which surveyed the northeastern Australian continental margin, and the Saumarez and Queensland Plateaus. A checklist of the species caught is provided. Levels of endemicity of deepwater fishes in the western Coral Sea are very high with about 50% of well-studied groups, such as sharks and rays, confined to this relatively small geographic region. A very high proportion of species caught during this voyage were either undescribed (78 species or 20%) or new Australian records (96 species or 24%) at the time of the survey. Another 68 species (17%) are the subject of further taxonomic investigation or are currently undergoing formal description. The fauna exhibits some intraregional differences in structure. Biogeographically informative fishes such as skates appear to be cryptically partitioned within the region, differing in composition to other Australian regions and those of French territories to the east. Strong depth-related partitioning of the fauna is also evident, and its structure follows zonation patterns observed across the wider Australian region. Given the high level of micro-endemicity and regional uniqueness of the fauna, there is a compelling argument for the existence of a faunal gyre in the Coral Sea.  New gap-filling surveys are needed to better define the structure of this fauna and determine its distribution. PMID:25543931

  2. Phytoplankton community and hydrochemical characteristics of the Western Black Sea.

    PubMed

    Velikova, V; Cociasu, A; Popa, L; Boicenco, L; Petrova, D

    2005-01-01

    Since the early 1990s the persistent reports about the irreversibly degrading Black Sea have started to disappear. A large set of data, reflecting the temporal and spatial variability of microalgae and hydrochemical parameters in Western Black Sea waters (WBS), collected in 2001-2002 (EU 5th FP project "daNubs"), allows us to compare the present-day ecosystem functioning to previous ones and to certainly conclude on positive signs of relaxation. The years 2001 and 2002 were without ample, negative biological and hydrochemical events in the WBS. Nutrient general trend was a decreasing one since the late 1980s, and inorganic phosphorus and nitrogen concentrations were frequently below the method detection limits during summer autumn periods of 2001-2002. The shelf waters were properly oxygenated. The phytoplankton community was producing biomass in a decreasing tendency, especially obviously since 1995. Simultaneously, there was an increase in Si:P and Si:N molar ratios and concurrent increase in the diversity of mass algal species (mainly diatoms) but only a few of them generated exceptional blooms. Reduction of the ratios between phytoplankton and zooplankton biomasses became evident. The observed ecological status in 2001-2002 confirms that the Black Sea is no longer a reference point for progressive water quality deterioration. PMID:16114612

  3. Interannual to decadal variation of spring sea level anomaly in the western South China Sea

    NASA Astrophysics Data System (ADS)

    Qiu, Fuwen; Fang, Wendong; Pan, Aijun; Cha, Jing; Zhang, Shanwu; Huang, Jiang

    2016-04-01

    Satellite observations of sea level anomalies (SLA) from January 1993 to December 2012 are used to investigate the interannual to decadal changes of the boreal spring high SLA in the western South China Sea (SCS) using the Empirical Orthogonal Function (EOF) method. We find that the SLA variability has two dominant modes. The Sea Level Changing Mode (SLCM) occurs mainly during La Niña years, with high SLA extension from west of Luzon to the eastern coast of Vietnam along the central basin of the SCS, and is likely induced by the increment of the ocean heat content. The Anticyclonic Eddy Mode (AEM) occurs mainly during El Niño years and appears to be triggered by the negative wind curl anomalies within the central SCS. In addition, the spring high SLA in the western SCS experienced a quasi-decadal change during 1993-2012; in other words, the AEM predominated during 1993-1998 and 2002-2005, while the La Niña-related SLCM prevailed during 1999-2001 and 2006-2012. Moreover, we suggest that the accelerated sea level rise in the SCS during 2005-2012 makes the SLCM the leading mode over the past two decades.

  4. An asymmetric upwind flow, Yellow Sea Warm Current: 1. New observations in the western Yellow Sea

    NASA Astrophysics Data System (ADS)

    Lin, Xiaopei; Yang, Jiayan; Guo, Jingsong; Zhang, Zhixin; Yin, Yuqi; Song, Xiangzhou; Zhang, Xiaohui

    2011-04-01

    The winter water mass along the Yellow Sea Trough (YST), especially on the western side of the trough, is considerably warmer and saltier than the ambient shelf water mass. This observed tongue-shape hydrographic feature implies the existence of a winter along-trough and onshore current, often referred to as the Yellow Sea Warm Current (YSWC). However, the YSWC has not been confirmed by direct current measurements and therefore skepticism remains regarding its existence. Some studies suggest that the presence of the warm water could be due to frontal instability, eddies, or synoptic scale wind bursts. It is noted that in situ observations used in most previous studies were from the central and eastern sides of the YST even though it is known that the warm water core is more pronounced along the western side. Data from the western side have been scarce. Here we present a set of newly available Chinese observations, including some from a coordinated effort involving three Chinese vessels in the western YST during the 2006-2007 winter. The data show unambiguously the existence of the warm current on the western side of YST. Both the current and hydrography observations indicate a dominant barotropic structure of YSWC. The westward deviation of YSWC axis is particularly obvious to the south of 35°N and is clearly associated with an onshore movement of warm water. To the north of 35°N, the YSWC flows along the bathymetry with slightly downslope movement. We conclude that the barotropic current is mainly responsible for the warm water intrusion, while the Ekman and baroclinic currents play an important but secondary role. These observations help fill an observational gap and establish a more complete view of the YSWC.

  5. Interannual differences for sea turtles bycatch in Spanish longliners from Western Mediterranean Sea.

    PubMed

    Báez, José C; Macías, David; García-Barcelona, Salvador; Real, Raimundo

    2014-01-01

    Recent studies showed that regional abundance of loggerhead and leatherback turtles could oscillate interannually according to oceanographic and climatic conditions. The Western Mediterranean is an important fishing area for the Spanish drifting longline fleet, which mainly targets swordfish, bluefin tuna, and albacore. Due to the spatial overlapping in fishing activity and turtle distribution, there is an increasing sea turtle conservation concern. The main goal of this study is to analyse the interannual bycatch of loggerhead and leatherback turtles by the Spanish Mediterranean longline fishery and to test the relationship between the total turtle by-catch of this fishery and the North Atlantic Oscillation (NAO). During the 14 years covered in this study, the number of sea turtle bycatches was 3,940 loggerhead turtles and 8 leatherback turtles, 0.499 loggerhead turtles/1000 hooks and 0.001014 leatherback turtles/1000 hooks. In the case of the loggerhead turtle the positive phase of the NAO favours an increase of loggerhead turtles in the Western Mediterranean Sea. However, in the case of leatherback turtle the negative phase of the NAO favours the presence of leatherback turtle. This contraposition could be related to the different ecophysiological response of both species during their migration cycle. PMID:24764769

  6. Interannual Differences for Sea Turtles Bycatch in Spanish Longliners from Western Mediterranean Sea

    PubMed Central

    Báez, José C.; García-Barcelona, Salvador

    2014-01-01

    Recent studies showed that regional abundance of loggerhead and leatherback turtles could oscillate interannually according to oceanographic and climatic conditions. The Western Mediterranean is an important fishing area for the Spanish drifting longline fleet, which mainly targets swordfish, bluefin tuna, and albacore. Due to the spatial overlapping in fishing activity and turtle distribution, there is an increasing sea turtle conservation concern. The main goal of this study is to analyse the interannual bycatch of loggerhead and leatherback turtles by the Spanish Mediterranean longline fishery and to test the relationship between the total turtle by-catch of this fishery and the North Atlantic Oscillation (NAO). During the 14 years covered in this study, the number of sea turtle bycatches was 3,940 loggerhead turtles and 8 leatherback turtles, 0.499 loggerhead turtles/1000 hooks and 0.001014 leatherback turtles/1000 hooks. In the case of the loggerhead turtle the positive phase of the NAO favours an increase of loggerhead turtles in the Western Mediterranean Sea. However, in the case of leatherback turtle the negative phase of the NAO favours the presence of leatherback turtle. This contraposition could be related to the different ecophysiological response of both species during their migration cycle. PMID:24764769

  7. PICASSO: Shear velocities in the Western Mediterranean from Rayleigh Wave tomography

    NASA Astrophysics Data System (ADS)

    Palomeras, I.; Thurner, S.; Levander, A.

    2012-12-01

    The Western Mediterranean has been affected by complex subduction and slab rollback, simultaneously with compression due to African-European convergence. The deformed region occupies a wide area from the intra-continental Atlas mountain belt in Morocco to the southern Iberian Massif in Spain. Evolutionary models of the Western Mediterranean invoke extensive slab rollback and compression in the Cenozoic, as well as likely upper mantle delamination scenarios during formation of the Alboran domain, the Betics, Rif, and Atlas Mountains. PICASSO (Program to Investigate Convective Alboran Sea System Overturn) is a multidisciplinary, international investigation of the Alboran System and surrounding areas. In this study we have analyzed data from the 95 PICASSO broadband stations with data from the Spanish IberArray and Siberia Array in Spain and Morocco, the University of Muenster array in the Atlas Mountains and the permanent Spanish and Portuguese networks. We present Rayleigh wave tomography results made from 168 teleseimic events recorded by 237 stations from April 2009 to April 2011. We measured Rayleigh phase velocities using the two-plane-wave method to remove complications due to multi-pathing, and finite-frequency kernels to improve lateral resolution. Phase velocities were then inverted for shear velocity structure on a grid of 0.5 by 0.5 degree to form a well-resolved 3D shear velocity model to 230 km depth. Our results show low S-velocities (2.9 km/s) in the crust beneath the Gibraltar Strait. Low upper mantle S-velocities are mapped beneath the Middle and High Atlas at ~60 km depth suggesting an elevated asthenosphere beneath these young mountain belts, in agreement with receiver functions analysis (Thurner et al, this session). Beneath the Western Alboran Sea, upper-mantle velocities change laterally from high velocities (>4.5 km/s) in the east to lower velocities to the west (~4.3 km/s). The Rayleigh wave tomography is consistent with P-tomography that

  8. Continent-ocean transition at the western Barents Sea/Svalbard continental margin

    SciTech Connect

    Eldholm, O.; Faleide, J.I.; Myhre, A.M.

    1987-12-01

    The change in crustal type at the western Barents Sea/Svalbard margin takes place over a narrow zone related to primary rift and shear structures reflecting the stepwise opening of the Greenland Sea. Regionally, the margin is composed of two large shear zones and a central rifted-margin segment. Local transtension and transpression at the plate boundary caused the early Cenozoic tectonism in Svalbard and the western Barents Sea, and might explain the prominent marginal gravity and velocity anomalies.

  9. Fish communities across a spectrum of habitats in the western Beaufort Sea and Chukchi Sea

    NASA Astrophysics Data System (ADS)

    Logerwell, E.; Busby, M.; Carothers, C.; Cotton, S.; Duffy-Anderson, J.; Farley, E.; Goddard, P.; Heintz, R.; Holladay, B.; Horne, J.; Johnson, S.; Lauth, B.; Moulton, L.; Neff, D.; Norcross, B.; Parker-Stetter, S.; Seigle, J.; Sformo, T.

    2015-08-01

    The increased scientific interest in the Arctic due to climate change and potential oil and gas development has resulted in numerous surveys of Arctic marine fish communities since the mid-2000s. Surveys have been conducted in nearly all Arctic marine fish habitats: from lagoons, beaches and across the continental shelf and slope. This provides an opportunity only recently available to study Arctic fish communities across a spectrum of habitats. We examined fish survey data from lagoon, beach, nearshore benthic, shelf pelagic and shelf benthic habitats in the western Beaufort Sea and Chukchi Sea. Specifically, we compare and contrast relative fish abundance and length (a proxy for age) among habitats and seas. We also examined ichthyoplankton presence/absence and abundance of dominant taxa in the shelf habitat. Our synthesis revealed more similarities than differences between the two seas. For example, our results show that the nearshore habitat is utilized by forage fish across age classes, and is also a nursery area for other species. Our results also indicated that some species may be expanding their range to the north, for example, Chinook Salmon. In addition, we documented the presence of commercially important taxa such as Walleye Pollock and flatfishes (Pleuronectidae). Our synthesis of information on relative abundance and age allowed us to propose detailed conceptual models for the life history distribution of key gadids in Arctic food webs: Arctic and Saffron Cod. Finally, we identify research gaps, such as the need for surveys of the surface waters of the Beaufort Sea, surveys of the lagoons of the Chukchi Sea, and winter season surveys in all areas. We recommend field studies on fish life history that sample multiple age classes in multiple habitats throughout the year to confirm, resolve and interpret the patterns in fish habitat use that we observed.

  10. Airborne gravity measurement over sea-ice: The western Weddel Sea

    SciTech Connect

    Brozena, J.; Peters, M. ); LaBrecque, J.; Bell, R.; Raymond, C. )

    1990-10-01

    An airborne gravity study of the western Weddel Sea, east of the Antarctic Peninsula, has shown that floating pack-ice provides a useful radar altimetric reference surface for altitude and vertical acceleration corrections surface for alititude and vertical acceleration corrections to airborne gravimetry. Airborne gravimetry provides an important alternative to satellite altimetry for the sea-ice covered regions of the world since satellite alimeters are not designed or intended to provide accurate geoidal heights in areas where significant sea-ice is present within the radar footprint. Errors in radar corrected airborne gravimetry are primarily sensitive to the variations in the second derivative of the sea-ice reference surface in the frequency pass-band of interest. With the exception of imbedded icebergs the second derivative of the pack-ice surface closely approximates that of the mean sea-level surface at wavelengths > 10-20 km. With the airborne method the percentage of ice coverage, the mixture of first and multi-year ice and the existence of leads and pressure ridges prove to be unimportant in determining gravity anomalies at scales of geophysical and geodetic interest, provided that the ice is floating and not grounded. In the Weddell study an analysis of 85 crosstrack miss-ties distributed over 25 data tracks yields an rms error of 2.2 mGals. Significant structural anomalies including the continental shelf and offsets and lineations interpreted as fracture zones recording the early spreading directions within the Weddell Sea are observed in the gravity map.

  11. Seismic stratigraphy of western Colombian basin, Caribbean Sea

    SciTech Connect

    Bowland, C.

    1984-04-01

    Multichannel seismic reflection profiles disclose the regional stratigraphy of the western Colombian basin. The basement complex is the seismic unit below the deepest, continuous reflection horizon that can be traced throughout the basin. The basement complex reflection signature on the flanks of the Mono Rise and adjacent areas is smooth, continuous, and characterized by local occurrences of internal reflectors, and is equivalent to the Late Cretaceous Horizon B in the Venezuelan basin. In the central basin, the reflection signature is rough with abundant diffractions typical of normal oceanic crust. The sediment overlying the basement complex is subdivided into five mapping units. Unit CB5, which directly overlies the basement complex, is thickest on the Mono Rise and thins down the flanks of the rise. This unit is equivalent to the Upper Cretaceous to the Middle Eocene pelagic unit bounded by seismic horizons A'' and B'' in the Venezuelan basin. Unit CB4, characterized by pervasive, small offset faulting, is restricted to the crest of the Mono Rise. Units CB3 and CB2 contain subparallel, variable amplitude, continuous reflectors that fill the regional basement complex relief. They are Middle Tertiary terrigenous distal turbidites and hemipelagic deposits. Unit CB1 thickens toward southern Central America and shows complicated reflection patterns typical of a deep-sea fan complex. A jump correlation to Deep Sea Drilling Project Site 154 is used to assign a Late Miocene to Quaternary age to unit CB1. Development of unit CB1 was concurrent with the uplift of and magmatic activity in southern Central America.

  12. Structure and sediment distribution in the western Bering Sea

    USGS Publications Warehouse

    Rabinowitz, P. D.; Cooper, A.

    1977-01-01

    Eleven seismic reflection profiles across Shirshov Ridge and the adjacent deep-water sedimentary basins (Komandorsky and Aleutian Basins) are presented to illustrate the sediment distribution in the western Bering Sea. A prominent seismic reflecting horizon, Reflector P (Middle-Late Miocene in age), is observed throughout both the Aleutian and Komandorsky Basins at an approximate subbottom depth of 1 km. This reflector is also present, in places, on the flanks and along the crest of Shirshov Ridge. The thickness of sediments beneath Reflector P is significantly different within the two abyssal basins. In the Aleutian Basin, the total subbottom depth to acoustic basement (basalt?) is about 4 km, while in the Komandorsky Basin the depth is about 2 km. Shirshov Ridge, a Cenozoic volcanic feature that separates the Aleutian and Komandorsky Basins, is an asymmetric bathymetric ridge characterized by thick sediments along its eastern flank and steep scarps on its western side. The southern portion of the ridge has more structural relief that includes several deep, sediment-filled basins along its summit. Velocity data from sonobuoy measurements indicate that acoustic basement in the Komandorsky Basin has an average compressional wave velocity of 5.90 km/sec. This value is considerably larger than the velocities measured for acoustic basement in the northwestern Aleutian Basin (about 5.00 km/sec) and in the central Aleutian Basin (5.40-5.57 km/sec). In the northwestern Aleutian Basin, the low-velocity acoustic basement may be volcaniclastic sediments or other indurated sediments that are overlying true basaltic basement. A refracting horizon with similar velocities (4.6-5.0 km/sec) as acoustic basement dips steeply beneath the Siberian continental margin, reaching a maximum subbottom depth of about 8 km. The thick welt of sediment at the base of the Siberian margin may be the result of sediment loading or tectonic depression prior to Late Cenozoic time. ?? 1977.

  13. Offshore Seismic Observation in the Western Marmara Sea, Turkey

    NASA Astrophysics Data System (ADS)

    Yamamoto, Y.; Takahashi, N.; Citak, S.; Kalafat, D.; Pinar, A.; Gurbuz, C.; Kaneda, Y.

    2014-12-01

    The North Anatolian Fault (NAF) extends 1600 km westward from a junction with the East Anatolian Fault at the Karliova Triple Junction in eastern Turkey, across northern Turkey and into the Aegean Sea, accommodating about 25 mm/yr of right-lateral motion between Anatolia and the Eurasian plate. Since 1939, devastating earthquakes with magnitude greater than seven ruptured NAF westward, starting from 1939 Erzincan at the eastern Turkey and including the latest 1999 Izmit-Golcuk and the Duzce earthquakes in the Marmara region. Considering the fault segments ruptured by the May 24th, 2014 Northern Aegean earthquake, the only un-ruptured segments left behind NAF locate beneath the Marmara Sea and those segments keep their mystery due to their underwater location. To clarify the detailed fault geometry beneath the western Marmara Sea, we started to operate a series of ocean bottom seismographic (OBS) observations. As a first step, we deployed 3 pop-up type OBSs on 20th of March 2014 as a trial observation, and recovered them on 18thof June 2014. Although one of the OBSs worked only 6 days from the start of the observation, other two OBSs functioned properly during the whole 3-month observation period. Only 8 earthquakes were reported near the OBS network in 3 months periods according to the Kandilli Observatory and Earthquake Research Institute catalogue. Thus, we first searched for the microearthquakes missing by the land seismic network and estimated their precious location by using the initial 6 days data. We could identify about 50 earthquakes with more than 5 picking data of P and S first arrivals, and half of them located near the NAF. We also tested the hypocenter relocation by combining the land and OBS seismic data for the 8 earthquakes, and found that these earthquakes are located in between 12-24 km depths. Next, we are planning to deploy 10 OBSs from September 2014 to June 2015 as a second step for our observation. At the AGU fall meeting, we will be able to

  14. Sperm whale assessment in the Western Ionian Sea using acoustic data from deep sea observatories

    NASA Astrophysics Data System (ADS)

    Caruso, Francesco; Bellia, Giorgio; Beranzoli, Laura; De Domenico, Emilio; Larosa, Giuseppina; Marinaro, Giuditta; Papale, Elena; Pavan, Gianni; Pellegrino, Carmelo; Pulvirenti, Sara; Riccobene, Giorgio; Scandura, Danila; Sciacca, Virginia; Viola, Salvatore

    2015-04-01

    The Italian National Institute of Nuclear Physics (INFN) operates two deep sea infrastructures: Capo Passero, Western Ionian Sea 3,600 meters of depth, and Catania Wester Ionian Sea 2,100 m depth. At the two sites, several research observatories have been run: OnDE, NEMO-SN1, SMO, KM3NeT-Italia most of them jointly operated between INFN and INGV. In all these observatories, passive acoustic sensors (hydrophones) have been installed. Passive Acoustics Monitoring (PAM) is nowadays the main tool of the bioacoustics to study marine mammals. In particular, receiving the sounds emitted by cetaceans from a multi-hydrophones array installed in a cabled seafloor observatory, a research about the ecological dynamics of the species may be performed. Data acquired with the hydrophones installed aboard the OnDE, SMO and KM3NeT-Italia observatories will be reported. Thanks to acquired data, the acoustic presence of the sperm whales was assessed and studied for several years (2005:2013). An "ad hoc" algorithm was also developed to allow the automatic identification of the "clicks" emitted by the sperm whales and measure the size of detected animals. According to the results obtained, the sperm whale population in the area is well-distributed in size, sex and sexual maturity. Although specimens more than 14 meters of length (old males) seem to be absent.

  15. WMOP: The SOCIB Western Mediterranean Sea OPerational forecasting system

    NASA Astrophysics Data System (ADS)

    Renault, Lionel; Juza, Mélanie; Garau, Bartolomé; Sayol, Juan Manuel; Orfila, Alejandro; Tintoré, Joaquín

    2013-04-01

    Development of science based ocean-forecasting systems at global, regional, sub-regional and local scales is needed to increase our understanding of ocean processes and to support knowledge based management of the marine environment. In this context, WMOP (Western Mediterranean sea /Balearic OPerational system) is the forecasting subsystem component of SOCIB, the new Balearic Islands Coastal Observing and Forecasting System. The WMOP system is operational since the end of 2010. The ROMS model is forced every 3 hours with atmospheric forcing derived from AEMET/Hirlam and daily boundary conditions provided by MFS2 from MyOcean/MOON. Model domain is implemented over an area extending from Gibraltar strait to Corsica/Sardinia (from 6°W to 9°E and from 35°N to 44.5°N), including Balearic Sea and Gulf of Lion. The grid is 631 x 539 points with a resolution of ~1.5km, which allows good representation of mesoscale and submesoscale features (first baroclinic Rossby radius ~10-15 km) of key relevance in this region. The model has 30 sigma levels, and the vertical s coordinate is stretched for boundary layer resolution, also essential to capture extreme events water masses formation and dynamical effects. Bottom topography is derived from a 2' resolution database. Online validation procedures based on inter-comparison of model outputs against observing systems and reference models such as MFS and Mercator are used to assess at what level the numerical models are able to reproduce the features observed from in-situ systems and remote sensing. The intrinsic three-dimensional variability of the coastal ocean and open-ocean exchanges imply the need of muti-plaform observing systems covering a variety of scales. Fixed moorings provide a good temporal resolution but poor spatial coverage, while satellite products provide a good spatial coverage but just on the surface layer. Gliders can provide a reasonable spatial variability in both horizontal and vertical axes. Thus, inter

  16. The summer gyre in the Western Irish Sea: Shelf sea paradigms and management implications

    NASA Astrophysics Data System (ADS)

    Hill, A. E.; Brown, J.; Fernand, L.

    1997-01-01

    A cyclonic, near-surface gyre has been discovered above the deep western Irish Sea basin. The gyre, present in spring and summer each year, is formed when stratification isolates a dome of cold bottom water which then drives a baroclinic circulation. Simultaneous observations using ship-mounted, broad-band acoustic Doppler current profiler, towed undulating CTD (conductivity, temperature, depth) and satellite-tracked drifting buoys reveal the detailed horizontal and vertical structure of the gyre. Gyre dynamics have been investigated using a three-dimensional, steady, diagnostic circulation model with realistic bathymetry. The role of the gyre within the existing Bowden-Simpson paradigm of shelf circulation is discussed. Knowledge of seasonal gyre systems is important when formulating management strategies. For example, there is evidence that the Irish Sea gyre acts as a retention system for the planktonic larvae of the commercially valuable Norway lobster ( Nephrops norvegicus, Linnaeus 1758) which inhabits the geographically isolated mud patch beneath the gyre. Moreover, in the event of an accidental summer-time spill, the gyre could also act to retain contaminants, suggesting that this system is at disproportionate risk from environmental damage.

  17. Heat flux through sea ice in the western Weddell Sea: Convective and conductive transfer processes

    NASA Astrophysics Data System (ADS)

    Lytle, V. I.; Ackley, S. F.

    1996-04-01

    The heat flux through the snow and sea ice cover and at the ice/ocean interface were calculated at five sites in the western Weddell Sea during autumn and early winter 1992. The ocean heat flux averaged 7 ± 2 W/m2 from late February to early June, and average ice/air heat flux in the second-year floes depended on the depth of the snow cover and ranged from 9 to 17 (±0.8) W/m2. In late February, three of the five sites had an ice surface which was depressed below sea level, resulting, at two of the sites, in a partially flooded snow cover and a slush layer at the snow/ice interface. As this slush layer froze to form snow ice, the dense brine which was rejected flowed out through brine drainage channels and was replaced by lower-salinity, nutrient-rich seawater from the ocean upper layer. We estimate that about half of the second-year ice in the region was covered with this slush layer early in the winter. As the slush layer froze, over a 2- to 3-week period, the convection within the ice transported salt from the ice to the upper ocean and increased total heat flux through the overlying ice and snow cover. On an area-wide basis, approximately 10 cm of snow ice growth occurred within second-year pack ice, primarily during a 2- to 3-week period in February and March. This ice growth, near the surface of the ice, provides a salt flux to the upper ocean equivalent to 5 cm of ice growth, despite the thick (about 1 m) ice cover, in addition to the ice growth in the small (area less than 5%), open water regions.

  18. Short-term biogenic particle flux under late spring sea ice in the western Weddell Sea

    NASA Astrophysics Data System (ADS)

    Michels, Jan; Dieckmann, Gerhard S.; Thomas, David N.; Schnack-Schiel, Sigrid B.; Krell, Andreas; Assmy, Philipp; Kennedy, Hilary; Papadimitriou, Stathis; Cisewski, Boris

    2008-04-01

    In the framework of the "Ice Station POLarstern" (ISPOL) expedition in the western Weddell Sea, two sediment traps were deployed at 10 and 70 m water depth under a drifting ice floe in December 2004. The amount and composition of the vertical particle flux under sea ice were determined during a period of 30 days in order to investigate the influence of biological processes in sea ice and on its underside on the flux. The total mass flux was dominated by diatoms, faecal material, and aggregates, and ranged from 95.28 to 197.67 mg m -2 d -1 at 10 m depth and from 51.54 to 55.34 mg m -2 d -1 at 70 m depth. A strong increase with time of the flux of chlorophyll equivalents, biogenic silica, and faecal material was recorded during the observation period, coincident with the increase in the concentration of chlorophyll a in the bottom ice layer above the trap array. The latter suggests a concomitant increase in the amount of food available for grazers, such as krill, in the bottom ice layer and on the underside of the ice floe, resulting in an increased downward transport of ice-algal material into the water column. The sinking faecal material was dominated by krill faecal strings and contained large amounts of diatom frustule debris, as well as intact diatom frustules, mainly of the species Fragilariopsis curta and F. cylindrus. Single pronounced flux events of Phaeocystis antarctica and aggregates were also observed early in the study period. Low POC/PON and biogenic silica/POC ratios of the sinking particulate matter suggest that the material collected in the traps was relatively fresh.

  19. Particle fluxes in the Almeria-Oran Front: control by coastal upwelling and sea surface circulation

    NASA Astrophysics Data System (ADS)

    Sanchez-Vidal, A.; Calafat, A.; Canals, M.; Fabres, J.

    2004-12-01

    Particle flux data were obtained from one instrumented array moored under the direct influence of the Almeria-Oran Front (AOF) in the Eastern Alboran Sea, Western Mediterranean Sea, within the frame of the "Mediterranean Targeted Project II-MAss Transfer and Ecosystem Response" (MTPII-MATER) EU-funded research project. The mooring line was deployed from July 1997 to May 1998, and was equipped with three sequential sampling sediment trap-current meter pairs at 645, 1170 and 2210 m (30 m above the seafloor). The settling material was analysed to obtain total mass, organic carbon, opal, calcium carbonate and lithogenic fluxes. Qualitative analyses of SST and SeaWiFS images allowed monitoring the location and development of the Western and Eastern Alboran Sea gyres and associated frontal systems to determine their influence on particle fluxes. Particle flux time series obtained at the three depths showed a downward decrease of the time-weighed total mass flux annual means, thus illustrating the role of pelagic particle settling. The total mass flux was dominated by the lithogenic fraction followed by calcium carbonate, opal and organic carbon. The time series at the various depths were rather similar, with two strong synchronous biogenic peaks (up to 98 mg m -2 day -1 of organic carbon and 156 mg m -2 day -1 of opal) recorded in July 1997 and May 1998. Through comparing the fluctuations of the lithogenic and calcium carbonate-rich fluxes with the biogenic flux, we observed that the non-biogenic fluxes remained roughly constant, while the biogenic flux responded strongly to seasonal variations throughout the water column. Overall, the temporal variability of particle fluxes appeared to be linked to the evolution of several tens of kilometres in length sea surface hydrological structures and circulation of the Alboran Sea. Periodic southeastward advective displacements of waters from upwelling events off the southern Spanish coast were observed on SST and SeaWiFS images

  20. Subduction initiation, recycling of Alboran lower crust, and intracrustal emplacement of subcontinental lithospheric mantle in the Westernmost Mediterranean

    NASA Astrophysics Data System (ADS)

    Varas-Reus, María Isabel; Garrido, Carlos J.; Bosch, Delphine; Marchesi, Claudio; Hidas, Károly; Booth-Rea, Guillermo; Acosta-Vigil, Antonio

    2015-04-01

    Unraveling the tectonic settings and processes involved in the annihilation of subcontinental mantle lithosphere is of paramount importance for our understanding of the endurance of continents through Earth history. Unlike ophiolites -- their oceanic mantle lithosphere counterparts -- the mechanisms of emplacement of the subcontinental mantle lithosphere in orogens is still poorly known. The emplacement of subcontinental lithospheric mantle peridotites is often attributed to extension in rifted passive margins or continental backarc basins, accretionary processes in subduction zones, or some combination of these processes. One of the most prominent features of the westernmost Mediterranean Alpine orogenic arcs is the presence of the largest outcrops worldwide of diamond facies, subcontinental mantle peridotite massifs; unveiling the mechanisms of emplacement of these massifs may provide important clues on processes involved in the destruction of continents. The western Mediterranean underwent a complex Alpine evolution of subduction initiation, slab fragmentation, and rollback within a context of slow convergence of Africa and Europe In the westernmost Mediterranean, the alpine orogeny ends in the Gibraltar tight arc, which is bounded by the Betic, Rif and Tell belts that surround the Alboran and Algero-Balearic basins. The internal units of these belts are mostly constituted of an allochthonous lithospheric domain that collided and overthrusted Mesozoic and Tertiary sedimentary rocks of the Mesozoic-Paleogene, South Iberian and Maghrebian rifted continental paleomargins. Subcontinental lithospheric peridotite massifs are intercalated between polymetamorphic internal units of the Betic (Ronda, Ojen and Carratraca massifs), Rif (Beni Bousera), and Tell belts. In the Betic chain, the internal zones of the allochthonous Alboran domain include, from bottom to top, polymetamorphic rock of the Alpujarride and Malaguide complexes. The Ronda peridotite massif -- the

  1. Deuterium excess as a proxy for sea ice extent in the western Ross Sea, Antarctica, 1882-2006

    NASA Astrophysics Data System (ADS)

    Sinclair, K. E.; Bertler, N.; Zwartz, D.; Trompetter, B.; Millet, M.; Davy, P.

    2011-12-01

    Deuterium excess in a high-resolution ice core extracted from the Whitehall Glacier (WHG) is highly sensitive to sea ice extent since observations began in 1979. Seasonal sea ice extent has increased significantly in the Ross Sea since 1995, creating a dipole between the Ross Sea and the Amundsen and Bellinghausen Sea Coasts, which have experienced significant sea ice loss. The reasons for the spatial differences in sea ice anomalies is thought to be primarily related to the phase of the Southern Annular Mode (SAM), the primary climate driver in this sector of Antarctica, and the complex interactions of SAM with the El Niño-Southern Oscillation (ENSO). A positive phase of SAM leads to deeper low pressure anomalies in the Amundsen Sea; cooler and stronger southerly winds in the western Ross Sea, and wind-driven sea ice advance, particularly when it is reinforced by La Nina conditions. In the WHG ice core, deuterium excess has mean values of 9.5 per mil from 1979 until 1994 and 5.2 per mil after 1995. This ~5 per mil shift is concurrent with a change from negative to positive sea ice extent anomalies in the Ross Sea and a concurrent decrease in marine trace elements (Na, Mg, V, Rb). We argue that increased southerly winds since 1995 (related to a more positive SAM) have increased the area of the Ross Sea and Terra Nova Bay polynas resulting in increased sea ice extent. Because sea surface temperatures (SST) are very low over these polynas, particularly in the austral autumn and winter, the deuterium excess signal at the Whitehall Glacier is highly sensitive to the amount of local moisture input and the seasonality of this moisture contribution. Increased local moisture, with low SST, results in low deuterium excess and therefore an inverse relationship with sea ice extent. In the context of the 125-year span of the WHG record, (1882-2006), deuterium excess is markedly high (and sea ice coverage is therefore expected to have been anomalously low) in the 1950s, '60s

  2. Coral-based Holocene sea level of Paraoir, western Luzon, Philippines

    NASA Astrophysics Data System (ADS)

    Siringan, Fernando P.; Shen, Chuan-Chou; Lin, Ke; Abigania, Maria Isabel T.; Gong, Shou-Yeh

    2016-06-01

    Shallow-water corals are crucial natural archives for reconstructing deglacial sea-level changes. However, significant discrepancies exist between sea-level records from different places. Here we present recently acquired 230Th-dated coral ages between 10,256 ± 50 yr BP and 6654 ± 29 yr BP (before 1950 AD) from Paraoir, western Luzon, Philippines to document deglacial sea-level rise of the western Pacific. The results indicate that the Paraoir reef started growing 10.3 kyr BP from about 29 m below present sea level, and reached 8 m below the PSL at 7.2 kyr BP. The Paraoir sea-level records are consistent with those of northwestern Luzon and the western Australia coast; both of which are coral-based records in continental or island arc settings. But sea levels of Luzon are significantly higher than those of Tahiti, a basaltic island on oceanic crust. We propose that the differences in sea level between the Philippine and Tahiti result from spatial variations of glacial isostatic adjustment of the two sites.

  3. Difference of mercury bioaccumulation in red mullets from the north-western Mediterranean and Black seas.

    PubMed

    Harmelin-Vivien, M; Cossa, D; Crochet, S; Bănaru, D; Letourneur, Y; Mellon-Duval, C

    2009-05-01

    The relationships between total mercury (Hg) concentration and stable nitrogen isotope ratio (delta(15)N) were evaluated in Mullus barbatus barbatus and M. surmuletus from the Mediterranean Sea and M. barbatus ponticus from the Black Sea. Mercury concentration in fish muscle was six times higher in the two Mediterranean species than in the Black Sea one for similar sized animals. A positive correlation between Hg concentration and delta(15)N occurred in all species. Increase in Hg concentration with delta(15)N was high and similar in the two Mediterranean fishes and much lower in the Black Sea species. Since this was neither related to trophic level difference between species nor to methylmercury (MeHg) concentration differences between the north-western Mediterranean and the Black Sea waters, we suggested that the higher primary production of the Black Sea induced a dilution of MeHg concentration at the base of the food webs. PMID:19201429

  4. CO2 deposition over the multi-year ice of the western Weddell Sea

    NASA Astrophysics Data System (ADS)

    Zemmelink, H. J.; Delille, B.; Tison, J. L.; Hintsa, E. J.; Houghton, L.; Dacey, J. W. H.

    2006-07-01

    Field measurements by eddy correlation (EC) indicate an average uptake of 0.6 g CO2 m-2 d-1 by the ice-covered western Weddell Sea in December 2004. At the same time, snow that covers ice floes of the western Weddell Sea becomes undersaturated with CO2 relative to the atmosphere during early summer. Gradients of CO2 from the ice to the atmosphere do not support significant diffusive fluxes and are not strong enough to explain the observed CO2 deposition. We hypothesize that the transport of air through the snow pack is controlled by turbulence and that undersaturation of CO2 is caused by biological productivity at the ice-snow and snow-atmosphere interface. The total carbon uptake by the multi-year ice zone of the western Weddell Sea in December could have been as high as 6.6 Tg C y-1.

  5. Sea-air CO2 exchange in the western Arctic coastal ocean

    NASA Astrophysics Data System (ADS)

    Evans, Wiley; Mathis, Jeremy T.; Cross, Jessica N.; Bates, Nicholas R.; Frey, Karen E.; Else, Brent G. T.; Papkyriakou, Tim N.; DeGrandpre, Mike D.; Islam, Fakhrul; Cai, Wei-Jun; Chen, Baoshan; Yamamoto-Kawai, Michiyo; Carmack, Eddy; Williams, William. J.; Takahashi, Taro

    2015-08-01

    The biogeochemical seascape of the western Arctic coastal ocean is in rapid transition. Changes in sea ice cover will be accompanied by alterations in sea-air carbon dioxide (CO2) exchange, of which the latter has been difficult to constrain owing to sparse temporal and spatial data sets. Previous assessments of sea-air CO2 flux have targeted specific subregional areas of the western Arctic coastal ocean. Here a holistic approach is taken to determine the net sea-air CO2 flux over this broad region. We compiled and analyzed an extensive data set of nearly 600,000 surface seawater CO2 partial pressure (pCO2) measurements spanning 2003 through 2014. Using space-time colocated, reconstructed atmospheric pCO2 values coupled with the seawater pCO2 data set, monthly climatologies of sea-air pCO2 differences (ΔpCO2) were created on a 0.2° latitude × 0.5° longitude grid. Sea-air CO2 fluxes were computed using the ΔpCO2 grid and gas transfer rates calculated from climatology of wind speed second moments. Fluxes were calculated with and without the presence of sea ice, treating sea ice as an imperfect barrier to gas exchange. This allowed for carbon uptake by the western Arctic coastal ocean to be assessed under existing and reduced sea ice cover conditions, in which carbon uptake increased 30% over the current 10.9 ± 5.7 Tg C (1 Tg = 1012 g) yr-1 of sea ice-adjusted exchange in the region. This assessment extends beyond previous subregional estimates in the region in an all-inclusive manner and points to key unresolved aspects that must be targeted by future research.

  6. STS-32 Earth observation of the western Coral Sea and the Great Barrier Reef

    NASA Technical Reports Server (NTRS)

    1990-01-01

    STS-32 Earth observation taken onboard Columbia, Orbiter Vehicle (OV) 102, is of the western Coral Sea and the Great Barrier Reef. The scene shows phytoplankton or algal bloom in the northwest Coral Sea. The western Coral Sea and the Great Barrier Reef waters offshore Queensland, Australia are the sites of some of the larger concentrations or 'blooms' of phytoplankton and algae in the open ocean. In the instance illustrated here, the leading edge of a probable concentration of algae or phytoplankton is seen as a light irregular line and sheen between the offshore Great Barrier Reef and the Queensland coast. Previous phytoplankton concentrations in this area have been reported by ships at sea as having formed floating mats as thick as two meters.

  7. Genetic stock identification of immature chum salmon ( Oncorhynchus keta) in the western Bering Sea, 2004

    NASA Astrophysics Data System (ADS)

    Kang, Minho; Kim, Suam; Low, Loh-Lee

    2016-03-01

    Genetic stock identification studies have been widely applied to Pacific salmon species to estimate stock composition of complex mixed-stock fisheries. In a September-October 2004 survey, 739 chum salmon ( Oncorhynchus keta) specimens were collected from 23 stations in the western Bering Sea. We determined the genetic stock composition of immature chum salmon based on the previous mitochondria DNA baseline. Each regional estimate was computed based on the conditional maximum likelihood method using 1,000 bootstrap resampling and then pooled to the major regional groups: Korea - Japan - Primorie (KJP) / Russia (RU) / Northwest Alaska (NWA) / Alaska Peninsula - Southcentral Alaska - Southeast Alaska - British Columbia - Washington (ONA). The stock composition of immature chum salmon in the western Bering Sea was a mix of 0.424 KJP, 0.421 RU, 0.116 NWA, and 0.039 ONA stocks. During the study period, the contribution of Asian chum salmon stocks gradually changed from RU to KJP stock. In addition, North American populations from NWA and ONA were small but present near the vicinity of the Russian coast and the Commander Islands, suggesting that the study areas in the western Bering Sea were an important migration route for Pacific chum salmon originating both from Asia and North America during the months of September and October. These results make it possible to better understand the chum salmon stock composition of the mixed-stock fisheries in the western Bering Sea and the stock-specific distribution pattern of chum salmon on the high-seas.

  8. Distribution of the bacteria Listeria monocytogenes in the western part of the Sea of Okhotsk

    NASA Astrophysics Data System (ADS)

    Terekhova, V. E.; Sosnin, V. A.; Buzoleva, L. S.; Shakirov, R. B.

    2010-04-01

    The Amur River’s influence on the distribution of the opportunistic bacteria Listeria monocytogenes in the western part of the Sea of Okhotsk is discussed. The presence of Listeria in the seawater, sea ice, and sediments on the northeastern Sakhalin shelf and slope supports the idea of its connection with the Amur River discharge. The hypothesis of the allochtonic parentage of L. monocytogenes in the sea’s development is proved.

  9. Coupling and feedback between Pacific sea ice and the Western Pacific pattern

    NASA Astrophysics Data System (ADS)

    Matthewman, N. J.; Magnusdottir, G.

    2010-12-01

    Coupling between sea ice variability in the Pacific basin and large scale modes of atmospheric variability are examined using weekly averaged data for December-April between 1979 and 2008. We define the large scale patterns of variability for sea ice concentration and 500hPa geopotential height over the Pacific basin and North America using Empirical Orthogonal Functions (EOFs). The patterns associated with the leading two EOFs of sea ice variability are a dipole in sea ice concentration with centers of action in the Bering Sea and Sea of Okhotsk (first EOF, ICE1), and an advance or retreat of sea ice in both seas simultaneously (second EOF, ICE2). Correlation analysis between the 500hPa geopotential height field and the principal component of the ICE2 pattern shows a large non-local response in geopotential height to changes in the ICE2 sea ice pattern. At extratropical latitudes this response in 500hPa geopotential height has two strong centers of action over the Bering Strait and Hudson Bay, with two somewhat weaker centers of action in the subtropics over the Western Pacific Ocean and the Atlantic Ocean. Further analysis suggests this response is due to sea ice in the Bering Sea region of the the ICE2 pattern, rather than the Sea of Okhotsk. This response pattern closely resembles a leading mode of 500hPa geopotential height variability, the Western Pacific (WP) pattern, indicating a coupled relationship between the WP pattern and the overall advance and retreat of sea ice in the Pacific basin. By considering intraseasonal time series of the principal components (indices) associated with the ICE2 and WP patterns, causality and coupling between the two is quantified using a stochastically forced Vector Autoregressive (VAR) model. Fitting the VAR model to observed time series for each index, we find that co-dependence between the ICE2 and WP significantly improves model performance compared with model configurations where dependence in either direction is

  10. Hydrography and biological resources in the western Bering Sea

    NASA Astrophysics Data System (ADS)

    Khen, G. V.; Basyuk, E. O.; Vanin, N. S.; Matveev, V. I.

    2013-10-01

    The variability of temperature, salinity, dissolved oxygen and nutrients (phosphate and silicate) in the west Bering Sea in the Russian Exclusive Economic Zone (REZ) since 1950 and the influence of these factors on the distribution and dynamics of hydrobionts were studied. Since 1950, the sea surface temperature has been gradually increasing, although non-significant cooling occurred in the last decade. In contrast, in the 50-200 m depth range, the temperature has been cooling. During the last 60 years, the salinity decreased by 0.30, 0.06-0.10 and 0.04 at the sea surface, at the 100-200 m layer and at the depth of 500 m, respectively, resulting in a strengthening of the vertical stability and weakening of the vertical water exchange. As a consequence, the oxygen concentrations at depths down to 1000 m decreased during this period. Phosphate and silicate concentrations increased during the last 40 years. The water exchange with the North Pacific (based on the discharge through the Kamchatka Strait) from the mid-1960s to the early 1990s was 2-3-fold higher than in the 1950s or from the mid-1990s to 2010. During the periods of weakened water exchange, the herring population sharply increased, while during periods of strengthened water exchange, pollock biomass increased. The increase of codfishes, flounders and sculpin biomass at the sea shelf during the second half of the 20th century coincided with sea surface warming. Since 2007, the westward water transport from the Aleutian Basin was almost half that during 2002-06, while the northward stream from Near Strait noticeably increased. The populations of immature chum, sockeye and chinook in the REZ declined because of their weakened input from the US zone, and these species were distributed mainly in the northern and eastern Russian waters. Taking into account the cooling since the middle of the last decade, the change in the intensity and direction of the Aleutian Low and Siberian High trends, and the westward

  11. Salinity dependence of recruitment success of the sea star Asterias rubens in the brackish western Baltic Sea

    NASA Astrophysics Data System (ADS)

    Casties, Isabel; Clemmesen, Catriona; Melzner, Frank; Thomsen, Jörn

    2015-06-01

    Salinity strongly influences development and distribution of the sea star Asterias rubens. In Kiel Fjord, located in the western Baltic Sea, A. rubens is the only echinoderm species and one of the main benthic predators controlling blue mussel ( Mytilus edulis) abundance. However, Kiel Fjord with an average salinity of about 15 is located close to the eastern distribution boundary of A. rubens in the Baltic Sea. In this study, we combined field and laboratory investigations to test whether the salinity of Kiel Fjord is high enough to enable successful development of A. rubens. Sea star eggs were fertilized in vitro, and development was monitored in the laboratory at four salinities (9, 12, 15 and 18) for 10 weeks. At a salinity of 9, development ceased prior to the blastula stage. At a salinity of 12, no larvae reached metamorphosis. At higher salinities, larvae developed normally and metamorphosed into juvenile sea stars. Abundances of A. rubens larvae and settled juveniles were also observed in Kiel Fjord and correlated to salinity values measured from March until June during 6 years (2005-2010). Results revealed high A. rubens settlement rates only in 2009, the year when salinity was the highest and least variable during the period of spawning and larval development. It appears that only years with high and stable salinities permit recruitment of A. rubens in Kiel Fjord. Projected desalination of the Baltic Sea could shift the distribution of A. rubens in the western Baltic Sea north-westwards and may lead to local extinction of a keystone species of the benthic ecosystem.

  12. Simulation of aerosol chemical compositions in the Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Chrit, Mounir; Kata Sartelet, Karine; Sciare, Jean; Marchand, Nicolas; Pey, Jorge; Sellegri, Karine

    2016-04-01

    This work aims at evaluating the chemical transport model (CTM) Polair3d of the air-quality modelling platform Polyphemus during the ChArMex summer campaigns of 2013, using ground-based measurements performed at ERSA (Cape Corsica, France), and at determining the processes controlling organic aerosol concentrations at ERSA. Simulations are compared to measurements for concentrations of both organic and inorganic species, as well as the ratio of biogenic versus anthropogenic particles, and organic aerosol properties (oxidation state). For inorganics, the concentrations of sulphate, sodium, chloride, ammonium and nitrate are compared to measurements. Non-sea-salt sulphate and ammonium concentrations are well reproduced by the model. However, because of the geographic location of the measurement station at Cape Corsica which undergoes strong wind velocities and sea effects, sea-salt sulphate, sodium, chloride and nitrate concentrations are strongly influenced by the parameterizations used for sea-salt emissions. Different parameterizations are compared and a parameterization is chosen after comparison to sodium measurements. For organics, the concentrations are well modelled when compared to experimental values. Anthropogenic particles are influenced by emission of semi-volatile organic compounds (SVOC). Measurements allow us to refine the estimation of those emissions, which are currently missing in emission inventories. Although concentrations of biogenic particles are well simulated, the organic chemical compounds are not enough oxidised in the model. The observed oxidation state of organics shows that the oligomerisation of pinonaldehyde was over-estimated in Polyphemus. To improve the oxidation property of organics, the formation of extremely low volatile organic compounds from autoxidation of monoterpenes is added to Polyphemus, using recently published data from chamber experiments. These chemical compounds are highly oxygenated and are formed rapidly, as first

  13. Vortices generation mechanisms in North western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Fraunie, P.; Redondo, J. M.; Schaeffer, A.; Molcard, A.; Forget, P.; Garreau, P.

    2012-04-01

    Mesoscale eddies have been observed in Northwestern Mediterranean Sea from satellites, RV cruises and more recently using HF radars. Different non linear mechanisms have been identified and investigated using process oriented high resolution numerical modelling. In particular, wind induced inertial motion and baroclinic instability cases have been illustrated and documented. Statistics of vortices occurence allow a better accounting for coherent structures for pollutants and nutriments dispersion and retention. Acknowledgements : GIRAC project (FUI - CG83 -TPM), ESA, HYMEX programme

  14. The Cretaceous Polar and Western Interior seas: paleoenvironmental history and paleoceanographic linkages

    NASA Astrophysics Data System (ADS)

    Schröder-Adams, Claudia

    2014-03-01

    This study reviews the Cretaceous histories of the Polar and Western Interior seas as recorded in the Canadian High Arctic Sverdrup Basin, Beaufort-Mackenzie Basin of northwest Canada and Western Canadian Foreland Basin. Newly emerging stratigraphic, paleoclimatic and paleoenvironmental interpretations from the polar realm allow for a fresh look at the response of this oceanic system to global climatic trends and sea-level histories over 35 Ma. Sverdrup basin localities on Axel Heiberg and Ellef Ringnes islands represent shelf to slope environments that contrasted with the shallow water and low gradient settings of the Canadian Western Interior Sea. Both marine systems, connected throughout Aptian to Maastrichtian time, responded to global transgressive-regressive cycles resulting in dynamic paleogeographic changes. The upper Aptian to Campanian succession of the Polar Sea shows at least two unconformable boundaries; one at the Albian/Cenomanian transition and another within the upper Cenomanian. The shallow basin setting and in particular the forebulge and backbulge settings of the Western Canadian Foreland Basin are characterized by multiple erosional surfaces throughout the Cretaceous succession. The Upper Albian disconformity is widely discernible close to the entrance of the Western Interior Sea to the Polar Sea. This suggests a short-lived closure of the latest Albian Mowry Sea that might have been responsible for the large loss of benthic foraminiferal species at this time. Several oceanic anoxic events are documented in these basins representing their response to global climate dynamics. During the Late Cretaceous temperature maximum benthic foraminiferal communities were severely restricted by bottom water hypoxia in both basins. A stratified water column might have been the result of increased freshwater runoff under warm, humid conditions. These conditions supported vegetation up into the polar latitudes that added abundant organic matter to marine shelf

  15. Abrupt climate shift in the Western Mediterranean Sea

    PubMed Central

    Schroeder, K.; Chiggiato, J.; Bryden, H. L.; Borghini, M.; Ben Ismail, S.

    2016-01-01

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected. PMID:26965790

  16. Abrupt climate shift in the Western Mediterranean Sea.

    PubMed

    Schroeder, K; Chiggiato, J; Bryden, H L; Borghini, M; Ben Ismail, S

    2016-01-01

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected. PMID:26965790

  17. Abrupt climate shift in the Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Schroeder, K.; Chiggiato, J.; Bryden, H. L.; Borghini, M.; Ben Ismail, S.

    2016-03-01

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected.

  18. No Evidence of Metabolic Depression in Western Alaskan Juvenile Steller Sea Lions (Eumetopias jubatus)

    PubMed Central

    Hoopes, Lisa A.; Rea, Lorrie D.; Christ, Aaron; Worthy, Graham A. J.

    2014-01-01

    Steller sea lion (Eumetopias jubatus) populations have undergone precipitous declines through their western Alaskan range over the last four decades with the leading hypothesis to explain this decline centering around changing prey quality, quantity, or availability for this species (i.e., nutritional stress hypothesis). Under chronic conditions of reduced food intake sea lions would conserve energy by limiting energy expenditures through lowering of metabolic rate known as metabolic depression. To examine the potential for nutritional stress, resting metabolic rate (RMR) and body composition were measured in free-ranging juvenile Steller sea lions (N = 91) at three distinct geographical locations (Southeast Alaska, Prince William Sound, Central Aleutian Islands) using open-flow respirometry and deuterium isotope dilution, respectively. Average sea lion RMR ranged from 6.7 to 36.2 MJ d−1 and was influenced by body mass, total body lipid, and to a lesser extent, ambient air temperature and age. Sea lion pups captured in the Aleutian Islands (region of decline) had significantly greater body mass and total body lipid stores when compared to pups from Prince William Sound (region of decline) and Southeast Alaska (stable region). Along with evidence of robust body condition in Aleutian Island pups, no definitive differences were detected in RMR between sea lions sampled between eastern and western populations that could not be accounted for by higher percent total body lipid content, suggesting that that at the time of this study, Steller sea lions were not experiencing metabolic depression in the locations studied. PMID:24416394

  19. Climate change and the Baltic Sea action plan: Model simulations on the future of the western Baltic Sea

    NASA Astrophysics Data System (ADS)

    Friedland, René; Neumann, Thomas; Schernewski, Gerald

    2012-12-01

    In this study we apply the model ERGOM to simulate the consequences of Climate Change as well as the combination of Climate Change with nutrient load reductions according to the Baltic Sea Action Plan (BSAP) on the Baltic Sea ecosystem. According to the simulations, Climate Change will cause an increase of the water temperature up to 3 K and a salinity decrease of 1.5 PSU until 2100. However, the implementation of the BSAP will have much stronger effects on the ecosystem. The model suggests that the western Baltic Sea will shift from a nitrogen (N) towards a phosphorus (P) limited system. As a consequence, N-fixation will strongly decrease. The same applies to nutrient-concentrations in winter, denitrification as well as detritus and chlorophyll concentrations in summer. The availability of N in summer, the Secchi depth and the oxygen saturation will increase. Our simulations suggest that the full implementation of the BSAP will cause imbalances in the Baltic Sea over decades before a new system state will be reached. Our results indicate that the Secchi depth alone is not a suitable indicator for the state of eutrophication. Concerning the Water Framework Directive (WFD), Climate Change might alter gradients and concentrations, e.g. of salinity, and in return this might require a re-definition of the WFD typology or a spatial shift of the surface water types, e.g. in Germany. The western Baltic Sea is strongly controlled by regional nutrient loads. Climate Change has only a limited effect on loads in the western Baltic. A re-definition of reference conditions and a good status because of Climate Change seems not necessary.

  20. A Sea-Surface Radiation Data Set for Climate Applications in the Tropical Western Pacific and South China Sea

    NASA Technical Reports Server (NTRS)

    Chou, Ming-Dah; Chan, Pui-King; Yan, Michael M.-H.

    2000-01-01

    The sea-surface shortwave and longwave radiative fluxes have been retrieved from the radiances measured by Japan's Geostationary Meteorological Satellite 5. The surface radiation data set covers the domain 40S-40N and 90E-170W. The temporal resolution is 1 day, and the spatial resolution is 0.5 deg x 0.5 deg latitude-longitude. The retrieved surface radiation have been validated with the radiometric measurements at the Atmospheric Radiation Measuring (ARM) site on Manus island in the equatorial western Pacific for a period of 15 months. It has also been validated with the measurements at the radiation site on Dungsha island in the South China Sea during the South China Sea Monsoon Experiment (SCSMEX) Intensive Observing Period (May and June 1998). The data set is used to study the effect of El Nino and East Asian Summer monsoon on the heating of the ocean in the tropical western Pacific and the South China Sea. Interannual variations of clouds associated with El Nino and the East Asian Summer monsoon have a large impact on the radiative heating of the ocean. It has been found that the magnitude of the interannual variation of the seasonal mean surface radiative heating exceeds 40 W/sq m over large areas. Together with the Clouds and the Earth's Radiant Energy System (CERES) shortwave fluxes at top of the atmosphere and the radiative transfer calculations of clear-sky fluxes, this surface radiation data set is also used to study the impact of clouds on the solar heating of the atmosphere. It is found that clouds enhance the atmospheric solar heating by approx. 20 W/sq m in the tropical western Pacific and the South China Sea. This result is important for evaluating the accuracy of solar flux calculations in clear and cloudy atmospheres.

  1. Early Miocene Tectonic Activity in the western Ross Sea (Antarctica)

    NASA Astrophysics Data System (ADS)

    Sauli, C.; Sorlien, C. C.; Busetti, M.; Geletti, R.; De Santis, L.

    2012-12-01

    In the framework of the Rossmap Italian PNRA work objectives to compile extended and revised digital maps of the main unconformities in Ross Sea, Antarctica, much additional seismic reflection data, that were not available to previous ANTOSTRAT compilation, were incorporated into a new ROSSMAP interpretation. The correlation across almost all of Ross Sea, from DSDP Site 270 and Site 272 in Eastern Basin to northern Victoria Land Basin, of additional early Miocene and late Oligocene horizons that were not part of ANTOSTRAT allows interpretations to be made of fault activity and glacial erosion or deposition at a finer time resolution. New conclusions include that extensional or transtensional fault activity within the zone between Victoria Land Basin and Northern Basin, initiated by 23 Ma or earlier, and continued after 18 Ma. Steep parallel-striking faults in southern Victoria Land Basin display both reverse and normal separation of 17.5 Ma (from Cape Roberts Program-core 1) and post-16 Ma horizons, suggesting an important strike-slip component. This result may be compared with published papers that proposed post-17 Ma extension in southern Victoria Land Basin, 16-17 Ma extension in the AdareTrough, north of the Ross Sea continental shelf, but no Miocene extension affecting the Northern Basin (Granot et al., 2010). Thus, our evidence for extension through the early Miocene is significant to post-spreading tectonic models. Reference Granot R., Cande S. C., Stock J. M., Davey F. J. and Clayton R. W. (2010) Postspreading rifting in the Adare Basin, Antarctica: Regional tectonic consequences. Geochem. Geophys. Geosyst., 8, Q08005, doi:10.1029/2010GC003105.

  2. Subduction initiation, recycling of Alboran lower crust, and intracrustal emplacement of subcontinental lithospheric mantle in the Westernmost Mediterranean

    NASA Astrophysics Data System (ADS)

    Varas-Reus, María Isabel; Garrido, Carlos J.; Bosch, Delphine; Marchesi, Claudio; Hidas, Károly; Booth-Rea, Guillermo; Acosta-Vigil, Antonio

    2015-04-01

    Unraveling the tectonic settings and processes involved in the annihilation of subcontinental mantle lithosphere is of paramount importance for our understanding of the endurance of continents through Earth history. Unlike ophiolites -- their oceanic mantle lithosphere counterparts -- the mechanisms of emplacement of the subcontinental mantle lithosphere in orogens is still poorly known. The emplacement of subcontinental lithospheric mantle peridotites is often attributed to extension in rifted passive margins or continental backarc basins, accretionary processes in subduction zones, or some combination of these processes. One of the most prominent features of the westernmost Mediterranean Alpine orogenic arcs is the presence of the largest outcrops worldwide of diamond facies, subcontinental mantle peridotite massifs; unveiling the mechanisms of emplacement of these massifs may provide important clues on processes involved in the destruction of continents. The western Mediterranean underwent a complex Alpine evolution of subduction initiation, slab fragmentation, and rollback within a context of slow convergence of Africa and Europe In the westernmost Mediterranean, the alpine orogeny ends in the Gibraltar tight arc, which is bounded by the Betic, Rif and Tell belts that surround the Alboran and Algero-Balearic basins. The internal units of these belts are mostly constituted of an allochthonous lithospheric domain that collided and overthrusted Mesozoic and Tertiary sedimentary rocks of the Mesozoic-Paleogene, South Iberian and Maghrebian rifted continental paleomargins. Subcontinental lithospheric peridotite massifs are intercalated between polymetamorphic internal units of the Betic (Ronda, Ojen and Carratraca massifs), Rif (Beni Bousera), and Tell belts. In the Betic chain, the internal zones of the allochthonous Alboran domain include, from bottom to top, polymetamorphic rock of the Alpujarride and Malaguide complexes. The Ronda peridotite massif -- the

  3. Western Pacific Air-Sea Interaction Study (W-PASS), Introduction and Highlights (Invited)

    NASA Astrophysics Data System (ADS)

    Tsuda, A.

    2010-12-01

    Western Pacific Air-Sea Interaction Study (W-PASS), Introduction and Highlights Atsushi Tsuda Atmosphere and Ocean Research Institute, The University of Tokyo In the western Pacific (WESTPAC) region, dust originating from Asian and Australian arid regions to the North and South Pacific, biomass burning emissions from the Southeast Asia to sub-tropical Pacific, and other anthropogenic substances are transported regionally and globally to affect cloud and rainfall patterns, air quality, and radiative budgets downwind. Deposition of these compounds into the Asian marginal seas and onto the Pacific Ocean influence surface primary productivity and species composition. In the WESTPAC region, subarctic, subtropical oceans and marginal seas are located relatively narrow latitudinal range and these areas are influenced by the dust and anthropogenic inputs. Moreover, anthropogenic emission areas are located between the arid region and the oceans. The W-PASS (Western Pacific Air-Sea interaction Study) project has been funded for 5 years as a part of SOLAS-Japan activity in the summer of 2006. We aim to resolve air-sea interaction through field observation studies mainly using research vessels and island observatories over the western Pacific. We have carried out 5 cruises to the western North Pacific focusing on air-sea interactions. Also, an intensive marine atmospheric observation including direct atmospheric deposition measurement was accomplished by a dozen W-PASS research groups at the NIES Atmospheric and Aerosol Monitoring Station of Cape Hedo in the northernmost tip of the Okinawa main Island facing the East China Sea in the spring 2008. A few weak Kosa (dust) events, anthropogenic air outflows, typical local air and occupation of marine background air were identified during the campaign period. The W-PASS has four research groups mainly focusing on VOC emissions, air-sea gas exchange processes, biogeochemical responses to dust depositions and its modeling. We also

  4. Amount and distribution of neustonic micro-plastic off the western Sardinian coast (Central-Western Mediterranean Sea).

    PubMed

    de Lucia, Giuseppe Andrea; Caliani, Ilaria; Marra, Stefano; Camedda, Andrea; Coppa, Stefania; Alcaro, Luigi; Campani, Tommaso; Giannetti, Matteo; Coppola, Daniele; Cicero, Anna Maria; Panti, Cristina; Baini, Matteo; Guerranti, Cristiana; Marsili, Letizia; Massaro, Giorgio; Fossi, Maria Cristina; Matiddi, Marco

    2014-09-01

    A plethora of different sampling methodologies has been used to document the presence of micro-plastic fragments in sea water. European Marine Strategy suggests to improve standard techniques to make future data comparable. We use Manta Trawl sampling technique to quantify abundance and distribution of micro-plastic fragments in Sardinian Sea (Western Mediterranean), and their relation with phthalates and organoclorine in the neustonic habitat. Our results highlight a quite high average plastic abundance value (0.15 items/m(3)), comparable to the levels detected in other areas of the Mediterranean. "Site" is the only factor that significantly explains the differences observed in micro-plastic densities. Contaminant levels show high spatial and temporal variation. In every station, HCB is the contaminant with the lowest concentration while PCBs shows the highest levels. This work, in line with Marine Strategy directives, represents a preliminary study for the analysis of plastic impact on marine environment of Sardinia. PMID:24776304

  5. First record of a Vestimentifera (Polychaeta: Siboglinidae) from chemosynthetic habitats in the western Mediterranean Sea—Biogeographical implications and future exploration

    NASA Astrophysics Data System (ADS)

    Hilário, A.; Comas, M. C.; Azevedo, L.; Pinheiro, L.; Ivanov, M. K.; Cunha, M. R.

    2011-02-01

    A new population of vestimentiferan tubeworms was discovered during a recent expedition to a mud volcano field in the Alboran Sea, western Mediterranean Sea. Morphological data and mitochondrial cytochrome-c-oxidase subunit 1 (COI) sequences show that the Alboran tubeworm is essentially identical to Lamellibrachia sp. found in the eastern Mediterranean. This is the first record of a vestimentiferan species in the western basin of the Mediterranean, an area with direct connection to the Atlantic via the Strait of Gibraltar and therefore of great importance to the study of distributional patterns and evolution of Mediterranean species. We examine the current hypotheses on the biogeographic distribution of vestimentiferan species in the eastern Atlantic and Mediterranean Sea and conclude that independently of when Lamellibrachia colonized the Mediterranean, neither the present hydrological settings of both Mediterranean Sea and Atlantic Ocean, nor vestimentiferans reproductive biology are impeditive to the presence of the Mediterranean species of Lamellibrachia in the NE Atlantic. The West African and Lusitanian margins are the most likely places to find living populations of this species in the NE Atlantic.

  6. Tectonics of the Western Betics: the role of E-W strike slip fault corridors

    NASA Astrophysics Data System (ADS)

    Frasca, Gianluca; Gueydan, Frédéric; Brun, Jean-Pierre; Célérier, Bernard

    2014-05-01

    The tectonic origin of the arcuate Betic-Rif orogenic belt that surrounds the Alboran Sea at the western tip of the Mediterranean Sea remains debated. Here, we investigate the tectonic units cropping out in the Western Betics (Malaga region, Southern Spain) with the main goal of reconstructing the Oligo-Miocene evolution of the area. New structural data and geological mapping together with available data allow us to identify the main structural features of the area. Deformation is found to be extremely diffused but two E-W elongated tectonic blocks with different lithological composition are outlined by marked E-W dextral strike-slip corridors ending up in horse-tail splays. These E-W strike slip corridors are responsible for late Miocence tectonics of both the internal and external zones of the Betic Cordillera.

