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Sample records for arabian sea

  1. Wave Clouds over the Arabian Sea

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Like a massive, ethereal bird gliding into the Persian Gulf, a large cluster of wave clouds spans the Arabian Sea from Oman to India. This cloud formation is likely an undular bore, which is created in the interaction between the cool, dry air in a low-pressure system with a stable layer of warm, moist air. In this case, a low-pressure system probably sits over the Arabian Peninsula, the Gulf of Oman, and Iran and Pakistan. The strong winds generated by the low-pressure system are kicking up clouds of dust from Iran and Pakistan, and, to a lesser degree, Oman. The low-pressure system is also pushing air south-southeast, and this south-moving wave of displaced air pushes ahead of the low-pressure system like a mound of water moving ahead of a boat in calm water. The wave of cool, dry air pushes forward until it meets the wall of warm, moist air that blankets the Arabian Sea. When the two air masses clash, the cool air pushes the warm air up. The warm air rises, cools at the peak of the wave, falls again, and then rises to a slightly lower peak, and so forth, until the wave dissipates. Clouds form at the high-altitude peaks of the waves, with the most defined cloud at the front of the group, where the initial wave formed, followed by increasingly less-defined lines of cloud. The air that moves in front of the low-pressure system does not push forward in a uniform wall; instead it pushes forward in a ragged band, with one part racing ahead of another, like a line of crew racers on a river. Because the air is not uniform, there are small, interacting arcs of waves within the larger band of clouds. Undular bores are rare and hard to predict. This particular undular bore formed over the Arabian Sea on May 8, 2007, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite captured this photo-like image. Typical undular bore patterns might display one or two rows of clouds. With more than thirty waves of clouds, this cloud pattern is unusually

  2. Salinity pathways between Arabian Sea and Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Krishna Kailasam, Muni

    2016-07-01

    Surface as well as subsurface salinity are highly heterogeneous in the Arabian Sea and the Bay of Bengal. Due to the strong seasonal reversal of currents in the two seas tremendous salt exchange occurred. The present study focuses on the exchange of salt between the Arabian Sea and Bay of Bengal by using remote sensing observations like SMOS and Aquarius. Inflow of high salinity water from the central Arabians Sea into the south Bay of Bengal is significant and occurs during August-September. Freshwater transport out of the Bay of Bengal is southward throughout the year along the along the east coast of the Indian sub-continent. Only a small fraction of low salinity water is advected into the eastern Arabian Sea from the Bay of Bengal. The pathways of salinity between the two seas are also examined using SODA data. It shows that relatively low salinity Bay of Bengal water is transported southward across the equator throughout the year. A considerable southward cross-equatorial exchange of Arabian Sea water occurs during the southwest monsoon season.

  3. Cabled ocean observatories in Sea of Oman and Arabian Sea

    NASA Astrophysics Data System (ADS)

    DiMarco, Steven F.; Wang, Zhankun; Jochens, Ann; Stoessel, Marion; Howard, Matthew K.; Belabbassi, Leila; Ingle, Stephanie; du Vall, Ken

    2012-07-01

    An ocean observatory—consisting of a real-time, cabled array in the Sea of Oman and an internally recording, autonomous mooring array recently upgraded to a cabled array in the northern Arabian Sea—celebrated more than 2500 days of continuous operation in July 2012. The observatory, which measures a range of properties, such as water current velocities, temperature, salinity, pressure, dissolved oxygen, and turbidity, is part of the Lighthouse Ocean Research Initiative (LORI) project [du Vall et al., 2011], which was designed as a pilot project and installed in 2005 in the region off Abu Bakara (Figures 1a and 1b). The initial goal of the project was to prove that an in situ, cabled ocean observatory can return high-quality scientific data on a real-time basis over longer time periods than conventional moored systems. That same year, an autonomous array was deployed off Ras al Hadd and on Murray Ridge in the Arabian Sea (Figure 1a).

  4. Marine geology and oceanography of Arabian Sea and coastal Pakistan

    SciTech Connect

    Haq, B.U.; Milliman, J.D.

    1985-01-01

    This volume is a collection of papers presented at the first US-Pakistan workshop in marine science held in Karachi, Pakistan, in November 1982. Of the twenty-four contributions in this book, fourteen cover topics specific to the Arabian Sea-coastal Pakistan region. These include six papers on the geology, tectonics, and petroleum potential of Pakistan, four papers on sedimentary processes in the Indus River delta-fan complex, and four papers on the biological oceanography of the Arabian Sea and coastal Pakistan. The additional ten papers are overviews of shelf sedimentation processes, paleoceanography, the marine nutrient cycle, and physical and chemical oceanography.

  5. Remotely Searching for Noctiluca Miliaris in the Arabian Sea

    NASA Technical Reports Server (NTRS)

    Werdell, P. Jeremy; Roesler, Collin S.; Goes, Joaquim I.

    2014-01-01

    Reversing monsoonal winds in the Arabian Sea result in two seasons with elevated biological activity, namely the annual summer Southwest Monsoon (SWM; June to September) and winter Northeast Monsoon (NEM; November to March) [Wiggert et al., 2005]. Generally speaking, the SWM and NEM create two geographically distinct blooms [Banse and English, 2000; Levy et al., 2007]. In the summer, winds from the southwest drive offshore Ekman transport and coastal upwelling along the northwestern coast of Africa, which brings nutrient-rich water to the surface from below the permanent thermocline [Bauer et al., 1991]. In the winter, cooling of the northern Arabian Sea causes surface waters to sink, which generates convective mixing that injects nutrients throughout the upper mixed layer [Madhupratap et al., 1996]. This fertilization of otherwise nutrient-deplete surface waters produces one of the most substantial seasonal extremes of phytoplankton biomass and carbon flux anywhere in the world [Smith, 2005].

  6. Biological control of surface temperature in the Arabian Sea

    NASA Technical Reports Server (NTRS)

    Sathyendranath, Shubha; Gouveia, Albert D.; Shetye, Satish R.; Ravindran, P.; Platt, Trevor

    1991-01-01

    In the Arabian Sea, the southwest monsoon promotes seasonal upwelling of deep water, which supplies nutrients to the surface layer and leads to a marked increase in phytoplankton growth. Remotely sensed data on ocean color are used here to show that the resulting distribution of phytoplankton exerts a controlling influence on the seasonal evolution of sea surface temperature. This results in a corresponding modification of ocean-atmosphere heat exchange on regional and seasonal scales. It is shown that this biological mechanism may provide an important regulating influence on ocean-atmosphere interactions.

  7. Indian Ocean Dipole modulated wave climate of eastern Arabian Sea

    NASA Astrophysics Data System (ADS)

    Anoop, T. R.; Sanil Kumar, V.; Shanas, P. R.; Johnson, G.; Amrutha, M. M.

    2015-10-01

    Intrinsic modes of variability have a significant role in driving climatic oscillations in the ocean. In this paper, we investigate the influence of inter-annual variability, the Indian Ocean Dipole (IOD), on the wave climate of the eastern Arabian Sea (AS). Using measured, modeled and reanalysis wave data and reanalysis wind data, we show that the IOD plays a major role in the variability of wave climate of the study region due to the IOD induced changes in equatorial sea surface temperature and sea level pressure. Inter-annual variability in the wave climate over the eastern AS during the IOD is due to the modification of winds from the northern AS. The change in wind field over the AS due to IOD influences the generation or dissipation of wave field and hence causes the decrease in northwest short period waves during positive IOD and increase during negative IOD.

  8. Indian Ocean Dipole modulated wave climate of eastern Arabian Sea

    NASA Astrophysics Data System (ADS)

    Anoop, T. R.; Sanil Kumar, V.; Shanas, P. R.; Glejin, J.; Amrutha, M. M.

    2016-03-01

    Intrinsic modes of variability have a significant role in driving the climatic oscillations in the oceanic processes. In this paper, we investigate the influence of an inter-annual mode of variability, the Indian Ocean Dipole (IOD), on the wave climate of the eastern Arabian Sea (AS). Using measured, modeled and reanalysis wave data and reanalysis wind data, we show that the IOD plays a major role in the variability of wave climate of the study region. Due to the IOD-induced changes in equatorial sea surface temperature and sea level pressure, the winds from the northern AS gets modified and cause inter-annual variability in the wave climate over the eastern AS. The changes in wind field over the AS due to the IOD influence the generation or dissipation of the wave field and hence cause a decrease in northwest short-period waves during positive IOD and an increase during negative IOD.

  9. Carbon fluxes in the Arabian Sea: Export versus recycling

    NASA Astrophysics Data System (ADS)

    Rixen, Tim; Gaye, Birgit; Ramaswamy, Venkitasubramani

    2016-04-01

    The organic carbon pump strongly influences the exchange of carbon between the ocean and the atmosphere. It is known that it responds to global change but the magnitude and the direction of change are still unpredictable. Sediment trap experiments carried out at various sites in the Arabian Sea between 1986 and 1998 have shown differences in the functioning of the organic carbon pump (OCP). An OCP driven by eukaryotic phytoplankton operated in the upwelling region off Oman and during the spring bloom in the northern Arabian Sea. Cyanobacteria capable of fixing nitrogen seem to dominate the phytoplankton community during all other seasons. The export driven by cyanobacteria was much lower than the export driven by eukaryotic phytoplankton. Productivity and nutrient availability seems to be a main factor controlling fluxes during blooms of eukaryotic phytoplankton. The ballast effect caused by inputs of dust into the ocean and its incorporation into sinking particles seems to be the main factor controlling the export during times when cyanobacteria dominate the phytoplankton community. C/N ratios of organic matter exported from blooms dominated by nitrogen fixing cyanobacteria are enhanced and, furthermore, indicate a more efficient recycling of nutrients at shallower water depth. This implies that the bacterial-driven OCP operates more in a recycling mode that keeps nutrients closer to the euphotic zone whereas the OCP driven by eukaryotic phytoplankton reduces the recycling of nutrients by exporting them into greater water-depth.

  10. The relationship between Arabian Sea upwelling and Indian Monsoon revisited

    NASA Astrophysics Data System (ADS)

    Yi, Xing; Zorita, Eduardo; Hünicke, Birgit

    2015-04-01

    Coastal upwelling is important to marine ecosystems and human activities. It transports nutrient-rich deep water mass that supports marine biological productivity. In this study, we aim to characterize the large-scale climate forcings that drive upwelling along the western Arabian Sea coast. Studies based on ocean sediments suggest that there is a link between this coastal upwelling system and the Indian summer monsoon. However, a more direct method is needed to examine the influence of various forcings on upwelling. For this purpose, we analyse a high-resolution (about 10 km) global ocean simulation (denoted STORM), which is based on the MPI-OM model developed by the Max-Planck-Institute for Meteorology in Hamburg driven by the global meteorological reanalysis NCEP over the period 1950-2010. This very high spatial resolution allows us to identify characteristics of the coastal upwelling system. We compare the simulated upwelling velocity of STORM with two traditional upwelling indices: along-shore wind speed and sea surface temperature. The analysis reveals good consistency between these variables, with high correlations between coastal upwelling and along-shore wind speed (r=0.85) as well as coastal sea surface temperature (r=-0.77). To study the impact of the monsoon on the upwelling we analyse both temporal and spatial co-variability between upwelling velocity and the Indian summer monsoon index. The spatial analysis shows that the impact of the monsoon on the upwelling is concentrated along the coast, as expected. However, somewhat unexpectedly, the temporal correlation between the coastal upwelling and the monsoon index is rather weak (r=0.26). Also, the spatial structure of upwelling in the Arabian Sea as revealed by a Principal Component Analysis is rather rich, indicating that factors other than the Monsoon are also important drivers of upwelling. In addition, no detectable trend in our coastal upwelling is found in the simulation that would match the

  11. Demersal Fisheries of the Arabian Sea, the Gulf of Oman and the Arabian Gulf

    NASA Astrophysics Data System (ADS)

    Siddeek, M. S. M.; Fouda, M. M.; Hermosa, G. V.

    1999-08-01

    The demersal fisheries of the Arabian Sea, the Gulf of Oman and the Arabian Gulf are reviewed. The region comprises eight countries: Oman, United Arab Emirates (U.A.E.), Qatar, Saudi Arabia, Bahrain, Kuwait, Iraq and Iran. Over 350 commercial fish species, eight shrimp species, two spiny lobster species, one shovel nose lobster species, one cuttlefish species, one crab species, and one abalone species support the demersal fisheries in the continental shelves of the three regions. Artisanal and industrial vessels with over 120 000 fishermen were involved in demersal fisheries. Fishing boats include fish and shrimp trawlers (wooden and steel hulled), large wooden boats (dhow) with inboard engines, small dhows with outboard engines, and fibreglass boats. Fishing gear consists of trawls, bottom gill nets, traps (wire mesh and plastic types), barrier traps, hand lines, and bare hands and knives (to dislodge abalone). Demersal fish (primarily Lethrinidae, Sparidae, Serranidae, Siganidae, Sciaenidae, Stromateidae, Lutjanidae, Trichiuridae, and Nemipteridae) and shrimp (primarily Penaeus semisulcatus, Metapenaeus affinis, Parapenaeopsis stylifera, and Penaeus merguiensis) were the two commercial demersal resources. Approximately 198 000-214 000 tonnes (t) of demersals were landed annually during 1988-1993, accounting for nearly 40% of the total marine landings (475 000-552 000 t). This percentage, however varied among countries: 25% in Oman, 32% in U.A.E., 71% in Qatar, 52% in Saudi Arabia, 56% in Bahrain, 55% in Kuwait, close to 100% in Iraq, and 41% in Iran. Fishing effort on certain stocks may have been below the optimum level (e.g. certain Omani demersal fish), near the optimum level (e.g. Omani shrimp), or above the optimum level (e.g. Arabian Gulf shrimp and demersal fish). Overexploitation led to restriction of fishing effort by limiting fishing licences, regulating fishing gear (mesh size) and capture size, closing fishing areas, restricting fishing season, and

  12. The Tectonic and Climatic Evolution of the Arabian Sea Region

    NASA Astrophysics Data System (ADS)

    Bosence, Dan

    2004-08-01

    This multi-authored volume provides a sampling of current research into the geology of the Arabian Sea region. The editors emphasize the importance of this area as the Earth's best natural laboratory for studying relations between climate and the growth and erosion of an orogenic belt. Uplift of the Himalaya and Tibetan Plateau is now believed to have altered global climate during the Cenozoic, and also to have affected the development of the region's monsoonal climate. The geological features of the region that make it a good area to study such processes include the excellent rock outcrops in the surrounding arid Arabian and Asian landmasses, the locally high rates of sedimentation which provide high-resolution sedimentological and geochemical information, and the monsoon itself, that imparts an annual time beat in some sedimentary successions. However, the region is very large and access is not always easy. Also, many areas are still poorly known geologically, such that this volume contains some papers on basic survey geology.

  13. The Tectonic and Climatic Evolution of the Arabian Sea Region

    NASA Astrophysics Data System (ADS)

    Bosence, Dan

    2004-08-01

    This multi-authored volume provides a sampling of current research into the geology of the Arabian Sea region. The editors emphasize the importance of this area as the Earth's best natural laboratory for studying relations between climate and the growth and erosion of an orogenic belt.Uplift of the Himalaya and Tibetan Plateau is now believed to have altered global climate during the Cenozoic, and also to have affected the development of the region's monsoonal climate. The geological features of the region that make it a good area to study such processes include the excellent rock outcrops in the surrounding arid Arabian and Asian landmasses, the locally high rates of sedimentation which provide high-resolution sedimentological and geochemical information, and the monsoon itself, that imparts an annual time beat in some sedimentary successions. However, the region is very large and access is not always easy. Also, many areas are still poorly known geologically such that this volume contains some papers on basic survey geology.

  14. Origin of cold bias over the Arabian Sea in Climate Models.

    PubMed

    Sandeep, S; Ajayamohan, R S

    2014-01-01

    Almost all climate models in Coupled Model Inter-comparison Project phase five (CMIP5) were found to have a cold bias in Sea Surface Temperature (SST) over the northern Arabian Sea, which is linked to the biases in the Indian Summer Monsoon (ISM). This cold SST bias was attributed to the anomalous cold winds from the north-western part of south Asian landmass during boreal winter. However, the origin of the anomalously strong cold winds over the Arabian Sea and its association with the large-scale circulation is obscure. Here we show that an equatorward bias in subtropical Jetstream during boreal spring season anomalously cools down the northern Arabian Sea and adjoining land regions in CMIP5 models. The models with stronger equatorward bias in subtropical jet are also the ones with stronger cold SST bias over the Arabian Sea. The equatorward shift coupled with enhanced strength of the subtropical jet produce a stronger upper tropospheric convergence, leading to a subsidence and divergence at lower levels over the Arabian deserts. The low entropy air flowing from the Arabian land mass cools the northern Arabian Sea. The weaker meridional temperature gradients in the colder models substantially weaken ISM precipitation. PMID:25228235

  15. Climate oscillations reflected in the Arabian Sea subseafloor microbiome

    NASA Astrophysics Data System (ADS)

    Orsi, William; Coolen, Marco; He, Lijun; Wuchter, Cornelia; Irigoien, Xabier; Chust, Guillem; Johnson, Carl; Hemingway, Jordon; Lee, Mitchell; Galy, Valier; Giosan, Liviu

    2016-04-01

    Marine sediment contains a vast microbial biosphere that influences global biogeochemical cycles over geological timescales. However, the environmental factors controlling the stratigraphy of subseafloor microbial communities are poorly understood. We studied a sediment core directly underlying the Arabian Sea oxygen minimum zone (OMZ), which exhibits organic carbon rich sapropelic laminae deposited under low oxygen conditions. Consistent with several other cores from the same location, age dating revealed the sapropelic layers coincide with warm North Atlantic millennial-scale Dansgaard-Oeschger events, indicating a direct link between the strength of the OMZ and paleoclimate. A total of 214 samples spanning 13 m and 52 Kyr of deposition were selected for geochemical analyses and paleoclimate proxy measurements, as well as high-throughput metagenomic DNA sequencing of bacteria and archaea. A novel DNA extraction protocol was developed that allowed for direct (unamplified) metagenomic sequencing of DNA from each sample. This dataset represents the highest resolved sedimentary metagenomic sampling profile to date. Analysis of these data together with multiple paleoceanographic proxies show that millennial-scale paleoenvironmental conditions correlate with the metabolism and diversity of bacteria and archaea over the last glacial-interglacial cycle in the Arabian Sea. The metabolic potential for bacterial denitrification correlates with climate-driven OMZ strength and concomitant nitrogen stable isotope fractionation, whereas catabolic potential reflects changing marine organic matter sources across the Last Glacial Maximum. These results indicate that the subsisting microbial communities had been stratified to a large extent by paleoceanographic conditions at the time of deposition. Paleoenvironmental conditions should thus be considered as a mechanism that can help explain microbiome stratigraphy in marine sediment.

  16. The relationship between Arabian Sea upwelling and Indian monsoon revisited

    NASA Astrophysics Data System (ADS)

    Yi, X.; Hünicke, B.; Tim, N.; Zorita, E.

    2015-11-01

    Studies based on upwelling indices (sediment records, sea-surface temperature and wind) suggest that upwelling along the western coast of Arabian Sea is strongly affected by the Indian summer monsoon (ISM). In order to examine this relationship directly, we employ the vertical water mass transport produced by the eddy-resolving global ocean simulation STORM driven by meteorological reanalysis over the last 61 years. With its very high spatial resolution (10 km), STORM allows us to identify characteristics of the upwelling system. We analyze the co-variability between upwelling and meteorological and oceanic variables from 1950 to 2010. The analyses reveal high interannual correlations between coastal upwelling and along-shore wind-stress (r=0.73) as well as with sea-surface temperature (r0.83). However, the correlation between the upwelling and the ISM is small and other factors might contribute to the upwelling variability. In addition, no long-term trend is detected in our modeled upwelling time series.

  17. Primary productivity and nitrogen fixation by Trichodesmium spp. in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Parab, Sushma G.; Matondkar, S. G. P.

    2012-12-01

    Trichodesmium was studied with the purpose of understanding its distribution, organic production and nitrogen fixation in the Arabian Sea. Out of the 143 stations sampled, a total of 93 stations showed the presence of Trichodesmium filaments. Two species of Trichodesmium namely, T. thiebautii and T. erythraeum were found. These were distributed on the basis of the physico-chemical conditions of the Arabian Sea. This was the first time that we managed to detect and record the presence of Trichodesmium thiebautii bloom in the Arabian Sea at depths as deep as 60-70 m. Total counts of Trichodesmium varied between 0 and 400737 filamentsL- 1. T. thiebautii developed in offshore waters during the fall intermonsoon, when the water temperature was around 28 °C and nitrate content was as low as 0.34 μM. After the northeast monsoon, Trichodesmium erythraeum developed in the offshore area and then spread to coastal waters. Both species of Trichodesmium together produced a total of 0.263 TgCyear- 1 and fixed a total of 0.2976 TgNyear- 1 in the Arabian Sea. The study revealed that Trichodesmium was a major contributor to the organic matter productivity of the Arabian Sea during the period from November to April. The seasonality of the blooms of Trichodesmium is discussed with the help of Ocean Color Monitoring (OCM) data and biogeochemical implication of these findings in the Arabian Sea.

  18. Carbonate and carbon fluctuations in the Eastern Arabian Sea over 140 ka: Implications on productivity changes?

    NASA Astrophysics Data System (ADS)

    Guptha, M. V. S.; Naidu, P. Divakar; Haake, Birgit Gaye; Schiebel, Ralf

    2005-07-01

    Biological productivity in the western Arabian Sea was higher during interglacial than glacial times. In the eastern Arabian Sea productivity was higher during the glacials compared to interglacials, which is in sharp contrast to the southwest monsoon intensity variations. To examine temporal changes in productivity in the eastern Arabian Sea over the last 140 ka, oxygen isotopes, calcium carbonate and organic carbon on three cores (SL-1 & 4 and SK 129-CR05) were analyzed. Oxygen isotope records display distinct glacial and interglacial transitions. In the northeastern (Core SL-1) and eastern Arabian Sea (Core SL-4) both calcium carbonate and organic carbon variations show no significant systematic relationship with glacial and interglacials periods. In the southeastern Arabian Sea (Core SK-129-CR05) calcium carbonate shows high and low values during interglacial and glacials, respectively, and temporal changes in organic carbon concentration are significant only during MIS 5. Differential variation of calcium carbonate and organic carbon concentration at the northeastern and southeastern Arabian Sea, and between glacials and interglacials, are attributed to regional differences in sedimentation rates, dilution and preservation, which modify the signal of carbonate and carbon production.

  19. Modelling the seasonality of subsurface light and primary production in the Arabian Sea

    USGS Publications Warehouse

    Brock, John C.; Sathyendranath, Shubha; Platt, Trevor

    1993-01-01

    Seasonal changes in mixed-layer depth and phytoplankton biomass in the Arabian Sea are assessed with climatologies of ship-based hydrographic measurements and ocean-color observations from satellite.  At the close of the intermonsoons in November and especially May, the open Arabian Sea resembles the stereotypic, unperturbed tropical ocean, with a thin oligotrophic mixed layer and a pronounced subsurface chlorophyll maximum.  Both the northeast and southwest monsoons disrupt this typical tropical hydrography through mixed-layer deepening and eutrophication in the central and northern Arabian Sea.  Computations using a spectral model of light penetration suggest that seasonal changes in mixed-layer thickness and phytoplankton concentration result in pronounced fluctuations through the annual cycle in the radiant flux reaching the base of the mixed layer.  At the close of the fall and spring intermonsoons the base of the model euphotic zone is in the thermocline across all of the open Arabian Sea.  The euphotic zone appears to rise into the mixed layer of the northern Arabian Sea during both the winter and summer monsoons.  Strong seasonality in total primary production and its partitioning between the mixed layer and thermocline is predicted byb a photo-synthesis-irradiance model for a site in the western Arabian Sea (14.36° N, 57.38° E).  Modeled mixed-layer primary production depicts an intense peak for the southwest monsoon and a secondary northeast monsoon peak separated by intermonsoon period of low production.  During the fall and spring intermonsoons, in the presence of a subsurface clorophyll maximum, the model estimate of primary production in the thermocline exceeds that in the mixed layer.  Our model calculations suggest that the subsurface clorophyll maximum present in the Arabian Sea during the spring intermonsoon is a precursor of the regional, summer, phytoplankton bloom.

  20. Tropospheric ozone pool over Arabian sea during pre-monsoon

    NASA Astrophysics Data System (ADS)

    Jia, Jia; Ladstätter-Weißenmayer, Annette; Hou, Xuewei; Rozanov, Alexei; Burrows, John

    2016-04-01

    This study focuses on the remarkable and stable phenomenon-enhancement of the tropospheric ozone over Arabian Sea (AS) during the pre-monsoon season. Satellite data (SCIAMACHY LNM, OMI/MLS and TES) showed a strong and clear ozone seasonality over AS with ~42 DU maxima in pre-monsoon season. With the help of MACC reanalysis data, our results showed that 3/4 of the enhanced ozone during this season is contributed at 0-8 km height. The main source of the ozone enhancement is believed to be a long range transport, together with a suitable meteorological condition for pollution accumulation. Local chemistry plays different roles over different altitudes. However we believe the contribution to the tropospheric ozone enhancement from the chemistry is low. The contribution of the STE is unclear. In addition, the interannual variation of the pre-monsoon tropospheric ozone enhancement over AS is discussed. The anomalies in 2005 and 2010 could be due to the dynamical variation of ozone caused by the El Niño events.

  1. Response of the Arabian Sea to global warming and associated regional climate shift.

    PubMed

    Kumar, S Prasanna; Roshin, Raj P; Narvekar, Jayu; Kumar, P K Dinesh; Vivekanandan, E

    2009-12-01

    The response of the Arabian Sea to global warming is the disruption in the natural decadal cycle in the sea surface temperature (SST) after 1995, followed by a secular warming. The Arabian Sea is experiencing a regional climate-shift after 1995, which is accompanied by a five fold increase in the occurrence of "most intense cyclones". Signatures of this climate-shift are also perceptible over the adjacent landmass of India as: (1) progressively warmer winters, and (2) decreased decadal monsoon rainfall. The warmer winters are associated with a 16-fold decrease in the decadal wheat production after 1995, while the decreased decadal rainfall was accompanied by a decline of vegetation cover and increased occurrence of heat spells. We propose that in addition to the oceanic thermal inertia, the upwelling-driven cooling provided a mechanism that offset the CO(2)-driven SST increase in the Arabian Sea until 1995. PMID:19592084

  2. Nematode abundance at the oxygen minimum zone in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Cook, Adam A.; Lambshead, P. John D.; Hawkins, Lawrence E.; Mitchell, Nicola; Levin, Lisa A.

    2000-01-01

    This paper supports the hypothesis that low oxygen does not influence deep-sea nematode abundance by investigating an oxygen minimum zone (OMZ) on the Oman slope in the Arabian Sea. Correlation with a number of environmental variables indicated that food quality (measured as the hydrogen index) rather than oxygen was the major predictor of nematode abundance. Nematode abundance was also positively correlated with abundance of total macrofauna, annelids, spionid polychaetes and macrofaunal tube builders. Comparison with published data showed Arabian Sea nematode abundance to be similar to that of the Porcupine Seabight and Bay of Biscay regions of the northeast Atlantic, which also receive significant quantities of phytodetritus but have no OMZ.

  3. Ammonia oxidation rates and nitrification in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Newell, Silvia E.; Babbin, Andrew R.; Jayakumar, Amal; Ward, Bess B.

    2011-12-01

    Nitrification rates, as well as the relationships between rates and ammonia oxidizer abundance (both archaeal and bacterial), were investigated in the Arabian Sea. Ammonia oxidation rates were measured directly using 15N-NH4+stable isotope additions in gas-impermeable, trace metal clean trilaminate bags (500 mL) at in situ temperature. Tracer incubations were performed at three stations at depths above, below, and within the oxycline of the open-ocean oxygen minimum zone (OMZ). Ammonia oxidation rates were similar to previous open-ocean measurements, ranging from undetectable to 21.6 ± 0.1 nmol L-1 d-1. The highest rates at each station occurred at the primary nitrite maximum (above the OMZ), and rates were very low at depths greater than 900 m. The abundances of both ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) were estimated using theamoA gene by quantitative polymerase chain reaction (qPCR). Both AOA and AOB amoA were detected above, within, and below the OMZ, although the AOA were always more abundant than the AOB, by a factor of 35-216. Nitrification rates were not directly correlated to AOA or AOB amoA abundance. These rates offer new insight into the role of nitrification in the mesopelagic zone. The abundance of AOA amoA genes at 1000 m suggests that ˜50% of the microbial biomass could be autotrophic. Additionally, the integrated nitrification rate at depth implies that nitrification could consume most of the ammonium produced by the flux of organic carbon in the mesopelagic zone.

  4. Characteristics of convective boundary layer over the Arabian sea region

    SciTech Connect

    Parasnis, S.S.

    1996-12-31

    The Convective Boundary Layer (CBL) over the oceanic regions plays an important role in regulating the transport of energy and moisture upward into the atmosphere from the surface. CBL structure over the Arabian sea region has been explored using the aerological soundings at two ships viz. SHIRSHOV (12.5{degrees}N, 68{degrees}E ) and OKEAN (14.5{degrees} N, 66{degrees} E) during MONSOON-77. Conserved variable analysis of the mean data sets obtained during the period of 29 June - 16 July, 1977 revealed salient features of the CBL over these regions. The vertical gradients of saturation point parameters viz. virtual potential temperature ({Theta}{sub v}), equivalent potential temperature ({Theta}{sub e}), saturated equivalent potential temperature ({Theta}{sub es}), saturation pressure deficit (P*) and the mixing ratio (q) were used to characterize the different sublayers such as subcloud layer, cloud layer and inversion/stable layer. The mean cloud base was around 950 hPa and the subcloud layer has nearly constant {Theta}{sub v}. The moist layer was associated with unstable {Theta}{sub es} with nearly constant value of P* ({approximately} -40 hPa). This cloud layer was capped by the stable (over OKEAN). The {Theta}{sub e} minimum over OKEAN was observed at 650 hPa (50 hPa above the CBL top) indicating that at some time the convection had reached deeper levels. The {Theta}{sub e} -q diagrams showed a characteristic mixing line up through the cloud and stable layer to the top of CBL. The low level stability analysis using the {Theta}{sub e} and {Theta}{sub es} profiles indicated conditions favorable for shallow convection over OKEAN and for deep convection over SHIRSHOV. The above characteristic features could be attributed to the prevailing weather conditions at OKEAN and SHIRSHOV. The results are discussed.

  5. Diversity and distribution of winter phytoplankton in the Arabian Gulf and the Sea of Oman

    NASA Astrophysics Data System (ADS)

    Polikarpov, Igor; Saburova, Maria; Al-Yamani, Faiza

    2016-05-01

    The spatial distribution of the phytoplankton (diversity, composition, and cell abundance) was described in relation to local environmental conditions across the Arabian Gulf, the Strait of Hormuz, and the Sea of Oman based on data of ROPME cruise of winter 2006. The 376 phytoplankton taxa identified in these waters represented a diverse composition of species with a prevalence of dinoflagellates and diatoms. Three peaks in the phytoplankton abundance were recorded throughout the studied area associated with diatom-dominated phytoplankton blooms in the central and northwestern part of the Arabian Gulf and in the Sea of Oman and the adjacent waters. The studied area was divided into three main regions by cluster analysis based on differences in the phytoplankton composition and concentration. The Sea of Oman and the Strait of Hormuz were occupied by highly abundant, strongly diatom-dominated phytoplankton assemblage. The Arabian Gulf was divided into two main regions along a diagonal northwest-southeast axis, with rather diatom-dominated phytoplankton assemblage off the south and along the Iranian coast but with flagellate-dominated phytoplankton of the north and along the Arabian coast. The distance-based linear modeling revealed a significant relationship between the phytoplankton composition and water masses as indexed by salinity. Our results demonstrated that abundance and composition of winter phytoplankton were related to water circulation pattern in the Arabian Gulf and the Sea of Oman.

  6. Denitrification as the dominant nitrogen loss process in the Arabian Sea.

    PubMed

    Ward, B B; Devol, A H; Rich, J J; Chang, B X; Bulow, S E; Naik, Hema; Pratihary, Anil; Jayakumar, A

    2009-09-01

    Primary production in over half of the world's oceans is limited by fixed nitrogen availability. The main loss term from the fixed nitrogen inventory is the production of dinitrogen gas (N(2)) by heterotrophic denitrification or the more recently discovered autotrophic process, anaerobic ammonia oxidation (anammox). Oceanic oxygen minimum zones (OMZ) are responsible for about 35% of oceanic N(2) production and up to half of that occurs in the Arabian Sea. Although denitrification was long thought to be the only loss term, it has recently been argued that anammox alone is responsible for fixed nitrogen loss in the OMZs. Here we measure denitrification and anammox rates and quantify the abundance of denitrifying and anammox bacteria in the OMZ regions of the Eastern Tropical South Pacific and the Arabian Sea. We find that denitrification rather than anammox dominates the N(2) loss term in the Arabian Sea, the largest and most intense OMZ in the world ocean. In seven of eight experiments in the Arabian Sea denitrification is responsible for 87-99% of the total N(2) production. The dominance of denitrification is reproducible using two independent isotope incubation methods. In contrast, anammox is dominant in the Eastern Tropical South Pacific OMZ, as detected using one of the isotope incubation methods, as previously reported. The abundance of denitrifying bacteria always exceeded that of anammox bacteria by up to 7- and 19-fold in the Eastern Tropical South Pacific and Arabian Sea, respectively. Geographic and temporal variability in carbon supply may be responsible for the different contributions of denitrification and anammox in these two OMZs. The large contribution of denitrification to N(2) loss in the Arabian Sea indicates the global significance of denitrification to the oceanic nitrogen budget. PMID:19727197

  7. Detection and monitoring of super sandstorm and its impacts on Arabian Sea-Remote sensing approach

    NASA Astrophysics Data System (ADS)

    Kunte, Pravin D.; M. A., Aswini

    2015-06-01

    The present study addresses an intense sandstorm event over the Persian Gulf and its transport over the Arabian Sea region and the Indian sub-continent using satellite observations and measurements. MODIS data are used to analyze the temporal variation of the dust events that occurred from 17 to 24 March 2012 with the strongest intensity on 20 March over the Arabian Sea. MODIS images are examined to provide an independent assessment of dust presence and plume location and its migration over the Arabian Sea to the Indian sub-continent. Dust enhancement and dust detection procedure is attempted to demarcate the dust event. Dust source, formation, transportation path, and dissipation is studied using source-back-tracking, surface wind, and surface pressure, wind speed and direction, geo-potential height for different pressure level, and remote sensing methods. Finally, an attempt is made to investigate the impact of super sandstorm on the Arabian Sea by studying sea surface temperature and chlorophyll a variability during the events. It is noted that sea surface temperature is decreased and chlorophyll a concentration increased during the post-event period. The present study demonstrates the use of remote sensing data and geospatial techniques in detecting and mapping of dust events and monitoring dust transport along specific regional transport pathways over land and ocean.

  8. Past, present, and future changes in marine biogeochemistry in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Six, Katharina; Segschneider, Joachim

    2014-05-01

    The work presented here aims at a better understanding of the Asian Monsoon system including the marine biogeochemistry in the Arabian Sea. Changes in the past as recorded in marine sediments, as simulated over the past 1000 years, and under forcing by anthropogenic CO2 emissions by numerical model simulations are investigated. The investigation is based on three columns: a sediment core taken in the Arabian Sea (core SO130-275KL taken off Pakistan), a pre-industrial model run from 850 - 1850 with the Max Planck Institute's Earth System Model (MPI-ESM) including the marine and terrestrial carbon cycle and forced by solar variations and volcanic eruptions, and a continuation of this simulation to 2005 under the historical anthropogenic CO2 forcing which allows a comparison with present day climatology. In a first step we compare model results for a set of biogeochemical tracers within the water column and the sediment mixed with observations in the Arabian Sea. We further analyse correlations between Monsoon forcing (represented by zonal wind speed at 850 hPA, short wave radiation, Indian summer precipitation) and biogeochemical parameters, with particular focus on denitrification rates and fluxes to the sediment. This analysis is focused on three regions: off Somalia and off Oman for the summer monsoon, and the central Arabian Sea for the winter monsoon. For the summer monsoon, the highest correlation is found between zonal wind speed and calcite flux to the sediment off Somalia, for the winter monsoon the correlation is highest for short wave radiation in the central Arabian Sea. Time series of mixed layer depth and integrated primary production within the upper 100 m of the ocean from a CMIP5 historical experiment (1850-2005) show, at the location of the sediment core SO130-275KL, little correlation during the summer monsoon, but good correlation during the winter monsoon. As a result, the sediment core is more likely to document winter monsoon conditions

  9. Aerosol optical depth, physical properties and radiative forcing over the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Satheesh, S. K.; Krishna Moorthy, K.; Kaufman, Y. J.; Takemura, T.

    2006-01-01

    The Arabian Sea region (4° N 20° N to 50° E 78° E) has a unique weather pattern on account of the Indian monsoon and the associated winds that reverse direction seasonally. The aerosol data, collected using ship-borne and island platforms (for 8 years from 1995 to 2002) along with MODIS (onboard TERRA satellite) data (from 2000 to 2003) have been used to evolve a comprehensive characterisation of the spatial and temporal variation in the physical, chemical, and radiative properties of aerosols over the Arabian Sea. The aerosol optical depth (AOD) was found to increase with latitude between the equator and 12° N. Over the northern Arabian Sea (regions lying north of 12° N), AODs do not show significant latitudinal variations; the average aerosol optical depth for this region was 0.29±0.12 during winter monsoon season (WMS; November to March) and 0.47±0.14 during summer monsoon season (SMS; April/May to September). The corresponding Angstrom exponents were 0.7±0.12 and 0.3±0.08, respectively. The low values of the exponent during SMS indicate the dominance of large aerosols (mainly dust particles >1 µm). The latitudinal gradient in AOD in the southern Arabian Sea is larger during SMS compared to WMS.

  10. Sea level rise within the west of Arabian Gulf using tide gauge and continuous GPS measurements

    NASA Astrophysics Data System (ADS)

    Ayhan, M. E.; Alothman, A.

    2009-04-01

    Arabian Gulf is connected to Indian Ocean and located in the south-west of the Zagros Trust Belt. To investigate sea level variations within the west of Arabian Gulf, monthly means of sea level at 13 tide gauges along the coast of Saudi Arabia and Bahrain, available in the database of the Permanent Service for Mean Sea Level (PSMSL), are studied. We analyzed individually the monthly means at each station, and estimated secular sea level rate by a robust linear trend fitting. We computed the average relative sea level rise rate of 1.96 ± 0.21 mm/yr within the west of Arabian Gulf based on 4 stations spanning longer than 19 years. Vertical land motions are included into the relative sea level measurements at the tide gauges. Therefore sea level rates at the stations are corrected for vertical land motions using the ICE-5G v1.2 VM4 Glacial Isostatic Adjustment (GIA) model then we found the average sea level rise rate of 2.27 mm/yr. Bahrain International GPS Service (IGS) GPS station, which is close to the Mina Sulman tide gauge station in Bahrain, is the only continuous GPS station accessible in the region. The weekly GPS time series of vertical component at Bahrain IGS-GPS station referring to the ITRF97 from 1999.2 to 2008.6 are downloaded from http://www-gps.mit.edu/~tah/. We fitted a linear trend with an annual signal and one break to the GPS vertical time series and found a vertical land motion rate of 0.48 ± 0.11 mm/yr. Assuming the vertical rate at Bahrain IGS-GPS station represents the vertical rate at each of the other tide gauge stations studied here in the region, we computed average sea level rise rate of 2.44 ± 0.21 mm/yr within the west of Arabian Gulf.

  11. Denitrification in the Arabian Sea: A 3D ecosystem modelling study

    NASA Astrophysics Data System (ADS)

    Anderson, Thomas R.; Ryabchenko, Vladimir A.; Fasham, Michael J. R.; Gorchakov, Victor A.

    2007-12-01

    A three-dimensional hydrodynamic-ecosystem model was used to examine the factors determining the spatio-temporal distribution of denitrification in the Arabian Sea. The ecosystem model includes carbon and nitrogen as currencies, cycling of organic matter via detritus and dissolved organic matter, and both remineralization and denitrification as sinks for material exported below the euphotic zone. Model results captured the marked seasonality in plankton dynamics of the region, with characteristic blooms of chlorophyll in the coastal upwelling regions and central Arabian Sea during the southwest monsoon, and also in the northern Arabian Sea during the northeast monsoon as the mixed layer shoals. Predicted denitrification was 26.2 Tg N yr -1,the greatest seasonal contribution being during the northeast monsoon when primary production is co-located with the zone of anoxia. Detritus was the primary organic substrate consumed in denitrification (97%), with a small (3%) contribution by dissolved organic matter. Denitrification in the oxygen minimum zone was predicted to be fuelled almost entirely by organic matter supplied by particles sinking vertically from the euphotic zone above (0.73 mmol N m -2 d -1) rather than from lateral transport of organic matter from elsewhere in the Arabian Sea (less than 0.01 mmol N m -2 d -1). Analysis of the carbon budget in the zone of denitrification (north of 10°N and east of 55°E) indicates that the modelled vertical export flux of detritus, which is similar in magnitude to estimates from field data based on the 234Th method, is sufficient to account for measured bacterial production below the euphotic zone in the Arabian Sea.

  12. Observational study of upper ocean cooling due to Phet super cyclone in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Muni Krishna, K.

    2016-05-01

    Phet super cyclone (31 May-7 June 2010) was the most intense and also the rarest of the rare track in Arabian Sea as per the recorded history during 1877-2009. The present study focuses on the ocean physical responses to Phet cyclone using satellite and Argo observations. The sea surface temperature is decreased to 6 °C with an approximately 350 km long and 100 km width area in the Arabian Sea after the cyclone passage. The translation speed of cyclone is 3.86 m/s, the mixed layer is 79 m, and thermocline displacement is 13 m at the cooling area. With the relationship of wind stress curl and Ekman pumping velocity (EPV), the author found that the speed of EPV was increased after the passage of cyclone. So the extent of the SST drop was probably due to the moving speed of cyclone and the depth of the mixed layer.

  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. Southwest Monsoon Circulation and Environments of Recent Planktonic Foraminifera in the Northwestern Arabian Sea

    NASA Astrophysics Data System (ADS)

    Brock, John C.; McClain, Charles R.; Anderson, David M.; Prell, Warren L.; Hay, William W.

    1992-12-01

    Digital hydrographic data combined with satellite thermal infrared and visible band remote sensing provide a synoptic climatological view of the shallow planktonic environment. This paper uses wind, hydrographic, and ocean remote sensing data to examine southwest monsoon controls on the foraminiferal faunal composition of Recent seafloor sediments of the northwestern Arabian Sea. Ekman pumping resulting in open-ocean upwelling and coastal upwelling create two distinctly different mixed layer plankton environments in the northwestern Arabian Sea during the summer monsoon. Open-sea upwelling to the northwest of the mean July position of the Findlater Jet axis yields a mixed layer environment with temperatures of less than 25°C to about 26.5°C, phytoplankton pigment concentrations between 1.5 and 5.0 mg/m³, and mixed layer depths less than 50 m. Convergence in the Ekman layer in the central Arabian Sea drives the formation of a mixed layer that is greater than 50 m thick, warmer than about 26.5°C, and has phytoplankton pigment concentrations generally below 2.0 mg/m³. Coastal upwelling creates an extremely eutrophic plankton environment that persists over and immediately adjacent to the Omani shelf and undergoes significant offshore transport only within topographically induced coastal squirts. The foraminiferal faunal composition of upper Pleistocene deep-sea sediments of the northwestern Arabian Sea are mainly controlled by vertical nutrient fluxes caused by Ekman pumping, not coastal upwelling. Transfer functions for late Pleistocene mixed layer depth, temperature, and chlorophyll have been obtained through factor analysis and nonlinear multiple regression between late summer mixed layer environment and Recent sediment faunal observations.

  15. Origin and fate of the secondary nitrite maximum in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Lam, P.; Jensen, M. M.; Kock, A.; Lettmann, K. A.; Plancherel, Y.; Lavik, G.; Bange, H. W.; Kuypers, M. M. M.

    2011-06-01

    The Arabian Sea harbours one of the three major oxygen minimum zones (OMZs) in the world's oceans, and it alone is estimated to account for ~10-20 % of global oceanic nitrogen (N) loss. While actual rate measurements have been few, the consistently high accumulation of nitrite (NO2-) coinciding with suboxic conditions in the central-northeastern part of the Arabian Sea has led to the general belief that this is the region where active N-loss takes place. Most subsequent field studies on N-loss have thus been drawn almost exclusively to the central-NE. However, a recent study measured only low to undetectable N-loss activities in this region, compared to orders of magnitude higher rates measured towards the Omani Shelf where little NO2- accumulated (Jensen et al., 2011). In this paper, we further explore this discrepancy by comparing the NO2--producing and consuming processes, and examining the relationship between the overall NO2- balance and active N-loss in the Arabian Sea. Based on a combination of 15N-incubation experiments, functional gene expression analyses, nutrient profiling and flux modeling, our results showed that NO2- accumulated in the central-NE Arabian Sea due to a net production via primarily active nitrate (NO3-) reduction and to a certain extent ammonia oxidation. Meanwhile, NO2- consumption via anammox, denitrification and dissimilatory nitrate/nitrite reduction to ammonium (NH4+) were hardly detectable in this region, though some loss to NO2- oxidation was predicted from modeled NO3- changes. No significant correlation was found between NO2- and N-loss rates (p>0.05). This discrepancy between NO2- accumulation and lack of active N-loss in the central-NE Arabian Sea is best explained by the deficiency of labile organic matter that is directly needed for further NO2- reduction to N2O, N2 and NH4+, and indirectly for the remineralized NH4+ required by anammox. Altogether, our data do not support the long-held view that NO2- accumulation is a

  16. Origin and fate of the secondary nitrite maximum in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Lam, P.; Jensen, M. M.; Kock, A.; Lettmann, K. A.; Plancherel, Y.; Lavik, G.; Bange, H. W.; Kuypers, M. M. M.

    2011-03-01

    The Arabian Sea harbours one of the three major oxygen minimum zones (OMZs) in the world's oceans, and it alone is estimated to account for ~10-20% of global oceanic nitrogen (N) loss. While actual rate measurements have been few, the consistently high accumulation of nitrite (NO2-) coinciding with suboxic conditions in the central-northeastern part of the Arabian Sea has led to the general belief that this is the region where active N-loss takes place. Most subsequent field studies on N-loss have thus been drawn almost exclusively to the central-NE. However, a recent study measured only low to undetectable N-loss activities in this region, compared to orders of magnitude higher rates measured towards the Omani shelf where little NO2- accumulated (Jensen et al., 2011). In this paper, we further explore this discrepancy by comparing the NO2- producing and consuming processes, and examining the relationship between the overall NO2- balance and active N-loss in the Arabian Sea. Based on a combination of 15N-incubation experiments, functional gene expression analyses, nutrient profiling and flux modeling, our results showed that NO2- accumulated in the Central-NE Arabian Sea due to a net production via primarily active nitrate (NO3-) reduction and to a certain extent ammonia oxidation. Meanwhile, NO2- consumption via anammox, denitrification and dissimilatory nitrate/nitrite reduction to ammonium (NH4+) were hardly detectable in this region, though some loss to NO2- oxidation was predicted from modeled NO3- changes. No significant correlation was found between NO2- and N-loss rates (p>0.05). This discrepancy between NO2- accumulation and lack of active N-loss in the Central-NE Arabian Sea is best explained by the deficiency of organic matter that is directly needed for further NO2- reduction to N2O, N2 and NH4+, and indirectly for the remineralized NH4+ required by anammox. Altogether, our data do not support the long-held view that NO2- accumulation is a direct

  17. Westward movement of eddies into the Gulf of Aden from the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Al Saafani, M. A.; Shenoi, S. S. C.; Shankar, D.; Aparna, M.; Kurian, J.; Durand, F.; Vinayachandran, P. N.

    2007-11-01

    Sea level anomalies (SLA) from satellite altimetry (1993-2003) reveal the westward movement of mesoscale eddies in the Gulf of Aden. Inside the gulf the eddies move at a speed of ˜6.0-8.5 cm s-1, comparable to the first-mode baroclinic Rossby wave speed of 7.2 cm s-1. We show that the eddies, which enter the gulf from the Arabian Sea, owe their existence to more than one mechanism. Local Ekman pumping in the western Arabian Sea is important during the summer monsoon (June-September). In May and during the latter half of the summer monsoon (late July to September) and the fall intermonsoon (October), the dominant mechanism is the generation of eddies by the instabilities in the Somali Current and the large eddies associated with it (Great Whirl and Socotra eddy). During the winter monsoon (November-April) the dominant mechanism involves the westward propagating Rossby waves generated either in the Arabian Sea by Ekman pumping or along the west coast of India by poleward propagating Kelvin waves. These Rossby waves from the Arabian Sea propagate slower on entering the gulf because of a shallower thermocline in the gulf. Analysis shows that the SLA signal consists of low (annual and subannual) and high (˜100-180 d) frequencies. The low-frequency signal (mainly annual) shows a discontinuity between 52°E and 60°E. Though the high-frequency signal is seen at all longitudes, a wavelet analysis shows that it was significant only west of 60°E. An energy analysis, based on model simulations, suggests that barotropic instabilities are important during the entire year and that baroclinic instabilities are also important during the summer monsoon.

  18. Biomass of zooplankton estimated by acoustical sensors in the Arabian sea. Final report

    SciTech Connect

    Holliday, D.V.

    1996-11-22

    The long term goal of our overall research program is the development of data-based models to predict ecological relationships of zooplankton, phytoplankton and the physical environment in the sea. The overall objective of the work carried out within the scope of this particular contract was to acoustically measure the dynamics of zooplankton and micronekton in the northern Arabian Sea during several seasons. The scientific focus was to examine the impact, if any, of the two annual monsoons that are thought to drive the ecosystem response in the area. This particular project involved the design and construction of two sensors which were then deployed in the Arabian Sea by several of our co-PIVs in the ONR ARI on Forced Upper Ocean Dynamics during the time period in which the JGOFS program also focused their efforts on the northern Arabian Sea. This contract involved only the development, calibration and maintenance of the instrumentation. The data processing, other than that which has been necessary for the purposes of quality assurance, was not induded in our original proposal.

  19. Influence of continental outflow on aerosol chemical characteristics over the Arabian Sea during winter

    NASA Astrophysics Data System (ADS)

    Kumar, Ashwini; Sudheer, A. K.; Goswami, Vineet; Bhushan, Ravi

    2012-04-01

    The chemical composition of aerosol over the Arabian Sea was investigated during December 2007. Elemental Carbon (EC), Organic Carbon (OC), water soluble organic and inorganic constituents and crustal elements (Al, Fe, Ca, and Mg) were measured in total suspended particulate samples (TSP) collected from marine boundary layer of the Arabian Sea when the oceanic region is influenced by continental outflow. Anthropogenic and natural mineral aerosol originating from continental regions dominates the aerosol composition contributing ∼88% of total aerosol mass. The sea-salt aerosol comprises only ∼12% of TSP. The carbonaceous aerosol exhibits spatial trend similar to that of K+ suggesting major source could be biomass burning. Secondary organic aerosol (SOA) contribution estimated by EC-tracer method suggests that up to 67% of OC can be of secondary origin. Average water soluble organic carbon to OC ratio is ∼0.9, indicates significant formation of SOA during transport of continental air masses. These results demonstrate the dominance of continental aerosol over the Arabian Sea during wintertime where deposition may have major impact on surface ocean biogeochemistry.

  20. Benthic foraminifera from the Arabian Sea oxygen minimum zone: towards a paleo-oxygenation proxy.

    NASA Astrophysics Data System (ADS)

    Clemence, Caulle; Meryem, Mojtahid; Karoliina, Koho; Andy, Gooday; Gert-Jan, Reichart; Gerhard, Schmiedl; Frans, Jorissen

    2014-05-01

    Benthic foraminifera from the Arabian Sea oxygen minimum zone: towards a paleo-oxygenation proxy. C. Caulle1, M. Mojtahid1, K. Koho2,3, A. Gooday4, G. J. Reichart2,3, G. Schmiedl5, F. Jorissen1 1UMR CNRS 6112 LPG-BIAF, University of Angers, 2 bd Lavoisier, 49045 Angers Cedex 2Utrecht University, Faculty of Geosciences, Department of Earth Sciences, Budapestlaan 4, 3584 CD Utrecht, The Netherlands 3Royal Netherland Institute for Sea Research (Royal NIOZ), Landsdiep 4, 1797 SZ 't Horntje (Texel) 4Southampton Oceanography Centre, Empress Dock, European Way, Southampton SO14 3ZH, UK 5Department of Geosciences, University of Hamburg, Bundesstraße 55, 20146 Hamburg, Germany The thermohaline circulation oxygenates the deep ocean sediment and therefore enables aerobic life on the sea-floor. In the past, interruption of this deep water formation occurred several times causing hypoxic to anoxic conditions on the sea-floor leading to major ecological turnover. A better understanding of the interaction between climate and bottom water oxygenation is therefore essential in order to predict future oceanic responses. Presently, permanent (stable over decadal timescale) low-oxygen conditions occur naturally at mid-water depths in the northern Indian Ocean (Arabian Sea). Oxygen Minimum Zones (OMZ) are key areas to understand the hypoxic-anoxic events and their impact on the benthic ecosystem. In this context, a good knowledge of the ecology and life cycle adaptations of the benthic foraminiferal assemblages living in these low oxygen areas is essential. A series of multicores were recovered from three transects showing an oxygen gradient across the OMZ: the Murray Ridge, the Oman margin and the Indian margin. The stations located at the same depths showed slightly different oxygen concentrations and large differences in organic matter content. These differences are mainly related to the geographic location in the Arabian Sea. We investigated at these stations live and dead benthic

  1. Late quaternary time series of Arabian Sea productivity: Global and regional signals

    NASA Technical Reports Server (NTRS)

    Clemens, Steven C.; Prell, W. L.; Murray, D. W.

    1992-01-01

    Modern annual floral and faunal production in the northwest Arabian Sea derives primarily from upwelling induced by strong southwest winds during June, July, and August. Indian Ocean summer monsoon winds are, in turn, driven by differential heating between the Asian continent and the Indian ocean to the south. This differential heating produces a strong pressure gradient resulting in southwest monsoon winds and both coastal and divergent upwelling off the Arabian Peninsula. Over geologic time scales (10(exp 4) to 10(exp 6) years), monsoon wind strength is sensitive to changes in boundary conditions which influence this pressure gradient. Important boundary conditions include the seasonal distribution of solar radiation, global ice volume, Indian Ocean sea surface temperature, and the elevation and albedo of the Asian continent. To the extent that these factors influence monsoon wind strength, they also influence upwelling and productivity. In addition, however, productivity associated with upwelling can be decoupled from the strength of the summer monsoon winds via ocean mechanisms which serve to inhibit or enhance the nutrient supply in the intermediate waters of the Indian Ocean, the source for upwelled waters in the Arabian Sea. To differentiate productivity associated with wind-induced upwelling from that associated with other components of the system such as nutrient sequestering in glacial-age deep waters, we employ a strategy which monitors independent components of the oceanic and atmospheric subsystems. Using sediment records from the Owen Ridge, northwest Arabian Sea, we monitor the strength of upwelling and productivity using two independent indicators, percent G. bulloides and opal accumulation. We monitor the strength of southwest monsoon winds by measuring the grain-size of lithogenic dust particles blown into the Arabian Sea from the surrounding deserts of the Somali and Arabian Peninsulas. Our current hypothesis is that the variability associated

  2. Tectonic development of the SW Arabian Plate margin within the central Arabian flank of the Red Sea rift system

    NASA Astrophysics Data System (ADS)

    Szymanski, E.; Stockli, D. F.; Johnson, P. R.; Kattan, F. H.; Cosca, M. A.

    2009-12-01

    The Red Sea rift system is a prime example of continental rifting and has contributed significantly to our understanding of the geologic processes that manage the rupture of continental lithosphere. Using a combined geo- and thermochronometric approach, we explore the modes and mechanisms of rift margin development by studying Red Sea rift-related geologic products along the central Saudi Arabian flank of the rift system, north of Jeddah. We use apatite and zircon (U-Th)/He thermochronometry and whole-rock 40Ar/39Ar dating of basalt to define the spatiotemporal relationship between rift flank extensional structures and rift-related harrat volcanism. This technical approach permits the reconstruction of the tectonic margin from early rift architecture, to strain distribution during progressive rifting, and through subsequent whole-scale modifications of the rift flank due to thermal and isostatic factors. Constraints on the dynamics of rift flank deformation are achieved through the collection of geologic samples along long-baseline thermochronometric transects that traverse the entire Arabian shield from the coastal escarpment to the inland Paleozoic sedimentary cover sequences. Long-baseline transects resolve the timing of rift flank uplift and reveal the pattern of lithospheric modification during the rupturing of continental lithosphere. Locally, short-baseline elevation transects map the footwall exhumation of major normal faults that delineate both the modern rift margin and inland extensional basins such as the NW-trending Hamd-Jizil basin, a prominent syn-extensional basin comprised of two distinct half-grabens (Jizil and Hamd) located NW of Medina. Diffuse lithospheric extension during the Oligo-Miocene affected a widespread area well inboard from the modern rift margin; samples from footwall blocks that bound the inland Jizil and Hamd half-grabens yield apatite (U-Th)/He cooling ages of 14.7 ± 0.9 Ma and 24.5 ± 1.5 Ma, respectively. The mid-Miocene age

  3. Geochemical evidence for anoxic deep water in the Arabian Sea during the last glaciation

    SciTech Connect

    Sarkar, A.; Bhattacharya, S.K.; Sarin, M.M. )

    1993-03-01

    Various paleoceanographic studies have indicated that the deep ocean was probably depleted in dissolved oxygen during the last glacial period ([approximately]18 kyr B.P.; [delta][sup 18]O, stage 2) compared to present time. However, direct evidence of low oxygen content in the deep waters has been lacking. Here, the authors report geochemical evidence of near anoxic conditions in the deep Arabian Sea during the entire last glacial cycle ([delta][sup 18]O; stages 2, 3, and 4). Anoxia is inferred from the concomitant enrichment of organic carbon and authigenic uranium in the glacial sections of a core from the deep eastern Arabian Sea. The anoxic conditions during the last glacial period, probably caused by a change in deep water circulation, evidently enhanced preservation of organic matter and simultaneous removal of uranium from seawater. 57 refs., 3 figs., 2 tabs.

  4. The phytoplankton bloom in the northwestern Arabian Sea during the southwest monsoon of 1979

    NASA Technical Reports Server (NTRS)

    Brock, John C.; Mcclain, Charles R.; Luther, Mark E.; Hay, William W.

    1991-01-01

    The present study investigates the biological variability of the northwestern Arabian Sea during the 1979 southwest monsoon by the synthesis of satellite ocean color remote sensing with an analysis of in situ hydrographic and meteorological data sets and the results of wind-driven modeling of upper-ocean circulation. The phytoplankton bloom peaked during August-September, extended from the Oman coast to about 65 deg E, and lagged behind the development of open-sea upwelling by at least 1 mo. The pigment distributions, hydrographic data, and model results all suggest that the boom was driven by spatially distinct upward nutrient fluxes to the euphotic zone forced by the physical processes of coastal upwelling and offshore Ekman pumping. Coastal upwelling was evident from May through September, yielded the most extreme concentrations of phytoplankton biomass, and, along the Arabian coast, was limited to the continental shelf in the promotion of high concentrations of phytoplankton.

  5. Variability of the Arabian Sea upwelling and intensity of the oxygen minimum zone over the late Pleistocene and Holocene

    NASA Astrophysics Data System (ADS)

    Gaye, Birgit; Böll, Anna; Rixen, Tim; Emeis, Kay-Christian; Ramaswamy, Venkitasubramani

    2016-04-01

    The northern Arabian Sea is one of the main oceanic regions with a permanent low oxygen layer at intermediate water depth that results in water column denitrification. While glacial/interglacial variations in the Arabian Sea oxygen minimum zone (OMZ) are relatively well studied, little is known about the spatial and temporal extent of mid-water oxygen throughout the Holocene. We compared alkenone derived sea surface temperatures of the last 25 kyrs from a core in the northern Arabian Sea with a core from the monsoonal upwelling area off Oman. The difference between the two temperature reconstructions indicates that monsoonal upwelling occurred during warm interstadials and during the entire Holocene. δ15N curves show that denitrification also matched with monsoonal upwelling. Comparison of δ15N records from different locations in the Arabian Sea reveal a Holocene shift in the location of the core OMZ from the northwestern (early Holocene) to the northeastern Arabian Sea (late Holocene). This shift was caused by (i) spatial differences in oxygen demand, caused by changes in SW- and NE-monsoon intensities and associated productivity changes, as well as (ii) changes in mid-water ventilation facilitated by sea level rise and inflow of Persian Gulf and Red Sea Water leading and changes of ventilation by Indian Ocean Central Water .

  6. Deglacial temperature patterns in the Arabian Sea and mechanisms for Indian monsoon failure

    NASA Astrophysics Data System (ADS)

    Tierney, J. E.; Pausata, F. S. R.; deMenocal, P. B.

    2015-12-01

    Both paleoclimate data and climate model simulations demonstrate that the Indian monsoon system responds to remote coolings in the North Atlantic. The textbook examples are the stadial events associated with the last deglaciation — the Younger Dryas and Heinrich Stadial 1 — when the monsoon weakened dramatically and caused drying throughout the Indian Ocean rim. The mechanism by which the North Atlantic influences the monsoon system is not completely clear: locally cool SSTs, increases in continental albedo, and southward migration of the intertropical convergence zone have all been raised as possibilities. Here we synthesize biomarker and foraminiferal estimates of temperature to study the evolution of the Arabian Sea water column during the deglaciation and test hypotheses of monsoon failure during stadials. Alkenone and Mg/Ca data clearly indicate that the Arabian Sea cools during the YD and H1, although H1 cooling is partly obscured by the overall warming trend associated with orbital forcing and rising greenhouse gases. In contrast, TEX86 data record warmings during the YD and H1. The stark difference between the TEX86 response and the alkenone and foraminiferal data, as well as comparison with climate model simulations, indicates that TEX86 is most likely acting as a subsurface temperature proxy in the Arabian Sea over these timescales. Taken together, the paleoclimate data describe a pattern of surface cooling and subsurface warming in response to North Atlantic cooling. This oceanographic response is in excellent agreement with both timeslice and transient model simulations spanning the last deglaciation, and strongly supports the hypothesis that locally cool SSTs are a requisite for monsoon failure. Furthermore, subsurface warming causes a destratification of the Arabian Sea water column and provides a mechanism for previously observed reductions in productivity during stadial events.

  7. Moisture transport over the Arabian Sea associated with summer rainfall over Pakistan in 1994 and 2002

    NASA Astrophysics Data System (ADS)

    Ullah, Kalim; Gao, Shouting

    2012-05-01

    In this study, we aimed to elucidate the critical role of moisture transport affecting monsoon activity in two contrasting summers over the Arabian Sea during the years 1994, a relatively wet year, and 2002, a relatively dry year. A comprehensive diagnostic evaluation and comparisons of the moisture fields were conducted; we focused on the precipitation and evaporation as well as the moisture transport and its divergence or convergence in the atmosphere. Monthly mean reanalysis data were obtained from the National Centers for Environmental Prediction (NCEP-I and -II). A detailed evaluation of the moisture budgets over Pakistan during these two years was made by calculating the latent energy flux at the surface ( E-P) from the divergence of the total moisture transport. Our results confirm the moisture supply over the Arabian Sea to be the major source of rainfall in Pakistan and neighboring regions. In 1994, Pakistan received more rainfall compared to 2002 during the summer monsoon. Moisture flow deepens and strengthens over Arabian Sea during the peak summer monsoon months of July and August. Our analysis shows that vertically integrated moisture transport flux have a significant role in supplying moisture to the convective centers over Pakistan and neighboring regions from the divergent regions of the Arabian Sea and the Bay of Bengal. Moreover, in 1994, a deeper vertically integrated moisture convergence progression occurred over Pakistan compared to that in 2002. Perhaps that deeper convergence resulted in a more intense moisture depression over Pakistan and also caused more rainfall in 1994 during the summer monsoon. Finally, from the water budget analysis, it has been surmised that the water budget was larger in 1994 than in 2002 during the summer monsoon.

  8. The impact of dust storms on the Arabian Peninsula and the Red Sea

    NASA Astrophysics Data System (ADS)

    Jish Prakash, P.; Stenchikov, G.; Kalenderski, S.; Osipov, S.; Bangalath, H.

    2015-01-01

    Located in the dust belt, the Arabian Peninsula is a major source of atmospheric dust. Frequent dust outbreaks and some 15 to 20 dust storms per year have profound effects on all aspects of human activity and natural processes in this region. To quantify the effect of severe dust events on radiation fluxes and regional climate characteristics, we simulated the storm that occurred from 18 to 20 March 2012 using a regional weather research forecast model fully coupled with the chemistry/aerosol module (WRF-Chem). This storm swept over a remarkably large area affecting the entire Middle East, northeastern Africa, Afghanistan, and Pakistan. It was caused by a southward propagating cold front, and the associated winds activated the dust production in river valleys of the lower Tigris and Euphrates in Iraq; the coastal areas in Kuwait, Iran, and the United Arab Emirates; the Rub al Khali, An Nafud, and Ad Dahna deserts; and along the Red Sea coast on the west side of the Arabian Peninsula. Our simulation results compare well with available ground-based and satellite observations. We estimate the total amount of dust generated by the storm to have reached 94 Mt. Approximately 78% of this dust was deposited within the calculation domain. The Arabian Sea and Persian Gulf received 5.3 Mt and the Red Sea 1.2 Mt of dust. Dust particles bring nutrients to marine ecosystems, which is especially important for the oligotrophic Northern Red Sea. However, their contribution to the nutrient balance in the Red Sea remains largely unknown. By scaling the effect of one storm to the number of dust storms observed annually over the Red Sea, we estimate the annual dust deposition to the Red Sea, associated with major dust storms, to be 6 Mt.

  9. The impact of dust storms on the Arabian Peninsula and the Red Sea

    NASA Astrophysics Data System (ADS)

    Jish Prakash, P.; Stenchikov, G.; Kalenderski, S.; Osipov, S.; Bangalath, H.

    2014-07-01

    Located in the dust belt, the Arabian Peninsula is a major source of atmospheric dust. Frequent dust outbreaks and some 15 to 20 dust storms per year have profound effects on all aspects of human activity and natural processes in this region. To quantify the effect of severe dust events on radiation fluxes and regional climate characteristics, we simulated the storm that occurred on 18-20 March 2012 using a regional weather research forecast model fully coupled with the chemistry/aerosol module (WRF-Chem). This storm swept over a remarkably large area affecting the entire Middle East, North-Eastern Africa, Afghanistan and Pakistan. It was caused by a southward propagating cold front and associated winds activated the dust production in river valleys of the lower Tigris and Euphrates in Iraq, the coastal areas in Kuwait, Iran, and the United Arab Emirates, Rub al Khali, An Nafud and Ad Dahna deserts, and along the Red Sea coast on the west side of the Arabian Peninsula. Our simulation results compare well with available ground-based and satellite observations. The total amount of dust generated by the storm reached 93.76 Mt. About 80% of this amount deposited within the calculation domain. The Arabian Sea and Persian Gulf received 5.3 Mt, and the Red Sea 1.2 Mt. Dust particles bring nutrients to marine ecosystems, which is especially important for the oligothrophic Northern Red Sea. However, their contribution to the nutrient balance in the Red Sea remains largely unknown. By scaling the effect of one storm to the number of dust storms observed annually over the Red Sea, we roughly estimate the annual dust deposition to the Red Sea to be 6 Mt.

  10. The world's most isolated and distinct whale population? Humpback whales of the Arabian Sea.

    PubMed

    Pomilla, Cristina; Amaral, Ana R; Collins, Tim; Minton, Gianna; Findlay, Ken; Leslie, Matthew S; Ponnampalam, Louisa; Baldwin, Robert; Rosenbaum, Howard

    2014-01-01

    A clear understanding of population structure is essential for assessing conservation status and implementing management strategies. A small, non-migratory population of humpback whales in the Arabian Sea is classified as "Endangered" on the IUCN Red List of Threatened Species, an assessment constrained by a lack of data, including limited understanding of its relationship to other populations. We analysed 11 microsatellite markers and mitochondrial DNA sequences extracted from 67 Arabian Sea humpback whale tissue samples and compared them to equivalent datasets from the Southern Hemisphere and North Pacific. Results show that the Arabian Sea population is highly distinct; estimates of gene flow and divergence times suggest a Southern Indian Ocean origin but indicate that it has been isolated for approximately 70,000 years, remarkable for a species that is typically highly migratory. Genetic diversity values are significantly lower than those obtained for Southern Hemisphere populations and signatures of ancient and recent genetic bottlenecks were identified. Our findings suggest this is the world's most isolated humpback whale population, which, when combined with low population abundance estimates and anthropogenic threats, raises concern for its survival. We recommend an amendment of the status of the population to "Critically Endangered" on the IUCN Red List. PMID:25470144

  11. Metagenomic analysis of nitrogen and methane cycling in the Arabian Sea oxygen minimum zone

    PubMed Central

    Kox, Martine A.R.; Villanueva, Laura; Jetten, Mike S.M.