  7. Eastern-western Arctic sea ice analysis, 1993

    SciTech Connect

    1993-12-31

    This publication is the 20th edition of the annual Arctic sea-ice atlases prepared by the JIC. The atlas contains weekly charts depicting Northern Hemisphere ice conditions and extent. The significant use of high resolution satellite imagery, combined with valuable ice reconnaissance data from various sources, has greatly improved the accuracy of these analyses. The purpose of this atlas is to provide the user with reliable weekly hemispheric ice analyses. These charts are prepared by experienced Navy and NOAA ice analysts who plot and evaluate numerous data sources: (a) Conventional shore station, ship, and aerial reconnaissance observations; and (b) Satellite data from various sensors. Table I, located on the inside back cover, lists these sensors and their availability. A final product is synthesized from the inputs described above. When insufficient data is available, estimated boundaries are plotted, using meteorological data and computer generated ice drift vectors to determine estimated ice position.

  8. Structure of the central Terror Rift, western Ross Sea, Antarctica

    USGS Publications Warehouse

    Hall, Jerome; Wilson, Terry; Henrys, Stuart

    2007-01-01

    The Terror Rift is a zone of post-middle Miocene faulting and volcanism along the western margin of the West Antarctic Rift System. A new seismic data set from NSF geophysical cruise NBP04-01, integrated with the previous dataset to provide higher spatial resolution, has been interpreted in this study in order to improve understanding of the architecture and history of the Terror Rift. The Terror Rift contains two components, a structurally-controlled rollover anticlinal arch intruded by younger volcanic bodies and an associated synclinal basin. Offsets and trend changes in fault patterns have been identified, coincident with shifts in the location of depocenters that define rift sub-basins, indicating that the Terror Rift is segmented by transverse structures. Multiple phases of faulting all post-date 17 Ma, including faults cutting the seafloor surface, indicating Neogene rifting and possible modern activity.

  9. Shifts in nursery habitat utilization by 0-group plaice in the western Dutch Wadden Sea

    NASA Astrophysics Data System (ADS)

    Freitas, Vânia; Witte, Johannes I. J.; Tulp, Ingrid; van der Veer, Henk W.

    2016-05-01

    Since the mid-1980s major changes in spatiotemporal patterns of distribution of juvenile plaice have occurred in the Wadden Sea. Large juvenile (I- and II-group) plaice have almost completely disappeared from the intertidal flats in spring and summer and are no longer found in subtidal and tidal channels in autumn, consistent with an offshore movement reported in the nearshore coastal zone. In this paper we evaluate the present functional importance of the western Wadden Sea as a nursery for young-of-the-year (0-group) plaice and the changes over time compared to the mid-1980s period by analyzing abundance, growth and distribution patterns in various intertidal, subtidal and tidal channel areas. Spatiotemporal changes in habitat use were observed compared to 1986 based on a depth-stratified sampling repeated two decades later, in 2009. Present results showed that the utilization of the western Wadden Sea has greatly changed, with changing patterns of depth distribution of the 0-group. Settlement of 0-group plaice still occurred in the intertidal, however, shortly thereafter, they moved to deeper waters. Such shift in habitat use did not seem to have affected growth rates. Overall, it seems that the western Wadden Sea can still support young-of-the-year plaice population and in spite of changes in habitat use, the functional importance of the area for this group has not been affected.

  10. Hydrodynamic modelling of coastal seas: the role of tidal dynamics in the Messina Strait, Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Cucco, Andrea; Quattrocchi, Giovanni; Olita, Antonio; Fazioli, Leopoldo; Ribotti, Alberto; Sinerchia, Matteo; Tedesco, Costanza; Sorgente, Roberto

    2016-07-01

    This work explores the importance of considering tidal dynamics when modelling the general circulation in the Messina Strait, a narrow passage connecting the Tyrrhenian and the Ionian subbasins in the Western Mediterranean Sea. The tides and the induced water circulation in this Strait are among the most intense oceanographic processes in the Mediterranean Sea. The quantification of these effects can be particularly relevant for operational oceanographic systems aimed to provide short-term predictions of the main hydrodynamics in the Western Mediterranean subbasins. A numerical approach based on the use of a high-resolution hydrodynamic model was followed to reproduce the tides propagation and the wind-induced and thermohaline water circulation within the Strait and in surrounding areas. A set of numerical simulations was carried out to quantify the role of the Strait dynamics on the larger-scale water circulation. The obtained results confirmed the importance of a correct representation of the hydrodynamics in the Messina Strait even when focusing on predicting the water circulation in the external sea traits. In fact, model results show that tidal dynamics deeply impact the reproduction of the instantaneous and residual circulation pattern, waters thermohaline properties and transport dynamics both inside the Messina Strait and in the surrounding coastal and open waters.

  11. High-resolution IP25-based reconstruction of sea-ice variability in the western North Pacific and Bering Sea during the past 18,000 years

    NASA Astrophysics Data System (ADS)

    Méheust, Marie; Stein, Ruediger; Fahl, Kirsten; Max, Lars; Riethdorf, Jan-Rainer

    2016-04-01

    Due to its strong influence on heat and moisture exchange between the ocean and the atmosphere, sea ice is an essential component of the global climate system. In the context of its alarming decrease in terms of concentration, thickness and duration, understanding the processes controlling sea-ice variability and reconstructing paleo-sea-ice extent in polar regions have become of great interest for the scientific community. In this study, for the first time, IP25, a recently developed biomarker sea-ice proxy, was used for a high-resolution reconstruction of the sea-ice extent and its variability in the western North Pacific and western Bering Sea during the past 18,000 years. To identify mechanisms controlling the sea-ice variability, IP25 data were associated with published sea-surface temperature as well as diatom and biogenic opal data. The results indicate that a seasonal sea-ice cover existed during cold periods (Heinrich Stadial 1 and Younger Dryas), whereas during warmer intervals (Bølling-Allerød and Holocene) reduced sea ice or ice-free conditions prevailed in the study area. The variability in sea-ice extent seems to be linked to climate anomalies and sea-level changes controlling the oceanographic circulation between the subarctic Pacific and the Bering Sea, especially the Alaskan Stream injection though the Aleutian passes.

  12. Hierarchical modeling of bycatch rates of sea turtles in the western North Atlantic

    USGS Publications Warehouse

    Gardner, B.; Sullivan, P.J.; Epperly, S.; Morreale, S.J.

    2008-01-01

    Previous studies indicate that the locations of the endangered loggerhead Caretta caretta and critically endangered leatherback Dermochelys coriacea sea turtles are influenced by water temperatures, and that incidental catch rates in the pelagic longline fishery vary by region. We present a Bayesian hierarchical model to examine the effects of environmental variables, including water temperature, on the number of sea turtles captured in the US pelagic longline fishery in the western North Atlantic. The modeling structure is highly flexible, utilizes a Bayesian model selection technique, and is fully implemented in the software program WinBUGS. The number of sea turtles captured is modeled as a zero-inflated Poisson distribution and the model incorporates fixed effects to examine region-specific differences in the parameter estimates. Results indicate that water temperature, region, bottom depth, and target species are all significant predictors of the number of loggerhead sea turtles captured. For leatherback sea turtles, the model with only target species had the most posterior model weight, though a re-parameterization of the model indicates that temperature influences the zero-inflation parameter. The relationship between the number of sea turtles captured and the variables of interest all varied by region. This suggests that management decisions aimed at reducing sea turtle bycatch may be more effective if they are spatially explicit. ?? Inter-Research 2008.

  13. Sedimentation in the western Arabian Sea the role of coastal and open-ocean upwelling

    NASA Astrophysics Data System (ADS)

    Rixen, Tim; Haake, Birgit; Ittekkot, Venugopalan

    Monsoon-induced coastal and open-ocean upwelling explain 84% of the variations of the organic carbon fluxes measured in the deep western Arabian Sea. In this paper, sea-level measurements, satellite-derived wind speeds, sea surface temperatures, and nutrient profiles are used to discern the relative importance of these factors on fluxes measured during nine years of continuous sediment trap deployments. This exercise shows: (i) the increase in fluxes observed during the initial stages of the SW monsoons are caused by open-ocean upwelling, which develops faster than the coastal upwelling; (ii) coastal upwelling triggers diatom blooms from nutrients from subsurface water and sediment resuspension and, more importantly, by injecting resting stages of diatoms back into the euphotic zone; (iii) silica depletion resulting from diatom blooms in laterally advecting water masses leads to a replacement of diatoms by other nitrate-limited organisms; (iv) organic carbon fluxes to the deep Arabian Sea increase in response to an intensification of both coastal and open-ocean upwelling; weak coastal upwelling and strong open-ocean upwelling also increase organic carbon fluxes. The varying dominance of their influence is reflected in the timing and the composition of the peak fluxes; (v) the link between organic carbon flux and monsoon strength is non-linear probably due to changes in the surface currents and to vigorous turbulence in the surface water during strong SW monsoons. These processes could reduce the organic carbon flux in the western Arabian Sea by about 65%.

  14. A possible 90 - 100 MYBP magnetic anomaly in the western-most Philippine Sea

    NASA Astrophysics Data System (ADS)

    Lee, C.; Cho, Y.; Liang, C.; Lai, W.

    2012-12-01

    10 years ago, Tamaki's team offered the deep-towed magnetometer and my team provided the R/V Ocean Research No. 1. We jointly conducted a deep-towed magnetic survey in the western-most Philippine Sea (also called the Huatung Basin). The results show the magnetic age could be either as the previous reported 35- 45 MYBP or as the ambiguous 90 - 100 MYBP. 10 year later, a Taiwan-USA co-operation on the understanding of Taiwan Mountain Building processes (the TAIGER project) has shown that this area and the east contain a huge area of submarine volcanoes and at least in 4-5 regions showing the overlapping spreading ridges, similar like today's East Pacific Spreading Center of higher spreading rate. This is interpreted as the 45 MYBP when the Pacific Plate changed its motion from N to NW and the massive volcanic activity accompany the motion change. Before the change, it is possible to have the Kula Plate in the east and the Tethys Sea in the west crossing the Pacific and Indian oceans at about 90 - 100 MYBP. The Taiwan Central Range and China Fuzhian Massive Range support this idea. At about 45 - 65 MYBP, the Himalaya and Alps experienced the head-to-head collision and the mountains started to push up. In the mean time, the Kula Plate disappeared and the Tethys Sea diminished its size. These could trigger the Western Pacific trench-arc-backarc systems. The systems continue to evolve up to today. The Gagua Ridge, located along the E longitude 123 degree, act as a dam to prevent the sediment further deposits into the east side of the Philippine Sea. The new OBS refraction and earthquake data show the east side of the Philippine Sea is subducting into the west side, the western-most Philippine Sea. The previous magnetic lineation, fossil radiolarian and metamorphosed igneous ages found surround the basin support that the western-most Philippine Sea may be the last remaining Tethys Sea in the Pacific.

  15. Neogene Development of the Terror Rift, western Ross Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Sauli, C.; Sorlien, C. C.; Busetti, M.; De Santis, L.; Wardell, N.; Henrys, S. A.; Geletti, R.; Wilson, T. J.; Luyendyk, B. P.

    2015-12-01

    Terror Rift is a >300 km-long, 50-70 km-wide, 14 km-deep sedimentary basin at the edge of the West Antarctic Rift System, adjacent to the Transantarctic Mountains. It is cut into the broader Victoria Land Basin (VLB). The VLB experienced 100 km of mid-Cenozoic extension associated with larger sea floor spreading farther north. The post-spreading (Neogene) development of Terror Rift is not well understood, in part because of past use of different stratigraphic age models. We use the new Rossmap seismic stratigraphy correlated to Cape Roberts and Andrill cores in the west and to DSDP cores in the distant East. This stratigraphy, and new fault interpretations, was developed using different resolutions of seismic reflection data included those available from the Seismic Data Library System. Depth conversion used a new 3D velocity model. A 29 Ma horizon is as deep as 8 km in the south, and a 19 Ma horizon is >5 km deep there and 4 km-deep 100 km farther north. There is a shallower northern part of Terror Rift misaligned with the southern basin across a 50 km right double bend. It is bounded by steep N-S faults down-dropping towards the basin axis. Between Cape Roberts and Ross Island, the Oligocene section is also progressively-tilted. This Oligocene section is not imaged within northern Terror Rift, but the simplest hypothesis is that some of the Terror Rift-bounding faults were active at least during Oligocene through Quaternary time. Many faults are normal separation, but some are locally vertical or even reverse-separation in the upper couple of km. However, much of the vertical relief of the strata is due to progressive tilting (horizontal axis rotation) and not by shallow faulting. Along the trend of the basin, the relief alternates between tilting and faulting, with a tilting margin facing a faulted margin across the Rift, forming asymmetric basins. Connecting faults across the basin form an accommodation zone similar to other oblique rifts. The Neogene basin is

  16. Total Organic Carbon Distribution and Bacterial Cycling Across A Geostrophic Front In Mediterranean Sea. Implications For The Western Basin Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Sempere, R.; van Wambeke, F.; Bianchi, M.; Dafner, E.; Lefevre, D.; Bruyant, F.; Prieur, L.

    We investigated the dynamic of the total organic carbon (TOC) pool and the role it played in the carbon cycle during winter 1997-1998 in the Almeria-Oran jet-front (AOF) system resulting from the spreading of Atlantic surface water through the Gibraltar Strait in the Alboran Sea (Southwestern Mediterranean Sea). We determined TOC by using high temperature combustion technique (HTC) and bacterial produc- tion (BP; via [3H] leucine incorporation) during two legs in the frontal area. We also estimated labile TOC (l-TOC) and bacterial growth efficiency (BGE) by performing TOC biodegradation experiments on board during the cruise whereas water column semi-labile (sl-TOC), and refractory-TOC were determined from TOC profile exami- nation. These results are discussed in relation with current velocity measured by using accoustic doppler current profiler (ADCP). Lowest TOC stocks (6330-6853 mmol C m-2) over 0-100 m were measured in the northern side of the geostrophic Jet which is also the highest dynamic area (horizontal speed of 80 cm s-1 in the first 100 m di- rected eastward). Our results indicated variable turnover times of sl-TOC across the Jet-Front system, which might be explained by different coupling of primary produc- tion and bacterial production observed in these areas. We also estimated TOC and sl-TOC transports within the Jet core off the Alboran Sea as well as potential CO2 production through bacterial respiration produced from sl-TOC assimilation by het- erotrophic bacteria.

  17. Sea surface temperature and salinity seasonal changes in the western Solomon and Bismarck Seas

    NASA Astrophysics Data System (ADS)

    Delcroix, Thierry; Radenac, Marie-Hélène; Cravatte, Sophie; Alory, Gaël.; Gourdeau, Lionel; Léger, Fabien; Singh, Awnesh; Varillon, David

    2014-04-01

    We analyze mean and seasonal change of Sea Surface Temperature (SST) and Salinity (SSS) in the Solomon and Bismarck Seas, using 1977-2009 in situ data collected from Voluntary Observing Ships. Covariability of these two variables with surface wind, altimeter-derived and model-derived horizontal currents, precipitation, and Sepik River discharge are examined. SST and SSS show large annual oscillations in the Solomon Sea, with the coldest and saltiest waters occurring in July/August mainly due to horizontal advection. In contrast, they show large semiannual oscillations in the Bismarck Sea. There, the coldest and saltiest waters happen in January/February, when the northwest monsoon winds drive coastal upwelling, and in July/August, when the New Guinea Coastal Current advects cold and high-salinity waters from the Solomon Sea through Vitiaz Strait. The low SSS values observed in April/May, stuck between the January/February and July/August SSS maxima, are further enhanced by the Sepik River discharge annual maximum. A high-resolution model strengthens the conclusions we derive from observations. The impacts of ENSO on SST and SSS are also discussed with, for instance, saltier-than-average and fresher-than-average waters during the 2002-2003 El Niño and 2007-2008 La Niña, respectively.

  18. Tsunami early warning system for the western coast of the Black Sea

    NASA Astrophysics Data System (ADS)

    Ionescu, Constantin; Partheniu, Raluca; Cioflan, Carmen; Constantin, Angela; Danet, Anton; Diaconescu, Mihai; Ghica, Daniela; Grecu, Bogdan; Manea, Liviu; Marmureanu, Alexandru; Moldovan, Iren; Neagoe, Cristian; Radulian, Mircea; Raileanu, Victor; Verdes, Ioan

    2014-05-01

    The Black Sea area is liable to tsunamis generation and the statistics show that more than twenty tsunamis have been observed in the past. The last tsunami was observed on 31st of March 1901 in the western part of the Black Sea, in the Shabla area. An earthquake of magnitude generated at a depth of 15 km below the sea level , triggered tsunami waves of 5 m height and material losses as well. The oldest tsunami ever recorded close to the Romanian shore-line dates from year 104. This paper emphasises the participation of The National Institute for Earth Physics (NIEP) to the development of a tsunami warning system for the western cost of the Black Sea. In collaboration with the National Institute for Marine Geology and Geoecology (GeoEcoMar), the Institute of Oceanology and the Geological Institute, the last two belonging to the Bulgarian Academy of Science, NIEP has participated as partner, to the cross-border project "Set-up and implementation of key core components of a regional early-warning system for marine geohazards of risk to the Romanian-Bulgarian Black Sea coastal area - MARINEGEOHAZARDS", coordinated by GeoEcoMar. The main purpose of the project was the implementation of an integrated early-warning system accompanied by a common decision-support tool, and enhancement of regional technical capability, for the adequate detection, assessment, forecasting and rapid notification of natural marine geohazards for the Romanian-Bulgarian Black Sea cross-border area. In the last years, NIEP has increased its interest on the marine related hazards, such as tsunamis and, in collaboration with other institutions of Romania, is acting to strengthen the cooperation and data exchanges with institutions from the Black Sea surrounding countries which already have tsunami monitoring infrastructures. In this respect, NIEP has developed a coastal network for marine seismicity, by installing three new seismic stations in the coastal area of the Black Sea, Sea Level Sensors

  19. Biweekly Sea Surface Temperature over the South China Sea and its association with the Western North Pacific Summer Monsoon

    NASA Astrophysics Data System (ADS)

    Vaid, B. H.

    2015-10-01

    The association of the biweekly intraseasonal (BWI) oscillation in the Sea Surface Temperature (SST) over the South China Sea (SCS) and the Western North Pacific Summer Monsoon is authenticated using version 4 the Tropical Rainfall Measuring Mission Microwave Imager data (SST and rain) and heat fluxes from Ocean Atmosphere Flux project data during 1998-2012. The results suggest that the SCS involves ocean-atmosphere coupling on biweekly timescales. The positive biweekly SST anomalies lead the rain anomalies over the SCS by 3 days, with a significant correlation coefficient (r = 0.6, at 99 % significance levels) between the SST-rain anomalies. It is evident from lead/lag correlation between biweekly SST and zonal wind shear that warm ocean surface induced by wind shear may contribute to a favorable condition of the convective activity over the SCS. The present study suggests that ocean-to-atmospheric processes induced by the BWI oscillation in the SCS SST results in enhanced sea level pressure and surface shortwave radiation flux during the summer monsoon. Besides, it is observed that the SCS BWI oscillation in the changes of SST causes a feedback in the atmosphere by modifying the atmospheric instability. This suggests that the active/break biweekly cycle of the SST over the SCS is related by sea level pressure, surface heat fluxes and atmospheric instability. The potential findings here indicate that the biweekly SST over the SCS play an important role in the eastward and the southward propagation of the biweekly anomalies in the Western North Pacific.

  20. Causes and consequences of hypoxia on the Western Black Sea Shelf

    NASA Astrophysics Data System (ADS)

    Friedrich, Jana; Gomoiu, Marian-Trajan; Naeher, Sebastian; Secrieru, Dan; Teaca, Adrian

    2013-04-01

    The Black Sea, containing the world's largest natural anoxic basin since ca 7500 years (Jones & Gagnon 1994), suffers from combined effects of anthropogenic eutrophication, overfishing and climate variability (Oguz & Gilbert 2007). We discuss causes for hypoxia in western shelf waters. Freshwater runoff by the large rivers Danube, Dniester and Dnieper results in strong thermohaline stratification that limits bottom water ventilation on the north-western shelf during warm seasons. This makes the western shelf generally prone to oxygen deficiency. During autumn and winter, the thermohaline stratification is eroded by frequent storms and the water column is re-oxygenated. The causal chain of anthropogenic eutrophication since the 1970s led to seasonal hypoxia on the western shelf for more than 20 years causing the catastrophic decline of key shelf habitats (Mee et al. 2005). More frequent and intense algal blooms, red tides (i.e. Noctiluca, Prorocentrum cordatum) and changes in species composition in phytoplankton resulted in deposition of surplus organic matter on the seafloor increasing the oxygen demand, with serious consequences for pelagic and benthic ecosystem structure and functioning. During hypoxia, release of reduced substances like ammonia and phosphate from the sediment to the water fuelled eutrophication internally (Friedrich et al. 2002). The combination of existing data with those gained during EU FP7 HYPOX on the Romanian shelf enables to assess the development of bottom water hypoxia and changes in benthic community and hence, the current state and trends in recovery of the Romanian Black Sea shelf ecosystem. Mud worms are the winners of eutrophication and hypoxia, whereas filter feeders like Mytilus galloprovincialis and Acanthocardia paucicostata are the losers. The western shelf benthic ecosystem showed a significant reduction in species diversity, a reduction of biofilter strength due to the loss of filter-feeder populations and flourishing of

  1. Recent seasonal hypoxia on the Western Black Sea shelf recorded in adjacent slope sediments

    NASA Astrophysics Data System (ADS)

    Roepert, Anne; Jilbert, Tom S.; Slomp, Caroline P.

    2015-04-01

    Bottom water hypoxia is a major environmental problem afflicting estuarine and marine environments across the globe (Diaz and Rosenberg, 2008). Hypoxia is often attributed to human-induced increased nutrient discharge from rivers and related eutrophication. The Western Black Sea shelf is a typical example of a system where such anthropogenic impacts are thought to have contributed to the development of seasonal hypoxia in the late 20th century. However, due to the lack of spatially and temporally consistent monitoring in the region, questions remain about the evolution, causes and consequences of the seasonal hypoxia on the Western Black Sea shelf and whether or not the ecological state has recently improved (Capet et al., 2013). In this study a resin-embedded sediment core from a location below the chemocline on the Western Black Sea slope (water depth 377 m) was analyzed for its elemental composition by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), recovering a continuous geochemical record at a sub-annual resolution for the last 100 years. Relative enrichments in organic carbon, Pb, Fe, S, and Mo were observed in the depth interval corresponding to the 1970s until the 1990s, suggesting an increased carbon flux to the sediments as well as an anthropogenic pollution signal. We propose that the expansion of eutrophication on the Western Black Sea shelf was responsible for the enhanced carbon flux to our study site, while the associated hypoxia enhanced the shuttling of redox-sensitive elements to locations below the chemocline. The subsequent decrease in organic carbon and metal enrichments at the core top suggests a recent rise in oxygen concentrations and improvement of the ecological state of the Western Black Sea shelf. References: Capet, A., Beckers, J.-M., Grégoire, M. (2013). "Drivers, mechanisms and long-term variability of seasonal hypoxia on the Black Sea northwestern shelf-is there any recovery after eutrophication

  2. Relative Sea Level Change in Western Alaska As Constructed from Satellite Altimetry and Repeat GPS Measurements.

    NASA Astrophysics Data System (ADS)

    DeGrandpre, K. G.; Freymueller, J. T.; Kinsman, N.

    2014-12-01

    Western Alaska is a remote region populated by small communities situated in low-lying coastal environments that are sensitive to variations in local relative sea level (RSL). RSL is the measurement of sea level relative to the local ground surface. Quantification of RSL variation requires measuring vertical velocities for both tectonic motion (onshore component) and the ocean surface (offshore component). Tide gauges in conjunction with tidal benchmarks record RSL, but in Western Alaska these datums are of short duration and too sparsely distributed both temporally and spatially to be able to accurately project RSL trends. Satellite altimetry is not suited for near shore estimates, but is used in this study because of the limited tide gauge coverage both spatially and temporally. During the summers of 2013 and 2014, campaign GPS surveys of geodetic benchmarks were undertaken to produce statistically significant velocity measurements of the tectonic component of sea level change for the Seward Peninsula, Yukon-Kuskokwim Delta, and Alaska Peninsula. Occupations of tidal benchmarks were also collected to compare historic tidal records from the mid-1900s to more recent data. Preliminary results from the GPS survey suggest regional subsidence of approximately 1-2 mm/yr of the Seward Peninsula, which supports one of the current glacial isostatic adjustment (GIA) models available for Western Alaska. The vertical velocity of the tectonic component and the satellite derived mean sea level trend will be coupled to produce a model of RSL change in Western Alaska that will be used to aid local communities in the development of adaptation strategies for changing coastal environments.

  3. Paleoceanographic conditions in the western Bering Sea as a response to global sea level changes and remote climatic signals during the last 180 kyr

    NASA Astrophysics Data System (ADS)

    Ovsepyan, E. A.; Ivanova, E. V.; Gulev, S. K.

    2016-06-01

    We present results from the sediment core SO201-2-85KL retrieved from the western Bering Sea that recovered the past 180 000 years. For the first time, the intense dissolution of calcareous microfossils has been established when the Bering Strait was open during the glacioeustatic sea level rise. Possible mechanisms of climatic teleconnections between remote regions are considered.

  4. Paleoceanographic reconstruction in the western and northern Barents Sea during and after the last deglaciation

    NASA Astrophysics Data System (ADS)

    Aagaard-Sørensen, Steffen; Groot, Diane E.; Husum, Katrine; Hald, Morten

    2013-04-01

    During the last glacial maximum the Barents Sea shelf area was covered by the Svalbard-Barents Sea Ice Sheet (SBIS). After the retreat of the SBIS the Barents Sea gradually became one of the main gate ways for Atlantic Water transport towards the Arctic Ocean. At present, the south-western Barents Sea is influenced by warm and saline Atlantic Water, while the northern part is dominated by cold and less saline Arctic water masses. The sharp temperature and salinity gradients between the two water masses form an oceanic front. The front area is associated with high benthic biological production and approximately defines the winter sea ice extend. Two gravity cores from the western (JM09-KA11, Kveithola Trough, ~74°N, 16°E) and northern (NP05-11-70, Olga Basin, ~78°N, 32°E) Barents Sea were investigated in regards to benthic foraminiferal fauna, stable isotopes and sedimentology. Moreover transfer function reconstructions of bottom water temperature and salinity were performed. The age models set minimum ages of deglaciation at 15.500 and 11.000 cal yr B.P. in the Kveithola Trough and the Olga Basin, respectively. Following the deglaciation of the Kveithola Trough bottom water temperature and salinity fluctuated in response to inputs of melt water and changing influx of Atlantic Water. Sea ice cover and presence of icebergs varied during this period. The area experienced near perennial sea ice cover conditions during the Younger Dryas. Conditions stabilized after ca. 10.000 cal yr B.P. with Atlantic Water dominating the bottom waters until present while sea ice/iceberg presence was reduced to a minimum. In the Olga Basin cold conditions, probably with abundant sea ice, characterized the early Holocene. This period was followed by warmer and more saline bottom water conditions due to an increased input of water of Atlantic origin after ca. 6.000 cal yr B.P. The last 2000 years conditions became colder and more unstable.

  5. Penultimate and last glacial cycles in the western Bering Sea: evidence from micropaleontological and sedimentary records

    NASA Astrophysics Data System (ADS)

    Ovsepyan, Ekaterina; Ivanova, Elena; Murdmaa, Ivar

    2014-05-01

    The short- and long-term variability of sea-surface bioproductivity, intermediate-water oxygenation, sea ice conditions and bottom current velocities are inferred from the high-resolution multi-proxy study based on benthic (BF) and planktonic (PF) foraminiferal assemblages and sedimentary record of the 18m-long Core SO201-2-85KL (western Bering Sea). Early MIS 6 is characterized by a very low seasonal bioproductivity, moderate bottom-water oxygenation, and expanded seasonal sea ice conditions, as documented by the abundant phytodetritus species Alabaminella weddelensis, Islandiella norcrossi and Epistominella arctica, suboxic group of BF, and high accumulation rates of gravel grains, respectively. Middle MIS 6 is represented by intercalation of green diatomaceous ooze and grey clayey silt layers with sharp peaks of BF abundance in green interbeds. These spikes might result either from short-term events of enhanced sea surface bioproductivity or from lateral BF transport by intensified bottom currents, as it is demonstrated by high-amplitude variations of the clay/silt ratio. Rather high seasonal productivity and northward migration of the sea ice margin are reconstructed for the late MIS 6 that is also characterized by a slight increase in the Northern Hemisphere summer insolation. Strong dissolution of calcareous microfossils is revealed for MIS 5.5-5.1 when the Bering Strait was open. Dissolution might be caused by an excess of carbon dioxide in the bottom-water due to an abundant organic matter decay and/or to an influence of the old CO2-rich deep water. MIS 4 - early Termination I is characterized by a dominance of glacial benthic foraminiferal assemblages that implies low bioproductivity conditions. A prevalence of suboxic BF group suggests moderate bottom-water oxygenation. Sea ice rafting occurred in the western Bering Sea during MIS 4 - early Termination I but the drifted ice was not so dense as during MIS 6. The well-known productivity spikes at B

  6. Low sea-level stand emplacement of megaturbidites in the western and eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Rothwell, R. G.; Reeder, M. S.; Anastasakis, G.; Stow, D. A. V.; Thomson, J.; Kähler, G.

    2000-09-01

    Piston cores from the Balearic and Herodotus Abyssal Plains in the Mediterranean Sea show that the Late Pleistocene to Holocene sedimentary sequence is dominated by turbidite muds. On each plain, one turbidite bed is conspicuous by its thickness, and this bed can be correlated basinwide on the basis of geochemical compositional analysis and its apparent correspondence with a distinct acoustically transparent layer on high-resolution seismic records. These megabeds on the two plains represent megaturbidites of very large volume (300-600 km 3 each) and are shown by AMS radiocarbon dating to have been emplaced during the last low stand of sea-level at the height of the last glacial maximum. The megabed on the Balearic Abyssal Plain is derived from the southern European margin and is the main sedimentation event over the last 120 ka. It emplaced as much material as was deposited by smaller flows during the previous 25 ka. Sedimentation rate curves for the Balearic Abyssal Plain show that falling sea-level correlates with increased terrigenous deposition, and that gross sedimentation rates in the basin increased as sea level fell from 120-18 ka due to more frequent emplacement of distal turbidites. The Herodotus Abyssal Plain megabed is derived from the Libyan-Egyptian continental shelf west of the Nile Delta and was the dominant sedimentation event in this basin during the past 60 kyr. High-resolution seismic profiles from the Ionian and Sirte Abyssal Plains in the central Mediterranean also suggest possible low sea-level emplacement of megabeds in these regions. Available evidence suggests widespread emplacement of megaturbidites throughout the Mediterranean at the last glacial maximum. Although the triggering mechanisms for these events remain speculative, catastrophic destabilisation of the margin after a long period of accumulation with an increased rate of sediment supply is suggested.

  7. Dimethylsulfide emissions over the multi-year ice of the western Weddell Sea

    NASA Astrophysics Data System (ADS)

    Zemmelink, H. J.; Dacey, J. W. H.; Houghton, L.; Hintsa, E. J.; Liss, P. S.

    2008-03-01

    This study, conducted in December 2004, is the first to present observations of DMS in a snow pack covering the multi-year sea ice of the western Weddell Sea. The snow layer is important because it is the interface through which DMS needs to be transported in order to be emitted directly from the ice to the overlying atmosphere. High concentrations of DMS, up to 6000 nmol m-3, were found during the first weeks of December but concentrations sharply decline as late spring-early summer progresses. This implies that DMS contained in sea ice is efficiently vented through the snow into the atmosphere. Indeed, field measurements by relaxed eddy accumulation indicate an average release of 11 μmol DMS m-2 d-1 from the ice and snow throughout December.

  8. Origin and abundance of marine litter along sandy beaches of the Turkish Western Black Sea Coast.

    PubMed

    Topçu, Eda N; Tonay, Arda M; Dede, Ayhan; Öztürk, Ayaka A; Öztürk, Bayram

    2013-04-01

    Beach debris abundance was estimated from surveys on 10 beaches of the Turkish Western Black Sea Coast. Debris was collected from 20 m long transects during four different seasons; sorted and categorized by type, usage and origin. Litter density varied from 0.085 to 5.058 items m(-2). Debris was mainly composed of unidentifiable small size (2-7 cm) plastic pieces and beverage-related litter such as bottles and bottle caps. About half of the labeled litter was of foreign origin, including 25 different countries, 23% of which are in the Black Sea region. The south-western Black Sea Coast seems to receive foreign litter from two main sources: land-based debris from the neighboring countries and seaborne debris due to international shipping. Standardized methodology and indicators need to be designated all over the Black Sea basin in order to quantify and qualify coastal litter pollution, monitor compliance with MARPOL and develop regionally effective mitigation measures. PMID:23290790

  9. Offshore seismicity in the western Marmara Sea, Turkey, revealed by ocean bottom observation

    NASA Astrophysics Data System (ADS)

    Yamamoto, Yojiro; Takahashi, Narumi; Citak, Seckin; Kalafat, Doğan; Pinar, Ali; Gurbuz, Cemil; Kaneda, Yoshiyuki

    2015-09-01

    The faults' geometry and their seismic activity beneath the Marmara Sea have been under debate for a couple of decades. We used data recorded by three ocean bottom seismographs (OBSs) over a period of 3 months in 2014 to investigate the relationship of fault geometry to microseismicity under the western Marmara Sea in Turkey. We detected a seismic swarm at 13 to 20 km depth beneath the main Marmara fault (MMF), and the maximum depth of seismogenic zone was 25 km within the OBS observation area. These results provided evidence that the dip of the MMF is almost vertical and that the seismogenic zone in this region extends into the lower crust. Our analysis of past seismicity indicated that the seismic swarm we recorded is the most recent of an episodic series of seismic activity with an average recurrence interval of 2-3 years. The repetitive seismicity indicates that the MMF beneath the western Marmara Sea is coupled and that some of the accumulated strain is released every 2 to 3 years. Our study shows that OBS data can provide useful information about seismicity along the MMF, but more extensive studies using more OBSs deployed over a wider area are needed to fully understand the fault geometry and stick-slip behavior of faults under the Marmara Sea.

  10. Model simulations of dense bottom currents in the Western Baltic Sea

    NASA Astrophysics Data System (ADS)

    Burchard, Hans; Janssen, Frank; Bolding, Karsten; Umlauf, Lars; Rennau, Hannes

    2009-01-01

    Only recently, medium intensity inflow events into the Baltic Sea have gained more awareness because of their potential to ventilate intermediate layers in the Southern Baltic Sea basins. With the present high-resolution model study of the Western Baltic Sea a first attempt is made to obtain model based realistic estimates of turbulent mixing in this area where dense bottom currents resulting from medium intensity inflow events are weakened by turbulent entrainment. The numerical model simulation which is carried out using the General Estuarine Transport Model (GETM) during nine months in 2003 and 2004 is first validated by means of three automatic stations at the Drogden and Darss Sills and in the Arkona Sea. In order to obtain good agreement between observations and model results, the 0.5×0.5 nautical mile bathymetry had to be adjusted in order to account for the fact that even at that scale many relevant topographic features are not resolved. Current velocity, salinity and turbulence observations during a medium intensity inflow event through the Øresund are then compared to the model results. Given the general problems of point to point comparisons between observations and model simulations, the agreement is fairly good with the characteristic features of the inflow event well represented by the model simulations. Two different bulk measures for mixing activity are then introduced, the vertically integrated decay of salinity variance, which is equal to the production of micro-scale salinity variance, and the vertically integrated turbulent salt flux, which is related to an increase of potential energy due to vertical mixing of stably stratified flow. Both measures give qualitatively similar results and identify the Drogden and Darss Sills as well as the Bornholm Channel as mixing hot spots. Further regions of strong mixing are the dense bottom current pathways from these sills into the Arkona Sea, areas around Kriegers Flak (a shoal in the western Arkona Sea

  11. Mercury Dynamics across the Ocean- Young Sea Ice- Atmosphere Interface in the Western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Chaulk, A. H.; Armstrong, D.; Wang, F.; Stern, G.

    2009-12-01

    Mercury is a global contaminant and has become an increasing concern in the Arctic marine ecosystems. Methyl mercury is highly toxic, biomagnifies in food webs, and is found in elevated levels in marine mammals in some locations. Major research initiatives have been undertaken in recent years to understand the sources and pathways for mercury bioaccumulation in the Arctic marine ecosystems. One major scientific dispute is on the net contribution of the atmospherically transported mercury. Atmospheric mercury depletion events (AMDEs) provide a possible pathway of increased atmospheric mercury deposition from the atmosphere to the surface. Although direct deposition can occur in open leads, much of the ocean surface is ice-covered at the time when AMDEs occur. The current understanding of mercury dynamics lacks data on mercury concentrations and distribution in sea ice and brine. As part of the International Polar Year Circumpolar Flaw Lead System Study (IPY-CFL), sea ice (new, first year, and multi-year) and brine drainage were sampled at various drifting and landfast ice stations in the western Arctic Ocean and Beaufort Sea throughout the 2008 Arctic AMDE season. Total mercury concentration in brine ranged from 71.2 ng/L to 2.7 ng/L, decreasing from shallow sack holes near the surface to deeper holes near the bottom, and was always much higher than that in the underlying seawater (typically around 0.2 ng/L). Bulk ice cores showed similar profiles with higher mercury concentrations in the surface layer, particularly in the surface frazil layer. Sea ice texture, salinity, and brine volume fraction have all been shown to impact the distribution of mercury within sea ice. Evidence also suggests that atmospheric deposition, although possible, seems relatively unimportant in mercury enrichment in the surface of first year sea ice. In the era of global climate change Arctic sea ice is undergoing rapid change; this changing ice regime will have an effect on the mercury

  12. Observation of an abrupt disruption of the long-term warming trend at the Balearic Sea, western Mediterranean Sea, in summer 2005

    NASA Astrophysics Data System (ADS)

    López-Jurado, J.-L.; González-Pola, C.; Vélez-Belchí, P.

    2005-12-01

    The properties of the Western Mediterranean Deep Water in a wide area located at the western boundary of the Mediterranean Sea, including the Balearic Sea, have revealed intense changes when observed in summer 2005. Between February and June 2005, a temperature drop of 0.14°C reverted dramatically the progressive warming trend of 0.011°C yr-1 that had been observed since 1996, in the waters below 600 dbar north of the Balearic channels. A similar temperature drop has been observed east of the Minorca Island, below the Levantine Intermediate Water and down to 1500 dbar. In the deepest levels, a complex thermohaline structure, which implies different waters masses as sources, was tracked more than 400 km along the western boundary of the Mediterranean Sea, from Barcelona to the Algerian Basin. It is suggested that the changes may be linked to the severe 2004/2005 winter occurred at the northwestern Mediterranean Sea.

  13. Ecology of the Atlantic black skipjack Euthynnus alletteratus (Osteichthyes: Scombridae) in the western Mediterranean Sea inferred by parasitological analysis.

    PubMed

    Mele, Salvatore; Pennino, M Grazia; Piras, M Cristina; Macías, David; Gómez-Vives, M José; Alemany, Francisco; Montero, Francisco E; Garippa, Giovanni; Merella, Paolo

    2016-09-01

    Between 2008 and 2011, the head of 150 Euthynnus alletteratus (Osteichthyes: Scombridae) caught inshore off the southeastern Iberian coast (western Mediterranean Sea) were examined for parasites. Two monogeneans, four didymozoid trematodes and four copepods were found. Parasite abundance showed a positive relationship with the annual sea surface temperature, except for Pseudocycnus appendiculatus, but negative with the sea depth (Capsala manteri, Neonematobothrium cf. kawakawa and Caligus bonito). Prevalences and mean abundances differed significantly among sampling areas, except for C. manteri, Oesophagocystis sp. 2 and Ceratocolax euthynni, and sampling years (Melanocystis cf. kawakawa, N.cf. kawakawa, P. appendiculatus and Unicolax collateralis). Results indicate that the parasite abundances of E. alletteratus in the western Mediterranean Sea depend mainly on regional environmental variables, which can show interannual variations. The presence of pelagic parasites, i.e. didymozoids and P. appendiculatus, could indicate that E. alletteratus migrates between inshore and offshore pelagic domains. The different parasite faunas reported in E. alletteratus populations from the western Atlantic Ocean and the Mediterranean Sea appear to point out the geographical host isolation. These results suggest that E. alletteratus inhabiting the western Mediterranean Sea performs inshore-offshore small-scale migrations, and not transoceanic migrations between the western Atlantic Ocean and Mediterranean Sea. PMID:27173779

  14. The main characteristics, problems, and prospects for Western European coastal seas.

    PubMed

    Dauvin, Jean-Claude

    2008-01-01

    Located to the far West of Western Europe, France has a western maritime coastal zone of more than 3800 km, which is widely influenced by the North-eastern Atlantic. The English Channel, an epi-continental shallow sea with very strong tides, runs along 650 km of the French coast and 1100 km of the English coast. It is also a bio-geographical crossroad encompassing a much wider range of ecological conditions than other European seas. France's Atlantic coast north of the Gironde estuary is a succession of rocky and sandy shorelines, including a sizeable intertidal zone, a wide continental shelf, and two major estuaries (Loire and Gironde). South of the Gironde, the 260 km of coastline is low, sandy and straight, with a narrowing continental shelf further on South due to the presence of the Cape Breton canyon in the bathyal and abyssal zones. Interface between the continental and oceanic systems, these bordering seas--North Sea, English Channel and Atlantic Ocean--have been the subject of many recent research programmes (the European Mast-FLUXMANCHE and INTERREG programmes; the national coastal environment programme and the LITEAU programme in France), designed to improve comprehension of the functions, production, and dynamics of these seas as well as their future evolution. Given the many conflicting practices in these littoral zones, integrated coastal zone management appears to be essential in order to cope with both natural phenomena, such as the infilling of estuarine zones, cliff erosion, and rising sea levels, and chronic anthropogenic pressures, such as new harbour installations (container dikes, marinas), sea aggregate extraction for human constructions, and offshore wind mill farms. This article provides as complete an overview as possible of the research projects on these bordering seas, both those that have recently been accomplished and those that are currently in progress, in order to highlight the main characteristics of these ecosystems and to

  15. Species diversity variations in Neogene deep-sea benthic foraminifera at ODP Hole 730A, western Arabian Sea

    NASA Astrophysics Data System (ADS)

    Arumugm, Yuvaraja; Gupta, Anil K.; Panigrahi, Mruganka K.

    2014-10-01

    Deep-sea benthic foraminifera are an important and widely used marine proxy to understand paleoceanographic and paleoclimatic changes on regional and global scales, owing to their sensitivity to oceanic and climatic turnovers. Some species of benthic foraminifera are sensitive to changes in water mass properties whereas others are sensitive to organic fluxes and deep-sea oxygenation. Benthic faunal diversity has been found closely linked to food web, bottom water oxygen levels, and substrate and water mass stability. The present study is aimed at analyzing species diversity trends in benthic foraminifera and their linkages with Indian monsoon variability during the Neogene. Species diversity of benthic foraminifera is examined in terms of number of species (S), information function (H), equitability (E) and Sanders' rarefied values, which were combined with relative abundances of high and low productivity benthic foraminifera at Ocean Drilling Program Hole 730A, Oman margin, western Arabian Sea. The Oman margin offers the best opportunity to understand monsoon-driven changes in benthic diversity since summer monsoon winds have greater impact on the study area. The species diversity was higher during the early Miocene Climatic Optimum (˜17.2-16.4 Ma) followed by a decrease during 16.4-13 Ma coinciding with a major increase in Antarctic ice volume and increased formation of Antarctic Bottom Water. All the diversity parameters show an increase during 13-11.6 Ma, a gradual decrease during 11.6-9 Ma and then an increase with a maximum at 7 Ma. Thereafter the values show little change until 1.2 Ma when all the parameters abruptly decrease. The benthic foraminiferal populations and diversity at Hole 730A were mainly driven by the Indian monsoon, and polar waters might have played a minor or no role since early Neogene period as the Arabian Sea is an enclosed basin.

  16. Clay mineralogy of Lower Cretaceous deep-sea fan sediments, western North Atlantic basin

    SciTech Connect

    Holmes, M.A.

    1986-05-01

    The Lower Cretaceous of the eastern North American continent was a time of extensive deltaic progradation. The effects of deltaic deposition on sedimentation in the western North Atlantic were unknown until May 1982, when, at Deep Sea Drilling Project Site 603 off Cape Hatteras, over 260 m of micaceous, muddy turbidites were recovered that correlate with deltaic progradation on eastern North America. The results of clay mineral studies from onshore and offshore equivalents indicate that during the Cretaceous, some sorting of clay minerals by transport processes occurred. Kaolinite tends to accumulate in continental environments, illite in transitional to marine environments, and smectite in deep sea sediments as pelagic clay. In the sediments from the western North Atlantic, illite tended to be more abundant in thick bedded sandy muds, whereas kaolinite tended to be more abundant in thin bedded muddy sands. Although the occurrence of illite and kaolinite in pelagic sediments indicates a general increased terrigenous influence, the results of this study indicate that these two clays behave independently in these sediments. The presence of large amounts of kaolinite at certain levels in these sediments corresponds to phases of maximum deep-sea fan development, and so indicates a more direct input of continental material, with less sorting of sediments by continental and shelf processes (pericontinental fractionation) prior to redeposition.

  17. Accumulation and marine forcing of ice dynamics in the western Ross Sea during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Hall, Brenda L.; Denton, George H.; Heath, Stephanie L.; Jackson, Margaret S.; Koffman, Tobias N. B.

    2015-08-01

    The grounding line of the ice sheet in the Ross Sea, Antarctica, retreated between the Last Glacial Maximum and the present. However, the timing of the retreat and the interplay of factors controlling ice stability in this region remain uncertain. Here we use 180 radiocarbon dates to reconstruct the chronology of moraine construction on the headlands adjacent to western McMurdo Sound. On the basis of these dates we then assess the timing of ice expansion and retreat in the Ross drainage system that is fed from both the East and West Antarctic ice sheets. We find that grounded ice in the western Ross Sea achieved its greatest thickness and extent during the last termination, between 12,800 and 18,700 years ago. Maximum ice thickness at our site coincides with a period of high accumulation as recorded by the West Antarctic Ice Sheet Divide ice core. Recession of the ice sheet from the headland moraines began about 12,800 years ago, despite continued high accumulation and the expansion of land-based glaciers at this time. We therefore suggest that the grounding-line retreat reflects an increased marine influence as sea levels rose and the ocean warmed. We suggest that future instability in the ice sheet grounding line may occur whenever the ocean forcing is stronger than forcing from accumulation.

  18. Polychlorinated biphenyls (PCBs) in sediments from the western Adriatic Sea: Sources, historical trends and inventories.

    PubMed

    Combi, Tatiane; Miserocchi, Stefano; Langone, Leonardo; Guerra, Roberta

    2016-08-15

    Sources, historical trends and inventories of polychlorinated biphenyls (PCBs) were investigated in sediments collected in five transects along the north-south axis of the western Adriatic Sea. The concentration of total PCBs (∑28 PCBs) ranged from western Adriatic Sea. This is further corroborated by the estimated inventories of PCBs, which were ~4-7 times higher in the Po River prodelta (256ngcm(-2)) in comparison to the middle and southern Adriatic, respectively, and about 100 times higher than the in the deep Adriatic Sea. PMID:27110972

  19. Faunistic Composition, Ecological Properties, and Zoogeographical Composition of the Elateridae (Coleoptera) Family in the Western Black Sea Region of Turkey

    PubMed Central

    Kabalak, Mahmut; Sert, Osman

    2013-01-01

    The main aim of this study was to understand the faunistic composition, ecological properties, and zoogeographical composition of the family Elateridae (Coleoptera) of the Western Black Sea region of Turkey. As a result, 44 species belonging to 5 subfamilies and 19 genera were identified. After adding species reported in the literature to the analysis, the fauna in the research area consists of 6 subfamilies, 23 genera and 72 species. Most of the Elateridae fauna of the Western Black Sea region were classified in the subfamilies Elaterinae and Dendrometrinae. The genus Athous was the most species-rich genus. The species composition of the Elateridae fauna of the Western Black Sea region partially overlaps with the known Elateridae fauna of Turkey. The Western Black Sea region shares the most species with the European part of the Western Palaearctic region, including many of those in the Elateridae family, compared to other regions. Comparisons of the three geographical regions of Turkey show that fauna composition, ecological properties, and zoogeographical compositions of the Middle and Western Black Sea regions are more similar to each other than to those of the Central Anatolian region. PMID:24787627

  20. Sedimentological imprint on subseafloor microbial communities in Western Mediterranean Sea Quaternary sediments

    NASA Astrophysics Data System (ADS)

    Ciobanu, M.-C.; Rabineau, M.; Droz, L.; Révillon, S.; Ghiglione, J.-F.; Dennielou, B.; Jorry, S.-J.; Kallmeyer, J.; Etoubleau, J.; Pignet, P.; Crassous, P.; Vandenabeele-Trambouze, O.; Laugier, J.; Guégan, M.; Godfroy, A.; Alain, K.

    2012-09-01

    An interdisciplinary study was conducted to evaluate the relationship between geological and paleoenvironmental parameters and the bacterial and archaeal community structure of two contrasting subseafloor sites in the Western Mediterranean Sea (Ligurian Sea and Gulf of Lion). Both depositional environments in this area are well-documented from paleoclimatic and paleooceanographic point of views. Available data sets allowed us to calibrate the investigated cores with reference and dated cores previously collected in the same area, and notably correlated to Quaternary climate variations. DNA-based fingerprints showed that the archaeal diversity was composed by one group, Miscellaneous Crenarchaeotic Group (MCG), within the Gulf of Lion sediments and of nine different lineages (dominated by MCG, South African Gold Mine Euryarchaeotal Group (SAGMEG) and Halobacteria) within the Ligurian Sea sediments. Bacterial molecular diversity at both sites revealed mostly the presence of the classes Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria within Proteobacteria phylum, and also members of Bacteroidetes phylum. The second most abundant lineages were Actinobacteria and Firmicutes at the Gulf of Lion site and Chloroflexi at the Ligurian Sea site. Various substrates and cultivation conditions allowed us to isolate 75 strains belonging to four lineages: Alpha-, Gammaproteobacteria, Firmicutes and Actinobacteria. In molecular surveys, the Betaproteobacteria group was consistently detected in the Ligurian Sea sediments, characterized by a heterolithic facies with numerous turbidites from a deep-sea levee. Analysis of relative betaproteobacterial abundances and turbidite frequency suggested that the microbial diversity was a result of main climatic changes occurring during the last 20 ka. Statistical direct multivariate canonical correspondence analyses (CCA) showed that the availability of electron acceptors and the quality of electron donors (indicated by age

  1. Cetacean response to summer maritime traffic in the Western Mediterranean Sea.

    PubMed

    Campana, I; Crosti, R; Angeletti, D; Carosso, L; David, L; Di-Méglio, N; Moulins, A; Rosso, M; Tepsich, P; Arcangeli, A

    2015-08-01

    Maritime traffic is one of many anthropogenic pressures threatening the marine environment. This study was specifically designed to investigate the relationship between vessels presence and cetacean sightings in the high sea areas of the Western Mediterranean Sea region. We recorded and compared the total number of vessels in the presence and absence of cetacean sightings using data gathered during the summer season (2009-2013) along six fixed transects repeatedly surveyed. In locations with cetacean sightings (N = 2667), nautical traffic was significantly lower, by 20%, compared to random locations where no sightings occurred (N = 1226): all cetacean species, except bottlenose dolphin, were generally observed in locations with lower vessel abundance. In different areas the species showed variable results likely influenced by a combination of biological and local environmental factors. The approach of this research helped create, for the first time, a wide vision of the different responses of animals towards a common pressure. PMID:26009840

  2. The macrozoobenthos of the subtidal western dutch wadden sea. I. Biomass and species richness

    NASA Astrophysics Data System (ADS)

    Dekker, R.

    During a one-year period in 1981-1982, a survey was conducted on the macrozoobenthos of the subtidal areas of the western half of the Dutch Wadden Sea. In total 80 species were found, half of them polychaetes. In terms of biomass, Mytilus edulis dominated the macrozoobenthos, with Hydrobia ulvae, Heteromastus filiformis, Carcinus maenas and Macoma balthica as other important species. Numerically important were also the polychaetes Pygospio elegans and Scoloplos armiger. Average macrozoobenthic biomass amounted to 43.7 g·m -2 ash-free dryweight. This value is in the same range as values from intertidal areas in the Wadden Sea. The relatively high value in comparison with data from similar subtidal areas is attributed to the important mussel culture in the area.

  3. Photographs of the Sea Floor of Western Massachusetts Bay, Offshore of Boston, Massachusett, July 1999

    USGS Publications Warehouse

    Gutierrez, Benjamin T.; Butman, Bradford; Blackwood, Dann S.

    2001-01-01

    This CD-ROM contains photographs and sediment sample analyses of the sea floor obtained at 142 sites in western Massachusetts Bay (Figure 1) during a research cruise (USGS cruise ISBL99024) aboard the Fishing Vessel (FV) Isabel S. (Figure 2) conducted July 18-21, 1999. These photographs and samples provide critical ground truth information for the interpretation of shaded relief and backscatter intensity maps created using data collected with a multibeam echo sounder system (Butman and others, in press, a, b, c; Valentine and others, in press, a, b, c). Collection of these photographs and samples was undertaken in support of a large project whose overall objective is to map and describe the sea floor of Massachusetts Bay.

  4. Ageostrophic Frontal Processes Controlling Phytoplankton Production in the Catalano-Balearic Sea (Western Mediterranean).

    PubMed

    Oguz, Temel; Macias, Diego; Tintore, Joaquin

    2015-01-01

    Buoyancy-induced unstable boundary currents and the accompanying retrograde density fronts are often the sites of pronounced mesoscale activity, ageostrophic frontal processes, and associated high biological production in marginal seas. Biophysical model simulations of the Catalano-Balearic Sea (Western Mediterranean) illustrated that the unstable and nonlinear southward frontal boundary current along the Spanish coast resulted in a strain-driven frontogenesis mechanism. High upwelling velocities of up to 80 m d(-1) injected nutrients into the photic layer and promoted enhanced production on the less dense, onshore side of the front characterized by negative relative vorticity. Additional down-front wind stress and heat flux (cooling) intensified boundary current instabilities and thus ageostrophic cross-frontal circulation and augmented production. Specifically, entrainment of nutrients by relatively strong buoyancy-induced vertical mixing gave rise to a more widespread phytoplankton biomass distribution within the onshore side of the front. Mesoscale cyclonic eddies contributed to production through an eddy pumping mechanism, but it was less effective and more limited regionally than the frontal processes. The model was configured for the Catalano-Balearic Sea, but the mechanisms and model findings apply to other marginal seas with similar unstable frontal boundary current systems. PMID:26065688

  5. Ageostrophic Frontal Processes Controlling Phytoplankton Production in the Catalano-Balearic Sea (Western Mediterranean)

    PubMed Central

    Oguz, Temel; Macias, Diego; Tintore, Joaquin

    2015-01-01

    Buoyancy-induced unstable boundary currents and the accompanying retrograde density fronts are often the sites of pronounced mesoscale activity, ageostrophic frontal processes, and associated high biological production in marginal seas. Biophysical model simulations of the Catalano-Balearic Sea (Western Mediterranean) illustrated that the unstable and nonlinear southward frontal boundary current along the Spanish coast resulted in a strain-driven frontogenesis mechanism. High upwelling velocities of up to 80 m d-1 injected nutrients into the photic layer and promoted enhanced production on the less dense, onshore side of the front characterized by negative relative vorticity. Additional down-front wind stress and heat flux (cooling) intensified boundary current instabilities and thus ageostrophic cross-frontal circulation and augmented production. Specifically, entrainment of nutrients by relatively strong buoyancy-induced vertical mixing gave rise to a more widespread phytoplankton biomass distribution within the onshore side of the front. Mesoscale cyclonic eddies contributed to production through an eddy pumping mechanism, but it was less effective and more limited regionally than the frontal processes. The model was configured for the Catalano-Balearic Sea, but the mechanisms and model findings apply to other marginal seas with similar unstable frontal boundary current systems. PMID:26065688

  6. Immigration of larval plaice ( Pleuronectes platessa L.) into the western wadden sea: A question of timing

    NASA Astrophysics Data System (ADS)

    Hovenkamp, Frans

    Migration of larval plaice into a nursery area in the western Wadden Sea was monitored during three immigration seasons. Daily otolith increments were used to estimate age and hatch dates of the larvae, and the hatch dates were compared to egg-production curves. Different cohorts of larvae invaded the area, originating from different spawning grounds. During a cold year, most larvae probably came from the Western Channel, but during the two warm years most larvae originated from more northern spawning grounds. Settlement on a tidal flat showed a delayed response to immigration in the first part of the season, but a direct response later in the season. Length-frequency distributions of settled juveniles were compared to expected frequencies based on a simple growth model. It is argued that early in the season growth-related mortality may have been too high to ensure successful settlement, and that timing could be of significant importance for larval immigration to be successful.

  7. Mid-Piacenzian sea surface temperature record from ODP Site 1115 in the western equatorial Pacific

    USGS Publications Warehouse

    Stoll, Danielle

    2010-01-01

    Planktic foraminifer assemblages and alkenone unsaturation ratios have been analyzed for the mid-Piacen-zian (3.3 to 2.9 Ma) section of Ocean Drilling Program (ODP) Site 1115B, located in the western equatorial Pacific off the coast of New Guinea. Cold and warm season sea surface temperature (SST) estimates were determined using a modern analog technique. ODP Site 1115 is located just south of the transition between the planktic foraminifer tropical and subtropical faunal provinces and approximates the southern boundary of the western equatorial Pacific (WEP) warm pool. Comparison of the faunal and alkenone SST estimates (presented here) with an existing nannofossil climate proxy shows similar trends. Results of this analysis show increased seasonal variability during the middle of the sampled section (3.22 to 3.10 Ma), suggesting a possible northward migration of both the subtropical faunal province and the southern boundary of the WEP warm pool.

  8. Anomalous hydrographic conditions in the western Barents Sea observed in March 2014

    NASA Astrophysics Data System (ADS)

    Dobrynin, Mikhail; Pohlmann, Thomas

    2015-12-01

    Observational data have been collected during a cruise to the western Barents Sea in March 2014 covering 33 stations along three west-east sections at 76.34°N, 77.26°N and 78.49°N and along one south-north section at 19.47°E. Our observations suggest a wedge-like water masses structure with colder and fresher Arctic Water moving southward, gliding over warmer and more saline Atlantic Water which below the surface moves to the north. Atlantic Water in the Storfjorden Trench reached farther north than 76.5°N and was present on the eastern and western slopes of the Spitsbergen Bank. Our measurements indicate limited dense water formation in the Storfjorden. A comparison with historical data over the years 1923-2011 reveal an anomalous northern location of the Polar Front for this time of the year in March 2014. A point by point comparison with ten historical stations in 1983 and 1986 shows significantly warmer (by up to 3.8 °C) and saltier (by up to 2.49 psu) conditions in 2014 for nine out of ten stations. Moreover, stations dominated by the Atlantic inflow experienced the largest changes, whereas in stations located in the area of the Arctic outflow the changes were smallest. Furthermore, we used satellite and decadal reanalysis data to estimate the climate variability defined by a range of two standard deviations. We found that in the Storfjorden Trench in March 2014 the water transport was within the range, while the water temperature exceeded the upper limit of climate variability. The sea ice extent in the western Barents Sea was below the lower limit of climate variability from mid-February to mid-March 2014. Combining in situ, satellite and model data, we were able to attribute the warm anomaly observed in March 2014 to two main reasons: (1) an increase of Atlantic water temperature which was evident already in the beginning of 2014 and (2) very little cooling in February and March 2014. From these results we conclude that the north-western Barents Sea

  9. Shallow geology, sea-floor texture, and physiographic zones of Vineyard and western Nantucket Sounds, Massachusetts

    USGS Publications Warehouse

    Baldwin, Wayne E.; Foster, David S.; Pendleton, Elizabeth A.; Barnhardt, Walter A.; Schwab, William C.; Andrews, Brian D.; Ackerman, Seth D.

    2016-01-01

    Geologic, sediment texture, and physiographic zone maps characterize the sea floor of Vineyard and western Nantucket Sounds, Massachusetts. These maps were derived from interpretations of seismic-reflection profiles, high-resolution bathymetry, acoustic-backscatter intensity, bottom photographs/video, and surficial sediment samples collected within the 494-square-kilometer study area. Interpretations of seismic stratigraphy and mapping of glacial and Holocene marine units provided a foundation on which the surficial maps were created. This mapping is a result of a collaborative effort between the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management to characterize the surface and subsurface geologic framework offshore of Massachusetts.

  10. Holocene palynomorph records since the last deglaciation from the Chukchi Sea shelf sediments, western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Kim, So-Young; Nam, Seung-Il; Polyak, Leonid; Delusina, Irina

    2015-04-01

    Organic-walled microscopic organisms in marine sediments such as dinoflagellate cysts, pollen, spores and freshwater algae from the Chukchi Sea shelf sediment document spatial and temporal variations in the paleoenvironmental history in relation to regional climatic changes during the Holocene. The records presented here are derived from a sediment core from the shallow shelf of the Chukchi Sea in the western Arctic (core ARA02B/01A-GC), a site which allows us to assess the timing of the Bering Strait opening and its influence over the regional environmental system during the last post glacial interval. The sediment core contains a rich concentration of terrestrially derived pollen and spores, indicating considerable changes in vegetation over the catchment area including the territories of both North America (Alaska and Northern Canadian Arctic) and Northern Siberia (Chukotka peninsula and Northern East-Siberian coast) during the last 10 kyr BP. We speculate that the palynomorphs were predominantly supplied from eroded shelf sediments during intervals of extensive sea-ice coverage, while they were carried to the shelves by large rivers (Yukon, Mackenzie and Siberian rivers) and then transferred by oceanic currents during low sea-ice coverage intervals. In particular, the percentage ratio between tree-herb pollen and spores, and the algae Pediastrum in the palynomorph assemblages represent significant changes in the western Arctic vegetation associated with freshwater inputs, including increased forest vegetation between ~8 and 4 kyr BP, a climatic optimum at ~5 kyr BP and a termination of the low sea-ice interval at ~3 kyr BP. In parallel, marine palynomorphs (dinoflagellate cysts) document significant changes in the marine environments, typically for a prominent increase in dinoflagellate cyst concentrations as well as total organic carbon and nitrogen contents since ca. 8 kyr BP suggesting increased nutrient inputs and marine productivity in the study area. Our

  11. Selected anthropogenic and natural radioisotopes in the Barents Sea and off the western coast of Svalbard.

    PubMed

    Leppänen, Ari-Pekka; Kasatkina, Nadezhda; Vaaramaa, Kaisa; Matishov, Gennady G; Solatie, Dina

    2013-12-01

    The Murmansk Marine Biological Institute (MMBI) performed high-latitude expeditions to the Barents Sea during 2007-2009 where a scientist from the Radiation and Nuclear Safety Authority (STUK) participated. The aim of the expeditions was to study and map the current radiological situation throughout the Barents Sea. In the expeditions, samples of seawater, sediment and biota were collected for radioactivity studies. The (90)Sr and (137)Cs isotopes were analysed from the seawater samples and no spatial distribution in the concentrations of (90)Sr and (137)Cs was found. The sediment samples were analysed for γ-emitting isotopes. In the statistical analysis performed only the (90)Sr was found to have no spatial distribution. In the (137)Cs concentrations two areas containing higher concentrations were observed: one in the western part of Svalbard and another in Franz Victoria Trough near the Franz Josef Land archipelago. The increase in the western coast of Svalbard suggests an Atlantic influence while in the Franz Victoria Trough source regions are possibly more complex. Since (137)Cs in marine sediments mainly originates from terrestrial sources, finding higher concentrations in the northern part of the Barents Sea may also suggest a contribution of (137)Cs carried by the ocean currents and by sea ice from the outside Barents Sea. In addition to γ spectrometric measurements, the sediment samples were radiochemically analysed for (210)Pb. It was found that the unsupported fraction of (210)Pb showed significant spatial variation. The fraction of unsupported (210)Pb was reduced to 40-70% near Bear Island, Edge Island and in the Franz Josef Land archipelago. In these regions the sea is typically covered with sea ice during winter. The relatively low fraction of unsupported (210)Pb is possibly caused by blocking of wet and dry deposition of (210)Pb onto the sea by winter sea ice. In biota samples, only small traces, at the level of 0.2 Bq/kg w.w. of (137)Cs, were found

  12. Distribution and sources of polycyclic aromatic hydrocarbons in surface sediments from the Bering Sea and western Arctic Ocean.