    2016-01-01

    Oxygen minimum zones (OMZ) are areas in the global ocean where oxygen concentrations drop to below one percent. Low oxygen concentrations allow alternative respiration with nitrate and nitrite as electron acceptor to become prevalent in these areas, making them main contributors to oceanic nitrogen loss. The contribution of anammox and denitrification to nitrogen loss seems to vary in different OMZs. In the Arabian Sea, both processes were reported. Here, we performed a metagenomics study of the upper and core zone of the Arabian Sea OMZ, to provide a comprehensive overview of the genetic potential for nitrogen and methane cycling. We propose that aerobic ammonium oxidation is carried out by a diverse community of Thaumarchaeota in the upper zone of the OMZ, whereas a low diversity of Scalindua-like anammox bacteria contribute significantly to nitrogen loss in the core zone. Aerobic nitrite oxidation in the OMZ seems to be performed by Nitrospina spp. and a novel lineage of nitrite oxidizing organisms that is present in roughly equal abundance as Nitrospina. Dissimilatory nitrate reduction to ammonia (DNRA) can be carried out by yet unknown microorganisms harbouring a divergent nrfA gene. The metagenomes do not provide conclusive evidence for active methane cycling; however, a low abundance of novel alkane monooxygenase diversity was detected. Taken together, our approach confirmed the genomic potential for an active nitrogen cycle in the Arabian Sea and allowed detection of hitherto overlooked lineages of carbon and nitrogen cycle bacteria. PMID:27077014

  12. Metagenomic analysis of nitrogen and methane cycling in the Arabian Sea oxygen minimum zone.

    PubMed

    Lüke, Claudia; Speth, Daan R; Kox, Martine A R; Villanueva, Laura; Jetten, Mike S M

    2016-01-01

    Oxygen minimum zones (OMZ) are areas in the global ocean where oxygen concentrations drop to below one percent. Low oxygen concentrations allow alternative respiration with nitrate and nitrite as electron acceptor to become prevalent in these areas, making them main contributors to oceanic nitrogen loss. The contribution of anammox and denitrification to nitrogen loss seems to vary in different OMZs. In the Arabian Sea, both processes were reported. Here, we performed a metagenomics study of the upper and core zone of the Arabian Sea OMZ, to provide a comprehensive overview of the genetic potential for nitrogen and methane cycling. We propose that aerobic ammonium oxidation is carried out by a diverse community of Thaumarchaeota in the upper zone of the OMZ, whereas a low diversity of Scalindua-like anammox bacteria contribute significantly to nitrogen loss in the core zone. Aerobic nitrite oxidation in the OMZ seems to be performed by Nitrospina spp. and a novel lineage of nitrite oxidizing organisms that is present in roughly equal abundance as Nitrospina. Dissimilatory nitrate reduction to ammonia (DNRA) can be carried out by yet unknown microorganisms harbouring a divergent nrfA gene. The metagenomes do not provide conclusive evidence for active methane cycling; however, a low abundance of novel alkane monooxygenase diversity was detected. Taken together, our approach confirmed the genomic potential for an active nitrogen cycle in the Arabian Sea and allowed detection of hitherto overlooked lineages of carbon and nitrogen cycle bacteria. PMID:27077014

  13. Recent changes in the Arabian Sea ecosystem linked to large-scale climatic events

    NASA Astrophysics Data System (ADS)

    Goes, Joaquim; do Rosario Gomes, Helga; Prabhu Matondkar, Shivprasad; de Rada, Sergio; Chai, Fei; Dwivedi, Rashmin; Thoppil, Prasad; Al-Azri, Adnan; Basu, Subhajit

    2014-05-01

    Between 1994 and 1996, the Arabian Sea became the focus of a multinational effort directed at studying ocean biological and physical processes and their links to the global carbon cycle. The results of this comprehensive, multi-disciplinary effort known as the Joint Global Flux Study (JGOFS) program provided important indications of the role of the reversal of the monsoons and the extremes in wind forcing, in causing the greatest seasonal variability of primary production and vertical flux of carbon observed in any of the world's oceans. Since the end of the JGOFS program, most contemporary shipboard investigations of primary productivity and biogeochemical processes have come mostly from small programmatically focused shipboard cruises that have been regional in scope. On the other hand, most recent large basin-scale studies have relied mainly on coupled physical-biological models and on satellite data. Here we present a synthesis of recent observations from shipboard cruises and satellites, together with modeling studies which highlight the extreme sensitivity of the Arabian Sea ecosystem to climatic events. We posit that the Arabian Sea ecosystem is undergoing rapid change as a result of changes in physical processes tied to climate change.

  14. The World's Most Isolated and Distinct Whale Population? Humpback Whales of the Arabian Sea

    PubMed Central

    Collins, Tim; Minton, Gianna; Findlay, Ken; Leslie, Matthew S.; Ponnampalam, Louisa; Baldwin, Robert; Rosenbaum, Howard

    2014-01-01

    A clear understanding of population structure is essential for assessing conservation status and implementing management strategies. A small, non-migratory population of humpback whales in the Arabian Sea is classified as “Endangered” on the IUCN Red List of Threatened Species, an assessment constrained by a lack of data, including limited understanding of its relationship to other populations. We analysed 11 microsatellite markers and mitochondrial DNA sequences extracted from 67 Arabian Sea humpback whale tissue samples and compared them to equivalent datasets from the Southern Hemisphere and North Pacific. Results show that the Arabian Sea population is highly distinct; estimates of gene flow and divergence times suggest a Southern Indian Ocean origin but indicate that it has been isolated for approximately 70,000 years, remarkable for a species that is typically highly migratory. Genetic diversity values are significantly lower than those obtained for Southern Hemisphere populations and signatures of ancient and recent genetic bottlenecks were identified. Our findings suggest this is the world's most isolated humpback whale population, which, when combined with low population abundance estimates and anthropogenic threats, raises concern for its survival. We recommend an amendment of the status of the population to “Critically Endangered” on the IUCN Red List. PMID:25470144

  15. Bio-Optical Properties of the Arabian Sea as Determined by In-Situ and SeaWifs Data

    NASA Technical Reports Server (NTRS)

    Trees, Charles C.

    1998-01-01

    The overall objective of this work was to characterize optical and fluorescence properties in the euphotic zone during two British Ocean Flux Study (BOFS) Arabian Sea cruises. This was later expanded in 1995 to include three U.S. Joint Global Ocean Flux Study (JGOFS) Arabian Sea Cruises. The region was to be divided into one or more "bio-optical provinces", within each of which a single set of regression models was to be developed to relate the vertical distribution of irradiance attenuation and normalized fluorescence (SF and NF) to remote sensing reflectance and diffuse attenuation coefficient [K(490)]. The working hypothesis was that over relatively large spatial and temporal scales, the vertical profiles of bio-optical properties were predictable.

  16. Physical processes affecting availability of dissolved silicate for diatom production in the Arabian Sea

    NASA Technical Reports Server (NTRS)

    Young, David K.; Kindle, John C.

    1994-01-01

    A passive tracer to represent dissolved silicate concentrations, with biologically realistic uptake kinetics, is successfully incorporated into a three-dimensional, eddy-resolving, ocean circulation model of the Indian Ocean. Hypotheses are tested to evaluate physical processes which potentially affect the availability of silicate for diatom production in the Arabian Sea. An alternative mechanism is offered to the idea that open ocean upwelling is primarily responsible for the high, vertical nutrient flux and consequent large-scale phytoplankton bloom in the northwestern Arabian Sea during the southwest monsoon. Model results show that dissolved silicate in surface waters available for uptake by diatoms is primarily influenced by the intensity of nearshore upwelling from soutwest monsoonal wind forcing and by the offshore advective transport of surface waters. The upwelling, which in the model occurs within 200 +/- 50 km of the coast, appears to be a result of a combination of coastal upwelling, Elkman pumping, and divergence of the coastal flow as it turns offshore. Localized intensifications of silicate concentrations appear to be hydrodynamically driven and geographically correlated to coastal topographic features. The absence of diatoms in sediments of the eastern Arabian Basin is consistent with modeled distributional patterns of dissolved silicate resulting from limited westward advection of upwelled coastal waters from the western continental margin of India and rapid uptake of available silicate by diatoms. Concentrations of modeled silicate become sufficiently low to become unavailable for diatom production in the eastern Arabian Sea, a region between 61 deg E and 70 deg E at 8 deg N on the south, with the east and west boundaries converging on the north at approximately 67 deg E, 20 deg N.

  17. Controlling factors of the oxygen balance in the Arabian Sea's OMZ

    NASA Astrophysics Data System (ADS)

    Resplandy, L.; Lévy, M.; Bopp, L.; Echevin, V.; Pous, S.; Sarma, V. V. S. S.; Kumar, D.

    2012-12-01

    The expansion of OMZs (oxygen minimum zones) due to climate change and their possible evolution and impacts on the ecosystems and the atmosphere are still debated, mostly because of the unability of global climate models to adequatly reproduce the processes governing OMZs. In this study, we examine the factors controlling the oxygen budget, i.e. the equilibrium between oxygen sources and sinks in the northern Arabian Sea OMZ using an eddy-resolving biophysical model. Our model confirms that the biological consumption of oxygen is most intense below the region of highest productivity in the western Arabian Sea. The oxygen drawdown in this region is counterbalanced by the large supply of oxygenated waters originated from the south and advected horizontally by the western boundary current. Although the biological sink and the dynamical sources of oxygen compensate on annual average, we find that the seasonality of the dynamical transport of oxygen is 3 to 5 times larger than the seasonality of the biological sink. In agreement with previous findings, the resulting seasonality of oxygen concentration in the OMZ is relatively weak, with a variability of the order of 15% of the annual mean oxygen concentration in the oxycline and 5% elsewhere. This seasonality primarily arises from the vertical displacement of the OMZ forced by the monsoonal reversal of Ekman pumping across the basin. In coastal areas, the oxygen concentration is also modulated seasonally by lateral advection. Along the western coast of the Arabian Sea, the Somali Current transports oxygen-rich waters originated from the south during summer and oxygen-poor waters from the northeast during winter. Along the eastern coast of the Arabian Sea, we find that the main contributor to lateral advection in the OMZ is the Indian coastal undercurrent that advects southern oxygenated waters during summer and northern low-oxygen waters during winter. In this region, our model indicates that oxygen concentrations are

  18. The role of salinity on the dynamics of the Arabian Sea mini warm pool

    NASA Astrophysics Data System (ADS)

    Nyadjro, Ebenezer S.; Subrahmanyam, Bulusu; Murty, V. S. N.; Shriver, Jay F.

    2012-09-01

    Warmer (>28°C) sea surface temperature (SST) occurs in the South Eastern Arabian Sea (SEAS, 5°N-13°N, 65°E-76°E) during March-April, and is known as the Arabian Sea Mini Warm Pool (ASMWP). In this study, we address the role of salinity and the upper layer heat and salt budgets in the formation and collapse of this ASMWP. An assessment of Level 3 sea surface salinity (SSS) data from the Soil Moisture and Ocean Salinity (SMOS) satellite mission for the year 2010 shows that SMOS is able to capture the SSS variability in the SEAS. Analysis of temperature, salinity and currents from the Hybrid Coordinate Ocean Model during 2003-06, and, in situ temperature and salinity data from Argo floats during 2003-06 for the SEAS revealed that low salinity waters cap the top 60 m of the SEAS in January-February. This minimum salinity was concurrent with the formation of a barrier layer and with the time when the SEAS gained little net heat flux and the equatorward flowing East India Coastal Current (EICC) fed low saline waters into the SEAS. Subsequently, the net heat flux increased to a peak value under the increased salinity stratification, leading to the formation of the ASMWP in March-April. The ASMWP collapsed by May due to increase in SSS and the associated weakening of the salinity stratification. The monsoon onset vortex in May 2004 could be related to the minimum SSS that occurred in February 2004, followed by higher SST and heat content of the ASMWP in April 2004.

  19. Mesoscale variability of water masses in the Arabian Sea as revealed by ARGO floats

    NASA Astrophysics Data System (ADS)

    Carton, X.; L'Hegaret, P.

    2011-06-01

    By analysing ARGO float data over the last four years, some aspects of the mesoscale variability of water masses in the Arabian Sea are described. The Red Sea Water outflow is strong in the Southwestern Gulf of Aden, in particular when a cyclonic gyre predominates in this region. Salinities of 36.5 and temperatures of 16 °C are found there between 600 and 1000 m depths. The Red Sea Water is more dilute in the eastern part of the Gulf, and fragments of this water mass can be advected offshore across the gulf or towards its northern coast by the regional gyres. The Red Sea Water outflow is also detected along the northeastern coast of Socotra, and fragments of RSW are found between one and three degrees of latitude north of this island. In the whole Gulf of Aden, the correlation between the deep motions of the floats and the SSH measured by altimetry is strong, at regional scale. The finer scale details of the float trajectories are more often related to the anomalous water masses that they encounter. The Persian Gulf Water (PGW) is found in the float profiles near Ras ash Sharbatat (near 57° E, 18° N), again with 36.5 in salinity and about 18-19 °C in temperature. These observations were achieved in winter when the southwestward monsoon currents can advect PGW along the South Arabian coast. Fragments of PGW are found in the Arabian Sea between 18 and 20° N and 63 and 65° E, showing that this water mass can escape the Gulf of Oman southeastward, in particular during summer.

  20. Spacebased Observations of the Oceanic Responses to Monsoons in South China Sea and Arabian Sea

    NASA Technical Reports Server (NTRS)

    Xie, Xiao-Su; Liu, W. Timothy

    2000-01-01

    A large percentage of the world's population and their agrarian economy must endure the vagaries of the monsoons over the tropical oceans between Africa and the Philippines. We know very little about the oceanic responses to changes of the monsoon in the South China Sea (SCS), which is under the influence of the East Asian Monsoon System, and the Arabian Sea (AS), which is dominated by the Indian Monsoon System; oceanic observations are sparse in both regions. Data from spaceborne microwave scatterometers and radiometers have been used to estimate the two major atmospheric forcing, momentum flux and latent heat flux (LHF), which change with the monsoon winds. Spaceborne sensors also observed the surface signatures of the oceanic response: SST and sea level changes (SLC. Sufficient durations of these data have recently become available to allow the meaningful studies of the annual cycles and interannual anomalies. In SCS, the winter monsoon is strong and steady but the summer monsoon is weak and has large intraseasonal fluctuations. In AS, the summer monsoon is much stronger than the winter monsoon. Significant correlations between LHF and SST tendency, and between curl of wind stress and SLC are found in both oceans. In the north SCS, winds are strong and dry, LHF is high, and ocean cooling is also large in fall; LHF is low and the ocean warms up in spring. In AS, LHF and SST tendency have a semi annual period; LHF is high in summer when the wind is strong and in winter when the wind is dry. Along the coast of Oman, the strong summer southwest monsoon causes intense upwelling, low SST and LHF in summer; such wind-driven SST changes is not as obvious along the Vietnam coast because of the weaker summer monsoon. The negative correlation between curl of wind stress and SLC found in the central basins of both SCS and AS agrees with a simple Ekman pumping scenario. Cyclonic winds drive surface divergence and upwelling in the ocean; the rise of the thermocline causes

  1. An overview of historical harmful algae blooms outbreaks in the Arabian Seas.

    PubMed

    Al Shehhi, Maryam R; Gherboudj, Imen; Ghedira, Hosni

    2014-09-15

    Harmful algae blooms (HABs), often composed of oceanic plants called phytoplankton, are potentially harmful to the marine life, water quality, human health, and desalination plants, a chief source of potable water in the Arabian Gulf. The last decade has seen a noticeable increase in the frequency of HAB outbreaks in the Arabian Seas. This increase is mainly caused by the unprecedented economic growth in the region. The increased human activities in the region have added more stress to the marine environment and contributed to the changes observed in the properties of the marine ecosystem: high temperature and salinity, high evaporation rates, limited freshwater inflow, shallow nature, pollution. However, very few studies that cover the HAB outbreaks, causes, impacts and biological characteristics over the region have been published. This work presents a comprehensive overview of historical HAB outbreaks recorded in the region, and investigate their causes and impact, and seasonal variability. PMID:25038981

  2. A Model Study on Understanding the Influence of Arabian Sea Mini Warm Pool on Monsoon Onset Vortex Formation

    NASA Astrophysics Data System (ADS)

    Deepa, R.; Gnanaseelan, C.; Deshpande, M.; Salvekar, P. S.

    2012-09-01

    The Arabian Sea Mini Warm Pool (MWP) is a zone of anomalously high Sea Surface Temperature (SST) in the Arabian Sea over which the monsoon onset vortex (OV) is believed to form. In the present study it is shown that this MWP is a key parameter in the development of the onset vortex. Atmospheric model experiments are carried out with and without MWP to understand the mechanisms for the formation of the OV. The model failed to simulate the OV with the cold SST advocating the importance of the MWP for the formation of the OV. The MWP is found to favor the formation of the onset vortex in the east central Arabian Sea by increasing the horizontal shear and decreasing the vertical wind shear.

  3. Magmatic history of Red Sea rifting: perspective from the central Saudi Arabian coastal plain.

    USGS Publications Warehouse

    Pallister, J.S.

    1987-01-01

    An early stage of magmatism related to Red Sea rifting is recorded by a Tertiary dyke complex and comagmatic volcanic rocks exposed on the central Saudi Arabian coastal plain. Field relations and new K/Ar dates indicate episodic magmatism from approx 30 m.y. to the present day and rift-related magmatism as early as 50 m.y. Localized volcanism and sheeted dyke injection ceased at approx 20 m.y. and were replaced by the intrusion of thick gabbro dykes, marking the onset of sea-floor spreading in the central Red Sea. Differences in the depths and dynamics of mantle-melt extraction and transport may account for the transition from mixed alkaline-subalkaline bimodal magmatism of the pre-20 m.y. rift basin to exclusively subalkaline (tholeiitic) magmatism of the Red Sea spreading axis and the alkali basalt volcanism inland.-L.C.H.

  4. Current and thermohaline characteristics of the Arabian Sea during January 1998

    NASA Astrophysics Data System (ADS)

    Chen, Meixiang; Zuo, Juncheng; Li, Peiliang; Du, Ling; Li, Lei

    2007-04-01

    Based on a ship survey during January 1998, the characteristics of the flow, the thermohaline properties and the volume transport of the Arabian Sea are discussed. A strong westward flow exists between 10.5°N and 11°N, part of which turns to the south as the Somali current near the coast at about 10°N and the rest turns north. At the passage between the African continent and the Socotra Island, the northern branch separates into two flows: the left one enters the passage and the right one flows eastward along the southern slope of the island. Off the island the flow separates once more, most of it meandering northeast and a small fraction flowing southeast. Volume transport calculation suggests that the tidal transport is one or two orders of magnitude smaller than the total transport in this region and it becomes more important near the coast. The average velocity of the flow in the upper layer (0 150 m) is about 20 cm s-1, with a maximum of 53 cm s-1 appearing east of the Socotra Island, and the subsurface layer (200 800 m) has an average velocity of 8.6 cm s-1; the velocity becomes smaller at greater depths. The depth of the seasonal thermocline is about 100 m, above which there is a layer with well mixed temperature and dissolved oxygen. High-salinity and oxygen-rich water appears near the surface of the northern Arabian Sea; a salinity maximum and oxygen minimum at 100 m depth along 8°N testifies the subduction of surface water from the northern Arabian Sea. Waters from the Red Sea and the Persian Gulf also influence the salinity of the area.

  5. The Northeast Monsoon's Impact on Mixing, Phytoplankton Biomass and Nutrient Cycling in the Arabian Sea

    NASA Technical Reports Server (NTRS)

    Wiggert, J. D.; Jones, B. H.; Dickey, T. D.; Brink, K. H.; Weller, R. A.; Marra, J.; Codispoti, L. A.

    2000-01-01

    In the northern Arabian Sea, atmospheric conditions during the Northeast (winter) Monsoon lead to deep convective mixing. Due to the proximity of the permanent pyncnocline to the sea surface, this mixing does not penetrate below 125 m. However, a strong nitracline is also present and the deep convection results in significant nitrate flux into the surface waters. This leads to nitrate concentrations over the upper 100 m that exceed 4 micrometers toward the end of the Monsoon. During the 1994/1995 US JGOFS/Arabian Sea expedition, the mean areal gross primary production over two successive Northeast Monsoons was determined to be 1.35gC/sq m/d. Thus, despite the deep penetrative convection, high rates of primary productivity were maintained. An interdisciplinary model was developed to elucidate the biogeochemical processes involved in supporting the elevated productivity. This model consists of a 1-D mixed-layer model coupled to a set of equations that tracked phytoplankton growth and the concentration of the two major nutrients (nitrate and ammonium). Zooplankton grazing was parameterized by rate constant determined by shipboard experiments. Model boundary conditions consist of meteorological time-series measured from the surface buoy that was part of the ONR Arabian Sea Experiment's central mooring. Our numerical experiments show that elevated surface evaporation, and the associated salinization of the mixed layer, strongly contributes to the frequency and penetration depth of the observed convective mixing. Cooler surface temperatures, increased nitrate entrainment, reduced water column stratification, and lower near-surface chlorophyll a concentrations all result from this enhanced mixing. The model also captured a dependence on regenerated nitrogen observed in nutrient uptake experiments performed during the Northeast Monsoon. Our numerical experiments also indicate that variability in mean pycnocline depth causes up to a 25% reduction in areal chlorophyll a

  6. Lithospheric and Upper-Mantle Structure of the Red Sea and Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Hansen, S. E.; Schwartz, S. Y.; Rodgers, A. J.; Gaherty, J. B.; Al-Amri, A. M.

    2007-12-01

    Using broadband seismic data recorded by various networks, a variety of techniques have been employed to investigate the lithospheric and upper-mantle structure of the Red Sea and Arabian Peninsula. This presentation will summarize our findings and conclusions about the tectonic evolution and current state of the Arabian Plate. S-wave receiver functions provide constraints on the lithospheric thickness and reveal very thin lithosphere (40-80 km) along the Red Sea coast, which thickens rapidly toward the interior of the Arabian Shield (100-120 km). A step of 20-40 km in lithospheric thickness is also observed at the Shield-Platform boundary. Mantle anisotropy has been analyzed using shear-wave splitting of teleseismic SKS waveforms. The consistent north-south oriented fast directions are not adequately explained by end-member models of fossilized anisotropy and present-day plate motion and have instead been explained by a combination of plate- and density-driven flow in the asthenosphere. Further constraints on the upper mantle velocity and anisotropy have been obtained by jointly inverting the receiver function constraints with frequency dependent surface wave phase delays. The results demonstrate that the thin lithospheric lid is underlain by a pronounced low-velocity zone and that anisotropy is required in both the lithosphere and asthenosphere. Attenuation and thermal estimates are also being explored and preliminary results will be presented. The combined results of these studies support a two-stage rifting history for the Red Sea, where extension and erosion by asthenospheric flow are responsible for variations in the lithospheric thickness. These lithospheric variations guide asthenospheric flow beneath western Arabia and the Red Sea, leading to a large-scale thermal anomaly that is associated with Cenozoic uplift and volcanism. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National

  7. Interannual variability in phytoplankton blooms observed in the northwestern Arabian Sea during the southwest monsoon

    NASA Technical Reports Server (NTRS)

    Brock, John C.; Mcclain, Charles R.

    1992-01-01

    Interannual changes in the strength and seasonal evolution of the 1979 through 1982 surface-level southwest monsoon winds are related to variations in the summer phytoplankton bloom of the northwestern Arabian Sea by synthesis of satellite ocean-color remote sensing with analysis of in-situ hydrographic and meteorological data sets. The 1979-1981 southwest monsoon phytoplankton blooms in the northwest Arabian Sea peaked during August-September, extended from the Omani coast to about 6 E, and appeared to lag the development of open-sea upwelling by at least 1 month. In all 3 years the bloom was driven by spatially distinct upward nutrient fluxes to the euphotic zone forced by the physical processes of coastal upwelling and offshore Ekman pumping. Coastal upwelling was evident from May through September, yielded the most extreme concentrations of phytoplankton biomass, and along the Omani coast was limited in its impact on upper ocean biological variability to the continental shelf. Ekman pumping stimulated the development of a broad open-ocean component of the southwest monsoon phytoplankton bloom oceanward of the Omani shelf. Phytoplankton biomass on the Omani continental shelf was increased during both the early and late phases of the 1980 southwest monsoon due to stronger coastal upwelling under the most intense southwesterly winds of the four summers investigated. Diminished coastal upwelling during the early phase of the weak 1982 southwest monsoon resulted in a coastal bloom that reached a mean phytoplankton-pigment concentration that was 28 percent of that seen in 1980. The lack of a strong regional northwestern Arabian Sea bloom in late summer 1982 is attributed to the development of persistent, shallow temperature stratification that rendered Ekman pumping less effective in driving upward nutrient fluxes.

  8. Mesoscale variability of water masses in the Arabian Sea as revealed by ARGO floats

    NASA Astrophysics Data System (ADS)

    Carton, X.; L'Hegaret, P.; Baraille, R.

    2012-03-01

    By analysing ARGO float data over the last four years, a few aspects of the mesoscale variability of water masses in the Arabian Sea are described. The Red Sea Outflow Water (RSOW) is concentrated in the Southwestern Gulf of Aden, in particular when a cyclonic gyre predominates in this region. Salinities of 36.5 and temperatures of 16 °C are found in this area at depths between 600 and 1000 m. RSOW is more dilute in the eastern part of the Gulf, where intense and relatively barotropic gyres mix it with Indian ocean Central Water. RSOW is also detected along the northeastern coast of Socotra, and fragments of RSOW are found between one and three degrees of latitude north of this island. In the whole Gulf of Aden, the correlation between the deep motions of the floats and the sea-level anomaly measured by altimetry is strong, at regional scale. The finer scale details of the float trajectories are not sampled by altimetry and are often related to the anomalous water masses that the floats encounter. The Persian Gulf Water (PGW) is found in the float profiles near Ras ash Sharbatat (near 57° E, 18° N), again with 36.5 in salinity and about 18-19 °C in temperature. These observations were achieved in winter when the southwestward monsoon currents can advect PGW along the South Arabian coast. Fragments of PGW were also observed in the Arabian Sea between 18 and 20° N and 63 and 65° E in summer, showing that this water mass can escape the Gulf of Oman southeastward, during that season. Kinetic energy distributions of floats with respect to distance or angle share common features between the two regions (Gulf of Aden and Arabian Sea), in particular peaks at 30, 50 and 150 km scales and along the axis of monsoon currents. Hydrological measurements by floats are also influenced by the seasonal variations of PGW and RSOW in these regions.

  9. Seasonal and interannual variations in the nitrogen cycle in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Rixen, T.; Baum, A.; Gaye, B.; Nagel, B.

    2014-10-01

    The Arabian Sea plays an important role in the marine nitrogen cycle because of its pronounced mid-water oxygen minimum zone (OMZ) in which bio-available nitrate (NO3-) is reduced to dinitrogen gas (N2). As the nitrogen cycle can respond fast to climate-induced changes in productivity and circulation, the Arabian Sea sediments are an important palaeoclimatic archive. In order to understand seasonal and interannual variations in the nitrogen cycle, nutrient data were obtained from the literature published prior to 1993, evaluated, and compared with data measured during five expeditions carried out in the framework of the Joint Global Ocean Flux Study (JGOFS) in the Arabian Sea in 1995 and during a research cruise of RV Meteor in 2007. The data comparison showed that the area characterized by a pronounced secondary nitrite maximum (SNM) was by 63% larger in 1995 than a similarly determined estimate based on pre-JGOFS data. This area, referred to as the core of the denitrifying zone, showed strong seasonal and interannual variations driven by the monsoon. During the SW monsoon, the SNM retreated eastward due to the inflow of oxygen-enriched Indian Ocean Central Water (ICW). During the NE monsoon, the SNM expanded westward because of the reversal of the current regime. On an interannual timescale, a weaker SW monsoon decreased the inflow of ICW from the equatorial Indian Ocean and increased the accumulation of denitrification tracers by extending the residence time of water in the SNM. This is supported by palaeoclimatic studies showing an enhanced preservation of accumulative denitrification tracers in marine sediments in conjunction with a weakening of the SW monsoon during the late Holocene.

  10. The Effect of the South Asia Monsoon on the Wind Sea and Swell Patterns in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Semedo, Alvaro

    2015-04-01

    Ocean surface gravity waves have a considerable impact on coastal and offshore infrastructures, and are determinant on ship design and routing. But waves also play an important role on the coastal dynamics and beach erosion, and modulate the exchanges of momentum, and mass and other scalars between the atmosphere and the ocean. A constant quantitative and qualitative knowledge of the wave patterns is therefore needed. There are two types of waves at the ocean surface: wind-sea and swell. Wind-sea waves are growing waves under the direct influence of local winds; as these waves propagate away from their generation area, or when their phase speed overcomes the local wind speed, they are called swell. Swell waves can propagate thousands of kilometers across entire ocean basins. The qualitative analysis of ocean surface waves has been the focus of several recent studies, from the wave climate to the air-sea interaction community. The reason for this interest lies mostly in the fact that waves have an impact on the lower atmosphere, and that the air-sea coupling is different depending on the wave regime. Waves modulate the exchange of momentum, heat, and mass across the air-sea interface, and this modulation is different and dependent on the prevalence of one type of waves: wind sea or swell. For fully developed seas the coupling between the ocean-surface and the overlaying atmosphere can be seen as quasi-perfect, in a sense that the momentum transfer and energy dissipation at the ocean surface are in equilibrium. This can only occur in special areas of the Ocean, either in marginal seas, with limited fetch, or in Open Ocean, in areas with strong and persistent wind speed with little or no variation in direction. One of these areas is the Arabian Sea, along the coasts of Somalia, Yemen and Oman. The wind climate in the Arabian sea is under the direct influence of the South Asia monsoon, where the wind blows steady from the northeast during the boreal winter, and

  11. Processes controlling forms of phosphorus in surficial sediments from the eastern Arabian Sea impinged by varying bottom water oxygenation conditions

    NASA Astrophysics Data System (ADS)

    Babu, C. Prakash; Nath, B. Nagender

    2005-07-01

    The surficial sediments from the upper continental slope of the eastern Arabian Sea, impinged by the oxygen minimum zone (OMZ, 150-1200 m water depth), show varying concentrations of the biogenic element phosphorus (P, 0.1-0.2%) in the northern and southern areas even though total organic carbon concentrations are relatively constant (TOC, 2-5%; Prakash Babu et al., 1999). To understand this discordance, 17 surface sediment samples from shelf, slope and deep sea of the eastern Arabian Sea were investigated using a five-step sequential extraction scheme to delineate the process responsible for P enrichment in OMZ. High fractions of organic phosphorus (P org 10-26%), biogenic phosphorus (P bio 36-48%), relatively low molar C org/P org ratios (322-447), and C org/P reactive ratios close to Redfield Ratio in OMZ sediments of the SE Arabian Sea suggest accumulation under high surface production and low residence time of labile forms of P due to high sedimentation rates. Despite higher productivity in surface waters, low fractions of P org (8-13%; less than deep-sea sediments of the study area 12-13%), P bio (25-33%), relatively high molar C org/P org ratios (341-508), and C org/P reactive ratios less than Redfield Ratio in OMZ sediments from the NE Arabian Sea may indicate a higher degree of regeneration and diagenetic transformation of labile forms of P to other phases. Authigenic phosphorus (P aut) fraction varies by a factor of 2-8 in sediments from the OMZ when compared to well-oxygenated deep-sea sediments of the study area. While the P total remains constant, significant P transformation seems to occur in NE Arabian Sea, which is suggested by high P aut fraction (˜50%) compared to low P aut fraction (10-39%) in the SE Arabian Sea sediments. Supply rates of phosphorus, variable rates of P dissolution under varying dissolved oxygen contents in the bottom waters, and early diagenetic transformation of P within the sediments seem to influence P geochemistry in

  12. Arabian Sea cyclone: Structure analysis using satellite data

    NASA Astrophysics Data System (ADS)

    Rafiq, Lubna; Blaschke, Thomas; Tajbar, Sapna

    2015-11-01

    Advances in earth observation technology over the last two decades have resulted in improved forecasting of various hydrometeorological-related disasters. In this study the severe tropical cyclone Gonu (2-7 June, 2007) was investigated using multi-sensor satellite data sets (i.e. AIRS, METEOSAT, MODIS and QSCAT data) to monitor its overall structure, position, intensity, and motion. A high sea surface temperature and warm core anomalies (at 200 hPa and above) with respect to the pressure minima in the central core were found to have influenced the pattern of development of the tropical cyclone. High relative humidity in the middle troposphere was aligned with temperature minima at 850 hPa and 700 hPa; high winds (above 120 knots) and closed pressure contours were observed during the intensification stage. A contour analysis of outgoing longwave radiation (OLR) provided an explanation for the direction of movement of the cyclone. The translational movement and velocities (ground speed) of the tropical cyclone were calculated using the surface pressure of the cyclone's central core. Statistical analyses revealed a strong correlation between the maximum wind speeds within the cyclone and various atmospheric parameters. We conclude with a discussion of the significance of these findings with regard to cyclone forecasting within the framework of early warning and disaster management.

  13. The secondary calcification of Neogloboquadrina pachyderma assemblages in Arabian Sea waters and surface sediments

    NASA Astrophysics Data System (ADS)

    Abdolalipour, Samereh; Schulz, Hartmut; Darling, Kate F.

    2014-05-01

    The planktic foraminifer Neogloboquadrina pachyderma (N. pachyderma (sin); Darling et al., 2006) has been recently considered as a (paleo) climatic index in Arabian Sea waters, where increased abundance correlates to the South West monsoon upwelling. Genetic characterization of living specimens collected in multinets off the Oman margin and in the central Arabian Sea indicate the presence of an new genotype of N. pachyderma (Type VIII) (Darling et al., submitted) in the northwestern Indian Ocean. Ecological investigation on these samples reveals that this new genotype, which is the only one to date found in this region, can tolerate warm water temperatures of up to 28° C. It was also found alive below the photic zone within the prominent oxygen minimum zone (OMZ) of the Arabian Sea. To extend our knowledge and understanding of this N. pachyderma Type VIII genotype, we have focused on a morphological analysis of randomly picked specimens (live and dead) from the multinets collected from 200 m down to 700 m water column and from core top sediments distributed over a wide range of water depths (607-3951 m) off the Oman margin in the Arabian Sea. We here use Scanning Electron Microscopy (SEM) to determine the size, shape variation and test wall structure of the penultimate chamber. High resolution measurements confirm the model of chamber growth in non-spinose bilamellar foraminifera of a three or four-layered test wall. As ontogenetic calcite, we were able to visualize the inner lining, the outer layer and the outermost layer formed during the growth of the ultimate chamber. Some of the specimens also showed a fourth layer, which can be attributed to encrustation, observed in higher-latitude specimens of both hemispheres to result from secondary calcification as a terminal step in ontogenetic maturation. To verify the test wall growth and secondary calcification the measurements of the layers were related to the maximum test diameter of the shell. The measurement

  14. 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.

  15. Characterizing Mineral Dust from the Arabian Coast of the Red Sea

    NASA Astrophysics Data System (ADS)

    Puthan Purakkal, J.; Stenchikov, G. L.; Engelbrecht, J. P.

    2014-12-01

    The Arabian Peninsula is one of the Earth's major sources of atmospheric dust. Along with profound negative effects on human activity and natural processes in this region, dust is an important nutrient source for the oligothrophic northern Red Sea. From preliminary observations it is estimated that some 18-20 major dust storms per year deposit about 6 Mt of mineral dust into the Red Sea. To better understand the optical properties, health, and ecological impacts of dust, we study the mineralogical, chemical and morphological properties of surface soil samples collected at prevbiously identified potential dust sources along the Arabian coast of the Red Sea. Many of these dust sources lie within a narrow coastal region and because of their proximity to the Red Sea, are important contributors to the dust/nutrient balance, during both dusty and fair weather conditions. Bulk samples were collected from the top 10 mm of soils from three sites along the Arabian coast of the Red Sea. The soil samples were sieved to separate the < 38μm particle fractions for chemical and mineralogical analysis. X-ray diffractometry (XRD) was applied to measure the mineral content of the dust. The chemical composition of individual particles was analyzed using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). From the XRD analysis of the sieved samples from An Masayat (23.3322 N, 38.9481 E), Buthna (23.2960 N, 38.9384 E) and Rabugh pipeline Road (23.292 N, 38.91 E), it was found that the dust was composed largely of hematite, goethite, calcite, dolomite, quartz, chlorite, muscovite, amphibole, epidote and plagioclase. Our results are being compared to, and show similarities to those of Engelbrecht et al. , collected at 15 Middle East sites. Both the mineralogical content and chemical composition of samples bear the signatures of the regional geology. Engelbrecht, J. P., McDonald, E. V., Gillies, J. A., Jayanty, R. K. M., Casuccio, G., and Gertler, A. W., 2009

  16. Response of benthic foraminifera to phytodetritus in the eastern Arabian Sea under low oxygen conditions

    NASA Astrophysics Data System (ADS)

    Enge, Annekatrin; Wukovits, Julia; Wanek, Wolfgang; Watzka, Margarete; Witte, Ursula; Hunter, William; Heinz, Petra

    2016-04-01

    At water depths between 100 and 1500 m a permanent Oxygen Minimum Zone (OMZ) impinges on the sea floor in the eastern Arabian Sea, exposing benthic organisms to anoxic to suboxic conditions. The flux of organic matter to the sea floor is relatively high at these depths but displays seasonal variation. Deposition of relatively fresh phytodetrital material (phytoplankton remains) can occur within a short period of time after monsoon periods. Several organism groups including foraminifera are involved to different extent in the processing of phytodetritus in the OMZs of the northern Arabian Sea. A series of in situ feeding experiments were performed to study the short-term processing (< 11 days) of organic carbon, nitrogen and nutritional demands of foraminifera at different oxygen concentrations on the continental margin in the eastern Arabian Sea. For the experiments, a single pulse of isotopically labeled phytodetritus was added to the sediment along a depth transect (540-1100 m) on the Indian Margin, covering the OMZ core and the lower OMZ boundary region. Uptake of phytodetritus within 4 days shows the relevance of phytodetritus as food source for foraminifera. Lower content of phytodetrital carbon recorded in foraminifera from more oxygenated depths shows greater food uptake by foraminifera in the OMZ core than in the OMZ boundary region. The foraminiferal assemblage living under almost anoxic conditions in the OMZ core is dominated by species typically found in eutroph environments (such as Uvigerinids) that are adapted to high flux of organic matter. The elevated carbon uptake can also result from missing food competition by macrofauna or from greater energy demand in foraminifera to sustain metabolic processes under hypoxic stress. Variable levels and ratios of phytodetrital carbon and nitrogen indicate specific nutritional demands and storage of food-derived nitrogen in some foraminifera species under near anoxia where the mean phytodetrital nitrogen content

  17. Dtection of Sea Level Rise within the Arabian Gulf Using Space Based GNSS Measurements and Insitu Tide Gauge data

    NASA Astrophysics Data System (ADS)

    Alothman, Abdulaziz; Ayhan, Mehmet

    In the 21st century, sea level rise is expected to be about 30 cm or even more (up to 60 cm). Saudi Arabia has very long coasts of about 3400 km and hundreds of islands. Therefore, sea level monitoring may be important in particular along coastal low lands on Red Sea and Arabian Gulf coasts. Arabian Gulf is connected to Indian Ocean and lying along a parallel course in the south-west of the Zagros Trust Belt. We expect vertical land motion within the area due to both tectonic structures of the Arabian Peninsula and oil production activities. Global Navigation Satellite System (GNSS) Continues observations were used to estimate the vertical crustal motion. Bahrain International GPS Service (IGS-GPS) station is the only continuous GPS station accessible in the region, and it is close to the Mina Sulman tide gauge station in Bahrain. The weekly GPS time series of vertical component at Bahrain IGS-GPS station referring to the ITRF97 from 1999.2 to 2008.6 are used in the computation. We fitted a linear trend with an annual signal and a break to the GPS vertical time series and found a vertical land motion rate of 0.46 0.11 mm/yr. To investigate sea level variation within the west of Arabian Gulf, monthly means of sea level at 13 tide gauges along the coast of Saudi Arabia and Bahrain, available in the database of the Permanent Service for Mean Sea Level (PSMSL), are studied. We analyzed separately the monthly mean sea level measurements at each station, and estimated secular sea level rate by a robust linear trend fitting. We computed the average relative sea level rise rate of 1.96 0.21 mm/yr within the west of Arabian Gulf based on 4 stations spanning longer than 19 years. Sea level rates at the stations are first corrected for vertical land motion contamination using the ICE-5G v1.2 VM4 Glacial Isostatic Adjustment (GIA) model, and the average sea level rate is found 2.27 0.21 mm/yr. Assuming the vertical rate at Bahrain IGS-GPS station represents the vertical rate

  18. Homogeneity of coral reef communities across 8 degrees of latitude in the Saudi Arabian Red Sea.

    PubMed

    Roberts, May B; Jones, Geoffrey P; McCormick, Mark I; Munday, Philip L; Neale, Stephen; Thorrold, Simon; Robitzch, Vanessa S N; Berumen, Michael L

    2016-04-30

    Coral reef communities between 26.8 °N and 18.6 °N latitude in the Saudi Arabian Red Sea were surveyed to provide baseline data and an assessment of fine-scale biogeography of communities in this region. Forty reefs along 1100 km of coastline were surveyed using depth-stratified visual transects of fish and benthic communities. Fish abundance and benthic cover data were analyzed using multivariate approaches to investigate whether coral reef communities differed with latitude. A total of 215 fish species and 90 benthic categories were recorded on the surveys. There were no significant differences among locations in fish abundance, species richness, or among several diversity indices. Despite known environmental gradients within the Red Sea, the communities remained surprisingly similar. The communities do, however, exhibit subtle changes across this span of reefs that likely reflect the constrained distributions of several species of reef fish and benthic fauna. PMID:26608504

  19. Challenges in modelling spatiotemporally varying phytoplankton blooms in the Northwestern Arabian Sea and Gulf of Oman

    NASA Astrophysics Data System (ADS)

    Sedigh Marvasti, S.; Gnanadesikan, A.; Bidokhti, A. A.; Dunne, J. P.; Ghader, S.

    2015-07-01

    We examine interannual variability of phytoplankton blooms in northwestern Arabian Sea and Gulf of Oman. Satellite data (SeaWIFS ocean color) shows two climatological blooms in this region, a wintertime bloom peaking in February and a summertime bloom peaking in September. A pronounced anti-correlation between the AVISO sea surface height anomaly (SSHA) and chlorophyll is found during the wintertime bloom. On a regional scale, interannual variability of the wintertime bloom is thus dominated by cyclonic eddies which vary in location from one year to another. These results were compared against the outputs from three different 3-D Earth System models. We show that two coarse (1°) models with the relatively complex biogeochemistry (TOPAZ) capture the annual cycle but neither eddies nor the interannual variability. An eddy-resolving model (GFDL CM2.6) with a simpler biogeochemistry (miniBLING) displays larger interannual variability, but overestimates the wintertime bloom and captures eddy-bloom coupling in the south but not in the north. The southern part of the domain is a region with a much sharper thermocline and nutricline relatively close to the surface, in which eddies modulate diffusive nutrient supply to the surface (a mechanism not previously emphasized in the literature). We suggest that for the model to simulate the observed wintertime blooms within cyclones, it will be necessary to represent this relatively unusual nutrient structure as well as the cyclonic eddies. This is a challenge in the Northern Arabian Sea as it requires capturing the details of the outflow from the Persian Gulf.

  20. Evidence for eddy formation in the eastern Arabian Sea during the northeast monsoon

    NASA Technical Reports Server (NTRS)

    Bruce, John G.; Johnson, Donald R.; Kindle, John C.

    1994-01-01

    The seasonal formation of a large (500-800 km diameter) anticyclonic eddy in the upper 300-400 m of the eastern Arabian Sea during the northest monsoon period (December-April) is indicated fom hydrographic and satellite altimetry sea level observations, as well as from numerical model experiments. The center of the eddy circulation is approximately 10 deg N, 70 deg E, just to the west of the north-south Laccadive Island chain. In this paper the eddy is called the Laccadive High (LH). In some ways it is like a mirrorlike counterpart to the Great Whirl that develops during the southwest monsoon of the Somali coast (western Arabian Sea). The LH occurs at the same latitude but on the opposite side of the basin during the reversed monsoon. It is different from the Great Whirl, however, in its formation process, its intensity, and its decay. The hydrographic data obtained from surveys all during a single season give sufficiently close station spacing to allow reasonable contouring of the geopotential surfaces and of the properties within and around the LH region with minimum time aliasing. The Geostat altimeter record extends over 4 years, during which the seasonal variability of the LH indicates a dynamic relief of approximately 15-20 cm, which is in good agreement with the hydrographics observations. The altimetry time series also suggests a westward translation of the LH by January with a subsequent dissipation in midbasin. The model used is a wind-forced three-layer primitive equation model which depicts a LH agreement with the timing, position, and amplitude of both the hydrographic and altimetric measurements. The numerical simulation includes a passive tracer located in the Western Bay of Bengal; the western advection of the tracer around the south coasts of Sri Lanka and India in December and January is consistent with the appearance of low-salinity water observed to extend into the Arabian Sea during this period. The modeling studies suggest that both local and

  1. Deep-sea benthic foraminiferal species diversity in the NE Atlantic and NW Arabian sea: a synthesis

    NASA Astrophysics Data System (ADS)

    Gooday, Andrew J.; Bett, Brian J.; Shires, Rizpah; Lambshead, P. John D.

    1998-01-01

    We present a synthesis of species diversity data (Fishers' alpha index, Shannon-Wiener (log 2), ES(100), Rank 1 Dominance) for "live" (stained) foraminifera from five bathyal (1340 m depth) and abyssal (4450-4950 m depth) sites in the NE Atlantic and a 3400 m-deep site in the Arabian Sea. Three Atlantic sites (Porcupine Seabight, BIOTRANS, Porcupine Abyssal Plain) are subject to seasonal phytodetritus inputs that support low diversity populations (8-17 species). In other respects the foraminifera are highly diverse. The meiofaunal fractions (>45 or >63 μm; including fragmented and phytodetritus species) of abyssal Atlantic samples yielded >110 and >170 species in the 0-1 cm and 0-10 cm layers, respectively; the Arabian Sea sample (0-1 cm layer only) yielded 232 species. In both cases, values for diversity measures were very high. Diversity was rather lower in bathyal Porcupine Seabight samples (0-1 cm layer), which yielded <100 species. The foraminiferal macrofauna (>500 μm; Porcupine and Madeira Abyssal Plains) was also speciose (113-133 species), but diversity measures were lower and dominance higher than for the meiofauna. All assemblages contained numerous undescribed species, many belonging to poorly known monothalamous, soft-bodied taxa. Sample diversity was influenced by several factors. Combining phytodetrital and sediment populations reduced diversity and increased dominance slightly; the inclusion of deeper sediment layers and finer sieve fractions had the opposite effect. The inclusion of fragments had more impact on macrofaunal than on meiofaunal diversity, although in both cases the effect was inconsistent (either positive or negative). Porcupine and Madeira Abyssal Plain multicore samples (>63 μm fraction) contained substantially more foraminiferal species than nematode species; the numbers of foraminiferal species in boxcore samples (>500 μm fraction) were comparable to, or greater than, literature values for macrofaunal taxa such as polychaetes

  2. Sea-level responses to erosion and deposition of sediment in the Indus River basin and the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Ferrier, Ken L.; Mitrovica, Jerry X.; Giosan, Liviu; Clift, Peter D.

    2015-04-01

    Changes in sea level are of wide interest because they shape the sedimentary geologic record, modulate flood-related hazards, and reflect Earth's climate. One driver of sea-level change is the erosion and deposition of sediment, which induces changes in sea level by perturbing Earth's crust, gravity field, and rotation axis. Here we use a gravitationally self-consistent global model to explore how sediment erosion and deposition affected sea level during the most recent glacial-interglacial cycle in the northeastern Arabian Sea and the Indus River basin, where fluvial sediment fluxes are among the highest on Earth. We drive the model with a widely used reconstruction of ice mass variations over the last glacial cycle and a sediment loading history that we constructed from published erosion and deposition rate measurements. Our modeling suggests that sediment fluxes from the Indus River are large enough to produce meter-scale changes in sea level near the Indus delta in as little as a few thousand years. These sea-level perturbations are largest closest to the center of the Indus delta, and they grow larger over time as sediment deposition increases. This implies that the elevation of sea-level markers near the Indus delta will be significantly altered by sediment transfer over millennial timescales, and that such deformation should be accounted for in studies that use paleo-sea-level markers to infer past ice sheet volume or explore local processes such as sediment compaction. Our analysis highlights the role that massive fluvial sediment fluxes play in driving sea-level changes over >1000-yr timescales from the Indus River, and, by implication, from other rivers with large sediment fluxes.

  3. 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.

  4. Observations of barrier layer in southeastern Arabian Sea using Argo observations

    NASA Astrophysics Data System (ADS)

    Sharma, Rashmi; Agarwal, Neeraj; Sarkar, Abhijit

    2006-12-01

    We present in this work composite relationships among Barrier Layer (BL) depth, and various other parameters either directly responsible for its formation or the sequence of events which follow once it is formed. Underlying mechanisms responsible for the development of the BL depth, its sustenance and annihilation are examined in the southeastern Arabian Sea (SEAS) in the north Indian Ocean using primarily ARGO floats observations along with ancillary data from various satellites and surface currents from ocean model. All the available Argo floats observations of temperature and salinity as of December 2005 have been analyzed to evaluate the seasonal characteristics of barrier layer (BL) in this warm pool region of Arabian Sea. The annual average BL thickness in this region varies from 20 to 70 m, with larger values towards coast. The standard deviation is also high (15-30 m) in this region showing a strong seasonal variation. In a complete seasonal characteristic studied with the use of observations, BL thickness shows a primary peak (~ 50 m) in January and a secondary peak in September (~ 35 m). While the former is remotely forced, the later owes its generation to the local forcing via precipitation. TMI observations show a lag of 3 months in the SST warming with respect to the maximum BL thickness observed during January. Peak warming in SST during April immediately follows by rise in integrated water vapour. Interestingly, following the secondary maxima of BL, SST does not show any warming signature, possibly due to the overcast condition, preventing the surface from heating up.

  5. Interannual variability of the Arabian Sea Warm Pool: observations and governing mechanisms

    NASA Astrophysics Data System (ADS)

    Rao, R. R.; Jitendra, V.; GirishKumar, M. S.; Ravichandran, M.; Ramakrishna, S. S. V. S.

    2015-04-01

    The near-surface layers in the Arabian Sea progressively warm up from February to early May resulting in the formation of pool of warm waters popularly known as the Arabian Sea Warm Pool (ASWP). The availability of high quality TMI sea surface temperature (SST) data for the years 1998-2010 is exploited to describe the evolution of the ASWP on seasonal and interannual time scales and to explain the associated mechanisms. The multi-year (1998-2010) averaged TMI SSTs during April-May show peak values of the ASWP in excess of 30 °C with its core >30.5 °C extending offshore as a well-marked southwestward tongue stretching from the southwest coast of India. The ASWP shows both seasonal and interannual variability in the evolution of spatio-temporal characteristics such as amplitude, phase and spatial extent. Among these 13 years, the ASWP was most (least) pronounced during 1998, 2003 and 2010 (1999, 2000, 2001 and 2008). The mechanisms that govern the observed interannual variability of the ASWP are examined addressing the most relevant issues such as—(1) dynamic pre-conditioning: background pycnocline topography influenced by the westward propagating Rossby waves during October-May, (2) thermal pre-conditioning: background SST/heat content signal during October-January influenced by the strength of the preceding year's summer monsoon and the post-monsoon cyclones during October-December, (3) haline pre-conditioning: near-surface vertical salinity stratification during November-February influenced by the advection of low saline waters from the Bay of Bengal, (4) influence of surface net heat flux forcing during February-May, and (5) influence of El Nino/La Nina.

  6. Challenges in modeling spatiotemporally varying phytoplankton blooms in the Northwestern Arabian Sea and Gulf of Oman

    NASA Astrophysics Data System (ADS)

    Sedigh Marvasti, S.; Gnanadesikan, A.; Bidokhti, A. A.; Dunne, J. P.; Ghader, S.

    2016-02-01

    Recent years have shown an increase in harmful algal blooms in the Northwest Arabian Sea and Gulf of Oman, raising the question of whether climate change will accelerate this trend. This has led us to examine whether the Earth System Models used to simulate phytoplankton productivity accurately capture bloom dynamics in this region - both in terms of the annual cycle and interannual variability. Satellite data (SeaWIFS ocean color) show two climatological blooms in this region, a wintertime bloom peaking in February and a summertime bloom peaking in September. On a regional scale, interannual variability of the wintertime bloom is dominated by cyclonic eddies which vary in location from one year to another. Two coarse (1°) models with the relatively complex biogeochemistry (TOPAZ) capture the annual cycle but neither eddies nor the interannual variability. An eddy-resolving model (GFDL CM2.6) with a simpler biogeochemistry (miniBLING) displays larger interannual variability, but overestimates the wintertime bloom and captures eddy-bloom coupling in the south but not in the north. The models fail to capture both the magnitude of the wintertime bloom and its modulation by eddies in part because of their failure to capture the observed sharp thermocline and/or nutricline in this region. When CM2.6 is able to capture such features in the Southern part of the basin, eddies modulate diffusive nutrient supply to the surface (a mechanism not previously emphasized in the literature). For the model to simulate the observed wintertime blooms within cyclones, it will be necessary to represent this relatively unusual nutrient structure as well as the cyclonic eddies. This is a challenge in the Northern Arabian Sea as it requires capturing the details of the outflow from the Persian Gulf - something that is poorly done in global models.

  7. Scavenger assemblages under differing trophic conditions: a case study in the deep Arabian Sea

    NASA Astrophysics Data System (ADS)

    Janßen, Felix; Treude, Tina; Witte, Ursula

    Baited cameras and traps were deployed at four stations in the deep Arabian Sea to investigate the composition of the necrophagous fauna and to evaluate whether regional differences in trophic conditions are reflected by differing scavenger assemblages. The ophidiid fish Barathrites iris, the large lysianassoid amphipod Eurythenes gryllus, the aristeid prawn Plesiopenaeus armatus, and zoarcid fishes of the genus Pachycara were abundant at the bait at all stations. The ophidiid Holcomycteronus aequatorius, the liparid fish Paraliparis sp., and galatheid crabs of the genus Munidopsis occurred in considerable numbers at single sites. Trap catches further contained lysianassoid amphipods of the genera Paralicella, Abyssorchomene and Paracallisoma. In contrast to scavenger assemblages of the Atlantic and Pacific Ocean, macrourid fishes were virtually absent at the bait. E. gryllus and B. iris consumed the main proportion of the bait, while consumption was at most moderate in all other taxa. Feeding strategies of the respective taxa are inferred from their behavior at the bait and discussed with regard to the profit that can be drawn from food falls. Differences between stations were pronounced with respect to species dominating bait consumption. E. gryllus appeared in highest numbers at the bait in the productive northern and central Arabian Sea where a relatively high availability of food items is expected to sustain high population densities. High numbers of B. iris in the least productive southern part indicate their ability to persist under food-poor conditions and may correspond to a high dependency on food falls. E. gryllus and B. iris both occurred in smaller numbers in the particularly productive western Arabian Sea. This may reflect a reduced dependency on food falls, due to an access to alternative food sources, rather than small population densities. Smaller numbers of E. gryllus and B. iris resulted in slower bait consumption and gave Pachycara spp. the

  8. Arabian Sea

    Atmospheric Science Data Center

    2013-04-16

    ... of the images. The image set is centered along the Tropic of Cancer, about 400 kilometers east of Muscat, Oman, and was acquired on October ... MD. The MISR data were obtained from the NASA Langley Research Center Atmospheric Science Data Center in Hampton, VA. Image ...

  9. Variations in productivity and eolian fluxes in the northeastern Arabian Sea during the past 110 ka

    NASA Astrophysics Data System (ADS)

    Pourmand, Ali; Marcantonio, Franco; Schulz, Hartmut

    2004-04-01

    High-resolution (one to two samples/ka) radionuclide proxy records from core 93KL in the northeastern Arabian Sea provide evidence for millennial climate variability over the past 110 ka. We interpret 230Th-normalized 232Th fluxes as a proxy for eolian input, and authigenic uranium concentrations as a proxy for past productivity. We attribute orbital and suborbital variations in both proxies to changes in the intensity of the southwest Indian Ocean monsoon. The highest 230Th-normalized 232Th fluxes occur at times that are consistent with the timing of the Younger Dryas, Heinrich events 1-7 and cold Dansgaard-Oeschger stadial events recorded in the GISP2 ice core. Such high dust fluxes may be due to a weakened southwest monsoon in conjunction with strengthened northwesterlies from the Arabian Peninsula and Mesopotamia. Authigenic uranium concentrations, on the other hand, are highest during warm Dansgaard-Oeschger interstadials when the southwest monsoon is intensified relative to the northwesterly winds. Our results also indicate that on orbital timescales maximum average eolian fluxes coincide with the timing of marine isotopic stage (MIS) 2 and 4, while minimum fluxes occur during MIS 1, 3 and 5. Although the forcing mechanism(s) controlling suborbital variabilities in monsoonal intensity is still debated, our findings suggest an atmospheric teleconnection between the low-latitude southwest monsoon and North Atlantic climate.

  10. Bio-Optical Properties of the Arabian Sea as Determined by In Situ and Sea WiFS Data

    NASA Technical Reports Server (NTRS)

    Trees, Charles C.

    1997-01-01

    The overall objective of this work was to characterize optical and fluorescence properties in the euphotic zone during two British Ocean Flux Study (BOFS) Arabian Sea cruises. This was later expanded in 1995 to include three U.S. JGOFS Arabian Sea Cruises. The region was to be divided into one or more "bio-optical provinces," within each of which a single set of regression models was to be developed to relate the vertical distribution of irradiance attenuation and normalized fluorescence (SF and NF) to remote sensing reflectance and diffuse attenuation coefficient. The working hypothesis was that over relatively large spatial and temporal scales, the vertical profiles of bio-optical properties were predictable. The specific technical objectives were: (1) To characterize the vertical distribution of the inherent and apparent optical properties by measuring downwelling and upwelling irradiances, upwelling radiances, scalar irradiance of PAR, and beam transmissions at each station - from these data, spectral diffuse attenuation coefficients, irradiance reflectances, remote sensing reflectances, surface-leaving radiances and beam attenuation coefficients were determined; (2) To characterize the spectral absorption of total particulate, detrital, and dissolved organic material at each station from discrete water samples; (3) To describe the vertical distribution of photoadaptive properties in the water column by measuring profiles of stimulated (SF) and natural (NF) fluorescence and examining relationships between SF and NF as a function of diffuse optical depth, pigment biomass and primary productivity; and (4) To establish locally derived, in-water algorithms relating remote sensing reflectance spectra to diffuse attenuation coefficients, phytoplankton pigment concentrations and primary productivity, through intercomparisons with in situ measurements, for application to SeaWiFS data.

  11. Late Holocene SST and primary productivity variations in the northeastern Arabian Sea as a recorder for winter monsoon variability

    NASA Astrophysics Data System (ADS)

    Böll, Anna; Gaye, Birgit; Lückge, Andreas

    2014-05-01

    Variability in the oceanic environment of the Arabian Sea region is strongly influenced by the seasonal monsoon cycle of alternating wind directions. Strong south-westerly winds during the summer monsoon induce upwelling of nutrient rich waters along the coast off Somalia, Oman and southwest India, which result in high rates of primary production. In the northeastern Arabian Sea off Pakistan on the other hand, primary production and sea surface temperatures are linked to northeast monsoonal winds that cool the sea surface and drive convective mixing and high surface ocean productivity during the winter season. In this study, we analyzed alkenone-derived sea surface temperature (SST) variations and proxies of primary productivity (organic carbon and δ15N) in a well-laminated sediment core from the Pakistan continental margin to establish the first high-resolution record of winter monsoon variability for the late Holocene. Over the last 2400 years reconstructed SST in the northeastern Arabian Sea decreased whereas productivity increased, imaging a long-term trend of northeast monsoon strengthening in response to insolation-induced southward migration of the Intertropical Convergence Zone. The comparison of our winter monsoon record with records of summer monsoon intensity suggests that summer and winter monsoon strength was essentially anti-correlated over the late Holocene throughout the Asian monsoon system. In addition, SST variations recorded off Pakistan match very well with Northern Hemisphere temperature records supporting the growing body of evidence that Asian climate is linked to Northern Hemisphere climate change. It reveals a consistent pattern of increased summer monsoon activity in the northeastern Arabian Sea during northern hemispheric warm periods (Medieval Warm Period, Roman Warm Period) and strengthened winter monsoon activity during hemispheric colder periods (Little Ice Age).

  12. Massive outbreaks of Noctiluca scintillans blooms in the Arabian Sea due to spread of hypoxia.

    PubMed

    do Rosário Gomes, Helga; Goes, Joaquim I; Matondkar, S G P; Buskey, Edward J; Basu, Subhajit; Parab, Sushma; Thoppil, Prasad

    2014-01-01

    In the last decade, the northern Arabian Sea has witnessed a radical shift in the composition of winter phytoplankton blooms, which previously comprised mainly of diatoms, the unicellular, siliceous photosynthetic organisms favoured by nutrient-enriched waters from convective mixing. These trophically important diatom blooms have been replaced by widespread blooms of a large, green dinoflagellate, Noctiluca scintillans, which combines carbon fixation from its chlorophyll-containing endosymbiont with ingestion of prey. Here, we report that these massive outbreaks of N. scintillans during winter are being facilitated by an unprecedented influx of oxygen deficient waters into the euphotic zone and by the extraordinary ability of its endosymbiont Pedinomonas noctilucae to fix carbon more efficiently than other phytoplankton under hypoxic conditions. We contend that N. scintillans blooms could disrupt the traditional diatom-sustained food chain to the detriment of regional fisheries and long-term health of an ecosystem supporting a coastal population of nearly 120 million people. PMID:25203785

  13. Weight dependence of arsenic concentration in the Arabian Sea tuna fish

    SciTech Connect

    Ashraf, M.; Jaffar, M.

    1988-02-01

    The objective of the present investigation was to estimate the arsenic concentration in the edible muscle of Thunnus thynnus and Thunnus toggel (hereafter called tuna and longtail tune) as they have great commercial value. These fish are widely available along the coastal line of Pakistan and are consumed abundantly in large bulk. Thus, it was felt justifiable on the basis of safety of human health that data, in the first instance, be obtained on arsenic concentration in tuna as a function of weight to check whether the metal distribution was species-specific or it depended on individual mode of development. The data, the first of the kind so far presented on the Arabian Sea tuna, would thus provide the required baseline quantitative information needed in future studies on the physiological processes regulating the distribution and uptake of arsenic by these and other species of fish common to the region.

  14. Winter monsoon circulation of the northern Arabian Sea and Somali Current

    NASA Astrophysics Data System (ADS)

    Schott, Friedrich A.; Fischer, Jürgen

    2000-03-01

    The winter monsoon circulation in the northern inflow region of the Somali Current is discussed on the basis of an array of moored acoustic Doppler current profiler and current meter stations deployed during 1995-1996 and a ship survey carried out in January 1998. It is found that the westward inflow into the Somali Current regime occurs essentially south of 11°N and that this inflow bifurcates at the Somali coast, with the southward branch supplying the equatorward Somali Current and the northward one returning into the northwestern Arabian Sea. This northward branch partially supplies a shallow outflow through the Socotra Passage between the African continent and the banks of Socotra and partially feeds into eastward recirculation directly along the southern slopes of Socotra. Underneath this shallow surface flow, southwestward undercurrent flows are observed. Undercurrent inflow from the Gulf of Aden through the Socotra Passage occurs between 100 and 1000 m, with its current core at 700-800 m, and is clearly marked by the Red Sea Water (RSW) salinity maximum. The observations suggest that the maximum RSW inflow out of the Gulf of Aden occurs during the winter monsoon season and uses the Socotra Passage as its main route into the Indian Ocean. Westward undercurrent inflow into the Somali Current regime is also observed south of Socotra, but this flow lacks the RSW salinity maximum. Off the Arabian peninsula, eastward boundary flow is observed in the upper 800 m with a compensating westward flow to the south. The observed circulation pattern is qualitatively compared with recent high-resolution numerical model studies and is found to be in basic agreement.

  15. Seasonal response of zooplankton to monsoonal reversals in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Smith, Sharon; Roman, Michael; Prusova, Irina; Wishner, Karen; Gowing, Marcia; Codispoti, L. A.; Barber, Richard; Marra, John; Flagg, Charles

    The US JGOFS Arabian Sea Process Study was designed to provide a seasonally and spatially resolved carbon budget for a basin exhibiting some of the highest and lowest concentrations of plant biomass in the world's ocean. During the US JGOFS Process Study in the Arabian Sea (September 1994-January 1996), the absolute maximum in biomass of epipelagic zooplankton in the entire study was observed during the Southwest Monsoon season inshore of the Findlater Jet in the area of upwelling. The greatest contrast between high and low biomass in the study area also was observed during the Southwest Monsoon, as was the strongest onshore-offshore gradient in biomass. Lowest biomass throughout the study was observed at the most offshore station (S15), outside the direct influence of the monsoon forcing. The greatest day/night contrasts in biomass were observed nearshore in all seasons, with nighttime biomass exceeding daytime in the Northeast Monsoon season, but daytime exceeding nighttime in the Southwest Monsoon season. The diel vertical migration patterns in general reversed between the monsoons at all stations in the southern part of the study area. Virtually, no diel vertical migration of zooplankton took place in any season at the station with strong, persistent subsurface suboxic conditions (N7), suggesting that these conditions suppress migration. Based on the distribution of biomass, we hypothesize that inshore of the Findlater Jet, zooplankton grazing on phytoplankton is the dominant pathway of carbon transformation during both monsoon seasons, whereas offshore the zooplankton feed primarily on microplankton or are carnivorous, conditions that result in reduction of the carbon flux mediated by the zooplankton. Predation by mesopelagic fish, primarily myctophids, may equal daily growth of zooplankton inshore of the Findlater Jet during all seasons. This suggests that the food web inshore of the Findlater Jet is well integrated, may have evolved during past periods of

  16. Large organic-walled Protista ( Gromia) in the Arabian Sea: Density, diversity, distribution and ecology

    NASA Astrophysics Data System (ADS)

    Aranda da Silva, A.; Gooday, A. J.

    2009-03-01

    The genus Gromia includes large marine protists ('gromiids') with filose pseudopodia and sack-like organic tests. The first deep-water species were discovered in the 1990s on the Oman Margin of the Arabian Sea and subsequently found on the Pakistan Margin. We present a survey of gromiids in samples collected off Oman in 2002 and off Pakistan in 2003. In addition to the two species ( Gromia sphaerica and Gromia pyriformis) already described from this area, at least eight undescribed gromiid species were present. Sausage shaped, grape shaped and spherical morphotypes were represented among this material. On the Oman Margin, gromiids occurred in densities up to several thousand individuals m -2 at 1400 and 1700 m but were much less common at 1100 and 2000 m. Apart from G. pyriformis, which was fairly common (several hundred individuals m -2) at 1000 m, gromiids were uncommon in core samples taken off Pakistan, with 11 indiv. m -2 at 1200 m and 19 indiv. m -2 at 1850 m. On both margins, these protists occurred at depths >1000 m where bottom-water oxygen concentrations exceeded ˜0.2 ml l -1 (=8.92 μM l -1) land sediments were fully bioturbated and oxidised. However, they were not observed at similar oxygen levels above the OMZ. Most gromiids lived on the sediment surface with their apertures facing down and their pseudopodia presumably deployed into the sediment to feed on surficial material and associated bacteria. We conclude that these large protists may play an important ecological role in the bathyal Arabian Sea, particularly in carbon cycling but also in structuring the surficial sediments. In addition, their tests, particularly those of G. sphaerica, provide substrates for attached Foraminifera.