    PubMed

    Zhao, Mengwei; Wang, Weiguo; Liu, Yanguang; Dong, Linsen; Jiao, Liping; Hu, Limin; Fan, Dejiang

    2016-03-15

    To analyze the distribution and sources of polycyclic aromatic hydrocarbons (PAHs) and evaluate their potential ecological risks, the concentrations of 16 PAHs were measured in 43 surface sediment samples from the Bering Sea and western Arctic Ocean. Total PAH (tPAH) concentrations ranged from 36.95 to 150.21 ng/g (dry weight). In descending order, the surface sediment tPAH concentrations were as follows: Canada Basin>northern Chukchi Sea>Chukchi Basin>southern Chukchi Sea>Aleutian Basin>Makarov Basin>Bering Sea shelf. The Bering Sea and western Arctic Ocean mainly received PAHs of pyrogenic origin due to pollution caused by the incomplete combustion of fossil fuels. The concentrations of PAHs in the sediments of the study areas did not exceed effects range low (ERL) values. PMID:26806662

  13. Post-glacial variability of sea ice cover, river run-off and biological production in the western Laptev Sea (Arctic Ocean) - A high-resolution biomarker study

    NASA Astrophysics Data System (ADS)

    Hörner, T.; Stein, R.; Fahl, K.; Birgel, D.

    2016-07-01

    Multi-proxy biomarker measurements were applied on two sediment cores (PS51/154, PS51/159) to reconstruct sea ice cover (IP25), biological production (brassicasterol, dinosterol) and river run-off (campesterol, β-sitosterol) in the western Laptev Sea over the last ∼17 ka with unprecedented temporal resolution. The absence of IP25 from 17.2 to 15.5 ka, in combination with minimum concentration of phytoplankton biomarkers, suggests that the western Laptev Sea shelf was mostly covered with permanent sea ice. Very minor river run-off and restricted biological production occurred during this cold interval. From ∼16 ka until 7.5 ka, a long-term decrease of terrigenous (riverine) organic matter and a coeval increase of marine organic matter reflect the gradual establishment of fully marine conditions in the western Laptev Sea, caused by the onset of the post-glacial transgression. Intensified river run-off and reduced sea ice cover characterized the time interval between 15.2 and 12.9 ka, including the Bølling/Allerød warm period (14.7-12.9 ka). Prominent peaks of the DIP25 Index coinciding with maximum abundances of subpolar foraminifers, are interpreted as pulses of Atlantic water inflow on the western Laptev Sea shelf. After the warm period, a sudden return to severe sea ice conditions with strongest ice-coverage between 11.9 and 11 ka coincided with the Younger Dryas (12.9-11.6 ka). At the onset of the Younger Dryas, a distinct alteration of the ecosystem (reflected in a distinct drop in terrigenous and phytoplankton biomarkers) was detected. During the last 7 ka, the sea ice proxies reflect a cooling of the Laptev Sea spring/summer season. This cooling trend was superimposed by a short-term variability in sea ice coverage, probably representing Bond cycles (1500 ± 500 ka) that are related to solar activity changes. Hence, atmospheric circulation changes were apparently able to affect the sea ice conditions on the Laptev Sea shelf under modern sea level

  14. Sea ice cover variability and river run-off in the western Laptev Sea (Arctic Ocean) since the last 18 ka

    NASA Astrophysics Data System (ADS)

    Hörner, T.; Stein, R.; Fahl, K.; Birgel, D.

    2015-12-01

    Multi-proxy biomarker measurements were performed on two sediment cores (PS51/154, PS51/159) with the objective reconstructing sea ice cover (IP25, brassicasterol, dinosterol) and river-runoff (campesterol, β-sitosterol) in the western Laptev Sea over the last 18 ka with unprecedented temporal resolution. The sea ice cover varies distinctly during the whole time period. The absence of IP25 during 18 and 16 ka indicate that the western Laptev Sea was mostly covered with permanent sea ice (pack ice). However, a period of temporary break-up of the permanent ice coverage occurred at c. 17.2 ka (presence of IP25). Very little river-runoff occurred during this interval. Decreasing terrigenous (riverine) input and synchronous increase of marine produced organic matter around 16 ka until 7.5 ka indicate the gradual establishment of a marine environment in the western Laptev Sea related to the onset of the post-glacial transgression of the shelf. Strong river run-off and reduced sea ice cover characterized the time interval between 15.2 and 12.9 ka, including the Bølling/Allerød warm period (14.7 - 12.9 ka). Moreover, the DIP25 Index (ratio of HBI-dienes and IP25) might document the presence of Atlantic derived water at the western Laptev Sea shelf area. A sudden return to severe sea ice conditions occurred during the Younger Dryas (12.9 - 11.6 ka). This abrupt climate change was observed in the whole circum-Arctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). At the onset of the Younger Dryas, a distinct alteration of the ecosystem (deep drop in terrigenous and phytoplankton biomarkers) may document the entry of a giant freshwater plume, possibly relating to the Lake Agassiz outburst at 13 ka. IP25 concentrations increase and higher values of the PIP25 Index during the last 7 ka reflect a cooling of the Laptev Sea spring season. Moreover, a short-term variability of c. 1.5 thousand years occurred during the last 12 ka, most probably following Bond Cycles.

  15. Ongoing lithospheric removal in the western Mediterranean: Evidence from Ps receiver functions and thermobarometry of Neogene basalts (PICASSO project)

    NASA Astrophysics Data System (ADS)

    Thurner, Sally; Palomeras, Imma; Levander, Alan; Carbonell, Ramon; Lee, Cin-Ty

    2014-04-01

    western Mediterranean tectonic system consists of the Betic Mountains in southern Spain and the Rif Mountains in northern Morocco curved around the back-arc extensional Alboran basin. Multiple tectonic models have been developed to explain the coeval compressional and extensional tectonic processes that have affected the western Mediterranean since the Oligocene. In order to provide constraints on these evolutionary models, we use Ps teleseismic receiver functions (RF), thermobarometric analyses of post-Oligocene basalts, and previous teleseismic tomography images to investigate the lithospheric structure of the region. Ps RFs were calculated using seismic data from 239 broadband seismic stations in southern Iberia and northern Morocco and thermobarometric analysis was performed on 19 volcanic samples distributed throughout the region. The RF images reveal a highly variable Moho depth (˜25 to ˜55 km), as well as a strong positive, sub-Moho horizon between ˜45 and ˜80 km depth beneath the central Betic and Rif Mountains, which we interpret to be the top of the previously imaged Alboran Sea slab. Thermobarometric constraints from magmas in the eastern Betics and Rif indicate mantle melting depths between 40 and 60 km, typical of melting depths beneath mid-oceanic ridges where little to no lithosphere exists. Together, the RF and thermobarometric data suggest ongoing and recent slab detachment resulting from delamination of the continental lithosphere.

  16. Connection of sea level height between Western Pacific and South Indian Ocean in recent decades

    NASA Astrophysics Data System (ADS)

    DU, Y.; Wang, T.; Zhuang, W.; Wang, J.

    2014-12-01

    Based on merged altimetry data and in site observations from tide gauges, we analyzed the fast increasing trend of sea surface height (SSH) in the recent two decades in the tropical Pacific and Indian Ocean. The results of analysis indicated a dynamic connection of SSH between the tropical western Pacific and the southeastern Indian Ocean. The low-frequency variations of SSH propagate westward in the tropical Pacific, enter the Indonesian Seas through the waveguide, and influence the southeastern India Ocean with the Kelvin-Rossby wave transformation. The thermal structure of upper ocean reveals the above adjustment mainly occur in the thermocline. However, the impacts from the Pacific are limited in the southeast Indian Ocean. In the central and west of the south Indian Ocean, local wind dominates the SSH changes in the last two decades. By lead-lag statistic analyses, we identified the cause of interdecadal from the interannual SSH variations. The interannual SSH variations is dominated by ENSO, forced by the anomalous wind along the equatorial Pacific. Whereas, the interdecadal SSH variations results from the off-equatorial wind stress curl, which is closely related to the Pacific Decadal Oscillation. The dynamic connections between the western Pacific and the south Indian Ocean were tested in the baroclinic Rossby wave solution and the numerical experiments based on the nonlinear reduced-gravity dynamics model.

  17. Spatially Explicit Modeling Reveals Cephalopod Distributions Match Contrasting Trophic Pathways in the Western Mediterranean Sea.

    PubMed

    Puerta, Patricia; Hunsicker, Mary E; Quetglas, Antoni; Álvarez-Berastegui, Diego; Esteban, Antonio; González, María; Hidalgo, Manuel

    2015-01-01

    Populations of the same species can experience different responses to the environment throughout their distributional range as a result of spatial and temporal heterogeneity in habitat conditions. This highlights the importance of understanding the processes governing species distribution at local scales. However, research on species distribution often averages environmental covariates across large geographic areas, missing variability in population-environment interactions within geographically distinct regions. We used spatially explicit models to identify interactions between species and environmental, including chlorophyll a (Chla) and sea surface temperature (SST), and trophic (prey density) conditions, along with processes governing the distribution of two cephalopods with contrasting life-histories (octopus and squid) across the western Mediterranean Sea. This approach is relevant for cephalopods, since their population dynamics are especially sensitive to variations in habitat conditions and rarely stable in abundance and location. The regional distributions of the two cephalopod species matched two different trophic pathways present in the western Mediterranean Sea, associated with the Gulf of Lion upwelling and the Ebro river discharges respectively. The effects of the studied environmental and trophic conditions were spatially variant in both species, with usually stronger effects along their distributional boundaries. We identify areas where prey availability limited the abundance of cephalopod populations as well as contrasting effects of temperature in the warmest regions. Despite distributional patterns matching productive areas, a general negative effect of Chla on cephalopod densities suggests that competition pressure is common in the study area. Additionally, results highlight the importance of trophic interactions, beyond other common environmental factors, in shaping the distribution of cephalopod populations. Our study presents a valuable

  18. Chemical contamination baseline in the Western basin of the Mediterranean Sea based on transplanted mussels.

    PubMed

    Andral, Bruno; Galgani, François; Tomasino, Corinne; Bouchoucha, Marc; Blottiere, Charlotte; Scarpato, Alfonso; Benedicto, José; Deudero, Salud; Calvo, Monica; Cento, Alexandro; Benbrahim, Samir; Boulahdid, Moustapha; Sammari, Cherif

    2011-08-01

    The MYTILOS project aimed at drawing up a preliminary report on coastal chemical contamination at the scale of the Western Mediterranean (continental coasts of the Balearic Islands, Sicily, Sardinia, Corsica and Maghreb) based on a transplanted mussels methodology validated along the French coasts since 1996 by Ifremer and the Rhône Méditerranée & Corsica water board. MYTILOS is backed up by the INTERREG III B/MEDOC programme, the PNUE/PAM-MEDPOL and Rhône Méditerranée & Corsica water board. Three cruises (2004, 2005, 2006) have taken place to assess the first state of chemical contamination along the Western Mediterranean shores with the same methodology. Approximately 120 days were spent at sea deploying and retrieving 123 mussel bags. The results obtained for all studied contaminants were equivalent to those obtained along the French coast according the RINBIO network. These similarities relate to both the highest measured levels and background levels throughout the 123 stations. The areas of greatest impact were mainly urban and industrial centers and the outlets of major rivers, with a far higher midsea impact on the dilution of organic compounds than on metals. Metal levels measured in midsea zones were found to be similar to those in natural shellfish populations living along the coast. On a global scale we can observe that the contaminants levels in the Mediterranean Sea are in the same range as in other areas worldwide. Overall, the research demonstrates the reliability of this methodology for marine pollution monitoring, especially in the Mediterranean sea. PMID:20862467

  19. Population Genetic History of Aristeus antennatus (Crustacea: Decapoda) in the Western and Central Mediterranean Sea

    PubMed Central

    Marra, Annamaria; Mona, Stefano; Sà, Rui M.; D’Onghia, Gianfranco; Maiorano, Porzia

    2015-01-01

    Aristeus antennatus is an ecologically and economically important deep-water species in the Mediterranean Sea. In this study we investigated the genetic variability of A. antennatus sampled from 10 sampling stations in the Western and Central Mediterranean. By comparing our new samples with available data from the Western area, we aim to identify potential genetic stocks of A. antennatus and to reconstruct its historical demography in the Mediterranean. We analyzed two regions of mitochondrial DNA in 319 individuals, namely COI and 16S. We found two main results: i) the genetic diversity values consistent with previous data within the Mediterranean and the absence of barriers to gene flow within the Mediterranean Sea; ii) a constant long-term effective population size in almost all demes but a strong signature of population expansion in the pooled sample about 50,000 years B.P./ago. We propose two explanation for our results. The first is based on the ecology of A. antennatus. We suggest the existence of a complex meta-population structured into two layers: a deeper-dwelling stock, not affected by fishing, which preserves the pattern of historical demography; and genetically homogeneous demes inhabiting the fishing grounds. The larval dispersal, adult migration and continuous movements of individuals from “virgin” deeper grounds not affected by fishing to upper fishing areas support an effective ‘rescue effect’ contributing to the recovery of the exploited stocks and explain their genetic homogeneity throughout the Mediterranean Sea. The second is based on the reproduction model of this shrimp: the high variance in offspring production calls for a careful interpretation of the data observed under classical population genetics and Kingman’s coalescent. In both cases, management policies for A. antennatus will therefore require careful evaluation of the meta-population dynamics of all stocks in the Mediterranean. In the future, it will be particularly

  20. Spatially Explicit Modeling Reveals Cephalopod Distributions Match Contrasting Trophic Pathways in the Western Mediterranean Sea

    PubMed Central

    Puerta, Patricia; Hunsicker, Mary E.; Quetglas, Antoni; Álvarez-Berastegui, Diego; Esteban, Antonio; González, María; Hidalgo, Manuel

    2015-01-01

    Populations of the same species can experience different responses to the environment throughout their distributional range as a result of spatial and temporal heterogeneity in habitat conditions. This highlights the importance of understanding the processes governing species distribution at local scales. However, research on species distribution often averages environmental covariates across large geographic areas, missing variability in population-environment interactions within geographically distinct regions. We used spatially explicit models to identify interactions between species and environmental, including chlorophyll a (Chla) and sea surface temperature (SST), and trophic (prey density) conditions, along with processes governing the distribution of two cephalopods with contrasting life-histories (octopus and squid) across the western Mediterranean Sea. This approach is relevant for cephalopods, since their population dynamics are especially sensitive to variations in habitat conditions and rarely stable in abundance and location. The regional distributions of the two cephalopod species matched two different trophic pathways present in the western Mediterranean Sea, associated with the Gulf of Lion upwelling and the Ebro river discharges respectively. The effects of the studied environmental and trophic conditions were spatially variant in both species, with usually stronger effects along their distributional boundaries. We identify areas where prey availability limited the abundance of cephalopod populations as well as contrasting effects of temperature in the warmest regions. Despite distributional patterns matching productive areas, a general negative effect of Chla on cephalopod densities suggests that competition pressure is common in the study area. Additionally, results highlight the importance of trophic interactions, beyond other common environmental factors, in shaping the distribution of cephalopod populations. Our study presents a valuable

  1. Distributions and air-sea fluxes of carbon dioxide in the Western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Gao, Zhongyong; Chen, Liqi; Sun, Heng; Chen, Baoshan; Cai, Wei-Jun

    2012-12-01

    The uptake of carbon dioxide (CO2) by the Arctic Ocean is most likely increasing because of the rapid sea-ice retreat that lifted the barriers preventing gas exchange and light penetration for biological growth. Measurements of atmospheric and surface sea water partial pressure of CO2 (pCO2) were conducted during the Chinese National Arctic Research Expedition (CHINARE) cruises from July to September in 2003 and 2008. The latitudinal distribution of pCO2 along the 169°W transect showed a below-atmopsheric pCO2 level in most of the Western Arctic Ocean, with distinct regional differences from Bering Strait northward to the Central Acrctic Ocean. The average air-sea CO2 fluxes on the shelf and slope of the Chukchi Sea were -17.0 and -8.1 mmol m-2 d-1 respectively. In the ice-free zone, the partially ice-covered zone, and the heavily ice-covered zone of the Canada Basin, the fluxes were -4.2, -8.6, -2.5 mmol m-2 d-1 respectively. These rates are lower than other recent estimates. Our new results not only confirmed previous observations that most areas of the Western Arctic Ocean were a CO2 sink in general, but they also revealed that the previously unsampled central basins were a moderate CO2 sink. Analysis of controlling factors in different areas shows that pCO2 in Bering Strait was influenced not only by the Bering inflow waters but also by the high biological production. However, pCO2 fluctuated sharply because of strong water mixing both laterally and vertically. In the marginal ice zone (Chukchi Sea), pCO2 was controlled by ice melt and biological production, both of which would decrease pCO2 onshore of the ice edge. In the nearly ice-free southern Canada Basin, pCO2 increasd latitudinally as a result of atmospheric CO2 uptake due to intensive gas exchange, increased temperature, and decresed biological CO2 uptake due to limited nutrient supply. Finally, pCO2 was moderately lower than the atmospheric value and was relatively stable under the ice sheet of the

  2. High-resolution record of last post-glacial variations of sea-ice cover and river discharge in the western Laptev Sea (Arctic Ocean)

    NASA Astrophysics Data System (ADS)

    Stein, R. H.; Hörner, T.; Fahl, K.

    2014-12-01

    Here, we provide a high-resolution reconstruction of sea-ice cover variations in the western Laptev Sea, a crucial area in terms of sea-ice production in the Arctic Ocean and a region characterized by huge river discharge. Furthermore, the shallow Laptev Sea was strongly influenced by the post-glacial sea-level rise that should also be reflected in the sedimentary records. The sea Ice Proxy IP25 (Highly-branched mono-isoprenoid produced by sea-ice algae; Belt et al., 2007) was measured in two sediment cores from the western Laptev Sea (PS51/154, PS51/159) that offer a high-resolution composite record over the last 18 ka. In addition, sterols are applied as indicator for marine productivity (brassicasterol, dinosterol) and input of terrigenous organic matter by river discharge into the ocean (campesterol, ß-sitosterol). The sea-ice cover varies distinctly during the whole time period and shows a general increase in the Late Holocene. A maximum in IP25 concentration can be found during the Younger Dryas. This sharp increase can be observed in the whole circumarctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). Interestingly, there is no correlation between elevated numbers of ice-rafted debris (IRD) interpreted as local ice-cap expansions (Taldenkova et al. 2010), and sea ice cover distribution. The transgression and flooding of the shelf sea that occurred over the last 16 ka in this region, is reflected by decreasing terrigenous (riverine) input, reflected in the strong decrease in sterol (ß-sitosterol and campesterol) concentrations. ReferencesBelt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Organic Geochemistry 38 (1), 16e27. Taldenkova, E., Bauch, H.A., Gottschalk, J., Nikolaev, S., Rostovtseva, Yu., Pogodina, I., Ya, Ovsepyan, Kandiano, E., 2010. History of ice-rafting and water mass evolution at the northern Siberian continental margin (Laptev Sea) during Late

  3. Post-glacial variations of sea ice cover and river discharge in the western Laptev Sea (Arctic Ocean) - a high-resolution study over the last 18 ka

    NASA Astrophysics Data System (ADS)

    Hörner, Tanja; Stein, Ruediger; Fahl, Kirsten

    2015-04-01

    Here, we provide a high-resolution reconstruction of sea-ice cover variations in the western Laptev Sea, a crucial area in terms of sea-ice production in the Arctic Ocean and a region characterized by huge river discharge. Furthermore, the shallow Laptev Sea was strongly influenced by the post-glacial sea-level rise that should also be reflected in the sedimentary records. The sea Ice Proxy IP25 (Highly-branched mono-isoprenoid produced by sea-ice algae; Belt et al., 2007) was measured in two sediment cores from the western Laptev Sea (PS51/154, PS51/159) that offer a high-resolution composite record over the last 18 ka. In addition, sterols are applied as indicator for marine productivity (brassicasterol, dinosterol) and input of terrigenous organic matter by river discharge into the ocean (campesterol, ß-sitosterol). The sea-ice cover varies distinctly during the whole time period and shows a general increase in the Late Holocene. A maximum in IP25 concentration can be found during the Younger Dryas. This sharp increase can be observed in the whole circumarctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). Interestingly, there is no correlation between elevated numbers of ice-rafted debris (IRD) interpreted as local ice-cap expansions (Taldenkova et al. 2010), and sea ice cover distribution. The transgression and flooding of the shelf sea that occurred over the last 16 ka in this region, is reflected by decreasing terrigenous (riverine) input, reflected in the strong decrease in sterol (ß-sitosterol and campesterol) concentrations. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Organic Geochemistry 38 (1), 16e27. Taldenkova, E., Bauch, H.A., Gottschalk, J., Nikolaev, S., Rostovtseva, Yu., Pogodina, I., Ya, Ovsepyan, Kandiano, E., 2010. History of ice-rafting and water mass evolution at the northern Siberian continental margin (Laptev Sea) during Late

  4. A major increase in winter snowfall during the middle Holocene on western Greenland caused by reduced sea ice in Baffin Bay and the Labrador Sea

    NASA Astrophysics Data System (ADS)

    Thomas, Elizabeth K.; Briner, Jason P.; Ryan-Henry, John J.; Huang, Yongsong

    2016-05-01

    Precipitation is predicted to increase in the Arctic as temperature increases and sea ice retreats. Yet the mechanisms controlling precipitation in the Arctic are poorly understood and quantified only by the short, sparse instrumental record. We use hydrogen isotope ratios (δ2H) of lipid biomarkers in lake sediments from western Greenland to reconstruct precipitation seasonality and summer temperature during the past 8 kyr. Aquatic biomarker δ2H was 100‰ more negative from 6 to 4 ka than during the early and late Holocene, which we interpret to reflect increased winter snowfall. The middle Holocene also had high summer air temperature, decreased early winter sea ice in Baffin Bay and the Labrador Sea, and a strong, warm West Greenland Current. These results corroborate model predictions of winter snowfall increases caused by sea ice retreat and furthermore suggest that warm currents advecting more heat into the polar seas may enhance Arctic evaporation and snowfall.

  5. From the North-Iberian Margin to the Alboran Basin: A lithosphere geo-transect across the Iberian Plate

    NASA Astrophysics Data System (ADS)

    Carballo, A.; Fernandez, M.; Jiménez-Munt, I.; Torne, M.; Vergés, J.; Melchiorre, M.; Pedreira, D.; Afonso, J. C.; Garcia-Castellanos, D.; Díaz, J.; Villaseñor, A.; Pulgar, J. A.; Quintana, L.

    2015-11-01

    A ~ 1000-km-long lithospheric transect running from the North-Iberian Margin to the Alboran Basin (W-Mediterranean) is investigated. The main goal is to image the changes in the crustal and upper mantle structure occurring in: i) the North-Iberian margin, whose deformation in Alpine times gave rise to the uplift of the Cantabrian Mountains related to Iberia-Eurasia incipient subduction; ii) the Spanish Meseta, characterized by the presence of Cenozoic basins on top of a Variscan basement with weak Alpine deformation in the Central System, and localized Neogene-Quaternary deep volcanism; and iii) the Betic-Alboran system related to Africa-Iberia collision and the roll-back of the Ligurian-Tethyan domain. The modeling approach, combines potential fields, elevation, thermal, seismic, and petrological data under a self-consistent scheme. The crustal structure is mainly constrained by seismic data whereas the upper mantle is constrained by tomographic models. The results highlight the lateral variations in the topography of the lithosphere-asthenosphere boundary (LAB), suggesting a strong lithospheric mantle strain below the Cantabrian and Betic mountain belts. The LAB depth ranges from 180 km beneath the Cantabrian Mountains to 135-110 km beneath Iberia Meseta deepening again to values of 160 km beneath the Betic Cordillera. The Central System, with a mean elevation of 1300 m, has a negligible signature on the LAB depth. We have considered four lithospheric mantle compositions: a predominantly average Phanerozoic in the continental mainland, two more fertile compositions in the Alboran Sea and in the Calatrava Volcanic Province, and a hydrated uppermost mantle in the North-Iberian Margin. These compositional differences allowed us to reproduce the main trends of the geophysical observables as well as the inferred P- and S-wave seismic velocities from tomography models and seismic experiments available in the study transect. The high mean topography of Iberia can be

  6. Late Eocene sea surface cooling of the western North Atlantic (ODP Site 647A)

    NASA Astrophysics Data System (ADS)

    Sliwinska, Kasia K.; Coxall, Helen K.; Schouten, Stefan

    2016-04-01

    The initial shift out of the early Cenozoic greenhouse and into a glacial icehouse climate occurred during the middle to late Eocene and culminated in the abrupt growth of a continental-scale ice cap on Antarctica, during an episode known as the Oligocene Isotope Event 1 (Oi-1) ˜33.7 Ma. Documenting the patterns of global and regional cooling prior to Oi-1 is crucial for understanding the driving force and feedback behind the switch in climate mode. Well-dated high-resolution temperature records, however, remain sparse and the climatic response in some of the most climatically sensitive regions of the Earth, including the high latitude North Atlantic (NA), where today large amounts of ocean heat are exchanged, are poorly known. Here we present a sea surface palaeotemperature record from the late Eocene to the early Oligocene (32.5 Ma to 35 Ma) of ODP Hole 647A based on archaeal tetraether lipids (TEX86H). The site is located in the western North Atlantic (Southern Labrador Sea) and is the most northerly located (53° N) open ocean site with a complete Eocene-Oligocene sequence which yields both calcareous and organic microfossils suitable for detailed proxy reconstructions. Our record agrees with the magnitude of temperature decrease (˜3 ° C sea surface cooling) recorded by alkenones and pollen data from the Greenland Sea, but our higher resolution study reveals that the high latitude NA cooling step occurred about 500 kyrs prior to the Oi-1 Antarctic glaciation, at around ˜34.4 Ma. This cooling can be explained by regional effects related to local NA tectonics including ocean gateways, known to have changed at the time, with potential to effect NA overturning circulation due to adjustments in the thermohaline density balance. Alternatively, the cooling itself may be due to changes in NA circulation, suggesting that global ocean circulation played a role in pre-conditioning the Earth for Antarctic glaciation.

  7. Life history of the deep-sea cephalopod family Histioteuthidae in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Quetglas, Antoni; de Mesa, Aina; Ordines, Francesc; Grau, Amàlia

    2010-08-01

    The life cycle of the two species of the deep-sea family Histioteuthidae inhabiting the Mediterranean Sea ( Histioteuthis reversa and Histioteuthis bonnellii) was studied from monthly samples taken throughout the year during daytime hours by bottom trawl gears. A small sample of individuals found floating dead on the sea surface was also analyzed. Both species were caught exclusively on the upper slope at depths greater than 300 m. Their frequency of occurrence increased with depth and showed two different peaks, at 500-600 m and 600-700 m depth in H. bonnellii and H. reversa, respectively, which might indicate spatial segregation. Maturity stages were assigned using macroscopic determination and confirmed with histological analyses. Although mature males were caught all year round, no mature females were found, which suggests that their sexual maturation in the western Mediterranean takes place deeper than the maximum depth sampled (800 m). In fact, the increase in mean squid size with increasing depth in H. reversa indicates an ontogenetic migration to deeper waters. The individuals of both species found floating dead on the sea surface were spent females which had a relatively large cluster of small atresic eggs and a small number of remaining mature eggs scattered in the ovary and mantle cavity. The sizes of these females were clearly larger than the largest individuals caught with bottom trawls. A total of 12 and 7 different types of prey, belonging to three major taxonomic groups (crustaceans, osteichthyes and cephalopods), were identified in the stomach contents of H. reversa and H. bonnellii, respectively. In both species fishes were by far the main prey followed by crustaceans, whereas cephalopods were found only occasionally. The preys identified, mainly myctophids and natantian crustaceans, indicate that both histioteuthids base their diet on pelagic nictemeral migrators.

  8. The genus Litophyton Forskål, 1775 (Octocorallia, Alcyonacea, Nephtheidae) in the Red Sea and the western Indian Ocean

    PubMed Central

    van Ofwegen, Leen P.

    2016-01-01

    Abstract The Litophyton species of the Red Sea and the western Indian Ocean are revised, which includes species previously belonging to the genus Nephthea, which is synonymized with Litophyton. A neotype for both Litophyton arboreum, the type species of Litophyton, and Nephthea chabrolii, the type species of Nephthea, are designated. The new species Litophyton curvum sp. n. is described and depicted, and a key to all Litophyton species is provided. Of the 26 species previously described from the western Indian Ocean and Red Sea, 13 species are considered valid and 13 have been synonymized or placed in other genera. PMID:27103869

  9. Features and variability of the South China Sea western boundary current from 1992 to 2011

    NASA Astrophysics Data System (ADS)

    Quan, Qi; Xue, Huijie; Qin, Huiling; Zeng, Xuezhi; Peng, Shiqiu

    2016-04-01

    Different from the traditional definition of the South China Sea western boundary current (SCSWBC), in this paper, only the southwestward and southward currents along the northern and western slopes in the SCS, which are closely associated with the basin-wide wind stress curl, are defined as the SCSWBC, while the flows on the southwestern shelf driven directly by the local wind stress are regarded as part of the shelf circulation. Using a new reanalysis dataset of the SCS in conjunction with the in situ and remote sensing data, the main features and variability of the SCSWBC from 1992 to 2011 were studied. Dictated by the prevailing monsoonal winds and in- and outflows, the SCSWBC in winter extended the full length of the western slope and reached its maximum intensity off the southeast coast of Vietnam, while in summer the main body of the SCSWBC was limited to the northern half of the western slope and merged with the northward coastal current to form the Vietnam Offshore Current (VOC) at about 12° N. Moreover, the respective seasonal patterns of the SCSWBC showed pronounced interannual variations in its structure, including the axis, the width, and the maximum depth. The strength of the SCSWBC, with the transport of -11.8 ± 3.5 Sv in winter and -3.0 ± 1.6 Sv in summer off the central coast of Vietnam, also varied significantly from year to year. It was demonstrated that the monsoonal forcing over the SCS, the interannual variability of which was closely associated with El Niño events, played an important role in modulating the interannual variability of the SCSWBC, whereas the influence from the upper-layer Luzon Strait transport was secondary.

  10. Features and variability of the South China Sea western boundary current from 1992 to 2011

    NASA Astrophysics Data System (ADS)

    Quan, Qi; Xue, Huijie; Qin, Huiling; Zeng, Xuezhi; Peng, Shiqiu

    2016-07-01

    Different from the traditional definition of the South China Sea western boundary current (SCSWBC), in this paper, only the southwestward and southward currents along the northern and western slopes in the SCS, which are closely associated with the basin-wide wind stress curl, are defined as the SCSWBC, while the flows on the southwestern shelf driven directly by the local wind stress are regarded as part of the shelf circulation. Using a new reanalysis dataset of the SCS in conjunction with the in situ and remote sensing data, the main features and variability of the SCSWBC from 1992 to 2011 were studied. Dictated by the prevailing monsoonal winds and in- and outflows, the SCSWBC in winter extended the full length of the western slope and reached its maximum intensity off the southeast coast of Vietnam, while in summer the main body of the SCSWBC was limited to the northern half of the western slope and merged with the northward coastal current to form the Vietnam Offshore Current (VOC) at about 12° N. Moreover, the respective seasonal patterns of the SCSWBC showed pronounced interannual variations in its structure, including the axis, the width, and the maximum depth. The strength of the SCSWBC, with the transport of -11.8 ± 3.5 Sv in winter and -3.0 ± 1.6 Sv in summer off the central coast of Vietnam, also varied significantly from year to year. It was demonstrated that the monsoonal forcing over the SCS, the interannual variability of which was closely associated with El Niño events, played an important role in modulating the interannual variability of the SCSWBC, whereas the influence from the upper-layer Luzon Strait transport was secondary.

  11. Intensification of decadal and multi-decadal sea level variability in the western tropical Pacific during recent decades

    NASA Astrophysics Data System (ADS)

    Han, Weiqing; Meehl, Gerald A.; Hu, Aixue; Alexander, Michael A.; Yamagata, Toshio; Yuan, Dongliang; Ishii, Masayoshi; Pegion, Philip; Zheng, Jian; Hamlington, Benjamin D.; Quan, Xiao-Wei; Leben, Robert R.

    2014-09-01

    Previous studies have linked the rapid sea level rise (SLR) in the western tropical Pacific (WTP) since the early 1990s to the Pacific decadal climate modes, notably the Pacific Decadal Oscillation in the north Pacific or Interdecadal Pacific Oscillation (IPO) considering its basin wide signature. Here, the authors investigate the changing patterns of decadal (10-20 years) and multidecadal (>20 years) sea level variability (global mean SLR removed) in the Pacific associated with the IPO, by analyzing satellite and in situ observations, together with reconstructed and reanalysis products, and performing ocean and atmosphere model experiments. Robust intensification is detected for both decadal and multidecadal sea level variability in the WTP since the early 1990s. The IPO intensity, however, did not increase and thus cannot explain the faster SLR. The observed, accelerated WTP SLR results from the combined effects of Indian Ocean and WTP warming and central-eastern tropical Pacific cooling associated with the IPO cold transition. The warm Indian Ocean acts in concert with the warm WTP and cold central-eastern tropical Pacific to drive intensified easterlies and negative Ekman pumping velocity in western-central tropical Pacific, thereby enhancing the western tropical Pacific SLR. On decadal timescales, the intensified sea level variability since the late 1980s or early 1990s results from the "out of phase" relationship of sea surface temperature anomalies between the Indian and central-eastern tropical Pacific since 1985, which produces "in phase" effects on the WTP sea level variability.

  12. Impact of the Pleistocene Glaciations on Net Erosion Development in the Western Barents Sea

    NASA Astrophysics Data System (ADS)

    Zieba, K. J.; Felix, M.

    2015-12-01

    The Barents Sea shelf was subjected to both tectonic- and glacially-driven erosion during the Cenozoic. It is however unclear which of the erosion mechanisms had the most important role in generating net erosion that indicates a total effect of all erosion events. The literature estimates of glacial to tectonic erosion ratio vary significantly and often do not account for regional variations. The tectonic erosion is often attributed to plate reorganization in the Norwegian-Greenland Sea during the Cenozoic. The literature shows wide diversity of opinions regarding timing and thickness of the tectonic erosion. In contrast, glacial erosion thickness estimates are well constrained and show lower discrepancy in results. The glacial erosion thickness estimates are therefore key information that can be used for constraining the ratio between tectonic and glacial erosion. The glacial contribution to the net erosion is however also controlled by on-shelf deposition that counteracts the process of glacial erosion. However the on-shelf deposition rates have never been calculated. In result, the Pleistocene sediment budget and glacial contribution to the net erosion has never been assessed yet. The Pleistocene contribution to the net erosion was approached by a new Monte-Carlo-type method where the Pleistocene-Holocene sediment budget is calculated and the net erosion thickness is determined as a balance between total deposition and erosion thicknesses. The proposed method requires definite ages of glacial and interglacial periods what is not available in the literature. The timeframe was established by using a new approach based on the regional ice-sheet volume curve. Also, the new glacial/interglacial timeframe enables calculating the erosion rates for glacial duration (103 - 104 yr) timescale what have not been performed before. The results show that the western Barents Sea was glaciated during 4 marine isotope stages for a total duration of 29 kyr. The glacial erosion

  13. Wave ensemble forecast in the Western Mediterranean Sea, application to an early warning system.

    NASA Astrophysics Data System (ADS)

    Pallares, Elena; Hernandez, Hector; Moré, Jordi; Espino, Manuel; Sairouni, Abdel

    2015-04-01

    The Western Mediterranean Sea is a highly heterogeneous and variable area, as is reflected on the wind field, the current field, and the waves, mainly in the first kilometers offshore. As a result of this variability, the wave forecast in these regions is quite complicated to perform, usually with some accuracy problems during energetic storm events. Moreover, is in these areas where most of the economic activities take part, including fisheries, sailing, tourism, coastal management and offshore renewal energy platforms. In order to introduce an indicator of the probability of occurrence of the different sea states and give more detailed information of the forecast to the end users, an ensemble wave forecast system is considered. The ensemble prediction systems have already been used in the last decades for the meteorological forecast; to deal with the uncertainties of the initial conditions and the different parametrizations used in the models, which may introduce some errors in the forecast, a bunch of different perturbed meteorological simulations are considered as possible future scenarios and compared with the deterministic forecast. In the present work, the SWAN wave model (v41.01) has been implemented for the Western Mediterranean sea, forced with wind fields produced by the deterministic Global Forecast System (GFS) and Global Ensemble Forecast System (GEFS). The wind fields includes a deterministic forecast (also named control), between 11 and 21 ensemble members, and some intelligent member obtained from the ensemble, as the mean of all the members. Four buoys located in the study area, moored in coastal waters, have been used to validate the results. The outputs include all the time series, with a forecast horizon of 8 days and represented in spaghetti diagrams, the spread of the system and the probability at different thresholds. The main goal of this exercise is to be able to determine the degree of the uncertainty of the wave forecast, meaningful

  14. Rock magnetism of a loess-palaeosol sequence from the western Black Sea shore (Romania)

    NASA Astrophysics Data System (ADS)

    Necula, Cristian; Dimofte, Daniela; Panaiotu, Cristian

    2015-09-01

    The Lower Danube Basin is one of the most important loess regions from Europe, which have provided excellent archives for long-term high-resolution palaeoclimate studies. The aim of this paper is to derive new information on the Middle-Late Pleistocene palaeoenvironment from a high resolution multiproxy assessment of the iron mineralogical composition at the Costineşti loess-palaeosol sequence located on the western Black Sea shore. It is the easternmost loess section in the Romanian loess region studied and its distinct pattern of the proxy records can be used to correlate the lower Danube loess to other key sites of the Moldavia and Ukraine loess regions. To investigate the climatic control on soft and hard ferromagnetic minerals we used several types of rock magnetic properties: magnetic susceptibility and its frequency dependence, anhysteretic remanent magnetization, isothermal remanent magnetization, hysteresis properties and FORC distributions, an unmixing model for isothermal remanent magnetization curves and high field (up to 8 T) isothermal remanence measurements. Our results show that the palaeosol horizons, formed during interglacials and climatically more favored periods of the Pleistocene, experienced pedogenic alteration, resulting in high amounts of superparamagnetic, single domain and pseudosingle domain magnetite/maghemite grains and hematite. The loess layers, formed during glacial periods, are mainly dominated by multidomain and/or pseudosingle domain oxidized magnetite and some hematite, all probably of aeolian origin. Goethite contribution is probably minor and constant both in loess and palaeosol horizons. We review the correlation of the loess sections from the lower Danube basin concluding that the new results can be interpreted as a support for the transition of a Mediterranean type climate to a steppe type climate in the last two interglacial periods in the western Black Sea. Because the pattern of magnetic susceptibility data from the

  15. Distribution of total mercury in surface sediments of the western Jade Bay, Lower Saxonian Wadden Sea, southern North Sea.

    PubMed

    Jin, Huafang; Liebezeit, Gerd; Ziehe, Daniel

    2012-04-01

    A total of 114 surface sediment samples was equidistantly collected in the western part of the Jade Bay, southern North Sea, to analyse total mercury contents as well as grain size distribution and total organic carbon (TOC) contents. Total mercury was determined by oxygen combustion-gold amalgamation. Validation, precision and accuracy of the method were evaluated and controlled with two certified reference materials (HISS-1 and MESS-3). Total mercury contents varied between 8 and 243 ng/g dry sediment with a mean value of 103 ng/g dw. The mercury levels in surface sediments showed an inhomogeneous spatial distribution with higher contents in near-dike areas. The values are mostly in the range of natural background values (50–100 ng/g dw) and positively related to TOC and clay/silt contents (<63 μm). The present total mercury contents are compared to those of previous studies, in order to estimate possible temporal trends of mercury contents in the study area over the last decades. Moreover, the comparison to sediment quality guidelines indicated that the surface sediments of the Jade Bay are not mercury contaminated. These results also suggested that the current mercury contents of Jade Bay surficial sediments are mostly affected by atmospheric deposition and re-emission. PMID:22301998

  16. Now an empty mudflat: past and present benthic abundances in the western Dutch Wadden Sea

    NASA Astrophysics Data System (ADS)

    Kraan, Casper; Dekinga, Anne; Piersma, Theunis

    2011-03-01

    The benthic fauna of two areas in the western Dutch Wadden Sea, Posthuiswad and Staart van Schieringhals, was described in 1930-1960 and again between 1996 and 2005. Here, we document the changes. Whereas both areas formerly had high densities of species that biogenically structured the intertidal mudflats such as mussels Mytilus edulis and cockles Cerastoderma edule, by 1996 they had shown a tenfold decrease in the densities of molluscs, with no recovery till 2005. Although the number of species of polychaetes and crustaceans may not have changed much, their relative abundance did. Nowadays, more polychaete species are common than before. We briefly discuss whether the changes in benthic community composition could be due to industrial fishery practices or eutrophication effects.

  17. Causes of the 1998 Bartin river flood in Western Black Sea region of Turkey.

    PubMed

    Celik, Huseyin E; Aydin, Abdurrahim; Ozturk, Tolga; Dagci, Mehmet

    2006-05-01

    A vast flood in the Western Black Sea region of Turkey in May 1998 caused great loss of life and significant damage. Communication network, transportation, and construction cost of the disaster was estimated around US $500 million. Since flood area was relatively large, only Bartin river watershed were analysed and investigated within the scope of this study. It is very common having intense summer showers, which results in floods and landslides in the region. Land use changes in Turkey are rapid; therefore, actual land use format and its recent change were determined using remote sensing. Geographic Information System (GIS) was employed to evaluate the data collected in the area. Prolonged rainfall on saturated soil by antecedent rainfall; misuse of land both in upper and lower watersheds are main reasons affecting the formation of such a flood in Bartin river watershed. PMID:17436521

  18. One decade of thermohaline variability in the deep western Mediterranean Sea (2004-2014)

    NASA Astrophysics Data System (ADS)

    Schroeder, Katrin; Ismail, S. Ben; Bryden, Harry; Borghini, Mireno; Sparnocchia, Stefania; Chiggiato, Jacopo; Ribotti, Alberto

    2015-04-01

    Recent intense deep water formation events in the western Mediterranean have produced a huge amount of a new deep water. Significantly warmer and saltier than previously, it substituted the resident deep water. The deep structure and properties began to change after winter 2004/2005 and the water rapidly spread towards the interior of the basin, in the direction of the Strait of Gibraltar and within the Tyrrhenian Sea. The changes observed over the past 10 years are substantial: since 2004 we witnessed increases in deep water temperature and salinity 3-4 times faster than during 1961-2004. The possible impacts these changes could have on a global scale are still an open issue.

  19. Stratigraphic architecture of the Pyreneo-Languedocian submarine fan, Gulf of Lions, western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    dos Reis, Antonio Tadeu; Gorini, Christian; Mauffret, Alain; Mepen, Michelle

    2004-02-01

    The Pyreneo-Languedocian submarine sediment body, located in the western sector of the Gulf of Lions, is an example of a fan-like depositional system essentially controlled by salt tectonics. The area was subjected to a combined effect of overburden subsidence into the evacuated salt layer and a significant distal salt thickening, due to preferential basinward salt migration. This mode of salt migration impacted the Quaternary sea-bottom morphology by creating a large midslope topographic low, providing space accommodation for the Pyreneo-Languedocian fan. At gulf scale, the fan is a unique feature because unchannelized sedimentary environment in the area occurs at slope level, thus in minor water depth in relation to all other deep-water sedimentary systems offshore Gulf of Lions. To cite this article: A.T. dos Reis et al., C. R. Geoscience 336 (2004).

  20. Empirical eigenfunction analysis of sea surface temperatures in the Western North Atlantic

    SciTech Connect

    Everson, R.; Cornillon, P.; Sirovich, L. |; Webber, A.

    1996-06-01

    The Karhunen-Lo{grave e}ve decomposition is used to analyze time records of AVHRR sea surface temperature observations of the Western North Atlantic. A manually declouded dataset covering the spring of 1985 is analyzed. The majority (80{percent}) of the variance about the mean is accounted for by an empirical eigenfunction which is identified with seasonal warming. The empirical eigenfunction describes the rates of warming in different regions of the ocean. Additional eigenfunctions associated with the meandering of the Gulf Stream are found. Techniques to deal with missing and partially cloudy data are advanced and applied to relatively cloud-free data selected from the period 1985 to 1991. Again, the dominant effect is identified as seasonal warming. {copyright} {ital 1996 American Institute of Physics.}

  1. Reservoir characters of the Ypresian carbonates, Western Libyan Offshore, Central Mediterranean Sea

    SciTech Connect

    Mriheel, I.Y.

    1995-08-01

    Significant hydrocarbon accumulations have been discovered in Western Libyan offshore in the Ypresian carbonate reservoirs of Jdeir Formation and Jirani Dolomite. The discoveries of hydrocarbons are mainly in structural traps where the Jdeir nummulitic facies and Jirani dolomitic facies B have been structured by salt domes or underlying positive fault blocks. This study investigates the relationship between environments of deposition, diagenesis and reservoir characters of the two main hydrocarbon producing units of the Jdeir and Jirani formations. Petrographic and petrophysical studies indicate that porosity in the Jirani Dolomite is related to diagenesis in meteoric environments, while in the Jdeir reservoir is the result of the environment of deposition and diagenesis. Excellent reservoir porosity of Jdeir nummulitic facies and Jirani dolomitic facies B is related to diagenesis in meteoric water during exposure to subaerial conditions which is considered to be due to lowering of sea level and possibly local uplifting.

  2. Late Holocene Bottom Water Temperature Variations from the Herald Canyon, western Chukchi Sea

    NASA Astrophysics Data System (ADS)

    Barrientos, N.; Coxall, H.; Lear, C. H.; Jakobsson, M.; O'Regan, M.; Pearce, C.; Stranne, C.; Muschitiello, F.; Koshurnikov, A.

    2015-12-01

    We present coupled stable isotope and trace metal records in benthic foraminifera to investigate the variability in past bottom water temperatures (BWT) from Core SWERUS-L2-2-PC1 (8.28 m) collected during the SWERUS-C3 Leg 2 Expedition in 2014. The core was retrieved at 71.7 m water depth from the Herald Trough, western Chukchi Sea. Radiocarbon dates revealed late Holocene linear sedimentation rates allowing the study of the core in high resolution. Preliminary Mg/Ca ratios in Nonionella labradorica and Elphidium excavatum clavatum with paired stable isotopes in Elphidium excavatum clavatum show a shift to either warmer or fresher bottom waters at around 2000-1800 years BP that suggests changes in the Pacific freshwater input via the Bering Strait.

  3. Ocean response to typhoon Nuri (2008) in western Pacific and South China Sea

    NASA Astrophysics Data System (ADS)

    Sun, Jingru; Oey, Lie-Yauw; Chang, Roger; Xu, Fanghua; Huang, Shih-Ming

    2015-05-01

    Typhoon Nuri formed on 18 August 2008 in the western North Pacific east of the Philippines and traversed northwestward over the Kuroshio in the Luzon Strait where it intensified to a category 3 typhoon. The storm weakened as it passed over South China Sea (SCS) and made landfall in Hong Kong as a category 1 typhoon on 22 August. Despite the storm's modest strength, the change in typhoon Nuri's intensity was unique in that it strongly depended on the upper ocean. This study examines the ocean response to typhoon Nuri using the Princeton Ocean Model. An ocean state accounting for the sea-surface temperature (SST) and mesoscale eddy field prior to Nuri was constructed by assimilating satellite SST and altimetry data 12 days before the storm. The simulation then continued without further data assimilation, so that the ocean response to the strong wind can be used to understand processes. It is found that the SST cooling was biased to the right of the storm's track due to inertial currents that rotated in the same sense as the wind vector, as has previously been found in the literature. However, despite the comparable wind speeds while the storm was in western Pacific and SCS, the SST cooling was much more intense in SCS. The reason was because in SCS, the surface layer was thinner, the vorticity field of the Kuroshio was cyclonic, and moreover a combination of larger Coriolis frequency as the storm moved northward and the typhoon's slower translational speed produced a stronger resonance between wind and current, resulting in strong shears and entrainment of cool subsurface waters in the upper ocean.

  4. Phosphorus limitation during a phytoplankton spring bloom in the western Dutch Wadden Sea

    NASA Astrophysics Data System (ADS)

    Ly, Juliette; Philippart, Catharina J. M.; Kromkamp, Jacco C.

    2014-04-01

    Like many aquatic ecosystems, the western Dutch Wadden Sea has undergone eutrophication. Due to changes in management policy, nutrient loads, especially phosphorus decreased after the mid-80s. It is still under debate, however, whether nutrients or light is limiting phytoplankton production in the western Wadden Sea, as studies using monitoring data delivered sometimes opposite conclusions and outcomes were related to years, seasons and approaches used. Clearly, the monitoring data alone were not sufficient. We therefore examined the limiting factors for the phytoplankton spring bloom using different experimental approaches. During the spring bloom in April 2010, we investigated several nutrient regimes on natural phytoplankton assemblages at a long term monitoring site, the NIOZ-Jetty sampling (Marsdiep, The Netherlands). Four bioassays, lasting 6 days each, were performed in controlled conditions. From changes in phytoplankton biomass, chlorophyll-a (Chla), we could conclude that the phytoplankton in general was mainly P-limited during this period, whereas a Si-P-co-limitation was likely for the diatom populations, when present. These results were confirmed by changes in the photosynthetic efficiency (Fv/Fm), in the expression of alkaline phosphatase activity (APA) measured with the fluorescent probe ELF-97, and in the 13C stable isotope incorporation in particulate organic carbon (POC). During our bioassay experiments, we observed a highly dynamic phytoplankton community with regard to species composition and growth rates. The considerable differences in net population growth rates, occurring under more or less similar environmental incubation conditions, suggest that phytoplankton species composition and grazing activity by small grazers were important structuring factors for net growth during this period.

  5. Parasitation of sea trout (Salmo trutta trutta L.) from the spawning ground and German coastal waters off Mecklenburg-Western Pomerania, Baltic Sea.

    PubMed

    Unger, Patrick; Palm, Harry W

    2016-01-01

    A total of 52 sea trouts, Salmo trutta trutta, were studied for parasites, originating from German freshwater streams and coastal waters of the Baltic Sea. While 35 specimens were caught mainly close to the shoreline in the Baltic Sea, 17 were sampled during their spawning migration in Warnow River and other neighboring rivers in Mecklenburg-Western Pomerania. A total of 12 different metazoan parasite species were found in sea trout originating from the Baltic Sea, including five digeneans, two cestodes, three nematodes, and two acanthocephalans. Marine and freshwater species were found. In the migratory trout, seven different parasite species were recorded (one digenean, two cestodes, one nematode, and one acanthocephalan), demonstrating lower parasite diversity and load during the spawning migration compared with the fish from the Baltic Sea. The anisakid nematodes Anisakis simplex (sensu stricto), Contraceacum rudolphii, and Hysterothylacium aduncum were identified by molecular analyses of the ITS-1, 5.8S, ITS-2, and flanking sequences of the rDNA. Together with the digenean Derogenes varicus, Hemiurus communis and H. luehei, and the cestode Diphyllobothrium dendriticum seven new host records for sea trout from the German part of the Baltic Sea are made. PMID:26374539

  6. Drilling below the salt in the Western Mediterranean Sea: the GOLD project

    NASA Astrophysics Data System (ADS)

    Rabineau, M.; Droxler, A. W.; Kuroda, J.; Eguchi, N.; Aslanian, D.; Alain, K.; Gorini, C.

    2011-12-01

    In recent years the Gulf of Lion within the western Mediterranean Sea has become a unique natural laboratory to study both the evolution and interaction of deep processes (geodynamics, tectonics, subsidence, isostasy) and surficial processes (river behavior, sedimentary fluxes, sea-level changes, climatic impacts). We present the three main objectives for the GOLD deep drilling project at the foot of the continental slope (2400 m water depth) in the Gulf of Lion, the only place where the complete high-resolution history of the last 30 Ma of Mediterranean history is recorded in some 7.7 km of sedimentary archive 1) For the substratum: the upper continental crust thins to less than 5 km, and changes laterally to a relatively thin crust with high velocities whose precise nature is still undetermined (Gailler et al., 2009). The aim of the drilling is to reach this crucial zone, which is essential for the understanding of margin formation and the evolution of sedimentary basin (Aslanian et al., 2009). 2) The drilling will allow the dating and characterization of the impact of climate variations on sedimentation in the deep basin. For the Miocene and older sediments the drilling, will yield information about the nature, paleoenvironments and age of deposits enabling an astronomically-tuned Neogene time scale to be refined for the period of Aquitanian through Langhian interval. The Messinian extreme event represents a unique crisis in Earth history. It is a unique case to study the impact of sea-level drop (more than 1000 m, one order of magnitude greater than Late Quaternary glaciations) on sedimentary river behavior, deltaic and evaporitic deposition and ensuing biotic crisis. Deep drilling with the R/V Chikyu is the only way to go through the complete series of evaporites in the Provence Basin, sample the initiation and evolution of the crises, the first deposits related to the lowering of sea-level on the one hand and to the salinity crisis on the other. 3) The

  7. A survey of the summer coccolithophore community in the western Barents Sea

    NASA Astrophysics Data System (ADS)

    Giraudeau, Jacques; Hulot, Vivien; Hanquiez, Vincent; Devaux, Ludovic; Howa, Hélène; Garlan, Thierry

    2016-06-01

    The Barents Sea is particularly vulnerable to large-scale hydro-climatic changes associated with the polar amplification of climate change. Key oceanographical variables in this region are the seasonal development of sea-ice and the location and strength of physico-chemical gradients in the surface and subsurface water layers induced by the convergence of Arctic- and Atlantic-derived water masses. Remote sensing imagery have highlighted the increasing success of calcifying haptophytes (coccolithophores) in the summer phytoplankton production of the Barents Sea over the last 20 years, as a response to an overall larger contribution of Atlantic waters to surface and sub-surface waters, as well as to enhanced sea-ice melt-induced summer stratification of the photic layer. The present study provides a first thorough description of coccolithophore standing stocks and diversity over the shelf and slope of the western Barents Sea from two sets of surface and water column samples collected during August-September 2014 from northern Norway to southern Svalbard. The abundance and composition of coccolithophore cells and skeletal remains (coccoliths) are discussed in view of the physical-chemical-biological status of the surface waters and water column based on in-situ (temperature, salinity, fluorescence) and shore-based (microscope enumerations, chemotaxonomy) measurements, as well as satellite-derived data (Chl a and particulate inorganic carbon contents). The coccolithophore population is characterized by a low species diversity and the overwhelming dominance of Emiliania huxleyi. Coccolithophores are abundant both within the well stratified, Norwegian coastal water - influenced shallow mixed layer off northern Norway, as well as within well-mixed cool Atlantic water in close vicinity of the Polar Front. Bloom concentrations with standing stocks larger than 4 million cells/l are recorded in the latter area north of 75°N. Our limited set of chemotaxonomic data suggests

  8. Reversal process of the South China Sea western boundary current in autumn 2011

    NASA Astrophysics Data System (ADS)

    Zhang, Zhixin; Guo, Jingsong; Guo, Binghuo

    2016-05-01

    Using merged sea level anomaly and absolute geostrophic velocity products from satellite altimetry and Argos drifter data, we analyzed the reversal process of the South China Sea (SCS) western boundary current (SCSwbc) from a summer to winter pattern in 2011 and important oceanic phenomena during this process. Results show that the outbreak time of the northeast monsoon over the southern SCS lagged that over the northern SCS by about 1 month. During the SCS monsoon reversal period, the SCSwbc reversed rapidly into the winter pattern at the Guangdong continental slope in late September. Subsequently, the southward Vietnam coastal boundary current strengthened. However, the northward Natuna Current maintained a summer state until mid-October. Thus, the balance between the southward and northward currents was lost when they met, their junction moved gradually southward. However, a loop current formed southeast of Vietnam because the main stream of the Vietnam Offshore Current (VOC) remained near its original latitude. Meanwhile, the VOC and associated dipole circulation system strengthened. After mid-October, the northward Natuna Current began to weaken, the loop current finally shed, becoming a cool ring. The VOC and its associated dipole sub-basin circulation system also weakened gradually until it disappeared.

  9. In situ autonomous optical radiometry measurements for satellite ocean color validation in the Western Black Sea

    NASA Astrophysics Data System (ADS)

    Zibordi, G.; Mélin, F.; Berthon, J.-F.; Talone, M.

    2015-03-01

    The accuracy of primary satellite ocean color data products from the Moderate Resolution Imaging Spectroradiometer on-board Aqua (MODIS-A) and the Visible/Infrared Imager/Radiometer Suite (VIIRS) is investigated in the Western Black Sea using in situ measurements from the Gloria site included in the ocean color component of the Aerosol Robotic Network (AERONET-OC). The analysis is also extended to an additional well-established AERONET-OC site in the northern Adriatic Sea characterized by optically complex coastal waters exhibiting similarities to those observed at the Gloria site. Results from the comparison of normalized water-leaving radiance LWN indicate biases of a few percent between satellite-derived and in situ data at the center wavelengths relevant for the determination of chlorophyll a concentrations (443-547 nm, or equivalent). Remarkable is the consistency between the annual cycle determined with time series of satellite-derived and in situ LWN ratios at these center wavelengths. Contrarily, the differences between in situ and satellite-derived LWN are pronounced at the blue (i.e., 412 nm) and red (i.e., 667 nm, or equivalent) center wavelengths, confirming difficulties in confidently applying satellite-derived radiometric data from these spectral regions for quantitative analysis in optically complex waters.

  10. In situ autonomous optical radiometry measurements for satellite ocean color validation in the Western Black Sea

    NASA Astrophysics Data System (ADS)

    Zibordi, G.; Mélin, F.; Berthon, J.-F.; Talone, M.

    2014-12-01

    The accuracy of primary satellite ocean color data products from the Moderate Resolution Imaging Spectroradiometer on-board Aqua (MODIS-A) and the Visible/Infrared Imager/Radiometer Suite (VIIRS), is investigated in the Western Black Sea using in situ measurements from the Gloria site included in the Ocean Color component of the Aerosol Robotic Network (AERONET-OC). The analysis is also extended to an additional well-established AERONET-OC site in the northern Adriatic Sea characterized by optically complex coastal waters exhibiting similarities with those observed at the Gloria site. Results from the comparison of normalized-water leaving radiance LWN indicate biases of a few percent between satellite derived and in situ data at the center-wavelengths relevant for the determination of chlorophyll a concentration (443-547 nm, or equivalent). Remarkable is the consistency among the annual cycle determined with time series of satellite-derived and in situ LWN ratios at these center-wavelengths. Contrarily, the differences between in situ and satellite-derived LWN are pronounced at the blue (i.e., 412 nm) and red (i.e., 667 nm, or equivalent) center-wavelengths, suggesting difficulties in confidently applying satellite-derived radiometric data from these spectral regions for quantitative analysis in optically complex waters.

  11. Air-sea temperature decoupling in western Europe during the last interglacial-glacial transition

    NASA Astrophysics Data System (ADS)

    Sánchez Goñi, María Fernanda; Bard, Edouard; Landais, Amaelle; Rossignol, Linda; D'Errico, Francesco

    2013-10-01

    A period of continental ice growth between about 80,000 and 70,000 years ago was controlled by a decrease in summer insolation, and was among the four largest ice expansions of the past 250,000 years. The moisture source for this ice sheet expansion, known as the Marine Isotope Stage (MIS) 5a/4 transition, has been proposed to be the warm subpolar and northern subtropical Atlantic Ocean. However, the mechanism by which glaciers kept growing through three suborbital cooling events within this period, which were associated with iceberg discharge in the North Atlantic and cooling over Greenland, is unclear. Here we reconstruct parallel records of sea surface and air temperatures from marine microfossil and pollen data, respectively, from two sediment cores collected within the northern subtropical gyre. The thermal gradient between the cold air and warmer sea increased throughout the MIS5a/4 transition, and was marked by three intervals of even more pronounced thermal gradients associated with the C20, C19 and C18' cold events. We argue that the warm ocean surface along the western European margin provided a source of moisture that was transported, through northward-tracking storms, to feed ice sheets in colder Greenland, northern Europe and the Arctic.

  12. The Late Permian - Early Triassic Evolution of the Western Barents Sea

    NASA Astrophysics Data System (ADS)

    Planke, S.; Svensen, H.; Faleide, J.; Myklebust, R.

    2013-12-01

    The Permian-Triassic boundary was temporarily associated with formation of the Siberian Traps Large Igneous Province. Major Late Permian and Early Triassic subsidence is documented by seismic reflection data in the East Barents Basin. Further west, basin subsidence and an abrupt change from carbonate and evaporite deposition to clastic sedimentation is recorded by industry seismic and well data in the south and onshore Svalbard in the north. The Permian-Triassic boundary is commonly not preserved either due to non-deposition or erosion, but could be locally preserved in depocenters. A major northwestward prograding clastic delta sourced from the Uralian hinterland reached the Norwegian (western) part of the Barents Sea in the earliest Triassic (Induan). We suggest that the large-scale changes in paleoenviroment, vertical motions, and sedimentary processes in the Barents Sea region were strongly influenced by large-scale changes in mantle dynamics and paleoclimate caused by the Siberian Traps igneous event. By analogy with other Large Igneous Provinces, such as the North Atlantic Volcanic Province, regional uplift and subsidence associated with a rising mantle plume may precede the arrival of the plume at the base of the lithosphere with 10's of millions of years. In contrast, the paleoenvironmental changes and the associated extinction were mainly caused by rapid intrusion of magma into sedimentary basins and voluminous igneous eruptions.

  13. Observations of sound-speed fluctuations in the western Philippine Sea in the spring of 2009.

    PubMed

    Colosi, John A; Van Uffelen, Lora J; Cornuelle, Bruce D; Dzieciuch, Matthew A; Worcester, Peter F; Dushaw, Brian D; Ramp, Steven R

    2013-10-01

    As an aid to understanding long-range acoustic propagation in the Philippine Sea, statistical and phenomenological descriptions of sound-speed variations were developed. Two moorings of oceanographic sensors located in the western Philippine Sea in the spring of 2009 were used to track constant potential-density surfaces (isopycnals) and constant potential-temperature surfaces (isotherms) in the depth range 120-2000 m. The vertical displacements of these surfaces are used to estimate sound-speed fluctuations from internal waves, while temperature/salinity variability along isopycnals are used to estimate sound-speed fluctuations from intrusive structure often termed spice. Frequency spectra and vertical covariance functions are used to describe the space-time scales of the displacements and spiciness. Internal-wave contributions from diurnal and semi-diurnal internal tides and the diffuse internal-wave field [related to the Garrett-Munk (GM) spectrum] are found to dominate the sound-speed variability. Spice fluctuations are weak in comparison. The internal wave and spice frequency spectra have similar form in the upper ocean but are markedly different below 170-m depth. Diffuse internal-wave mode spectra show a form similar to the GM model, while internal-tide mode spectra scale as mode number to the minus two power. Spice decorrelates rapidly with depth, with a typical correlation scale of tens of meters. PMID:24116515

  14. Characterization of a Strain of Fukuyoa paulensis (Dinophyceae) from the Western Mediterranean Sea.

    PubMed

    Laza-Martínez, Aitor; David, Helena; Riobó, Pilar; Miguel, Irati; Orive, Emma

    2016-07-01

    A single cell of the dinoflagellate genus Fukuyoa was isolated from the island of Formentera (Balearic Islands, west Mediterranean Sea), cultured, and characterized by morphological and molecular methods and toxin analyses. This is the first report of the Gambierdiscus lineage (genera Fukuyoa and Gambierdiscus) from the western Mediterranean Sea, which is cooler than its eastern basin. Molecular analyses revealed that the Mediterranean strain belongs to F. paulensis and that it bears LSU rDNA sequences identical to New Zealand, Australian, and Brazilian strains. It also shared an identical sequence of the more variable ITS-rDNA with the Brazilian strain. Toxin analyses showed the presence of maitotoxin, 54-deoxyCTX1B, and gambieric acid A. This is the first observation of the two latter compounds in a Fukuyoa strain. Therefore, both Gambierdiscus and Fukuyoa should be considered when as contributing to ciguatera fish poisoning. Different strains of Fukuyoa form a complex of morphologically cryptic lineages where F. paulensis stands as the most distantly related nominal species. The comparison of the ITS2 secondary structures revealed the absence of CBCs among strains. The study of the morphological and molecular traits depicted an unresolved taxonomic scenario impacted by the low strains sampling. PMID:26686980

  15. Monsoon-driven vertical fluxes of organic pollutants in the western Arabian Sea

    SciTech Connect

    Dachs, J.; Bayona, J.M.; Ittekkot, V.; Albaiges, J.

    1999-11-15

    A time series of sinking particles from the western Arabian Sea was analyzed for aliphatic and polycyclic aromatic hydrocarbons, polychlorinated biphenyls, 4,4{prime}-DDT and 4,4{prime}-DDE, to assess the role of monsoons on their vertical flux in the Indian Ocean. Concurrently, molecular markers such as sterols and linear and branched alkanes were analyzed enabling the characterization of the biogenic sources and biogeochemical processes occurring during the sampling period. Hierarchical cluster analysis (HCA) of the data set of concentrations and fluxes of these compounds confirmed a seasonal variability driven by the SW and NE monsoons. Moreover, the influence of different air masses is evidenced by the occurrence of higher concentrations of DDT, PCBs, and pyrolytic PAHs during the NE monsoon and of fossil hydrocarbons during the SW monsoon. Total annual fluxes to the deep Arabian Sea represent an important removal contribution of persistent organic pollutants, thus not being available for the global distillation process (volatilization and atmospheric transport from low or mid latitudes to cold areas). Therefore, monsoons may play a significant role on the global cycle of organic pollutants.

  16. Clouds, radiation, and the diurnal cycle of sea surface temperature in the tropical Western Pacific

    SciTech Connect

    Webster, P.J.; Clayson, C.A.; Curry, J.A.

    1996-04-01

    In the tropical Western Pacific (TWP) Ocean, the clouds and the cloud-radiation feedback can only be understood in the context of air/sea interactions and the ocean mixed layer. Considerable interest has been shown in attempting to explain why sea surface temperature (SST) rarely rises above 30{degrees}C, and gradients of the SST. For the most part, observational studies that address this issue have been conducted using monthly cloud and SST data, and the focus has been on intraseasonal and interannual time scales. For the unstable tropical atmosphere, using monthly averaged data misses a key feedback between clouds and SST that occurs on the cloud-SST coupling time scale, which was estimated to be 3-6 days for the unstable tropical atmosphere. This time scale is the time needed for a change in cloud properties, due to the change of ocean surface evaporation caused by SST variation, to feed back to the SST variation, to feed back to the SST through its effect on the surface heat flux. This paper addresses the relationship between clouds, surface radiation flux and SST of the TWP ocean over the diurnal cycle.

  17. Reversal process of the South China Sea western boundary current in autumn 2011

    NASA Astrophysics Data System (ADS)

    Zhang, Zhixin; Guo, Jingsong; Guo, Binghuo

    2015-10-01

    Using merged sea level anomaly and absolute geostrophic velocity products from satellite altimetry and Argos drifter data, we analyzed the reversal process of the South China Sea (SCS) western boundary current (SCSwbc) from a summer to winter pattern in 2011 and important oceanic phenomena during this process. Results show that the outbreak time of the northeast monsoon over the southern SCS lagged that over the northern SCS by about 1 month. During the SCS monsoon reversal period, the SCSwbc reversed rapidly into the winter pattern at the Guangdong continental slope in late September. Subsequently, the southward Vietnam coastal boundary current strengthened. However, the northward Natuna Current maintained a summer state until mid-October. Thus, the balance between the southward and northward currents was lost when they met, their junction moved gradually southward. However, a loop current formed southeast of Vietnam because the main stream of the Vietnam Offshore Current (VOC) remained near its original latitude. Meanwhile, the VOC and associated dipole circulation system strengthened. After mid- October, the northward Natuna Current began to weaken, the loop current finally shed, becoming a cool ring. The VOC and its associated dipole sub-basin circulation system also weakened gradually until it disappeared.

  18. The Mesozoic Cenozoic structural framework of the Bay of Kiel area, western Baltic Sea

    NASA Astrophysics Data System (ADS)

    Hansen, Martin Bak; Lykke-Andersen, Holger; Dehghani, Ali; Gajewski, Dirk; Hübscher, Christian; Olesen, Morten; Reicherter, Klaus

    2005-12-01

    A dense grid of multichannel high-resolution seismic sections from the Bay of Kiel in the western Baltic Sea has been interpreted in order to reveal the Mesozoic and Cenozoic geological evolution of the northern part of the North German Basin. The overall geological evolution of the study area can be separated into four distinct periods. During the Triassic and the Early Jurassic, E W extension and the deposition of clastic sediments initiated the movement of the underlying Zechstein evaporites. The deposition ceased during the Middle Jurassic, when the entire area was uplifted as a result of the Mid North Sea Doming. The uplift resulted in a pronounced erosion of Upper Triassic and Lower Jurassic strata. This event is marked by a clear angular unconformity on all the seismic sections. The region remained an area of non-deposition until the end of the Early Cretaceous, when the sedimentation resumed in the area. Throughout the Late Cretaceous the sedimentation took place under tectonic quiescence. Reactivated salt movement is observed at the Cretaceous Cenozoic transition as a result of the change from an extensional to compressional regional stress field. The vertical salt movement influenced the Cenozoic sedimentation and resulted in thin-skinned faulting.

  19. Keep up or drown: adjustment of western Pacific coral reefs to sea-level rise in the 21st century.

    PubMed

    van Woesik, R; Golbuu, Y; Roff, G

    2015-07-01

    Since the Mid-Holocene, some 5000 years ago, coral reefs in the Pacific Ocean have been vertically constrained by sea level. Contemporary sea-level rise is releasing these constraints, providing accommodation space for vertical reef expansion. Here, we show that Porites microatolls, from reef-flat environments in Palau (western Pacific Ocean), are 'keeping up' with contemporary sea-level rise. Measurements of 570 reef-flat Porites microatolls at 10 locations around Palau revealed recent vertical skeletal extension (78±13 mm) over the last 6-8 years, which is consistent with the timing of the recent increase in sea level. We modelled whether microatoll growth rates will potentially 'keep up' with predicted sea-level rise in the near future, based upon average growth, and assuming a decline in growth for every 1°C increase in temperature. We then compared these estimated extension rates with rates of sea-level rise under four Representative Concentration Pathways (RCPs). Our model suggests that under low-mid RCP scenarios, reef-coral growth will keep up with sea-level rise, but if greenhouse gas concentrations exceed 670 ppm atmospheric CO2 levels and with +2.2°C sea-surface temperature by 2100 (RCP 6.0 W m(-2)), our predictions indicate that Porites microatolls will be unable to keep up with projected rates of sea-level rise in the twenty-first century. PMID:26587277

  20. A remote-sensing/GIS application for analysis of sea surface temperature off the western coast of North America

    EPA Science Inventory

    Recent work reports a warming trend in Pacific Ocean temperatures over the last 50 years. Coastal regions along western North America are particularly sensitive to climatic change, an important indicator of which is sea surface temperature (SST). In situ SST measurements (typica...

  1. Causes for intraseasonal sea surface salinity variability in the western tropical Pacific Ocean and its seasonality

    NASA Astrophysics Data System (ADS)

    Li, Yuanlong; Han, Weiqing

    2016-01-01

    Pronounced intraseasonal variability (ISV; 20-90 day) of sea surface salinity (SSS) with a standard deviation of 0.12-0.20 psu is detected in the western tropical Pacific Ocean (PO) from measurements of Aquarius/SAC-D satellite. These variations are not spatially uniform but show distinct regional features. The Hybrid Coordinate Ocean Model (HYCOM) well simulated the observed SSS variations, and a suite of parallel experiments were performed to understand the underlying physical processes. Surface forcing by atmospheric intraseasonal oscillations which are dominated by the Madden-Julian oscillation (MJO) is largely responsible for producing the SSS ISV, while ocean internal variability plays a secondary role. Impact of atmospheric forcing is primarily through precipitation and wind stress-driven oceanic processes. Their relative importance shows spatial variations. They have approximately equal importance in the western equatorial PO west of 155°E and the southwestern tropical PO. Wind stress effect dominates SSS ISV in the equatorial PO east of 155°E, while precipitation effect is larger in the northwestern tropical PO. In comparison, the effect of evaporation induced by wind speed change is smaller. The SSS ISV also shows evident seasonality in some areas, particularly in the far western equatorial basin and southwestern tropical PO. During boreal summer (winter), SSS ISV is enhanced (weakened) in the northwestern PO and weakened (enhanced) in the southwestern PO. Comparing with the strength of atmospheric forcing, seasonal variation of the ocean state, especially the mixed layer depth, is generally more important in causing such seasonality.

  2. Quaternary mass wasting on the western Black Sea margin, offshore of Amasra

    NASA Astrophysics Data System (ADS)

    Dondurur, Derman; Küçük, H. Mert; Çifçi, Günay

    2013-04-01

    In recent years, the western Black Sea margin has become well-studied due to its potential for petroleum plays in relatively deeper waters. In 2010, multi-channel seismic, multibeam bathymetry and Chirp high resolution seismic data were collected in order to define the existing geohazards along the margin, to identify the seabed morphology and to determine mass movement types and their run-out distances. Seismic data indicate that the western Black Sea margin is an unstable region with sediment erosion. Particularly, an unstable area offshore of Amasra in the NW consisting of four slides and four buried debris lobes is named the Amasra mass failure zone. Different types of sliding with varying sizes and different mechanisms are observed. These include sliding in the steep slope zones where block-type sliding occurs, smaller-scale slides on the canyon walls, and relatively larger slides in the Amasra mass failure zone. Block-type sliding is observed on the upper continental slope to the south as well as on the canyon walls. They are formed along the rotational faults and occur due to the gravitational loading on the steep slope zones possibly triggered by local seismic activity. In addition, seven large debris lobes identified in the northern toe of the slope buried in the Quaternary sediments triggered by excess pore pressures due to high sediment input and submarine fluid flow. We suggest that earthquake activity may be an important agent for all kind of mass movements in the area. In addition, we propose that the slides in the Amasra mass failure zone are triggered by excess pore pressures in shallow sediments due to the submarine fluid flow possibly produced from gas hydrate dissociation. Warmer Mediterranean seawater input during the rapid transgression period after the Last Glacial Maximum in the Black Sea together with the rapid sedimentation resulted in destabilization of gas hydrates, which caused excess pore pressures in shallow sediments leading to

  3. Deglacial history of the West Antarctic Ice Sheet in the western Amundsen Sea Embayment

    NASA Astrophysics Data System (ADS)

    Smith, James A.; Hillenbrand, Claus-Dieter; Kuhn, Gerhard; Larter, Robert D.; Graham, Alastair G. C.; Ehrmann, Werner; Moreton, Steven G.; Forwick, Matthias

    2011-03-01

    The Amundsen Sea Embayment (ASE) drains approximately 35% of the West Antarctic Ice Sheet (WAIS) and is one of the most rapidly changing parts of the cryosphere. In order to predict future ice sheet behaviour, modellers require long-term records of ice-sheet melting to constrain and build confidence in their simulations. Here, we present detailed marine geological and radiocarbon data along three palaeo-ice stream tributary troughs in the western ASE to establish vital information on the timing of deglaciation of the WAIS since the Last Glacial Maximum (LGM). We have undertaken multi-proxy analyses of the cores (core description, shear strength, x-radiographs, magnetic susceptibility, wet bulk density, total organic carbon/nitrogen, carbonate content and clay mineral analyses) in order to: (1) characterise the sedimentological facies and depositional environments; and (2) identify the horizon(s) in each core that would yield the most reliable age for deglaciation. In accordance with previous studies we identify three key facies, which offer the most reliable stratigraphies for dating deglaciation by recording the transition from a grounded ice sheet to open marine environments. These facies are: i) subglacial, ii) proximal grounding line, and iii) seasonal open marine. In addition, we incorporate ages from other facies (e.g., glaciomarine diamictons deposited at some distance from the grounding line, such as glaciogenic debris flows and iceberg-rafted diamictons and turbates) into our deglacial model. In total, we have dated 78 samples (mainly the acid insoluble organic (AIO) fraction, but also calcareous foraminifers), which include 63 downcore and 15 surface samples. Through careful sample selection prior to dating, we have established a robust deglacial chronology for this sector of the WAIS. Our data show that deglaciation of the western ASE was probably underway as early as 22,351 calibrated years before present (cal yr BP), reaching the mid-shelf by 13

  4. Multiproxy assessment of Holocene relative sea-level changes in the western Mediterranean: sea-level variability and improvements in the definition of the isostatic signal

    NASA Astrophysics Data System (ADS)

    Vacchi, Matteo; Rovere, Alessio; Marriner, Nick; Morhange, Christophe; Spada, Giorgio; Fontana, Alessandro

    2016-04-01

    After the review of 918 radiocarbon dated Relative Sea-Level (RSL) data-points we present here the first quality-controlled database constraining the Holocene sea-level histories of the western Mediterranean Sea (Spain, France, Italy, Slovenia, Croatia, Malta and Tunisia). We reviewed and standardized the geological RSL data-points using a new multi-proxy methodology based on: (1) modern taxa assemblages in Mediterranean lagoons and marshes; (2) beachrock characteristics (cement fabric and chemistry, sedimentary structures); and (3) the modern distribution of Mediterranean fixed biological indicators. These RSL data-points were coupled with the large number of archaeological RSL indicators available for the western Mediterranean. We assessed the spatial variability of RSL histories for 22 regions and compared these with the ICE-5G VM2 GIA model. In the western Mediterranean, RSL rose continuously for the whole Holocene with a sudden slowdown at ~7.5 ka BP and a further deceleration during the last ~4.0 ka BP, after which time observed RSL changes are mainly related to variability in isostatic adjustment. The sole exception is southern Tunisia, where data show evidence of a mid-Holocene high-stand compatible with the isostatic impacts of the melting history of the remote Antarctic ice sheet. Our results indicate that late-Holocene sea-level rise was significantly slower than the current one. First estimates of GIA contribution indicate that, at least in the northwestern sector, it accounts at least for the 25-30% of the ongoing sea-level rise recorded by Mediterranean tidal gauges. Such contribution is less constrained at lower latitudes due to the lower quality of the late Holocene index points. Future applications of spatio-temporal statistical techniques are required to better quantify the gradient of the isostatic contribution and to provide improved context for the assessment of 20th century acceleration of Mediterranean sea-level rise.

  5. Total Mercury in Surface and Deep Waters in the Western and Eastern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Varde', M.; Cofone, F.; Servidio, A.; Rosselli, A.; Hedgecock, I. M.; Ammoscato, I.; Mannarino, V.; Sprovieri, F.; Gensini, M.; Pirrone, N.

    2014-12-01

    In the framework of the Italian National Research Council (CNR) Med-Oceanor measurement program and as part of the Global Mercury Observation System (GMOS) objectives, we performed two cruise campaigns with the CNR's Research Vessel (RV) Urania, in the western and eastern Mediterranean Basin, in the summers of 2012 and 2013. Total Mercury (THg) concentration in seawater was systematically measured at different depths from the sea bottom to the surface. A total of 155 surface and deep seawater samples at 25 selected stations were collected during the cruise campaigns using a stainless-steel rosette system on which 24 Niskin bottles (10L) were mounted. Continuous monitoring of temperature, conductivity, salinity and oxygen with depth were obtained by CTD measurements. All fluorinated containers were cleaned prior to use following GMOS SOPs. The chemical reagents used were suitable for ultra-trace Hg analysis. After sampling, samples were preserved by adding HCl solution to the sample bottles, which were refrigerated during transportation and analyzed within four weeks of the end of the oceanographic campaign. Sea water samples were analyzed in the laboratory following the US-EPA 1631 method revision E (US-EPA, 2002). To assess the critical issues related to mercury (Hg) contamination and to prevent leakage of Hg through volatilization we used all necessary precautions for sampling, sample stabilization, preservation and subsequent analysis in the laboratory. Quality assurance and quality control were performed using transport blanks, laboratory blanks and use of seawater certified reference materials. The accuracy of the analytical procedures for the determination of THg in sea water was corroborated by participation in a global inter-laboratory comparison study for THg in natural waters. THg concentrations in surface and deep waters found in the Mediterranean basin during the last two cruise campaigns Med-Oceanor as well as the THg measurements in sea water

  6. 3D reflection on the edge of a sinkhole: Evidence from the western Dead Sea shore.

    NASA Astrophysics Data System (ADS)

    Medvedev, B.; Keydar, S.; Al-Zoubi, A.; Abueladas, A.-R.; Ezersky, M.; Trachtman, P.

    2012-04-01

    The formation of sinkholes along the Dead Sea is caused by the rapid decline of the Dead Sea level, as a possible result of human extensive activity. According to one of the geological models the sinkholes in several sites are clustered along a narrow coastal strip developing along lineaments representing faults in NNW direction. In order to understand the relationship between a developing sinkhole and its tectonic environment, a high-resolution (HR) three dimensional (3D) seismic reflection survey was carried out at the western shoreline of the Dead Sea. The purpose of this survey was to estimate future developing sinkhole revealed from south. The survey was conducted at the Mineral Beach located between the Dead Sea shoreline and Route #90, where sinkholes develop in alluvial fan. The field acquisition covers 120m by 60m using 288 shots with 96 channels in 2.5m interval per shot. For energy source we used truck mounted accelerated weight ("Digipulse") and single 10Hz geophone per station. In order to image the new developing fault in details the survey was designed with a full azimuth cover for offsets less than 30m. Preliminary results from processed 3D time volume show sub- horizontal coherent reflectors at approximate depth of 50-80m which incline on closer location to the exposed sinkhole. In addition, a fault with vertical displacement of 10m appears at NNW direction to the exposed sinkhole. The character of the reflectors southward is varies rapidly, suggesting also a presence of horizontal displacement of the fault. This study provides the first 3D HR imaging on the edge of a sinkhole and a nearby fault seen from seismic interpretation and field observations. The results of the seismic interpretation suggest a possible linkage between revealed fault and the sinkholes, field observation and 3D HR imaging. Acknowledgements This publication was made possible through support provided by the U.S. Agency for International Development (USAID) and MERC Program

  7. IBAMar 2.0: 36 years sampling on the Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Aparicio, A.; López-Jurado, J. L.; Balbín, R.; Jansá, J.; Amengual, B.

    2012-04-01

    IBAMar 2.0 is a new database created from the oceanographic data obtained during the development of different oceanographic projects by the Balearic Center of Spanish Institute of Oceanography (IEO) and conducted from 1974 and ongoing in the Western Mediterranean basin (Balearic Sea and Algerian Basin). This database collects data from 27 research projects with 134 oceanographic surveys and 6463 sampling stations. IBAMar 2.0 database covers 36 year sampling and approximately 210,846 km2 in the Western Mediterranean Sea (WM). The effort applied for obtaining this data was growing from less than 100 station/year to more than 700 in the year 2009. IBAMar 2.0 database includes main hydrographic parameters such as pressure, temperature, salinity and others as dissolved oxygen, turbidity, chlorophyll-a and nutrients (nitrates, nitrites, phosphates and silicates). Most of the data from 1990 until now were obtained with multiparametric CTDs, although earlier data corresponding to cast sampling with Niskin bottles were incorporated too. The main goal of this database is to establish a climatology for the most significant variables to study the existence of decadal cycles or long-term trends, trying to better understand the behaviour of the hydrographic conditions of the Spanish Mediterranean coast, at both seasonal and interannual time scale and long term. From these studies is possible to provide answers on topical issues as the thermohaline anomaly of the deep waters of WM, the spatial distribution of dissolved oxygen minimum, or the effects of the Climate Change on the hydrodynamics characteristics of the study area [1]. Future work includes data quality control based on standard protocols like [2] and publishing IBAMar 2.0 (including next surveys) on the website of the Mediterranean Group on Climate Change of IEO (http://www.ma.ieo.es/gcc/). There, the data could be obtained summarized as seasonal climatology. These will include horizontal sections at standard depths

  8. Methodology for filling gaps and forecast in sea level: Applications to the eastern English Channel and the North Atlantic Sea (western France)

    NASA Astrophysics Data System (ADS)

    Turki, Imen; Laignel, Benoit; Kakeh, Nabil; Chevalier, Laetitia; Costa, Stephane

    2014-05-01

    This research was carried out in the framework of the program Surface Water and Ocean Topography (SWOT) which is a partnership between NASA and CNES. Sea level is a key variable in marine, climate, and coastal process studies. In this research, a new methodology was implemented for filling gaps and forecasting the sea level by combining classical harmonic models to high statistical methods. In agreement with previous studies, this work indicates that sea level heights are correlated to climate conditions of sea level pressures (SLP). After averaging out surface waves from the mean sea level, the deterministic tides and the stochastic processes of residual surges were investigated using classical harmonic analyses and a statistical model of autoregressive moving average (ARMA), respectively. The estimation of the residual surges was also investigated together with the SLP. This new methodology was applied to the Atlantic sea and the eastern English Channel (western France). Results have shown that the developed model reproduces the observations with RMSE of 4.5 cm and 7 cm for 12 days and 30 days of gaps, respectively. For medium scales of 6 months, the RMSE reaches 9,2 cm. Larger scales more than 10 months were also statistically reproduced. Accordingly, the proposed model seems to be more promising for filling gaps and estimating the sea level at short- to large- time scales. This new methodology presents a coherent, simple, and easy tool to estimate the deterministic nature of tidal processes and the stochastic framework of residual surges. Key words: sea level forecast, astronomical tides, residual surges, ARMA, sea level pressure.

  9. SSMI Wind Speed Climatology of the Time of Monsoon Wind Offset in the Western Arabian Sea

    NASA Technical Reports Server (NTRS)

    Halpern, David

    2000-01-01

    Forecasting the time of onset of monsoon wind in the western Arabian Sea, which is believed to precede the onset of rainfall along the west coast of India, is an important unsolved problem. Prior to measurements of the surface wind field by satellite, there was an absence of suitable surface wind observations. NASA scatterometer (NSCAT) surface wind vectors revealed that the time of the 1997 onset of 12 m/s southwest monsoon wind speeds in the western Arabian Sea preceded the onset of monsoon rainfall in Goa, India, by 3 - 4 days. Wind speed and direction data were necessary to establish a dynamical mechanism between times of onset of 12 m/s wind speed off Somalia and rainfall in Goa. Except for NSCAT, no satellite scatterometer wind product recorded adequately sampled 2-day 1deg x 1deg averaged wind vectors, which are the required space and time scales, to examine the wind-rain relationship in other years. However, the greater-than-95% steadiness of summer monsoon winds allows an opportunity to use satellite measurements of surface wind speed. The Special Sensor Microwave Imager (SSMI) recorded surface wind speed with adequate sampling to produce a 1-day, 1deg x 1deg data product during 1988 - 1998. SSMI data had been uniformly processed throughout the period. Times of onset of 12 m/s wind speed off Somalia determined with the SSMI data set were 21 May 1988, 24 May 1989, 17 May 1990, 28 May 1991, 8 June 1992, 28 May 1993, 30 May 1994, 7 June 1995, 29 May 1996, 12 June 1997, and 15 May 1998. Uncertainty of the 1992 and 1996 times of onset were increased because of the absence of SSMI data on 6 and 7 June 1992 and on 30 May 1996. Correlations of timing of monsoon wind onset with El Nino will be described. Variability of the time difference between times of onset of 12 m/s wind speed and Goa rainfall will be discussed. At the time of submission of the abstract, the Goa rainfall data have not arrived from the India Meteorological Department.

  10. Seasonal variation of methane in the water column of Arkona and Bornholm Basin, western Baltic Sea

    NASA Astrophysics Data System (ADS)

    Gülzow, W.; Gräwe, U.; Kedzior, S.; Schmale, O.; Rehder, G.

    2014-11-01

    Methane and the hydrographic parameters temperature, salinity and oxygen (T, Sal, O2) were surveyed at several stations and along selected transects in the Arkona and Bornholm Basin, western Baltic Sea, between 2009 and 2012. The methane distribution in the two adjacent basins show annually reoccurring as well as seasonal variations, governed by stratification of the water column during the summer period, enhanced vertical mixing during winter and the frequent inflow of oxygen-rich saline water from the North Sea. The Arkona Basin is characterized by low methane concentrations in the surface water with increasing values towards the bottom water layer. Elevated methane concentrations were found in the bottom layer during the summer period. The Bornholm Basin also shows low methane concentrations in the surface water, but high values in the bottom water layer throughout the year. For anoxic conditions, often prevailing in the Bornholm Basin in summer, a positive correlation between methane and hydrogen sulfide concentrations was observed. Strong depletion in the stable isotopic ratio of methane in the deeper waters of the Bornholm Basin reveals effective oxidation processes. The midwater region from 50 to 70 m water depth in the Bornholm Basin is characterized by a methane-enriched water layer, persistent throughout the survey period. High-resolution hydrographic modelling of the physical driving forces suggest this finding to be caused by intrusion of methane-rich waters originating from the Arkona Basin into the water column of the Bornholm Basin and is shown to be a powerful tool for the interpretation of the development of the methane distribution in space and time.

  11. Coastal and mesoscale dynamics characterization combining glider and altimetry: case study over the Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Jerome, Bouffard; Pascual, Ananda; Ruiz, Simon; Isabelle Pujol, Marie; Faugere, Yannice; Larnicol, Gilles; Tintore, Joaquin

    Satellite altimetry allows a direct computation of geostrophic velocity anomalies. However, conventional altimetry measurements remain largely spurious in coastal zone, due to several factors such as inaccurate geophysical corrections (e.g. atmospheric and tidal signals) as well as environmental issues (land contamination in the altimetric and radiometric footprints). At the present time and in the attempt of future relevant technologies (cf. SWOT satellite), experimen-tal coastal altimeter products are under development (XTRACK, PISTACH, COASTALT. . . ). The main efforts consist in the application of coastal-oriented corrections and the review of the data recovery strategies near the coast. The new coastal altimetric products need to be assessed with independent data before to be used in synergy with other measurements and fully exploited for scientific applications. This is the frame of this study as part of an intensive observational program conducted in the Western Mediterranean Sea. We present here the main outcomes resulting from the combination of coastal altimetry and gliders. Gliders -autonomous underwater vehicles -allow to provide precise and high resolution data complementary to altimetry (temperature, salinity, pressure, velocity. . . ) both at surface and over the whole water column. Since July 2007, several glider missions have been performed along Jason-1, Jason-2 and ENVISAT altimeters. The altimetric sea level anomalies have been processed from both standard and coastal-oriented strategies. Furthermore, new methodologies have also been developed in order to combine surface glider geostrophic velocities (derived from CTD measurements) with integrated currents estimated by the glider (derived from GPS locations every 6 hours). These approaches prove to be very efficient to improve the budget errors and homogenize the physical contents of altimetry and glider data. Further, the combined analysis of the two datasets provides interesting insights of

  12. Flow of pacific water in the western Chukchi Sea: Results from the 2009 RUSALCA expedition

    NASA Astrophysics Data System (ADS)

    Pisareva, Maria N.; Pickart, Robert S.; Spall, M. A.; Nobre, C.; Torres, D. J.; Moore, G. W. K.; Whitledge, Terry E.

    2015-11-01

    The distribution of water masses and their circulation on the western Chukchi Sea shelf are investigated using shipboard data from the 2009 Russian-American Long Term Census of the Arctic (RUSALCA) program. Eleven hydrographic/velocity transects were occupied during September of that year, including a number of sections in the vicinity of Wrangel Island and Herald canyon, an area with historically few measurements. We focus on four water masses: Alaskan coastal water (ACW), summer Bering Sea water (BSW), Siberian coastal water (SCW), and remnant Pacific winter water (RWW). In some respects the spatial distributions of these water masses were similar to the patterns found in the historical World Ocean Database, but there were significant differences. Most notably, the ACW and BSW were transposed in Bering Strait, and the ACW was diverted from its normal coastal pathway northwestward through Herald Canyon. It is argued that this was the result of atmospheric forcing. September 2009 was characterized by an abnormally deep Aleutian Low and the presence of the Siberian High, which is normally absent this time of year. This resulted in strong northerly winds during the month, and mooring data from the RUSALCA program reveal that the ACW and BSW were transposed in Bering Strait for a significant portion of the month. Using an idealized numerical model we show that the Ekman response to the wind can cause such a transposition, and that the consequences of this will persist on the shelf long after the winds subside. This can explain the anomalous presence of ACW in Herald Canyon during the RUSALCA survey.

  13. Middle and Late Weichselian (Devensian) glaciation history of south-western Norway, North Sea and eastern UK

    NASA Astrophysics Data System (ADS)

    Sejrup, H. P.; Nygård, A.; Hall, A. M.; Haflidason, H.

    2009-02-01

    Data from eastern England, Scotland, the northern North Sea and western Norway have been compiled in order to outline our current knowledge of the Middle and Late Weichselian glacial history of this region. Radiometric dates and their geological context from key sites in the region are presented and discussed. Based on the available information the following conclusions can be made: (i) Prior to 39 cal ka and most likely after ca 50 cal ka Scotland and southern Norway were extensively glaciated. Most likely the central North Sea was not glaciated at this time and grounded ice did not reach the shelf edge. (ii) During the time interval between 29 and 39 ka periods with ameliorated climate (including the Ålesund, Sandnes and Tolsta Interstadials) alternated with periods of restricted glaciation in Scotland and western Norway. (iii) Between 29 and 25 ka maximum Weichselian glaciation of the region occurred, with the Fennoscandian and British ice sheets coalescing in the central North Sea. (iv) Decoupling of the ice sheets had occurred at 25 ka, with development of a marine embayment in the northern North Sea (v) Between 22 and 19 ka glacial ice expanded westwards from Scandinavia onto the North Sea Plateau in the Tampen readvance. (vi) The last major expansion of glacial ice in the offshore areas was between 17.5 and 15.5 ka. At this time ice expanded in the north-western part of the region onto the Måløy Plateau from Norway and across Caithness and Orkney and to east of Shetland from the Moray Firth. The Norwegian Channel Ice Stream (NCIS), which drained major parts of the south-western Fennoscandian Ice Sheet, was active at several occasions between 29 and 18 ka.

  14. Messinian seismic Markers in the Western Tyrrhenian Sea: preliminary results from the "METYSS" Cruise (June 2009)

    NASA Astrophysics Data System (ADS)

    Lofi, Johanna; Gaullier, Virginie; Sage, Françoise; Chanier, Franck; Deverchere, Jacques; Gorini, Christian; Maillard, Agnès.; Pascucci, Vincenzo; Sellier, Nicolas; Thinon, Isabelle

    2010-05-01

    This work has been undertaken in the framework of an integrated study of the Messinian Salinity Crisis (MSC, Hsu et al., 1973) seismic makers at the scale of the Mediterranean basin. This new approach is based on multi-site comparative studies and on a unified nomenclature for Messinian sedimentary units and surfaces (Lofi et al., accepted). The objectives are to establish the impact of the MSC event on margins and basins that are characterized by various geodynamical, structural and sedimentary settings. In this scientific context, the Tyrrhenian Sea and especially its western part, constitutes a major target because of its geodynamical evolution. This area is a Neogene back-arc basin opened by continental rifting and oceanic spreading related to the eastward migrating Apennine subduction system (Jolivet et al., 2006). Rifting of the Tyrrhenian Sea started first on the Eastern Sardinian margin during the Tortonian-Messinian times, thus including Messinian deposits potentially syn-rift in some places. For these reasons, the western part of the Tyrrhenian basin is a key-area to document relationships between Messinian deposits and tectonic activity. In addition, this geodynamical evolution rises the question of the paleogeography and paleo-connections with the East Corsica basin, that may have worked as an independent lacustrine basin during the MSC, a topic that is questioned (Thinon et al., 2004). The dataset used in this study consists of 15 seismic high-resolution reflection profiles (±1200 km). They have been acquired during the "METYSS" cruise (June 2009) along the Eastern Sardinian and South-Eastern Corsican margins on the R/V "Téthys II" (INSU-CNRS/CIRMED) (Gaullier et al., 2009). These profiles penetrate up to 1 second TWT below the sea-floor, allowing to clearly image the Plio-Quaternary sequence, Messinian Salinity Crisis deposits and erosion surfaces, down to the basement top. Here, we describe the characteristics (seismic facies, geometry

  15. New relative sea-level curves for the southern Scott Coast, Antarctica: evidence for Holocene deglaciation of the western Ross Sea

    NASA Astrophysics Data System (ADS)

    Hall, Brenda L.; Denton, George H.

    1999-12-01

    Here we present new relative sea-level (RSL) curves developed from Holocene-aged raised beaches along the southern Scott Coast of the western Ross Sea, Antarctica. Fifty-four dates of marine shells, seal skin and elephant seal remains incorporated within raised beaches during storms afford a chronology for these curves. All of the curves show the same pattern and timing of RSL change within a small range of error. The best-dated curve suggests that final unloading of grounded Ross Sea ice from the southern Scott Coast and McMurdo Sound region occurred shortly before 6500 14C yr BP. This age is consistent with glacial geological evidence that places deglaciation between 5730 and 8340 14C yr BP. Our data strongly suggest that grounding-line retreat of the Ross Sea ice sheet southward through the McMurdo Sound region occurred in mid- and late Holocene time. If this is correct, then rising sea level could not have driven ice recession to the present-day grounding line on the Siple Coast, because global deglacial sea-level rise was essentially accomplished by mid-Holocene time.

  16. First in situ observations of the deep-sea carnivorous ascidian Dicopia antirrhinum Monniot C., 1972 in the Western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Mecho, A.; Aguzzi, J.; Company, J. B.; Canals, M.; Lastras, G.; Turon, X.

    2014-01-01

    Dicopia antirrhinum C. Monniot, 1972 is a rare species of deep-sea ascidian belonging to the Family Octacnemidae, reported at depths of 1000-2500 m in European Atlantic waters. Adult individuals have never been reported before in the Mediterranean Sea, where only seven juvenile specimens were found in 1975 at 500 m water depth in the Central basin (Malta). The affinities of these specimens with D. antirrhinum were noted, but lack of some typical characters of the species in juveniles prevented a definite taxonomical identification. No other member of the Octacnemidae has ever been found in the Mediterranean. In this study we describe the sampling of an adult specimen of D. antirrhinum at around 1100 m water depth on the flank of the La Fonera (Palamós) canyon, Northwestern Mediterranean, confirming their presence in the Mediterranean Sea. We also observed 5 individuals of this species on their natural habitat with a Remotely Operated Vehicle (ROV). Our results highlight the potential occurrence of Octacnemidae, the presence of which has been largely overlooked, in several deep-sea canyon areas within the Western Mediterranean basin. These observations are important because they indicate the need for increased sampling effort with new technologies, such as ROVs, in ecologically relevant habitats such as canyons, in order to obtain a more accurate picture of deep-sea biodiversity in the Mediterranean Sea.

  17. Review: Potential catastrophic reduction of sea ice in the western Arctic Ocean: Its impact on biogeochemical cycles and marine ecosystems

    NASA Astrophysics Data System (ADS)

    Harada, Naomi

    2016-01-01

    The reduction of sea ice in the Arctic Ocean, which has progressed more rapidly than previously predicted, has the potential to cause multiple environmental stresses, including warming, acidification, and strengthened stratification of the ocean. Observational studies have been undertaken to detect the impacts on biogeochemical cycles and marine ecosystems of these environmental stresses in the Arctic Ocean. Satellite analyses show that the reduction of sea ice has been especially great in the western Arctic Ocean. Observations and model simulations have both helped to clarify the impact of sea-ice reductions on the dynamics of ecosystem processes and biogeochemical cycles. In this review, I focus on the western Arctic Ocean, which has experienced the most rapid retreat of sea ice in the Arctic Ocean and, very importantly, has a higher rate of primary production than any other area of the Arctic Ocean owing to the supply of nutrient-rich Pacific water. I report the impact of the current reduction of sea ice on marine biogeochemical cycles in the western Arctic Ocean, including lower-trophic-level organisms, and identify the key mechanism of changes in the biogeochemical cycles, based on published observations and model simulations. The retreat of sea ice has enhanced primary production and has increased the frequency of appearance of mesoscale anticyclonic eddies. These eddies enhance the light environment and replenish nutrients, and they also represent a mechanism that can increase the rate of the biological pump in the Arctic Ocean. Various unresolved issues that require further investigation, such as biological responses to environmental stressors such as ocean acidification, are also discussed.

  18. On the glacial erosion of the south-western Barents Sea shelf

    NASA Astrophysics Data System (ADS)

    Sverre Laberg, Jan; Andreassen, Karin; Vorren, Tore O.

    2010-05-01

    The Barents Sea has experienced profound glacial erosion during the late Pliocene and Pleistocene which resulted in the development of a characteristic glacial morphology of the continental shelf and deposition of a several km thick sediment wedge/fan along the western margin prograding into the deep sea. During the middle and late Pleistocene, glacial erosion was most severe beneath the paleo-ice streams of the Barents Sea Ice Sheet and affected mainly the trough areas (~200.000 km2). The total erosion is estimated to 435 - 530 m, the average erosion 0.6 - 0.8 mm/yr and the average sedimentation rates on the continental slope were 18 - 22 cm/kyr. The first-order control on the amount of erosion was probably the glaciations duration and velocity of the ice streams. Erosion by paleo-ice streams affected a larger area (~575.000 km2) during the early and middle Pleistocene because they were less topographically stable due to a less pronounced paleo-relief. Also, glaciotectonism was more extensive during this period. The total erosion was estimated to 330 - 420 m and the average erosion 0.4 - 0.5 mm/yr. The average sedimentation rates were 50 - 64 cm/kyr, 2 - 3 times higher than during the succeeding period. In the late Pliocene - early Pleistocene period, proglacial processes including glacifluvial erosion dominated. The total erosion was found to be 170 - 230 m, the average erosion 0.15 - 0.2 mm/yr and the average sedimentation rates were 16 - 22 cm/kyr. In total, the glacial erosion of the troughs has been relatively high throughout the late Pliocene - Pleistocene period, about 1000 - 1100 m. For the banks the erosion is inferred to have increased from late Pliocene to peak in early - middle Pleistocene, later there has been little erosion in these areas which implies a total of 500 - 650 m of erosion. The average glacial erosion during the whole late Pliocene and Pleistocene period is 38 cm/kyr, one order of magnitude higher than the average glacial erosion of the

  19. Time-Series Photographs of the Sea Floor in Western Massachusetts Bay, 1996 - 2005

    USGS Publications Warehouse

    Butman, Bradford; Dalyander, P. Soupy; Bothner, Michael H.; Lange, William N.

    2008-01-01

    Time-series photographs of the sea floor were obtained from an instrumented tripod deployed in western Massachusetts Bay at LT-A (42? 22.6' N, 70? 47.0' W; 32 m water depth; fig. 1) from December 1989 through September 2005. The photographs provide time-series observations of physical changes of the sea floor, near-bottom water turbidity, and life on the sea floor. Two reports present these photographs in digital form (table 1) and chronological order. U.S. Geological Survey Data Series 265 (Butman and others, 2008a) contains the photographs obtained from December 1989 to October 1996. This report, U.S. Geological Survey Data Series 266 (Butman and others, 2008b), contains photographs obtained from October 1996 through September 2005. The photographs are published in separate reports because the data files are too large for distribution on a single DVD. This report also contains photographs that were published previously in an uncompressed format (Butman and others 2004a, b, and c; table 1); they have been compressed and included in this publication so that all of the photographs are available in the same format. The photographs, obtained every 4 or every 6 hours, are presented as individual photographs (in .png format, each accessible through a page of thumbnails) and as a movie (in .avi format). The time-series photographs taken at LT-A were collected as part of a U.S. Geological Survey (USGS) study to understand the transport and fate of sediments and associated contaminants in Massachusetts Bay and Cape Cod Bay (Bothner and Butman, 2007). This long-term study was carried out by the USGS in partnership with the Massachusetts Water Resources Authority (MWRA) (http://www.mwra.state.ma.us/) and with logistical support from the U.S. Coast Guard (USCG). Long-term oceanographic observations help to identify the processes causing bottom sediment resuspension and transport and provide data for developing and testing numerical models. The observations document seasonal

  20. Tsunami modeling Scenarios for the Western Black Sea, Shabla seismic area

    NASA Astrophysics Data System (ADS)

    Partheniu, Raluca; Diaconescu, Mihai; Ioane, Dumitru; Ionescu, Constantin; Marmureanu, Alexandru

    2015-04-01

    Although a rare natural phenomenon, tsunami type events in the Black Sea had been generated, past studies showing more than twenty events (Altinok Y., 1999). The western Black Sea could mostly be affected by earthquakes generated in Shabla area, the most known event being generated on 31st of March 1901, when an earthquake with Mw = 7.2 triggered tsunami waves up to 5 m height (Papadopoulos et al., 2011). In order to generate a tsunami in the Black Sea area, earthquakes should mainly follow some conditions: a) to have a magnitude Mw > 6.5; b) to have a focal depth h < 40 km and c) to have an inverse or normal fault focal mechanism. A recent earthquake generated in Shabla area on 05.08.2009, at 07:49 UTC, was taken into consideration for running tsunami scenarios. The following parameters were used as initial conditions: earthquake location (Latitude and Longitude) and one plane solution with preset fault parameters (Strike, Dip, Rake, Width, Length). A set of 18 different tsunami modeling scenarios have been run, varying the Magnitude (Mw = 7, 7.5 and 8) and the Depth (5 km, 10 km and 30 km). The software used for generating the tsunami modeling scenarios is Tsunami Analysis Tool (TAT), developed by Joint Research Centre (JRC) of the European Commission. After analyzing and comparing the generated tsunami modeling scenarios, minimum values of magnitude for tsunami waves generation were evaluated for the Shabla seismic source. For some of the scenarios no tsunami waves were generated. The worst case scenario is for a depth of 5 km, a magnitude Mw = 8, the tsunami waves heights reaching 0.8 m in Kranevo (Bulgaria). The maximum wave heights and some of the affected locations for this scenario show that at Costinesti, Mangalia, Techirghiol cities the waves will reach 0.6 m height and respectively 0.5 m at Constanta city. According to these scenarios, the tsunami generated waves can vary as follows: increasing the depth from 5 to 10 and 30 km will lead to lower heights

  1. Speleothem records of western Mediterranean. Hydrological variability along the Last Interglacial Period and marine linkages

    NASA Astrophysics Data System (ADS)

    Torner, Judit; Cacho, Isabel; Moreno, Ana; Stoll, Heather; Belmonte, Anchel; Sierro, Francisco J.; Frigola, Jaime; Martrat, Belen; Fornós, Joan; Arnau Fernández, Pedro; Hellstrom, John; Cheng, Hai; Edwards, R. Lawrence

    2016-04-01

    This study aims to identify and characterize regional hydrological variability in the western Mediterranean region in base to different geochemical parameters (δ18O, δ13C, and Mg/Ca ratios). Speleothems have been recovered from several caves located in southern central Pyrenees one and the others form the Balearic Islands. Their chronologies have been constructed in base on U/Th absolute dating and indicate that the speleothem sequences cover the end of the last interglacial and the glacial inception. One of the most remarkable features of the records is the intense and abrupt shift toward more arid conditions that marks the end of the last interglacial (MIS 5e). Furthermore, our speleothem records also show relatively humid but highly variable hydrological conditions during the interstadial periods from MIS 5c to 5a. These speleothem records have been compared with new generated western Mediterranean marine records from the Balearic Sea (MD99-2343) and Alboran Sea (OPD-977). Marine records include (1) proxies of sea surface temperature and changes in evaporation-precipitation rates based on pair analysis of δ18O and the Mg/Ca ratios in planktonic foraminifera Globigerina bulloides; (2) proxies of deep-water currents associated with the Western Mediterranean Deep Water (WMDW) based on grain size analyses. The results reveal that arid conditions on land were coeval with cold sea surface sub-stages (MIS 5b and 5d), and also with increases in the intensity of the WMDW-related currents. By contrast, humid and hydrological unstable atmosphere conditions were synchronous with sea surface warm sub-stages, and lower WMDW-related currents intensities (MIS 5a, c and e). Consequently, our results highly evidence a strong atmospheric-oceanic coupling, involving parallel changes in both surface but also deep western Mediterranean Sea conditions during the last interglacial period and the glacial inception.

  2. Holocene History of the Bering Sea Bowhead Whale ( Balaena mysticetus) in Its Beaufort Sea Summer Grounds off Southwestern Victoria Island, Western Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Dyke, Arthur S.; Savelle, James M.

    2001-05-01

    The fossil remains of 43 bowhead whales were mapped on the raised beaches of western Wollaston Peninsula, Victoria Island, Canadian Arctic, near the historic summer range limit of the Bering Sea stock in the Beaufort Sea. The elevations and radiocarbon ages of the remains demonstrate that the bowhead ranged commonly into the region following the submergence of Bering Strait at ca. 10,000 14C yr B.P. until ca. 8500 14C yr B.P. During the same interval, bowheads ranged widely from the Beaufort Sea to Baffin Bay. Subsequently, no whales reached Wollaston Peninsula until ca. 1500 14C yr B.P. Late Holocene populations evidently were small, or occupations were brief, in comparison to those of the early Holocene. Although the late Holocene recurrence may relate to the expansion of pioneering Thule whalers eastward from Alaska, there are few Thule sites and limited evidence of Thule whaling in the area surveyed to support this suggestion.

  3. PICASSO Rayleigh wave tomography of the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Palomeras, I.; Liu, K.; Thurner, S.; Levander, A.

    2011-12-01

    The western Mediterranean comprises a diffusive plate boundary between the African and Eurasian plates. The area was under extension in the Mesozoic, when the Atlantic and Tethys oceans opened, and under compression from Cenozoic times to present due African-European convergence. The deformation occupies a wide area from the intra-continental Atlas mountain belt in Morocco to the southern Iberian Massif in Spain. The tectonic history of the area is complicated and several geodynamic models have been suggested. PICASSO (Program to Investigate Convective Alboran Sea System Overturn) is a multidisciplinary, international investigation of the Alboran System and surrounding areas. As part of this program a deployment of a dense array of 83 broadband seismic stations in the area has been done. The stations are deployed in a north-south line from central Spain to the Morocco-Algerian border, crossing part of the Iberian Massif in Spain, the Gibraltar Arc (Betics Mountains in Spain and Rif Mountains in Morocco) and the Middle and High Atlas in Morocco. Additional stations form an areal array around the Alboran Sea, in the Betic Mountains and the Rif Mountains. These stations recorded more than 115 teleseismic events since April 2009, of which we chose 30 with a good signal to noise ratio for the study of the lithosphere and asthenosphere with surface waves. To complement our data and to increase the coverage, the data recorded by the IberArray experiment have also been used. The latter experiment, of the Spanish seismological community, has covered the same region with a uniform 50 km x 50 km grid of broadband stations recording from mid-2007 to mid-2009. Rayleigh phase velocities have been measured using the two-plane-wave method to remove complications due to multi-pathing, and finite-frequency kernels to improve lateral resolution. The phase velocities were inverted for 1D structure on a grid of 0.25 by 0.25 degree. The resulting 3D shear velocity models provide first

  4. Taxonomy of quaternary deep-sea ostracods from the Western North Atlantic ocean

    USGS Publications Warehouse

    Yasuhara, Moriaki; Okahashi, H.; Cronin, T. M.

    2009-01-01

    Late Quaternary sediments from Ocean Drilling Program (ODP) Hole 1055B, Carolina Slope, western North Atlantic (32??47.041??? N, 76??17.179??? W; 1798m water depth) were examined for deep-sea ostracod taxonomy. A total of 13933 specimens were picked from 207 samples and c. 120 species were identified. Among them, 87 species were included and illustrated in this paper. Twenty-eight new species are described. The new species are: Ambocythere sturgio, Argilloecia abba, Argilloecia caju, Argilloecia keigwini, Argilloecia robinwhatleyi, Aversovalva carolinensis, Bythoceratina willemvandenboldi, Bythocythere eugeneschornikovi, Chejudocythere tenuis, Cytheropteron aielloi, Cytheropteron demenocali, Cytheropteron didieae, Cytheropteron richarddinglei, Cytheropteron fugu, Cytheropteron guerneti, Cytheropteron richardbensoni, Eucytherura hazeli, Eucytherura mayressi, Eucytherura namericana, Eucytherura spinicorona, Posacythere hunti, Paracytherois bondi, Pedicythere atroposopetasi, Pedicythere kennettopetasi, Pedicythere klothopetasi, Pedicythere lachesisopetasi, Ruggieriella mcmanusi and Xestoleberis oppoae. Taxonomic revisions of several common species were made to reduce taxonomic uncertainty in the literature. This study provides a robust taxonomic baseline for application to palaeoceanographical reconstruction and biodiversity analyses in the deep and intermediate-depth environments of the North Atlantic Ocean. ?? The Palaeontological Association, 2009.

  5. Morphological characteristics and distribution of Pleuronectidae (Pisces) eggs in the western margin of the East Sea

    NASA Astrophysics Data System (ADS)

    Lee, Soo Jeong; Kim, Jin-Koo

    2016-03-01

    Seven species of Pleuronectidae ( Platichthys stellatus, Kareius bicoloratus, Pseudopleuronectes herzensteini, Microstomus achne, Glyptocephalus stelleri, Hippoglossoides dubius, and Limanda punctatissima) were identified based on eggs collected from the western margin of the East Sea (east coast of Korea), using DNA barcoding. The eggs of P. herzensteini and G. stelleri were relatively widely distributed along the east coast of Korea, whereas those of P. stellatus and K. bicoloratus were narrowly distributed; in particular, the eggs of P. stellatus were restricted to areas near bays. The eggs, which share common morphological characteristics (such as a homogeneous yolk and smooth membrane) were divided into three groups according to egg size: group A (more than 1.60 mm in egg diameter, including genera Hippoglossoides and Microstomus), group B (1.00-1.60 mm, including genera Kareius, Glyptocephalus, and Platichthys), and group C (less than 1.00 mm, including genera Limanda and Pseudopleuronectes). This paper provides an overview of the morphological characteristics of the eggs of the family Pleuronectidae collected from the east coast of Korea. Our approach to the analysis of eggs, based on DNA barcoding, morphological characteristics, and geographic distributions, provides a rapid and accurate basis for identifying spawning areas and spawning periods, thus facilitating the assessment and management of fisheries stocks and resources.

  6. A new species of Speleogobius (Teleostei: Gobiidae) from the Western Mediterraenean Sea.

    PubMed

    Kovačić, Marcelo; Ordines, Francesc; Schliewen, Ulrich K

    2016-01-01

    A new goby species, Speleogobius llorisi sp. nov. (Teleostei: Gobiidae) is described from the circalittoral sea bed at 46-69 m depth off the Balearic Islands, western Mediterranean. Six specimens, four females and two males, of the new species were collected from beam trawl samples carried out on the red algae beds off the south west coast of Mallorca Island. Among others, the main traits that differentiate the new species from the only congeneric species, S. trigloides, are the presence of preopercular head canal with pores γ, δ, ε vs. preopercular head canal absent; a longer snout, equal or longer than eye vs. shorter than eye; lower lip ending anteriorly slightly in front of upper lip vs. upper lip slightly protruding lower lip; scales in lateral series 28 or 29 vs. 26; scales in transverse series 6 vs.7-8. It also differs from S. trigloides in some non-overlapping morphometrics and in coloration. All individuals of the new species were collected from Peyssonnelia beds, beds of red algae dominated by species of the family Peyssonneliaceae. The generic diagnosis of Speleogobius is revised. PMID:27395553

  7. Evaluation of Atlantic bluefin tuna reproductive potential in the western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Aranda, Guillermo; Medina, Antonio; Santos, Agustín; Abascal, Francisco J.; Galaz, Txema

    2013-02-01

    Ovarian tissue samples of Atlantic bluefin tuna (ABFT) spawners (n = 49) caught by purse seine in the Balearic Sea (western Mediterranean) were used to assess the stock reproductive characteristics. The frequency of spawning females estimated by the postovulatory follicle method was 84% and the spawning periodicity 1.2 days. Using an unbiased stereological method, the realized batch fecundity was estimated from counts of postovulatory follicles (POFs), whereas the batch fecundity of the subsequent spawn was estimated by quantification of the number of follicles containing oocytes at maturation stage (OMFs). The number of POFs was used as a reliable proxy of the realized batch fecundity, as it represents the actual number of eggs released in the last spawning event. The average relative realized batch fecundity was estimated to be approximately 48 eggs g- 1 of total body mass. While the absolute batch fecundity was isometrically related to the fork length, the relative batch fecundity was not dependent on fish size, which leads to the assumption that all length classes contribute proportionally to their size, towards the total number of eggs spawned by the broodstock. Size-related variations in the sex ratio were observed in the study area and in other Mediterranean locations; females were more abundant in mid-size classes while males predominated in large-size classes.

  8. Acoustic and visual surveys for bowhead whales in the western Beaufort and far northeastern Chukchi seas

    NASA Astrophysics Data System (ADS)

    Moore, Sue E.; Stafford, Kathleen M.; Munger, Lisa M.

    2010-01-01

    Two types of passive-acoustic survey were conducted to investigate the seasonal occurrence of bowhead whales ( Balaena mysticetus) in the western Beaufort and far northeastern Chukchi seas: (1) an over-winter (2003-04) survey using autonomous recorders deployed northeast of Barrow, Alaska, and (2) a summertime dipping-hydrophone survey along the 2005 NOAA Ocean Exploration (OE) cruise track northwest of Barrow. The longest continuous sampling period from the over-winter survey was 3 October 2003 to 12 May 2004. During that period, bowhead whale calls were recorded from 3 to 23 October, intermittently on 6-7 and 22-23 November, then not again until 25 March 2004. Bowhead calls were recorded almost every hour from 19 April to 12 May 2004, with a call rate peak on 30 April ( ca. 9400 calls) and a few instances of patterned calling (or, "song") detected in early May. Bowhead whale calls were never detected during the NOAA OE cruise, but calls of beluga whales ( Delphinapterus leucas) were recorded at 3 of 16 acoustic stations. Opportunistic visual surveys for marine mammals were also conducted during the NOAA OE cruise from the ship (65 h) and helicopter (7.8 h), resulting in single sightings of bowhead whales (3-5 whales), beluga (16-20 whales), walrus (1), polar bear (2=sow/cub), and 17 sightings of 87 ringed seals from the ship and 15 sightings of 67 ringed seals from the helicopter.

  9. Polycyclic aromatic hydrocarbons in sediments and mussels of the western Mediterranean Sea

    SciTech Connect

    Baumard, P.; Budzinski, H.; Garrigues, P.

    1998-05-01

    The distribution of polycyclic aromatic hydrocarbons (PAHs) has been investigated in superficial sediments and mussels (Mytilus galloprovincialis) of the western Mediterranean sea. The analyses were performed by gas chromatography coupled to mass spectrometry (GC-MS). The PAH concentrations ranged from 1 to 20,500 ng/g in the sediments. Different molecular indices allowed differentiation between the different pollutant sources. On the French coast, PAHs originated mainly from incomplete combustion of organic matter (pyrolytic origin), whereas for some sites in Corsica and Sardinia an overimposition of petrogenic PAHs occurred. The mussel PAH concentrations ranged from 25 to 390 ng/g. The total and individual PAH bioaccumulation factors were calculated. The correlation between sediment and mussel PAH content was discussed in terms of bioavailability. It was possible to distinguish different absorption routes for the xenobiotics according to their physicochemical properties. Because the mussel distribution of phenanthrene and anthracene seems to be governed by their water solubility, these compounds were probably mainly absorbed as the water-dissolved form, whereas the heavier molecular weight PAHs (more than four aromatic rings), whose sediment and mussel concentrations are correlated with higher correlation coefficients than for phenanthrene and anthracene, were probably mainly absorbed as adsorbed on particles. Furthermore, a possible preferential biotransformation of benzo[a]pyrene over benzo[e]pyrene is discussed.

  10. Spanish economic exclusive zone (zeee) project: valencia trough and balearic sea (western mediterranean) results.

    NASA Astrophysics Data System (ADS)

    Pérez Carrillo, F.; Palomo, C.; Martín Davila, J.; Carbó, A.; Acosta, J.; Catalán, M.; Herranz, P.; Muñoz Martín, A.; Muñoz Recio, A.; Marín, J. A.

    2003-04-01

    On 1993, the Spanish Government decided to perform a systematic hydrographic/oceanographic study of the so called "Spanish Exclusive Economic Zone" (ZEEE), that is, the marine area surrounding Spanish coast within the 200 nm limit. To achieve it, the oceanographic ship "Hespérides" would be at disposal of the Defense Ministry during one moth a year. A "ZEEE-Plan" was established on 1994 with the main objective to improve cartography of the ZEEE zone and acquire different geophysical parameters to characterize it. A "ZEEE-group" was conformed by personnel coming from the Hydrographic Institute of the Spanish Navy (IHM) and the Spanish Oceanographic Institute (IEO), the Institutions responsible of the campaigns, as well as San Fernando Naval Observatory (ROA), University Complutense of Madrid (UCM), and others. From 1995 to 1997 systematic marine campaigns were carried out at the Valencia Trough and Balearic Sea (Western Mediterranean), complemented by two additional campaigns, carried out on 1999 and 2000. As a result of those campaigns maps of Bathymetry, Geomagnetic Anomalies and Free Air/Bouguer Gravity Anomalies have been published, six maps of 1:200.000 scale and one additional map, of 1:500.000 scale, for the whole area (the maps are available at IEO: Juan.acosta@md.ieo.es, fax: +34 914135597, and IHM: fax: +34 956599396). In this work the above mentioned results will be presented, together with the main characteristics of the surveys.

  11. Detecting hot-spots of bivalve biomass in the south-western Baltic Sea

    NASA Astrophysics Data System (ADS)

    Darr, Alexander; Gogina, Mayya; Zettler, Michael L.

    2014-06-01

    Bivalves are among the most important taxonomic groups in marine benthic communities in nutrient cycling via benthic-pelagic coupling and as food source for higher trophic levels. Additionally, bivalve species combine several autecological features with potential value for assessment and management purposes. Therefore, the demand for quantitative distribution maps of bivalves is high both in research with focus on functional ecology of marine benthos and in policy. In our study, we modelled and mapped the distribution of biomass of soft- and hard-bottom bivalves in the south-western Baltic Sea using Random Forest algorithms. Models were achieved for ten of the most frequent of overall 29 identified species. The distribution of bivalve biomass was mainly influenced by the abiotic parameters salinity, water depths, sediment characteristics and the amount of detritus as a proxy for food availability. Three hot-spots of bivalve biomass dominated by different species were detected: the oxygen-rich deeper parts of the Kiel Bay dominated by Arctica islandica, the shallow areas close to the mouth of the river Oder dominated by Mya arenaria and the hard-substrates around Rügen Island and the shallow Adlergrund dominated by Mytilus spp. The attained maps provide a good basis for further functional and applied analysis.

  12. Low-salinity-induced surface sound channel in the western sea of Jeju Island during summer.

    PubMed

    Kim, Juho; Kim, Hansoo; Paeng, Dong-Guk; Bok, Tae-Hoon; Lee, Jongkil

    2015-03-01

    Surface salinity in the western sea of Jeju Island in Korea becomes low due to the inflow of the Chinese coastal waters during summer. One of the characteristics of low salinity water is the formation of a surface sound channel (SSC) due to the decrease in sound speed by salinity. However, a quantitative analysis between low salinity water and SSC has not been fully investigated yet. In this paper, a temperature-salinity (T-S) gradient diagram is introduced in order to assess SSC formation and its acoustic characteristics are also investigated through a case study of low salinity waters. Maximum angles of limiting rays were less than 4.6° and low frequency cutoffs were higher than 2.0 kHz for the SSCs formed in low salinity water. When the salinity gradients were large (>0.5 psu/m), a SSC was formed more efficiently than other cases whose salinity gradients were small. On the other hand, a SSC was not formed in spite of highly positive salinity gradients when the amount of temperature gradients was negatively high enough (<-0.5 °C/m). However, the acoustic energy transfer in the surface ducts was dependent on frequency and position of source. PMID:25786968

  13. Eddy properties in the Western Mediterranean Sea from satellite altimetry and a numerical simulation

    NASA Astrophysics Data System (ADS)

    Escudier, Romain; Renault, Lionel; Pascual, Ananda; Brasseur, Pierre; Chelton, Dudley; Beuvier, Jonathan

    2016-06-01

    Three different eddy detection and tracking methods are applied to the outputs of a high-resolution simulation in the Western Mediterranean Sea in order to extract mesoscale eddy characteristics. The results are compared with the same eddy statistics derived from satellite altimetry maps over the same period. Eddy radii are around 30 km in altimetry maps whereas, in the model, they are around 20 km. This is probably due to the inability of altimetry maps to resolve the smaller mesoscale in the region. About 30 eddies are detected per day in the basin with a very heterogeneous spatial distribution and relatively short lifespans (median life around 13 days). Unlike other areas of the open ocean, they do not have a preferred direction of propagation but appear to be advected by mean currents. The number of detected eddies seems to present an annual cycle when separated according to their lifespan. With the numerical simulation, we show that anticyclones extend deeper in the water column and have a more conic shape than cyclones.

  14. PICASSO: Lithosphere Structure in the Western Mediterranean from Ps Receiver Functions and Rayleigh Wave Tomography

    NASA Astrophysics Data System (ADS)

    Palomeras, I.; Thurner, S.; Levander, A.; Humphreys, E.; Miller, M. S.; Carbonell, R.; Gallart, J.

    2012-04-01

    The western Mediterranean is a diffuse plate boundary separating the African and Eurasian plates. Cenozoic deformation is centered on the Gibraltar arc and Alboran Sea, and occupies a wide area from the southern Iberian Massif in Spain to the Atlas Mountains in Morocco. We present a model of the lithospheric structure of this region derived from Rayleigh wave tomography and Ps receiver functions, using data from the PICASSO (Program to Investigate Convective Alboran Sea System Overturn) linear broadband array of ~100 seismographs. This array is deployed from central Spain to the Morocco-Algerian border. We complement these data with some of that recorded by IberArray, an areal broadband array, operated by the Spanish seismological community, covering the same region with a uniform 50 km x 50 km grid of stations. Rayleigh phase velocities have been measured from 20-167s period using the two-plane-wave method to remove complications due to multi-pathing, and finite-frequency kernels to improve lateral resolution. The phase velocities were inverted for 1D structure on a 0.25 by 0.25 degree grid. Ps receiver functions at 1Hz and 2Hz were calculated for the same area using water-level and time-domain iterative deconvolution, and were then CCP stacked. The Rayleigh wave shear velocity model, jointly interpreted with the discontinuity structure from the CCP stack, shows the first-order lithospheric structure, and the lithosphere-asthenosphere boundary (LAB). From north to south along the PICASSO profile: The lithosphere is ~120 km thick beneath the Iberian Massif, where it has the highest shear velocity, 4.45 km/s. To the south the lithosphere thins dramatically beneath the Betic Mountains to ~85 km, and then varies in thickness and decreases in velocity beneath the Alboran Sea and Gibraltar Arc. The thinnest lithosphere, ~60 km, is observed beneath the Rif mountains and Middle Atlas, with a low velocity feature (4.2 km/s) at ~60 km depth beneath a site of Late Cenozoic

  15. A new hybrid model for filling gaps and forecast in sea level: application to the eastern English Channel and the North Atlantic Sea (western France)

    NASA Astrophysics Data System (ADS)

    Turki, Imen; Laignel, Benoit; Kakeh, Nabil; Chevalier, Laetitia; Costa, Stephane

    2015-04-01

    This research is carried out in the framework of the program Surface Water and Ocean Topography (SWOT) which is a partnership between NASA and CNES. Here, a new hybrid model is implemented for filling gaps and forecasting the hourly sea level variability by combining classical harmonic analyses to high statistical methods to reproduce the deterministic and stochastic processes, respectively. After simulating the mean trend sea level and astronomical tides, the nontidal residual surges are investigated using an autoregressive moving average (ARMA) methods by two ways: (1) applying a purely statistical approach and (2) introducing the SLP in ARMA as a main physical process driving the residual sea level. The new hybrid model is applied to the western Atlantic sea and the eastern English Channel. Using ARMA model and considering the SLP, results show that the hourly sea level observations of gauges with are well reproduced with a root mean square error (RMSE) ranging between 4.5 and 7 cm for 1 to 30 days of gaps and an explained variance more than 80 %. For larger gaps of months, the RMSE reaches 9 cm. The negative and the positive extreme values of sea levels are also well reproduced with a mean explained variance between 70 and 85 %. The statistical behavior of 1-year modeled residual components shows good agreements with observations. The frequency analysis using the discrete wavelet transform illustrate strong correlations between observed and modeled energy spectrum and the bands of variability. Accordingly, the proposed model presents a coherent, simple, and easy tool to estimate the total sea level at timescales from days to months. The ARMA model seems to be more promising for filling gaps and estimating the sea level at larger scales of years by introducing more physical processes driving its stochastic variability.

  16. 3D subduction modelling of the Betic-Rif Alboran region.

    NASA Astrophysics Data System (ADS)

    Chertova, M.; Geenen, T.; van den Berg, A. P.; Spakman, W.

    2012-04-01

    Our project is concerned with the 4D evolution of Western-Mediterranean region from ~30 Ma until the Present. Slab rollback and lithosphere tearing play an important role in the evolution of this region and affects the development of surface geology (Spakman and Wortel(1)). The project was started with 2D numerical simulations of self-consistent slab rollback for the different model setup. We investigate the influence of different boundary conditions (open boundaries versus closed boundaries), different domain size and different far-field generated intraplate stresses applied to the overriding plate on the subduction process. We have found that free slip implemented either on the both sides of the domain or on one side leads to results that are influenced by the boundary for any reasonable domain size. For the model with open boundary conditions such an influence is only observed in the magnitude of the velocity, which can be successfully scaled by an iterative procedure. Thereby, the model with open boundaries allows us to investigate the subduction dynamic process under conditions that are free from disturbing boundary influences. By being able to model the subduction process in a smaller domain size we significantly decrease computational expenses. Generally our research is now focused on 3D models. We start from the reconstruction of the subduction process in the Betic-Rif Alboran region. This region has a long and complicated subduction history, which consists of slab rollback, lithosphere detachment and tearing processes leading to a narrow curved subduction zone (Spakman and Wortel, 2004). So far analogue models failed to reconstruct such a high-curved structure. We have implemented and tested the open boundary conditions in a 3D setting, which allowed us to significantly decrease the domain size. Different initial plate tectonic settings and kinematic boundary conditions are now being tested in order to reconstruct this complex subduction process. Spakman

  17. Wind induced energy-momentum distribution along the Ekman-Stokes layer. Application to the Western Mediterranean Sea climate

    NASA Astrophysics Data System (ADS)

    Sayol, J. M.; Orfila, A.; Oey, L.-Y.