  17. MODIS-Aqua detects Noctiluca scintillans and hotspots in the central Arabian Sea.

    PubMed

    Dwivedi, R; Priyaja, P; Rafeeq, M; Sudhakar, M

    2016-01-01

    Northern Arabian Sea is considered as an ecologically sensitive area as it experiences a massive upwelling and long-lasting algal bloom, Noctiluca scintillans (green tide) during summer and spring-winter, respectively. Diatom bloom is also found to be co-located with N. scintillans and both have an impact on ecology of the basin. In-house technique of detecting species of these blooms from Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua data was used to generate a time-series of images revealing their spatial distribution. A study of spatial-temporal variability of these blooms using satellite data expressed a cyclic pattern of their spread over a period of 13 years. An average distribution of the blooms for January-March period revealed a peak in 2015 and minimum in 2013. Subsequently, a time-series of phytoplankton species images were generated for these 2 years to study their inter-annual variability and the associated factors. Species images during active phase of the bloom (February) in 2015 indicated development of N. scintillans and diatom in the central Arabian Sea also, up to 12° N. This observation was substantiated with relevant oceanic parameters measured from the ship as well as satellite data and the same is highlight of the paper. While oxygen depletion and release of ammonia associated with N. scintillans are detrimental for waters on the western side; it is relatively less extreme and supports the entire food chain on the eastern side. In view of these contrasting eco-sensitive events, it is a matter of concern to identify biologically active persistent areas, hot spots, in order to study their ecology in detail. An ecological index, persistence of the bloom, was derived from the time-series of species images and it is another highlight of our study. PMID:26690080

  18. Is the trend in chlorophyll-a in the Arabian Sea decreasing?

    NASA Astrophysics Data System (ADS)

    Prakash, Prince; Prakash, Satya; Rahaman, Hasibur; Ravichandran, M.; Nayak, Shailesh

    2012-12-01

    Recent studies of satellite-derived Chlorophyll concentrations (Chl-a) in the western Arabian Sea (AS) have suggested an increasing temporal trend, but the length of the records used have typically been too short to resolve longer-term trends, if any. Our analysis of a long term satellite ocean color data shows a change of trend in the summer chlorophyll for the western AS before and after 2003; Chl-a concentration was indeed increasing till 2003, but appears to be declining since then, indicating a secular multi-year trend in Chl-a variability. However, this trend is not uniform over the entire region. Analysis of wind, sea surface temperature (SST), Sea Level Anomaly (SLA) and thermocline depth, suggests that the declining summer monsoon chlorophyll-a (Chl-a) concentration may be due to increasing SLA in this region. The earlier observed biological changes in the western AS could be an artifact of the change in local winds and ocean dynamics, which may be a part of the natural long-term variability.

  19. Relationship between coccolith Sr/Ca ratios and coccolithophore production and export in the Arabian Sea and Sargasso Sea

    NASA Astrophysics Data System (ADS)

    Stoll, Heather M.; Ziveri, Patrizia; Shimizu, Nobumichi; Conte, Maureen; Theroux, Susanna

    2007-03-01

    Coccolithophore CaCO 3 production can account for 20-80% of biogenic carbonate exported from the photic zone, and coccoliths are a dominant biogenic carbonate in many deep-sea sediments. A new method for picking individual coccoliths from sediment traps and sediments for analysis using Secondary Ion Mass Spectrometry (ion probe) allows us to make precise Sr/Ca and Mg/Ca determinations on coccoliths from single species even in samples where material is limited. There are large biological effects in Sr/Ca partitioning in coccoliths that have been related to variations in coccolithophore productivity. In sediment traps from the Sargasso Sea at Bermuda and Arabian Sea in the Somali Basin, we can identify Sr/Ca variations in several species that are consistent with inferred seasonal variations in coccolithophore productivity in surface waters. In the Arabian Sea, coccolith Sr/Ca ratios in Calcidiscus leptoporus and Helicosphaera carteri are lowest during the nonproductive intermonsoon. They are highest during the upwelling of southwest monsoon and during the nutrient entrainment from strong winds of the northeast monsoon. These Sr/Ca variations match seasonal trends in coccolith export flux. Furthermore, Sr/Ca variations in C. leptoporus are larger, and this species also has the greater variation in export flux between southwest monsoon and intermonsoon seasons. At Bermuda, a 1996 fall bloom, driven by passage of a warm mode water eddy, induced a large increase in Sr/Ca of C. leptoporus coincident with an increase of C. leptoporus export. Over an annual series for 2004, highest Sr/Ca ratios of C. leptoporus in the summer months match the typical summer peak in surface standing stock of this species and the stimulation of its productivity by mesoscale cyclonic eddies and eddy-eddy interactions. High Sr/Ca did not coincide with the highest export of C. leptoporus coccoliths, likely because cyclonic eddies, unlike mode-water eddies, are dominated by small phytoplankton

  20. Modeling a Typical Winter-time Dust Event over the Arabian Peninsula and the Red Sea

    SciTech Connect

    Kalenderski, S.; Stenchikov, G.; Zhao, Chun

    2013-02-20

    We used WRF-Chem, a regional meteorological model coupled with an aerosol-chemistry component, to simulate various aspects of the dust phenomena over the Arabian Peninsula and Red Sea during a typical winter-time dust event that occurred in January 2009. The model predicted that the total amount of emitted dust was 18.3 Tg for the entire dust outburst period and that the two maximum daily rates were ~2.4 Tg/day and ~1.5 Tg/day, corresponding to two periods with the highest aerosol optical depth that were well captured by ground- and satellite-based observations. The model predicted that the dust plume was thick, extensive, and mixed in a deep boundary layer at an altitude of 3-4 km. Its spatial distribution was modeled to be consistent with typical spatial patterns of dust emissions. We utilized MODIS-Aqua and Solar Village AERONET measurements of the aerosol optical depth (AOD) to evaluate the radiative impact of aerosols. Our results clearly indicated that the presence of dust particles in the atmosphere caused a significant reduction in the amount of solar radiation reaching the surface during the dust event. We also found that dust aerosols have significant impact on the energy and nutrient balances of the Red Sea. Our results showed that the simulated cooling under the dust plume reached 100 W/m2, which could have profound effects on both the sea surface temperature and circulation. Further analysis of dust generation and its spatial and temporal variability is extremely important for future projections and for better understanding of the climate and ecological history of the Red Sea.

  1. Pollutants from the Gulf War serve as water mass tracer in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Plähn, Olaf; Rhein, Monika; Fine, Rana A.; Sullivan, Kevin F.

    In 1995, concentrations of the chlorofluorocarbon compound CFC-12 in the outflow water from the Persian Gulf were 8-40 fold higher than normally caused by air-sea gas exchange. At that time, the anomaly was restricted to the Gulf of Oman north of 20°N, while in 1998 the signal had spread southwestward to 12°N. The sources of this CFC-12 input of about 6400 kg are most likely the fire extinguishers and solvents used during and after the Gulf War in 1991. This CFC-12 signal is a new feature of the Persian Gulf Water (PGW) which can be used to track and quantify the spreading and dilution of PGW in the northern Indian Ocean. The contaminated PGW spreads southward with a mean velocity of 0.02-0.025 m s-1. At 20°N, the anomaly is diluted by a factor of more than two, and east of the island Socotra by a factor of four. A mean transport of less than 0.5·106 m³ s-1 is calculated for PGW assuming a mean dilution rate of 30% from the source signal in the Gulf of Oman to the western Arabian Sea.

  2. Tracing the strength of the southwest monsoon using boron isotopes in the eastern Arabian Sea

    NASA Astrophysics Data System (ADS)

    Naik, Sushant S.; Divakar Naidu, P.; Foster, Gavin L.; Martínez-Botí, Miguel A.

    2015-03-01

    Here we present the first boron isotope-based pCO2sw (pCO2 of seawater) reconstruction from the eastern Arabian Sea using the planktic foraminifera species Globigerinoides ruber. Our results from sediment core AAS9/21 show that pCO2sw varied between ~160 and 300 µatm during the last 23 kyr. The ΔpCO2, the sea-air pCO2 difference, is relatively small during the last glacial maximum and becomes more negative toward the Holocene, with the exception of a significant excess during the last deglaciation centered on the Bølling-Ållerød. Throughout the record, ΔpCO2 is predominantly negative, probably as a result of enhanced biological productivity (and higher nutrient and carbon utilization) during the southwest monsoon. A reduction in ΔpCO2 during the last glacial maximum is therefore consistent with a reduction in the strength of this monsoon system.

  3. Measurements of CO and CH4 in the troposphere over Saudi Arabia, India, and the Arabian Sea during the 1979 International Summer Monsoon Experiment /MONEX/

    NASA Technical Reports Server (NTRS)

    Newell, R. E.; Condon, E. P.; Reichle, H. G., Jr.

    1981-01-01

    During the 1979 Summer MONEX, 150 air samples collected over Saudi Arabia, India, and the Arabian Sea were analyzed for CO and CH4. Near Dhahran and over the Ganges Valley there were high concentrations of CO, around 300 ppbv, in the boundary layer. Out over the Saudi Arabian desert there was no sharp increase in the boundary layer. It is suggested that these high concentrations originate from pollution sources. Low values of CO, down to 80 ppbv, are found over the Arabian Sea as the monsoon progresses, and these may originate from the Southern Hemisphere. Methane over Saudi Arabia (1.59 ppmv) is a little higher than that over the Arabian Sea (1.54 ppmv) probably because the latter region is influenced by air from the Southern Hemisphere.

  4. Modeling of circulation in the Arabian Gulf and the Sea of Oman: Skill assessment and seasonal thermohaline structure

    NASA Astrophysics Data System (ADS)

    Al Azhar, Muchamad; Temimi, Marouane; Zhao, Jun; Ghedira, Hosni

    2016-03-01

    Hindcast simulations of the Arabian Gulf and the Sea of Oman using the Regional Ocean Modeling System (ROMS) are quantitatively evaluated with basin-wide hydrographic data and time series measurements. The model shows comparable skill in reproducing moored observations of current velocities structure in upper and bottom depths. The skill in simulating observed temperature is higher of 0.93 (scale 0-1) in upper depths compared to 0.52 in bottom depths. Model results are sensitive to parameterization of water clarity. A lower sensitivity was noticed to KPP, GLS, and MY2.5 turbulence closures. When coastal turbid water parameterization is used, accuracy of the model in reproducing seasonal and spatial variations of temperature and salinity increased by 25% compared to the clear water case whereas only 10% increase was noticed when applying KPP turbulent closure. The model reproduces well anticlockwise circulation in the Gulf. A stronger surface inflow of fresher water to the Arabian Gulf through the Strait of Hormuz is simulated in summer compared to winter conditions, mainly due to upper layer horizontal gradient of density between the Arabian Gulf and the Sea of Oman. Less seasonal variability of outflow between 0.15 and 0.20 m s-1 at 50 m to bottom depth around the Strait of Hormuz was noticed in the model results. Modeled surface layer stratification is stronger in summer than winter and varies spatially in the Arabian Gulf with highest stratification near the Strait of Hormuz. Overall, the stratification in shallow water area of the Arabian Gulf remains low throughout the year.

  5. Heavy metals in fish from the Red Sea, Arabian Sea, and Indian Ocean: effect of origin, fish species and size and correlation among the metals.

    PubMed

    Obaidat, Mohammad M; Massadeh, Adnan M; Al-Athamneh, Ahmad M; Jaradat, Qasem M

    2015-04-01

    This study determined the levels of As, Cu, Pb, and Cd in fish from Red Sea, Arabian Sea, and Indian Ocean by graphite furnace atomic absorption spectrophotometry. Metal levels were compared with international standards. The levels among fish types and origin, the relationship among metals, and the correlation between the levels and fish size were statistically tested. Fish type and origin significantly affected the levels. None of the fish contained As, Cu, and Pb above the FAO and EU codes. However, Cd exceeded the Jordanian, FAO, and EC codes from the three origins. As and Cd positively correlated with each other in Arabian Sea fish. As and Pb correlated negatively, but Cu and Cd did not correlate with fish size. This study indicates that Cd is common in fish from the three origins regardless the fish size. This warrants continuous monitoring for heavy metals, especially Cd, in internationally traded fish. PMID:25822330

  6. Winter and summer monsoon water mass, heat and freshwater transport changes in the Arabian Sea near 8°N

    NASA Astrophysics Data System (ADS)

    Stramma, Lothar; Brandt, Peter; Schott, Friedrich; Quadfasel, Detlef; Fischer, Jürgen

    The differences in the water mass distributions and transports in the Arabian Sea between the summer monsoon of August 1993 and the winter monsoon of January 1998 are investigated, based on two hydrographic sections along approximately 8°N. At the western end the sections were closed by a northward leg towards the African continent at about 55°E. In the central basin along 8°N the monsoon anomalies of the temperature and density below the surface-mixed layer were dominated by annual Rossby waves propagating westward across the Arabian Sea. In the northwestern part of the basin the annual Rossby waves have much smaller impact, and the density anomalies observed there were mostly associated with the Socotra Gyre. Salinity and oxygen differences along the section reflect local processes such as the spreading of water masses originating in the Bay of Bengal, northward transport of Indian Central Water, or slightly stronger southward spreading of Red Sea Water in August than in January. The anomalous wind conditions of 1997/98 influenced only the upper 50-100 m with warmer surface waters in January 1998, and Bay of Bengal Water covered the surface layer of the section in the eastern Arabian Sea. Estimates of the overturning circulation of the Arabian Sea were carried out despite the fact that many uncertainties are involved. For both cruises a vertical overturning cell of about 4-6 Sv was determined, with inflow below 2500 m and outflow between about 300 and 2500 m. In the upper 300-450 m a seasonally reversing shallow meridional overturning cell appears to exist in which the Ekman transport is balanced by a geostrophic transport. The heat flux across 8°N is dominated by the Ekman transport, yielding about -0.6 PW for August 1993, and 0.24 PW for January 1998. These values are comparable to climatological and model derived heat flux estimates. Freshwater fluxes across 8°N also were computed, yielding northward freshwater fluxes of 0.07 Sv in January 1998 and 0

  7. Annual biomarker record for export production in the central Arabian Sea

    NASA Astrophysics Data System (ADS)

    Prahl, Fredrick G.; Dymond, Jack; Sparrow, Margaret A.

    The record for plankton biomarkers in sediment trap samples from a one-year experiment in the central Arabian Sea (AS4: 15°59'N 61°30'E) shows variations that reflect changing biological conditions in surface waters. Particulate fluxes of C 37-39 alkenones, highly branched C 25 isoprenoids (HBI), dinosterol, nC 28 12-hydroxy fatty acid, 24-ethylcholesterol, and a C 30-34 series of pentacyclic triterpanols all displayed distinct maxima at the start and stop of the Northeast (NE) and Southwest (SW) Monsoons. Surface mixing conditions changed rapidly at these times, altering light and nutrient availability, thereby triggering these biomarker signals of export production. Temporal offsets noted in individual biomarker concentrations (per g total organic carbon) at the start of the SW Monsoon suggest succession occurs in the phytoplankton community contributing to organic matter export. Comparable offsets were neither apparent at the start of the less dynamic NE Monsoon nor at the end of the NE or SW Monsoons. Broad concentration maxima for HBI also were observed at the beginning and end of the time-series during the relatively quiescent Fall Intermonsoon period when such features were conspicuously absent for other biomarkers. HBI are reputed biomarkers of Rhizoselenia and Haslea spp., two recognized dominants of diatom biomass in the Arabian Sea. These peaks in biomarker concentration could reflect either changes in the relative proportion of specific organisms that contribute to the upper ocean productivity or enhanced preservation of the biomarkers during times of high export production. In either case, the biomarker record in sediment traps reflects important changes in the biological condition of the upper ocean. All biomarkers except HBI were measurable in surface sediments deposited beneath the trap site. Comparison with concentrations in average sediment trap particles showed each was sensitive to significant (˜99%) degradation, displaying depletion factors

  8. Living (Rose Bengal stained) benthic foraminifera from the Pakistan continental margin (northern Arabian Sea)

    NASA Astrophysics Data System (ADS)

    Jannink, N. T.; Zachariasse, W. J.; Van der Zwaan, G. J.

    1998-09-01

    The Arabian Sea is characterized by one of the world's most pronounced oxygen minimum zones (OMZ) (<0.1 O 2 ml/l), which impinges on the seafloor at 200-1000 m depths. The OMZ in the Arabian Sea results from extremely high surface water productivity and moderate thermocline ventilation. Nine box cores were taken on two parallel down-slope transects covering depths from 500 to 2000 m. From these nine box cores living (Rose Bengal stained) benthic foraminifera were studied in detail. Within the upper part of the OMZ, Bolivina dilatata and Bulimina exilis are the most abundant species. In the lower part of the OMZ, Uvigerina peregrina and B. exilis are the most abundant. Just below the OMZ, at a water depth of about 1250 m, the assemblage is typically dominated by Rotaliatinopsis semiinvoluta and U. peregrina; in still deeper waters (1500-2000 m) Bulimina aculeata and Epistominella exigua are the most prominent species. Transect II was sampled three weeks after transect I; on the average, standing stocks were four times higher in transect II. However, down-slope species distributions are similar in the two transects, both in the 63 μm and the 150 μm size fractions. Also vertical (in-sediment) distributions are remarkably similar. This indicates that standing stock differences between the two transects can be ascribed either to the effect of patchiness or, more likely, to the nature and the amount of organic flux. We found unambiguous evidence that in and below the OMZ many benthic foraminifera persist in suboxic to anoxic microhabitats. This regards surface as well as subsurface habitats. Evidently, oxygen is not a limiting factor for a considerable number of species. The obvious relationship between species distribution and the OMZ might then be explained in terms of preferences for amount or type of organic flux. An alternative explanation involves favourable effects resulting from the absence of larger predators. The various models pertaining to the limiting

  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. The trophic and metabolic pathways of foraminifera in the Arabian Sea: evidence from cellular stable isotopes

    NASA Astrophysics Data System (ADS)

    Jeffreys, R. M.; Fisher, E. H.; Gooday, A. J.; Larkin, K. E.; Billett, D. S. M.; Wolff, G. A.

    2015-03-01

    The Arabian Sea is a region of elevated productivity with the highest globally recorded fluxes of particulate organic matter (POM) to the deep ocean, providing an abundant food source for fauna at the seafloor. However, benthic communities are also strongly influenced by an intense oxygen minimum zone (OMZ), which impinges on the continental slope from 100 to 1000 m water depth. We compared the trophic ecology of foraminifera on the Oman and Pakistan margins of the Arabian Sea (140-3185 m water depth). These two margins are contrasting both in terms of the abundance of sedimentary organic matter and the intensity of the OMZ. Organic carbon concentrations of surficial sediments were higher on the Oman margin (3.32 ± 1.4%) compared to the Pakistan margin (2.45 ± 1.1%) and sedimentary organic matter (SOM) quality estimated from the Hydrogen Index was also higher on the Oman margin (300-400 mg HC mg TOC-1) compared to the Pakistan margin (< 250 mg HC mg TOC-1). The δ13C and δ15N values of sediments were similar on both margins (-20 and 8‰, respectively). Stable isotope analysis (SIA) showed that foraminiferal cells had a wide range of δ13C values (-25.5 to -11.5‰), implying that they utilise multiple food sources; indeed δ13C values varied between depths, foraminiferal types and between the two margins. Foraminifera had broad ranges in δ15N values (-7.8 to 27.3‰). The enriched values suggest that some species may store nitrate to utilise in respiration; this was most notable on the Pakistan margin. Depleted foraminiferal δ15N values, particularly at the Oman margin, may reflect feeding on chemosynthetic bacteria. We suggest that differences in productivity regimes may be responsible for the differences observed in foraminiferal isotopic composition. In addition, at the time of sampling, whole jellyfish carcasses (Crambionella orsini) and a carpet of jelly detritus were observed across the Oman margin transect. Associated chemosynthetic bacteria may have

  11. The trophic and metabolic pathways of foraminifera in the Arabian Sea: evidence from cellular stable isotopes

    NASA Astrophysics Data System (ADS)

    Jeffreys, R. M.; Fisher, E. H.; Gooday, A. J.; Larkin, K. E.; Wolff, G. A.; Billett, D. S. M.

    2014-12-01

    The Arabian Sea is a region of elevated productivity with the highest globally recorded fluxes of particulate organic matter (POM) to the deep ocean, providing an abundant food source for fauna at the seafloor. However, benthic communities are also strongly influenced by an intense oxygen minimum zone (OMZ), which impinges on the continental slope at bathyal depths. We compared the trophic ecology of foraminifera on the Oman and Pakistan margins of the Arabian Sea (140-3185 m water depth). Organic carbon concentrations of surficial sediments were higher on the Oman margin (3.32 ± 1.4%) compared to the Pakistan margin (2.45 ± 1.1%) and sedimentary organic matter (SOM) quality estimated from the Hydrogen Index was also higher on the Oman margin (300-400 mg HC (mg TOC)-1) compared to the Pakistan margin (<250 mg HC (mg TOC)-1). δ13C and δ15N values of sediments were similar on both margins (-20 and 8‰, respectively). Stable isotope analysis (SIA) showed that foraminiferal cells had a wide range of δ13C values (-25.5 to -11.5‰), implying that they utilise multiple food sources; indeed δ13C values varied between depths, foraminiferal types and between the two margins. Foraminifera had broad ranges in δ15N values (-7.8 to 27.3‰). The enriched values suggest that some species may store nitrate to utilise in respiration; this was most notable on the Pakistan margin. Depleted foraminiferal δ15N values were identified on both margins, particularly the Oman margin, and may reflect feeding on chemosynthetic bacteria. We suggest that differences in productivity regimes between the two margins may be responsible for the differences observed in foraminiferal isotopic composition. In addition, at the time of sampling, whole jellyfish carcasses (Crambionella orsini) and a carpet of jelly detritus were observed across the Oman margin transect. Associated chemosynthetic bacteria may have provided an organic-rich food source for foraminifera at these sites. Our data

  12. Biological response due to tropical cyclone PHYN in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Rao Neerukattu, Srinivasa; Rao, B. Venkateswara

    During the fall intermonsoon cyclone PHYN (09-11 Nov 2009) occurred in the Northeast Ara-bian Sea, we observed 4.4 C mean Sea Surface Temperature (SST) drop in Aqua-MODIS derived SST data; where the maximum wind speeds recorded were of the order of 50 Knots. High wind speeds deepened the vertical mixing of 90 m, and brought the cold (23.9C), nutrient rich waters to the surface; this is confirmed with Argo's temperature profile data. Post cyclone chlorophyll-a (Chl-a) enhancement was observed through 8 day mean average chlorophyll-a derived from Aqua-MODIS data, concentration from 4.56 mg/m3 to 16 mg/m3. SST drop and Chl-a Enhancement are not continuum all along the cyclone path; Maximum SST drop and Chl-a enhancement are observed at the establishment of `cyclone eye'. The formation of an eye is almost always an indicator of increasing tropical cyclone organization and strength. Where the cyclone stalls, its movement has fallen below 2.24m/s, movement is erratic over a small area; the wave action caused by the strong surface winds churns the ocean surface and produces upwelling. This has the effect of cooling the temperature of the sea surface over an area 200 to 300 miles across. Strong asymmetry in the SST response occurs in the wake of the storm. These results in a cool swath of SST centered 50-400 km on the right hand side of the storm track. SST drop 3o C larger than on left hand side of the track. Tropical cyclones when passing over land may have destroying human lives, but over the ocean they can strongly enhance biological life i.e. enhancing phytoplankton (Chl-a) biomass.

  13. Correlation between some selected trace metal concentrations in six species of fish from the Arabian Sea

    SciTech Connect

    Ashraf, M.; Jaffar, M.

    1988-07-01

    The role of trace metals in marine ecosystems has been keenly investigated during recent years. It is known that abundance of essential trace metals regulates the metal content in the organisms by homeostatic control mechanisms, which when cease to function cause essential trace metals to act in an either acutely or chronically toxic manner. Therefore, a correlation study based on essential and non-essential trace metal concentrations is imperative for extending the existing knowledge of bioaccumulation of trace metals in marine organisms. An attempt has been made in the present investigation to bring out quantitative correlations between the concentrations of iron, copper, lead and zinc in the edible muscle tissue of six species of marine fish: Salmon (salmon sole); tuna (thunnus thynnus); pomfret silver (pampus argenteus); Pomfret black (formioniger); long tail tuna (thynnus tonggel) and Indian oil sardine (sardinella longiceps). These fish are abundantly available in Pakistan along the coastal line of the Arabian Sea and have great commercial value. The computational analysis on the trace metal correlation was conducted using an MSTAT statistical package.

  14. Trace metals health risk appraisal in fish species of Arabian Sea.

    PubMed

    Yasmeen, Kousar; Mirza, Muhammad Aslam; Khan, Namra A; Kausar, Nazish; Rehman, Atta-Ur; Hanif, Muddasir

    2016-01-01

    Fish is a vital food for humans and many animals. We report an environmental monitoring study to assess the trace metals in fish species caught from Arabian Sea and commercially available in the coastal city Karachi, Pakistan. Heavy metals such as copper, iron, lead and cadmium were determined in the skin, fillet and heart of the fish species Pampus argenteus, Epinephelus chlorostigma, Rachycentron canadum, Scomberomorus commerson, Johnius belangerii, Labeo rohita, Lutjanus argentimaculatus, Trachinotus blochii, Pomadsys olivaceum and Acanthopagrus berda by the atomic absorption spectrophotometer. The concentration (mg kg(-1), dry weight) range was: Cd (0.00-0.041), Cu (0.006-0.189), Fe (0.413-4.952) and Pb (0.00-0.569). Cadmium, copper and iron levels were below the tolerable limits whereas concentration of lead in the skins of S. commerson, E. chlorostigma, J. belangerii, A. berda; L. argentimaculatus, fillets of J. belangerii, E. chlorostigma and in the heart of J. belangerii exceeded the recommended limits. Therefore fish skin should be discouraged as food for humans or animals. The results indicate that a number of fish species have higher concentration of heavy metals dangerous for human health. Since the fish P. olivaceum (Dhotar) has the lowest level of trace metals therefore we recommend it for breeding and human consumption. PMID:27386308

  15. Evolution to decay of upwelling and associated biogeochemistry over the southeastern Arabian Sea shelf

    NASA Astrophysics Data System (ADS)

    Gupta, G. V. M.; Sudheesh, V.; Sudharma, K. V.; Saravanane, N.; Dhanya, V.; Dhanya, K. R.; Lakshmi, G.; Sudhakar, M.; Naqvi, S. W. A.

    2016-01-01

    Observations along 10 shelf transects in 2012 near 10°N in the southeastern Arabian Sea revealed the usual warm oligotrophic conditions during the winter monsoon and upwelling of oxygen-deficient, nutrient-rich cool water during the summer monsoon (SM). By changing an oligotrophic to a nutrient-replete condition, the upwelling is the major process that regulates the biogeochemistry of this shelf. Its onset is perceptible at 100 m depth between January and March. The upwelling reaches the surface layer in May and intensifies during June-July but withdraws completely and abruptly by October. Despite the nutrient injection, the primary production during SM, integrated for euphotic zone, is comparable to that during the preceding spring intermonsoon (SIM). Again, as usual, the high oxygen demand coupled with low concentration in the upwelled subsurface waters causes severe oxygen depletion below the shallow pycnocline. The oxygen concentrations/saturations of 2012 on the midshelf are similar from those of mid-1958 to early 1960, except for marginally higher values during the peak upwelling period due to relatively weak upwelling in 2012. This implies little anthropogenic influence on coastal hypoxia unlike many other coastal regions. In 2012, the inner shelf system shifted from net autotrophy in SIM to net heterotrophy in SM but on an annual basis it was net autotrophic (gross primary production to community respiration ratio, GPP/R:1.11 ± 0.84) as organic production exceeded consumption.

  16. Species identification of mixed algal bloom in the Northern Arabian Sea using remote sensing techniques.

    PubMed

    Dwivedi, R; Rafeeq, M; Smitha, B R; Padmakumar, K B; Thomas, Lathika Cicily; Sanjeevan, V N; Prakash, Prince; Raman, Mini

    2015-02-01

    Oceanic waters of the Northern Arabian Sea experience massive algal blooms during winter-spring (mid Feb-end Mar), which prevail for at least for 3 months covering the entire northern half of the basin from east to west. Ship cruises were conducted during winter-spring of 2001-2012 covering different stages of the bloom to study the biogeochemistry of the region. Phytoplankton analysis indicated the presence of green tides of dinoflagellate, Noctiluca scintillans (=N. miliaris), in the oceanic waters. Our observations indicated that diatoms are coupled and often co-exist with N. scintillans, making it a mixed-species ecosystem. In this paper, we describe an approach for detection of bloom-forming algae N. scintillans and its discrimination from diatoms using Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua data in a mixed-species environment. In situ remote sensing reflectance spectra were generated using Satlantic™ hyperspectral radiometer for the bloom and non-bloom waters. Spectral shapes of the reflectance spectra for different water types were distinct, and the same were used for species identification. Scatter of points representing different phytoplankton classes on a derivative plot revealed four diverse clusters, viz. N. scintillans, diatoms, non-bloom oceanic, and non-bloom coastal waters. The criteria developed for species discrimination were implemented on MODIS data and validated using inputs from a recent ship cruise conducted in March 2013. PMID:25638059

  17. The Lighthouse Ocean Research Initiative: Sustained Cabled Ocean Observing Systems in the Sea of Oman and Arabian Sea

    NASA Astrophysics Data System (ADS)

    Ingle, S.; Du Vall, K.; Dimarco, S. F.

    2011-12-01

    In 2003 Lighthouse R & D Enterprises, Inc. began developing an ocean observing system that would help the Sultanate of Oman better manage the health of their fisheries. The resulting cutting-edge, fiber-optic cabled ocean observatory was installed in the northern Sea of Oman and became operational in August of 2005; this summer the system surpassed the milestone of 2100 days of successful operation. A second, deepwater cabled observatory was installed farther to the south, where the Sea of Oman meets the Arabian Sea, in January, 2010. Both systems monitor physical properties throughout the water column including current velocity, temperature, pressure, conductivity, dissolved oxygen and turbidity. The entirely subsea nature of the fiber-optic cabled observatory capitalizes on several advantages over traditional buoyed systems including a lack of exposure to environmental wear and tear, collision, vandalism and theft. The systems are both cabled to nearby shore facilities, where the data are relayed instantly to Houston via satellite for processing, analysis and modeling - the data may also be used in making real time decisions. Many challenges were encountered between the design / development stage and the operation a reliable, long-term, real-time observing system in a dynamic marine environment. Examples of obstacles we encountered and overcame include: maintaining upright mooring strings under differential current velocities; minimizing points of weakness in the system, especially the number of wet mates; recognizing the need for cathodic protection in unanticipated places; protecting vulnerable sensors from biofouling; developing a climate-controlled shore facility in a harsh and remote environment; ensuring an uninterrupted power supply and availability of additional power bursts when required; and lengthening the life of the system while reducing the need for maintenance. The design and obstacles and scientific questions being addressed by the Lighthouse

  18. Seismic anisotropy and subduction-induced mantle fabrics beneath the Arabian and Nubian Plates adjacent to the Red Sea

    NASA Astrophysics Data System (ADS)

    Elsheikh, Ahmed A.; Gao, Stephen S.; Liu, Kelly H.; Mohamed, Abdelnasser A.; Yu, Youqiang; Fat-Helbary, Raafat E.

    2014-04-01

    For most continental areas, the mechanisms leading to mantle fabrics responsible for the observed anisotropy remain ambiguous, partially due to the lack of sufficient spatial coverage of reliable seismological observations. Here we report the first joint analysis of shear-wave splitting measurements obtained at stations on the Arabian and Nubian Plates adjacent to the Red Sea. More than 1100 pairs of high-quality splitting parameters show dominantly N-S fast orientations at all 47 stations and larger-than-normal splitting times beneath the Afro-Arabian Dome (AAD). The uniformly N-S fast orientations and large splitting times up to 1.5 s are inconsistent with significant contributions from the lithosphere, which is about 50-80 km thick beneath the AAD and even thinner beneath the Red Sea. The results can best be explained by simple shear between the lithosphere and the asthenosphere associated with northward subduction of the African/Arabian Plates over the past 150 Ma.

  19. The effect of Arabian Sea optical properties on SST biases and the South Asian summer monsoon in a coupled GCM

    NASA Astrophysics Data System (ADS)

    Turner, A. G.; Joshi, M.; Robertson, E. S.; Woolnough, S. J.

    2012-08-01

    This study examines the effect of seasonally varying chlorophyll on the climate of the Arabian Sea and South Asian monsoon. The effect of such seasonality on the radiative properties of the upper ocean is often a missing process in coupled general circulation models and its large amplitude in the region makes it a pertinent choice for study to determine any impact on systematic biases in the mean and seasonality of the Arabian Sea. In this study we examine the effects of incorporating a seasonal cycle in chlorophyll due to phytoplankton blooms in the UK Met Office coupled atmosphere-ocean GCM HadCM3. This is achieved by performing experiments in which the optical properties of water in the Arabian Sea—a key signal of the semi-annual cycle of phytoplankton blooms in the region—are calculated from a chlorophyll climatology derived from Sea-viewing Wide Field-of-View Sensor (SeaWiFS) data. The SeaWiFS chlorophyll is prescribed in annual mean and seasonally-varying experiments. In response to the chlorophyll bloom in late spring, biases in mixed layer depth are reduced by up to 50% and the surface is warmed, leading to increases in monsoon rainfall during the onset period. However when the monsoons are fully established in boreal winter and summer and there are strong surface winds and a deep mixed layer, biases in the mixed layer depth are reduced but the surface undergoes cooling. The seasonality of the response of SST to chlorophyll is found to depend on the relative depth of the mixed layer to that of the anomalous penetration depth of solar fluxes. Thus the inclusion of the effects of chlorophyll on radiative properties of the upper ocean acts to reduce biases in mixed layer depth and increase seasonality in SST.

  20. Particle size distribution and estimated carbon flux across the Arabian Sea oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Roullier, F.; Berline, L.; Guidi, L.; Durrieu De Madron, X.; Picheral, M.; Sciandra, A.; Pesant, S.; Stemmann, L.