    2016-05-01

    Wind-wave interaction in the Western Mediterranean Sea is analyzed using 16 years of model data. The mass transport and energy distribution due to wind and waves are integrated through the Ekman-Stokes layer and then spatially and seasonally analyzed. The Stokes drift is estimated from an empirical parameterization accounting for local surface wind and the significant wave height. The impact of the Stokes drift depends on wind variability at the ocean surface and also on the geographical configuration of the basin. The Western Mediterranean Sea has on average a wind energy input two times higher in winter than in summer, and the Stokes-Ekman mass transport interaction term contributes approximately 10-15% of the total wind induced transport, but at some locations the contribution is as much as 40% or more.

  18. Satellite and hydrography observations of the riverine water dynamics in the Black Sea north-western shelf

    SciTech Connect

    Ilyin, Y.P.; Lemeshko, E.M.; Allewijn, R.

    1997-08-01

    Satellite thermal and visible imagery allow to describe the spatial distribution and time evolution of the turbid desalinated water plumes expanding from the principal rivers (Danube, Dnieper and Dniester). The main amount of river inflows is transported to the south along the western coast of the Black Sea. But in spring and summer, they often turn eastward and flow within thin surface layer into the outer shelf region. Their expansion is under the wind control (enforcing of western, Southwestern winds). Coastal upwelling of the underlying cold transparent water is produced under these conditions which separates the river plum from the shore. Sometimes, the intensive small-scale eddies generation is observed at the outer front of plum. The part of turbid desalinated water is trapped by quasi-stationary anticyclonic eddies at the shelf edge and transferred into the central (deep-water) region of the sea.

  19. Keep up or drown: adjustment of western Pacific coral reefs to sea-level rise in the 21st century

    PubMed Central

    van Woesik, R.; Golbuu, Y.; Roff, G.

    2015-01-01

    Since the Mid-Holocene, some 5000 years ago, coral reefs in the Pacific Ocean have been vertically constrained by sea level. Contemporary sea-level rise is releasing these constraints, providing accommodation space for vertical reef expansion. Here, we show that Porites microatolls, from reef-flat environments in Palau (western Pacific Ocean), are ‘keeping up’ with contemporary sea-level rise. Measurements of 570 reef-flat Porites microatolls at 10 locations around Palau revealed recent vertical skeletal extension (78±13 mm) over the last 6–8 years, which is consistent with the timing of the recent increase in sea level. We modelled whether microatoll growth rates will potentially ‘keep up’ with predicted sea-level rise in the near future, based upon average growth, and assuming a decline in growth for every 1°C increase in temperature. We then compared these estimated extension rates with rates of sea-level rise under four Representative Concentration Pathways (RCPs). Our model suggests that under low–mid RCP scenarios, reef-coral growth will keep up with sea-level rise, but if greenhouse gas concentrations exceed 670 ppm atmospheric CO2 levels and with +2.2°C sea-surface temperature by 2100 (RCP 6.0 W m−2), our predictions indicate that Porites microatolls will be unable to keep up with projected rates of sea-level rise in the twenty-first century. PMID:26587277

  20. Offshore seismicity in the western Marmara Sea, Turkey, revealed by ocean bottom observation

    NASA Astrophysics Data System (ADS)

    Yamamoto, Yojiro; Takahashi, Narumi; Citak, Seckin; Kalafat, Doǧan; Pinar, Ali; Gürbüz, Cemil; Kaneda, Yoshiyuki

    2015-04-01

    The North Anatolian Fault (NAF) extends 1600 km westward from a junction with the East Anatolian Fault at the Karliova Triple Junction in eastern Turkey, across northern Turkey and into the Aegean Sea, accommodating about 25 mm/yr of right-lateral motion between Anatolia and the Eurasian plate. Since 1939, devastating earthquakes with magnitude greater than seven ruptured NAF westward, starting from 1939 Erzincan (Ms=7.9) at the eastern Turkey and including the latest 1999 Izmit-Golcuk (Ms=7.7) and the Duzce (Ms=7.4) earthquakes in the Marmara region. Considering the fault segments ruptured by the May 24th, 2014 Northern Aegean earthquake (Mw=6.9), the only un-ruptured segments left behind the 1600 km long NAF locate beneath the Marmara Sea and those segments keep their mystery due to their underwater location. To consider the earthquake hazard and disaster mitigation, the detailed information about fault geometry and its stick-slip behavior beneath the western Marmara Sea is very important. Thus, we started to operate a series of ocean bottom seismographic (OBS) observations to estimate the fault geometry from microearthquake distribution. As a first step, we deployed 3 pop-up type OBSs on 20th of March 2014 as a trial observation, and recovered them on 18th of June 2014. Although one of the OBSs worked only 6 days from the start of the observation, other two OBSs functioned properly during the whole 3-month observation period. We first searched for the microearthquakes missing by the land seismic network and estimated their precious location by using the initial 6 days data, i.e., using all the temporary OBS stations. Although there are only 3 earthquakes listed on the Kandilli Observatory and Earthquake Research Institute (KOERI) catalogue, we could identify 41 earthquakes with more than 5 picking data of P and S first arrivals, and two-third of them located within the OBS network. We found the earthquake cluster along the main NAF and whose depth interval is 12

  1. Ecological state of North -Western Black Sea macrobenthos on offshore bottoms deeper than 50 m

    NASA Astrophysics Data System (ADS)

    Gomoiu, M.-T.; Begun, T.; Teaca, A.

    2009-04-01

    In the last 10-15 years researches concerning benthos in the north-western Black Sea were focused mainly on inshore bottoms, usually less than 50 m deep, where important ecological changed occurred. The offshore bottoms, deeper than 50 m, and especially the periazoic level at the edge of the continental shelf have been less known, the information being scarce. The present study gathers the results of the researches carried out in the past 12 years on the Modiolus phaseolinus community, including the periazoic level, and allows a comparison to be drawn with the situation of the so-called "ecological stability" period at the beginning of the 1960s, before the ecosystemic disturbances began in the Black Sea. In 1995-2007, a number of 133 quantitative macro-benthos samples were collected at depths of 50 - 213 m by means of the van Veen-type grab and box corer; these samples were taken during several cruises (R/V "Prof.Vodyanitskyi" EROS 1995, 1997, R/V „Akademik" 2003, R/V „Parshin" 2005, R/V „Akademik" 2006 R/V „Mare Nigrum" 2006 and 2007), the researches aiming at the assessment of the benthic ecosystem state. The analyses of the 133 samples helped identify 191 taxa (Vermes - 88, Mollusca - 24, Crustacea - 32 and Varia - 47), approximately 60% of the total number of species recorded in the north-western Black Sea during the period of "ecological prosperity". The mean abundance of the benthic populations was 4,836.2 indvs.m-2 for density and 189.9 g.m-2 for biomass. Most macrobenthic taxa occurred in the samples accidentally; out of the 191 taxa recorded, 60 taxa had a frequency of 1-2%, 37 taxa 2-5%, 28 taxa 5-10%, 32 taxa 10-20%, 26 taxa 20-50% and only eight species had a frequency over 50% (Modiolus phaseolinus, Terebelides stroemi, Capitella capitata, Nephtys hombergi, Amphiura stepanovi, Sphaerosyllis bulbosa, Apseudes ostroumovi and Phyllodoce lineata). Numerical abundances were dominated by worms (2,606.9 indvs.m-2) and molluscs (1,398.7 indvs.m-2

  2. Simultaneous observations of sea surface temperature in the western equatorial Pacific Ocean by bulk, radiative and satellite methods

    NASA Astrophysics Data System (ADS)

    Coppin, P. A.; Bradley, E. F.; Barton, I. J.; Godfrey, J. S.

    The increasing reliance on satellite observations for mapping and following changes in sea surface temperature (SST) has renewed interest in the measurement of the skin temperature of the ocean surface. In this experiment, skin surface temperature was measured with a narrow-band radiometer over a 13-day period in the western equatorial Pacific Ocean and compared with bulk sea temperatures and satellite-derived estimates. A cool skin was found to be a quasi-permanent feature in this region; its temperature averaged 0.3°C less than the bulk sea temperature. Conventional models for the cool skin were found to give a reasonable fit down to wind speeds of 1 m s-1. Satellite measurements showed some deviations from the true SST values, a result not unexpected, considering the substantial corrections required as a result of the high atmospheric water vapor content in these latitudes.

  3. Interaction Between Surface Heat Budgets, Sea Surface Temperature and Deep Convection in the Tropical Western Pacific

    NASA Technical Reports Server (NTRS)

    Chou, Shu-Hsien; Chou, Ming-Dah; Lin, Po-Hsiung; Starr, David OC. (Technical Monitor)

    2002-01-01

    The surface heat budgets, sea surface temperature (SST), clouds and winds in the tropical western Pacific are analyzed and compared for the periods April-June 1998 and 1999. The spring of 1998 is in the later phase of a strong El Nino, whereas the spring of 1999 is in a period of a La Nina. The surface shortwave (SW) and longwave (LW) radiative fluxes are retrieved from Japanese Geostationary Meteorological Satellite radiance measurements, while the surface turbulent fluxes (latent and sensible heat) are derived from SSM/I-Inferred surface air humidity and winds. The SST and sea-air temperature differences are taken from NCEP/NCAR reanalysis. Deep convection is inferred from the outgoing longwave radiation of NOAA's polar-orbiting satellites. The longitudinal shift in maximum SST, deep convection and winds during El Nino and La Nina have a large impact on the spatial distribution of surface heating. Changes in clouds between these two periods have a large impact on the monthly-mean radiative heating, exceeding 60 W m(exp -2) over large oceanic regions. Similarly, the differences in wind speeds and SST have a large impact on the latent cooling, exceeding 40 W m(exp -2) over large oceanic areas. However, the maximum impacts on radiative and latent heat fluxes occur in different regions. The regions of maximum impact on radiative fluxes coincide with the regions of maximum change in clouds, whereas regions of maximum impact on turbulent heat fluxes coincide with the regions of maximum change in trade winds. The time-evolution of SST in relation to that of surface heat fluxes and winds are investigated and compared between the two El Nino and La Nina periods. In regions where wind speeds (or wind stresses) are large, the change in SST agrees well with the change in the net surface heating, indicating a deep ocean mixed layer associated with strong trade winds. On the other hand, in regions where radiative fluxes are large, the change in SST does not agree well with the

  4. Methane in water columns and sediments of the north western Sea of Japan

    NASA Astrophysics Data System (ADS)

    Vereshchagina, Olga F.; Korovitskaya, Elena V.; Mishukova, Galina I.

    2013-02-01

    This paper presents the results of methane measurements in water and sediments, first performed along the north western continental slope and abyssal plain of the Sea of Japan. Methane concentrations in the study area were very low. However, some features of its distribution are revealed. The highest dissolved methane concentrations (10-14 nmol kg-1) are characteristic of the pycnocline layer at a depth of 30-50 m in the northern shallow stations. With increasing depth, the methane is reduced to minimum values (0.5-1.0 nmol kg-1). The greatest variability in methane concentrations was observed in the layers at 0-500 m, which can be explained by the hydrodynamic conditions of the environment on the slope. Methane plumes (1.7 and 1.3 nmol kg-1) on the northern section were recorded at the depth of 1250 and 1495 m, respectively. Plumes (1.2 nmol kg-1) are also observed on near bottom layers at the deepest (more than 3000 m) stations. CH4 concentration in bottom sediments is also low (from 1 nmol kg-1 at 7 cm level to 752 nmol kg-1 at the 53 cm level of the core sediment in the northern part). Reduced sediments in the southern part of the study region have maximal methane concentration for sediment (2549 nmol kg-1) at the horizon 44 cm bsf (below sea floor) with a smell of H2S. These results assume a close relation of CH4 with sediment properties. A few stations with maximum methane (86-101 nmol kg-1) in the surface sediment layer are at the foot of a steep slope. Herewith, the highest abundance of some pericarid species was observed at the points with the highest values of methane concentrations in the surface sediment layer. Weak methane seepage can cause anoxic marine waters. Methane emission from water to the atmosphere is low because its concentration is close to equilibrium in surface water. An improved formula for calculating the methane flux of water into the atmosphere, taking into account high wind speeds, is presented in the paper.

  5. Interactions between volcanism and tectonics in the western Aeolian sector, southern Tyrrhenian Sea

    NASA Astrophysics Data System (ADS)

    Bortoluzzi, Giovanni; Ligi, Marco; Romagnoli, Claudia; Cocchi, Luca; Casalbore, Daniele; Sgroi, Tiziana; Cuffaro, Marco; Tontini, Fabio Caratori; D'Oriano, Filippo; Ferrante, Valentina; Remia, Alessandro; Riminucci, Francesco

    2010-10-01

    New high-resolution bathymetric and magnetic data from the western Aeolian sector, southern Tyrrhenian Sea, provide insights into structural and volcanic development of the area, suggesting a strong interaction between volcanism and tectonics. The analysis of these data combined with relocated earthquake distribution, focal plane solutions and strain rate evaluation indicates that the dextral strike-slip Sisifo-Alicudi shear zone is a complex and wide area of active deformation, representing the superficial expression of the deep seated lithospheric tear fault separating the subduction slab below Sicily and Calabria. Most of the observed volcanic features are aligned along a NW-SE trend, such as the Filicudi island-Alicudi North Seamount and Eolo-Enarete alignments, and are dissected by hundred-metre-high scarps along conjugate NNE-SSW trending fault systems. The magnetic field pattern matches the main trends of volcanic features. Spectral analysis and Euler deconvolution of magnetic anomalies show the existence of both deep and shallow sources. High-amplitude, high-frequency anomalies due to shallow sources are dominant close to the volcanic edifices of Alicudi and Filicudi, while the main contribution on the surrounding Eolo, Enarete, Alicudi North and Filicudi North seamounts is given by low-amplitude anomalies and/or deeper magnetic sources. This is probably related to different ages of the volcanic rocks, although hydrothermal processes may have played an important role in blanketing magnetic anomalies, in particular at Enarete and Eolo seamounts. Relative chronology of the eruptive centres and the inferred deformation pattern outline the Quaternary evolution of the western Aeolian Arc: Sisifo, Alicudi North and Filicudi North seamounts might have developed in an early stage, following the Late Pliocene-Early Pleistocene SE-ward migration of arc-related volcanism due to the Ionian subduction hinge retreat; Eolo, Enarete and Filicudi represent later

  6. Forecasting database for the tsunami warning regional center for the western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Gailler, A.; Hebert, H.; Loevenbruck, A.; Hernandez, B.

    2010-12-01

    Improvements in the availability of sea-level observations and advances in numerical modeling techniques are increasing the potential for tsunami warnings to be based on numerical model forecasts. Numerical tsunami propagation and inundation models are well developed, but they present a challenge to run in real-time, partly due to computational limitations and also to a lack of detailed knowledge on the earthquake rupture parameters. Through the establishment of the tsunami warning regional center for NE Atlantic and western Mediterranean Sea, the CEA is especially in charge of providing rapidly a map with uncertainties showing zones in the main axis of energy at the Mediterranean scale. The strategy is based initially on a pre-computed tsunami scenarios database, as source parameters available a short time after an earthquake occurs are preliminary and may be somewhat inaccurate. Existing numerical models are good enough to provide a useful guidance for warning structures to be quickly disseminated. When an event will occur, an appropriate variety of offshore tsunami propagation scenarios by combining pre-computed propagation solutions (single or multi sources) may be recalled through an automatic interface. This approach would provide quick estimates of tsunami offshore propagation, and aid hazard assessment and evacuation decision-making. As numerical model accuracy is inherently limited by errors in bathymetry and topography, and as inundation maps calculation is more complex and expensive in term of computational time, only tsunami offshore propagation modeling will be included in the forecasting database using a single sparse bathymetric computation grid for the numerical modeling. Because of too much variability in the mechanism of tsunamigenic earthquakes, all possible magnitudes cannot be represented in the scenarios database. In principle, an infinite number of tsunami propagation scenarios can be constructed by linear combinations of a finite number of

  7. The evaluation of Pat-Pat related injuries in the western black sea region of Turkey

    PubMed Central

    2011-01-01

    Background Accidents caused by motorized vehicle in the agricultural sector are frequently observed. In Turkey; accidents arising from motorized vehicles, named Pat-Pat, which are used by farmers in the Western Black Sea region is not unusual. Methods One hundred five patients who were brought into the Emergency Department of Duzce University, Medical Faculty Hospital between September 2009 and August 2010 due to Pat-Pat related accidents were evaluated. Results The cases consisted of 73 (69.5%) males and 32 (30.5%) females, ranging from 2 to 73 years of age. In the 10-39 age group, a total of 63 (60.0%) cases were determined. The months when the greatest rate of cases applied to the hospital consisted of July, August, September and the season is summer. The cases were exposed to trauma in roads in 54 (51.4%), and 51 (48.6%) occurred in agricultural area without roads. Eighty seven (82.9%) cases were injured due to the overturning of vehicle. The patients were brought to the hospital using a private vehicle in 54 (51.4%) of the cases and in 51 (48.6%) cases, 112 ambulance system was used. The cases were determined to apply to the hospital most frequently between 6 pm-12 am. The injuries frequently consisted of head-neck and spine traumas, thorax traumas and upper extremity traumas. In 55 (52.4%) cases, open wound-laceration was determined. Seventy five (71.4%) cases were treated in the Emergency Department, and 28 (26.7%) were hospitalized. Three (2.9%) cases were deceased. Conclusions Serious injuries can occur in Pat-Pat related accidents, and careful systematic physical examination should be conducted. In order to prevent these accidents, education of farm operators and engineering studies on the mechanics and safety of these vehicles should be taken and legal regulations should be created. PMID:21699689

  8. Diversity, distribution and population size structure of deep Mediterranean gorgonian assemblages (Menorca Channel, Western Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Grinyó, Jordi; Gori, Andrea; Ambroso, Stefano; Purroy, Ariadna; Calatayud, Clara; Dominguez-Carrió, Carlos; Coppari, Martina; Lo Iacono, Claudio; López-González, Pablo J.; Gili, Josep-Maria

    2016-06-01

    Gorgonians are a key group of organisms in benthic marine communities with a wide bathymetric and geographical distribution. Although their presence on continental shelves and slopes has been known for more than 100 years, knowledge concerning the ecology of deep gorgonian species is still in a very preliminary stage. To overcome this situation, gorgonian assemblages located at 40-360 m depth were studied over a large geographical area on the continental shelf and upper slope of the Menorca Channel (Western Mediterranean Sea). A quantitative analysis of video transects recorded by a manned submersible and a remotely operated vehicle, were used to examine the diversity, distribution and demography of gorgonian species. Results showed high gorgonian diversity within this depth range (a total of nine species were observed) compared to Mediterranean coastal areas. Gorgonian assemblages on the continental shelf and upper slope were mostly monospecific (respectively 73% and 76% of occupied sampling units contained one single species), whereas shelf edge assemblages were highly multispecific (92% of occupied sampling units contained several species). This contrasts with the monospecificity of Mediterranean coastal gorgonian assemblages. Gorgonian populations on the continental shelf were mostly dominated by small colonies (88% of measured colonies) with few intermediate and large colonies (12% of measured colonies). In deeper areas small colonies were still dominant (60% of measured colonies), but intermediate and large colonies were much more abundant (40% of measured colonies). This suggests high recruitment rates on the continental shelf, but perturbations (trammel nets, long lines and strong storms) may limit the presence of intermediate and large colonies. Conversely, on the shelf edge and upper slope a more stable environment may allow colonies to reach larger dimensions. The identification and ecological characterization of these deep assemblages further extends

  9. Response of Tropical Cyclone Tracks to Sea Surface Temperature in the Western North Pacific

    NASA Astrophysics Data System (ADS)

    Inatsu, Masaru; Katsube, Kotaro

    2016-04-01

    A set of short-term experiments using a regional atmospheric model (RAM) were carried out to investigate the response of tropical cyclone (TC) tracks to sea surface temperature (SST) in the western North Pacific. For ten selected TC cases occurring during 2002-2007, a warm and a cold run are performed with 2 K and ‑2 K added to the SSTs uniformly over the model domain, respectively. The cases can be classified into three groups in terms of recurvature: recurved tracks in the warm and cold runs, a recurved track in the warm run and a non-recurved track in the cold run, and non-recurved tracks in both runs. Commonly the warm run produced northward movement of the TC faster than the cold run. The rapid northward migration can be mainly explained by the result that cyclonic circulation to the west of the TC is found in the steering flow in the warm run and it is not in the cold run. The beta effect is also activated under the warm SST environment. For the typical TC cases, a linear baroclinic model experiment is performed to examine how the cyclonic circulation is intensified in the warm run. The stationary linear response to diabatic heating obtained from the RAM experiment reveals that the intensified TC by the warm SST excites the cyclonic circulation in the lower troposphere to the west of the forcing position. The vorticity and thermodynamic equation analysis shows the detailed mechanism. The time scale of the linear response and the teleconnection are also discussed.

  10. Neogene Fault and Feeder Dike Patterns in the Western Ross Sea

    NASA Astrophysics Data System (ADS)

    Magee, W. R.; Wilson, T. J.

    2010-12-01

    In Antarctica, where much of the continent is covered by water and ice, geophysical data from the Antarctic submarine continental shelf is a fundamental part of reconstructing geological history. Multibeam sonar from the western Ross Sea has revealed elongate volcanic edifices and fields of elongate submarine hills on the seafloor. Origin of the submarine hills as carbonate mounds and drumlins have been proposed. The hills are up to ~8000m long and ~3500m wide, and rise 50-100m above the seafloor. Morphometric analysis of the hills shows they are elongate, with axial ratios ranging from 1.2:1 to 2:1, and some hills are linked to form elongate ridges. Seismic profiles show significant pull-ups directly below the hills, consistent with narrow, higher-density magmatic bodies; thus we favor an origin as volcanic seamounts above subsurface feeder dikes. If this volcanic hypothesis is correct, feeder dikes below the hills and elongate volcanic ridges may document magmatically-forced extension within the Terror Rift. The seamount field forms part of a regional en echelon array of volcanic ridges extending NNW from Beaufort Island toward Drygalski Ice Tongue. The ridges and elongate seamount cluster trend NNE, subparallel to mapped fault trends in this sector of the Terror Rift. This geometry is compatible with right-lateral transtension along this zone, as previously proposed for the Terror Rift as a whole. Volcanic islands and dredged volcanic ridges within the en echelon array are dated at ~7-4 Ma, implying Neogene deformation. We are completing a detailed analysis of orientation patterns and cross-cutting relations between faults and volcanic hills and their feeder systems to test this model for Neogene rift kinematics.

  11. Midwater food web in the vicinity of a marginal ice zone in the western Weddell Sea

    NASA Astrophysics Data System (ADS)

    Hopkins, Thomas L.; Torres, Joseph J.

    1989-04-01

    The structure of the food web in the vicinity of a marginal ice zone was investigated in the western Weddell Sea during austral autumn 1986. The diets of 40 species of zooplankton and micronekton occurring in the epipelagic zone were examined and compared using non-hierarchical clustering procedures. Over half the species were in three clusters of predominantly small-particle (phytoplankton; protozoans) grazers. These included biomass dominants Calanoides acutus, Calanus propinquus, Metridia gerlachei and Salpa thompsoni. Six clusters contained omnivores that had diets consisting of small particles as well as a substantial fraction of metazoan food. Among these was Euphausia superba. Seven groups were carnivorous, including species of copepods (1), chaetognaths (3), and fishes (5). Copepods were the most frequent food of carnivores; however krill also were important in the diets of three fish species. Among small-particle grazers, phytoplankton occurred more frequently in guts of individuals from open water; carnivory was more in evidence in samples collected under the pack ice. Regional comparisons of material taken on this and several previous cruises indicate that, in most of the dominant species, diets remain relatively consistent with respect to major food categories. Seasonal impact on feeding dynamics appears to be great: the guts of grazing species were generally much more full (visual evidence) during summer bloom conditions than during the autumn. The following trophic sequence is suggested for grazing zooplankton species in ice-covered regions of the Antarctic: (1) Active small-particle grazing during the summer bloom period; (2) reduced ingestion rates in autumn as primary production declines and the system becomes more oligotrophic, with some species augmenting grazing with carnivory; (3) descent of zooplankton biomass species into the mesopelagic zone in late autumn-early winter with feeding largely terminated. The sequence applies to the dominant

  12. Human impact on dynamics of western coast of Yamal, Kara sea

    NASA Astrophysics Data System (ADS)

    Kuznetsov, Dmitry; Noskov, Alexey; Belova, Nataliya; Kamalov, Anatoly; Arkhipov, Vasily; Ogorodov, Stanislav

    2010-05-01

    The western coast of Yamal around the site of Bovanenkovo-Ukhta gas pipeline landfall (Baydarata bay, Kara sea) consists of two types of shore, with specific kind of human impact for each of them. These are low and gentle accumulative shores, which in this case are most influenced since the landfall site is situated within this type, and high bluffy abrasion shores. The heaviness of impact depends on degree of anthropogenic activity influencing the topography (this degree relates to proximity to main construction sites and intensity of human activity), and natural relief features, mainly its resistance to anthropogenic destruction and ability to restore itself. Accumulative shores are more resistant to destruction; main morphogenetic processes are marine accumulation (mainly within tideland) and aeolian transport, especially in areas without vegetation (tideland, beach and often the onshore sand bar). In the meantime, most part of construction (dams, roads, buildings, infrastructural sites) is located within accumulative coast, since it's generally more stable and good for construction. Abrasion coast is more prone to destruction because of human activity, but is much less subject to human impact since no direct construction activity is held here, and main types of this impact are usually traffic of heavy motor transport and allocation of construction waste (often brought by the sea). There are the following types of direct human impact on topography at pipeline landfall construction sites: 1) construction of large artificial accumulative bodies (dams, banks, sand deposits), which leads to additional sediment inflow at the site; 2) creation of negative forms like pits and trenches while taking sand material for construction (leads to erosion and decrease in tideland and beach width, rebuilding of submerged bar system); 3) change of surface properties during construction and traffic, destruction or suppression of vegetation (leads to activation of erosion). The

  13. Investigation of the shelf break and continental slope in the Western part of the Black Sea using acoustic methods

    NASA Astrophysics Data System (ADS)

    Dutu, F.; Ion, G.; Jugaru Tiron, L.

    2009-04-01

    The Black Sea is a large marginal sea surrounded by a system of Alpine orogenic chains, including the Balkanides-Pontides, Caucasus, Crimea and North Dobrogea located to the south, northeast, north and northwest, respectively (Dinu et al., 2005). The north-western part of the Black Sea is the main depocentre for sediment supply from Central Europe via the Danube River, but also from Eastern Europe through the Ukrainian rivers Dniepr, Dniestr and Southern Bug (Popescu et al., 2004). The shelfbreak is located at water depths of 120-140 m southward of the Danube Canyon, and up to 170 m northward of the canyon possibly due to recent faulting which is very common in this area. The continental slope is dissected by numerous canyons, each of which is fed by several tributaries. The Danube Canyon (also known as Viteaz Canyon) is a large shelf-indenting canyon located in the north-western Black Sea and connected to the youngest channel-levee system of the Danube Fan (Popescu et al., 2004). The acoustic methods are a useful way for investigate the shelf break and the continental slope giving us information about landslides on the continental slope, the topography of the investigated area, the sedimentary zones affected by instability and to quantify the geometry of the underwater landslides. The measurements made on the continental slope from north-western part of the Black Sea gave us the possibility to make a digital terrain model. After processing the data the model offer information about the main access ways of the sediments through gravitational slide on the submarines canyons, with forming of turbidity currents, debris flows and also other transport/transformation phenomena of the sediments on the continental slope like submarine landslides and submarine collapse. References Dinu, C., Wong, H.K., Tambrea, D., Matenco, L., 2005. Stratigraphic and structural characteristics of the Romanian Black Sea shelf. Tectonophysics 410, 417-435. Popescu, I., Lericolais, G., Panin

  14. Sea surface temperature variability in the central-western Mediterranean Sea during the last 2700 years: a multi-proxy and multi-record approach

    NASA Astrophysics Data System (ADS)

    Cisneros, M.; Cacho, I.; Frigola, J.; Canals, M.; Masqué, P.; Martrat, B.; Lirer, F.; Margaritelli, G.

    2015-11-01

    This study analyses the evolution of sea surface conditions during the last 2700 years in the central-western Mediterranean Sea based on six records as measured on five short sediment cores from two sites north of Minorca (cores MINMC06 and HER-MC-MR3). Sea Surface Temperatures (SSTs) were obtained from alkenones and Globigerina bulloides-Mg/Ca ratios combined with δ18O measurements to reconstruct changes in the regional Evaporation-Precipitation (E-P) balance. We reviewed the G. bulloides Mg/Ca-SST calibration and re-adjusted it based on a set of core top measurements from the western Mediterranean Sea. According to the regional oceanographic data, the estimated Mg/Ca-SSTs are interpreted to reflect spring seasonal conditions mainly related to the April-May primary productivity bloom. In contrast, the Alkenone-SSTs signal likely integrates the averaged annual signal. A combination of chronological tools allowed synchronizing the records in a common age model. Subsequently a single anomaly stack record was constructed for each proxy, thus easing to identify the most significant and robust patterns. The warmest SSTs occurred during the Roman Period (RP), which was followed by a general cooling trend interrupted by several centennial-scale oscillations. This general cooling trend could be controlled by changes in the annual mean insolation. Whereas some particularly warm SST intervals took place during the Medieval Climate Anomaly (MCA) the Little Ice Age (LIA) was markedly unstable with some very cold SST events mostly during its second half. The records of the last centuries suggest that relatively low E-P ratios and cold SSTs dominated during negative North Atlantic Oscillation (NAO) phases, although SST records seem to present a close positive connection with the Atlantic Multidecadal Oscillation index (AMO).

  15. Sea surface temperature variability in the central-western Mediterranean Sea during the last 2700 years: a multi-proxy and multi-record approach

    NASA Astrophysics Data System (ADS)

    Cisneros, Mercè; Cacho, Isabel; Frigola, Jaime; Canals, Miquel; Masqué, Pere; Martrat, Belen; Casado, Marta; Grimalt, Joan O.; Pena, Leopoldo D.; Margaritelli, Giulia; Lirer, Fabrizio

    2016-04-01

    This study presents the reconstructed evolution of sea surface conditions in the central-western Mediterranean Sea during the late Holocene (2700 years) from a set of multi-proxy records as measured on five short sediment cores from two sites north of Minorca (cores MINMC06 and HER-MC-MR3). Sea surface temperatures (SSTs) from alkenones and Globigerina bulloides Mg / Ca ratios are combined with δ18O measurements in order to reconstruct changes in the regional evaporation-precipitation (E-P) balance. We also revisit the G. bulloides Mg / Ca-SST calibration and re-adjusted it based on a set of core-top measurements from the western Mediterranean Sea. Modern regional oceanographic data indicate that Globigerina bulloides Mg / Ca is mainly controlled by seasonal spring SST conditions, related to the April-May primary productivity bloom in the region. In contrast, the alkenone-SST signal represents an integration of the annual signal. The construction of a robust chronological framework in the region allows for the synchronization of the different core sites and the construction of "stacked" proxy records in order to identify the most significant climatic variability patterns. The warmest sustained period occurred during the Roman Period (RP), which was immediately followed by a general cooling trend interrupted by several centennial-scale oscillations. We propose that this general cooling trend could be controlled by changes in the annual mean insolation. Even though some particularly warm SST intervals took place during the Medieval Climate Anomaly (MCA), the Little Ice Age (LIA) was markedly unstable, with some very cold SST events mostly during its second half. Finally, proxy records for the last centuries suggest that relatively low E-P ratios and cold SSTs dominated during negative North Atlantic Oscillation (NAO) phases, although SSTs seem to present a positive connection with the Atlantic Multidecadal Oscillation (AMO) index.

  16. Mineral distributions in surface sediments of the western South Yellow Sea: implications for sediment provenance and transportation

    NASA Astrophysics Data System (ADS)

    Lu, Jian; Li, Anchun; Huang, Peng; Li, Yan

    2015-03-01

    The South Yellow Sea (SYS) is strongly influenced by the substantial sediment loads of the Huanghe (Yellow) (including the modern Huanghe and abandoned old Huanghe subaqueous delta) and Changjiang (Yangtze) Rivers. However, the dispersal patterns of these sediments, especially in the western SYS, have not been clearly illustrated. In this study, we have analyzed clay minerals, detrital minerals, and grain sizes for 245 surface sediment samples (0-5 cm) collected from the western SYS. The clay minerals, on average, consist of 67% illite, 14% smectite, 11% chlorite, and 8% kaolinite. Clay minerals, detrital minerals, and grain size analyses of surface sediments, combined with water mass hydrology analysis, reveal that sediments in the western SYS are mainly derived from the modern Huanghe River, the abandoned subaqueous delta of the old Huanghe River, some material from the Changjiang, and coastal erosion. The clay minerals (especially illite and smectite) and quartz/feldspar ratio distribution patterns, reveal that the influence of modern Huanghe sediments can reach 35°N in the northwestern part of the study area, an influence that can be enhanced especially in winter owing to northerly winds. Conversely, sediments along the Jiangsu coast are mixed, in summer, with material from the Changjiang arriving via northward flow of Changjiang Diluted Water. The Subei Coastal Current carries the refreshed sediments northward into the western SYS. Sediment distribution and transport in the western SYS are mainly controlled by the oceanic circulation system that is primarily related to the monsoon.

  17. Alongshore and cross-shore circulations and their response to winter monsoon in the western East China Sea

    NASA Astrophysics Data System (ADS)

    Huang, Daji; Zeng, Dingyong; Ni, Xiaobo; Zhang, Tao; Xuan, Jiliang; Zhou, Feng; Li, Jia; He, Shuangyan

    2016-02-01

    An array of four bottom-mounted acoustic Doppler current profilers (ADCPs) were deployed during the winter of 2008 (28 December 2008 to 12 March 2009) along a cross-shelf section in the western East China Sea to investigate the winter circulation and its response to wind. During the observation period, the observed subtidal currents exhibit coherent spatial structure and temporal variation in terms of their mean (seasonal), trend (intra-seasonal), and synoptic variability. The subtidal currents are polarized roughly in the alongshore direction parallel to local isobaths, and the weak cross-shore current is closely linked to the alongshore component. The temporal variation of the currents follows the rhythm of wind stress, sea level, and sea level difference at the synoptic scale. The mean currents are basically composed of two anti-parallel currents in the alongshore direction: the East China Sea coastal current (ECSCC) flows southwestward along the inner shelf and the Taiwan warm current (TWC) flows in the opposite direction along the outer-shelf. The strongest current occurs over the mid-shelf as a coastal jet. The intra-seasonal currents exhibit an expansion and intensification of the ECSCC along with shrinking and weakening the alongshore component of the TWC. There is a significant increase in onshore current particularly over the mid-shelf. The fluctuations of synoptic currents show a significant positive correlation with wind stress, and the fluctuations are negatively correlated with sea level and sea level difference. The coherent spatial structure of the currents indicates that the depth-independent column motion is related to the sea level difference through a barotropic pressure gradient. The vertical shear of currents is related to the density-related baroclinic pressure gradient in the whole water column and to the friction within the surface and bottom boundary layers.

  18. Broad-Scale Climate Influences on Spring-Spawning Herring (Clupea harengus, L.) Recruitment in the Western Baltic Sea

    PubMed Central

    Gröger, Joachim P.; Hinrichsen, Hans-Harald; Polte, Patrick

    2014-01-01

    Climate forcing in complex ecosystems can have profound implications for ecosystem sustainability and may thus challenge a precautionary ecosystem management. Climatic influences documented to affect various ecological functions on a global scale, may themselves be observed on quantitative or qualitative scales including regime shifts in complex marine ecosystems. This study investigates the potential climatic impact on the reproduction success of spring-spawning herring (Clupea harengus) in the Western Baltic Sea (WBSS herring). To test for climate effects on reproduction success, the regionally determined and scientifically well-documented spawning grounds of WBSS herring represent an ideal model system. Climate effects on herring reproduction were investigated using two global indices of atmospheric variability and sea surface temperature, represented by the North Atlantic Oscillation (NAO) and the Atlantic Multi-decadal Oscillation (AMO), respectively, and the Baltic Sea Index (BSI) which is a regional-scale atmospheric index for the Baltic Sea. Moreover, we combined a traditional approach with modern time series analysis based on a recruitment model connecting parental population components with reproduction success. Generalized transfer functions (ARIMAX models) allowed evaluating the dynamic nature of exogenous climate processes interacting with the endogenous recruitment process. Using different model selection criteria our results reveal that in contrast to NAO and AMO, the BSI shows a significant positive but delayed signal on the annual dynamics of herring recruitment. The westward influence of the Siberian high is considered strongly suppressing the influence of the NAO in this area leading to a higher explanatory power of the BSI reflecting the atmospheric pressure regime on a North-South transect between Oslo, Norway and Szczecin, Poland. We suggest incorporating climate-induced effects into stock and risk assessments and management strategies as part

  19. Multi-year study of the carbonate system in the Chukchi Sea with emphasizes on its western part

    NASA Astrophysics Data System (ADS)

    Semiletov, I. P.; Pipko, I.; Pugach, S.

    2015-12-01

    Variability of the Arctic climate has affected many aspects of the Arctic environment, especially in the Pacific sector of the Arctic. The primary implication is that today's Arctic cryosphere (glaciers, frozen ground, and sea ice) and biosphere (terrestrial, lacustrine, and marine) are not at steady state; they have changed and will continue to change in response to evolving Arctic climate. Over the decade 2004-2013 environmental changes in the Pacific sector of the Arctic have been dramatic enough to suggest that a 'new normal' climate is emerging (Wood et al., 2015). Like everywhere in the Arctic, understanding of environmental change in the Chukchi Sea is hindered by sparse data. Dynamics of the carbonate system (CS) in the eastern Chukchi Sea (US EEZ) has been studied more extensively for a longer period and is better understood than in its western (Russian EEZ) part. Here we focus on the carbonate system data collected in the Russian part of the Chukchi Sea over > 10 years (2000-2011). Our data exhibit a strong mesoscale and interannual dynamics of carbonate system parameters in the surface seawater. The aragonite saturation state (WAr) was highly variable but also has generally been decreasing in the upper waters from 2000 to 2011. It was shown that despite strong sea ice loss, waters heating and storm increasing, the surface waters in this area have been consistently undersaturated by CO2 with respect to the atmosphere. Notable localized exceptions, where CO2 outgassing occurs, include the well-mixed waters near Bering Strait. Combining our long-term carbonate system data set (1996-2011) with the available literature data we felt in conclusion that the entire Chukchi Sea during ice-free season absorbs ~12-15× 1012 g C and a significant part of this carbon was transferred to the deep layers and insulated from contact with the atmosphere for a long time. Note that the CO2 invasion is a similar value with the CO2 outgassing from the shallow eastern Laptev Sea

  20. Age-structured modeling reveals long-term declines in the natality of western Steller sea lions.

    PubMed

    Holmes, E E; Fritz, L W; York, A E; Sweeney, K

    2007-12-01

    Since the mid-1970s, the western Steller sea lion (Eumetopias jubatus), inhabiting Alaskan waters from Prince William Sound west through the Aleutian Islands, has declined by over 80%. Changing oceanographic conditions, competition from fishing operations, direct human-related mortality, and predators have been suggested as factors driving the decline, but the indirect and interactive nature of their effects on sea lions have made it difficult to attribute changes in abundance to specific factors. In part, this is because only changes in abundance, not changes in vital rates, are known. To determine how vital rates of the western Steller sea lion have changed during its 28-year decline, we first estimated the changes in Steller sea lion age structure using measurements of animals in aerial photographs taken during population surveys since 1985 in the central Gulf of Alaska (CGOA). We then fit an age-structured model with temporally varying vital rates to the age-structure data and to total population and pup counts. The model fits indicate that birth rate in the CGOA steadily declined from 1976 to 2004. Over the same period, survivorship first dropped severely in the early 1980s, when the population collapsed, and then survivorship steadily recovered. The best-fitting model indicates that in 2004, the birth rate in the central Gulf of Alaska was 36% lower than in the 1970s, while adult and juvenile survivorship were close to or slightly above 1970s levels. These predictions and other model predictions concerning population structure match independent field data from mark-recapture studies and photometric analyses. The dominant eigenvalue for the estimated 2004 Leslie matrix is 1.0014, indicating a stable population. The stability, however, depends on very high adult survival, and the shift in vital rates results in a population that is more sensitive to changes in adult survivorship. Although our modeling analysis focused exclusively on the central Gulf of Alaska

  1. Hydrographic controls on marine organic matter fate and microbial diversity in the western Irish Sea

    NASA Astrophysics Data System (ADS)

    O'Reilly, Shane; Szpak, Michal; Monteys, Xavier; Flanagan, Paul; Allen, Christopher; Kelleher, Brian

    2014-05-01

    Cycling of organic matter (OM) is the key biological process in the marine environment1 and knowledge of the sources and the reactivity of OM, in addition to factors controlling its distribution in estuarine, coastal and shelf sediments are of key importance for understanding global biogeochemical cycles2. With recent advances in cultivation-independent molecular approaches to microbial ecology, the key role of prokaryotes in global biogeochemical cycling in marine ecosystems has been emphasised3,4. However, spatial studies combining the distribution and fate of OM with microbial community abundance and diversity remain rare. Here, a combined spatial lipid biomarker and 16S rRNA tagged pyrosequencing study was conducted in surface sediments and particulate matter across hydrographically distinct zones associated with the seasonal western Irish Sea gyre. The aim was to assess the spatial variation of, and factors controlling, marine organic cycling and sedimentary microbial communities across these distinct zones. The distribution of phospholipid fatty acids, source-specific sterols, wax esters and C25 highly branched isoprenoids indicate that diatoms, dinoflagellates and green algae were the major contributors of marine organic matter, while the distribution of cholesterol, wax esters and C20 and C22 polyunsaturated fatty acids have highlighted the importance of copepod grazing for mineralizing organic matter in the water column5. This marine OM production and mineralisation was greatest in well-mixed waters compared to offshore stratified waters. Lipid analysis and 16S rRNA PCR-DGGE profiling also suggests that sedimentary bacterial abundance increases while community diversity decreases in offshore stratified waters. The major bacterial classes are the Deltaproteobacteria, Clostridia, Flavobacteriia, Gammaproteobactera and Bacteroiidia. At the family/genus level most groups appear to be associated with organoheterotrophic processing of sedimentary OM, ranging

  2. Climatic changes in hydrological and biological characteristics of the North-Western Black Sea region

    NASA Astrophysics Data System (ADS)

    Kovalyshyna, S.; Ivanov, S.; Matygin, A.

    2009-04-01

    The last decades have shown considerable climatic changes in all components of the Earth System. In particular, a hydrological regime of river runoffs in the North-Western Black Sea (NWBS) shows changes on seasonal and interannual scales. A general reduction in annual runoff occurs, while winter flow increases and spring flow decreases. This can be explained by the fact that the snow cover becomes less important with regional warming. Changes in the hydrological regime affect the vertical thermohaline structure and circulation in the NWBS. Observations in coastal waters show that both the temperature and salinity changed remarkably for the winter, while there are no significant variations for the summer season. Moreover, for the winter season, temperature has increased by about 2C within the upper layer of 0-10 m and more than 3C in the benthonic layer. Changes of salinity in the upper and benthonic layers are of opposite signs leading to weakening of the vertical water exchange between two layers. The changes in hydrological environment lead to consequent changes of diversity and population of hydrobiota. Biological components are less sensitive to the interannual changes and work like a natural filter smoothing this temporal scale and emphasizing longer fluctuations. Due to the warming, the spring peak of phytoplankton has moved from May to late March - early April and its population during the last decade considerably increased. The major contribution of this growth is associated with the green and blue-green seaweed microalgae, coming into the NWBS with river runoff. The increasing amount of microalgae while decreasing the biomass means the degradation of macrocells species of microalgae. The peaks of population and biomass of zooplankton follow in 2-4 weeks after microalgae, which is the forage reserve. Diversity and amount of zooplankton have been degradated in the past decades. The spring peak associated with the zooplankton has especially decreased

  3. A new Holocene relative sea-level curve for western Brittany (France): Insights on isostatic dynamics along the Atlantic coasts of north-western Europe

    NASA Astrophysics Data System (ADS)

    Goslin, Jérôme; Van Vliet Lanoë, Brigitte; Spada, Giorgio; Bradley, Sarah; Tarasov, Lev; Neill, Simon; Suanez, Serge

    2015-12-01

    This study presents new Relative Sea Level (RSL) data that were obtained in the Finistère region (Western tip of Brittany, France) and the implications those data have for the understanding of the isostatic dynamics across north-western Europe, and more specifically along the Atlantic and Channel coasts. New stratigraphic sequences were obtained and analyzed to derive 24 new Sea-level Index Points, in which 6 are basal. These new data considerably increase the knowledge we have of the RSL evolution along the coasts of Western Brittany since the last 8 kyr B.P. From this new dataset, RSL was estimated to rise continuously over the last 8 kyr with a major inflection at ca. 6 kyr cal. BP. Our results show large vertical discrepancies between the RSL records of Brittany and South-Western UK, with the latter plotting several meters below the new data. From this comparison we suggest that the two regions underwent a very different pattern and/or amplitude of subsidence during the last 8 kyr which has implications for the spatial and temporal pattern of the peripheral bulge of the European ice sheets. We compared our data against predictions from Glacio-Isostatic Adjustment models (GIA models). There are large misfits between RSL observations and the predictions of the global (ICE-5G (VM2a) - Peltier, 2004, GLAC1-b - Tarasov and Peltier, 2002; Tarasov et al., 2012, Briggs et al., 2014) and regional UK models ("BIIS" - Bradley et al., 2009; Bradley et al., 2011; "Kuchar"- Kuchar et al., 2012), which can't be resolved through significant changes to the deglaciation history and size of the British-Irish Ice sheet. Paleo-tidal modelling corrections indicate regional changes in the tidal ranges played a negligible role in the data-model misfits. Hence, we propose that the misfits are due to some combination of: (i) unaccounted mass-loss of far-field ice-sheets (Antarctic ice-Sheet or Laurentide Ice-Sheet), (ii) unresolved differences in the deglaciation history and size of

  4. Affects of Changes in Sea Ice Cover on Bowhead Whales and Subsistence Whaling in the Western Arctic

    NASA Astrophysics Data System (ADS)

    Moore, S.; Suydam, R.; Overland, J.; Laidre, K.; George, J.; Demaster, D.

    2004-12-01

    Global warming may disproportionately affect Arctic marine mammals and disrupt traditional subsistence hunting activities. Based upon analyses of a 24-year time series (1979-2002) of satellite-derived sea ice cover, we identified significant positive trends in the amount of open-water in three large and five small-scale regions in the western Arctic, including habitats where bowhead whales (Balaena mysticetus) feed or are suspected to feed. Bowheads are the only mysticete whale endemic to the Arctic and a cultural keystone species for Native peoples from northwestern Alaska and Chukotka, Russia. While copepods (Calanus spp.) are a mainstay of the bowhead diet, prey sampling conducted in the offshore region of northern Chukotka and stomach contents from whales harvested offshore of the northern Alaskan coast indicate that euphausiids (Thysanoessa spp.) advected from the Bering Sea are also common prey in autumn. Early departure of sea ice has been posited to control availability of zooplankton in the southeastern Bering Sea and in the Cape Bathurst polynya in the southeastern Canadian Beaufort Sea, with maximum secondary production associated with a late phytoplankton bloom in insolatoin-stratified open water. While it is unclear if declining sea-ice has directly affected production or advection of bowhead prey, an extension of the open-water season increases opportunities for Native subsistence whaling in autumn. Therefore, bowhead whales may provide a nexus for simultaneous exploration of the effects sea ice reduction on pagophillic marine mammals and on the social systems of the subsistence hunting community in the western Arctic. The NOAA/Alaska Fisheries Science Center and NSB/Department of Wildlife Management will investigate bowhead whale stock identity, seasonal distribution and subsistence use patterns during the International Polar Year, as an extension of research planned for 2005-06. This research is in response to recommendations from the Scientific

  5. Crustal structure and evolution of the Mawson Sea, western Wilkes Land margin, East Antarctica

    USGS Publications Warehouse

    Leitchenkov, G.L.; Gandyukhin, V.V.; Guseva, Yu. B.; Kazankov, A. Yu

    2007-01-01

    3 to 11 mm/yr. Three major unconformities are identified in the sedimentary cover of the Mawson Sea and are interpreted to be caused by break-up between Australia and Antarctica at about 81 Ma ago (WL1), the first arrival of the ice sheet to the Mawson Sea (WL3) and continental scale glaciation at about 34 Ma ago (WL4).

  6. Effects of earlier sea ice breakup on survival and population size of polar bears in western Hudson Bay

    USGS Publications Warehouse

    Regehr, E.V.; Lunn, N.J.; Amstrup, Steven C.; Stirling, I.

    2007-01-01

    Some of the most pronounced ecological responses to climatic warming are expected to occur in polar marine regions, where temperature increases have been the greatest and sea ice provides a sensitive mechanism by which climatic conditions affect sympagic (i.e., with ice) species. Population-level effects of climatic change, however, remain difficult to quantify. We used a flexible extension of Cormack-Jolly-Seber capture-recapture models to estimate population size and survival for polar bears (Ursus maritimus), one of the most ice-dependent of Arctic marine mammals. We analyzed data for polar bears captured from 1984 to 2004 along the western coast of Hudson Bay and in the community of Churchill, Manitoba, Canada. The Western Hudson Bay polar bear population declined from 1,194 (95% CI = 1,020-1,368) in 1987 to 935 (95% CI = 794-1,076) in 2004. Total apparent survival of prime-adult polar bears (5-19 yr) was stable for females (0.93; 95% CI = 0.91-0.94) and males (0.90; 95% CI = 0.88-0.91). Survival of juvenile, subadult, and senescent-adult polar bears was correlated with spring sea ice breakup date, which was variable among years and occurred approximately 3 weeks earlier in 2004 than in 1984. We propose that this correlation provides evidence for a causal association between earlier sea ice breakup (due to climatic warming) and decreased polar bear survival. It may also explain why Churchill, like other communities along the western coast of Hudson Bay, has experienced an increase in human-polar bear interactions in recent years. Earlier sea ice breakup may have resulted in a larger number of nutritionally stressed polar bears, which are encroaching on human habitations in search of supplemental food. Because western Hudson Bay is near the southern limit of the species' range, our findings may foreshadow the demographic responses and management challenges that more northerly polar bear populations will experience if climatic warming in the Arctic continues as

  7. A large channel system in the western the Riiser Larsen Sea, East Antarctica: Paleoceanographic and sedimentary aspects

    NASA Astrophysics Data System (ADS)

    Hass, H. Christian; Klages, Johann P.; Kuhn, Gerhard; Forwick, Matthias

    2016-04-01

    We investigated seafloor morphology and sedimentary processes at the continental margin in the western Riiser Larsen Sea, Antarctica, to reconstruct processes of channel/levee development, and to evaluate the influence of climate through the past 5 marine isotope stages on these processes. Shallow seismic (parametric subbottom profiler) investigations reveal that channels and associated levees form the principal morphological structures in the western Riiser Larsen Sea. The channels are up to several kilometers wide and hundreds of meters deep. They stretch from the upper continental slope towards the Enderby Abyssal Plain. Sediment cores (taken from levee tops) reveal increased amounts of sand and coarser silt during warmer climate phases (MIS 1, 3, 5). The sand is mainly composed of planktic foraminifers and IRD, both suggesting seasonally open waters (interglacials). The carbonate-free sortable silt mean grain size suggests increased bottom current speed during the warmer climate phases. We postulate, that the occurrence of coastal polynyas and strong sea-ice formation through katabatic winds promote the formation of cold waters and brines. These are channeled on the continental slope and intensify turbidity currents that occur on the steep slopes. Alternatively, the newly formed dense waters can be taken up by westward flowing contour currents and thus support the formation of turbidity currents. It is suggested that either process supports downslope sediment transport and levee growth during warm climate phases. Under cold climates a permanent ice cover is suggested at least for the positions of the sediment cores (seasonally open waters today). These reveal significantly IRD and carbonate-depleted sediments during the cold climate phases. Hence, polynyas may have formed further to the north over deeper waters. The volume of the cooled-down waters and brines was likely smaller and probably not able to reach the sea floor due to mixing with upwelling warmer

  8. Temporal variation of genetic composition in Atlantic salmon populations from the Western White Sea Basin: influence of anthropogenic factors?

    PubMed Central

    2013-01-01

    Background Studies of the temporal patterns of population genetic structure assist in evaluating the consequences of demographic and environmental changes on population stability and persistence. In this study, we evaluated the level of temporal genetic variation in 16 anadromous and 2 freshwater salmon populations from the Western White Sea Basin (Russia) using samples collected between 1995 and 2008. To assess whether the genetic stability was affected by human activity, we also evaluated the effect of fishing pressure on the temporal genetic variation in this region. Results We found that the genetic structure of salmon populations in this region was relatively stable over a period of 1.5 to 2.5 generations. However, the level of temporal variation varied among geographical regions: anadromous salmon of the Kola Peninsula exhibited a higher stability compared to that of the anadromous and freshwater salmon from the Karelian White Sea coast. This discrepancy was most likely attributed to the higher census, and therefore effective, population sizes of the populations inhabiting the rivers of the Kola Peninsula compared to salmon of the Karelian White Sea coast. Importantly, changes in the genetic diversity observed in a few anadromous populations were best explained by the increased level of fishing pressure in these populations rather than environmental variation or the negative effects of hatchery escapees. The observed population genetic patterns of isolation by distance remained consistent among earlier and more recent samples, which support the stability of the genetic structure over the period studied. Conclusions Given the increasing level of fishing pressure in the Western White Sea Basin and the higher level of temporal variation in populations exhibiting small census and effective population sizes, further genetic monitoring in this region is recommended, particularly on populations from the Karelian rivers. PMID:24053319

  9. Wave-planation surfaces in the mid-western East Sea (Sea of Japan): indicators of subsidence history and paleogeographic evolution of back-arc basin

    NASA Astrophysics Data System (ADS)

    Yoon, S.; Kim, G. B.; Sohn, Y. K.; Kwon, Y.

    2013-12-01

    In this study, we focus on the deep-submerged wave-planation surfaces identified in the multi-channel seismic reflection data acquired from the mid-western East Sea (Sea of Japan). By delineating seismic characters and geomorphic features of wave-planation surfaces, genetic models, including relevant volcano-tectonic activities and interaction between marine and subsiding ground masses, are established. Furthermore, local variability of back-arc subsidence history and paleogeographic evolution of the mid-western East Sea are revisited with broader implications of tectonic, volcanic, and sedimentological processes. The approaching method and results are applicable to the other deep-submerged oceanic basins. In seismic reflection profiles, the wave-planation surfaces are recognized as continuous high-amplitude single reflectors outlining the flattened tops of deeply submerged continental margin terraces and isolated topographic highs. In accordance with local geotectonic or volcanic settings, four genetic types of wave-planation surfaces are classified in continental margin terraces (type-1), rifted continental fragments (type-2), volcanic edifices (type-3), and uplifted sedimentary successions (type-4). The maximum depths of the planation surfaces are highly varied (150-1,650 m bsl) depending on age and locality, which gives an insight into local-scale subsidence history of extended back-arc basin. Based on the information about local subsidence histories, five episodes of paleogeographic evolution can be restored with specific emphases on major changes in geotectonic and volcanic settings during Neogene-Quaternary back-arc evolution: (1) incipient continental rifting and onset of marine incursion (23-18 Ma); (2) progressive continental rifting and onset of wave planation (18-11 Ma); (3) final eruption of post-rift volcanic edifices (11 Ma); (4) uplifting of shelf-margin bank and onset of the Pliocene-Holocene volcanic activities (11-2.5 Ma); (5) change in locus of

  10. P and S Waves Traversing Beneath Western Japan and the Shape of the Subducting Philippine Sea Plate

    NASA Astrophysics Data System (ADS)

    Kuge, K.; Fukuda, T.

    2011-12-01

    We show the characteristics of P and S waves traversing beneath western Japan, which can provide constraints on the shape of the subducting Philippine Sea plate. The subduction of the Philippine Sea plate causes megathrust earthquakes along the Nankai trough in western Japan. The complicated shape of the subducting plate can affect the spatial variation of the plate coupling as well as the recurrence of great interplate earthquakes. For slab earthquakes at depths of about 45 km in northwestern Shikoku, we observe two arrivals of P wave at the NIED Hi-net stations in the azimuth range from the north to the east. The apparent velocities are about 8 and 6.7 km/s, corresponding to P velocities in the mantle and crust, respectively. Dominant S waves propagate by apparent velocity of about 3.8 km/s, being S velocity in the crust. These observations are in agreement with those of Oda et al. (1990) and Ohkura (2000) using a smaller number of local stations. The P and S waves propagating at the slow apparent velocities can be modeled by horizontally layered structure if the earthquakes are located within a low-velocity layer spanning the stations. The thick low-velocity layer can be a stack of the continental crust of the Eurasian plate and the oceanic crust of the Philippine Sea plate subducting nearly subhorizontally (Oda et al., 1990; Ohkura, 2000). The P and S waves with the slow apparent velocities are observable at distances up to about 300 km. On the other hand, they are not observed or observable only at small distances in the western side of the epicenters. The spatial characteristics can be used to constrain the geometry of the low-velocity layer associated with the shape of the oceanic crust of the Philippine Sea plate. We observe two arrivals of P wave in the eastern side of the Kii Peninsula for slab earthquakes beneath Shikoku. Both apparent velocities are in a range of P velocity in the mantle. There appear two ray paths of P wave propagating in the mantle

  11. Acidification of the Mediterranean Sea from anthropogenic carbon penetration

    NASA Astrophysics Data System (ADS)

    Hassoun, Abed El Rahman; Gemayel, Elissar; Krasakopoulou, Evangelia; Goyet, Catherine; Abboud-Abi Saab, Marie; Guglielmi, Véronique; Touratier, Franck; Falco, Cédric

    2015-08-01

    This study presents an estimation of the anthropogenic CO2 (CANT) concentrations and acidification (ΔpH=pH2013-pHpre-industrial) in the Mediterranean Sea, based upon hydrographic and carbonate chemistry data collected during the May 2013 MedSeA cruise. The concentrations of CANT were calculated using the composite tracer TrOCA. The CANT distribution shows that the most invaded waters (>60 μmol kg-1) are those of the intermediate and deep layers in the Alboran, Liguro- and Algero-Provencal Sub-basins in the Western basin, and in the Adriatic Sub-basin in the Eastern basin. Whereas the areas containing the lowest CANT concentrations are the deep layers of the Eastern basin, especially those of the Ionian Sub-basin, and those of the northern Tyrrhenian Sub-basin in the Western basin. The acidification level in the Mediterranean Sea reflects the excessive increase of atmospheric CO2 and therefore the invasion of the sea by CANT. This acidification varies between -0.055 and -0.156 pH unit and it indicates that all Mediterranean Sea waters are already acidified, especially those of the Western basin where ΔpH is rarely less than -0.1 pH unit. Both CANT concentrations and acidification levels are closely linked to the presence and history of the different water masses in the intermediate and deep layers of the Mediterranean basins. Despite the high acidification levels, both Mediterranean basins are still highly supersaturated in calcium carbonate minerals.

  12. Input of Terrestrial Palynomorphs since the Last Deglaciation from Sediments of the Chukchi Sea Shelf, Western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Delusina, I.; Kim, S. Y.; Nam, S. I.; Woo, K. S.

    2014-12-01

    We report the palynology of marine sediment core ARA02B/01A-GC from the Western margin of the shallow shelf of the Chukchi Sea in the Arctic, a site which was synchronously influenced by climatic changes during the last deglaciation with those in the Bering Strait. The core contains a rich concentration of continental palynomorphs, even though the coring location is quite a distance from land. The catchment area for the observed palynomorphs includes the territories of both North America (Alaska and North Canada) and Northern Siberia (Chukotka peninsula and Northern East-Siberian coast). Based on this fact, we can reconstruct a common paleoenvironmental history for this location and the Bering Strait during the postglacial interval. We hypothesize that palynomorphs were carried to the sea during low sea-ice coverage intervals by large rivers (Yukon, Mackenzie and Siberian rivers) and were then transferred by oceanic currents. During intervals of extensive sea-ice coverage the source of the palynomorphs was predominantly eroded shelf sediments. The percentage ratio of tree-herb pollen and spores in the palynomorph assemblages shows that favorable conditions for an increase in forest vegetation took place between ~8 and 4 kyr BP, which coincides with maximum freshwater input to the sea. During a climatic optimum at ~5 kyr BP, as inferred from the total dominance of tree and herb pollen, the Chukchi Sea was apparently warmer than today. This represents the maximum ice-free period for the sea. The low sea-ice interval ended ~3 kyr BP, as suggested by a sharp drop in tree pollen, a reduction in fresh water input, and a drop in the concentration of the algae Pediastrum. Our data correlate well with data from marine core HLY0501-5 from the Bering Strait (Polyak et al., 2009) for the interval of 10-8 kyr BP, but shows a divergence since ~4 kyr BP, which may correspond to the beginning of the differentiation of North American and East-Siberian ecosystem zones.

  13. THE EXTENT OF SEA FLOOR VOLCANISM AND NATURE OF PRIMITIVE MAGMAS IN THE WESTERN ALEUTIANS

    NASA Astrophysics Data System (ADS)

    Yogodzinski, G. M.; Turka, J.; Portnyagin, M.; Kelemen, P. B.; Vervoort, J. D.; Sims, K. W.; Bindeman, I. N.

    2009-12-01

    Results of the 2005 Western Aleutian Volcano Expedition (WAVE) and the June 2009 cruise of the German-Russian KALMAR project (Kamchatka-Aleutian Margin) include the discovery of seafloor volcanism at the Ingenstrem Depression and at unnamed seamounts located 300 km west of Buldir Island, the westernmost emergent volcano in the Aleutians. The newly discovered features fall on a volcanic line connecting Buldir and other emergent volcanoes to Piip Seamount, which is located in the far west. These discoveries suggest that the surface expression of Aleutian volcanism slips below sea level at 175°E, but is otherwise continuous from 170°W to 167°E. Geochemical results from the Ingenstrem Depression (60 km west of Buldir) define two compositional groups, which provide insight into the nature of primitive Aleutian magmatism. Low-Sr lavas (<700 ppm Sr) are basalts and andesites with moderately enriched trace element patterns (La/Yb 4-8, Sr/Y<30) and relatively radiogenic Sr (87/86=0.7031-0.7033), typical of IAB. High-Sr lavas (>700 ppm) are plagioclase and hornblende-phyric andesites and dacites with fractionated trace element patterns (Sr/Y>50) and low Y (<12 ppm) and HREE. Sr isotopes for all lavas are inversely correlated with Sr/Y and SiO2, so the most felsic samples (65-67% SiO2), which have the highest Sr abundances and most fractionated trace element patterns (Sr/Y>120) are also the most isotopically depleted (87/86<0.7028). Major and trace elements are well correlated with isotopes defining primitive end-members at 87/86<0.7027 (high-Sr), and >0.7032 (low Sr). The narrow range for Nd isotopes (8.5-9.5 epsNd) suggests that the main source of Sr and Nd may be seawater-altered subducted oceanic crust; however, oxygen isotopes on olivine and hornblende separates are similar to MORB for both groups (delta18O=5.1-5.6 per-mil, olivine-equ). Available data do not identify a high-Sr lava with whole-rock Mg# and olivine phenocryst compositions appropriate for equilibration

  14. Active rollback in the Gibraltar Arc: Evidences from CGPS data in the western Betic Cordillera

    NASA Astrophysics Data System (ADS)

    Gonzalez-Castillo, L.; Galindo-Zaldivar, J.; de Lacy, M. C.; Borque, M. J.; Martinez-Moreno, F. J.; García-Armenteros, J. A.; Gil, A. J.

    2015-11-01

    The Gibraltar Arc, located in the western Mediterranean Sea, is an arcuate Alpine orogen formed by the Betic and Rif Cordilleras, separated by the Alboran Sea. New continuous GPS data (2008-2013) obtained in the Topo-Iberia stations of the western Betic Cordillera allow us to improve the present-day deformation pattern related to active tectonics in this collision area between the Eurasian and African plates. These data indicate a very consistent westward motion of the Betic Cordillera with respect to the relatively stable Iberian Massif foreland. The displacement in the Betics increases toward the south and west, reaching maximum values in the Gibraltar Strait area (4.27 mm/yr in Ceuta, CEU1, and 4.06 mm/yr in San Fernando, SFER), then progressively decreasing toward the northwestern mountain front. The recent geological structures and seismicity evidence moderate deformation in a roughly NW-SE to WNW-ESE compressional stress setting in the mountain frontal areas, and moderate extension toward the internal part of the cordillera. The mountain front undergoes progressive development of folds affecting at least up to Pliocene deposits, with similar recent geological and geodetical rates. This folded strip helps to accommodate the active deformation with scarce associated seismicity. The displacement pattern is in agreement with the present-day clockwise rotation of the tectonic units in the northern branch of the Gibraltar Arc. Our data support that the westward emplacement of the Betic Cordillera continues to be active in a rollback tectonic scenario.