    2014-08-01

    The goal of the Arabian Sea section of the TARA oceans expedition was to study large particulate matter (LPM > 100 μm) distributions and possible impact of associated midwater biological processes on vertical carbon export through the oxygen minimum zone (OMZ) of this region. We propose that observed spatial patterns in LPM distribution resulted from the timing and location of surface phytoplankton bloom, lateral transport, microbial processes in the core of the OMZ, and enhanced biological processes mediated by bacteria and zooplankton at the lower oxycline. Indeed, satellite-derived net primary production maps showed that the northern stations of the transect were under the influence of a previous major bloom event while the most southern stations were in a more oligotrophic situation. Lagrangian simulations of particle transport showed that deep particles of the northern stations could originate from the surface bloom while the southern stations could be considered as driven by 1-D vertical processes. In the first 200 m of the OMZ core, minima in nitrate concentrations and the intermediate nepheloid layer (INL) coincided with high concentrations of 100 μm < LPM < 200 μm. These particles could correspond to colonies of bacteria or detritus produced by anaerobic microbial activity. However, the calculated carbon flux through this layer was not affected. Vertical profiles of carbon flux indicate low flux attenuation in the OMZ, with a Martin model b exponent value of 0.22. At three stations, the lower oxycline was associated to a deep nepheloid layer, an increase of calculated carbon flux and an increase in mesozooplankton abundance. Enhanced bacterial activity and zooplankton feeding in the deep OMZ is proposed as a mechanism for the observed deep particle aggregation. Estimated lower flux attenuation in the upper OMZ and re-aggregation at the lower oxycline suggest that OMZ may be regions of enhanced carbon flux to the deep sea relative to non OMZ regions.

  1. Particles size distribution and carbon flux across the Arabian Sea Oxygen Minimum Zone

    NASA Astrophysics Data System (ADS)

    Roullier, F.; Berline, L.; Guidi, L.; Sciandra, A.; Durrieu De Madron, X.; Picheral, M.; Pesant, S.; Stemmann, L.

    2013-12-01

    The goal of the Arabian Sea section of the TARA oceans expedition was to study Large Particulate Matter (LPM > 100 μm) distributions and possible impact of associated midwater biological processes on vertical carbon export through the Oxygen Minimum Zone (OMZ) of this region. We found that spatial patterns in LPM distribution resulted from the timing and location of surface phytoplankton bloom, lateral transport, microbial processes in the core of the OMZ, and zooplankton activity at the lower oxycline. Indeed, satellite-derived net primary production maps showed that the northern stations of the transect were under the influence of a previous major bloom event while, the most southern stations were in a more oligotrophic situation. Lagrangian simulations of particle transport showed that deep particles of the northern stations could originate from the surface bloom while the southern stations could be considered as driven by 1-D vertical processes. In the first 200 m of the OMZ core, minima in nitrate concentrations and the Intermediate Nepheloid Layer (INL) coincided with high concentrations of 100 μm < LPM < 200 μm. These particles could correspond to colonies of bacteria or detritus produced by anaerobic microbial activity. However, the calculated carbon flux through this layer was not affected. Vertical profiles of carbon flux indicate low flux attenuation in the OMZ, with a Martin model b exponent value of 0.22. At the lower oxycline, a deep nepheloid layer was associated to an increase of carbon flux and an increase in mesozooplankton abundance. Zooplankton feeding on un-mineralized sinking particles in the OMZ is proposed as a mechanism for the observed deep particle aggregation. These results suggest that OMZ may be regions of enhanced carbon flux to the deep sea relative to non-OMZ regions.

  2. The stratigraphic evolution of the Indus Fan and the history of sedimentation in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Clift, Peter; Gaedicke, Christoph; Edwards, Rosemary; Il Lee, Jae; Hildebrand, Peter; Amjad, Shahid; White, Robert S.; Schlüter, Hans-Ulrich

    The Indus Fan records the erosion of the western Himalayas and Karakoram since India began to collide with Asia during the Eocene, ~50 Ma. Multi-channel seismic reflection data from the northern Arabian Sea correlated to industrial well Indus Marine A-1 on the Pakistan Shelf show that sedimentation patterns are variable through time, reflecting preferential sedimentation in deep water during periods of lower sea-level (e.g., middle Miocene, Pleistocene), the diversion of sediment toward the east following uplift of the Murray Ridge, and the autocyclic switching of fan lobes. Individual channel-levee systems are estimated to have been constructed over periods of 105-106 yr during the Late Miocene. Sediment velocities derived from sonobuoys and multi-channel stacking velocities allow sections to be time-depth converted and then backstripped to calculate sediment budgets through time. The middle Miocene is the period of most rapid accumulation, probably reflecting surface uplift in the source regions and strengthening of the monsoon at that time. Increasing sedimentation during the Pleistocene, after a late Miocene-Pliocene minimum, is apparently caused by faster erosion during intense glaciation. The sediment-unloaded geometry of the basement under the Pakistan Shelf shows a steep gradient, similar to the continent-ocean transition seen at other rifted volcanic margins, with basement depths on the oceanward side indistinguishable from oceanic crust. Consequently we suggest that the continent-ocean transition is located close to the present shelf break, rather than >350 km to the south, as previously proposed.

  3. Identification of new deep sea sinuous channels in the eastern Arabian Sea.

    PubMed

    Mishra, Ravi; Pandey, D K; Ramesh, Prerna; Clift, Peter D

    2016-01-01

    Deep sea channel systems are recognized in most submarine fans worldwide as well as in the geological record. The Indus Fan is the second largest modern submarine fan, having a well-developed active canyon and deep sea channel system. Previous studies from the upper Indus Fan have reported several active channel systems. In the present study, deep sea channel systems were identified within the middle Indus Fan using high resolution multibeam bathymetric data. Prominent morphological features within the survey block include the Raman Seamount and Laxmi Ridge. The origin of the newly discovered channels in the middle fan has been inferred using medium resolution satellite bathymetry data. Interpretation of new data shows that the highly sinuous deep sea channel systems also extend to the east of Laxmi Ridge, as well as to the west of Laxmi Ridge, as previously reported. A decrease in sinuosity southward can be attributed to the morphological constraints imposed by the elevated features. These findings have significance in determining the pathways for active sediment transport systems, as well as their source characterization. The geometry suggests a series of punctuated avulsion events leading to the present array of disconnected channels. Such channels have affected the Laxmi Basin since the Pliocene and are responsible for reworking older fan sediments, resulting in loss of the original erosional signature supplied from the river mouth. This implies that distal fan sediments have experienced significant signal shredding and may not represent the erosion and weathering conditions within the onshore basin at the time of sedimentation. PMID:27386293

  4. Acoustic doppler current profiling from the JGOFS Arabian Sea cruises aboard the RV T.G. Thompson

    SciTech Connect

    Flagg, C.N.; Shi, Y.

    1995-04-01

    Acoustic Doppler Current Profiler (ADCP) data from the R/V T.G. THOMPSON is part of the core data for the US JGOFS Arabian Sea project along with hydrographic and nutrient data. Seventeen cruises on the THOMPSON are scheduled to take place between September 1994 and January 1996. The first of these cruises, a transit of the R/V THOMPSON into the northern Arabian Sea area from Singapore, was a calibration and training cruise that took place between September 18 and October 7, 1994. (The cruises on the THOMPSON are numbered consecutively from the ship`s commissioning with the first JOGFS cruise designated TN039.) The remaining cruises have been and will be staged from Muscat, Oman. Seven of these cruises, referred to as process cruises, will follow a set cruise track, making hydrographic, chemical and biological measurements. The remainder of the cruises while not restricted to the set cruise track, will generally stay within the region defined by the track during the deployment and retrieval of moored equipment and the towing of a SeaSoar. Each cruise will last between two weeks and one month. ADCP data will be collected on all the JGOFS Arabian Sea cruises using an autonomous data acquisition system developed for ship-of-opportunity cruises. This system, referred to as the AutoADCP, makes it possible to collect the ADCP data without the constant monitoring usually necessary and assures constant data coverage and uniform data quality. The AutoADCP system is an extension of RD Instrument`s DAS version 2.48 using enhancements made possible with ``user exit`` programs. This data report presents ADCP results from the first four JGOFS cruises, TN039 through TN042, concentrating on the data collection and processing methods.

  5. Mesoscale variability in the Arabian Sea from HYCOM model results and observations: impact on the Persian Gulf Water path

    NASA Astrophysics Data System (ADS)

    L'Hégaret, P.; Duarte, R.; Carton, X.; Vic, C.; Ciani, D.; Baraille, R.; Corréard, S.

    2015-09-01

    The Arabian Sea and Sea of Oman circulation and water masses, subject to monsoon forcing, reveal a strong seasonal variability and intense mesoscale features. We describe and analyze this variability and these features, using both meteorological data (from ECMWF reanalyses), in situ observations (from the ARGO float program and the GDEM - Generalized Digital Environmental mode - climatology), satellite altimetry (from AVISO) and a regional simulation with a primitive equation model (HYCOM - the Hybrid Coordinate Ocean Model). The model and observations display comparable variability, and the model is then used to analyze the three-dimensional structure of eddies and water masses with higher temporal and spatial resolutions than the available observations. The mesoscale features are highly seasonal, with the formation of coastal currents, destabilizing into eddies, or the radiation of Rossby waves from the Indian coast. The mesoscale eddies have a deep dynamical influence and strongly drive the water masses at depth. In particular, in the Sea of Oman, the Persian Gulf Water presents several offshore ejection sites and a complex recirculation, depending on the mesoscale eddies. The associated mechanisms range from coastal ejection via dipoles, alongshore pulses due to a cyclonic eddy, to the formation of lee eddies downstream of Ra's Al Hamra. This water mass is also captured inside the eddies via several mechanisms, keeping high thermohaline characteristics in the Arabian Sea. The variations of the outflow characteristics near the Strait of Hormuz are compared with variations downstream.

  6. Arabian Night and Sea Story - Biomarkers from a Giant Mass Transport Deposit.

    NASA Astrophysics Data System (ADS)

    Bratenkov, Sophia; Kulhanek, Denise K.; Clift, Peter D.; George, Simon C.

    2016-04-01

    The study of mass transport deposits (MTDs) is an important field of research due to the potential insights into catastrophic events in the past and modern geohazard threats (e.g. tsunamis). Submarine mass movements are very significant processes in sculpturing the structure of continental margins, particularly in their extent and magnitude that have consequences both in the modern day, as well as in the geological past. An understanding of the complex stratigraphy of a submarine mass transport deposit (MTD) might help in reconstructing the provenance and transport pathways of sedimentary material and thus give important insights into sedimentary dynamics and processes triggering specific events. Drilling operations during International Ocean Discovery Program (IODP) Expedition 355 Arabian Sea Monsoon, which took place during April and May, 2015 cored two sites in Laxmi Basin. Site U1456 was cored to 1109.4 m below seafloor (mbsf), with the oldest recovered rock dated to ~13.5-17.7 Ma. Site U1457 was cored to 1108.6 mbsf, with the oldest rock dated to ~62 Ma. At each site, we cored through ~330 m and ~190 m of MTD material. The MTD layers mainly consist of interbedded lithologies of dark grey claystone, light greenish calcarenite and calcilutite, and conglomerate/breccia, with ages based on calcareous nannofossil and foraminifer biostratigraphy ranging from the Eocene to early Miocene (Pandey et al., 2015). This MTD, known as Nataraja Slide, is the third largest MTD known from the geological record and the second largest on a passive margin. Calvés et al. (2015) identified a potential source area offshore Sourashstra on the Indian continental margin and invoked the single step mass movement model to explain the mechanism of emplacement. Initial shipboard work demonstrated the high variability in total organic carbon and total nitrogen levels in different layers within the MTD, which raises a number of questions related to the source and composition of the organic

  7. Characteristics of monsoon inversions over the Arabian Sea observed by satellite sounder and reanalysis data sets

    NASA Astrophysics Data System (ADS)

    Dwivedi, Sanjeev; Narayanan, M. S.; Venkat Ratnam, M.; Narayana Rao, D.

    2016-04-01

    Monsoon inversion (MI) over the Arabian Sea (AS) is one of the important characteristics associated with the monsoon activity over Indian region during summer monsoon season. In the present study, we have used 5 years (2009-2013) of temperature and water vapour measurement data obtained from satellite sounder instrument, an Infrared Atmospheric Sounding Interferometer (IASI) onboard MetOp satellite, in addition to ERA-Interim data, to study their characteristics. The lower atmospheric data over the AS have been examined first to identify the areas where MIs are predominant and occur with higher strength. Based on this information, a detailed study has been made to investigate their characteristics separately in the eastern AS (EAS) and western AS (WAS) to examine their contrasting features. The initiation and dissipation times of MIs, their percentage occurrence, strength, etc., has been examined using the huge database. The relation with monsoon activity (rainfall) over Indian region during normal and poor monsoon years is also studied. WAS ΔT values are ˜ 2 K less than those over the EAS, ΔT being the temperature difference between 950 and 850 hPa. A much larger contrast between the WAS and EAS in ΔT is noticed in ERA-Interim data set vis-à-vis those observed by satellites. The possibility of detecting MI from another parameter, refractivity N, obtained directly from another satellite constellation of GPS Radio Occultation (RO) (COSMIC), has also been examined. MI detected from IASI and Atmospheric Infrared Sounder (AIRS) onboard the NOAA satellite have been compared to see how far the two data sets can be combined to study the MI characteristics. We suggest MI could also be included as one of the semipermanent features of southwest monsoon along with the presently accepted six parameters.

  8. Locating Noctiluca Miliaris in the Arabian Sea: An Optical Proxy Approach

    NASA Technical Reports Server (NTRS)

    Thibodeau, Patricia S.; Roesler, Collin S.; Drapeau, Susan L.; Matondkar, S. G. Prabhu; Goes, Joaquim I.; Werdell, P. Jeremy

    2014-01-01

    Coincident with shifting monsoon weather patterns over India, the phytoplankter Noctiluca miliaris has recently been observed to be dominating phytoplankton blooms in the northeastern Arabian Sea during the winter monsoons. Identifying the exact environmental and/or ecological conditions that favor this species has been hampered by the lack of concurrent environmental and biological observations on time and space scales relevant to ecologic and physiologic processes. We present a bio-optical proxy for N. miliaris measured on highly resolved depth scales coincident with hydrographic observations with the goal to identify conducive hydrographic conditions for the bloom. The proxy is derived from multichannel excitation chlorophyll a fluorescence and is validated with microscopy, pigment composition, and spectral absorption. Phytoplankton populations dominated by either diatoms or other dinoflagellates were additionally discerned. N. miliaris populations in full bloom were identified offshore in low-nutrient and low-N : P ratio surface waters within a narrow temperature and salinity range. These populations transitioned to high-biomass diatom-dominated coastal upwelling populations. A week later, the N. miliaris blooms were observed in declining phase, transitioning to very-low-biomass populations of non-N. miliaris dinoflagellates. There were no clear hydrographic conditions uniquely associated with the N. miliaris populations, although N. miliaris was not found in the upwelling or extremely oligotrophic waters. Taxonomic transitions were not discernible in the spatial structure of the bloom as identified by the ocean color Chl imagery, indicating that in situ observations may be necessary to resolve community structure, particularly for populations below the surface.

  9. Species delimitation in the coral genus Goniopora (Scleractinia, Poritidae) from the Saudi Arabian Red Sea.

    PubMed

    Terraneo, Tullia I; Benzoni, Francesca; Arrigoni, Roberto; Berumen, Michael L

    2016-09-01

    Variable skeletal morphology, genotype induced plasticity, and homoplasy of skeletal structures have presented major challenges for scleractinian coral taxonomy and systematics since the 18th century. Although the recent integration of genetic and micromorphological data is helping to clarify the taxonomic confusion within the order, phylogenetic relationships and species delimitation within most coral genera are still far from settled. In the present study, the species boundaries in the scleractinian coral genus Goniopora were investigated using 199 colonies from the Saudi Arabian Red Sea and sequencing of four molecular markers: the mitochondrial intergenic spacer between CytB and NAD2, the nuclear ribosomal ITS region, and two single-copy nuclear genes (ATPsβ and CalM). DNA sequence data were analyzed using a variety of methods and exploratory species-delimitation tools. The results were broadly congruent in identifying five distinct molecular lineages within the sequenced Goniopora samples: G. somaliensis/G. savignyi, G. djiboutiensis/G. lobata, G. stokesi, G. albiconus/G. tenuidens, and G. minor/G. gracilis. Although the traditional macromorphological characters used to identify these nine morphospecies were not able to discriminate the obtained molecular clades, informative micromorphological and microstructural features (such as the micro-ornamentation and the arrangement of the columella) were recovered among the five lineages. Moreover, unique in vivo morphologies were associated with the genetic-delimited lineages, further supporting the molecular findings. This study represents the first attempt to identify species boundaries within Goniopora using a combined morpho-molecular approach. The obtained data establish a basis for future taxonomic revision of the genus, which should include colonies across its entire geographical distribution in the Indo-Pacific. PMID:27321092

  10. Characteristics of Monsoon inversions over Arabian Sea observed by satellite sounder and reanalysis data sets

    NASA Astrophysics Data System (ADS)

    Dwivedi, Sanjeev; Narayanan, M. S.; Venkat Ratnam, M.; Narayana Rao, D.

    2015-12-01

    Monsoon inversions (MIs) over Arabian Sea (AS) are an important characteristic associated with the monsoon activity over Indian region during summer monsoon season. In the present study, we have used five years (2009-2013) data of temperature and water vapor profiles obtained from satellite sounder instrument, Infrared Atmospheric Sounding Interferometer (IASI) onboard MetOp satellite, besides ERA-Interim data, to study their characteristics. The lower atmospheric data over the AS have been examined first to identify the areas where monsoon inversions are predominant and occur with higher strength. Based on this information, a detailed study has been made to investigate their characteristics separately in eastern AS (EAS) and western AS (WAS) to examine their contrasting features. The initiation and dissipation times of MI, their percentage occurrence, strength etc., has been examined using the huge data base. The relation with monsoon activity (rainfall) over Indian region during normal and poor monsoon years is also studied. WAS ΔT values are ~ 2 K less than those over the EAS, ΔT being temperature difference between 950 and 850 hPa. A much larger contrast between WAS and EAS in ΔT is noticed in ERA-Interim dataset Vis a Vis those observed by satellites. The possibility of detecting MI from another parameter, Refractivity N, obtained directly from another satellite constellation of GPS RO (COSMIC), has also been examined. MI detected from IASI and Atmospheric InfraRed Sounder (AIRS) sounder onboard NOAA satellite have been compared to see how far the two data sets can be combined to study the MI characteristics. We suggest MI could also be included as one of the semi-permanent features of southwest monsoon along with the presently accepted six parameters.

  11. Seismic Velocity Structure and Depth-Dependence of Anisotropy in the Red Sea and Arabian Shield from Surface Wave Analysis

    SciTech Connect

    Hansen, S; Gaherty, J; Schwartz, S; Rodgers, A; Al-Amri, A

    2007-07-25

    We investigate the lithospheric and upper mantle structure as well as the depth-dependence of anisotropy along the Red Sea and beneath the Arabian Peninsula using receiver function constraints and phase velocities of surface waves traversing two transects of stations from the Saudi Arabian National Digital Seismic Network. Frequency-dependent phase delays of fundamental-mode Love and Rayleigh waves, measured using a cross-correlation procedure, require very slow shear velocities and the presence of anisotropy throughout the upper mantle. Linearized inversion of these data produce path-averaged 1D radially anisotropic models with about 4% anisotropy in the lithosphere, increasing to about 4.8% anisotropy across the lithosphere-asthenosphere boundary (LAB). Models with reasonable crustal velocities in which the mantle lithosphere is isotropic cannot satisfy the data. The lithospheric lid, which ranges in thickness from about 70 km near the Red Sea coast to about 90 km beneath the Arabian Shield, is underlain by a pronounced low-velocity zone with shear velocities as low as 4.1 km/s. Forward models, which are constructed from previously determined shear-wave splitting estimates, can reconcile surface and body wave observations of anisotropy. The low shear velocity values are similar to many other continental rift and oceanic ridge environments. These low velocities combined with the sharp velocity contrast across the LAB may indicate the presence of partial melt beneath Arabia. The anisotropic signature primarily reflects a combination of plate- and density-driven flow associated with active rifting processes in the Red Sea.

  12. 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.

  13. Limpets of the genus Cellana (Patellogastropoda) from Pakistan, North Arabian Sea: species identification based on DNA sequencing.

    PubMed

    Zafar, Fatima Hayat Shaheen; Ayub, Zarrien; Begum, Samar; Siddiqui, Ghazala; Roberts, David

    2016-07-01

    The true limpets are found in the intertidal zone of the rocky shores of Pakistan, North Arabian Sea. Partial sequence of the mitochondrial cytochrome oxidase I was used to estimate the degree of genetic differentiation among the morphological forms of Cellana, which were considered as three separate species earlier in Pakistan. The study revealed that the three morphs of Cellana on COI sequence generated a single haplotype and matched with the COI sequence of Cellana karachiensis. This point out the phenotypic plasticity between the proposed species. PMID:26065851

  14. Extremely high aerosol loading over Arabian Sea during June 2008: The specific role of the atmospheric dynamics and Sistan dust storms

    NASA Astrophysics Data System (ADS)

    Kaskaoutis, D. G.; Rashki, A.; Houssos, E. E.; Goto, D.; Nastos, P. T.

    2014-09-01

    This study focuses on analyzing the extreme aerosol loading and the mechanisms, source areas and meteorological conditions that favored the abnormal dust exposure towards Arabian Sea during June 2008. The analysis reveals that the spatial-averaged aerosol optical depth (AOD) over Arabian Sea in June 2008 is 0.5 (78.2%) higher than the 2000-2013 mean June value and is mostly attributed to the enhanced dust activity and several (18) dust storms originated from the Sistan region (Iran-Afghanistan borders). Landsat images show that the marshy lakes in Sistan basin got dried during the second half of June 2008 and the alluvial silt and saline material got easily eroded by the intense Levar winds, which were stronger (>15-20 m s-1) than the climatological mean for the month of June. These conditions led to enhanced dust exposure from Sistan that strongly affected the northern and central parts of the Arabian Sea, as forward air-mass trajectories show. The NCEP/NCAR reanalysis reveals an abnormal intensification and spatial expansion of the Indian low pressure system towards northern Arabian Sea in June 2008. This suggests strengthening of the convection over the arid southwest Asia and exposure of significant amount of dust, which can reach further south over Arabian Sea favored by the enhanced cyclonic circulation. MODIS imagery highlighted several dust storms originated from Sistan and affecting Arabian Sea during June 2008, while the SPRINTARS model simulations of increased AOD and dust concentration over Sistan and downwind areas are in agreement with ground-based and satellite observations.

  15. Heavy mineral variation in the deep sea sediment of southeastern Arabian Sea during the past 32 kyr

    NASA Astrophysics Data System (ADS)

    Akaram, Vaseem; Das, S. S.; Rai, A. K.; Mishra, Gaurav

    2015-03-01

    The present study is based on heavy mineral assemblages (HM) of top 104-cm thick section of gravity core SK 221 (Lat. 8∘7.12'N; Long. 73∘16.38'E and water depth - 2188 m) located near the Chagos-Laccadive Ridge in the southeastern Arabian Sea to evaluate the provenance and paleoenvironmental changes during the last 32 kyr. The biogenic carbonate, acid insoluble residue, magnetic susceptibility, total organic carbon (TOC) and clay based humidity index, i.e., kaolinite/illite ratio are also utilized to correlate with the above paleoenvironmental changes. Ilmenite, garnet, staurolite, pyroxenes, andalusite and zircon are the dominant HM with moderate to low ZTR (zircon-tourmaline-rutile) index indicating instability of the sediments and rapid erosion in the source region. The characteristic HM suggest their mixed sources from the basic igneous, gneisses/granites, high grade metamorphic rocks and sandstones occurring mainly in the western and southwestern India. The temporal variations of HM, AIR (acid insoluble residue), MS (magnetic susceptibility), biogenic carbonate and Corg (TOC) during preglacial and early Holocene suggest intensive weathering, erosion, and transportation of terrigenous detritus from continental region by fluvial processes and summer monsoon led high biogenic productivity, respectively. The convective mixing of waters due to intense winter monsoon resulted in very high biogenic carbonate content during the early stages of glacial period. The HM and associated proxies indicated that the winter monsoons of Heinrich (H3, H2, and H1) and Younger Dryas (YD) events and summer monsoons of Bølling/Allerød (BA) event were not strong enough to bring drastic changes in the above parameters.

  16. Study of air-sea interaction processes over the Arabian Sea and the Bay of Bengal using satellite data

    SciTech Connect

    Gautam, N.; Simon, B.; Pandey, P.C.

    1995-12-01

    The main objective of this work is to study the latitudinal and seasonal variation of latent heat fluxes (LHF) and associated atmospheric and oceanic parameters over the Arabian Sea (AS) and the Bay of Bengal (BB) for the year 1988. A significant latitudinal variation is observed in LHF for most of the months over the AS and the BB, while other oceanic and atmospheric parameters are characterized by a strong latitudinal variation in nonmonsoon months. Seasonal variations in LHF are more significant at higher latitudes compared to lower latitudes over the AS and the BB. The effect of coastal upwelling near the Somali coast decreases LHF, while surface winds near the Indian coast during monsoon months increases LHF. A comparative study over the AS and the BB demonstrates higher PW and SST over the BB than over the AS. LHF is found to be greater over the AS than over the BB for nonmonsoon months. Correlation analysis indicates that LHF is found to be highly correlated with DQ (difference between the humidity at the surface and humidity near the surface) over the AS and weakly correlated over the BB during nonmonsoon months. Throughout the year, DQ is found to be a dominant factor for LHF over the AS. However, WS exercised better control over the BB in generating LHF. SST and PW are found to be highly correlated with each other over the AS (r = 0.87) and the BB (r = 0.75) for nonmonsoon months. The correlation becomes weakly negative over the AS (r = 0.15) and weak over the BB (r = 0.26) during monsoon months. Precipitable water is found to have a high correlation with WS over the AS (r = 0.72). This unique feature is revealed by SSM/I data and has not been reported earlier due to paucity of data over this region.

  17. Retrieval of near-surface bio-optical properties of the Arabian Sea from remotely sensed ocean colour data

    NASA Astrophysics Data System (ADS)

    Pinkerton, M. H.; Trees, C. C.; Aiken, J.; Bale, A. J.; Moore, G. F.; Barlow, R. G.; Cummings, D. G.

    1999-03-01

    The use of CZCS-type band-ratio algorithms to estimate the diffuse attenuation coefficient, percentage light depths, and near-surface optically weighted phytoplankton pigment concentrations from remotely sensed ocean colour data was investigated on two cruises in the Arabian Sea and Gulf of Oman during autumn and winter 1994. The variations of upwelling radiance and downwelling irradiance with depth were measured along with phytoplankton pigment concentrations by HPLC. A spectroradiometer was used on the second cruise to investigate the feasibility of measuring water-leaving radiance from above the sea surface. Retrieval of the diffuse downwelling attenuation coefficient at 490 nm was accurate to within 22% of the actual value across both cruises. There was also a robust relationship between the diffuse attenuation coefficient and the 10, 1 and 0.1% light depths. Above-surface estimates of water-leaving radiance agreed with SeaWiFS-standard estimates to within 10% between 443 and 555 nm. The global 443 : 555 band-ratio algorithms of Aiken et al. [NASA Tech. Memo 104566, Vol. 29, SeaWiFS Technical Report Series, 34 pp] estimated near-surface chlorophyll- a and fluorometric pigment concentrations with mean absolute errors of less than 35% of the actual values (which were all less than 2.0 mg m -3). The performance of algorithms based on the 490 : 555 ratio was poorer. The estimates given by the algorithms were generally higher than the measured pigment concentrations and the variance of the accuracy of the estimates was high. There appears to be no significant change in the performance of the algorithms between cruises (approximately 2 1/2 months apart in time). There is no evidence that the Gulf of Oman should be treated as a separate bio-optical province to the Arabian Sea/Omani shelf area for the purpose of the retrieval of near-surface pigment concentrations from ocean colour observations.

  18. Deep-water Thyasiridae (Mollusca: Bivalvia) from the Oman Margin, Arabian Sea, new species and examples of endemism and cosmopolitanism.

    PubMed

    Oliver, P Graham

    2015-01-01

    Seven species of Thyasiridae are reported from the Oman Margin of the Arabian Sea at depths between 688 m and 3356 m. Hypoxic conditions exist at depths between 400 and 1200 m and three species are restricted to this zone and to the Arabian Sea. Leptaxinus indusarium has also been recorded from the Indus Fan and Channelaxinus investigatoris from off Sri Lanka. A new species Thyasira anassa sp. nov. is described from the hypoxic zone. Another four species are recorded from the abyssal zone where oxygen levels are typical for the deep ocean. Here another new species is described, Parathyasira bamberi sp. nov. but the other species could not be conclusively identified because of close affinity with populations from other oceans.  Deep water Atlantic species Axinulus croulinensis and Mendicula ferruginosa are apparently present in the abyssal Indian Ocean while another thyasirid shell is very close to Channelaxinus excavatus from the Eastern Pacific and C. perplicata from the Atlantic. Accompanying these abyssal thyasirids were other bivalve species, Deminucula atacellana, Limopsis pelagica and Bentharca asperula that cannot be distinguished by morphology from their Atlantic populations. It is concluded that using morphology alone that the abyssal species may well be cosmopolitan in distribution. PMID:26250317

  19. Spatial variability in phytoplankton community structure along the eastern Arabian Sea during the onset of south-west monsoon

    NASA Astrophysics Data System (ADS)

    Ahmed, Ayaz; Kurian, Siby; Gauns, Mangesh; Chndrasekhararao, A. V.; Mulla, Amara; Naik, Bhagyashri; Naik, Hema; Naqvi, S. W. A.

    2016-05-01

    The Arabian Sea experiences moderate to weak upwelling along the south-west coast of India, which subsequently propagates towards the north. This causes variation in plankton community composition, which is addressed in the present study. Here we report the spatial variations in distribution of phytoplankton groups along the north-south transect in the eastern Arabian Sea based on marker pigments supported with flow-cytometric and microscopic analyses. 15 phytoplankton pigments were identified using High-performance liquid chromatography (HPLC) and the chemotaxonomic software (CHEMTAX) analysis associated these to seven major group of phytoplankton. The phytoplankton biomass, chlorophyll a (Chl a) was higher in southern stations with dominance of fucoxanthin whereas, divinyl chlorophyll a (divinyl Chl a), marker pigment of Prochlorococcus was present only in the northern region. Microscopic observation revealed the dominance of larger forms; diatoms (Chaetoceros coarctatum and Nitzschia sp.) and dinoflagellates (Scrippsiella sp., Oxytoxum nanum and Oxytoxum sp.) in the southern region. Furthermore, a study of plankton size distribution showed dominance of picoplankton (fpico) followed by nanoplankton (fnano) along the northern stations with comparatively higher microplankton (fmicro) in the south. This study clearly showed the influence of different environmental conditions on the phytoplankton community as reflected in dominance of diatoms in the southern (south of 12 °N) and that of picoplankton in the northern (north of 12 °N) region.

  20. Response of the Surface Circulation of the Arabian Sea to Monsoonal Forcing

    NASA Astrophysics Data System (ADS)

    Beal, L. M.; Hormann, V.; Lumpkin, R.; Foltz, G. R.

    2014-12-01

    We use two decades of drifter and satellite data to examine the monthly evolution of the surface circulation of the Arabian Sea, which reverses annually in response to the Indian monsoon winds. Most significantly, we find that in the transition from winter to summer circulations, northward flow appears along the length of the western boundary as early as March or April, one or two months before the onset of the southwest monsoon winds. This reversal is initiated by annual Rossby waves, which in turn are initiated by wind curl forcing during the previous southwest monsoon. These results lead us to speculate that there is an oceanic mechanism through which one monsoon may precondition the next. Previous studies of monsoon circulations with lower temporal resolution have highlighted basin-wide currents and connections that are not found to exist in the monthly fields. In particular, we find that the Northeast Monsoon Current does not reach the western boundary and there is no counter-rotating gyre system during boreal winter. South of the equator, the eastward-flowing South Equatorial Counter Current (SECC) is present year-round, even though equatorial winds are strongly influenced by the monsoons. Semi-annual variability of the SECC is governed by Ekman pumping over the south equatorial gyre (or Seychelles dome) and, surprisingly, it is weakest during the northeast monsoon. This region has important influence on the atmosphere and its link to the monsoons deserves further investigation. The East African Coastal Current feeds into the SECC from the boundary. During the southwest monsoon it overshoots the equator and splits, feeding both northward into the Somali Current and eastward into the SECC after looping back across the equator. This apparent retroflection of the EACC is what was previously known as the southern gyre and is obscured at the surface by strong, locally wind-driven, cross-equatorial Ekman transport. Finally, there is broad, strong eastward flow at

  1. Seasonal and annual variability of vertically migrating scattering layers in the northern Arabian Sea

    NASA Astrophysics Data System (ADS)

    Wang, Zhankun; DiMarco, Steven F.; Ingle, Stephanie; Belabbassi, Leila; Al-Kharusi, Lubna H.