  15. ENSURF: multi-model sea level forecast - implementation and validation results for the IBIROOS and Western Mediterranean regions

    NASA Astrophysics Data System (ADS)

    Pérez, B.; Brower, R.; Beckers, J.; Paradis, D.; Balseiro, C.; Lyons, K.; Cure, M.; Sotillo, M. G.; Hacket, B.; Verlaan, M.; Alvarez Fanjul, E.

    2011-04-01

    ENSURF (Ensemble SURge Forecast) is a multi-model application for sea level forecast that makes use of existing storm surge or circulation models today operational in Europe, as well as near-real time tide gauge data in the region, with the following main goals: - providing an easy access to existing forecasts, as well as to its performance and model validation, by means of an adequate visualization tool - generation of better forecasts of sea level, including confidence intervals, by means of the Bayesian Model Average Technique (BMA) The system was developed and implemented within ECOOP (C.No. 036355) European Project for the NOOS and the IBIROOS regions, based on MATROOS visualization tool developed by Deltares. Both systems are today operational at Deltares and Puertos del Estado respectively. The Bayesian Modelling Average technique generates an overall forecast probability density function (PDF) by making a weighted average of the individual forecasts PDF's; the weights represent the probability that a model will give the correct forecast PDF and are determined and updated operationally based on the performance of the models during a recent training period. This implies the technique needs the availability of sea level data from tide gauges in near-real time. Results of validation of the different models and BMA implementation for the main harbours will be presented for the IBIROOS and Western Mediterranean regions, where this kind of activity is performed for the first time. The work has proved to be useful to detect problems in some of the circulation models not previously well calibrated with sea level data, to identify the differences on baroclinic and barotropic models for sea level applications and to confirm the general improvement of the BMA forecasts.

  16. Abundance and diversity of sedimentary bacterial communities in a coastal productive setting in the Western Irish Sea

    NASA Astrophysics Data System (ADS)

    O'Reilly, S. S.; Pentlavalli, P.; Flanagan, P. V.; Allen, C. C. R.; Monteys, X.; Szpak, M. T.; Murphy, B. T.; Jordan, S. F.; Kelleher, B. P.

    2016-02-01

    The bacterial community composition and biomass abundance from a depositional mud belt in the western Irish Sea and regional sands were investigated by phospholipid ester-linked fatty acid profiling, denaturing gradient gel electrophoresis and barcoded pyrosequencing of 16S rRNA genes. The study area varied by water depth (12-111 m), organic carbon content (0.09-1.57% TOC), grain size, hydrographic regime (well-mixed vs. stratified), and water column phytodetrital input (represented by algal polyunsaturated PLFA). The relative abundance of bacterial-derived PLFA (sum of methyl-branched, cyclopropyl and odd-carbon number PLFA) was positively correlated with fine-grained sediment, and was highest in the depositional mud belt. A strong association between bacterial biomass and eukaryote primary production was suggested based on observed positive correlations with total nitrogen and algal polyunsaturated fatty acids. In addition, 16S rRNA genes affiliated to the classes Clostridia and Flavobacteria represented a major proportion of total 16S rRNA gene sequences. This suggests that benthic bacterial communities are also important degraders of phytodetrital organic matter and closely coupled to water column productivity in the western Irish Sea.

  17. Evidence of low density sub-crustal underplating beneath western continental region of India and adjacent Arabian Sea: Geodynamical considerations

    NASA Astrophysics Data System (ADS)

    Pandey, O. P.; Agrawal, P. K.; Negi, J. G.

    1996-07-01

    The known high mobility of the Indian subcontinent during the period from 80 to 53 Ma has evoked considerable interest in recent times. It appears to have played an important role in shaping the subcontinental structures of western India and the adjoining Arabian Sea. During this period, a major catastrophic event took place in the form of Deccan volcanism, which coincides with the biological mass extinction at the K-T boundary, including the death of dinosaurs. The origin of Deccan volcanism is still being debated. Geophysically, western India and its offshore regions exhibit numerous prominent anomalies which testify to the abnormal nature of the underlying crust-lithosphere. In this work, we develop a two-dimensional structural model of these areas along two long profiles extending from the eastern basin of the Arabian Sea to about 1000 km inland. The model, derived from the available gravity data in the oceanic and continental regions, is constrained by seismic and other relevant information in the area, and suggests, for the first time, the presence of an extensive low-density (2.95-3.05 g/cm 3) sub-crustal underplating. Such a layer is found to occur between depths of 11 and 20 km in the eastern basin of the Arabian Sea, and betweeen 45 and 60 km in the continental region where it is sandwiched in the lower lithosphere. The low density may have been caused as a result of serpentinization or fractionation of magma by a process related in some way to the Deccan volcanic event. Substantial depletion of both oceanic and continental lithosphere is indicated. We hypothesize that the present anatomy of the deformed lithosphere of the region at the K-T boundary is the result of substantial melt generated owing to frictional heat possibly giving rise to a hot cell like condition at the base of the lithosphere, resulting from the rapid movement of the Indian subcontinent between 80 and 53 Ma.

  18. Abundance and distribution of Tursiops truncatus in the Western Mediterranean Sea: an assessment towards the Marine Strategy Framework Directive requirements.

    PubMed

    Lauriano, Giancarlo; Pierantonio, Nino; Donovan, Greg; Panigada, Simone

    2014-09-01

    The Mediterranean Sea common bottlenose dolphin population has been assessed as Vulnerable according to the IUCN Red List Criteria. The species is also included in several International Agreements, European Union Regulations and Directives. Amongst them, a strict protection and identification of special conservation areas are requested by the EU Habitats Directive. Despite direct takes, by-catch, chemical and acoustic pollution, and prey depletion, general habitat degradation and fragmentation have been indicated as detrimental for the species, the degree to which these threats pose population risk is still largely unknown. At present it is thus not possible to depict the actual status of the population and to assess prospective trends. To address this gap in the current knowledge, line transect distance sampling aerial surveys were conducted in a wide portion of the Western Mediterranean Sea between the summer of 2010 and winter 2011. A total of 165 parallel transects equally spaced at 15 km were designed providing homogeneous coverage probability. Overall, 21,090 km were flown on effort and 16 bottlenose dolphin sightings were recorded and used for the analysis. The surface abundance and density estimates resulted in 1676 animals (CV = 38.25; 95% CI = 804-3492) with a density of 0.005 (CV = 38.25%). These results represent the first ever estimates for the common bottlenose dolphin over a wide portion of the Western Mediterranean Sea Subregion, with the potential to be useful baseline data to inform conservation. Specifically, they could be used as indicators under the Marine Strategy Framework Directive requirements, in conjunction with other study methods. PMID:24784442

  19. Seasonality of blue and fin whale calls and the influence of sea ice in the Western Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Širović, Ana; Hildebrand, John A.; Wiggins, Sean M.; McDonald, Mark A.; Moore, Sue E.; Thiele, Deborah

    2004-08-01

    The calling seasonality of blue ( Balaenoptera musculus) and fin ( B. physalus) whales was assessed using acoustic data recorded on seven autonomous acoustic recording packages (ARPs) deployed from March 2001 to February 2003 in the Western Antarctic Peninsula. Automatic detection and acoustic power analysis methods were used for determining presence and absence of whale calls. Blue whale calls were detected year round, on average 177 days per year, with peak calling in March and April, and a secondary peak in October and November. Lowest calling rates occurred between June and September, and in December. Fin whale calling rates were seasonal with calls detected between February and June (on average 51 days/year), and peak calling in May. Sea ice formed a month later and retreated a month earlier in 2001 than in 2002 over all recording sites. During the entire deployment period, detected calls of both species of whales showed negative correlation with sea ice concentrations at all sites, suggesting an absence of blue and fin whales in areas covered with sea ice. A conservative density estimate of calling whales from the acoustic data yields 0.43 calling blue whales per 1000 n mi 2 and 1.30 calling fin whales per 1000 n mi 2, which is about one-third higher than the density of blue whales and approximately equal to the density of fin whales estimated from the visual surveys.

  20. First observations on the abundance and composition of floating debris in the North-western Black Sea.

    PubMed

    Suaria, Giuseppe; Melinte-Dobrinescu, Mihaela C; Ion, Gabriel; Aliani, Stefano

    2015-06-01

    The occurrence of marine litter in the Black Sea region is poorly known and even less data have been reported on the abundance of floating debris. Here we present results from a ship-based visual survey carried out in the North-Western part of the Black Sea, providing the first preliminary data on the characteristics of floating debris in Romanian waters. High litter densities peaking to 135.9 items/km(2) were found in the study area (mean 30.9 ± 7.4 items/km(2)). Probably due to the proximity of the Danube delta, natural debris were on average, much more abundant than anthropogenic litter in most surveyed locations (mean 141.4 ± 47.1 items/km(2), max 1131.3 items/km(2)). Most of the 225 objects we sighted consisted of pieces of wood and other riparian debris (75.5%), however plastic items remained undoubtedly the most abundant type of litter, representing 89.1% of all sighted man-made items. The Black Sea is not exempt from the global invasion of floating debris, however data are still lacking and a basin-wide survey is urgently needed to identify accumulation areas and develop regionally effective solutions to the problem of marine litter. PMID:25881011

  1. Links Between the Deep Western Boundary Current, Labrador Sea Water Formation and Export, and the Meridional Overturning Circulation

    NASA Astrophysics Data System (ADS)

    Myers, Paul G.; Kulan, Nilgun

    2010-05-01

    Based on an isopyncal analysis of historical data, 3-year overlapping triad fields of objectively analysed temperature and salinity are produced for the Labrador Sea, covering 1949-1999. These fields are then used to spectrally nudge an eddy-permitting ocean general circulation model of the sub-polar gyre, otherwise forced by inter annually varying surface forcing based upon the Coordinated Ocean Reference Experiment (CORE). High frequency output from the reanalysis is used to examine Labrador Sea Water formation and its export. A number of different apprpoaches are used to estimate Labrador Sea Water formation, including an instanteous kinematic approach to calculate the annual rate of water mass subduction at a given density range. Historical transports are computed along sections at 53 and 56N for several different water masses for comparison with recent observations, showing a decline in the stength of the deep western boundary current with time. The variability of the strength of the meridional overturning circulation (MOC) from the reanalysis is also examined in both depth and density space. Linkages between MOC variability and water mass formation variability is considered.

  2. Postglacial change in sea level in the Western north atlantic ocean.

    PubMed

    Redfield, A C

    1967-08-11

    Radioactive carbon determinations of the age of peat indicate that at Bermuda, southern Florida, North Carolina, and Louisiana the relative sea level has risen at approximately the same rate, 2.5 x 10(-3) foot per year (0.76 x 10(-3) meter per year), during the past 4000 years. It is proposed tentatively that this is the rate of eustatic change in sea level. The rise in sea level along the northeastern coast of the United States has been at a rate much greater than this, indicating local subsidence of the land. Between Cape Cod and northern Virginia, coastal subsidence of 13 feet appears to have occurred between 4000 and 2000 years ago and has continued at a rate of about 1 x 10(-3) foot per year since then. On the northeastern coast of Massachusetts, subsidence of 6 feet occurred between 4000 and 3000 years ago; since then sea level has risen at about the eustatic rate. Between 12,000 and 4000 years ago, sea level rose at an average of about 11 x 10(-3) foot per year. The part played by local subsidence or temporary departures from the average rate during this period is uncertain. PMID:17792852

  3. Variations of the paleo-productivity in benthic foraminifera records in MIS 3 from western South China Sea

    NASA Astrophysics Data System (ADS)

    Niu, Y.; Du, J.; Huang, B.; Chen, M.

    2010-12-01

    Understanding climate change of last glacial age as the background information of climate forecasting is particularly important in climate research. Marine Isotope Stage 3 (MIS 3, 61-24 ka B.P.) is a relative warm and unstable period in the last glacial. Millennium scale abrupt climate changes, such as Heinrich events and Dansgaard-Oeschger (D-O) cycles, are identified in this period. Research topic on the variations of monsoon during the glacial cycles, especially in MIS 3, is critical for understanding low latitude climatic change and the global paleo-environment as a whole. Fortunately, high resolution sedimentary records in western South China Sea provide us valuable materials to uncover how East Asia Summer Monsoon (EASM) system acts in a highly fluctuating climate ambient like MIS 3. Core 17954 is located in the modern summer upwelling area off the Vietnam coast in western South China Sea (SCS), its sediments record the variations of upwelling generated by EASM. In this work, we carry out paleo-ecological analyses on planktonic ( Neogloboquadrina dutertrei, Globigerina bulloides) and benthic foraminifera (Bulimina aculeate, Uvigerina peregrina, Cibicidoides wuellerstorfi, ect.) sampled from Core 17954 to investigate paleo-productivity and nutrition change of western SCS and its relation to EASM. The results show that benthic and planktonic foraminifera have similar responses to nutrition change. Various indicators of productivity on the basis of benthic foraminiferal analyses reflect an overall three stage change trend: productivity gradually increases from the beginning of MIS 3 (60-40 ka) to its maximum during 35-30 ka, and finally declines after 30 ka. There is also another important discovery, if we observe the climate change in MIS 3 as a whole, we can also find western SCS and Northern Hemisphere High latitude have strong correspondences in such changes: Heinrich events coincided with high productivity events in the western SCS. Further, the result of

  4. Relationship between sea level pressures of the winter tropical western Pacific and the subsequent Asian summer monsoon

    NASA Astrophysics Data System (ADS)

    Bingyi, Wu; Dongxiao, Wang; Ronghui, Huang

    2003-07-01

    Using monthly mean National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data for the period 1958-1996, based on a new circulation index in the tropical western Pacific region, this paper investigates extreme winter circulation conditions in the northwestern Pacific and their evolution. The results show that the extreme winter circulation anomaly in the northwestern Pacific exhibits a strong association with those appearing in the high latitudes of the Northern Hemisphere including the northern Asian continent, part of the Barents Sea, and the northeastern Pacific. As the season progresses, an anticyclonic (cyclonic) circulation anomaly appearing in the north-western Pacific gradually moves northeastwards and extends westwards. Its axis in the west-east direction is also stretched. Therefore, easterly (westerly) anomalies in the southern part of the anticyclonic (cyclonic) circulation anomaly continuously expand westwards to the peninsula of India. Therefore, the South Asian summer monsoon would be weaker (stronger). Simultaneously, another interesting phenomenon is the evolution of SLP anomalies. As the season progresses (from winter to the following summer), SLP anomalies originating from the tropical western Pacific gradually move towards, and finally occupy the Asian continent, and further influence the thermal depression over the Asian continent in the following summer.

  5. Relationship between sea level pressures of the winter tropical western Pacific and the subsequent Asian summer monsoon

    NASA Astrophysics Data System (ADS)

    Wu, Bingyi; Wang, Dongxiao; Huang, Ronghui

    2003-07-01

    Using monthly mean National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data for the period 1958 1996, based on a new circulation index in the tropical western Pacific region, this paper investigates extreme winter circulation conditions in the northwestern Pacific and their evolution. The results show that the extreme winter circulation anomaly in the northwestern Pacific exhibits a strong association with those appearing in the high latitudes of the Northern Hemisphere including the northern Asian continent, part of the Barents Sea, and the northeastern Pacific. As the season progresses, an anticyclonic (cyclonic) circulation anomaly appearing in the north-western Pacific gradually moves northeastwards and extends westwards. Its axis in the west-east direction is also stretched. Therefore, easterly (westerly) anomalies in the southern part of the anticyclonic (cyclonic) circulation anomaly continuously expand westwards to the peninsula of India. Therefore, the South Asian summer monsoon would be weaker (stronger). Simultaneously, another interesting phenomenon is the evolution of SLP anomalies. As the season progresses (from winter to the following summer), SLP anomalies originating from the tropical western Pacific gradually move towards, and finally occupy the Asian continent, and further influence the thermal depression over the Asian continent in the following summer.

  6. Origin and pathways of Winter Intermediate Water in the Northwestern Mediterranean Sea using observations and numerical simulation

    NASA Astrophysics Data System (ADS)

    Juza, Mélanie; Renault, Lionel; Ruiz, Simon; Tintoré, Joaquin

    2013-12-01

    The study of water masses worldwide (their formation, spreading, mixing, and impact on general circulation) is essential for a better understanding of the ocean circulation and variability. In this paper, the formation and main pathways of Winter Intermediate Water (WIW) in the Northwestern Mediterranean Sea (NWMED) are investigated during the winter-spring 2011 using observations and numerical simulation. The main results show that the WIW, formed along the continental shelves of the Gulf of Lion and Balearic Sea, circulates southward following five preferential pathways depending on the WIW formation site location and the oceanic conditions. WIW joins the northeastern part of the Balearic Sea, or flows along the continental shelves until joining the Balearic Current (maximum of 0.33 Sv in early-April) or further south until the Ibiza Channel entrance. Two additional trajectories, contributing to water mass exchanges with the southern part of the Western Mediterranean Sea, bring the WIW through the Ibiza and Mallorca Channels (maxima of 0.26 Sv in late-March and 0.1 Sv in early-April, respectively). The circulation of WIW over the NWMED at 50-200 m depth, its mixing and spreading over the Western Mediterranean Sea (reaching the south of the Balearic Islands, the Algero-Provencal basin, the Ligurian and the Alboran Seas) suggest that the WIW may have an impact on the ocean circulation by eddy blocking effect, exchange of water masses between north and south subbasins of Western Mediterranean Sea through the Ibiza Channel or modification of the ocean stratification.

  7. Seismic stratigraphy of the Tyrrhenian Sea (western Mediterranean Sea) based on ODP leg results: Consequences for the basin evolution

    SciTech Connect

    Mascle, J.; Rehault, J.

    1988-08-01

    A revision of the seismic stratigraphy of the Tyrrehenian Sea is based on detailed calibrations between a dense network of single-channel seismic reflection lines, about 2,000 km of recent multichannel seismic profiles, and the seven sites drilled within the Tyrrhenian in 1986 during the Ocean Drilling Program Leg 107. These correlations substantiate that the basin has been submitted to a succession of short-lived rifting episodes progressively shifting toward the southeast and leading to the local creation of discrete oceanic crust floored basins. Most of the Tyr-rhenian basins and margins have been created in a very short time (between 8 and 2 m.y. in age) and are much younger than previously anticipated. Rifting processes have been acting on a very heterogeneous continental basement (including several suture zones); drifting has created small oceanic subbasins also floored by a very heterogeneous magmatic basement (including serpentinized peridotites). The hypothesis of an asymmetric evolution facilitated by one or several crustal detachment fault systems and driven by geodynamic mechanisms of the bordering collision/subduction is considered.

  8. Observations on the spatio-temporal patterns of radon along the western fault of the Dead Sea Transform, NW Dead Sea

    NASA Astrophysics Data System (ADS)

    Steinitz, G.; Piatibratova, O.; Malik, U.

    2015-05-01

    An extensive radon anomaly is developed along the western boundary fault of the Dead Sea Transform in the NW sector of the Dead Sea, extending 15-20 km north-south. The highest radon values occur in proximity to the fault scarp. Radon is measured, in gravel (depth 1.5-3 m) at sites located at a) on-fault positions, 1-30 meters east of the fault scarp, and b) off-fault positions located 600-800 the east. Prominent signals occur in the annual and daily periodicity bands, as well as non-periodic multi-day variations (2-20 days). Modulations occur among the annual variation and the multi-day and the daily signals, and between the multi-day and the daily signal. Dissimilar variation patterns occur at on-fault versus off-fault sites in the time domain, and in the relative amplitude of the daily periodicities. Variation patterns and their modulations are similar to those encountered in experimental simulations. It is concluded that: 1) above surface atmospheric influences can be excluded; 2) a remote above surface influence probably drives the periodic components in the annual and diurnal bands; 3) diurnal as well as the multi-day signals are modified and inter-modulated by near field geological (static) and geophysical (dynamic) influences. Systematically different influences are operating at on-fault versus off-fault positions, So far the natures of these near field influences are unidentified.

  9. Population model for sea otters in western Prince William sound. Restoration project 93043-3. Sea otter demographics. Exxon Valdez oil spill restoration project final report

    SciTech Connect

    Udevitz, M.S.; Ballachey, B.E.; Bruden, D.L.

    1996-05-01

    A large portion of the western Prince William Sound (PWS) sea otter population was killed by the Exxon Valdez oil spill in March 1989, but little is known about the dynamics of the population before the spill in March 1989, or the rate at which the population can be expected to recover. We estimated age-specific reproductive and survival rates for the western PWS population before the spill based on examinations or reproductive tracts and the age structure of carcasses collected in 1989. We developed a new technique for estimating survival rates that uses age-structure and age-at-death data, and does not require the assumption of a stable age structure. Because of the lack of data for estimating juvenile survival rates, were considered a series of 4 potential scenarios. The population was projected to decrease slightly during the first year under all of the scenarios and then begin increasing, achieving maximum rates of increase ranging from 10% to 14% per year and recovering to its estimated 1985 population size in 10 to 23 years. Projected population sizes during the first few years after the spill are in broad agreement with estimates based on boat surveys in 1990, 1991, and 1993.

  10. ENSURF: multi-model sea level forecast - implementation and validation results for the IBIROOS and Western Mediterranean regions

    NASA Astrophysics Data System (ADS)

    Pérez, B.; Brouwer, R.; Beckers, J.; Paradis, D.; Balseiro, C.; Lyons, K.; Cure, M.; Sotillo, M. G.; Hackett, B.; Verlaan, M.; Fanjul, E. A.

    2012-03-01

    ENSURF (Ensemble SURge Forecast) is a multi-model application for sea level forecast that makes use of several storm surge or circulation models and near-real time tide gauge data in the region, with the following main goals: 1. providing easy access to existing forecasts, as well as to its performance and model validation, by means of an adequate visualization tool; 2. generation of better forecasts of sea level, including confidence intervals, by means of the Bayesian Model Average technique (BMA). The Bayesian Model Average technique generates an overall forecast probability density function (PDF) by making a weighted average of the individual forecasts PDF's; the weights represent the Bayesian likelihood that a model will give the correct forecast and are continuously updated based on the performance of the models during a recent training period. This implies the technique needs the availability of sea level data from tide gauges in near-real time. The system was implemented for the European Atlantic facade (IBIROOS region) and Western Mediterranean coast based on the MATROOS visualization tool developed by Deltares. Results of validation of the different models and BMA implementation for the main harbours are presented for these regions where this kind of activity is performed for the first time. The system is currently operational at Puertos del Estado and has proved to be useful in the detection of calibration problems in some of the circulation models, in the identification of the systematic differences between baroclinic and barotropic models for sea level forecasts and to demonstrate the feasibility of providing an overall probabilistic forecast, based on the BMA method.

  11. Holocene sea-level changes and barrier reef formation on an oceanic island, Palau Islands, western Pacific

    NASA Astrophysics Data System (ADS)

    Kayanne, Hajime; Yamano, Hiroya; Randall, Richard H.

    2002-06-01

    Internal facies and development of an oceanic island's barrier reef were revealed by the stratigraphical study of six drill cores in Palau Islands, western Pacific. The Holocene reef development is primarily constrained at its foundation by the antecedent topography of Pleistocene substratum. Holocene barrier reef is an increment on the Pleistocene barrier reef, which had been subaerially exposed during glacial stages. About 8300 cal. year BP (calibrated calendar years B.P.), branching Acropora facies initially formed a bank on the seaward side of a Pleistocene limestone surface with a vertical accumulation rate as high as 30 m/ka (ka=1000 years). After 7200 cal. year BP, when the sea-level rise rate decreased, reef crest facies caught up with the sea surface with an accumulation rate of less than 2.2 m/ka. Corals found in the reef crest facies are similar to the present-day reef crest corals dominated by Acropora digitifera and A. humilis. After the reef crest was formed, bioclastic sand and gravel facies prograded lagoonward of the reef crest and consisted mostly of reef derived materials. The construction of patch reefs post-dated the barrier reef formation. The mature barrier reef provided calm conditions inside the lagoon, which then led to the construction of patch reefs and fringing reefs. Sea-level changes deduced from the accumulation curves show rapid rise before 7200 cal. year BP followed by a slight rise of 4 m at its maximum. This change in sea-level rise rate inspired the change in reef facies from branching Acropora to reef crest.

  12. Sea-ice melt CO2-carbonate chemistry in the western Arctic Ocean: meltwater contributions to air-sea CO2 gas exchange, mixed-layer properties and rates of net community production under sea ice

    NASA Astrophysics Data System (ADS)

    Bates, N. R.; Garley, R.; Frey, K. E.; Shake, K. L.; Mathis, J. T.

    2014-12-01

    The carbon dioxide (CO2)-carbonate chemistry of sea-ice melt and co-located, contemporaneous seawater has rarely been studied in sea-ice-covered oceans. Here, we describe the CO2-carbonate chemistry of sea-ice melt (both above sea-ice as "melt ponds" and below sea-ice as "interface waters") and mixed-layer properties in the western Arctic Ocean in the early summer of 2010 and 2011. At 19 stations, the salinity (∼0.5 to <6.5), dissolved inorganic carbon (DIC; ∼20 to <550 μmol kg-1) and total alkalinity (TA; ∼30 to <500 μmol kg-1) of above-ice melt pond water was low compared to the co-located underlying mixed layer. The partial pressure of CO2 (pCO2) in these melt ponds was highly variable (∼<10 to >1500 μatm) with the majority of melt ponds acting as potentially strong sources of CO2 to the atmosphere. The pH of melt pond waters was also highly variable ranging from mildly acidic (6.1 to 7) to slightly more alkaline than underlying seawater (>8.2 to 10.8). All of the observed melt ponds had very low (<0.1) saturation states (Ω) for calcium carbonate (CaCO3) minerals such as aragonite (Ωaragonite). Our data suggest that sea-ice generated alkaline or acidic type melt pond water. This melt water chemistry dictates whether the ponds are sources of CO2 to the atmosphere or CO2 sinks. Below-ice interface water CO2-carbonate chemistry data also indicated substantial generation of alkalinity, presumably owing to dissolution of CaCO3 in sea-ice. The interface waters generally had lower pCO2 and higher pH/Ωaragonite than the co-located mixed layer beneath. Sea-ice melt thus contributed to the suppression of mixed-layer pCO2, thereby enhancing the surface ocean's capacity to uptake CO2 from the atmosphere. Our observations contribute to growing evidence that sea-ice CO2-carbonate chemistry is highly variable and its contribution to the complex factors that influence the balance of CO2 sinks and sources (and thereby ocean acidification) is difficult to

  13. Genome sequence of Oceanicaulis sp. strain HTCC2633, isolated from the Western Sargasso Sea.

    PubMed

    Oh, Hyun-Myung; Kang, Ilnam; Vergin, Kevin L; Lee, Kiyoung; Giovannoni, Stephen J; Cho, Jang-Cheon

    2011-01-01

    The genus Oceanicaulis represents dimorphic rods that were originally isolated from a marine dinoflagellate. Here, we announce the genome sequence of Oceanicaulis sp. strain HTCC2633, isolated by dilution-to-extinction culturing from the Sargasso Sea. The genome information of strain HTCC2633 indicates a chemoorganotrophic way of life of this strain. PMID:21036991

  14. Biogeography of Persephonella in deep-sea hydrothermal vents of the Western Pacific.

    PubMed

    Mino, Sayaka; Makita, Hiroko; Toki, Tomohiro; Miyazaki, Junichi; Kato, Shingo; Watanabe, Hiromi; Imachi, Hiroyuki; Watsuji, Tomo-O; Nunoura, Takuro; Kojima, Shigeaki; Sawabe, Tomoo; Takai, Ken; Nakagawa, Satoshi

    2013-01-01

    Deep-sea hydrothermal vent fields are areas on the seafloor with high biological productivity fueled by microbial chemosynthesis. Members of the Aquificales genus Persephonella are obligately chemosynthetic bacteria, and appear to be key players in carbon, sulfur, and nitrogen cycles in high temperature habitats at deep-sea vents. Although this group of bacteria has cosmopolitan distribution in deep-sea hydrothermal ecosystem around the world, little is known about their population structure such as intraspecific genomic diversity, distribution pattern, and phenotypic diversity. We developed the multi-locus sequence analysis (MLSA) scheme for their genomic characterization. Sequence variation was determined in five housekeeping genes and one functional gene of 36 Persephonella hydrogeniphila strains originated from the Okinawa Trough and the South Mariana Trough (SNT). Although the strains share >98.7% similarities in 16S rRNA gene sequences, MLSA revealed 35 different sequence types (ST), indicating their extensive genomic diversity. A phylogenetic tree inferred from all concatenated gene sequences revealed the clustering of isolates according to the geographic origin. In addition, the phenotypic clustering pattern inferred from whole-cell matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF/MS) analysis can be correlated to their MLSA clustering pattern. This study represents the first MLSA combined with phenotypic analysis indicative of allopatric speciation of deep-sea hydrothermal vent bacteria. PMID:23630523

  15. Tectonic configuration of the western Arabian continental margin, southern Red Sea, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Bohannon, R.G.

    1987-01-01

    A tectonic reconstruction of pre-Red Sea Afro/Arabia suggests that the early rift was narrow with intense extension confined to an axial belt 20 to 40 km wide. Steep Moho slopes probably developed during rift formation as indicated by published gravity data, two published seismic interpretations and the surface geology.

  16. Interannual relationships between the tropical sea surface temperature and summertime subtropical anticyclone over the western North Pacific

    NASA Astrophysics Data System (ADS)

    Chung, Pei-Hsuan; Sui, Chung-Hsiung; Li, Tim

    2011-07-01

    The interannual variability of the Western North Pacific Subtropical High (WNPSH) in boreal summer is investigated with the use of the NCEP/NCAR Reanalysis Data. The most significant change of the 500 hPa geopotential height field appears at the western edge of the WNPSH, with dominant 2-3 year and 3-5 year power spectrum peaks. The 2-3 year oscillation of the WNPSH and associated circulation and sea surface temperature (SST) patterns possess a coherent eastward propagating feature, with a warm SST anomaly (SSTA) and anomalous ascending motion migrating from the tropical Indian Ocean in the preceding autumn to the maritime continent in the concurrent summer of a strong WNPSH. A strong WNPSH is characterized by anomalous anticyclonic circulation and maximum subsidence in the western North Pacific (WNP). The anomalous WNPSH circulation has an equivalent barotropic vertical structure and resides in the sinking branch of the local Hadley circulation, triggered by enhanced convection over the maritime continent. A heat budget analysis reveals that the WNPSH is maintained by radiative cooling. The 3-5 year oscillation of the WNPSH exhibits a quasi-stationary feature, with a warm SSTA (anomalous ascending motion) located in the equatorial central eastern Pacific and Indian Ocean and a cold SSTA (anomalous descending motion) located in the western Pacific. The anomaly pattern persists from the preceding winter to the concurrent summer of a high WNPSH. The greatest descent is located to the southeast of the anomalous anticyclone center, where a baroclinic vertical structure is identified. The zonal phase difference and the baroclinic vertical structure suggest that the anomalous anticyclone on this timescale is a Rossby wave response to a negative latent heating associated with the persistent local cold SSTA. ECHAM4 model experiments further confirm that the 2-3 year mode is driven by the SSTA forcing over the maritime continent, while the 3-5 year mode is driven by the

  17. The Role of Middle and Late Holocene North Pacific Sea Surface Temperatures on Precipitation Patterns in the Western United States

    NASA Astrophysics Data System (ADS)

    Barron, J. A.; Anderson, L.; Starratt, S.; Wahl, D.; Anderson, L.; Addison, J. A.

    2015-12-01

    Comparative analyses of marine and terrestrial proxy records reveal regional changes in precipitation seasonality and relationships with sea surface temperatures (SSTs) as indicators of ocean-atmosphere dynamics. Enhanced La Niña-like conditions and cooler SSTs characterized the middle Holocene (~8.O to 4.0 ka) waters off northern California and in the eastern equatorial Pacific. Terrestrial records suggest that winters in the western US were generally dry, although wetter intervals attributed to winter precipitation beginning at ~5.5 ka are documented in coastal Oregon and Washington and in the northern Great Basin. Proxy studies suggest that the North American Monsoon (NAM) intensified beginning at ~7.5 ka, coinciding with warming Gulf of California SSTs coupled with a more northerly position of the Intertropical Convergence Zone (ITCZ). If monsoonal precipitation spread northward into the eastern Great Basin and the western Rockies of Colorado, it is possible that wetter intervals of the middle Holocene in Nevada, Utah, and western Colorado may reflect increases in both summer and winter precipitation. El Niño event frequency and intensity began increasing between 4.0 and 3.0 ka, when modern ocean-atmosphere dynamics appear to have been established along the California coastal margin. Effects included cool, wet winters, enhanced spring coastal upwelling that extended into the summer, and higher September-October SSTs corresponding with the end of the coastal upwelling season. Winters became wetter in both the coastal and interior regions of the western US, while spring and summers generally became drier. The intensity of NAM precipitation also declined due to a more southerly mean position of the ITCZ. By ~3.0 cal ka the modern climatology of the margins of eastern North Pacific was established, resulting in intensification of the northwest-southwest precipitation dipole and the development of distinct Pacific Decadal Oscillation cycles.

  18. Aptian-Albian sea level history from Guyots in the western Pacific

    NASA Astrophysics Data System (ADS)

    RöHl, Ursula; Ogg, James G.

    1996-10-01

    Relative sea level fluctuations are an important control on patterns of sedimentation on continental margins and provide a valuable tool for regional correlations. One of the main objectives of combined Ocean Drilling Program Legs 143 and 144 was drilling the thick carbonate caps of a suite of seamounts, called guyots, scattered over the northwestern Pacific. The array of drowned Cretaceous banks includes four carbonate banks of Aptian-Albian age. These particular carbonate banks display emergent surfaces if regional sea level falls faster than the rate of guyot subsidence, or intervals of condensed parasequences and well-cemented peritidal crypto-algal flats if the rate of sea level fall is slightly less than guyot subsidence. Rapid rises of sea level following these sequence boundaries are recorded as drowning of the emergent horizons or as pronounced deepening of facies. The cored lithologies and downhole geophysical and geochemical logs were used to identify depositional sequences and surfaces of exceptional shallowing or deepening. A combination of biostratigraphic datums, carbon and strontium isotope curves, relative magnitude of surfaces of emergence, relative thicknesses of depositional sequences, sea level events, and counts of upward shallowing cycles or parasequences were used to correlate sequences among the four sites. After compensating for thermal subsidence rates at each guyot, an identical pattern of major Aptian-Albian eustatic sea level events is evident throughout this large portion of the Pacific Ocean. There are approximately 12 Aptian and 12 Albian significant sequence boundaries, of which a third were associated with major episodes of emergence. When these events are compared with Aptian-Albian relative sea level changes observed in European shelf successions, the major sequence boundaries and transgressive surges can be easily correlated, and it appears that both regions also display the same number of minor events. Therefore we can apply

  19. Satellite observation of bio-optical indicators related to North-Western Black Sea coastal zone changes

    NASA Astrophysics Data System (ADS)

    Zoran, Maria

    Satellite remote sensing provides a means for locating, identifying and mapping certain coastal zone features and assessing of spatio-temporal changes.The Romanian coastal zone of the Black Sea is a mosaic of complex, interacting ecosystems, exposed to dramatic changes due to natural and anthropogenic causes (increase in the nutrient and pollutant load of rivers input, industrial and municipal wastewater pollution along the coast, and dumping on the open sea). This study focuses on the assessment of coastal zone land cover changes based on the fusion of satellite remote sensing data.The evaluation of coastal zone landscapes is based upon different sub-functions which refer to landscape features such as water, soil, land-use, buildings, groundwater, biotope types. Mixed pixels result when the sensor's instantaneous field-of-view includes more than one land cover class on the ground. Based on different satellite data (Landsat TM, ETM, SAR ERS, IKONOS, Quickbird, and MODIS) was performed object recognition for North-Western Black Sea coastal zone. Preliminary results show significant coastline position changes of North Western Black Sea during the period of 1987-2007 and urban growth of Constantza town. Also the change in the position of the coastline is examined and linked to the urban expansion in order to determine if the changes are natural or anthropogenic. A distinction is made between landfill/sedimentation processes on the one hand and dredging/erosion processes on the other. Waves play an important role for shoreline configuration. Wave pattern could induce erosion and sedimentation. A quasi-linear model was used to model the rate of shoreline change. The vectors of shoreline were used to compare with wave spectra model in order to examine the accuracy of the coastal erosion model. The shoreline rate modeled from vectors data of SAR ERS-1 has a good correlation with a quasi-linear model. Wave refraction patterns are a good index for shoreline erosion. A coast

  20. Lithospheric-scale effects of a subduction-driven Alboran plate: improved neotectonic modeling

    NASA Astrophysics Data System (ADS)

    Neres, Marta; Carafa, Michele; Terrinha, Pedro; Fernandes, Rui; Matias, Luis; Duarte, João; Barba, Salvatore

    2016-04-01

    The presence of a subducted slab under the Gibraltar arc is now widely accepted. However, discussion still remains on whether subduction is active and what is its influence in the lithospheric processes, in particular in the observed geodesy, deformation rates and seismicity. Aiming at bringing new insights into the discussion, we have performed a neotectonic numerical study of a segment of the Africa-Eurasia plate boundary, from the Gloria fault to the Northern Algerian margin. Specifically, we have tested the effect of including or excluding an independently driven Alboran plate, i.e. testing active subduction versus inactive subduction (2plates versus 3plates scenarios). We used the dynamic code SHELLS (Bird et al., 2008) to model the surface velocity field and the ongoing deformation, using a new up-to-date simplified tectonic map of the region, new available lithospheric data and boundary conditions determined from two alternative Africa-Eurasia angular velocities, respectively: SEGAL2013, a new pole based on stable Africa and stable Eurasia gps data (last decades); and MORVEL, a geological-scale pole (3.16 Ma). We also extensively studied the variation within the parametric space of fault friction coefficient, subduction resistance and surface velocities imposed to the Alboran plate. The final run comprised a total of 5240 experiments, and each generated model was scored against geodetic velocities, stress direction data and seismic strain rates. The preferred model corresponds to the 3plates scenario, SEGAL2013 pole and fault friction of 0.225, with scoring results: gps misfit of 0.78 mm/yr; SHmax misfit of 13.6° and correlation with seismic strain rate of 0.62, significantly better than previous models. We present predicted fault slip rates for the recognized active structures and off-faults permanent strain rates, which can be used for seismic and tsunami hazard calculations (the initial motivation for this work was contributing for calculation of

  1. Gravity field of the Western Weddell Sea: Comparison of airborne gravity and Geosat derived gravity

    NASA Technical Reports Server (NTRS)

    Bell, R. E.; Brozena, J. M.; Haxby, W. F.; Labrecque, J. L.

    1989-01-01

    Marine gravity surveying in polar regions was typically difficult and costly, requiring expensive long range research vessels and ice-breakers. Satellite altimetry can recover the gravity field in these regions where it is feasible to survey with a surface vessel. Unfortunately, the data collected by the first global altimetry mission, Seasat, was collected only during the austral winter, producing a very poor quality gravitational filed for the southern oceans, particularly in the circum-Antarctic regions. The advent of high quality airborne gravity (Brozena, 1984; Brozena and Peters, 1988; Bell, 1988) and the availability of satellite altimetry data during the austral summer (Sandwell and McAdoo, 1988) has allowed the recovery of a free air gravity field for most of the Weddell Sea. The derivation of the gravity field from both aircraft and satellite measurements are briefly reviewed, before presenting along track comparisons and shaded relief maps of the Weddell Sea gravity field based on these two data sets.

  2. Coralligenous "atolls": discovery of a new morphotype in the Western Mediterranean Sea.

    PubMed

    Bonacorsi, Marina; Pergent-Martini, Christine; Clabaut, Philippe; Pergent, Gérard

    2012-01-01

    Coralligenous habitat and rhodoliths beds are very important in terms of biodiversity in the Mediterranean Sea. During an oceanographic campaign, carried out in northern Cap Corse, new coralligenous structures have been discovered. These structures, never previously identified in the Mediterranean Sea, are named "coralligenous atolls" because of their circular shape. The origin and growth dynamics of these atolls are still unknown but their form does not appear to result from hydrodynamic action and an anthropogenic origin also seems unlikely. However, this kind of shape seems rather closer to that of other circular structures (e.g. pockmarks) the origin of which is related to gaseous emissions. Further studies are needed to confirm this hypothesis through chemical analysis. PMID:23199634

  3. Bioaccumulation of persistent organochlorine pesticides (OCPs) by gray whale and Pacific walrus from the western part of the Bering Sea.

    PubMed

    Tsygankov, Vasiliy Yu; Boyarova, Margarita D; Lukyanova, Olga N

    2015-10-15

    The feeding habits of a gray whale (Eschrichtius robustus) and a Pacific walrus (Odobenus rosmarus divergens), caught from the western Bering Sea in the summers of 2010 and 2011, have been studied, and concentration of persistent organochlorine pesticides (OCPs) in their organs determined. The total OCP concentration (∑HCH+∑DDT) in muscles and liver of the gray whales varies from 297 to 3581 and from 769 to 13,808 ng/g lipids, respectively. The total OCP concentration (∑HCH+∑DDT) in muscles and liver of the Pacific walruses varies from 197 to 5659 and from 4856 to 90,263 ng/g lipids, respectively. The specifics of diet as a source of pesticide accumulation in these two marine mammal species are discussed. PMID:26169228

  4. Density of pack-ice seals and penguins in the western Weddell Sea in relation to ice thickness and ocean depth

    NASA Astrophysics Data System (ADS)

    Flores, Hauke; Haas, Christian; van Franeker, Jan Andries; Meesters, Erik

    2008-04-01

    Aerial band transect censuses were carried out parallel with ice thickness profiling surveys in the pack ice of the western Weddell Sea during the ISPOL (Ice Station POLarstern) expedition of R.V. Polarstern from November 2004 to January 2005. Three regions were surveyed: the deep sea of the Weddell Sea, a western continental shelf/slope region where R.V. Polarstern passively drifted with an ice floe (ISPOL), and a northern region (N). Animal densities were compared among regions and in relation to bathymetry and ice thickness distribution. Crabeater seals Lobodon carcinophaga were the most abundant species in all three regions. Their density was significantly lower in the deep sea (0.50 km -2) than in the ISPOL (1.00 km -2) and northern regions (1.21 km -2). Weddell seals Leptonychotes weddellii were not sighted in the deep-sea region, their density elsewhere ranging from 0.03 (N) to 0.08 km -2 (ISPOL). Leopard seals Hydrurga leptonyx were observed in all three areas, but could only be quantified in the deep-sea (0.05 km -2) and northern regions (0.06 km -2). The abundance of emperor penguins Aptenodytes forsteri was markedly higher in the northern (0.75 km -2) than in the ISPOL (0.13 km -2) and the deep-sea region (not quantified). Crabeater seal density was significantly related to ocean depth and modal ice thickness.

  5. Effects of neotectonic and sedimentary processes on the seafloor geomorphology of the Tekirdag Basin of the western Marmara Sea (Turkey)

    NASA Astrophysics Data System (ADS)

    Ergin, Mustafa; Yigit-Faridfathi, Füsun

    2010-05-01

    This study forms part of a project (TUBITAK YDABCAG 101Y071) with the main purpose of investigation of late Quaternary slope stability, sediment mass movements and turbidite formations in the tectonically active Tekirdag Basin and its margins from the western Marmara Sea. The results were also intended to relate to the major earthquakes and sea-level changes. During this project, in 2001 aboard the former R/V MTA Sismik-1, a total of 100 km seismic reflection profiles were obtained along three tracklines representing from shelf to slope to deep basin environments. A multichannel airgun seismic system and well-known methods and principles of seismic stratigraphy was used for interpretations. At 11 sites from 29 to 1111 m water depths gravity sediment cores were taken having 100 to 359 cm recoveries and textural and structural characteristics were determined using standard petrographic methods. The NEE-SWW directed seismic profile (TKD-01) which runs parallel to the North Anatolian Fault zone displayed syntectonic sedimentation with negative flower structure that increased in thickness toward the Ganos Fault and pinched out in the east. ENE section of this profile also bears structures of underwater landslides with slump facies. Seismic profile TKD-02 which crosses the Tekirdag Basin in WNW-ESE direction most likely displays major 3 fault segments of the NAF zone. Many faults and syntectonic sedimentation structure can be recognized on this profile. A morphological feature of a sediment wedge or former lowstand delta at the present shelf edge can be related to the effects of last sea-level change. Mounded and chaotic seismic reflection configurations which indicate channel and slope-front fill as well as slump facies are thought to reflect submarine slides and slumps. Other morphological features such as incised submarine valleys or channels running E-W direction are also present on this profile. The seismic profile (TKD-03) runs from NNW to SSE across the basin and

  6. A case study of the mesoscale dynamics in the North-Western Mediterranean Sea: a combined data-model approach

    NASA Astrophysics Data System (ADS)

    Guihou, Karen; Marmain, Julien; Ourmières, Yann; Molcard, Anne; Zakardjian, Bruno; Forget, Philippe

    2013-07-01

    The Northern current is the main circulation feature of the North-Western Mediterranean Sea. While the large-scale to mesoscale variability of the northern current (NC) is well known and widely documented for the Ligurian region, off Nice or along the Gulf of Lions shelf, few is known about the current instabilities and its associated mesoscale dynamics in the intermediate area, off Toulon. Here, we took advantage of an oceanographic cruise of opportunity, the start of a HF radar monitoring programme in the Toulon area and the availability of regular satellite sea surface temperature and chlorophyll a data, to evaluate the realism of a NEMO-based regional high-resolution model and the added value brought by HF radar. The combined analysis of a 1/64° configuration, named GLAZUR64, and of all data sets revealed the occurrence of an anticyclonic coastal trapped eddy, generated inside a NC meander and passing the Toulon area during the field campaign. We show that this anticyclonic eddy is advected downstream along the French Riviera up to the study region and disturbs the Northern current flow. This study aims to show the importance of combining observations and modelling when dealing with mesoscale processes, as well as the importance of high-resolution modelling.

  7. Spatial and temporal variation of seasonal synchrony in the deep-sea shrimp Aristeus antennatus in the Western Mediterranean

    NASA Astrophysics Data System (ADS)

    Hidalgo, Manuel; Rueda, Lucía; Molinero, Juan Carlos; Guijarro, Beatriz; Massutí, Enric

    2015-08-01

    Resolving drivers of spatial synchrony in marine species is fundamental for the management and conservation of deep-sea ecosystems. Here we examine an 11-year data set of monthly catches per unit of effort (CPUE) of the red-shrimp Aristeus antennatus. These data comprise 16 locations of two population subunits in the Western Mediterranean, the Catalan coast and the Balearic archipelago. The analysis of their seasonal covariation and its space-time structure showed small-scale geographical segregation of locations linked with the seasonal fluctuations of CPUE. Results further revealed that seasonal synchrony dominates at short spatial scales (ca. 50 km), while asynchrony prevails are broader spatial scales (ca. 200-300 km). This spatial pattern, however, varied over the period examined, although it was specific for each population subunit suggesting contrasting drivers of seasonal synchrony. The Balearic Islands, a patchier population subunit, displayed a seasonal synchrony pattern mainly dependent on biological and oceanographic processes at local scales. By contrast, in the Catalan coast, the pattern appeared related with regional-scale climate, which triggers spatial differences in the phenology of primary producers and the timing of food advection to the seabed. These cascading processes depicted by our investigation shed light on underlying mechanisms shaping the temporal synchrony of broadly distributed deep-sea populations.

  8. Aerial surveys of endangered whales in the Alaskan Chukchi and western Beaufort Seas, 1990. Final report, Oct-Nov 90

    SciTech Connect

    Moore, S.E.; Clarke, J.T.

    1991-06-01

    In keeping with the National Environmental Policy Act (1969), the Marine Mammal Protection Act (1972) and the Endangered Species Act (1973), the OCS Lands Act Amendments (1978) established a management policy that included studies in OCS lease sale areas to ascertain potential environmental impacts of oil and gas development on OCS marine coastal environments. The Minerals Management Service (MMS) is the agency responsible for these studies and for the leasing of submerged Federal lands. The report summarizes the 1990 investigations of the distribution, abundance, migration, behavior and habitat relationships of endangered whales in the Alaskan Chukchi and western Beaufort Seas (hereafter, study area); 1990 was the second of a three year (1989-91) study. The Bering Sea stock of bowhead whales (Balaena mysticetus) was the principal species studied, with incidental sightings of all other marine mammals routinely recorded. The 1990 season was compromised by circumstances that restricted the availability of the survey aircraft (Grumman Goose, model G21G) to the period 26 October - 7 November; opportunistic surveys were flown in the study area from 3-25 October. In 1990, there were 14 sightings of 19 bowheads from 9-29 October; 5 whales, including 2 calves, were seen north of the study area. One gray whale, 110 belukhas and 53 polar bears were also seen. Over nine survey seasons (1982-90), there were 240 sightings of 520 bowhead whales and 148 sightings of 398 gray whales.

  9. Time-Series Photographs of the Sea Floor in Western Massachusetts Bay: June 1998 to May 1999

    USGS Publications Warehouse

    Butman, Bradford; Alexander, P. Soupy; Bothner, Michael H.

    2004-01-01

    This report presents time-series photographs of the sea floor obtained from an instrumented tripod deployed at Site A in western Massachusetts Bay (42? 22.6' N., 70? 47.0' W., 30 m water depth, figure 1) from June 1998 through May 1999. Site A is approximately 1 km south of an ocean outfall that began discharging treated sewage effluent from the Boston metropolitan area into Massachusetts Bay in September 2000. Time-series photographs and oceanographic observations were initiated at Site A in December 1989 and are anticipated to continue to September 2005. This one of a series of reports that present these images in digital form. The objective of these reports is to enable easy and rapid viewing of the photographs and to provide a medium-resolution digital archive. The images, obtained every 4 hours, are presented as a movie (in .avi format, which may be viewed using an image viewer such as QuickTime or Windows Media Player) and as individual images (.tif format). The images provide time-series observations of changes of the sea floor and near-bottom water properties.

  10. Time-Series Photographs of the Sea Floor in Western Massachusetts Bay: June 1997 to June 1998

    USGS Publications Warehouse

    Butman, Bradford; Alexander, P. Soupy; Bothner, Michael H.

    2004-01-01

    This report presents time-series photographs of the sea floor obtained from an instrumented tripod deployed at Site A in western Massachusetts Bay (42? 22.6' N., 70? 47.0' W., 30 m water depth, figure 1) from June 1997 through June 1998. Site A is approximately 1 km south of an ocean outfall that began discharging treated sewage effluent from the Boston metropolitan area into Massachusetts Bay in September 2000. Time-series photographs and oceanographic observations were initiated at Site A in December 1989 and are anticipated to continue to September 2005. This is the first in a series of reports planned to summarize and distribute these images in digital form. The objective of these reports is to enable easy and rapid viewing of the photographs and to provide a medium-resolution digital archive. The images, obtained every 4 hours, are presented as a movie (in .avi format, which may be viewed using an image viewer such as QuickTime or Windows Media Player) and as individual images (.tif format). The images provide time-series observations of changes of the sea floor and near-bottom water properties.

  11. Response of rapidly developing extratropical cyclones to sea surface temperature variations over the western Kuroshio-Oyashio confluence region

    NASA Astrophysics Data System (ADS)

    Hirata, Hidetaka; Kawamura, Ryuichi; Kato, Masaya; Shinoda, Taro

    2016-04-01

    The dynamical response of rapidly developing extratropical cyclones to sea surface temperature (SST) variations over the western Kuroshio-Oyashio confluence (WKOC) region was examined by using regional cloud-resolving simulations. This study specifically highlights an explosive cyclone that occurred in early February 2014 and includes a real SST experiment (CNTL run) and two sensitivity experiments with warm and cool SST anomalies over the WKOC region (warm and cool runs). The results derived from the CNTL run indicated that moisture supply from the ocean was enhanced when the dry air associated with the cold conveyor belt (CCB) overlapped with warm currents. Further, the evaporated moisture contributed substantially to latent heat release over the bent-back front with the aid of the CCB, leading to cyclone intensification and strengthening of the asymmetric structure around the cyclone's center. Such successive processes were more active in the warm run than in the cool run. The dominance of the zonally asymmetric structure resulted in a difference in sea level pressure around the bent-back front between the two runs. The WKOC SST variations have the potential to affect strong wind distributions along the CCB through modification of the cyclone's inner system. Additional experiments with two other cyclones showed that the cyclone response to the WKOC SST variations became evident when the CCB north of the cyclone's center overlapped with that region, confirming that the dry nature of the CCB plays an important role in latent heat release by allowing for larger moisture supply from the ocean.

  12. Direct ageing of Thunnus thynnus from the eastern Atlantic Ocean and western Mediterranean Sea using dorsal fin spines.

    PubMed

    Luque, P L; Rodriguez-Marin, E; Landa, J; Ruiz, M; Quelle, P; Macias, D; Ortiz De Urbina, J M

    2014-06-01

    This study deals with important methodology issues that affect age estimates of eastern Atlantic bluefin tuna Thunnus thynnus using dorsal fin spines. Nearly 3800 spine sections were used from fish caught in the north-east Atlantic Ocean and western Mediterranean Sea over a 21 year period. Edge type and marginal increment analyses indicated a yearly periodicity of annulus formation with the translucent bands (50% of occurrence) appearing from October to May. Nucleus vascularization seriously affected specimens older than 6 years, with the disappearance of 40-50% of the presumed annuli by that age. An alternate sectioning location was a clear improvement and this finding is an important contribution to the methodology of using this structure for ageing the full-length range of eastern T. thynnus. Finally, there were no significant differences between the coefficients of von Bertalanffy growth model estimated from mean length at age data (L∞  = 327.4; k = 0.097; t0  = -0.838) and those estimated from the growth curves accepted for the eastern and western T. thynnus management units. PMID:24890407

  13. Observed evidence of the anomalous South China Sea western boundary current during the summers of 2010 and 2011

    NASA Astrophysics Data System (ADS)

    Shu, Yeqiang; Xue, Huijie; Wang, Dongxiao; Xie, Qiang; Chen, Ju; Li, Jian; Chen, Rongyu; He, Yunkai; Li, Daning

    2016-02-01

    Seven years of directly measured current data from a mooring in the Xisha area of the South China Sea (SCS), together with shipboard ADCP and satellite data, have shown the western boundary current (WBC) anomaly and its vertical structure during the summers of 2010 and 2011. The observed WBC presented obvious year-to-year variability, especially in the summer. Overall, the summer mean velocity at the mooring site over 7-year (2007-2013) was northeastward. The moored ADCP showed that the northeastward velocity was particularly strong in the summer of 2010, but the increase was confined in the upper 120 m. In contrast, the northeastward current disappeared throughout the observed depth range (from 50 to 450 m) in the summer of 2011. Even at the deepest observed position, the monthly velocity anomalies reached 14 cm s-1 westward and 12 cm s-1 southward in the zonal and meridional directions, respectively. Both the Vietnam offshore current (VOC) and double gyres in the western SCS disappeared and the southern anticyclonic gyre expanded to strengthened the northward WBC in the summer of 2010. However, in summer of 2011, the VOC intensified, and the northern cyclonic gyre enlarged with its northern edge reaching 18°N, slightly north of mooring site, which weakened the northeastward WBC. The observed SCS circulation anomalies during 2010 and 2011 were mainly induced by the basin-scale wind field anomalies associated with the 2009/2010 El Niño and 2010/2011 La Niña.

  14. Surface circulation in the Iroise Sea (western Brittany) derived from high resolution current mapping by HF radars

    NASA Astrophysics Data System (ADS)

    Sentchev, Alexei; Forget, Philippe; Barbin, Yves; Marié, Louis; Ardhuin, Fabrice

    2010-05-01

    The use of high frequency radar (HFR) systems for near-real-time coastal ocean monitoring necessities that short time scale motions of the radar-derived velocities are better understood. While the ocean radar systems are able to describe coastal flow patterns with unprecedented details, the data they produce are often too sparse or gappy for applications such as the identification of coherent structures and fronts or understanding transport and mixing processes. In this study, we address two challenges. First, we report results from the HF radar system (WERA) which is routinely operating since 2006 on the western Brittany coast to monitor surface circulation in the Iroise Sea, over an area extending up to 100 km offshore. To obtain more reliable records of vector current fields at high space and time resolution, the Multiple Signal Classification (MUSIC) direction finding algorithm is employed in conjunction with the variational interpolation (2dVar) of radar-derived velocities. This provides surface current maps at 1 km spacing and time resolution of 20 min. Removing the influence of the sea state on radar-derived current measurements is discussed and performed on some data sequences. Second, we examine in deep continuous 2d velocity records for a number of periods, exploring the different modes of variability of surface currents in the region. Given the extent, duration, and resolution of surface current velocity measurements, new quantitative insights from various time series and spatial analysis on higher frequency kinematics will be discussed. By better characterizing the full spectrum of flow regimes that contribute to the surface currents and their shears, a more complete picture of the circulation in the Iroise Sea can be obtained.

  15. Sea-ice melt CO2-carbonate chemistry in the western Arctic Ocean: meltwater contributions to air-sea CO2 gas exchange, mixed layer properties and rates of net community production under sea ice

    NASA Astrophysics Data System (ADS)

    Bates, N. R.; Garley, R.; Frey, K. E.; Shake, K. L.; Mathis, J. T.

    2014-01-01

    The carbon dioxide (CO2)-carbonate chemistry of sea-ice melt and co-located, contemporaneous seawater has rarely been studied in sea ice covered oceans. Here, we describe the CO2-carbonate chemistry of sea-ice melt (both above sea ice as "melt ponds" and below sea ice as "interface waters") and mixed layer properties in the western Arctic Ocean in the early summer of 2010 and 2011. At nineteen stations, the salinity (~ 0.5 to < 6.5), dissolved inorganic carbon (DIC; ~ 20 to < 550 μmol kg-1) and total alkalinity (TA; ~ 30 to < 500 μmol kg-1) of above-ice melt pond water was low compared to water in the underlying mixed layer. The partial pressure of CO2 (pCO2) in these melt ponds was highly variable (~ < 10 to > 1500 μatm) with the majority of melt ponds acting as potentially strong sources of CO2 to the atmosphere. The pH of melt pond waters was also highly variable ranging from mildly acidic (6.1 to 7) to slightly more alkaline than underlying seawater (8 to 10.7). All of observed melt ponds had very low (< 0.1) saturation states (Ω) for calcium carbonate (CaCO3) minerals such as aragonite (Ωaragonite). Our data suggests that sea ice generated "alkaline" or "acidic" melt pond water. This melt-water chemistry dictates whether the ponds are sources of CO2 to the atmosphere or CO2 sinks. Below-ice interface water CO2-carbonate chemistry data also indicated substantial generation of alkalinity, presumably owing to dissolution of calcium CaCO3 in sea ice. The interface waters generally had lower pCO2 and higher pH/Ωaragonite than the co-located mixed layer beneath. Sea-ice melt thus contributed to the suppression of mixed layer pCO2 enhancing the surface ocean's capacity to uptake CO2 from the atmosphere. Meltwater contributions to changes in mixed-layer DIC were also used to estimate net community production rates (mean of 46.9 ±29.8 g C m-2 for the early-season period) under sea-ice cover. Although sea-ice melt is a transient seasonal feature, above-ice melt

  16. Holocene tropical western Indian Ocean sea surface temperatures in covariation with climatic changes in the Indonesian region

    NASA Astrophysics Data System (ADS)

    Kuhnert, Henning; Kuhlmann, Holger; Mohtadi, Mahyar; Meggers, Helge; Baumann, Karl-Heinz; Pätzold, Jürgen

    2014-05-01

    The sea surface temperature (SST) of the tropical Indian Ocean is a major component of global climate teleconnections. While the Holocene SST history is documented for regions affected by the Indian and Arabian monsoons, data from the near-equatorial western Indian Ocean are sparse. Reconstructing past zonal and meridional SST gradients requires additional information on past temperatures from the western boundary current region. We present a unique record of Holocene SST and thermocline depth variations in the tropical western Indian Ocean as documented in foraminiferal Mg/Ca ratios and δ18O from a sediment core off northern Tanzania. For Mg/Ca and thermocline δ18O, most variance is concentrated in the centennial to bicentennial periodicity band. On the millennial time scale, an early to mid-Holocene (~7.8-5.6 ka) warm phase is followed by a temperature drop by up to 2°C, leading to a mid-Holocene cool interval (5.6-4.2 ka). The shift is accompanied by an initial reduction in the difference between surface and thermocline foraminiferal δ18O, consistent with the thickening of the mixed layer and suggestions of a strengthened Walker circulation. However, we cannot confirm the expected enhanced zonal SST gradient, as the cooling of similar magnitude had previously been found in SSTs from the upwelling region off Sumatra and in Flores air temperatures. The SST pattern probably reflects the tropical Indian Ocean expression of a large-scale climate anomaly rather than a positive Indian Ocean Dipole-like mean state.

  17. Towards an Archaeology of Early Islamic Ports on the Western Red Sea Coast

    NASA Astrophysics Data System (ADS)

    Breen, Colin

    2013-12-01

    Against a background of developing research on Red Sea ports, a hypothetical model of the morphology of port towns during the early Islamic period is presented here. These places went through constant cycles of change as economic and political frameworks fluctuated. While their physical shape and form was strongly influenced by architectural features of the Islamic world their functionality was more aligned to commercial interaction. These were dynamic spaces where the daily life of their inhabitants was guided by trade, religion, weather and politics. The ports were intrinsically tied to the trade networks that connected Africa with Arabia and the broader Indian Ocean world.

  18. Multi-platform operational validation of the Western Mediterranean SOCIB forecasting system

    NASA Astrophysics Data System (ADS)

    Juza, Mélanie; Mourre, Baptiste; Renault, Lionel; Tintoré, Joaquin

    2014-05-01

    The development of science-based ocean forecasting systems at global, regional, and local scales can support a better management of the marine environment (maritime security, environmental and resources protection, maritime and commercial operations, tourism, ...). In this context, SOCIB (the Balearic Islands Coastal Observing and Forecasting System, www.socib.es) has developed an operational ocean forecasting system in the Western Mediterranean Sea (WMOP). WMOP uses a regional configuration of the Regional Ocean Modelling System (ROMS, Shchepetkin and McWilliams, 2005) nested in the larger scale Mediterranean Forecasting System (MFS) with a spatial resolution of 1.5-2km. WMOP aims at reproducing both the basin-scale ocean circulation and the mesoscale variability which is known to play a crucial role due to its strong interaction with the large scale circulation in this region. An operational validation system has been developed to systematically assess the model outputs at daily, monthly and seasonal time scales. Multi-platform observations are used for this validation, including satellite products (Sea Surface Temperature, Sea Level Anomaly), in situ measurements (from gliders, Argo floats, drifters and fixed moorings) and High-Frequency radar data. The validation procedures allow to monitor and certify the general realism of the daily production of the ocean forecasting system before its distribution to users. Additionally, different indicators (Sea Surface Temperature and Salinity, Eddy Kinetic Energy, Mixed Layer Depth, Heat Content, transports in key sections) are computed every day both at the basin-scale and in several sub-regions (Alboran Sea, Balearic Sea, Gulf of Lion). The daily forecasts, validation diagnostics and indicators from the operational model over the last months are available at www.socib.es.

  19. Maps Showing Sea Floor Topography, Sun-Illuminated Sea Floor Topography, and Backscatter Intensity of Quadrangles 1 and 2 in the Great South Channel Region, Western Georges Bank

    USGS Publications Warehouse

    Valentine, Page C.; Middleton, Tammie J.; Malczyk, Jeremy T.; Fuller, Sarah J.

    2002-01-01

    The Great South Channel separates the western part of Georges Bank from Nantucket Shoals and is a major conduit for the exchange of water between the Gulf of Maine to the north and the Atlantic Ocean to the south. Water depths range mostly between 65 and 80 m in the region. A minimum depth of 45 m occurs in the east-central part of the mapped area, and a maximum depth of 100 m occurs in the northwest corner. The channel region is characterized by strong tidal and storm currents that flow dominantly north and south. Major topographic features of the seabed were formed by glacial and postglacial processes. Ice containing rock debris moved from north to south, sculpting the region into a broad shallow depression and depositing sediment to form the irregular depressions and low gravelly mounds and ridges that are visible in parts of the mapped area. Many other smaller glacial featuresprobably have been eroded by waves and currents at worksince the time when the region, formerly exposed bylowered sea level or occupied by ice, was invaded by the sea. The low, irregular and somewhat lumpy fabric formed by the glacial deposits is obscured in places by drifting sand and by the linear, sharp fabric formed by modern sand features. Today, sand transported by the strong north-south-flowing tidal and storm currents has formed large, east-west-trending dunes. These bedforms (ranging between 5 and 20 m in height) contrast strongly with, and partly mask, the subdued topography of the older glacial features.

  20. PICASSSO Ps Receiver Function Analysis of the Lithospheric Structure Beneath the Western Mediterranean

    NASA Astrophysics Data System (ADS)

    Thurner, S.; Palomeras, I.; Levander, A.