    2014-08-01

    A 30-month time series of mean volume backscattering strength (MVBS) data obtained from moored acoustic Doppler current profilers (ADCPs) is used to analyze the evolution of vertically migrating scattering layers and their seasonal and annual variability in the Arabian and Oman Seas. Substantial diel vertical migration (DVM) is observed almost every day at all three mooring sites. Two daytime layers (Layers D1 and D2) and one nighttime layer (Layer E1) are typically present. The greatest biomass is observed near the surface during the night in Layer E1 and at depth between 250 and 450 m during the daytime in Layer D2. All layers are deepest during the spring inter-monsoon and shallowest during the summer/fall southwest monsoon (SWM). Seasonal modulation of the D2 biomass change is evident in our high-resolution data. The lowest biomass in D2 is measured in the early summer (May or June) followed by a rapid biomass increase during the SWM (June-November) until the biomass reaches a maximum at the end of the SWM season. Short-period oscillations in D2 biomass are often seen with periods ranging from days to one month. Occasionally, a lower nighttime layer E2 is formed between 180 and 270 m, mostly near the time of full moons. The upper daytime layer D1 is centered at 200 m and densely concentrated. It is only formed during the winter northeast monsoon (NEM) and the spring inter-monsoon. The influence of physical processes on layer distribution is also investigated. Interestingly, the two daytime layers are found to be formed at the two boundaries of the Persian Gulf outflow water (PGW) and follow the seasonal depth change of the PGW. The timing of the DVM and the formation, persistence, decay and reformation of the deep scattering layers seem to be governed by light, both solar and lunar. The scattering strength, the layer depth and the layer thickness are likewise closely related to the Moon phase at night. Cloud coverage, the isotherm and the isohaline also appear

  2. Retreived bacteria from Noctiluca miliaris (green) bloom of the northeastern Arabian Sea

    NASA Astrophysics Data System (ADS)

    Basu, Subhajit; Matondkar, S. G. Prabhu; Furtado, Irene

    2013-01-01

    In recent years, seasonal blooms of the dinoflagellate Noctiluca miliaris have appeared in the open-waters of the northern Arabian Sea (NAS). This study provides the first characterization of bacteria from a seasonal bloom of green Noctiluca of NAS (20°N-17°N and 64°E-70°E), during the spring-inter-monsoon cruise of Sagar Sampada 253, in March 2007. Bacterial growth as assessed by most-probable number (MPN) and plate counts, revealed `variable-physiotypes' over a wide range of salinities (0%-25% w/v NaCl), pH levels (5-8.5), and organic nutrient strengths, in comparison to non-bloom waters. MPN indices of bacteria in surface waters of bloom stations *DWK and *PRB, corresponded to (3.08-4.41)×103 cells/mL at 3.5% NaCl (w/v), and (2.82-9.49)×102 cells/mL at 25% (w/v) NaCl in tryptone-yeast extract broth (TYE). Plate counts were (1.12-4)×106 CFU/mL at 0% (w/v) NaCl, (1.28-3.9)×106 CFU/mL at 3.5% (w/v) NaCl, and (0.4-7)×104 CFU/mL at 25% NaCl (w/v) on TYE. One-tenth-strength Zobell's gave (0.6-3.74)×105 CFU/mL at pH 5 to (3.58-7.5)×105 CFU/mL at pH 8.5. These bacteria were identified to the genera Bacillus, Cellulomonas, Staphylococcus, Planococcus, Dietzia, Virgibacillus, Micrococcus, Sporosarcinae, Leucobacter, and Halomonas. The identity of three strains (GUFBSS253N2, GUFBSS253N30, and GUFBSS253N84) was confirmed through 16S rDNA sequence homology as Bacillus cohnii, Bacillus flexus, and Bacillus cereus. The ˜2-3-fold higher plate counts of culturable bacteria from the open-waters of the NAS indicate that these bacteria could critically determine the biogeochemical dynamics of the bloom and its milieu. The role of these bacteria in sustaining/terminating the bloom is under evaluation.

  3. Uptake of phytodetritus by benthic foraminifera under oxygen depletion at the Indian Margin (Arabian Sea)

    NASA Astrophysics Data System (ADS)

    Enge, A. J.; Witte, U.; Kucera, M.; Heinz, P.

    2013-09-01

    Benthic foraminifera in sediments on the Indian margin of the Arabian Sea where the oxygen minimum zone (OMZ) impinges on the continental slope are exposed to particularly severe levels of oxygen depletion. Food supply for the benthic community is high but delivered in distinct pulses during upwelling and water mixing events associated with summer and winter monsoon periods. In order to investigate the response by benthic foraminifera to such pulsed food delivery under oxygen concentrations of less than 0.1 mL L-1 (4.5 μmol L-1), an in situ isotope labeling experiment (13C, 15N) was performed at the western continental slope of India at 540 m water depth (OMZ core region). The assemblage of living foraminifera (>125 μm) in the uppermost centimeter at this depth is characterized by an unexpectedly high population density of 3982 ind. 10 cm-2 and a strong dominance by few calcareous species. For the experiment, we concentrated on the nine most abundant taxa, which constitute 93% of the entire foraminifera population at 0-1 cm sediment depth. Increased concentrations of 13C and 15N in the cytoplasm indicate that all investigated taxa took up the labeled phytodetritus during the 4 day experimental phase. In total, these nine species had assimilated 113.8 mg C m-2 (17.5% of the total added carbon). The uptake of nitrogen by the three most abundant taxa (Bolivina aff. B. dilatata, Cassidulina sp., Bulimina gibba) was 2.7 mg N m-2 (2% of the total added nitrogen) and showed the successful application of 15N as tracer in foraminiferal studies. The short-term response to the offered phytodetritus varied largely among foraminiferal species with Uvigerina schwageri being by far the most important species in short-term processing whereas the most abundant taxa Bolivina aff. B. dilatata and Cassidulina sp. showed comparably low uptake of the offered food. We suggest that the observed species-specific differences are related to individual biomass of species and to specific

  4. Uptake of phytodetritus by benthic foraminifera under oxygen depletion at the Indian margin (Arabian Sea)

    NASA Astrophysics Data System (ADS)

    Enge, A. J.; Witte, U.; Kucera, M.; Heinz, P.

    2014-04-01

    Benthic foraminifera in sediments on the Indian margin of the Arabian Sea, where the oxygen minimum zone (OMZ) impinges on the continental slope, are exposed to particularly severe levels of oxygen depletion. Food supply for the benthic community is high but delivered in distinct pulses during upwelling and water mixing events associated with summer and winter monsoon periods. In order to investigate the response by benthic foraminifera to such pulsed food delivery under oxygen concentrations of less than 0.1 mL L-1 (4.5 μmol L-1), an in situ isotope labeling experiment (13C, 15N) was performed on the western continental slope of India at 540 m water depth (OMZ core region). The assemblage of living foraminifera (>125 μm) in the uppermost centimeter at this depth is characterized by an unexpectedly high population density of 3982 individuals 10 cm-2 and a strong dominance by few calcareous species. For the experiment, we concentrated on the nine most abundant taxa, which constitute 93% of the entire foraminiferal population at 0-1 cm sediment depth. Increased concentrations of 13C and 15N in the cytoplasm indicate that all investigated taxa took up labeled phytodetritus during the 4 day experimental phase. In total, these nine species had assimilated 113.8 mg C m-2 (17.5% of the total added carbon). Uptake of nitrogen by the three most abundant taxa (Bolivina aff. B. dilatata, Cassidulina sp., Bulimina gibba) was 2.7 mg N m-2 (2% of the total added nitrogen). The response to the offered phytodetritus varied largely among foraminiferal species with Uvigerina schwageri being by far the most important species in short-term processing, whereas the most abundant taxa Bolivina aff. B. dilatata and Cassidulina sp. showed comparably low uptake of the offered food. We suggest the observed species-specific differences are related to species biomass and specific feeding preferences. In summary, the experiment in the OMZ core region shows rapid processing of fresh

  5. Acoustic Doppler current profiling from the JGOFS Arabian Sea cruises aboard the RV T.G. Thompson

    SciTech Connect

    Kim, H.S.; Flagg, C.N.; Shi, Y.

    1996-12-01

    Acoustic Doppler current profiler (ADCP) data is part of the core data for the US JGOFS Arabian Sea project, along with hydrographic and nutrient data. Seventeen cruises are scheduled to take place between September 1994 and January 1996 on the R/V T.G. Thompson. Seven of the cruises follow a standard cruise track, taking hydrographic, chemical and biological measurements. The rest of the cruises, which take place generally within the standard cruise region defined by a set track, are for the deployment and recovery of moored equipment and towing of a SeaSoar. Detailed description of ADCP hardware, the AutoADCP data acquisition system, and the collection of navigation and compass data on the Thompson is documented in Section 2. Followed by data collection for each cruise together with a cruise track, Section 3 presents the processing and analysis of velocity and acoustic backscatter intensity data. Section 5 shows results of profile quality diagnosis.

  6. Monsoon driven changes in phytoplankton populations in the eastern Arabian Sea as revealed by microscopy and HPLC pigment analysis

    NASA Astrophysics Data System (ADS)

    Parab, Sushma G.; Prabhu Matondkar, S. G.; Gomes, H. do R.; Goes, J. I.

    2006-12-01

    Like the rest of the Arabian Sea, the west coast of India is subject to semi-annual wind reversals associated with the monsoon cycle that result in two periods of elevated phytoplankton productivity, one during the northeast (NE) monsoon (November-February) and the other during the southwest (SW) monsoon (June-September). Although the seasonality of phytoplankton biomass in these coastal waters is well known, the abundance and composition of phytoplankton populations associated with this distinct and predictable seasonal cycle is poorly known. Here we present for the first time, the results of a study on the community structure of phytoplankton for this region, derived from HPLC pigment analysis and microscopic cell counts. Our sampling strategy allowed for large spatial and temporal coverage over regions representative of the coastal and offshore waters, and over seasons that included the NE and the SW monsoon. Monthly observations at a fixed coastal station in particular, allowed us to follow changes in phytoplankton community structure associated with the development of anoxia. Together these measurements helped establish a pattern of seasonal change of three major groups of phytoplankton: diatoms, dinoflagellates and cyanobacteria that appeared to be tightly coupled with hydrographic and chemical changes associated with the monsoonal cycle. During the SW monsoon when nitrate concentrations were high, diatoms were dominant but prymnesiophytes were present as well. By October, as nitrate fell to below detection levels and anoxic conditions began to develop on the shelf below the shallow pycnocline, both diatom and prymensiophytes declined sharply giving way to dinoflagellates. In the well oxygenated surface waters, where both nitrate and ammonium were below detection limits, pico-cyanobacterial populations became dominant. During the NE monsoon, a mixed diatom-dinoflagellate population was quickly replaced by blooms of Trichodesmium erythraeum and Noctiluca

  7. Sink or link? The bacterial role in benthic carbon cycling in the Arabian sea oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Pozzato, L.; Van Oevelen, D.; Moodley, L.; Soetaert, K.; Middelburg, J. J.

    2013-06-01

    The bacterial loop, the consumption of dissolved organic matter (DOM) by bacteria and subsequent transfer of bacterial carbon to higher trophic levels, plays a prominent role in pelagic aquatic food webs. However, its role in sedimentary ecosystems is not well documented. Here we present the results of isotope tracer experiments performed under in situ oxygen conditions in sediments from inside and outside the Arabian Sea Oxygen Minimum Zone (OMZ) to study the importance of the microbial loop in this setting. Particulate organic matter, added as phytodetritus, was processed by bacteria, protozoa and metazoans, while dissolved organic matter was processed only by bacteria and there was very little, if any, transfer to higher trophic levels within the experimental period. This lack of significant transfer of bacterial-derived carbon to metazoan consumers indicates that the bacterial loop is rather inefficient in these sediments. Moreover, metazoans directly consume labile particulate organic matter resources and thus compete with bacteria for phytodetritus.

  8. Biodegradation of diesel oil by an Arabian Sea sediment culture isolated from the vicinity of an oil field.

    PubMed

    Mukherji, Suparna; Jagadevan, Sheeja; Mohapatra, Gita; Vijay, Avinash

    2004-12-01

    Laboratory scale batch studies were performed to test the diesel oil biodegradation ability of ES1 cultures isolated from Arabian Sea sediments obtained from the vicinity of an oil field. This culture could utilize diesel as the sole source of carbon and energy. Under aerobic conditions, 39% loss of diesel oil was observed over 8 days where 80% of the loss was due to aliphatic constituents. Under anoxic nitrate reducing conditions the rate and extent of degradation was significantly lower, i.e., 18% over 50 days. Salt acclimatized cultures could tolerate salinities up to 3.5% and demonstrated optimal performance at a salinity of 0.5%. The optimum N/P ratio for these cultures was found to be in the range of 2:1-5:1. Addition of two trace elemental substance formulations exhibited a significant inhibitory effect on culture growth. This culture has good potential for decontamination of oil-contaminated marine and subsurface environments. PMID:15288270

  9. Trace metal enrichment and organic matter sources in the surface sediments of Arabian Sea along southwest India (Kerala coast).

    PubMed

    Sreekanth, Athira; Mrudulrag, S K; Cheriyan, Eldhose; Sujatha, C H

    2015-12-30

    The geochemical distribution and enrichment of trace metals (Cd, Co, Cu, Fe, Mn, Ni, Pb and Zn) were determined in the surface sediments of Arabian Sea, along southwest India, Kerala coast. The results of geochemical indices indicated that surficial sediments of five transects are uncontaminated with respect to Mn, Zn and Cu, uncontaminated to moderately contaminated with Co and Ni, and moderately to strongly contaminated with Pb. The deposition of trace elements exhibited three different patterns i) Cd and Zn enhanced with settling biodetritus from the upwelled waters, ii) Pb, Co and Ni show higher enrichment, evidenced by the association through adsorption of iron-manganese nodules onto clay minerals and iii) Cu enrichment observed close to major urban sectors, initiated by the precipitation as Cu sulfides. Correlation, principal component analysis (PCA) and cluster analysis (CA) were used to confirm the origin information of metals and the nature of organic matter composition. PMID:26602174

  10. Grazing processes and secondary production in the Arabian Sea: A simple food web synthesis with measurement constraints

    NASA Astrophysics Data System (ADS)

    Landry, Michael R.

    The Joint Global Ocean Flux Study in the Arabian Sea during the mid 1990s provides a rare opportunity to elucidate carbon flows in the lower food web of an open ocean ecosystem. Analysis of that data to date has, however, produced widely divergent perspectives on major flux pathways and roles of zooplankton: from zooplankton as controlling grazers tightly coupled to microbial processes to zooplankton as casual consumers who let a large fraction of production, mostly generated by picophytoplankton, flow directly to detritus and export. Synthesis of experimental grazing rates and production inferences for mesozooplankton and microzooplankton fit well in a conceptually simple food web, constrained by measured carbon flows through phytoplankton and bacteria. Microzooplankton dominate grazing processes, consuming over 70% of particulate primary production (PP), on average, and providing steady and significant supplemental nutrition to mesozooplankton. Direct grazing estimates of mesozooplankton, on the order of 25% of PP, are sufficient to balance the remaining particulate production, with additional transfer through a one- to two-step food chain of microzooplankton accounting for a total ingestion of ˜40% of PP required for mesozooplankton secondary production. Dissolved organic carbon fluxes to bacteria are provided mostly within the constraints of gross and net primary production. Contradictory results from inverse models are likely due to an assumption that exaggerates by approximately twofold the production contribution of picophytoplankton and to the failure to use measured rates of gross primary production as a system constraint. Grazing generally balances net particulate primary production in the Arabian Sea, but true grazer control of phytoplankton dynamics remains an open issue for further study.

  11. Live (Rose Bengal stained) foraminiferal faunas from the northern Arabian Sea: faunal succession within and below the OMZ

    NASA Astrophysics Data System (ADS)

    Caulle, Clemence; Koho, Karoliina; Mojtahid, Meryem; Reichart, Gert-Jan; Jorissen, Frans

    2014-05-01

    Live (Rose Bengal stained) benthic foraminifera from the Murray Ridge, within and below the northern Arabian Sea Oxygen Minimum Zone (OMZ), were studied in order to determine the relationship between faunal composition, bottom-water oxygenation (BWO), pore-water chemistry and organic matter (organic carbon and phytopigment) distribution. A series of multicores were recovered from a ten-station oxygen (BWO: 2µM - 78µM) and bathymetric (885 - 3010m depth) transect during the winter monsoon in January 2009. Foraminifera were investigated from three different size fractions (63-125µm, 125-150µm and >150µm). The larger foraminifera (>125µm) were strongly dominated by agglutinated species (e.g. Reophax spp.). In contrast, in the 63-125µm fraction, calcareous taxa were more abundant, especially in the core of the OMZ. On the basis of a Principal Components Analysis, three foraminiferal groups were identified and correlated to the environmental parameters by Canonical Correspondence Analysis. The faunas from the shallowest stations, in the core of the OMZ (BWO: 2µM), were composed of "low oxygen" species, typical of the Arabian Sea OMZ (e.g., Rotaliatinopsis semiinvoluta, Praeglobobulimina sp., Bulimina exilis, Uvigerina peregrina type parva). These taxa are adapted to the very low BWO conditions and to high phytodetritus supplies. The transitional group, typical for the lower part of the OMZ (BWO: 5-16µM), is composed of species, which are tolerant as well to low-oxygen concentrations, but may be less critical with respect to organic supplies (e.g. Globocassidulina subglobosa, Ehrenbergina trigona). Below the OMZ (BWO: 26-78µM), where food availability is more limited and becomes increasingly restricted to surficial sediments, cosmopolitan calcareous taxa were present, such as Bulimina aculeata, Melonis barleeanus, Uvigerina peregrina and Epistominella exigua. Miliolids were uniquely observed in this last zone, reflecting the higher BWO and/or lower organic

  12. Trace and rare earth elemental variation in Arabian sea sediments through a transect across the oxygen minimum zone

    SciTech Connect

    Nath, B.N.; Rao, B.R.; Rao, C.M.; Bau, M.

    1997-06-01

    We have determined the calcium carbonate (CaCO{sub 3}), organic carbon (C{sub org}), trace element, and rare earth element (REE) composition of surface sediments collected from a transect on the central western continental shelf and slope of India in the Eastern Arabian Sea. The transect samples across the oxygen minimum zone (OMZ) allows us to compare the relative abundances of trace elements and REEs in the sediments beneath and beyond the OMZ. Shale-normalized REE patterns, La{sub n}/Yb{sub n} ratios, and Eu/Eu* anamolies indicate that the sediments in the study area are either derived from the adjoining Archaean land masses or from distal Indus source. Sediment deposited in the OMZ have high U values from 3.6 to 8.1 ppm, with their U{sub excess} (of that can be supplied by continental particles) values ranging between 82-91% of the total U, indicating that the U may be precipitated as U{sup +4} in the reducing conditions of OMZ. Sediments deposited beneath the intense OMZ (<0.2 mL/L) and away from the OMZ (1-2 mL/L) show slight negative Ce anomalies, with no significant differences between these two sets of sediments. The Ce/Ce*{sub shale} values are poorly related to U and C{sub org} which are indicators of suboxic bottom waters. Normative calculations suggest that two sources, namely, terrestrial and seawater (terrestrial > seawater) contribute to the total Ce anomaly of the sediments. The Ce anomaly values of the calculated seawater derived component are similar to the anomalies reported for other coastal waters and the oxygenated surface waters of the Arabian Sea and do not show any correspondence to the lowered redox state of the overlying water, probably due to the redirection of dissolved Ce into the oxic deeper water. 103 refs., 6 figs., 3 tabs.

  13. High-resolution regional modeling of summertime transport and impact of African dust over the Red Sea and Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Kalenderski, Stoitchko; Stenchikov, Georgiy

    2016-06-01

    Severe dust outbreaks and high dust loading over Eastern Africa and the Red Sea are frequently detected in the summer season. Observations suggest that small-scale dynamic and orographic effects, from both the Arabian and African sides, strongly contribute to dust plume formation. To better understand these processes, we present here the first high-resolution modeling study of a dust outbreak in June 2012 developed over East Africa, the Red Sea, and the Arabian Peninsula. Using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) component, we identified several dust generating dynamical processes that range from convective to synoptic scales, including synoptic cyclones, nocturnal low-level jets, and cold pools of mesoscale convective systems. The simulations reveal an eastward transport of African dust across the Red Sea. Over the northern part of the Red Sea, most of the dust transport occurs above 2 km height, whereas across the central and southern parts of the sea; dust is mostly transported below 2 km height. Dust is the dominant contributor (87%) to the aerosol optical depth, producing a domain average cooling effect of -12.1 W m-2 at the surface, a warming of 7.1 W m-2 in the atmosphere, and a residual cooling of -4.9 W m-2 at the top of the atmosphere. Both dry and wet deposition processes contribute significantly to dust removal from the atmosphere. Model results compare well with available ground-based and satellite observations but generally underestimate the observed maximum values of aerosol optical depth. The satellite-retrieved mean optical depth at some locations is underestimated by a factor of 2. A sensitive experiment suggests that these large local differences may result from poor characterization of dust emissions in some areas of the modeled domain. In this case study we successfully simulate the major fine-scale dust generating dynamical processes, explicitly resolving convection and haboob formation. The future

  14. Monsoon variability in the northeastern Arabian Sea on orbital- and millennial scale during the past 200,000 years

    NASA Astrophysics Data System (ADS)

    Lückge, Andreas; Groeneveld, Jeroen; Steinke, Stephan; Mohtadi, Mahyar; Westerhold, Thomas; Schulz, Hartmut

    2016-04-01

    The Dansgaard-Oeschger oscillations and Heinrich events described in the Greenland ice cores and in North Atlantic and Western Mediterranean sediments are also expressed in the climate of the tropics, for example, as documented in Arabian Sea sediments. However, little is known about these fluctuations beyond the reach of the Greenland ice cores. Here, we present high-resolution geochemical, sedimentological as well as micropaleontological data from two cores (SO130-283KL, 987m water depth and SO130-289KL, 571m) off the coast of Pakistan, extending the monsoon record on orbital and millennial scales to the past 200,000 years. The stable oxygen isotope record of the surface-dwelling planktonic foraminifer G. ruber shows a strong correspondence to Greenland ice core δ18O, whereas the deepwater δ18O signal of benthic foraminifera (U. peregrina and G. affinis) reflects patterns recorded in ice cores from Antarctica. Strong shifts in benthic δ18O during stadials/Heinrich events are interpreted to show frequent advances of oxygen-rich intermediate water masses into the Arabian Sea originating from the southern ocean. Alkenone-derived SSTs varied between 23 and 28° C. Highest temperatures were encountered during interglacial MIS 5. Rapid SST changes of 2° C magnitude on millennial scale are overlain by long-term SST fluctuations. Interstadials (of glacial phases) and the cold phases of interglacials are characterized by sediments enriched in organic carbon (up to 4 % TOC) whereas sediments with low TOC contents (< 1 % TOC) appear during stadials and Heinrich events. Shifts at climate transitions, such as onsets of interstadials, were coeval with changes in productivity-related and anoxia-indicating proxies. Interstadial inorganic elemental data consistently show that enhanced fluxes of terrestrial-derived sediments are paralleled by productivity maxima, and are characterized by an increased fluvial contribution from the Indus River. In contrast, stadials are

  15. Impact of water mass mixing and dust deposition on Nd concentration and εNd of the Arabian Sea water column

    NASA Astrophysics Data System (ADS)

    Goswami, Vineet; Singh, Sunil K.; Bhushan, Ravi

    2014-11-01

    The concentration and isotopic composition (εNd) of dissolved Nd have been measured in the sub-oxic/denitrifying water column of the eastern Arabian Sea to explore the impact of water mass mixing and release from particles. Dissolved Nd in the north-eastern Arabian Sea is more radiogenic (εNd: -7 to -10) compared to its south-eastern part (εNd: -11 to -15) suggesting contribution of Nd from the Bay of Bengal (BoB). The vertical profile of Nd typically show higher values in surface waters (15.8-27.8 pmol/kg), followed by minima (12-18 pmol/kg) in the subsurface waters (200-300 m) and a gradual increase with depth thereafter. The Nd concentration does not seem to show any changes in the sub-oxic layers suggesting no impact of the sub-oxic/denitrifying conditions in this oceanic region on the biogeochemistry of Nd. The enrichment of Nd in surface waters can be explained either by supply from high Nd low salinity waters from the BoB to the Arabian Sea via the East India Coastal Current (EICC) or, alternatively the Nd surface excess can be result of release from aeolian dust depositing over the sea surface. Inverse modeling computations suggest that in addition to Nd contributed from water mass mixing, some additional excess Nd (Ndxs) is required to balance the Nd inventory in the water column. There is significant Ndxs in the surface waters of the north-eastern Arabian Sea with εNd ∼ -6, similar to that of dust depositing over the Arabian Sea. The fractional solubility of Nd released from the aeolian dust was estimated to be varying from ∼3% to 17% (for excess Nd inventory per unit area (Ndxs∗) of 20 μg m-2 with τNd ranging from 1 to 3 years). This study highlights the significance of aeolian dust deposition in controlling the abundance and distribution of Nd in the Arabian Sea, the western arm of the northern Indian Ocean, lying in the proximity to the arid landmass and characterized by high lithogenic aeolian dust deposition.

  16. Analysis of humpback whale sounds in shallow waters of the Southeastern Arabian Sea: An indication of breeding habitat.

    PubMed

    Mahanty, Madan M; Latha, G; Thirunavukkarasu, A

    2015-06-01

    The primary objective of this work was to present the acoustical identification of humpback whales, detected by using an autonomous ambient noise measurement system, deployed in the shallow waters of the Southeastern Arabian Sea (SEAS) during the period January to May 2011. Seven types of sounds were detected. These were characteristically upsweeps and downsweeps along with harmonics. Sounds produced repeatedly in a specific pattern were referred to as phrases (PQRS and ABC). Repeated phrases in a particular pattern were referred to as themes, and from the spectrographic analysis, two themes (I and II) were identified. The variation in the acoustic characteristics such as fundamental frequency, range, duration of the sound unit, and the structure of the phrases and themes are discussed. Sound units were recorded from mid-January to mid-March, with a peak in February, when the mean SST is approx. 28 degree C, and no presence was recorded after mid-March. The temporal and thematic structures strongly determine the functions of the humpback whale song form. Given the use of song in the SEAS, this area is possibly used as an active breeding habitat by humpback whales during the winter season. PMID:25963267

  17. Feeding ecology of the copepod Lucicutia aff. L. grandis near the lower interface of the Arabian Sea oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Gowing, Marcia M.; Wishner, Karen F.

    Feeding ecology of the calanoid copepod Lucicutia aff. L. grandis collected in the Arabian Sea at one station during the Spring Intermonsoon and during the Southwest Monsoon of 1995 was studied with transmission electron microscopy of gut-contents. Highest abundances of these animals occurred from ˜400 to 1100 m, near the lower interface of the oxygen minimum zone and at the inflection point where oxygen starts to increase. We expected that their gut-contents would include particles and cells that had sunk relatively undegraded from surface waters as well as those from within the oxygen minimum zone, and that gut-contents would differ between the Spring Intermonsoon and the more productive SW Monsoon. Overall, in both seasons Lucicutia aff. L. grandis was omnivorous, and consumed a variety of detrital particles, prokaryotic and eukaryotic autotrophs, gram-negative bacteria including metal-precipitating bacteria, aggregates of probable gram-positive bacteria, microheterotrophs, virus-like particles and large virus-like particles, as well as cuticle and cnidarian tissue. Few significant differences in types of food consumed were seen among life stages within or among various depth zones. Amorphous, unidentifiable material was significantly more abundant in guts during the Spring Intermonsoon than during the late SW Monsoon, and recognizable cells made up a significantly higher portion of gut-contents during the late SW Monsoon. This is consistent with the Intermonsoon as a time when organic material is considerably re-worked by the surface water microbial loop before leaving the euphotic zone. In both seasons Lucicutia aff. L. grandis had consumed what appeared to be aggregates of probable gram-positive bacteria, similar to those we had previously found in gut-contents of several species of zooplankton from the oxygen minimum zone in the eastern tropical Pacific. By intercepting sinking material, populations of Lucicutia aff. L. grandis act as a filter for carbon

  18. Living (Rose-Bengal-stained) benthic foraminiferal faunas along a strong bottom-water oxygen gradient on the Indian margin (Arabian Sea)

    NASA Astrophysics Data System (ADS)

    Caulle, C.; Mojtahid, M.; Gooday, A. J.; Jorissen, F. J.; Kitazato, H.

    2015-08-01

    Rose-Bengal-stained foraminiferal assemblages (> 150 μm) were analysed along a five-station bathymetric transect across the core and the lower part of the oxygen minimum zone (OMZ) on the Indian margin of the Arabian Sea. Sediment cores were collected using the manned submersible Shinkai 6500 during the RV Yokosuka cruise YK08-11 in the post-monsoon season (October 2008) at water depths ranging from 535 to 2000 m, along a gradient from almost anoxic to well-oxygenated (0.3 to 108 μM) bottom waters. Stained benthic foraminifera were investigated from two different size fractions (150-300 μm and > 300 μm). Stained foraminiferal densities were very high in the core of the OMZ (at 535 and 649 m) and decreased at deeper sites. The faunas (> 150 μm) were dominated (40-80 %) by non-calcareous taxa at all stations. These were mainly species of Reophax and Lagenammina but also included delicate monothalamous taxa (organic-walled "allogromiids", agglutinated saccamminids, psammosphaerids and tubular forms). These new data from the Indian margin are compared to previous studies from the Murray Ridge, the Pakistan margin and the Oman margin. The fact that similar species were found at sites with comparable bottom-water oxygen concentrations but with very different surface water productivity suggests that, within the strongly developed Arabian Sea OMZ, bottom-water oxygen concentration, and not the organic flux to the sea floor, is the main factor controlling the species composition of the foraminiferal communities. Several foraminiferal species (e.g. Praeglobobulimina sp. 1, Ammodiscus sp. 1, Bolivina aff. dilatata) were confined to the core of the OMZ. These species are presently known only from the Arabian Sea. Because of their association with extremely low oxygen concentrations, these species may be good markers for very low oxygen concentrations, and could be used to reconstruct past OMZ variability in the Arabian Sea.

  19. Living (Rose Bengal stained) benthic foraminiferal faunas along a strong bottom-water oxygen gradient on the Indian margin (Arabian Sea)

    NASA Astrophysics Data System (ADS)

    Caulle, C.; Mojtahid, M.; Gooday, A. J.; Jorissen, F. J.; Kitazato, H.

    2015-02-01

    Rose Bengal stained foraminiferal assemblages were analysed along a five-station bathymetric transect across the core and the lower part of the oxygen minimum zone (OMZ) on the Indian margin of the Arabian Sea. Sediment cores were collected using the manned submersible Shinkai 6500 during RV Yokosuka cruise YK08-11 in the post-monsoon season (October 2008) at water depths ranging from 535 to 2000 m, along a gradient from almost anoxic to well-oxygenated (0.3 to 108 μM) bottom waters. Stained foraminiferal densities were very high in the OMZ core (535 m) and decreased with depth. The faunas were dominated (40-80%) by non-calcareous taxa at all stations. These were mainly species of Reophax and Lagenammina but also included delicate monothalamous taxa (organic-walled "allogromiids", agglutinated saccamminids, psammosphaerids and tubular forms). These new data from the Indian margin are compared to previous studies from the Murray Ridge, the Pakistan margin and the Oman margin. The fact that similar species were found at sites with comparable bottom-water oxygen concentrations but with very different surface water productivity suggests that, within the strongly developed Arabian Sea OMZ, bottom-water oxygen concentration, and not the organic flux to the sea floor, is the main factor controlling the species composition of the foraminiferal communities. Several foraminiferal species (e.g. Praeglobobulimina sp. 1, Ammodiscus sp. 1, Bolivina aff. dilatata) were confined to the core of the OMZ and are presently known only from the Arabian Sea. Because of their association with extremely low-oxygen concentration, these species may prove to be good indicators of past OMZ variability in the Arabian Sea.

  20. Present-Day Kinematics of the Dead Sea Transform and Internal Deformation within the Sinai and Arabian Plates

    NASA Astrophysics Data System (ADS)

    Gomez, F. G.; Yassminh, R.; Cochran, W. J.; Reilinger, R. E.; Barazangi, M.

    2015-12-01

    An updated GPS velocity field along the Dead Sea Fault (DSF) provides a basis for assessing off-transform strain within the Sinai and Arabian plates along entire length of this left-lateral, continental transform. As one of the main tectonic elements in the eastern Mediterranean region, an improved kinematic view of the DSF elucidates the broader understanding of the regional tectonic framework, as well as contributes to refining the earthquake hazard assessment. Reconciling short-term (geodetic) measurements of crustal strain with neotectonic data on fault movements can yield insight into the mechanical and rheological properties of crustal deformation associated with transform tectonics. In addition to regional continuous GPS stations, this study assembles results from campaign GPS networks in Syria, Lebanon, and Jordan spanning more than a decade. 1-sigma uncertainties on velocities range from less than 0.4 mm/yr (continuous stations and older GPS survey sites) to about 1.0 mm/yr (newer survey sites). Analyses using elastic block models suggest slip rates of 4.0 - 5.0 mm/yr along the southern and central DSF and slip rates of 2.0 - 3.0 mm/yr along the northern DSF, and fault locking depths also vary along strike of the transform. Furthermore, the spatial distribution of GPS observations permits analyzing residual strains within the adjacent plates, after plate boundary strain is removed. A key observation is horizontal stretching within the Sinai plate, which may be related to pull by the subducted slab of the Sinai plate. Within the Arabian plate, areas of horizontal stretching generally correlate with locations of Quaternary volcanism.

  1. A Study of Tropical Cyclones over India (Bay of Bengal and Arabian Sea) and Solar Influence on It

    NASA Astrophysics Data System (ADS)

    Banerjee, Dhruba

    2016-07-01

    A prominent example of extreme weather event in India is Cyclonic Storm. In this paper annual variation of tropical Cyclonic Storm (CS), Severe Cyclonic Storm (SCS), Very Severe Cyclonic Storm (VSCS) and Super Cyclonic Storm (SuCS) over Bay Of Bengal (BOB) and Arabian Sea (ARS) during last 20 years (1990-2009) have been analyzed .The analysis revels that the total number of cyclone (TNC) has increased with high rate(gradient being +1.67 per year) and although C.S. is more over BOB than that over ARS.The rate of increase of C.S. over Arabian Sea is more than that over Bay of Bengal. Furthermore, two interesting features have been noted: (i) Monsoon tends to prohibit the formation of C.S (ii) Cyclonic Storm(C.S.) increases with the increase of Global Sea Surface Temperature (GSST) during said period.. Attempt has also been made to find out the influence of solar activity on these extreme weather events. Keeping in mind that the Sun Spot Number (SSN) is an indicator of the strength of solar effects, it has been found that in most of the times the high value of SSN is associated with small number of total cyclone (C.S.). Specifically, when only the years of high Sun's Spot Number (approximately greater than 90) are taken into consideration then Correlation Coefficient (C.C.) between SSN and number of cyclones comes out to be quite high (-0.78) significance at 99.99% level while Correlation Coefficient (C.C.) of cyclones with time is 0.53 and with SSN < 60 it is..095 . Thus it appears that although C.S. frequency is increasing with time, Sun's Spot's influence is such that it basically opposes the formation of cyclone provided SSN exceeds certain critical value (roughly 90). In principle, this is very important for any such event, and it is consistent with the trend of different phenomena occurring in nature. Key words: India, cyclone, solar influence, Critical Sun's Spot Number

  2. Passive Acoustic Recognition of Fishing Vessel Activity in the Shallow Waters of the Arabian Sea: A Statistical Approach

    NASA Astrophysics Data System (ADS)

    Kannan, R.; Sanjana, M. C.; Latha, G.