    2011-12-01

    The western Mediterranean, consisting of the Betic Mountains in southern Spain, the Gibraltar Arc, the Alboran Sea, and the Rif and Atlas Mountains in northern Africa, has been affected by many different geodynamic processes throughout the Cenozoic. The ongoing collision between Africa and Iberia initiated ~60 Ma and resulted in crustal thickening. During this same time period (~30 Ma), slab rollback began in the Tethys Sea, causing significant extension. It is the juxtaposition of these coeval extensional and compressional regimes that has motivated numerous studies of the Mediterranean tectonic environment. Multiple geodynamic models, that include slab roll-back (Royden, 1993; Lonergan and White, 1997; Gutscher et al., 2002), accompanied and followed by lithospheric convective downwelling (Seber et al., 1996; Calvert et al., 2000), and delamination (Platt et al., 1996), have been invoked to explain the tectonics. It is hypothesized that a succession of small-scale convection processes initiated beneath the Alboran Sea ~20-25 Ma, and have continued most recently under the Atlas Mountains. PICASSO (Program to Investigate Convective Alboran Sea System Overturn) is a multi-disciplinary, international investigation seeking to improve our understanding of the geodynamics of the western Mediterranean, including the small-scale convection processes associated with slab rollback. We use Ps teleseismic receiver functions to investigate the crustal and lithospheric structure beneath the Atlas, Rif, and Betic Mountains. Data was collected from 33 earthquake events recorded between May 2009 and February 2011 at 83 PICASSO broadband seismic stations. 1 Hz receiver functions were calculated using both frequency domain and iterative deconvolution methods, and were CCP stacked to create a 3D image volume of the region. These results indicate crustal thicknesses between ~42-47 km in southern Spain beneath the Betic Mountains and ~35-45 km across the Gibraltar Arc. Beneath both the

  1. Rifting of the north-western South China Sea Basin from MCS images

    NASA Astrophysics Data System (ADS)

    Ranero, Cesar R.; Cameselle, Alejandra L.; Franke, Dieter; Barckhausen, Udo

    2014-05-01

    We have reprocessed about 2250 km of multichannel seismic reflection data collected during cruise Sonne 49 across the NW South China Sea. We present images across four regional lines that cross the outer continental shelf and slope, and extend into the deep-water basin. The seismic images are of high quality and show the crustal structure from clear base-of-the-crust reflections to continuous top-of-basement reflections and a well imaged syn-rift and post rift stratigraphy and intrusive magmatic layering. In addition, fault reflections in the basement are also common. The crystalline basement and sediment strata display a series of structures that change laterally from the continental shelf to the deep-water basin and that have been used to define a continental domain, an abrupt continent to ocean transition and an oceanic domain. Existing wide-angle data coincident with our lines support our interpretation. The style of continental extension, the structures defining the continent to ocean transition, and the distribution of oceanic crust in the basin has been used to propose a tectonic model of the formation of the NW South China Sea continental margin. The data document the three-dimensional temporal evolution of the interplay between rifting processes and seafloor spreading leading to the current structural configuration.

  2. Deep-sea scavenging amphipod assemblages from the submarine canyons of the Western Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Duffy, G. A.; Horton, T.; Billett, D. S. M.

    2012-11-01

    Submarine canyons have often been identified as hotspots of secondary production with the potential to house distinct faunal assemblages and idiosyncratic ecosystems. Within these deep-sea habitats, assemblages of scavenging fauna play a vital role in reintroducing organic matter from large food falls into the wider deep-sea food chain. Free-fall baited traps were set at different depths within three submarine canyons on the Iberian Margin. Amphipods from the traps were identified to species level and counted. Scavenging amphipod assemblages were compared at different depths within each canyon and between individual canyon systems. Using data from literature, abyssal plain assemblages were compared to submarine canyon assemblages. Samples from canyons were found to contain common abyssal plain species but in greater than expected abundances. It is proposed that this is a result of the high organic carbon input into canyon systems owing to their interception of sediment from the continental shelf and input from associated estuarine systems. Community composition differed significantly between the submarine canyons and abyssal plains. The cause of this difference cannot be attributed to one environmental variable due to the numerous inherent differences between canyons and abyssal plains.

  3. Holocene climate variability in the North-Western Mediterranean Sea (Gulf of Lions)

    NASA Astrophysics Data System (ADS)

    Jalali, B.; Sicre, M.-A.; Bassetti, M.-A.; Kallel, N.

    2016-01-01

    Sea surface temperatures (SSTs) and land-derived input time series were generated from the Gulf of Lions inner-shelf sediments (NW Mediterranean Sea) using alkenones and high-molecular-weight odd-carbon numbered n-alkanes (TERR-alkanes), respectively. The SST record depicts three main phases: a warm Early Holocene ( ˜ 18 ± 0.4 °C) followed by a cooling of ˜ 3 °C between 7000 and 1000 BP, and rapid warming from ˜ 1850 AD onwards. Several superimposed multi-decadal to centennial-scale cold events of ˜ 1 °C amplitude were also identified. TERR-alkanes were quantified in the same sedimentary horizons to identify periods of high Rhone River discharge and compare them with regional flood reconstructions. Concentrations show a broad increase from the Early Holocene towards the present with a pronounced minimum around 2500 BP and large fluctuations during the Late Holocene. Comparison with Holocene flood activity reconstructions across the Alps region suggests that sediments of the inner shelf originate mainly from the Upper Rhone River catchment basin and that they are primarily delivered during positive North Atlantic Oscillation (NAO).

  4. Holocene climate variability in the North-Western Mediterranean Sea (Gulf of Lions)

    NASA Astrophysics Data System (ADS)

    Jalali, B.; Sicre, M.-A.; Bassetti, M.-A.; Kallel, N.

    2015-07-01

    Sea surface temperatures (SSTs) and land-derived input time series were generated from the Gulf of Lions inner-shelf sediments (NW Mediterranean Sea) using alkenones and high-molecular-weight odd-carbon numbered n-alkanes (TERR-alkanes), respectively. The SST record depicts three main phases: a warm Early Holocene (∼ 18 ± 0.4 °C) followed by a cooling of ∼ 3 °C (from 7000 to 1000 BP) and rapid warming from ∼ 1850 AD onwards. Several superimposed multi-decadal cooling events of ∼ 1 °C amplitude were also identified. TERR-alkanes were also quantified to identify periods of high river discharge in relation with flood events of the Rhone River and precipitations. Their concentrations show a broad increase from the early Holocene towards present with a pronounced minimum around 2500 BP and large fluctuations during the second part of the Holocene. Comparison with Holocene flood activity reconstructions across the Alps region suggests that sediments of the inner shelf originate mainly from the Upper Rhone River catchment basin and that they are primarily delivered during positive NAO.

  5. Recent trends of SST in the Western Mediterranean basins from AVHRR Pathfinder data (1985-2007)

    NASA Astrophysics Data System (ADS)

    López García, M. J.; Camarasa Belmonte, A. M.

    2011-08-01

    Climate change in the Mediterranean region cannot be understood without taking into account changes in the Mediterranean Sea, which is an important source of moisture and heat for the Mediterranean climate system. Many research papers have been published in the last two decades increasing our knowledge about long-term trends and inter-annual variability of temperature and salinity in the Western Mediterranean. Although recent changes have been better documented, there remain uncertainties because different results are obtained depending on the period of time analyzed or the geographic region selected. This paper analyses the regional, seasonal and decadal variability of sea surface temperature in the Western Mediterranean basins (Northern (Ligurian Sea and Gulf of Lions), Balearic, Algerian and Alboran) by means of thermal satellite images. Monthly data from the PO.DAAC (Physical Oceanography Distributed Active Archive Center) have been processed for the period 1985-2007. Results show an averaged warming linear trend of 0.03 °C/yr. This rate is higher during the spring (0.06 °C/yr) in all the basins and the highest values were registered in the Northern basin in June. The study suggests that an early warming of the Sea is occurring in all the basins during the spring, with an increment of 0.5-1 °C in the mean SST of April, May and June over the two decades studied. The analysis of thermal anomalies confirms the warming trend with a dominance of negative anomalies during 1985-1996 and a dominance of positive anomalies during the last decade (1997-2007). Intense anomalies are more frequent in the Northern basin.

  6. Development from the seafloor to the sea surface of the cabled NEMO-SN1 observatory in the Western Ionian Sea

    NASA Astrophysics Data System (ADS)

    Sparnocchia, Stefania; Beranzoli, Laura; Borghini, Mireno; Durante, Sara; Favali, Paolo; Giovanetti, Gabriele; Italiano, Francesco; Marinaro, Giuditta; Meccia, Virna; Papaleo, Riccardo; Riccobene, Giorgio; Schroeder, Katrin

    2015-04-01

    A prototype of cabled deep-sea observatory has been operating in real-time since 2005 in Southern Italy (East Sicily, 37°30' N - 15°06'E), at 2100 m water depth, 25 km from the harbor of the city of Catania. It is the first-established real-time node of the "European Multidisciplinary Seafloor and water column Observatory" (EMSO, http://www.emso-eu.org) a research infrastructure of the Sector Environment of ESFRI. In the present configuration it consists of two components: the multi-parametric station NEMO-SN1 (TSN branch) equipped with geophysical and environmental sensors for measurements at the seafloor, and the NEMO-OνDE station (TSS branch) equipped with 4 wideband hydrophones. A 28 km long electro-optical cable connects the observatory to a shore laboratory in the Catania harbor, hosting the data acquisition system and supplying power and data transmission to the underwater instrumentation. The NEMO-SN1 observatory is located in an area particularly suited to multidisciplinary studies. The site is one of the most seismically active areas of the Mediterranean (some of the strongest earthquakes occurred in 1169, 1693 and 1908, also causing very intense tsunami waves) and is close to Mount Etna, one of the largest and most active volcanoes in Europe. The deployment area is also a key site for monitoring deep-water dynamics in the Ionian Sea, connecting the Levantine basin to the southern Adriatic basin where intermediate and deep waters are formed, and finally to the western Mediterranean Sea via the Strait of Sicily. The observatory is being further developed under EMSO MedIT (http://www.emso-medit.it/en/), a structural enhancement project contributing to the consolidation and enhancement of the European research infrastructure EMSO in Italian Convergence Regions. In this framework, a new Junction Box will be connected to the TSN branch and will provide wired and wireless (acoustic connections) for seafloor platforms and moorings. This will allow the

  7. Combined use of glider, radar and altimetry data to study a coastal current in the western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Troupin, Charles; Pascual, Ananda; Lana, Arancha; Valladeau, Guillaume; Pujol, Isabelle; Tintoré, Joaquin

    2014-05-01

    The Mediterranean Sea is characterized by a small Rossby radius of deformation, hence small structures and eddies. The Ibiza Channel, located in the Balearic Sea, is of particular importance since it controls the exchanges in the western Mediterranean Sea. In order to understand and describe the upper ocean dynamics, a multi-sensor/integrated approach was applied in the Ibiza Channel in the first days of August 2013 during the G-AltiKa mission. This approach combines: Sea-level anomaly (SLA) measurements from Saral-AltiKa track no. 16, which passed west of Ibiza island. 1-Hz and 40-Hz data were considered. Glider data obtained along the satellite track a few hours after its passage. The horizontal resolution ranges from 5 km offshore to about 1 km in the coastal area. HF radar hourly velocities on a 3 km-resolution grid that partially covers the study region (range up to 74 km offshore). Dynamic height (DH) was derived from the glider temperature and salinity profiles, while Absolute Dynamic Topography (ADT) was obtained by combining SLA and the new Mean Dynamic Topography (MDT) jointly produced by CLS and SOCIB. From DH and SLA, the cross-track velocities were derived using geostrophy relations. Different filters were applied on SLA data and different reference levels were tested for the DH computation. DH and ADT both displayed very weak variations, on the order of 2-3 cm, along the glider trajectory. The glider- and the altimetry-derived velocities exhibit the signal of a meander centered at 38.65°N and a narrow coastal current flowing northward a few kilometers off Ibiza. These computed velocities are on the order of 20 cm/s, as confirmed by the HF radar. The time separation between the passage of the satellite and the glider can explain the discrepancies observed between the two platforms. Our results highlight the promising measurements offered by SARAL/AltiKa in the coastal band. In particular, the satellite was able is able to capture the northern edge of

  8. Geochemical assessment of hydrocarbon migration phenomena: Case studies from the south-western margin of the Dead Sea Basin

    NASA Astrophysics Data System (ADS)

    Sokol, Ella; Kozmenko, Olga; Smirnov, Sergey; Sokol, Ivan; Novikova, Sofya; Tomilenko, Anatoliy; Kokh, Svetlana; Ryazanova, Tatyana; Reutsky, Vadim; Bul'bak, Taras; Vapnik, Yevgeny; Deyak, Michail

    2014-10-01

    Calcite veins with fluid and solid bitumen inclusions have been discovered in the south-western shoulder of the Dead Sea rift within the Masada-Zohar block, where hydrocarbons exist in small commercial gas fields and non-commercial fields of heavy and light oils. The gas-liquid inclusions in calcite are dominated either by methane or CO2, and aqueous inclusions sometimes bear minor dissolved hydrocarbons. The enclosed flake-like solid bitumen matter is a residue of degraded oil, which may be interpreted as “dead carbon”. About 2/3 of this matter is soot-like amorphous carbon and 1/3 consists of n-C8sbnd C18 carboxylic acids and traces of n-alkanes, light dicarboxylic acids, and higher molecular weight (>C20) branched and/or cyclic carboxylic acids. Both bitumen and the host calcites show genetic relationship with mature Maastrichtian chalky source rocks (MCSRs) evident in isotopic compositions (δ13C, δ34S, and δ18O) and in REE + Y patterns. The bitumen precursor may have been heavy sulfur-rich oil which was generated during the burial compaction of the MCSR strata within the subsided blocks of the Dead Sea graben. The δ18O and δ13C values and REE + Y signatures in calcites indicate mixing of deep buried fluids equilibrated with post-mature sediments and meteoric waters. The temperatures of fluid generation according to Mg-Li-geothermometer data range from 55 °С to 90 °С corresponding to the 2.5-4.0 km depths, and largely overlap with the oil window range (60-90 °С) in the Dead Sea rift (Hunt, 1996; Gvirtzman and Stanislavsky, 2000; Buryakovsky et al., 2005). The bitumen-rich vein calcites originated in the course of Late Cenozoic rifting and related deformation, when tectonic stress triggers damaged small hydrocarbon reservoirs in the area, produced pathways, and caused hydrocarbon-bearing fluids to rise to the subsurface; the fluids filled open fractures and crystallized to calcite with entrapped bitumen. The reported results are in good agreement

  9. How dangerous are slope failures offshore western Thailand (Andaman Sea, Indian Ocean)?

    NASA Astrophysics Data System (ADS)

    Schwab, J.; Krastel, S.; Grün, M.; Gross, F.; Pananont, P.; Jintasaeranee, P.; Bunsomboonsakul, S.; Weinrebe, W.; Winkelmann, D.

    2012-12-01

    The Thai west coast is well known for being hit by tsunami waves triggered by earthquakes arising from the nearby Sunda Trench. However, so far little has been known about additional factors that may trigger tsunamis in the area, such as submarine landslides at the shelf slope area. In order to assess the stability of the slope and evaluate the tsunamigenic potential of submarine landslides off western Thailand, 2D seismic data from the top and the western slope of a bathymetric high (Mergui Ridge about 200 km off the Thai west coast) have been investigated. These data were the basis for mapping locations and approximate volumes of mass transport deposits (MTDs). In total, 17 mass transport deposits were found. The estimated minimum volumes of individual MTDs range between 0.3 cbkm and 14 cbkm. MTDs have been identified in three different settings: i) stacked MTDs within disturbed and faulted basin sediments at the transition of the Mergui Ridge to the adjacent East Andaman Basin, ii) MTDs within a pile of drift sediments at the basin-ridge transition, and iii) MTDs near the edge of/on top of Mergui Ridge in relatively shallow water depths (<1000m). Our data indicate that the Mergui Ridge-slope area seems to have been generally unstable. Slide events occurred repeatedly and slope failures may occur again in the future. We find that the most likely causes for slope instabilities are the presence of unstable drift sediments, excess pore pressure in the sediments, and active tectonics. Most MTDs are located in large water depths (> 1000 m) and/or comprise small volumes; hence it is very unlikely that they triggered significant tsunamis in the past. Moreover, the recurrence rates of failure events seem to be low. Some MTDs with tsunami potential, however, have been identified on top of Mergui Ridge in water depths below 1000 m. Mass-wasting events that may occur in the future at similar locations do have a tsunami potential if they comprise sufficient volumes

  10. New geological estimates of Pliocene sea levels from the Western and Northern Cape Provinces, Republic of South Africa

    NASA Astrophysics Data System (ADS)

    Hearty, P. J.; O'Leary, M.; Raymo, M. E.; Rovere, A.; Inglis, J.; Roberts, D.; Bergh, E.

    2012-12-01

    The mid-late Pliocene warm period (MPWP) is the most recent geologic interval when global atmospheric CO2 reached ~400 ppmv. The MPWP is of great interest to paleoclimatologists and modelers because accurate geological data would help to explain the behavior of sea level (SL) and ice sheets in a past warmer climates. Our modern industrial Earth is rapidly approaching this ominous benchmark (395.77 ppmv 6/2012). The trailing continental margin and far-field sites of western and southern Republic of South Africa (RSA) yield abundant coastal imprints of Miocene to Pleistocene seastands. Existing literature identifies zone fossils, and a few unpublished Sr-isotope ages that correlate these shoreline deposits with Pliocene highstands. Younger Pleistocene SL benchmarks provide indications of the regional tectonic stability, with MIS 5e (125 ka) deposits widely correlated along RSA coasts at about +3 m asl. Precise elevations of geomorphic, sedimentary, and biological SL indicators were measured in Western and Northern Cape Provinces of RSA with decimeter accuracy using an OmniStar differential GPS. High-resolution SL indicators (within 0.5 m of paleo-SL) include abrasion platforms (Fig 1), marine terraces, sub-, inter-, and supratidal sedimentary structures, and in situ marine invertebrates such as shallow water oysters and intertidal barnacles. The coastal geomorphic expression of the MPWP is profound. For more than 0.5 Ma, we hypothesize that high frequency (20-40 ka), low amplitude oscillations of Pliocene SL acted as a shoreline "buzz saw", laterally incising older bedrock, forming extensive planation surfaces along the coastline. We propose these broad geomorphic features are diagnostic of this prolonged interval of low amplitude but consistent SL along relatively stable, non-sediment-dominated coastlines of the world. Although currently uncorrected for post-depositional effects including GIA and dynamic topography, our PLIOMAX team (www.pliomax.org) has documented

  11. Resonant Third-Degree Diurnal Tides in the Seas Off Western Europe

    NASA Technical Reports Server (NTRS)

    Ray, Richard D.; Smith, David E. (Technical Monitor)

    2000-01-01

    Third-degree diurnal tides are estimated from long time series of sea level measurements at three North Atlantic tide gauges. Although their amplitudes are only a few mm or less, their admittances are far larger than those of second-degree diurnal tides, just as Cartwright discovered for the M(sub 1) constituent. The tides are evidently resonantly enhanced owing to high spatial correlation between the third-degree spherical harmonic of the tidal potential and a near-diurnal oceanic normal mode that is most pronounced in the North Atlantic. By estimating the ocean tidal response across the diurnal band (5 tidal constituents plus nodal modulations), the period and Q of this mode and one nearby mode are estimated.

  12. Episodic rifting of phanerozoic rocks in the victoria land basin, Western ross sea, antarctica.

    PubMed

    Cooper, A K; Davey, F J

    1985-09-13

    Multichannel seismic-reflection data show that the Victoria Land-basin, unlike other sedimentary basins in the Ross Sea, includes a rift-depression 15 to 25 kilometers wide that parallels the Transantarctic Mountains and contains up to 12 kilometers of possible Paleozoic to Holocene age sedimentary rocks. An unconformity separates the previously identified Cenozoic sedimentary section from the underlying strata of possible Mesozoic and Paleozoic age. Late Cenozoic volcanic rocks intrude into the entire section along the eastern flank of the basin. The Victoria Land basin is probably part of a more extensive rift system that has been active episodically since Paleozoic time. Inferred rifting and basin subsidence during Mesozoic and Cenozoic time may be associated with regional crustal extension and uplift of the nearby Transantarctic Mountains. PMID:17753283

  13. Episodic rifting of phanerozoic rocks in the Victoria Land basin, Western Ross Sea, Antarctica

    USGS Publications Warehouse

    Cooper, A. K.; Davey, F.J.

    1985-01-01

    Multichannel seismic-reflection data show that the Victoria Land basin, unlike other sedimentary basins in the Ross Sea, includes a rift-depression 15 to 25 kilometers wide that parallels the Transantarctic Mountains and contains up to 12 kilometers of possible Paleozoic to Holocene age sedimentary rocks. An unconformity separates the previously identified Cenozoic sedimentary section from the underlying strata of possible Mesozoic and Paleozoic age. Late Cenozoic volcanic rocks intrude into the entire section along the eastern flank of the basin. The Victoria Land basin is probably part of a more extensive rift system that has been active episodically since Paleozoic time. Inferred rifting and basin subsidence during Mesozoic and Cenozoic time may be associated with regional crustal extension and uplift of the nearby Transantarctic Mountains.

  14. Lead in the western South China Sea: Evidence of atmospheric deposition and upwelling

    NASA Astrophysics Data System (ADS)

    Chen, Mengli; Goodkin, Nathalie F.; Boyle, Edward A.; Switzer, Adam D.; Bolton, Annette

    2016-05-01

    In recent decades, rapid industrial developments have increased lead (Pb) inputs to the South China Sea. To quantify the increasing variability, we investigated 170 years of skeletal Pb and Pb isotopes from an offshore, central Vietnamese coral. The Pb/Ca in the coral was 10-16 nmol/mol before the mid-1950s and increased to more than 30 nmol/mol by 2000. While the regional phaseout of leaded petrol commenced in 2000, coral Pb/Ca continued increasing until 2004, possibly due to regional upwelling and the transport of previously emitted Pb from tropical Pacific waters. The 206Pb/207Pb ratio in the coral was 1.191-1.195 before mid-1950s, suggesting natural sources. Since then, the ratio decreased, reaching ~1.165 in 2004. Lead isotopes show high linearity between natural and Chinese emitted Pb, with the latter contributing ~40%~60% of the skeletal Pb after 2000.

  15. Sedimentological, biogeochemical and mineralogical facies of Northern and Central Western Adriatic Sea

    NASA Astrophysics Data System (ADS)

    Spagnoli, Federico; Dinelli, Enrico; Giordano, Patrizia; Marcaccio, Marco; Zaffagnini, Fabio; Frascari, Franca

    2014-11-01

    The aim of this work was to identify sedimentary facies, i.e. facies having similar biogeochemical, mineralogical and sedimentological properties, in present and recent fine sediments of the Northern and Central Adriatic Sea with their spatial and temporal variations. Further aims were to identify the transportation, dispersion and sedimentation processes and provenance areas of sediments belonging to the facies. A Q-mode factor analysis of mineralogical, granulometric, geochemical (major and trace elements) and biochemical (organic carbon and total nitrogen) properties of surficial and sub-surficial sediments sampled in the PRISMA 1 Project has been used to identify the sedimentary facies. On the whole, four facies were identified: 1) Padanic Facies, made up of fine siliciclastic sediments which reach the Adriatic Sea mainly from the Po River and are distributed by the Adriatic hydrodynamic in a parallel belt off the Italian coast. Southward, this facies gradually mixes with sediments from the Apennine rivers and with biogenic autochthonous particulate; 2) Dolomitic Facies, made up of dolomitic sediments coming from the eastern Alps. This facies is predominant north of the Po River outfalls and it mixes with Padanic Facies sediments in front of the Po River delta; 3) Mn-carbonate Facies, made up of very fine sediments, rich in coccolithophores and secondary Mn-oxy-hydroxides resulting from the reworking of surficial fine sediments in shallow areas and subsequent deposition in deeper areas; 4) Residual Facies, made up of coarse siliciclastic sediments and heavy minerals resulting from the action of waves and coastal currents; this facies is present mainly in inshore areas. The zoning of the facies, resulting from this study, will make possible the identification, through further investigation, on a greater scale, of more accurate facies borders and the recognition of sub-facies, resulting from secondary or weaker biogeochemical processes.

  16. Soils of sea terraces and bedrock slopes of fiords in Western Spitsbergen

    NASA Astrophysics Data System (ADS)

    Pereverzev, V. N.; Litvinova, T. I.

    2010-03-01

    The genetic characteristics of soils on the main geomorphic elements of Western Spitsbergen are compared with those of soils on similar rocks of the Kola Peninsula. Soils of the same type—gray-humus (soddy) soils with an O-AY-C profile—are developed from the rocks of different geneses and textures. These soils have a weakly differentiated profile. The accumulation of humus takes place under the litter horizon, and the soddy gray-humus (AY) horizon is formed. It has a diffuse boundary with the C horizon. The analytical data indicate that the bulk contents of iron and aluminum, as well as the contents of their oxalatesoluble compounds, are similar in the soils developed in different geomorphic positions and from different rocks. In all the soils, the bulk elemental composition and the oxalate-soluble sesquioxides are not differentiated in the profiles.

  17. Ophiolites of the deep-sea trenches of the western Pacific

    SciTech Connect

    Chudaev, O.

    1990-06-01

    Igneous and metamorphic rocks of ophiolites are widespread in the basement of the Izu-Bonin, Volcano, Mariana, Philippine, Yap, Palau, New Hebrides, West Melanesian, Tonga, and Mussau trenches. Ophiolite in the trenches includes (1) metamorphic rocks ranging from low-T and low P to high-T and moderate P; (2) serpentinites after harzburgite; (3) ultramafic-mafic layered series; (4) tholeiitic basalts, dolerites, and their metamorphosed varieties; and (5) rocks of the boninitic series. Two geodynamic stages could be distinguished in the formation of the ophiolites of the Western Pacific. At the rifting stage, mantle diapir ascended during rifting and magmatic series were formed. In this period, rocks underwent intense low-temperature metasomatic alterations in the zones of heated seawater circulation. At the compression stage (subduction zone) regional pressure metamorphism of the ophiolites superimposed on the low-temperature metasomatic processes.

  18. Dynamic Modeling of Back-arc Extension in the Aegean Sea and Western Anatolia

    NASA Astrophysics Data System (ADS)

    Mazlum, Ziya; Göğüş, Oğuz H.; Sözbilir, Hasan; Karabulut, Hayrullah; Pysklywec, Russell N.

    2015-04-01

    Western Anatolian-Aegean regions are characterized by large-scale lithospheric thinning and extensional deformation. While many geological observations suggest the formation of rift basins, normal faulting, exhumation of metamorphic rocks, and back-arc volcanism, the primary cause and the geodynamic driving mechanisms for the lithospheric thinning and extension are not well understood. Previous studies suggest three primary geodynamic hypotheses to address the extension in the Aegean-west Anatolia: 1) Slab retreat/roll-back model, inferred by the southward younging magmatism and metamorphic exhumations; 2) Gravitational collapse of the overthickened (post orogenic) lithosphere, interpreted by the structural studies that suggests tectonic mode switching from contraction to extension; 3) Lateral extrusion (escape tectonics) associated with the continental collision in East Anatolia. We use 2-D thermo-mechanical numerical subduction experiments to investigate how subduction retreat and related back-arc basin opening are controlled by a) changing length and thickness of the subducting plate, b) the dip angle of the subducting slab and c) various thickness and thermal properties of the back-arc lithosphere. Subsequently, we explore the surface response to the subduction retreat model in conjunction with the gravitational (orogenic) collapse in the presumed back-arc region. Quantitative model predictions (e.g., crustal thickness, extension rate) are tested against a wide range of available geological and geophysical observations from the Aegean and west Anatolia regions and these results are reconciled with regional tectonic observations. Our model results are interpreted in the context of different surface response in the extensional regime (back-arc) for the Aegean and western Anatolia, where these two regions have been presumably segmented by the right lateral transfer fault system (Izmir-Balıkesir transfer zone).

  19. Seasonal hypoxia in eutrophic stratified coastal shelves: mechanisms, sensibilities and interannual variability from the North-Western Black Sea case

    NASA Astrophysics Data System (ADS)

    Capet, A.; Beckers, J.-M.; Grégoire, M.

    2012-12-01

    The Black Sea north-western shelf (NWS) is a~shallow eutrophic area in which seasonal stratification of the water column isolates bottom waters from the atmosphere and prevents ventilation to compensate for the large consumption of oxygen, due to respiration in the bottom waters and in the sediments. A 3-D coupled physical biogeochemical model is used to investigate the dynamics of bottom hypoxia in the Black Sea NWS at different temporal scales from seasonal to interannual (1981-2009) and to differentiate the driving factors (climatic versus eutrophication) of hypoxic conditions in bottom waters. Model skills are evaluated by comparison with 14 500 in-situ oxygen measurements available in the NOAA World Ocean Database and the Black Sea Commission data. The choice of skill metrics and data subselections orientate the validation procedure towards specific aspects of the oxygen dynamics, and prove the model's ability to resolve the seasonal cycle and interannual variability of oxygen concentration as well as the spatial location of the oxygen depleted waters and the specific threshold of hypoxia. During the period 1981-2009, each year exhibits seasonal bottom hypoxia at the end of summer. This phenomenon essentially covers the northern part of the NWS, receiving large inputs of nutrients from the Danube, Dniestr and Dniepr rivers, and extends, during the years of severe hypoxia, towards the Romanian Bay of Constanta. In order to explain the interannual variability of bottom hypoxia and to disentangle its drivers, a statistical model (multiple linear regression) is proposed using the long time series of model results as input variables. This statistical model gives a general relationship that links the intensity of hypoxia to eutrophication and climate related variables. The use of four predictors allows to reproduce 78% of hypoxia interannual variability: the annual nitrate discharge (N), the sea surface temperature in the month preceding stratification (T), the

  20. Dissolved organic carbon in the South China Sea and its exchange with the Western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Wu, Kai; Dai, Minhan; Chen, Junhui; Meng, Feifei; Li, Xiaolin; Liu, Zhiyu; Du, Chuanjun; Gan, Jianping

    2015-12-01

    Based on a large and high quality dataset of total organic carbon (TOC, an approximation of dissolved organic carbon) collected from three cruises in spring, fall and winter in 2009-2011, we examined the distribution of TOC and its seasonality in the oligotrophic regime of the Northern South China Sea (NSCS) as well as its exchanges with the West Philippine Sea (WPS) in the Northwest Pacific Ocean through the Luzon Strait, the only deep channel linking the South China Sea (SCS) and the Pacific Ocean. Surface TOC concentration in the slope and basin areas of the NSCS varied from 65 to 75 μmol L-1 with relatively high values in the northeast part (southwest of Taiwan Island) in spring, and in the eastern parts of the NSCS during fall and winter. The TOC inventory in the upper 100 m of the water column ranged from 6.0-7.5 mol m-2 with a similar distribution pattern as the surface TOC concentration. There were two most significant differences in the TOC profiles between the SCS and the WPS. One was in the upper 200 m, where more TOC was accumulated in the WPS; the other was in the intermediate layer at ~1000-1500 m, where the gradient of TOC concentration was still persistent below 1000 m in the SCS, a feature which did not exist in the WPS. At this intermediate layer, there also appeared an excess of TOC in the SCS as compared with that in the WPS. The TOC concentration below 2000 m in the SCS was identical to that in the Northwestern Pacific, both of which were ~40 μmol L-1 without significant difference among stations and seasons, suggesting that this deep water TOC was homogeneously distributed in the deep SCS basin owing to the fast replenishment of the deep water from the WPS. We adopted an isopycnal mixing model to derive the water proportion contributed respectively from the SCS and Kuroshio along individual isopycnal plane and examined the impact of the Kuroshio intrusion on the TOC in the NSCS. The upper 100 m TOC inventory in the NSCS was overall

  1. A sharp Moho step under Central and Eastern Betics, Western Mediterranean region

    NASA Astrophysics Data System (ADS)

    de Lis Mancilla, Flor; Aguilera-Molina, Antonio; Heit, Benjamin; Morales, Jose; Yuan, Xiaohui; Stich, Daniel; Martin, Rosa

    2016-04-01

    Previous geophysical studies in the northern limit of the western Mediterranean region have showed that the Iberian crust understrusts the Alboran domain under its contact with the External zones. They observe the presence of slab-type feature of Iberian lithosphere at the western Betics and interpret tearing and delamination of this Iberian slab at central and eastern Betics. To map the variations of the lithospheric structure between the different geological domains under central and eastern Betics, we deploy two dense seismic profiles (~120 and ~160 km length). The spacing between stations, around 2-3 km, allows mapping with high accuracy variations of the crustal structure. By interpreting P-receiver functions, we observe sharp Moho steps of ~15-17 km underneath the Internal zones (Alboran domain) at both profiles. The images suggest that the Iberian crust undertrusts the more deformed Alboran crust and terminates sharply under the contact between the Alpujarride and the Nevado-Filabre complexes (Alboran domain). The thickness of the Iberian crust near the edge, ~17 km, and its position along the contact suggest that the breaking of the Iberian slab occurs in the transitional crust of the Iberian Paleomargin.

  2. Seawater-derived neodymium isotope records in the Chukchi Sea, western Arctic Ocean during Holocene: implications for oceanographic circulation

    NASA Astrophysics Data System (ADS)

    Lee, Borom; Nam, Seung-Il; Huh, Youngsook; Lee, Mi Jung

    2015-04-01

    Changes in oceanographic circulation in the Artic have a large influence on the global oceanic and climate system of the Earth through the geological times. In particular, freshwater input from the North Pacific to the western Arctic Ocean affects the Atlantic meridional overturning circulation (AMOC) after the opening of the Bering Strait. Seawater-derived neodymium isotope in marine sediments has been used as a proxy to trace the origin of water masses and oceanic circulation system. The global average residence time of Nd is shorter than the global ocean mixing time and dissolved Nd in seawater behaves quasi-conservatively. In the modern Arctic Ocean, the Nd isotope distribution is dominated by Atlantic source water, although the circum-Arctic riverine discharge and Pacific-derived waters also have noticeable impacts. In this study, we investigated seawater-derived neodymium isotope records from a sediment core recovered from the Chukchi Sea to understand the changes in hydrograhic circulation of the western Arctic during the Holocene. A gravity core, ARA02B 01A, was collected on the northern shelf of the Chukchi Sea (73°37.8939'N, 166°30.9838'W, ca. 111 m in water depth) during the RV Araon expedition in 2011. To obtain seawater-derived Nd records, we extracted Fe-Mn oxide coatings as an authigenic fraction from bulk sediments by leaching with acid-reducing solution after removing carbonate by leaching with acetic acid. Our preliminary results might show a general pattern of increasing radiogenic ɛNd values through Holocene intervals. Therefore, it implies that ɛNd results may be related with variations in the intensity of Bering Strait inflow during the last ~9.31 ka BP. The radiogenic trend was strongly pronounced from the late Holocene (ɛNd -7.23; ca. 8.84 ka BP) to the middle Holocene (ɛNd -4.78; ca. 6.18 ka BP) and vaguely during the middle Holocene. After 4.13 ka BP, ɛNd values were increased again from -4.86 to -4.03 at 0.57 ka BP. But 87Sr/86Sr

  3. Land-sea correlation between Late Holocene coastal and infralittoral deposits in the SE Iberian Peninsula (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Fernández-Salas, L. M.; Dabrio, C. J.; Goy, J. L.; Díaz del Río, V.; Zazo, C.; Lobo, F. J.; Sanz, J. L.; Lario, J.

    2009-03-01

    The well-exposed systems of prograding beach ridges on the Carchuna-Calahonda (Granada) and Campo de Dalías-Roquetas (Almería) coastal plains continue offshore as infralittoral prograding wedges (IPW). The Holocene IPW is a narrow morpho-sedimentary unit up to 2.5 km wide which develops seaward from the lower edge of the shoreface to 15-20 m depth, extending to a well-defined break of slope at water depths of 35-40 m. These IPWs have been recognized and studied using very high-resolution seismic profiles (TOPAS) and multibeam data (EM-3000D). In detail they are complex morpho-sedimentary units in which internal structures are closely linked to the pattern of progradation of the adjacent coastal plains. When longshore currents produce significant littoral drift, the IPWs are composed of several minor units arranged in offlap, which accrete parallel or oblique to the main shoreline. Therefore, it is possible to correlate progradational units in the coastal plain (H-units, sensu[Goy, J.L., Zazo, C., Dabrio, C.J., 2003. A beach-ridge progradation complex reflecting periodical sea-level and climate variability during the Holocene (Gulf of Almería, Western Mediterranean). Geomorphology 50, 251-268]) and subunits in the IPW, but special care is required depending on the local arrangement of morpho-sedimentary units. Besides, it is not realistic to draw conclusions regarding the age of the subunits inside a given IPW without adequate dating, as the number of subunits will greatly vary from place to place depending on local factors, magnitude of sea-level oscillations, and sediment supply.

  4. Seasonal suspended particles distribution patterns in Western South Yellow Sea based on Acoustic Doppler Current Profiler observation

    NASA Astrophysics Data System (ADS)

    Li, Jianchao; Li, Guangxue; Xu, Jishang; Qiao, Lulu; Dong, Ping; Ding, Dong; Liu, Shidong; Sun, Pingkuo

    2015-06-01

    An Acoustic Doppler Current Profiler (ADCP) observation site was set up in the Western South Yellow Sea from 2012 to 2013 to study the local suspended particle matters (SPM) distribution pattern. The SPM concentration could be semi-quantitatively represented by backscatter intensity (Sv), converted by the echo intensity (EI) of ADCP. Results show two types of SPM in the water column: the quasi-biological SPM and quasi-mineral SPM. The quasi-biological SPM mainly exists in summer half year and is concentrated above the thermocline. It has periodically diurnal variations with high concentration at night and low concentration in the daytime. The quasi-mineral SPM is located in lower part of the water column, with similar relation to monthly tidal current variation all year round. However, the daily quasi-mineral SPM distribution patterns vary between summer and winter half year. The sunlight is thought to be the origin factor leading to the diurnally vertical motion of the biological features, which might cause the diurnal Sv variation. Unlike in winter half year when tidal current is relatively single driving force of the monthly SPM pattern, the high speed current near the thermocline is also responsible for the concentration of quasi-mineral SPM in summer half year. The sediment input difference between summer and winter half year contribute to the varied daily variation of quasi-mineral SPM with re-suspended SPM in winter and sediments from Yellow Sea Mud Area (YSMA) in summer. The seasonal variations in hydrodynamics, water structure and heavy-wind incidents are the primary factors influencing the differential seasonal SPM distribution patterns.

  5. Time variability of the north-western Mediterranean Sea pH over 1995-2011.

    PubMed

    Marcellin Yao, Koffi; Marcou, Olivier; Goyet, Catherine; Guglielmi, Véronique; Touratier, Franck; Savy, Jean-Philippe

    2016-05-01

    Factors controlling ocean acidification and its temporal variations were studied over the 1995-2011 period at the Dyfamed site at 10 m depth, in the North Mediterranean Sea. The results indicated a mean annual decrease of 0.003 ± 0.001 pH units on the seawater scale. The seasonal variability was characterized by a pH decrease during springtime and a strong pH increase in late fall. Anthropogenic CO2 (CANT) absorption by the ocean was the key driver of seawater acidification in this region, accounting for about 70% of the observed drop in pH, followed by water temperature (about 30%). The total inorganic carbon (CT) data showed a CT increase of 30.0 ± 1.0 μmol kg(-1) per decade. This decadal increase is mainly due to the CANT penetration (43.2 μmol kg(-1) per decade) in surface waters, which is mitigated for by relatively small opposing changes in CT due to physical and biological processes. PMID:26994464

  6. Benthic prokaryotic community dynamics along the Ardencaple Canyon, Western Greenland Sea

    NASA Astrophysics Data System (ADS)

    Quéric, Nadia-Valérie; Soltwedel, Thomas

    2012-07-01

    The Ardencaple Canyon, emanating from the Eastern Greenland continental rise over a distance of about 200 km towards the Greenland Basin, was investigated to determine the effect of enhanced down-slope transport mechanisms on deep-sea benthic prokaryotic communities. The concentration of viable bacterial cells (Live/Dead®BacLight) and prokaryotic incorporation rates (3H-thymidine, 14C-leucine) increased with increasing distance from the continental shelf. Multidimensional scaling (MDS) results from terminal restriction fragment length polymorphism (T-RFLP) analysis indicated a spatial coherence between the benthic bacterial community structure, prokaryotic incorporation rates, water content, protein concentration and the total organic matter in the sediments. The community complexity in sediments at 4-5 cm depth was lower in the central parts of the channel compared with the northern and the southern levees, while richness in surface sediments of all stations was similar. Lacking any clear indications for a recent mass sediment transport or funneled shelf drainage flows, high similarities between bacterial assemblages in sediments along the canyon course may thus be governed by a combination of an ice-edge induced particle flux, episodic down-slope and canyon-guided transport mechanisms.

  7. A comparison between two permanent broad band ocean bottom seismometers in the western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Frontera, T.; Deschamps, A.; Ugalde, A.; Jara, J. A.; Hello, Y.; Goula, X.; Olivera, C.

    2009-04-01

    The aim of this work is to compare two permanent broad band ocean bottom seismometers (OBS) in terms of noise conditions by taking to account their similar instrumentation types, but their very different site characteristics. Both OBS stations have Güralp CMG-3T three component broad band sensors and differential pressure gauges (DPG). The first sensor operates since August 2005 under the framework of a research project that aims to improve the knowledge of the seismicity and seismic risk in the Tarragona region (north eastern Spain). This pioneering project in Spain is being carried out by the Institut Geològic de Catalunya (IGC) and the Observatori de l'Ebre, in collaboration with the Spanish oil company Repsol Investigaciones Petrolíferas, and is being financed by the Ministerio de Educación y Ciencia (CASABLANCA REN2003-06577), FEDER funding, the IGC and the Institut Cartogràfic de Catalunya. The OBS is installed inside the security perimeter of the Casablanca oil platform, which is located 40 km offshore Tarragona. The sensors are submerged at about 400 m to the SW of the oil platform at about 150 m in depth. Data are digitized on-site and are transmitted through a submarine cable to the platform, where they are recorded. In July 2007 some improvements were made: i) the OBS was completely buried and the DPG was moved about 10 m away from the OBS; and ii) via satellite signal transmission was implemented, which allowed to have continuous and real time data in Barcelona so that the OBS could be integrated into the Catalan Seismic Network. The second seismometer operates in the frame of the Antares neutrino telescope project developed in Liguria Sea. Geoazur is carrying out the project of deployment of a broad band seismological instrument in the aim of developing the permanent sea floor observation knowledge necessary to characterize Ligurian Sea seismicity and seismic risk along French Riviera coast (SE France). The operation was facilitated by the

  8. A comparison between two permanent broad band ocean bottom seismometers in the western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Frontera, T.; Deschamps, A.; Ugalde, A.; Jara, J. A.; Hello, Y.; Goula, X.; Olivera, C.

    2009-04-01

    The aim of this work is to compare two permanent broad band ocean bottom seismometers (OBS) in terms of noise conditions by taking to account their similar instrumentation types, but their very different site characteristics. Both OBS stations have Güralp CMG-3T three component broad band sensors and differential pressure gauges (DPG). The first sensor operates since August 2005 under the framework of a research project that aims to improve the knowledge of the seismicity and seismic risk in the Tarragona region (north eastern Spain). This pioneering project in Spain is being carried out by the Institut Geològic de Catalunya (IGC) and the Observatori de l'Ebre, in collaboration with the Spanish oil company Repsol Investigaciones Petrolíferas, and is being financed by the Ministerio de Educación y Ciencia (CASABLANCA REN2003-06577), FEDER funding, the IGC and the Institut Cartogràfic de Catalunya. The OBS is installed inside the security perimeter of the Casablanca oil platform, which is located 40 km offshore Tarragona. The sensors are submerged at about 400 m to the SW of the oil platform at about 150 m in depth. Data are digitized on-site and are transmitted through a submarine cable to the platform, where they are recorded. In July 2007 some improvements were made: i) the OBS was completely buried and the DPG was moved about 10 m away from the OBS; and ii) via satellite signal transmission was implemented, which allowed to have continuous and real time data in Barcelona so that the OBS could be integrated into the Catalan Seismic Network. The second seismometer operates in the frame of the Antares neutrino telescope project developed in Liguria Sea. Geoazur is carrying out the project of deployment of a broad band seismological instrument in the aim of developing the permanent sea floor observation knowledge necessary to characterize Ligurian Sea seismicity and seismic risk along French Riviera coast (SE France). The operation was facilitated by the

  9. Precessional changes in the western equatorial Pacific Hydroclimate: A 240 kyr marine record from the Halmahera Sea, East Indonesia

    NASA Astrophysics Data System (ADS)

    Dang, Haowen; Jian, Zhimin; Kissel, Catherine; Bassinot, Franck

    2015-01-01

    the precession band, an interhemispheric antiphase pattern in the tropical hydroclimate is supported by many paleorecords, and optimally explained by the forcing of precessional insolation change. However, scenarios within the western equatorial Pacific (WEP), which plays the role of the ascending center of atmospheric convection, remain poorly determined. In this study, a marine sediment core from the Halmahera Sea, East Indonesia, was analyzed with high-resolution XRF scanning, quantitative discrete XRF, and ICP-AES/MS measurements. The terrigenous fractions in this core are constrained by their trace elemental characteristics to be locally sourced from Halmahera Island, and hence reflect variations in the local riverine runoff and precipitation. On this basis, a continuous record of precipitation changes of the western equatorial Pacific was reconstructed with multidecadal resolution over the last ˜240 ka, using an age model established by the correlation between an adjusted ice volume model and benthic δ18O constrained by 14C dating. The records of terrigenous input show a dominant ˜23 kyr periodicity with a 90°˜100° phase lag to the boreal summer (i.e., in-phase with the boreal autumn) insolation change. This pattern can be explained by the variability in the convective activity over the WEP, which might be primarily controlled by precessional changes in the El Niño and Southern Oscillation (ENSO) system. A dynamic linkage is implied between the precessional variations in the convective activity in the WEP and the East Asian and Australia-Indonesian summer monsoons (EASM and AISM), in the sense of their distinct stable phase relationship to precession.

  10. Localized accumulation and a shelf-basin gradient of particles in the Chukchi Sea and Canada Basin, western Arctic

    NASA Astrophysics Data System (ADS)

    Yamada, Yosuke; Fukuda, Hideki; Uchimiya, Mario; Motegi, Chiaki; Nishino, Shigeto; Kikuchi, Takashi; Nagata, Toshi

    2015-07-01

    Transparent exopolymer particles (TEP), particulate organic carbon (POC), and particles (size range: 5.2-119 μm) as determined by laser in situ scattering and transmissometry (LISST) were measured in the water column from the Chukchi Sea to the Canada Basin in the western Arctic Ocean, during the late summer of 2012. In general, the percentages of TEP-carbon to POC were high (the mean values for the shelf and slope-basin regions were 135.4 ± 58.0% (± standard deviation, n = 36) and 187.6 ± 73.3% (n = 58), respectively), relative to the corresponding values reported for other oceanic regions, suggesting that TEP play an important role in regulating particle dynamics. A hotspot (extremely high concentration) of particles, accompanied by high prokaryote abundance and production, was observed near the seafloor (depth 50 m) of the shelf region. Localized accumulation of particles was also found in the thin layer near the pycnocline (depth 10-30 m) and on the slope. Over a broader spatial scale, particle concentration gradients were identified from the shelf to the basin in the upper water column (<50 m). The particle-size distribution analysis indicated that relatively small particles were dominant in the shelf region compared to the slope-basin region. These results suggest that particles containing large amounts of TEP are produced in the shelf region and are potentially delivered to the slope-basin region along the pycnocline, which might support productivity and material cycles in the nutrient-depleted basin region of the western Arctic Ocean.

  11. New estimation of N2 fixation in the western and central Pacific Ocean and its marginal seas

    NASA Astrophysics Data System (ADS)

    Shiozaki, Takuhei; Furuya, Ken; Kodama, Taketoshi; Kitajima, Satoshi; Takeda, Shigenobu; Takemura, Toshihiko; Kanda, Jota

    2010-03-01

    The distribution of N2 fixation was examined using a 15N2 tracer with accompanying measurements of abundance of Trichodesmium spp. and Richelia intracellularis, nitrate plus nitrite (N+N) and soluble reactive phosphorus at the nanomolar level, and primary production in the western and central Pacific Ocean. N2 fixation occurred only in >˜20°C oligotrophic (i.e., N+N < 100 nM) waters except at a station in the equatorial upwelling zone where N+N was 1880 nM. High N2 fixation rates were observed in the Kuroshio and East China Sea (KECS) and near Fiji and other isolated islands with concomitant high abundance of Trichodesmium spp. In contrast, N2 fixation in the western and central oligotrophic North Pacific (WCONP) was significantly lower, and Trichodesmium spp. were rarely observed. These observations hint that KECS and waters around isolated islands are N2 fixation "hot spots" because of the occurrence of Trichodesmium spp. The average N2 fixation rate in the KECS of 232 ± 54.8 (±SE, n = 13) μmol N m-2 d-1 was almost 1 order of magnitude higher than that in the WCONP of 39.2 ± 7.51 (n = 26) μmol N m-2 d-1. On the basis of these estimates and reported values obtained using 15N2, depth-integrated N2 fixation in the North Pacific was estimated to be 2.6 ± 0.3 × 109 (n = 63) mol N d-1, which is less than half of previous estimates. This difference was ascribed primarily to the unavailability of N2 fixation rates in the WCONP, which occupies a vast area of the subtropical North Pacific, and the use of data obtained in the hot spots which represent small areas that likely led to the previous overestimation.

  12. The effect of organohalogen contaminants on western Steller sea lion survival and movement in the Russian Far East.

    PubMed

    Zaleski, Adam; Atkinson, Shannon; Burkanov, Vladimir; Quinn, Terrance

    2014-08-15

    The western stock of Steller sea lions (Eumetopias jubatus) have experienced dramatic declines since the 1960s, particularly in the western Alaskan and Asian portions, which have continued to decline or stabilized at low levels. Multiple causes for this decline have been proposed and may include anthropogenic contamination from organohalogen contaminants (OCs). These include polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT), which have not been ruled out as a potential cause for the lack of recovery. The objective of this study was to determine the effects of OCs on survival and movement probabilities estimated in program MARK using resighting data collected from 2003 to 2009. PCBs and DDTs were measured in whole blood from 136 (74 males and 62 females) individually marked, free-ranging pups from four Russian Far East rookeries. The mean concentration of ∑PCB and ∑DDT was 4.25±5.12 and 3.22±4.28 ng g(-1) ww (n=136), respectively, and the average ∑PCB and ∑DDT concentration for those above the aggregate mean (n=44) was 9.25±6.55 and 7.65±5.21 ng g(-1) ww, and those below the aggregate mean (n=92) the concentration was 1.86±0.89 and 1.11±0.65 ng g(-1) ww, respectively. The lowest estimated probabilities of survival occurred in the first year, ranging from 38% to 74%, but increased for ages 1-9, ranging from 82% to 94%. The greatest movement occurred from Medny Island west toward the Kamchatka Peninsula (33%) and to Bering Island (18%), and low movement estimates for other natal rookeries was largely due to minimal resighting effort. The estimated probabilities of resighting varied by location (48%-87%), but had greater precision than survival or movement parameters. Survival and movement were most affected by age and location rather than OCs. PMID:24887189

  13. New insights into the organic carbon export in the Mediterranean Sea from 3-D modeling

    NASA Astrophysics Data System (ADS)

    Guyennon, A.; Baklouti, M.; Diaz, F.; Palmieri, J.; Beuvier, J.; Lebaupin-Brossier, C.; Arsouze, T.; Béranger, K.; Dutay, J.-C.; Moutin, T.

    2015-12-01

    The Mediterranean Sea is one of the most oligotrophic regions of the oceans, and nutrients have been shown to limit both phytoplankton and bacterial activities, resulting in a potential major role of dissolved organic carbon (DOC) export in the biological pump. Strong DOC accumulation in surface waters is already well documented, though measurements of DOC stocks and export flux are still sparse and associated with major uncertainties. This study provides the first basin-scale overview and analysis of organic carbon stocks and export fluxes in the Mediterranean Sea through a modeling approach based on a coupled model combining a mechanistic biogeochemical model (Eco3M-MED) and a high-resolution (eddy-resolving) hydrodynamic simulation (NEMO-MED12). The model is shown to reproduce the main spatial and seasonal biogeochemical characteristics of the Mediterranean Sea. Model estimations of carbon export are also of the same order of magnitude as estimations from in situ observations, and their respective spatial patterns are mutually consistent. Strong differences between the western and eastern basins are evidenced by the model for organic carbon export. Though less oligotrophic than the eastern basin, the western basin only supports 39 % of organic carbon (particulate and dissolved) export. Another major result is that except for the Alboran Sea, the DOC contribution to organic carbon export is higher than that of particulate organic carbon (POC) throughout the Mediterranean Sea, especially in the eastern basin. This paper also investigates the seasonality of DOC and POC exports as well as the differences in the processes involved in DOC and POC exports in light of intracellular quotas. Finally, according to the model, strong phosphate limitation of both bacteria and phytoplankton growth is one of the main drivers of DOC accumulation and therefore of export.

  14. Environmental factors controlling particulate mass fluxes on the Mallorca continental slope (Western Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Pasqual, Catalina; Amores, Angel; Flexas, M. Mar; Monserrat, Sebastià; Calafat, Antoni

    2014-10-01

    Settled material recorded by two near bottom sediment traps deployed from November 2009 to February 2011 at northern (Sóller) and southern (Cabrera) slopes of Mallorca Island (Western Mediterranean) is studied with the aim of discerning their possible origin. The total settled particulate mass fluxes (TMF) at Sóller station were found to be, on average, 2.8 times greater than at Cabrera location during the deployment period, although both time series had a similar temporal evolution. It is suggested that wind episodes affecting the entire area were the common forcing, causing a primary production enhancement and being responsible of the similar temporal behavior. The greater sediment amounts collected in Sóller are explained on the basis of two physical mechanisms: 1) a number of successive eddies generated by instabilities of the Balearic Current that are regularly observed on satellite images, some of which have been reported to reach the seabed, thus increasing near bottom velocities and causing sediment resuspension. And 2) bottom trapped waves that are evidenced from a wavelet analysis in Sóller which could affect the TFM by enhancing sediment resuspension or advecting material from the surrounding areas.

  15. East-west differences in water mass, nutrient, and chlorophyll a distributions in the sea ice reduction region of the western Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Nishino, Shigeto; Shimada, Koji; Itoh, Motoyo; Yamamoto-Kawai, Michiyo; Chiba, Sanae

    2008-01-01

    The R/V Mirai conducted hydrographic surveys in the western Arctic Ocean during summer 2004 across a front between cold Arctic water and warm water from the Pacific Ocean where sea ice cover has been largely reduced in recent summers. The hydrographic data indicate a new type of vertical temperature minimum water west of the front along isohaline surfaces with approximate salinity (S) of 32, which is fresher than the typical temperature minimum (S ≈ 33) caused by spreading of Pacific winter water (PWW) mainly to the east of the front. Both of the temperature minimum waters are characterized by low potential vorticity with near-freezing temperature, suggesting that they are formed by winter convection with sea ice formation. A difference between the waters results from a large contribution of sea ice meltwater to the fresh temperature minimum (frTmin) water of S ≈ 32. The distributions of the sea ice meltwater contribution and nitrogen deficit suggest that summer shelf water, largely influenced by the sea ice melt in the Chukchi Sea, is modified by winter convection on its way to the Chukchi Abyssal Plain to form the frTmin water. This water supplies nutrients through the water distribution to the west of the front at depths shallower than the nutrient maximum layer caused by the PWW spreading. The shallower nutrient supply by the frTmin water combined with light penetration without sea ice cover could produce a prominent chlorophyll a maximum layer west of the front.

  16. A sharp Moho step under the Central and Eastern Betics, Western Mediterranean region.

    NASA Astrophysics Data System (ADS)

    de Lis Mancilla, Flor; Heit, Benjamin; Morales, Jose; Heit, Xiaohui; Molina-Aguilera, Antonio; Stich, Daniel

    2015-04-01

    We map the lithospheric structure under the central and eastern Betics (western Mediterranean region) interpreting P-receiver functions obtained from two dense seismic profiles (HIRE and Transcorbe profiles of ~120 km and 160 km of length, respectively). The goal is to study the lithospheric structure and its variations between the different geological domains, from the Alboran domain in the south (metamorphic rocks), the External zones (sedimentary rocks) and the Variscan terrains of the Iberian Massif in the north. One of the profiles (HIRE), North-South oriented, crosses the Sierra Nevada Mountains, one of the prominent features in the Western Mediterranean tectonic region with the highest topography of the Iberia peninsula (~3400 m). The spacing between stations, around 2km, allows mapping with high accuracy of the variations of the crustal structure. We observe a sharp Moho step of ~15 km under the Internal zones of the Alboran domain coinciding the thinner crust with the highest topography along the profile. This agrees with the prior hypothesis about the lack of crustal root underneath Sierra Nevada Mountains and opens a question about the source of the dynamic compensation of its topography. Previous studies showed that the Iberian crust understrust the Alboran domain under its contact with the External zones observing the presence of slab-type feature of Iberian lithosphere at the western Betics while tearing and delamination of this Iberian slab is proposed at eastern Betics. We observe that the Iberian crust undertrust the Alboran domain and terminate sharply under the contact between the Alpujarride and the Nevado-Filabre complexes (Alboran domain).

  17. Lower Miocene coeval thrusting and strike-slip faulting in the Western Betics

    NASA Astrophysics Data System (ADS)

    Frasca, Gianluca; Gueydan, Frédéric; Brun, Jean-Pierre

    2015-04-01

    In the framework of the Africa-Europe convergence, the Mediterranean system presents a complex interaction between subduction rollback and upper subduction plate deformation since 30 Ma. The western end of the system shows an arcuate geometry across the Gibraltar arc, the Betico-Rifean belt, in which the relationship between slab dynamics and onshore tectonics is poorly constrained. The present study focuses on the Western Betics, which is characterized by two major thrusts: 1/ the Alboran Front limits the metamorphic domain (Alboran Domain) from the fold-and-thrust belts involving the Mesozoic cover of the Iberian margin (Subbetics Domain); 2/ the Alboran Internal Thrust allows the juxtaposition of a strongly attenuated lithosphere section, containing the large Ronda subcontinental mantle bodies, on top of crustal rocks. New structural data show that two major E-W strike-slip corridors controlled the deformation pattern of the Alboran Domain, in which E-W dextral strike-slip faults, N60° thrusts and N140° normal faults developed simultaneously during dextral strike-slip simple shear. The Alozaina piggy-back Basin, mainly formed by olistotromic deposits of Lower Miocene age, provides an age estimate for the continuous westward translation of the Alboran Domain, with reference to Iberia, that is accommodated mainly by an E-W lateral strike-slip ramp and a N60° frontal thrust ramp. In this context, a thrust sequence led to the piling up of thrust units in the Western Betics and to the crustal emplacement of the Ronda Peridotites bodies.

  18. Future sea ice conditions in Western Hudson Bay and consequences for polar bears in the 21st century.

    PubMed

    Castro de la Guardia, Laura; Derocher, Andrew E; Myers, Paul G; Terwisscha van Scheltinga, Arjen D; Lunn, Nick J

    2013-09-01

    The primary habitat of polar bears is sea ice, but in Western Hudson Bay (WH), the seasonal ice cycle forces polar bears ashore each summer. Survival of bears on land in WH is correlated with breakup and the ice-free season length, and studies suggest that exceeding thresholds in these variables will lead to large declines in the WH population. To estimate when anthropogenic warming may have progressed sufficiently to threaten the persistence of polar bears in WH, we predict changes in the ice cycle and the sea ice concentration (SIC) in spring (the primary feeding period of polar bears) with a high-resolution sea ice-ocean model and warming forced with 21st century IPCC greenhouse gas (GHG) emission scenarios: B1 (low), A1B (medium), and A2 (high). We define critical years for polar bears based on proposed thresholds in breakup and ice-free season and we assess when ice-cycle conditions cross these thresholds. In the three scenarios, critical years occur more commonly after 2050. From 2001 to 2050, 2 critical years occur under B1 and A2, and 4 under A1B; from 2051 to 2100, 8 critical years occur under B1, 35 under A1B and 41 under A2. Spring SIC in WH is high (>90%) in all three scenarios between 2001 and 2050, but declines rapidly after 2050 in A1B and A2. From 2090 to 2100, the mean spring SIC is 84 (±7)% in B1, 56 (±26)% in A1B and 20 (±13)% in A2. Our predictions suggest that the habitat of polar bears in WH will deteriorate in the 21st century. Ice predictions in A1B and A2 suggest that the polar bear population may struggle to persist after ca. 2050. Predictions under B1 suggest that reducing GHG emissions could allow polar bears to persist in WH throughout the 21st century. PMID:23716301

  19. 3D multidisciplinary numerical model of polychlorinated biphenyl dynamics on the Black Sea north-western shelf

    NASA Astrophysics Data System (ADS)

    Bagaiev, Andrii; Ivanov, Vitaliy

    2014-05-01

    The Black Sea north-western shelf plays a key role in economics of the developing countries such as Ukraine due to food supply, invaluable recreational potential and variety of the relevant maritime shipping routes. On the other hand, a shallow flat shelf is mostly affected by anthropogenic pollution, eutrophication, hypoxia and harmful algae blooms. The research is focused on modeling the transport and transformation of PCBs (PolyChlorinated Biphenyls) because they are exceedingly toxic and highly resistant to degradation, hence cumulatively affect marine ecosystems. Being lipophilic compounds, PCBs demonstrate the distinguishing sorption/desorption activity taking part in the biogeochemical fluxes via the organic matter particles and sediments. In the framework of the research, the coastal in-situ data on PCB concentration in the water column and sediments are processed, visualized and analyzed. It is concluded that the main sources of PCBs are related to the Danube discharge and resuspension from the shallow-water sediments. Developed 3D numerical model is aimed at simulation of PCB contamination of the water column and sediment. The model integrates the full physics hydrodynamic block as well as modules, which describe detritus transport and transformation and PCB dynamics. Three state variables are simulated in PCB transport module: concentration in solute, on the settling particles of detritus and in the top layer of sediments. PCB adsorption/desorption on detritus; the reversible PCB fluxes at the water-sediment boundary; destruction of detritus are taken into consideration. Formalization of PCB deposition/resuspension in the sediments is adapted from Van Rijn's model of the suspended sediment transport. The model was spun up to reconstruct the short term scenario of the instantaneous PCB release from the St. George Arm of Danube. It has been shown that PCB transport on sinking detritus represents the natural buffer mechanism damping the spreading PCB

  20. Segregation of herring larvae from inshore and offshore spawning grounds in the north-western North Sea — Implications for stock structure

    NASA Astrophysics Data System (ADS)

    Heath, M.

    Herring larvae hatching from spawning sites around the Scottish coast are dispersed by water currents during the weeks following hatching. Hydrographic data, observations on the distribution of caesium-137 and measurements of current velocities by moored meters and drifting buoys, suggest that larvae from offshore spawning sites around the north of Scotland should be more rapidly dispersed than those hatching in inshore areas. This has been confirmed by direct observations on the advection of herring larvae in different regions of the north western North Sea. The conclusion is that larvae hatching in inshore areas, especially in the Moray Firth, are most likely to contribute to nearby juvenile populations, whereas larvae from offshore spawning sites should be widely dispersed over the North Sea. Tagging and parasitology investigations have shown that adult herring spawning in the north-western North Sea have been widely dispersed in the North Sea and adjacent waters as juveniles (six months — one and a half years old). However, a high proportion of adult fish caught at inshore spawning sites and in the Moray Firth were found to have been recruited from more local areas. Taken together with the observations on larval drift, these observations suggest that the stock structure of herring in the northern North Sea may in part be a consequence of the physical oceanography of the area.

  1. Patterns in bacterial and archaeal community structure and diversity in western Beaufort Sea sediments and waters

    NASA Astrophysics Data System (ADS)

    Hamdan, L. J.; Sikaroodi, M.; Coffin, R. B.; Gillevet, P. M.

    2010-12-01

    A culture-independent phylogenetic study of microbial communities in water samples and sediment cores recovered from the Beaufort Sea slope east of Point Barrow, Alaska was conducted. The goal of the work was to describe community composition in sediment and water samples and determine the influence of local environmental conditions on microbial populations. Archaeal and bacterial community composition was studied using length heterogeneity-polymerase chain reaction (LH-PCR) and multitag pyrosequencing (MTPS). Sediment samples were obtained from three piston cores on the slope (~1000m depth) arrayed along an east-west transect and one core from a depth of approximately 2000m. Discrete water samples were obtained using a CTD-rosette from three locations adjacent to piston core sites. Water sample were selected at three discrete depths within a vertically stratified (density) water column. The microbial community in near surface waters was distinct from the community observed in deeper stratified layers of the water column. Multidimensional scaling analysis (MDS) revealed that water samples from mid and deep stratified layers bore high similarity to communities in cores collected in close proximity. Overall, the highest diversity (bacteria and archaea) was observed in a core which had elevated methane concentration relative to other locations. Geochemical (e.g., bulk organic and inorganic carbon pools, nutrients, metabolites) and physical data (e.g. depth, water content) were used to reveal the abiotic factors structuring microbial communities. The analysis indicates that sediment water content (porosity) and inorganic carbon concentration are the most significant structuring elements on Beaufort shelf sedimentary microbial communities.

  2. New evidence for the postglacial lowstand of sea level in the western Gulf of Maine

    SciTech Connect

    Barnhardt, W.A.; Belknap, D.F.; Bund, S. . Dept. of Geological Sciences); Kelley, J.T. )

    1992-01-01

    Emergent glaciomarine deltas in Maine exhibit variable geometry and internal architecture related to differing accommodation space and the irregular topography of underlying Paleozoic bedrock. Recently, 1,024 km of new side-scan sonar records and 235 km of seismic reflection profiles were used to map the distribution of surficial sediments, to understand their relationship to the region's Quaternary stratigraphy, and to refine models of delta evolution during times of rapidly changing base-level. These lowstand deposits are as variable as their highstand counterparts, and their morphology and seismic stratigraphy appear controlled by local bedrock topography. Seaward of the Kennebec River, a large fan-shaped paleodelta overlies the eroded surface of older glacial sediments. Fine-grained materials, unconformably overlying glaciomarine sediments and interpreted as prodeltaic muds, comprise a significant portion of the delta's volume. Although multi-lobate and initially conceived as a classic Gilbert type delta, seaward-dipping reflectors above the inferred prodeltaic deposits are generally interpreted as channel-fill deposits, not foresets. Holocene erosion has removed most evidence of topset beds except in a few areas sheltered by linear bedrock shoals and islands. Erosion has also locally exhumed portions of the underlying glacial sediments, creating a palimpsest of rippled gravel ribbons across the otherwise sandy delta top. Sandy paleodeltas do not exist seaward of other Maine rivers which drain similar terrain. The absence of thick, sandy deltas seaward of these rivers and the presence of regressive sand deposits in their upper valleys implies local differences in sediment supply and in the timing of their formation with respect to deglaciation and relative sea-level changes.

  3. Biologically active warm-core anticyclonic eddies in the marginal seas of the western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Chen, Yuh-ling Lee; Chen, Houng-Yung; Jan, Sen; Lin, Yen-Huei; Kuo, Tien-Hsia; Hung, Jia-Jang

    2015-12-01

    Our investigations in the northern South China Sea (SCS) have revealed warm-core anticyclonic eddies that had a depressed pycnocline and a high biological productivity and phytoplankton abundance. With an elliptical shape of 420-430 km in major axis and 240-260 km in minor axis, these eddies were formed in the winter as the Kuroshio Current intruded through the Luzon Strait into the SCS under the prevailing northeast monsoon. They were characterized by a deep mixed layer up to 140-180 m, in which nitrate was relatively abundant. Although chlorophyll a concentration per volume of seawater was not always higher inside than outside the eddies, water-column (0-200 m) integrated chlorophyll a concentration and abundances of Synechococcus, coccolithophores, and diatoms were higher inside than outside the eddies. Primary productivity and nitrate-uptake new production inside the eddies were higher than or equal to those outside the eddies. Unlike the mode-water anticyclonic eddy that is biologically productive with a domed shallow seasonal pycnocline, the eddies we investigated had high surface temperatures and depressed pycnoclines in the upper water column. Possible explanations for these biological aspects were that the eddies were at their decaying stage, the eddies re-incorporated intermittently with an intruding Kuroshio branch, or the passage of the prevalent high amplitude internal tides introduced nutrients to the eddies. Frequent occurrences of eddies in oceanic regimes, especially cold eddies, are associated with high biological activity. Some warm eddies, such as these investigated in the present study, also have high biological activities, indicating that more rigorous in situ studies relating to eddy biological activity are needed in ocean regimes such as the SCS, where a half of the eddies are warm eddies.

  4. Meso-scale variability of coastal suprabenthic communities in the southern Tyrrhenian Sea (western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Fanelli, E.; Cartes, J. E.; Badalamenti, F.; D'Anna, G.; Pipitone, C.; Azzurro, E.; Rumolo, P.; Sprovieri, M.

    2011-02-01

    Meso-scale spatial variability of coastal suprabenthic communities inhabiting muddy bottoms at 50-80 m depth in three gulfs of northern Sicily (Western Mediterranean) was here investigated. Although similar as concerns the hydrological and oceanographic conditions, the three areas, that encompass a large portion of the continental shelf (135 km), are characterized by different geo-morphological features. In addition, they are subjected to different trawl fishery pressures. The Gulf of Castellammare is a semi-enclosed bay, where the trawling activity has been banned since 1990. The Gulf of Termini Imerese and the Gulf of Sant'Agata are open areas, subjected to high trawl fishing intensity. In terms of density, gammarid amphipods showed differences among the three gulfs; in terms of biomass, cumaceans and amphipods were more abundant in the Gulf of Castellammare than in the other two areas. Multivariate analyses provided evidence for separation of suprabenthic assemblages between the Gulf of Castellammare and the other two gulfs. The Gulf of Castellammare seemed to host the most diversified and stable community according to α- and β-diversity indices. In the same way the low value of δ 13C vs. δ 15N correlation found in the gulf of Castellammare, which evidences the occurrence of several food sources, supports the idea of a higher stability in the semi-enclosed, trawl-ban area. In the other two areas δ 13C vs. δ 15N correlations were high, suggesting the existence of a pelagic source sustaining the suprabenthic communities. This is also confirmed by the lower δ 13C concentrations found in suprabenthic species. Taking into account the homogeneous oceanographic conditions among gulfs, other factors, such as geo-morphology and trawling pressure should be involved in the observed differences among the three areas in terms of assemblage structure, diversity, and trophodynamics of suprabenthic communities.

  5. Applicability of an empirical law to predict significant sea-wave heights from microseisms along the Western Ligurian Coast (Italy)

    NASA Astrophysics Data System (ADS)

    Ferretti, Gabriele; Scafidi, Davide; Cutroneo, Laura; Gallino, Stefano; Capello, Marco

    2016-07-01

    The use of microseisms with appropriate predictive laws is a reliable method for estimating such sea-wave parameters as period and significant height. Through the use of opportune predictive laws calibrated with measurements obtained from wave buoys, it is possible to determine the significant height of the wave as a function of the spectral energy-content of the microseism. In this paper we will present a procedure that utilises microseisms recorded by a micro network of five seismic stations to predict the significant height of waves, and its uncertainty, along the western Ligurian coast (Italy). The calibration and validation of the procedure was performed using wave measurements obtained from a wave buoy off Capo Mele (Imperia, Italy) over a two and a half year period. The differences between the significant heights measured by the wave buoy and the empirical predictions were less than 10 cm (corresponding to 10% of the mean measured value) for 47% of the data and less than 20 cm (corresponding to 20% of the mean measured value) for 72%.

  6. Response of rocky reef top predators (Serranidae: Epinephelinae) in and around marine protected areas in the Western Mediterranean Sea.

    PubMed

    Hackradt, Carlos Werner; García-Charton, José Antonio; Harmelin-Vivien, Mireille; Pérez-Ruzafa, Ángel; Le Diréach, Laurence; Bayle-Sempere, Just; Charbonnel, Eric; Ody, Denis; Reñones, Olga; Sanchez-Jerez, Pablo; Valle, Carlos

    2014-01-01

    Groupers species are extremely vulnerable to overfishing and many species are threatened worldwide. In recent decades, Mediterranean groupers experienced dramatic population declines. Marine protected areas (MPAs) can protect populations inside their boundaries and provide individuals to adjacent fishing areas through the process of spillover and larval export. This study aims to evaluate the effectiveness of six marine reserves in the Western Mediterranean Sea to protect the populations of three species of grouper, Epinephelus marginatus, Epinephelus costae and Mycteroperca rubra, and to understand in which circumstances MPAs are able to export biomass to neighbouring areas. All the studied MPAs, except one where no grouper was observed, were able to maintain high abundance, biomass and mean weight of groupers. Size classes were more evenly distributed inside than outside MPAs. In two reserves, biomass gradients could be detected through the boundaries of the reserve as an indication of spillover. In some cases, habitat structure appeared to exert a great influence on grouper abundance, biomass and mean individual weight, influencing the gradient shape. Because groupers are generally sedentary animals with a small home range, we suggest that biomass gradients could only occur where groupers attain sufficient abundance inside MPA limits, indicating a strongly density-dependent process. PMID:24905331

  7. Preliminary hydrocarbon source rock assessment of the Paleozoic and Mesozoic formations of the western Black Sea region of Turkey

    SciTech Connect

    Harput, B.O.; Demirel, I.H.; Karayigit, A.I.; Aydin, M.; Sahintuerk, O.; Bustin, R.M.

    1999-12-01

    Source rock maturity and potential of Paleozoic and Mesozoic formations in the Eregli, Zonguldak, Bartin, Ulus, and Eflani subregions of the western Black Sea region (WBSR), have been investigated by rock-eval pyrolysis, reflected-light microscopy, and palynofacies analyses. The % Ro values of dispersed organic matter of the Paleozoic formations primarily range from 0.72 to 1.8%, but values as high as 2.6% occur locally in the Silurian Findikli Formation in the Eregli subregion. The % Ro values of Namurian-Westphalian coal seams in the K20/H well drilled in the Zonguldak subregion range from 0.87 to 1.52%, with increasing depth consistent with sedimentary depth of burial. Most Cretaceous age samples have reflectance values ranging from 0.44 to 1.6% Ro that indicates they are marginally mature to mature with respect to the oil window. Rock-eval pyrolysis demonstrates that the Paleozoic formations have limited oil-generation potential (HI values {le} 200 mg HC/g C{sub org}), but good gas potential (TOC values up to 3%). Cretaceous formations have better petroleum source rock characteristics, but they too are primarily gas prone. Variations in the source rock maturity probably reflect variable burial histories in different localities of the WBSR.

  8. Response of Rocky Reef Top Predators (Serranidae: Epinephelinae) in and Around Marine Protected Areas in the Western Mediterranean Sea

    PubMed Central

    Hackradt, Carlos Werner; García-Charton, José Antonio; Harmelin-Vivien, Mireille; Pérez-Ruzafa, Ángel; Le Diréach, Laurence; Bayle-Sempere, Just; Charbonnel, Eric; Ody, Denis; Reñones, Olga; Sanchez-Jerez, Pablo; Valle, Carlos

    2014-01-01

    Groupers species are extremely vulnerable to overfishing and many species are threatened worldwide. In recent decades, Mediterranean groupers experienced dramatic population declines. Marine protected areas (MPAs) can protect populations inside their boundaries and provide individuals to adjacent fishing areas through the process of spillover and larval export. This study aims to evaluate the effectiveness of six marine reserves in the Western Mediterranean Sea to protect the populations of three species of grouper, Epinephelus marginatus, Epinephelus costae and Mycteroperca rubra, and to understand in which circumstances MPAs are able to export biomass to neighbouring areas. All the studied MPAs, except one where no grouper was observed, were able to maintain high abundance, biomass and mean weight of groupers. Size classes were more evenly distributed inside than outside MPAs. In two reserves, biomass gradients could be detected through the boundaries of the reserve as an indication of spillover. In some cases, habitat structure appeared to exert a great influence on grouper abundance, biomass and mean individual weight, influencing the gradient shape. Because groupers are generally sedentary animals with a small home range, we suggest that biomass gradients could only occur where groupers attain sufficient abundance inside MPA limits, indicating a strongly density-dependent process. PMID:24905331

  9. Growth conditions of 0-group plaice Pleuronectes platessa in the western Wadden Sea as revealed by otolith microstructure analysis

    NASA Astrophysics Data System (ADS)

    Cardoso, Joana F. M. F.; Freitas, Vânia; de Paoli, Hélène; Witte, Johannes IJ.; van der Veer, Henk W.

    2016-05-01

    Growth studies based on population-based growth estimates are limited by the fact that they do not take into account differences in age/size structure within the population. To overcome these problems, otolith microstructure analysis is often used to estimate individual growth. Here, we analyse growth of 0-group plaice in the western Wadden Sea in two years: a year preceded by a mild winter (1995) and a year preceded by a severe winter (1996). Growth was analysed by combining information on individual growth based on otolith analysis with predictions of maximum growth (= under optimal food conditions) based on a Dynamic Energy Budget model. Otolith analysis revealed that settlement occurred earlier in 1995 than in 1996. In both years, one main cohort was found, followed by a group of late settlers. No differences in mean length-at-age were found between these groups. DEB modelling suggested that growth was not maximal during the whole growing season: realized growth (the fraction of maximum growth realized by 0-group plaice) declined in the summer, although this decline was relatively small. In addition, late settling individuals exhibited lower realized growth than individuals from the main cohort. This study confirms that growth conditions for 0-group plaice are not optimal and that a growth reduction occurs in summer, as suggested in previous studies.

  10. Biogeochemistry of a low-activity cold seep in the Larsen B area, western Weddell Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Niemann, H.; Fischer, D.; Graffe, D.; Knittel, K.; Montiel, A.; Heilmayer, O.; Nöthen, K.; Pape, T.; Kasten, S.; Bohrmann, G.; Boetius, A.; Gutt, J.

    2009-06-01

    First videographic indication of an Antarctic cold seep ecosystem was recently obtained from the collapsed Larsen B ice shelf, western Weddell Sea (Domack et al., 2005). Within the framework of the R/V Polarstern expedition ANTXXIII-8, we revisited this area for geochemical, microbiological and further videographical examinations. During two dives with ROV Cherokee (MARUM, Bremen), several bivalve shell agglomerations of the seep-associated, chemo syntheticclam Calyptogena sp. were found in the trough of the Crane and Evans glacier. The absence of living clam specimens indicates that the flux of sulphide and hence the seepage activity is diminished at present. This impression was further substantiated by our geochemical observations. Concentrations of thermogenic methane were moderately elevated with 2 μM in surface sediments of a clam patch, increasing up to 9 μM at a sediment depth of about 1 m in the bottom sections of the sediment cores. This correlated with a moderate decrease in sulphate from 28 mM at the surface down to 23.4 mM, an increase in sulphide to up to 1.43 mM and elevated rates of the anaerobic oxidation of methane (AOM) of up to 600 pmol cm-3 d-1 at about 1 m below the seafloor. Molecular analyses indicate that methanotrophic archaea related to ANME-3 are the most likely candidates mediating AOM in sediments of the Larsen B seep (Domack et al., 2005; EOS 86, 269-276).

  11. Biogeochemistry of a low-activity cold seep in the Larsen B area, western Weddell Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Niemann, H.; Fischer, D.; Graffe, D.; Knittel, K.; Montiel, A.; Heilmayer, O.; Nöthen, K.; Pape, T.; Kasten, S.; Bohrmann, G.; Boetius, A.; Gutt, J.

    2009-11-01

    First videographic indication of an Antarctic cold seep ecosystem was recently obtained from the collapsed Larsen B ice shelf, western Weddell Sea (Domack et al., 2005). Within the framework of the R/V Polarstern expedition ANTXXIII-8, we revisited this area for geochemical, microbiological and further videographical examinations. During two dives with ROV Cherokee (MARUM, Bremen), several bivalve shell agglomerations of the seep-associated, chemosynthetic clam Calyptogena sp. were found in the trough of the Crane and Evans glacier. The absence of living clam specimens indicates that the flux of sulphide and hence the seepage activity is diminished at present. This impression was further substantiated by our geochemical observations. Concentrations of thermogenic methane were moderately elevated with 2 μM in surface sediments of a clam patch, increasing up to 9 μM at a sediment depth of about 1 m in the bottom sections of the sediment cores. This correlated with a moderate decrease in sulphate from about 28 mM at the surface down to 23.4 mM, an increase in sulphide to up to 1.43 mM and elevated rates of the anaerobic oxidation of methane (AOM) of up to 600 pmol cm-3 d-1 at about 1 m below the seafloor. Molecular analyses indicate that methanotrophic archaea related to ANME-3 are the most likely candidates mediating AOM in sediments of the Larsen B seep.

  12. Trace metal fluxes to ferromanganese nodules from the western Baltic Sea as a record for long-term environmental changes

    SciTech Connect

    Hlawatsch, S.; Garbe-Schonberg, C.D.; Lechtenberg, F.; Manceau, A.; Tamura, N.; Kulik, D.A.; Suess, E.; Kersten, M.

    2002-03-12

    Trace element profiles in ferromanganese nodules from the western Baltic Sea were analyzed with laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) and synchrotron-based micro-X-ray radiation techniques (fluorescence: mSXRF, and diffraction: mXRD) at high spatial resolution in growth direction. Of the trace elements studied (Zn, Cu, Cd, Ni, Co, Mo, Ba), Zn showed the most significant enrichment, with values in the outermost surface layers of up to six-fold higher than those found in older core parts. The high-resolution Zn profiles provide the necessary temporal resolution for a dating method analogous to dendrochronology. Profiles in various samples collected during two decades were matched and the overlapping sections used for estimation of the accretion rates. Assuming a continuous accretion of these relatively fast growing nodules (on average 20 mm a-1) over the last century, the Zn enrichment was thus assessed to have commenced around 1860/70 in nodules from the Kiel Bight and in 1880/90 from Mecklenburg Bight, reflecting the enhanced heavy metal emissions with rising industrialization in Europe. Apart from the obvious success with Zn, only As and Co show significant but only 1.5-fold enrichments in the most recent growth layers of the nodules. Other anthropogenic trace metals like Cu and Cd are not at all enriched, which, together with the distinct early-diagenetic Fe/Mn banding, weakens the potential of the nodules for retrospective monitoring.

  13. Decapod crustacean larval communities in the Balearic Sea (western Mediterranean): Seasonal composition, horizontal and vertical distribution patterns

    NASA Astrophysics Data System (ADS)

    Torres, Asvin P.; Dos Santos, Antonina; Balbín, Rosa; Alemany, Francisco; Massutí, Enric; Reglero, Patricia

    2014-10-01

    Decapod crustaceans are the main target species of deep water bottom trawl fisheries in the Balearic Sea but little is known about their larval stages. This work focuses on the species composition of the decapod larval community, describing the main spatio-temporal assemblages and assessing their vertical distribution. Mesozooplankton sampling was carried out using depth-stratified sampling devices at two stations located over the shelf break and the mid slope, in the north-western and southern Mallorca in late autumn 2009 and summer 2010. Differences among decapod larvae communities, in terms of composition, adult's habitat such as pelagic or benthic, and distribution patterns were observed between seasons, areas and station. Results showed that for both seasons most species and developmental stages aggregated within the upper water column (above 75 m depth) and showed higher biodiversity in summer compared to late autumn. Most abundant species were pelagic prawns (e.g., Sergestidae) occurring in both seasons and areas. The larval assemblages' distributions were different between seasonal hydrographic scenarios and during situations of stratified and non-stratified water column. The vertical distribution patterns of different larval developmental stages in respect to the adult's habitat were analyzed in relation to environmental variables. Fluorescence had the highest explanatory power. Four clearly different vertical patterns were identified: two corresponding to late autumn, which were common for all the main larval groups and other two in summer, one corresponding to larvae of coastal benthic and the second to pelagic species larvae.

  14. Sea ice and snow thickness and physical properties of an ice floe in the western Weddell Sea and their changes during spring warming

    NASA Astrophysics Data System (ADS)

    Haas, Christian; Nicolaus, Marcel; Willmes, Sascha; Worby, Anthony; Flinspach, David

    2008-04-01

    Helicopter-borne and ground-based electromagnetic (EM) ice thickness and ruler-stick snow thickness measurements as well as ice-core analyses of ice temperature, salinity and texture were performed over a 5-week observation period between November 27, 2004, and January 2, 2005, on an ice floe in the western Weddell Sea at approximately 67°S, 55°W. The study was part of the Ice Station Polarstern (ISPOL) expedition of German research icebreaker R.V. Polarstern, investigating changes of physical, biological, and biogeochemical properties during the spring warming as a function of atmospheric and oceanic boundary conditions. The ice floe was composed of fragments of thin and thick first-year ice and thick second-year ice, with modal total thicknesses of 1.2-1.3, 2.1, and 2.4-2.9 m, respectively. This included modal snow thicknesses of 0.2-0.5 m on first-year ice and 0.75 m on second-year ice. During the observation period, snow thickness decreased by less than 0.2 m. There was hardly any ice thinning. Warming of snow and ice between 0.1 and 1.9 °C resulted in decreased ice salinity and increased brine volume. Direct current (DC) geoelectric and electromagnetic (EM) induction depth sounding were performed to study changes of electrical ice conductivity as a result of the observed ice warming. Bulk ice conductivity increased from to 37 to 97 mS/m. Analysis of conductivity anisotropy showed that the horizontal ice conductivity changed from 9 to 70 mS/m. These conductivity changes have only negligible effects on the thickness retrieval from EM measurements.

  15. Trophodynamics of suprabenthic fauna on coastal muddy bottoms of the southern Tyrrhenian Sea (western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Fanelli, E.; Cartes, J. E.; Badalamenti, F.; Rumolo, P.; Sprovieri, M.

    2009-02-01

    The trophodynamics of suprabenthic fauna were analyzed in the Gulf of Castellammare (North-western Sicily, Italy) at depths ranging between 40 and 80 m. Variations in species abundance and biomass together with changes in nitrogen and carbon stable isotope composition were explored at a seasonal scale, from November 2004 to June 2005. Suprabenthos showed maximum biomass and abundance from late winter to summer, while minimum values were found in autumn. The highest abundances of mysids and copepods occurred in March, 1 month after the peak of primary production. Amphipod abundance was higher in summer, likely due to a relative increase in organic matter in the sediments. Statistical analysis provided evidence for separation of sample abundances as a function of season. The best match between suprabenthos abundance and environmental variables was found with Chlorophyll a recorded 3 months before the sampling. Stable isotope analyses suggest a relatively complex food web in the Gulf of Castellammare with several potential food sources. Some suprabenthic species (i.e. mysids and copepods) exhibited depleted values of δ13C, indicating a planktonic source of nutrition. Cumaceans and amphipods displayed more enriched δ13C values, pointing to more detritivorous behaviour. A third group with intermediate δ13C values comprised species with a mixed diet (e.g. Ampelisca spp., Apherusa vexatrix and Harpinia spp.). Assuming a 15N-enrichment of ca. 2.54‰ between consumers and their diet, at least two trophic levels can be distinctly identified: (1) filter feeders/grazers (mysids, copepods), suspension/deposit feeders ( Ampelisca spp., A. vexatrix, small Goneplax rhomboides) and omnivores, alternatively feeding on detritus and small invertebrates such as meiobenthos (the cumacean Leucon mediterraneus or the amphipod Westwoodilla rectirostris); (2) carnivores on small crustaceans and zooplankton (the amphipod Harpinia spp., the gobiid fish Lesuerigobius suerii and the decapod

  16. Subduction initiation and recycling of Alboran domain derived crustal components prior to the intra-crustal emplacement of mantle peridotites in the Westernmost Mediterranean: isotopic evidence from the Ronda peridotite

    NASA Astrophysics Data System (ADS)

    Varas-Reus, María Isabel; Garrido, Carlos J.; Bosch, Delphine; Marchesi, Claudio Claudio; Acosta-Vigil, Antonio; Hidas, Károly; Barich, Amel

    2014-05-01

    -Rif cordillera crustal rocks that might have been potentially subducted beneath the Alborán domain before the emplacement of Ronda peridotites. Isotopic data rules out potential crustal sources coming from pre-early Miocene Flysch Trough sediments and crustal rocks from the Blanca Unit currently underlying peridotite. Crustal rocks from the Jubrique Unit overlying the Ronda peridotite are the only crustal samples that may account for the relatively high 207Pb-208Pb/204Pb and low 206Pb/204Pb characteristic of the crustal contaminant added to the mantle source of late Cr-pyroxenites. These data strongly support Alboran geodynamic models that envisage slab roll-back as the tectonic mechanism responsible for Miocene lithospheric thinning, and provides a scenario where back-arc inversion leading to self-subduction of crustal units at the front of the Alboran wedge. REFERENCES 1. Durand-Delga, M., P. Rossi, P. Olivier, and D. Puglisi, Situation structurale et nature ophiolitique de roches basiques jurassiques associées aux flyschs maghrébins du Rif (Maroc) et de Sicile (Italie). Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science, 2000. 331(1): p. 29-38. 2. Lenoir, X., C. Garrido, J.L. Bodinier, J.M. Dautria, and F. Gervilla, The Recrystallization Front of the Ronda Peridotite: Evidence for Melting and Thermal Erosion of Subcontinental Lithospheric Mantle beneath the Alboran Basin. Journal of Petrology, 2001. 42(1): p. 141-158. 3. Garrido, C.J., F. Gueydan, G. Booth-Rea, J. Precigout, K. Hidas, J.A. Padrón-Navarta, and C. Marchesi, Garnet lherzolite and garnet-spinel mylonite in the Ronda peridotite: Vestiges of Oligocene backarc mantle lithospheric extension in the western Mediterranean. Geology, 2011. 4. Balanyá, J.C., V. García-Dueñas, J.M. Azañón, and M. Sánchez-Gómez, Alternating contractional and extensional events in the Alpujarride nappes of the Alboran Domain (Betics, Gibraltar Arc). Tectonics, 1997. 16(2): p. 226-238. 5. Platt, J

  17. The interplay between tectonics, sediment dynamics and gateways evolution in the Danube system from the Pannonian Basin to the western Black Sea.

    PubMed

    Matenco, Liviu; Munteanu, Ioan; ter Borgh, Marten; Stanica, Adrian; Tilita, Marius; Lericolais, Gilles; Dinu, Corneliu; Oaie, Gheorghe

    2016-02-01

    Understanding the natural evolution of a river-delta-sea system is important to develop a strong scientific basis for efficient integrated management plans. The distribution of sediment fluxes is linked with the natural connection between sediment source areas situated in uplifting mountain chains and deposition in plains, deltas and, ultimately, in the capturing oceans and seas. The Danube River-western Black Sea is one of the most active European systems in terms of sediment re-distribution that poses significant societal challenges. We aim to derive the tectonic and sedimentological background of human-induced changes in this system and discuss their interplay. This is obtained by analysing the tectonic and associated vertical movements, the evolution of relevant basins and the key events affecting sediment routing and deposition. The analysis of the main source and sink areas is focused in particular on the Miocene evolution of the Carpatho-Balkanides, Dinarides and their sedimentary basins including the western Black Sea. The vertical movements of mountains chains created the main moments of basin connectivity observed in the Danube system. Their timing and effects are observed in sediments deposited in the vicinity of gateways, such as the transition between the Pannonian/Transylvanian and Dacian basins and between the Dacian Basin and western Black Sea. The results demonstrate the importance of understanding threshold conditions driving rapid basins connectivity changes superposed over the longer time scale of tectonic-induced vertical movements associated with background erosion and sedimentation. The spatial and temporal scale of such processes is contrastingly different and challenging. The long-term patterns interact with recent or anthropogenic induced modifications in the natural system and may result in rapid changes at threshold conditions that can be quantified and predicted. Their understanding is critical because of frequent occurrence during

  18. Radiocarbon Ages from Two Submerged Strandline Features in the Western Gulf of Maine and a Sea-Level Curve for the Northeastern Massachusetts Coastal Region

    USGS Publications Warehouse

    Oldale, R.N.; Colman, Steven M.; Jones, Glenn A.

    1993-01-01

    New radiocarbon dates provide ages for two submerged strandline features on the Massachusetts inner shelf. These ages provide limited control on a relative sea-level (RSL) curve for the late Wisconsinan and Holocene. The curve indicates a late Wisconsinan high stand of RSL of +33 m about 14,000 yr ago and a very short-lived relative low stand of about -43 m at about 12,000 yr ago followed by a rise to present sea level. Rapid changes of RSL around 12,000 yr ago may be related to changes in global glacial meltwater discharge and eustatic sea-level change shown by dated corals off Barbados. Variations in the magnitude and timing of RSL change from south to north along the coast of the western Gulf of Maine are due to greater crustal depression and later deglaciation to the north.

  19. Interannual variability of the air-sea heat exchange in the western Mediterranean in relation to the deep-water formation processes

    NASA Astrophysics Data System (ADS)

    Soto, J.; Criado Aldeanueva, F.; García Lafuente, J.; Sanchez Román, A.; Carracedo, L.

    2009-04-01

    A 60-year long time series of heat fluxes (long and short wave radiation, sensible and latent contributions) from NCEP reanalysis dataset and a 22-year long time series of Sea Surface Temperature (SST) from JPL AVHRR Oceans Pathfinder dataset have been combined to study the seasonal and interannual variability of air-sea heat exchanges over the Mediterranean Sea and correlate them with the characteristics of the Mediterranean outflow through the Strait of Gibraltar collected in the frame of the INGRES projects in the last years. Special attention has been devoted to the historically reported deep-water formation basin of the Western Mediterranean (Gulf of Lions) during the pre-conditioning (November and December) and winter seasons. Until around 1970, no clear trend is found in the net heat flux winter series since positive and negative anomalies are observed alternatively. From then onwards, negative anomalies are frequently observed until the 2003-2006 positive events. A net heat loss of about 150 W/m2 is observed in 2005, the highest value since 1956, especially due to evaporation losses towards the atmosphere. The anomalously cold air and sea surface temperature in the area help to increase this contribution that reflects in a higher fraction of Western Mediterranean Deep Water (WMDW) in the outflow through the Strait.

  20. Application of satellite remote sensing and eco-hydrodynamic model in environmental and fisheries research in western part of South China Sea

    NASA Astrophysics Data System (ADS)

    van Uu, D.

    The South China Sea (SCS), one of the largest sea in the western part of the Pacific Ocean. This region is most important heat storage of the World Ocean with the highest value of the mean SST. The hydrological and Biological conditions of the South China Sea is principally determined by reversing monsoon winds and has fort seasonal variations. During the south-west monsoon period, from June to September, the upwelling phenomenon is developed and expanded in the western part of SCS. Due to upwelling development, the vulnerability and catch ability of fish stocks in this region is considerably changed. Using AVHRR data (JPL PO.DAAC) and 3D hydrodynamic primitive equation model demonstrated the variation of the upwelling conditions and the role of oceanic structure in the habitat and migration patterns of high migratory pelagic fishes and tuna and tuna-liked species in waters off the coast of Vietnam. The AVHRR data are currently used in research mode to determine possible improvements in prediction of fishing zones by combining these data with CZCS, SeaWiFS data and model simulations.

  1. Role of atmospheric heating over the South China Sea and western Pacific regions in modulating Asian summer climate under the global warming background

    NASA Astrophysics Data System (ADS)

    He, Bian; Yang, Song; Li, Zhenning

    2016-05-01

    The response of monsoon precipitation to global warming, which is one of the most significant climate change signals at the earth's surface, exhibits very distinct regional features, especially over the South China Sea (SCS) and adjacent regions in boreal summer. To understand the possible atmospheric dynamics in these specific regions under the global warming background, changes in atmospheric heating and their possible influences on Asian summer climate are investigated by both observational diagnosis and numerical simulations. Results indicate that heating in the middle troposphere has intensified in the SCS and western Pacific regions in boreal summer, accompanied by increased precipitation, cloud cover, and lower-tropospheric convergence and decreased sea level pressure. Sensitivity experiments show that middle and upper tropospheric heating causes an east-west feedback pattern between SCS and western Pacific and continental South Asia, which strengthens the South Asian High in the upper troposphere and moist convergence in the lower troposphere, consequently forcing a descending motion and adiabatic warming over continental South Asia. When air-sea interaction is considered, the simulation results are overall more similar to observations, and in particular the bias of precipitation over the Indian Ocean simulated by AGCMs has been reduced. The result highlights the important role of air-sea interaction in understanding the changes in Asian climate.

  2. Holocene climate variations in the western Antarctic Peninsula: evidence for sea ice extent predominantly controlled by insolation and ENSO variability changes

    NASA Astrophysics Data System (ADS)

    Etourneau, J.; Collins, L. G.; Willmott, V.; Kim, J. H.; Barbara, L.; Leventer, A.; Schouten, S.; Sinninghe Damsté, J. S.; Bianchini, A.; Klein, V.; Crosta, X.; Massé, G.

    2013-01-01

    The West Antarctic ice sheet is particularly sensitive to global warming and its evolution and impact on global climate over the next few decades remains difficult to predict. In this context, investigating past sea ice conditions around Antarctica is of primary importance. Here, we document changes in sea ice presence, upper water column temperatures (0-200 m) and primary productivity over the last 9000 yr BP (before present) in the western Antarctic Peninsula (WAP) margin from a sedimentary core collected in the Palmer Deep basin. Employing a multi-proxy approach, we derived new Holocene records of sea ice conditions and upper water column temperatures, based on the combination of two biomarkers proxies (highly branched isoprenoid (HBI) alkenes for sea ice and TEXL86 for temperature) and micropaleontological data (diatom assemblages). The early Holocene (9000-7000 yr BP) was characterized by a cooling phase with a short sea ice season. During the mid-Holocene (~ 7000-3000 yr BP), local climate evolved towards slightly colder conditions and a prominent extension of the sea ice season occurred, promoting a favorable environment for intensive diatom growth. The late Holocene (the last ~ 3000 yr) was characterized by more variable temperatures and increased sea ice presence, accompanied by reduced local primary productivity likely in response to a shorter growing season compared to the early or mid-Holocene. The stepwise increase in annual sea ice duration over the last 7000 yr might have been influenced by decreasing mean annual and spring insolation despite an increasing summer insolation. We postulate that in addition to precessional changes in insolation, seasonal variability, via changes in the strength of the circumpolar Westerlies and upwelling activity, was further amplified by the increasing frequency/amplitude of El Niño-Southern Oscillation (ENSO). However, between 4000 and 2100 yr BP, the lack of correlation between ENSO and climate variability in the

  3. Holocene climate variations in the western Antarctic Peninsula: evidence for sea ice extent predominantly controlled by changes in insolation and ENSO variability

    NASA Astrophysics Data System (ADS)

    Etourneau, J.; Collins, L. G.; Willmott, V.; Kim, J.-H.; Barbara, L.; Leventer, A.; Schouten, S.; Sinninghe Damsté, J. S.; Bianchini, A.; Klein, V.; Crosta, X.; Massé, G.

    2013-07-01

    The West Antarctic ice sheet is particularly sensitive to global warming and its evolution and impact on global climate over the next few decades remains difficult to predict. In this context, investigating past sea ice conditions around Antarctica is of primary importance. Here, we document changes in sea ice presence, upper water column temperatures (0-200 m) and primary productivity over the last 9000 yr BP (before present) in the western Antarctic Peninsula (WAP) margin from a sedimentary core collected in the Palmer Deep Basin. Employing a multi-proxy approach, based on the combination of two biomarkers proxies (highly branched isoprenoid (HBI) alkenes for sea ice and TEX86L for temperature) and micropaleontological data (diatom assemblages), we derived new Holocene records of sea ice conditions and upper water column temperatures. The early Holocene (9000-7000 yr BP) was characterized by a cooling phase with a short sea ice season. During the mid-Holocene (~7000-3800 yr BP), local climate evolved towards slightly colder conditions and a prominent extension of the sea ice season occurred, promoting a favorable environment for intensive diatom growth. The late Holocene (the last ~2100 yr) was characterized by warmer temperatures and increased sea ice presence, accompanied by reduced local primary productivity, likely in response to a shorter growing season compared to the early or mid-Holocene. The gradual increase in annual sea ice duration over the last 7000 yr might have been influenced by decreasing mean annual and spring insolation, despite increasing summer insolation. We postulate that, in addition to precessional changes in insolation, seasonal variability, via changes in the strength of the circumpolar Westerlies and upwelling activity, was further amplified by the increasing frequency/amplitude of the El Niño-Southern Oscillation (ENSO). However, between 3800 and 2100 yr BP, the lack of correlation between ENSO and climate variability in the WAP

  4. Eolian depositional phases during the past 50 ka and inferred climate variability for the Pampean Sand Sea, western Pampas, Argentina

    NASA Astrophysics Data System (ADS)

    Tripaldi, Alfonsina; Forman, Steven L.

    2016-05-01

    The Pampean Sand Sea, which occurs from the Argentinian Pampas to the eastern Andean piedmont, hosts presently stabilized dune fields spanning the late Quaternary. This study integrates previous results and presents new geomorphic, stratigraphic, sedimentological, and chronologic data for nineteen >2 m-thick eolian successions for the San Luis paleo-dune field, western Pampas, to better constrain the depositional history. Six eolian depositional phases are identified spanning the past 50 ka, interposed with paleosols and/or bounded by erosive surfaces. Age control was from 61 OSL ages of small aliquots of quartz grains from eolian stratigraphic units. The inferred timing of eolian phases are at ca. 70 ± 10 yr, 190 ± 20 yr, 12 to 1 ka, 22 to 17 ka, 29 to 24 ka, and 40 to 32 ka. A maximum span for periods of pedogenesis at ca. 12 to 17 ka, 22 to 24 ka, and 29 to 32 ka was provided by bounding OSL ages, which broadly overlap with high stands of pluvial lakes and glacier advances in the central Andes. We infer that the added precipitation may reflect expansion of the Southern Hemisphere monsoon, associated with Northern Hemisphere Heinrich events, leading to episodes of significantly wetter conditions (>350 mm MAP) to at least 35° S. Most of the Holocene (12 ka to 0.8 ka) was characterized by sand sheet deposit under drier than present conditions (100-450 mm MAP), associated with Monte-type vegetation (shrub steppe). The latest two eolian depositional phases, occurred at ca. 190 and 70 yr ago, during the historic period with European settlement and are related to anthropogenic landscape disturbance, though the youngest phase was concomitant with 1930s drought. Wet conditions dominated since ca. AD 1970 with new lakes and rivers forming across this eolian terrain; an incongruous environmental response in reference to drier conditions for most of the Holocene.

  5. Depth-related trends in morphological and functional diversity of demersal fish assemblages in the western Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Farré, Marc; Tuset, Víctor M.; Cartes, Joan E.; Massutí, Enric; Lombarte, Antoni

    2016-09-01

    The morphological and functional traits of fishes are key factors defining the ecological and biological habits of species within ecosystems. However, little is known about how the depth gradient affects these factors. In the present study, several demersal fish assemblages from the Balearic Islands (western Mediterranean Sea) along a wide depth range (40-2200 m) were morphologically, functionally and ecologically described. The morphological characterization of communities was performed using geometric morphometric methods, while the functional structures were obtained by the functional categorization of species and the application of principal coordinates analysis (PCoA). The results revealed that morphospaces presented less richness of body forms as depth increases, although they showed a progressive spreading of species toward the periphery, with a proliferation of more extreme body traits, demonstrating lower morphological redundancy. In addition, a trend toward the elongation of body shape was also observed with depth. Moreover, functional diversity increased with bathymetry up to 1400 m, where it sharply decreased downwards. This decrease was parallel to a progressive fall of H‧ (ecological diversity) up to 2200 m. Functional redundancy progressively decreased until the deepest assemblage (more constantly in the deeper levels), which was almost exclusively dominated by benthopelagic wandering species feeding on suprabenthos. Redundancy analysis (RDA) demonstrated that both morphological and functional spaces showed high variation along the bathymetric range. Mantel test indicated that the majority of species presented similar spatial distribution within the morphospace and functional space, although in the functional space the more abundant species were always located at the periphery. These results demonstrate that the assessment of the morpho-functional variation between marine communities helps to understand the processes that affect the structure and

  6. Biomarker-derived phytoplankton community for summer monsoon reconstruction in the western South China Sea over the past 450 ka

    NASA Astrophysics Data System (ADS)

    Li, Li; Li, Qianyu; He, Juan; Wang, Hui; Ruan, Yanming; Li, Jianru

    2015-12-01

    Marine algal-derived lipid biomarkers (alkenones, brassicasterol, dinosterol, and long-chain diol/keto-ol representing haptophytes, diatoms, dinoflagellates, and eustigmatophytes, respectively) were used to evaluate the phytoplankton productivity and community structure changes in core MD05-2901 from the western South China Sea, which features distinct summer upwelling induced by southwest Asian monsoon. The results revealed substantial differences in the distribution patterns between the four major marine primary producers. Diatom and dinoflagellate biomarkers displayed slightly higher abundances, mostly in interglacials especially after MIS 8, while alkenones exhibited lower values in MIS 12 and MIS 1, with higher values in between especially in the middle of MIS 7, but eustigmatophytes increased in most glaciations, indicating complex responses of different phytoplanktons to paleoclimatic and paleoenvironmental changes over the past 450 ka. The sum of the four phytoplanktons shows subtle glacial-interglacial patterns, probably reflecting the combined hydrological dynamics driven by enhanced summer monsoon during summer/interglacials and enhanced winter monsoon during winter/glacials in the region. The biomarker-based community structure showed relative high contribution from diatoms and dinoflagellates during interglacials, high contribution in the middle part of the section centered at ~210 ka from the coccolithophorids, but varying levels from the eustigmatophytes with high percentages in most glacials. Diatoms show strong nutrient sensitivity and positive relation with other paleo-proxies, and their enrichments during interglacials can be attributed to enhanced nutrient level induced by the East Asian summer monsoon, which could have been coupled with the influence of the global ice volume, the summer insolation and the Southern Hemisphere latent heat.

  7. Sediment-water exchange of nutrients in the Marsdiep basin, western Wadden Sea: Phosphorus limitation induced by a controlled release?

    NASA Astrophysics Data System (ADS)

    Leote, Catarina; Epping, Eric H. G.

    2015-01-01

    To quantify the release of inorganic phosphorus from the sediments and assess its contribution to present primary production, a basin-wide study of the Marsdiep (western Wadden Sea, The Netherlands) was performed. Two distinct sedimentary zones were identified: a depositional area characterized by a high content of silt and organic carbon and a small grain size and the majority of the area, composed of fine/medium sand and a low organic carbon content. The sediment-water exchange was higher in the fine grained depositional area and based on a relationship found between the release of inorganic phosphorus and the silt content, a total annual release of 1.0×107 mol P was estimated for the whole Marsdiep basin. A spatial variability in the processes controlling the nutrient release was found. The exchange in the depositional area resulted mainly from molecular diffusive transport, with mineralization and sorption determining the concentration of inorganic phosphorus in the porewater. For the coarser sediment stations the activity of macrofauna clearly enhanced the fluxes. Given the relative demand of nutrients (N:P:Si) for phytoplankton growth, the release was phosphorus deficient during most of the year. Nevertheless, it increased from February until September, in parallel with the increase in temperature and light, thus having the potential to fuel primary production during their seasonal growth period. In terms of absolute values, our results show that the present exchange, enhanced by the activity of macrofauna has the potential to fuel a significant fraction of the recent levels of primary productivity.

  8. Physical-Biological Coupling in the Western South China Sea: The Response of Phytoplankton Community to a Mesoscale Cyclonic Eddy.

    PubMed

    Wang, Lei; Huang, Bangqin; Chiang, Kuo-Ping; Liu, Xin; Chen, Bingzhang; Xie, Yuyuan; Xu, Yanping; Hu, Jianyu; Dai, Minhan

    2016-01-01

    It is widely recognized that the mesoscale eddies play an important part in the biogeochemical cycle in ocean ecosystem, especially in the oligotrophic tropical zones. So here a heterogeneous cyclonic eddy in its flourishing stage was detected using remote sensing and in situ biogeochemical observation in the western South China Sea (SCS) in early September, 2007. The high-performance liquid chromatography method was used to identify the photosynthetic pigments. And the CHEMical TAXonomy (CHEMTAX) was applied to calculate the contribution of nine phytoplankton groups to the total chlorophyll a (TChl a) biomass. The deep chlorophyll a maximum layer (DCML) was raised to form a dome structure in the eddy center while there was no distinct enhancement for TChl a biomass. The integrated TChl a concentration in the upper 100 m water column was also constant from the eddy center to the surrounding water outside the eddy. However the TChl a biomass in the surface layer (at 5 m) in the eddy center was promoted 2.6-fold compared to the biomass outside the eddy (p < 0.001). Thus, the slight enhancement of TChl a biomass of euphotic zone integration within the eddy was mainly from the phytoplankton in the upper mixed zone rather than the DCML. The phytoplankton community was primarily contributed by diatoms, prasinophytes, and Synechococcus at the DCML within the eddy, while less was contributed by haptophytes_8 and Prochlorococcus. The TChl a biomass for most of the phytoplankton groups increased at the surface layer in the eddy center under the effect of nutrient pumping. The doming isopycnal within the eddy supplied nutrients gently into the upper mixing layer, and there was remarkable enhancement in phytoplankton biomass at the surface layer with 10.5% TChl a biomass of water column in eddy center and 3.7% at reference stations. So the slight increasing in the water column integrated phytoplankton biomass might be attributed to the stimulated phytoplankton biomass at the

  9. Physical-Biological Coupling in the Western South China Sea: The Response of Phytoplankton Community to a Mesoscale Cyclonic Eddy

    PubMed Central

    Wang, Lei; Huang, Bangqin; Chiang, Kuo-Ping; Liu, Xin; Chen, Bingzhang; Xie, Yuyuan; Xu, Yanping; Hu, Jianyu; Dai, Minhan

    2016-01-01

    It is widely recognized that the mesoscale eddies play an important part in the biogeochemical cycle in ocean ecosystem, especially in the oligotrophic tropical zones. So here a heterogeneous cyclonic eddy in its flourishing stage was detected using remote sensing and in situ biogeochemical observation in the western South China Sea (SCS) in early September, 2007. The high-performance liquid chromatography method was used to identify the photosynthetic pigments. And the CHEMical TAXonomy (CHEMTAX) was applied to calculate the contribution of nine phytoplankton groups to the total chlorophyll a (TChl a) biomass. The deep chlorophyll a maximum layer (DCML) was raised to form a dome structure in the eddy center while there was no distinct enhancement for TChl a biomass. The integrated TChl a concentration in the upper 100 m water column was also constant from the eddy center to the surrounding water outside the eddy. However the TChl a biomass in the surface layer (at 5 m) in the eddy center was promoted 2.6-fold compared to the biomass outside the eddy (p < 0.001). Thus, the slight enhancement of TChl a biomass of euphotic zone integration within the eddy was mainly from the phytoplankton in the upper mixed zone rather than the DCML. The phytoplankton community was primarily contributed by diatoms, prasinophytes, and Synechococcus at the DCML within the eddy, while less was contributed by haptophytes_8 and Prochlorococcus. The TChl a biomass for most of the phytoplankton groups increased at the surface layer in the eddy center under the effect of nutrient pumping. The doming isopycnal within the eddy supplied nutrients gently into the upper mixing layer, and there was remarkable enhancement in phytoplankton biomass at the surface layer with 10.5% TChl a biomass of water column in eddy center and 3.7% at reference stations. So the slight increasing in the water column integrated phytoplankton biomass might be attributed to the stimulated phytoplankton biomass at the

  10. Comparing the Gibraltar and Calabrian subduction zones (central western Mediterranean) based on seismic tomography

    NASA Astrophysics Data System (ADS)

    Argnani, Andrea; Battista Cimini, Giovanni; Frugoni, Francesco; Monna, Stephen; Montuori, Caterina

    2016-04-01

    The Central Western Mediterranean (CWM) was shaped by a complex tectonic and geodynamic evolution. Deep seismicity and tomographic studies point to the existence, under the Alboran and Tyrrhenian Seas, of lithospheric slabs extending down to the bottom of the mantle transition zone, at 660 km depth. Two narrow arcs correspond to the two slabs, the Gibraltar and Calabrian Arcs (e.g., Monna et al., 2013; Montuori et al., 2007). Similarities in the tectonic and mantle structure of the two areas have been explained by a common subduction and roll-back mechanism for the opening of the CWM, in which the two arcs are symmetrical end products. In spite of this unifying model, a wide amount of literature from different disciplines shows that many aspects of the two areas are still controversial. We present a new 3-D tomographic model at mantle scale for the Calabrian Arc and compare it with a recently published 3-D tomographic model for the Gibraltar Arc by Monna et al (2013). The two models are based on non-linear inversion of teleseismic phase arrivals, and have scale and parametrization that allow for a direct comparison. Unlike previous studies the tomographic models here presented include Ocean Bottom Seismometer broadband data, which improved the resolution of the mantle structures in the marine areas surrounding the arcs. We focus on key features of the two models that constrain reconstructions of the geodynamic evolution of the CWM (e.g., Monna et al., 2015). At Tortonian time the opening of the Tyrrhenian basin was in its initial stage, and the Calabrian arc formed subsequently; on the contrary, the Gibraltar arc was almost completely defined. We hypothesize that the complexity of the continental margin approaching the subduction zone played a key role during the final stages of the arc formation. References Monna, S., G. B. Cimini, C. Montuori, L. Matias, W. H. Geissler, and P. Favali (2013), New insights from seismic tomography on the complex geodynamic evolution

  11. Relations between tectonics and sedimentation along the Eastern Sardinian margin (Western Tyrrhenian Sea) : from rifting to reactivation

    NASA Astrophysics Data System (ADS)

    Gaullier, Virginie; Chanier, Frank; Vendeville, Bruno; Lymer, Gaël; Maillard, Agnès; Thinon, Isabelle; Lofi, Johanna; Sage, Françoise; Giresse, Pierre; Bassetti, Maria-Angela

    2014-05-01

    The offshore-onshore project "METYSS-METYSAR" aims at better understand the Miocene-Pliocene relationships between crustal tectonics, salt tectonics, and sedimentation along the Eastern Sardinian margin, Western Tyrrhenian Sea. In this key-area, the Tyrrhenian back-arc basin underwent recent rifting (9-5 Ma), pro parte coeval with the Messinian Salinity Crisis (MSC, 5.96-5.33 Ma), sea-floor spreading starting during Pliocene times. Thereby, the Tyrrhenian basin and the Eastern Sardinian margin are excellent candidates for studying the mechanisms of extreme lithospheric stretching and thinning, the role of pre-existing structural fabric during and after rifting, and the reactivation of a passive margin and the associated deformation and sedimentation patterns during the MSC. We looked at the respective contributions of crustal and salt tectonics in quantifying vertical and horizontal movements, using especially the seismic markers of the MSC. Overall, we delineate the history of rifting and tectonic reactivation in the area. The distribution maps respectively of the Messinian Erosion Surface and of Messinian units (Upper Unit and Mobile Unit) show that a rifted basin already existed by Messinian time. This reveals a major pre-MSC rifting across the entire domain. Because salt tectonics can create fan-shaped geometries in sediments, syn-rift deposits have to be carefully re-examined in order to decipher the effects of crustal tectonics (rifting) and thin-skinned salt tectonics. Our data surprisingly show that there are no clues for Messinian syn-rift sediments along the East-Sardinia Basin and Cornaglia Terrace, hence no evidence for rifting after Late Tortonian times. Nevertheless, widespread deformation occurred during the Pliocene and can only be attributed to post-rift reactivation. This reactivation is characterized not only by normal faulting but also by contractional structures. Some Pliocene vertical movements caused localized gravity gliding of the mobile

  12. Improving the study of the seismicity in the western and central parts of the Sea of Marmara using Ocean Bottom Seismometers

    NASA Astrophysics Data System (ADS)

    Cros, Estelle; Géli, Louis; Bayrakci, Gaye; Cagatay, Namik; Gürbüz, Cemil

    2013-04-01

    The Marmara Sea is located between the Agean Sea and the Black Sea, along the North Anatolian strike-slip fault, which experienced a sixty year sequence of earthquakes since 1940. Prior to this sequence, which ended with the Izmit and Duzce earthquakes in 1999, at the eastern end of the Sea of Marmara (SoM), the fault ruptured to the west in 1912 in Ganos, with an estimated moment magnitude of 7.4. Therefore, a major earthquake is expected within the SoM seismic gap. In order to better understand the seismicity and to reduce the threshold of detection, a network of ten OBS with four components was deployed by Ifremer with R/V Yunus of Istanbul Technical University, in the western and central parts of the Marmara Sea to record the micro-seismicity from the immediate vicinity of the main Marmara Fault, between April and August, 2011. The network was specifically designed to survey the segments crossing the Western High, where gas hydrates where recently found, the Central Basin and the Kumburgaz Basin. During this period more than one hundred earthquakes were detected by the EMSC (European-Mediterranean Seismological Centre) in the Sea of Marmara. Because the basins of the Sea of Marmara are filled with more than 5 km of Plio- Quaternary soft ("slow") sediments, it is of critical importance to take into account the velocity structure of the offshore domain, which is drastically different from the one onshore, and the bathymetry. To improve the localization of seismic events, a 3D velocity model was thus considered and implemented in the Sytmis software developed by INERIS. This model is based on the tomographic data collected in 2001 using a controlled source experiment and on the numerous multichannel seismic profiles that provide information on, respectively, the deeper structures and the upper, sedimentary layers. Preliminary results are presented. Special focus will be given on the clustering of the micro-seismicity in the Western High and on a swarm event. As a

  13. Southern McMurdo Sound Project (SMS- ANDRILL): overview of Mid Miocene Climatic Optima events and correlations in western Ross Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Harwood, D. M.; Florindo, F.; Levy, R. H.; Talarico, F.; Fielding, C.; Fischbein, S.; Sms Science Team

    2009-04-01

    The ANtarctic geological DRILLing Program (ANDRILL), an international collaboration between Antarctic research programs of Germany, Italy, New Zealand and the United States, successfully cored in late 2007 (with 98% recovery) a 1138 meter drill hole that documents an excellent history of high latitude paleoenvironmental conditions and climate/glacial variation during Miocene climatic optimum periods. In addition, fracture mapping, core orientation success, and borehole hydrofracture experiments reveal details regarding the history and current stress regime in the western Ross Sea. We present initial correlations of the AND-2A drillcore to global proxies of sea-level and deep-sea geochemical stratigraphy, guided by a robust chronostrati-graphic framework for the early and middle Miocene. Changes evident in stratigraphic sequences, physical properties (borehole and core), and geochemical logs, record fine details of glacial, climatic, tectonic and eustatic influence in the western Ross Sea help establish through correlation to existing records how local changes evident in the drillcore relate to regional and global events. These records combined with paleontological and geochemical evidence for terrestrial - marine paleotemperatures provide important data input for climate and ice-sheet model reconstructions and testing. An abundance of volcanic materials reveals evolution of the McMurdo Volcanic Group, including episodes of explosive volcanism. Substantial subsidence occurred within the last 2 Ma associated with volcanic loading from Ross Island, reversing the persistent littoral to shallow neritic depths evident through most of the cored sequence. Persistent sediment supply into western Victoria Land Basin during a steady phase of thermal subsidence produced a thick stratigraphic sequence from which we are reconstructing the details of paleoclimatic, eustatic and glacial variations on the shallow marine coast of the Transantarctic Mountains.

  14. Possible Controls on Boron Incorporation in Tests of Planktonic Foraminifera G. ruber in Upwelling Region of the Western Arabian Sea: a Paleoperspective

    NASA Astrophysics Data System (ADS)

    Naik, S. S.; Pothuri, D. N.

    2012-12-01

    In recent times the B/Ca elemental ratio from planktonic foraminifera shells has shown promise as a possible pH proxy (Yu et al 2007). However, studies have further shown that the controls on boron incorporation into foraminifera shells could be other then the seawater pH (Foster 2008; Allen et al 2012). We attempt to utilize this proxy in the intense upwelling region of the western Arabian Sea to understand which factors have dominant control/s on this proxy. The western Arabian Sea upwelling region is known to be an intense source of CO2 to the atmosphere. The intensity of upwelling is also known to be associated with the intensity of monsoon linked through wind strength. We have used a sediment core ODP 723A (18°03N, 57°37E) from a water depth of 808 m, spanning the last 22kyr from the western Arabian Sea. The B/Ca values varied from 123 to 178 μmol/mol with peak value at around 9 kyrs. A comparison with the salinity and temperature calculated using δ18O and Mg/Ca and further comparison with a eastern Arabian Sea core shows that B/Ca proxy is not controlled by salinity or temperature. The B/Ca values however showed a significant correlation with the shell sizes of G. ruber which were seen to increase during 5 to 10 kyr, a period of intense upwelling. This observation suggests that the growth rate of a planktonic foraminifer could be the most important control over the boron incorporation in their shells with higher B/Ca ratios during faster growth period, for example the upwelling period.

  15. Biogeochemistry of lipid biomarkers and pigments in particulate matter from the frontal structure of the Alboran Sea (SW Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Tolosa, I.; Leblond, N.; Vescovali, I.; Copin-Montegut, C.; Marty, J. C.; de Mora, S.; Prieur, L.

    2003-04-01

    The distribution of pigments, and the molecular and isotopic carbon ratios of lipid biomarkers (sterol, fatty alcohol and fatty acids) were used to investigate the different sources and transformation processes of organic matter in the water column of the Almeria-Oran frontal zone. Four sites representative of three different hydrodynamic structures (Mediterranean water, geostrophic Atlantic jet and anticyclonic gyre) were investigated using samples from sediment traps deployed at 100 and 300 m depth and from filtered (0.7 µm) water obtained at depths between 20 to 300 m. In contrast to the relatively fresh sinking particles with elevated concentrations of phyto- and zooplanktonic sterols, suspended particles were extensively degraded with increasing depth and exhibited more terrestrial, bacterial and zooplanktonic character with depth. Whereas diatom-biomarkers predominated in the frontal zone, and in particular in the gyre downstream, flagellate-biomarkers were mainly associated with the suspended particles of the Mediterranean site and gyre upstream of the Atlantic water. Sterol and alcohol biomarkers distributions and 13C values from the jet core and the gyre of Atlantic waters showed a decoupling between the sinking particles of 100 m and 300 m depth, demonstrating the influence of lateral advection in the frontal zone. In contrast, vertical transport of the particulate organic matter in Mediterranean waters was indicated by similar isotopic and molecular composition at both depths. A downwelling of biomass below the euphotic zone on the gyre downstream, due to the effects of the internal secondary circulation, was also observed from the high abundance of phytoplanktonic biomarkers at 100 m depth.

  16. New insights into hydrological exchange between the South China Sea and the Western Pacific Ocean based on the Nd isotopic composition of seawater

    NASA Astrophysics Data System (ADS)

    Wu, Qiong; Colin, Christophe; Liu, Zhifei; Douville, Eric; Dubois-Dauphin, Quentin; Frank, Norbert

    2015-12-01

    Rare Earth Element (REE) concentrations and Nd isotopic compositions (εNd) of 16 seawater profiles collected in the northern South China Sea (SCS) and the Philippine Sea were investigated (1) to establish the distribution of the Nd isotopic composition of water masses along the tropical Western Pacific and the SCS until now underexplored, (2) to constrain hydrological exchanges between the SCS and the Philippine Sea through the Luzon Strait, and (3) to test, in the context of the semi-closed marginal sea (SCS), the possible impact of the process of exchange of Nd between SCS water masses and unradiogenic sediments from its north-western margin. εNd values for mid- and deep-water masses of the Philippine Sea and the SCS range from -2.3 to -4.4 and generally increase slightly as water depth increases. In the Philippine Sea, εNd values for the North Pacific Intermediate Water (NPIW) reach -2.7±0.4 at mid-depths (500 to 1400 m). Below ~1800 m, the Pacific Deep Water (PDW) is characterised by less radiogenic Nd (-4.1±0.5) indicating the intrusion of southern-sourced water. For most of the stations in the Northern SCS, water masses below 1500 m (PDW) display homogenous εNd values (~-4.1) identical to those of the PDW in the Philippine Sea. εNd values for the South China Sea Intermediate Water (SCSIW, 500-1500 m) vary from -3.0 to -3.9 as a result of the vertical mixing of the NPIW with the PDW in the SCS. Seawater εNd values for the SCS display local modification (~-5.3 to -7.0) in areas where water passes above sediment drift deposit systems. This implies locally confined "boundary exchange'' with unradiogenic sediments (around -11) insufficient to alter the Nd isotopic composition of the PDW in the Northern SCS. In addition, εNd values analysed for the first time in nepheloid layers collected along the north-western margin of the SCS do not exhibit any significant modification of the seawater εNd which remains into a narrow range between -3.7 and -4

  17. The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats

    PubMed Central

    Coll, Marta; Piroddi, Chiara; Steenbeek, Jeroen; Kaschner, Kristin; Ben Rais Lasram, Frida; Aguzzi, Jacopo; Ballesteros, Enric; Bianchi, Carlo Nike; Corbera, Jordi; Dailianis, Thanos; Danovaro, Roberto; Estrada, Marta; Froglia, Carlo; Galil, Bella S.; Gasol, Josep M.; Gertwagen, Ruthy; Gil, João; Guilhaumon, François; Kesner-Reyes, Kathleen; Kitsos, Miltiadis-Spyridon; Koukouras, Athanasios; Lampadariou, Nikolaos; Laxamana, Elijah; López-Fé de la Cuadra, Carlos M.; Lotze, Heike K.; Martin, Daniel; Mouillot, David; Oro, Daniel; Raicevich, Saša; Rius-Barile, Josephine; Saiz-Salinas, Jose Ignacio; San Vicente, Carles; Somot, Samuel; Templado, José; Turon, Xavier; Vafidis, Dimitris; Villanueva, Roger; Voultsiadou, Eleni

    2010-01-01

    Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well. This abstract has been translated to other languages (File S1). PMID:20689844

  18. The biodiversity of the Mediterranean Sea: estimates, patterns, and threats.

    PubMed

    Coll, Marta; Piroddi, Chiara; Steenbeek, Jeroen; Kaschner, Kristin; Ben Rais Lasram, Frida; Aguzzi, Jacopo; Ballesteros, Enric; Bianchi, Carlo Nike; Corbera, Jordi; Dailianis, Thanos; Danovaro, Roberto; Estrada, Marta; Froglia, Carlo; Galil, Bella S; Gasol, Josep M; Gertwagen, Ruthy; Gil, João; Guilhaumon, François; Kesner-Reyes, Kathleen; Kitsos, Miltiadis-Spyridon; Koukouras, Athanasios; Lampadariou, Nikolaos; Laxamana, Elijah; López-Fé de la Cuadra, Carlos M; Lotze, Heike K; Martin, Daniel; Mouillot, David; Oro, Daniel; Raicevich, Sasa; Rius-Barile, Josephine; Saiz-Salinas, Jose Ignacio; San Vicente, Carles; Somot, Samuel; Templado, José; Turon, Xavier; Vafidis, Dimitris; Villanueva, Roger; Voultsiadou, Eleni

    2010-01-01

    Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well. This abstract has been translated to other languages (File S1). PMID:20689844

  19. Tectonic controls on the quality and distribution of Syn- to Post-Rift reservoir sands in the Southern Red Sea, offshore Western Yemen

    SciTech Connect

    Carter, J.M.L.

    1995-08-01

    Previous geophysical and drilling results in the southern Red Sea, and the presence of numerous oil seeps, indicate that the syn- to post-rift section is prospective for oil and gas. The relatively high geothermal gradient offshore western Yemen makes intra-salt and post-salt reservoir sands the only viable exploration targets. The quality and distribution of the reservoir sands remains one of the main unknown risk factors, An improved understanding of the controls on deposition of these sands is achieved by use of LandSat data, which provide evidence of a regional tectonic framework involving NE/SW-trending oceanic transform faults which are expressed onshore as strike-slip features, in some cases representing reactivated Precambrian lineaments. These faults are thought to have played two fundamental roles in the Neogene to Recent evolution of the southern Red Sea - firstly by directing clastic input from the rising Yemen Highlands into offshore depocentres, and secondly by influencing the location of salt diapirs sourced by Upper Miocene evaporates. By considering these factors, together with the pattern of heat flow from the developing oceanic rift of the southern Red Sea, it is possible to delineate areas of offshore western Yemen where reservoir characteristics are likely to be most favourable.

  20. Contrasting records of sea-level change in the eastern and western North Atlantic during the last 300 years

    NASA Astrophysics Data System (ADS)

    Long, A. J.; Barlow, N. L. M.; Gehrels, W. R.; Saher, M. H.; Woodworth, P. L.; Scaife, R. G.; Brain, M. J.; Cahill, N.

    2014-02-01

    We present a new 300-year sea-level reconstruction from a salt marsh on the Isle of Wight (central English Channel, UK) that we compare to other salt-marsh and long tide-gauge records to examine spatial and temporal variability in sea-level change in the North Atlantic. Our new reconstruction identifies an overall rise in relative sea level (RSL) of c. 0.30 m since the start of the eighteenth century at a rate of 0.9±0.3 mm yr. Error-in-variables changepoint analysis indicates that there is no statistically significant deviation from a constant rate within the dataset. The reconstruction is broadly comparable to other tide-gauge and salt-marsh records from the European Atlantic, demonstrating coherence in sea level in this region over the last 150-300 years. In contrast, we identify significant differences in the rate and timing of RSL with records from the east coast of North America. The absence of a strong late 19th/early 20th century RSL acceleration contrasts with that recorded in salt marsh sediments along the eastern USA coastline, in particular in a well-dated and precise sea-level reconstruction from North Carolina. This suggests that this part of the North Carolina sea level record represents a regionally specific sea level acceleration. This is significant because the North Carolina record has been used as if it were globally representative within semi-empirical parameterisations of past and future sea-level change. We conclude that regional-scale differences of sea-level change highlight the value of using several, regionally representative RSL records when calibrating and testing semi-empirical models of sea level against palaeo-records. This is because by using records that potentially over-estimate sea-level rise in the past such models risk over-estimating sea-level rise in the future.

  1. Sediment dispersal system in the Taiwan-South China Sea collision zone along a convergent margin: A comparison with the Papua New Guinea collision zone of the western Solomon Sea

    NASA Astrophysics Data System (ADS)

    Hsiung, Kan-Hsi; Yu, Ho-Shing

    2013-01-01

    Through a large-scale examination of the morpho-sedimentary features on sea floors in the Taiwan-Luzon convergent margin, we determined the main sediment dispersal system which stretches from 23°N to 20°N and displays as an aligned linear sediment pathway, consisting of the Penghu Canyon, the deep-sea Penghu Channel and northern Manila Trench. The seafloor of South China Sea north of 21°N are underlain by a triangle-shaped collision marine basin, resulting from oblique collision between the