    2015-09-01

    The ambient noise system consisting of a vertical linear hydrophone array (VLA) with 12 elements was deployed in the waters of the Arabian Sea at a depth of 16m, off Goa, India, for extracting the ambient noise during the fishing season (March, April and May, 2013 before the onset of the south west monsoon). This study focuses on fishing vessel activity by finding the domination of the vessel and wind noise at two 12 hourly periodic cycles that start at midnight and noon, using the statistical analysis. It is performed using statistical parameters, like the mean, median, and standard deviation, skewness, percentile and spread of data. It is observed that the vessel noise dominates during the 12h period that starts at midnight and is an indication of the activity of fishing vessels while the wind generated noise is more during the 12h period that starts at noon, which is a sign of the domination of the sea breeze effects. This is the first time that a statistical analysis has been carried out to study the ambient noise data collected off Goa, in order to find the fishing vessel activity during the pre-monsoon season. The results are verified with the fishing information from the Directorate of Fisheries, Goa, ship traffic data from the Mormugao Port Trust and wind speed measurements.

  3. The Owen Ridge uplift in the Arabian Sea: Implications for the sedimentary record of Indian monsoon in Late Miocene

    NASA Astrophysics Data System (ADS)

    Rodriguez, Mathieu; Chamot-Rooke, Nicolas; Huchon, Philippe; Fournier, Marc; Delescluse, Matthias

    2014-05-01

    The pelagic cover of the Owen Ridge in the Arabian Sea recorded the evolution of the Indian monsoon since the Middle Miocene. The uplift of the Owen Ridge resulted from tectonic processes along the previously unidentified Miocene India-Arabia plate boundary. Based on seismic reflection data tied with deep-sea drilling to track the Miocene India-Arabia plate boundary, we propose a new timing for the uplift of the Owen Ridge and highlight its impact on the record of climate changes in pelagic sediments. The new dataset reveals a fracture zone east of the Owen Ridge corresponding to the fossil plate boundary, and documents that the main uplift of the Owen Ridge occurred close to ˜8.5 Ma, and is coeval with a major uplift of the east Oman margin. Late Miocene deformation at the India-Arabia plate boundary is also coeval with the onset of intra-plate deformation in the Central Indian Ocean, suggesting a kinematic change of India and surrounding plates in the Late Miocene. The uplift of the Owen Ridge above the lysocline at ˜8.5 Ma accounts for a better preservation of Globigerina bulloides in the pelagic cover, previously misinterpreted as the result of a monsoon intensification event.

  4. Acoustic Doppler current profiling from the JGOFS Arabian sea cruises aboard the RV T.G. Thompson

    SciTech Connect

    Kim, Hyun-Sook; Flagg, C.N.; Shi, Yan

    1996-06-01

    Acoustic Doppler current profiler (ADCP) data is part of the core data for the U.S. JGOFS Arabian Sea project, along with hydrographic and nutrient data. Seventeen cruises are scheduled to take place between September 1994 and January 1996 on the R/V T.G. Thompson. They are numbered consecutively from the ship`s commissioning with the first JGOFS cruise designated TN039. Table 1 lists start and end dates of each cruise with its mission. All but the first cruise have been or will be staged from Muscat, Oman. Each cruise is scheduled for a duration of between two weeks and one month. Seven of the cruises, referred to as process cruises, follow a standard cruise track, taking hydrographic, chemical and biological measurements. The rest of the cruises, which take place generally within the standard cruise region defined by a set track, are for the deployment and recovery of moored equipments and towing of a SeaSoar. ADCP data are collected using an autonomous data acquisition system developed for ship-of-opportunity cruises, named the AutoADCP system. The system is an extension of RD instrument`s DAS version 2.48 using enhancements made possible with {open_quotes}user-exit{close_quotes} programs. It makes it possible to collect ADCP data without the constant monitoring usually necessary and insures constant data coverage and uniform data quality.

  5. 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.

  6. Speciation of phosphorus in the continental shelf sediments in the Eastern Arabian Sea

    NASA Astrophysics Data System (ADS)

    Acharya, Shiba Shankar; Panigrahi, Mruganka Kumar; Kurian, John; Gupta, Anil Kumar; Tripathy, Subhasish

    2016-03-01

    The distributions of various forms of phosphorus (P) and their relation with sediment geochemistry in two core sediments near Karwar and Mangalore offshore have been studied through the modified SEDEX procedure (Ruttenberg et al., 2009) and bulk chemical analysis. The present study provides the first quantitative analysis of complete phosphorus speciation in the core sediments of the Eastern Arabian shelf. The chemical index of alteration (CIA), chemical Index of Weathering (CIW) and Al-Ti-Zr ternary diagram suggest low to moderate source area weathering of granodioritic to tonalitic source rock composition, despite the intense orographic rainfall in the source area. Due to the presence of same source rock and identical oxic depositional environment, the studied sediments show the same range of variation of total phosphorus (24 to 83 μmol/g) with a down-depth depleting trend. Organic bound P and detrital P are the two major chemical forms followed by iron-bound P, exchangeable/loosely bound P and authigenic P. The authigenic P content in the sediments near Mangalore coast varies linearly with calcium (r=0.88) unlike that of Karwar coast. The different reactive-phosphorus pools exhibit identical depleting trend with depth. This indicates that the phosphorus released from the organic matter and Fe bound fractions are prevented from precipitating as authigenic phosphates in the deeper parts of the sediment column. The low concentration of total P, dominance of detrital non-reactive fraction of P and inhibition of formation of authigenic phosphate result in the absence of active phosphatization in the Eastern Arabian Shelf in the studied region. High sedimentation rate (35-58 cm/kyr) and absence of winnowing effect appear to be the dominant factor controlling the P-speciation in the studied sediments.

  7. Oxygen minimum zone of the open Arabian Sea: variability of oxygen and nitrite from daily to decadal time scales

    NASA Astrophysics Data System (ADS)

    Banse, K.; Naqvi, S. W. A.; Narvekar, P. V.; Postel, J. R.; Jayakumar, D. A.

    2013-09-01

    The oxygen minimum zone (OMZ) of the Arabian Sea is the thickest of the three oceanic OMZs, which is of global biogeochemical significance because of denitrification in the upper part leading to N2 and N2O production. The residence time of the OMZ water is believed to be less than a decade. The upper few hundred meters of this zone are nearly anoxic but non-sulfidic and still support animal (metazoan) pelagic life, possibly as a result of episodic injections of O2 by physical processes. The very low O2 values obtained with the new STOX sensor in the eastern tropical South Pacific probably also characterize the Arabian Sea OMZ, but there is no apparent reason as to why the temporal trends of the historic data should not hold. We report on discrete measurements of dissolved O2 and NO2-, besides temperature and salinity, made between 1959 and 2004 well below the tops of the sharp pycno- and oxyclines near 150, 200, 300, 400, and 500 m depth. We assemble nearly all O2 determinations (originally, 849 values, 695 in the OMZ) by the visual endpoint detection of the iodometric Winkler procedure, which in our data base yields about 0.04 mL L-1 (∼2 μM) O2 above the endpoint from modern automated titration methods. We find 632 values acceptable (480 from 150 stations in the OMZ). The data are grouped in zonally-paired boxes of 1° lat. and 2° long. centered at 8°, 10°, 12°, 15°, 18°, 20°, and 21° N along 65° E and 67° E. The latitudes of 8-12° N, outside the OMZ, are only treated in passing. The principal results are as follows: (1) an O2 climatology for the upper OMZ reveals a marked seasonality at 200 to 500 m depth with O2 levels during the northeast monsoon and spring intermonsoon season elevated over those during the southwest monsoon season (median difference, 0.08 mL L-1 [3.5 μM]). The medians of the slopes of the seasonal regressions of O2 on year for the NE and SW monsoon seasons are -0.0043 and -0.0019 mL L-1 a-1, respectively (-0.19 and -0.08 μM a

  8. Mulloidichthys flavolineatus flavicaudus Fernandez-Silva & Randall (Perciformes, Mullidae), a new subspecies of goatfish from the Red Sea and Arabian Sea.

    PubMed

    Fernandez-Silva, Iria; Randall, John E; Golani, Daniel; Bogorodsky, Sergey V

    2016-01-01

    The number of goatfish species has increased recently, thanks in part to the application of molecular approaches to the taxonomy of a family with conservative morphology and widespread intraspecific color variation. A new subspecies Mulloidichthys flavolineatus flavicaudus Fernandez-Silva & Randall is described from the Red Sea and Arabian Sea, including Socotra and Gulf of Oman. It is characterized by a yellow caudal fin, 25-28 gill rakers, and 37-38 lateral-line scales and it is differentiated from nominal subspecies Mulloidichthys flavolineatus flavolineatus by 1.7% sequence divergence at the mitochondrial cytochrome b gene. The morphometric examination of specimens of Mulloidichthys flavolineatus flavolineatus revealed variation in head length, eye diameter, and barbel length, in western direction from the Hawaiian Islands, South Pacific, Micronesia, and the East Indies to the Indian Ocean. The population of Mulloidichthys flavolineatus flavicaudus subsp. n. in the Gulf of Aqaba differs from that of the remaining Red Sea by shorter barbels, smaller eyes, shorter head, and shorter pelvic fins. We present a list of 26 endemic fishes from the Gulf of Aqaba and discuss the probable basis for the endemism in the light of the geological history of this region. PMID:27551217

  9. Mulloidichthys flavolineatus flavicaudus Fernandez-Silva & Randall (Perciformes, Mullidae), a new subspecies of goatfish from the Red Sea and Arabian Sea

    PubMed Central

    Fernandez-Silva, Iria; Randall, John E.; Golani, Daniel; Bogorodsky, Sergey V.

    2016-01-01

    Abstract The number of goatfish species has increased recently, thanks in part to the application of molecular approaches to the taxonomy of a family with conservative morphology and widespread intraspecific color variation. A new subspecies Mulloidichthys flavolineatus flavicaudus Fernandez-Silva & Randall is described from the Red Sea and Arabian Sea, including Socotra and Gulf of Oman. It is characterized by a yellow caudal fin, 25–28 gill rakers, and 37–38 lateral-line scales and it is differentiated from nominal subspecies Mulloidichthys flavolineatus flavolineatus by 1.7% sequence divergence at the mitochondrial cytochrome b gene. The morphometric examination of specimens of Mulloidichthys flavolineatus flavolineatus revealed variation in head length, eye diameter, and barbel length, in western direction from the Hawaiian Islands, South Pacific, Micronesia, and the East Indies to the Indian Ocean. The population of Mulloidichthys flavolineatus flavicaudus subsp. n. in the Gulf of Aqaba differs from that of the remaining Red Sea by shorter barbels, smaller eyes, shorter head, and shorter pelvic fins. We present a list of 26 endemic fishes from the Gulf of Aqaba and discuss the probable basis for the endemism in the light of the geological history of this region. PMID:27551217

  10. How a seven-year ocean observatory is influencing our understanding of physical and biological processes in northern Arabian Sea?

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Dimarco, S. F.; Al-Kharusi, L. H.; Belabbassi, L.; Ingle, S.

    2012-12-01

    An ocean observatory—consisting of a real-time, cabled system in the Sea of Oman and an internally-recording, autonomous mooring system recently upgraded to a cabled system in the northern Arabian Sea—was installed in 2005. The two arrays have collected a continuous seven-year time series record of current velocities, temperature, pressure, salinity, dissolved oxygen, and turbidity in a region where several water masses converge and subsequently spread southward to the Indian Ocean. The systems have provided new insights into physical and biological oceanographic processes of the northwestern Indian Ocean, which is strongly affected by the monsoonal oscillation, along with lessons learned and best practices in the operation and application of ocean observatories to ocean science. In this presentation, we show four recent studies for the scientific highlights derived from the data collected from the two systems and supporting data from other sources. The topics of those four studies include: (1) The seasonality associated with the upwelling of low oxygen water on the northern Oman coast and insights on the inter-annual variability of this process; (2) The deep-water oceanic responses excited by the passage of Cyclone Gonu, the largest-ever recorded cyclone in the region; (3) The temporal and spatial evolution of an acoustic backscatter layer; (4) The pulse-like salinity/temperature events in the northeastern Arabian Sea and Gulf of Oman. In summary, the observatory provides a long-term time series with which to perform basic scientific research related to characterizing the general dynamical patterns of the region, quantifying seasonal variability of water column properties, and establishing a time series of sufficient duration to deduce the potential impacts of climate change. Furthermore, observations taken over the full, 20+ year lifetime of a typical cabled system will be extremely useful for evaluating numerical ocean circulation and coupled atmospheric

  11. Live (Rose Bengal stained) foraminiferal faunas from the northern Arabian Sea: faunal succession within and below the OMZ

    NASA Astrophysics Data System (ADS)

    Caulle, C.; Koho, K. A.; Mojtahid, M.; Reichart, G. J.; Jorissen, F. J.

    2014-02-01

    Live (Rose Bengal stained) benthic foraminifera from the Murray Ridge, within and below the northern Arabian Sea oxygen minimum zone (OMZ), were studied in order to determine the relationship between faunal composition, bottom water oxygenation (BWO), pore water chemistry and organic matter (organic carbon and phytopigment) distribution. A series of multicores were recovered from a ten-station oxygen (BWO: 2-78 μM) and bathymetric (885-3010 m depth) transect during the winter monsoon in January 2009. Foraminifera were investigated from three different size fractions (63-125 μm, 125-150 μm and >150 μm). The larger foraminifera (>125 μm) were strongly dominated by agglutinated species (e.g. Reophax spp.). In contrast, in the 63-125 μm fraction, calcareous taxa were more abundant, especially in the core of the OMZ. On the basis of a principal components analysis, three foraminiferal groups were identified and correlated to the environmental parameters by canonical correspondence analysis. The faunas from the shallowest stations, in the core of the OMZ (BWO: 2 μM), were composed of "low oxygen" species, typical of the Arabian Sea OMZ (e.g. Rotaliatinopsis semiinvoluta, Praeglobobulimina sp., Bulimina exilis, Uvigerina peregrina type parva). These taxa are adapted to the very low BWO conditions and to high phytodetritus supplies. The transitional group, typical for the lower part of the OMZ (BWO: 5-16 μM), is composed of species that are tolerant as well to low-oxygen concentrations, but may be less critical with respect to organic supplies (e.g. Globocassidulina subglobosa, Ehrenbergina trigona). Below the OMZ (BWO: 26-78 μM), where food availability is more limited and becomes increasingly restricted to surficial sediments, cosmopolitan calcareous taxa were present, such as Bulimina aculeata, Melonis barleeanus, Uvigerina peregrina and Epistominella exigua. Miliolids were uniquely observed in this last zone, reflecting the higher BWO and/or lower organic

  12. Live foraminiferal faunas (Rose Bengal stained) from the northern Arabian Sea: links with bottom-water oxygenation

    NASA Astrophysics Data System (ADS)

    Caulle, C.; Koho, K. A.; Mojtahid, M.; Reichart, G. J.; Jorissen, F. J.

    2013-09-01

    Live (Rose Bengal stained) benthic foraminifera from the Murray Ridge, within and below the northern Arabian Sea Oxygen Minimum Zone (OMZ), were studied in order to determine the relationship between faunal composition, bottom-water oxygenation (BWO), pore-water chemistry and organic matter (organic carbon and phytopigment) distribution. A series of multicores were recovered from a ten-station oxygen (BWO: 2-78 μM) and bathymetric (885-3010 m depth) transect during the winter monsoon in January 2009. Foraminifera were investigated from three different size fractions (63-125 μm, 125-150 μm and > 150 μm). The larger foraminifera (> 125 μm) were strongly dominated by agglutinated species (e.g. Reophax spp.). In contrast, in the 63-125 μm fraction, calcareous taxa were more abundant, especially in the core of the OMZ, suggesting an opportunistic behaviour. On the basis of a Principal Component Analysis, three foraminiferal groups were identified, reflecting the environmental parameters along the study transect. The faunas from the shallowest stations, in the core of the OMZ (BWO: 2 μM), were composed of "low oxygen" species, typical of the Arabian Sea OMZ (e.g., Rotaliatinopsis semiinvoluta, Praeglobobulimina spp. , Bulimina exilis, Uvigerina peregrina typeparva). These taxa are adapted to the very low BWO conditions and to high phytodetritus supplies. The transitional group, typical for the lower part of the OMZ (BWO: 5-16 μM), is composed of more cosmopolitan taxa tolerant to low-oxygen concentrations (Globocassidulina subglobosa, Ehrenbergina trigona). Below the OMZ (BWO: 26-78 μM), where food availability is more limited and becomes increasingly restricted to surficial sediments, more cosmopolitan calcareous taxa were present, such as Bulimina aculeata, Melonis barleeanus, Uvigerina peregrina and Epistominella exigua. Miliolids were uniquely observed in this last group, reflecting the higher BWO. At these deeper sites, the faunas exhibit a clear depth

  13. Mechanisms and Effects of Summertime Transport of African Dust Through the Tokar Mountain Gap to the Red Sea and Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Kalenderski, S.; Stenchikov, G. L.

    2015-12-01

    Very high dust loading over the Red Sea region in summer strongly affects the nutrition balance and thermal and dynamic regimes of the sea. The observations suggest that small-scale local dynamic and orographic effects, from both the Arabian and African sides, strongly contribute to dust plume formation. To better understand and quantify these processes we present here the first high resolution modeling study of the dust outbreak phenomena in June 2012 over East Africa, the Red Sea, and the Arabian Peninsula using the WRF-Chem model. We identified several dust generating dynamical processes that range from convective to synoptic scales, including: synoptic cyclones, nocturnal low-level jets, and cold pools of mesoscale convective systems. The simulations reveal an eastward transport of African dust across the Red Sea. Over the northern part of the Red Sea most of the dust transport occurs beyond 2 km above ground level and is strengthened by a pressure gradient formed by low pressure over the eastern Mediterranean and high pressure over the Arabian Peninsula. Across the central and southern parts of the Red Sea dust is mostly transported below 2 km height. During the study period dust is a dominant contributor (87%) to aerosol optical depth (AOD), producing a domain average cooling effect of -12.1 W m-2 at surface, a warming of 7.1 W m-2 in the atmosphere, and a residual cooling of -4.9 W m-2 at the top of the atmosphere. WRF-Chem simulations demonstrate that both dry and wet deposition processes contribute significantly to dust removal from the atmosphere. During the dust outbreak 49.2 Tg of dust deposits within the calculation domain, which is approximately 90% of the total dust emission of 54.5 Tg. Model results compare well with available ground-based and satellite observations but generally underestimate the observed AOD maximum values.

  14. Decadal- to biennial scale variability of planktic foraminifera in the northeastern Arabian Sea during the last two millennia: evidence for winter monsoon forcing mechanisms

    NASA Astrophysics Data System (ADS)

    Munz, Philipp; Lückge, Andreas; Siccha, Michael; Kucera, Michal; Schulz, Hartmut

    2015-04-01

    The Asian monsoon system is controlling the hydrologic cycle, and thus the agricultural and economic prosperity of the worlds most densely populated region. Strong and moisture-laden winds from the southwest induce upwelling and significant productivity in the western Arabian Sea during boreal summer. During boreal winter, weaker dry and cold surface winds from the northeast nourish ocean productivity mainly in the northeastern Arabian Sea. Instrumental records spanning the last century are too short to understand how the monsoon system reacts to external forcing mechanisms and to accurately determine its natural variability. Compared to the summer monsoon component, the dynamics of the winter monsoon are virtually unknown, due to the lack of adequate archives that are affected only by winter conditions. Here we present a decadal- to biennial-scale resolution record of past winter monsoon variability over the last two millennia, based on census counts of planktic foraminifera from two laminated sediment cores collected offshore Pakistan. One shorter box core (SO90-39KG) spans the last 250 years with an average ~2-year resolution, whereas the longer piston core (SO130-275KL) spans the last 2,100 years with a 10-year resolution. We use Globigerina falconensis as a faunal indicator for winter conditions, a species that is most abundant during winter in the NE Arabian Sea (Peeters and Brummer, 2002; Schulz et al., 2002). Our results show that during the past 2,100 years G. falconensis varied with significant periodicities centered on ˜ 60, ˜ 53, ˜ 40, ˜ 34 and ˜ 29 years per cycle. Some of these periods closely match cycles that are known from proxy records of solar irradiance, suggesting a solar forcing on winter monsoon variability. During the past 250 years G. falconensis varied in correlation with the (11-year) Schwabe and the (22-year) Hale solar cycles. Furthermore, a significant ˜ 7 year cyclicity could indicate a teleconnection to the El Niño Southern

  15. Millennial/centennial-scale thermocline ventilation changes in the Indian Ocean as reflected by aragonite preservation and geochemical variations in Arabian Sea sediments

    NASA Astrophysics Data System (ADS)

    Böning, Philipp; Bard, Edouard

    2009-11-01

    The formation and temporal variability of the oxygen minimum zone (OMZ) of the Arabian Sea is a subject of intense research. We contribute to the discussion by studying modern seawater profiles of the Indian Ocean (salinity, O 2, pH, aragonite saturation, nitrate deficit, nutrients), which show that Subantarctic Mode and Antarctic Intermediate Waters (SAMW-AAIW) have a strong influence on the OMZ characteristics of the Arabian Sea. To obtain a better grasp of the range of possible OMZ variations, we studied a 50-kyr record in the NE Arabian Sea (core MD042876) from a site at 828 m water depth within the thermocline. In this core, aragonite is preserved during North Atlantic Heinrich events (HEs) and Dansgaard-Oeschger (DO) stadials, while it is absent during DO interstadials and most of the Holocene. Considering the excellent correlation between aragonite content and Sr/Ca ratio, as well as the presence of fine-grained aragonitic needles and the isotopic composition (δ 13C) of carbonates in the fine fraction, we infer that essentially all aragonite originates as fine Sr-rich debris from shallow water. A comparison with other records from the NE Arabian Sea (Sr/Ca, δ 15N) indicates that aragonite variability in the cores is rather controlled by OMZ intensity variations as forcing mechanism while changes in aragonite supply seem to play a minor role. The strong correlation of aragonite content with changes in millennial-scale ventilation of the Indian Ocean, as well as a comparison with modern oceanographic conditions, supports the theory that OMZ intensity variations are controlled by changes in the formation of SAMW-AAIW, and are not only due to monsoonal changes. Thus, during HEs and DO stadials, the thermocline Arabian Sea experienced a strengthened influx of O 2-rich SAMW-AAIW. On the other hand, OMZ conditions during DO interstadials and the Holocene seem best explained by analogy with the present-day situation: low supply of O 2 combined with elevated O 2

  16. Sink or link? The bacterial role in benthic carbon cycling in the Arabian Sea's oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Pozzato, L.; Van Oevelen, D.; Moodley, L.; Soetaert, K.; Middelburg, J. J.

    2013-11-01

    The bacterial loop, the consumption of dissolved organic matter (DOM) by bacteria and subsequent transfer of bacterial carbon to higher trophic levels, plays a prominent role in pelagic food webs. However, its role in sedimentary ecosystems is not well documented. Here we present the results of isotope tracer experiments performed under in situ oxygen conditions in sediments from inside and outside the Arabian Sea's oxygen minimum zone (OMZ) to study the importance of the microbial loop in this setting. Particulate organic matter, added as phytodetritus, was processed by bacteria, protozoa and metazoans, while dissolved organic matter was processed only by bacteria and there was very little, if any, transfer to higher trophic levels within the 7 day experimental period. This lack of significant transfer of bacterial-derived carbon to metazoan consumers indicates that the bacterial loop is rather inefficient, in sediments both inside and outside the OMZ. Moreover, metazoans directly consumed labile particulate organic matter resources and thus competed with bacteria for phytodetritus.

  17. Sedimentary pigments and nature of organic matter within the oxygen minimum zone (OMZ) of the Eastern Arabian Sea (Indian margin)

    NASA Astrophysics Data System (ADS)

    Rasiq, K. T.; Kurian, S.; Karapurkar, S. G.; Naqvi, S. W. A.

    2016-07-01

    Sedimentary pigments, carbon and nitrogen content and their stable isotopes were studied in three short cores collected from the oxygen minimum zone (OMZ) of the Eastern Arabian Sea (EAS). Nine pigments including chlorophyll a and their degradation products were quantified using High Performance Liquid Chromatography (HPLC). Astaxanthin followed by canthaxanthin and zeaxanthin were the major carotenoids detected in these cores. The total pigment concentration was high in the core collected from 500 m water depth (6.5 μgg-1) followed by 800 m (1.7 μgg-1) and 1100 m (1.1 μgg-1) depths respectively. The organic carbon did not have considerable control on sedimentary pigments preservation. Pigment degradation was comparatively high in the core collected from the 800 m site which depended not only the bottom dissolved oxygen levels, but also on the faunal activity. As reported earlier, the bottom water dissolved oxygen and presence of fauna have good control on the organic carbon accumulation and preservation at Indian margin OMZ sediments. The C/N ratios and δ13C values for all the cores conclude the marine origin of organic matter and δ15N profiles revealed signature of upwelling associated denitrification within the water column.

  18. Genetic and ecophysiological traits of Synechococcus strains isolated from coastal and open ocean waters of the Arabian Sea.

    PubMed

    Bemal, Suchandan; Anil, Arga Chandrashekar

    2016-11-01

    The picocyanobacterium Synechococcus is a prominent primary producer in the marine environment. The marine Synechococcus strains are clustered into different clades representing ecologically distinct genotypes. In this study, we compared phylogeny, photophysiology and cell cycles of four novel phycoerythrin-containing Synechococcus strains (clade II of subcluster 5.1) isolated from different depths of the water column (surface and subsurface waters) in coastal and offshore regions of the eastern Arabian Sea. The surface water strains possessed a lesser number of thylakoid layers and had a higher zeaxanthin to chlorophyll a ratio than subsurface strains indicating possible influence of light intensity available at their niche. The DNA distribution pattern of the four strains was bimodal in optimal cellular physiology conditions with cell division restricted to the light period and synchronized with the light-dark cycle. The presence of phycourobilin or phycoerythrobilin and the ratio between these two chromophores in all four strains varied according to available spectral wavelength in situ This study indicates that the timing of cell division is conserved within these genotypically identical Synechococcus strains, despite their having different chromophore ratios. We conclude that the timing of cell division of the Synechococcus strains has a genetic basis rather than being determined by phenotypic characters, such as chromophore content and ratio. PMID:27495242

  19. Fluorescence-based characterization of phycoerythrin-containing cyanobacterial communities in the Arabian Sea during the Northeast and early Southwest Monsoon (1994 1995)

    NASA Astrophysics Data System (ADS)

    Michelle Wood, A.; Lipsen, Michael; Coble, Paula

    1999-08-01

    Scanning fluorescence spectroscopy was used to investigate the spatial and temporal variability in the fluorescence signature of phycoerythrin-containing organisms in the Arabian Sea during the early Northeast and early Southwest Monsoon (1994-1995). Phycoerythrin (PE) emission spectra were relatively invariant among all the samples collected on either cruise; the relatively symmetrical PE emission peaks showed maxima at wavelengths ranging from 563-572 nm. PE excitation spectra always showed either a strong shoulder or a peak at wavelengths absorbed maximally by phycourobilin (PUB) chromophores as well as a peak at wavelengths absorbed maximally by phycoerythrobilin (PEB) chromophores. Thus, the Arabian Sea appears to be different from the Black Sea or Gulf of Maine in that PUB-lacking forms of PE rarely, if ever, dominate the PE signal. Fluorescence excitation signatures differed in the relative excitation of PE emission by wavelengths absorbed by PUB (˜495 nm, Ex PUB) and by wavelengths absorbed by PEB (˜550 nm, Ex PEB); these were distinguished by having either very low (˜0.6), very high (˜1.8), or intermediate Ex PUB:Ex PEB ratios. The distribution of samples with different PE fluorescence signatures was investigated extensively during the early Southwest Monsoon, and communities characterized by the low Ex PUB:Ex PEB ratios were closely associated with cooler (24-27°C), fresher (35.7-36.25 psu) water influenced by coastal upwelling. In general, "ambient" surface water of the Arabian Sea during the early Southwest Monsoon was of intermediate temperature (27-29°C) and salinity (36.15-36.4 psu) and showed intermediate or high values for Ex PUB:Ex PEB. This suggests that the PE fluorescence signature can be used to follow the fate of upwelling-influenced water masses and the populations they transport.

  20. 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.

  1. Past Temperature and Salinity of the Eastern Arabian Sea: Implications to Sun-Monsoon Precipitation Relationship over Past Couple of Millennia

    NASA Astrophysics Data System (ADS)

    Tiwari, Manish; Nagoji, Siddhesh; Ganeshram, Raja

    2016-04-01

    Eastern Arabian Sea is one of the few regions from where not many high-resolution records of sea surface temperature (SST) and salinity exist despite its hydrological importance vis-à-vis South Asian summer monsoon precipitation. During this period, significant changes in salinity occur in the eastern Arabian Sea due to orographic precipitation and runoff. Additionally, minimal bioturbation occurs in coastal sediments accumulating rapidly due to the presence of an oxygen minima zone (OMZ) in the Arabian Sea. The sediment core used in this study was collected offshore Mangalore from the middle of the OMZ from a water depth of 589 m. The core spans a period of 154 to 4772 yr BP. The average sedimentation rate is 8.96 cm/Kyr while the average resolution is ˜112 yrs/cm. The stable oxygen isotope content (δ18Oc) was determined on the planktic foraminifera Globigerinoides ruber while the past SST variations were determined using an independent parameter - Mg/Ca - in the same species. The salinity was obtained by delineating SST from the δ18Oc using empirical equations. The salinity varies from a maximum of 35.5 (arid) to a minimum of 32.4 (wet) while the SST varies from varies from a maximum of 29.9° C to a minimum of 27.5° C - a variability of 2.4° C. Such high variability could be during to its coastal location, which is affected by moderate upwelling during monsoon season. The long-term trend determined through linear regression shows that the salinity has been increasing since mid-Holocene implying increasing aridity. We identify periods of aridity during the Little Ice Age (and a few centuries prior to it) and at 1300 yr BP, 2000 yr BP, and 4600 yr BP. A few paleomonsoon records also exhibit prominent correspondence with solar activity during early Holocene and beyond. But despite the strong recent solar minima (e.g. Maunder, Spörer, Oort, Wolf), their correlation with monsoon precipitation is weak and inconclusive. Additionally, those from the western

  2. Topographic controls on bioproductivity and organic carbon deposition, Oman Arabian Sea coastal upwelling region

    SciTech Connect

    Brock, J.C.; Hay, W.W.

    1989-03-01

    Ocean boundary currents impinging on swallow shelves and coastal capes may undergo oceanward divergence driven by the conservation of potential vorticity. This process may result in local upwelling, enhanced primary productivity, and increased organic richness in sediments. Combined with reconstructions of past coastline configurations and models of paleo-ocean circulation, the recognition of this process should enable the hindcasting of more specific sites of organic carbon enrichment than has previously been possible. Preliminary investigations of ocean circulation along the southeastern coast of Arabia during recent southwest monsoon seasons suggest that continental shelf topography and coastal promontories act to focus upwelling. Thermal infrared NOAA advanced very high resolution radiometer images acquired during the 1981, 1982, 1983, and 1985 southwest monsoon seasons depict localized regions of depressed sea surface temperature near a major shelf break and coastal capes. These regions of cooler surface water may result from topographically focused upwelling plumes. Present work includes the development of a numerical ocean model to predict the effect of topography on the southwest monsoon current as it encounters the Omani coast. Thermal infrared and visible band satellite remote sensing is being integrated with in-situ vertical temperature profiles and sea surface temperature observations in order to assess horizontal and vertical water motion and surface layer bioproductivity during the monsoonal upwelling season. The effects of topographically focused coastal upwelling on organic carbon deposition are being assessed by the mapping of the total organic carbon content of surface sea-floor sediments.

  3. A study of the circulation and salinity budget of the Arabian Sea with an isopycnic coordinate ocean model

    NASA Astrophysics Data System (ADS)

    Esenkov, Oleg E.; Olson, Donald B.; Bleck, Rainer

    2003-07-01

    The evolution of surface circulation and salinity budget are studied with the open-boundary version of the Miami Isopycnic Coordinate Ocean Model (MICOM) that uses a global MICOM simulation as a boundary condition. Under climatological wind and thermodynamic forcing, the model develops solutions that are in good agreement with the climatologically forced global MICOM results and with observations. When the observed winds force the model, interannual variability of the surface fields increases significantly. However, coalescence of the two large eddies off Somalia in the end of the summer monsoon suggested in earlier observations does not occur in the model. To identify what processes facilitate or restrict the merger, a series of experiments was performed with modified model parameters and forcing fields. The eddies coalesced when half-slip, rather than no-slip, boundary conditions were used. In this case, less positive vorticity was produced at the coast, resulting in reduced blocking effect on the propagation of the southern eddy. The Socotra Island, which is submerged in the standard model, hinders a northward movement of the Great Whirl, leading to a stronger interaction between the eddies, which results in their subsequent merging. A more realistic coalescence occurs in an experiment where winds are held constant after reaching the peak summer value. Freshwater fluxes from the east and south are important for the salinity budget in the Arabian Sea, where evaporation exceeds precipitation. The only significant cross-equatorial transport of low-salinity water occurs in the upper 400 m in the model. Most of this water is advected below the surface mixed layer at the western boundary. The strongest interaction between the mixed layer and the oceanic interior occurs during the summer in the coastal upwelling regions off Somalia. Almost half of all upwelled water comes from depths between 100 and 200 m, thus signifying the importance of mid-depth circulation and

  4. Phycoerythrin-containing picocyanobacteria in the Arabian Sea in February 1995:. diel patterns, spatial variability, and growth rates

    NASA Astrophysics Data System (ADS)

    Sherry, Nelson D.; Michelle Wood, A.

    The abundance of phycoerythrin-containing picocyanobacteria in the surface mixed layer was measured both along-shore and offshore between 8 and 23 February 1995 in the Northwestern Arabian Sea. Water samples from 3 m depth were taken at 2-h intervals and picocyanobacterial abundance and frequency of dividing cells were determined by epifluorescence microscopy. Cell counts showed an average diel change from a mid-day minimum of ˜50×10 3 cells ml -1 to an evening maximum of ˜180×10 3 cells ml -1. The diel change was greater than the differences observed between physically and spatially discrete water masses. By counting the frequency of dividing cells (FDC) and using a novel approach to estimating the length of time required to complete cell division, growth and loss rates were both estimated to be ˜2.9 d -1 with daily turnover being 140% of the mean standing stock. If differences in the intrinsic population growth rate ( μ) and the net rate of change in cell number ( r) are assumed to be due to grazing, then grazing occurred throughout the day at a relatively constant rate (reflecting phytoplankton loss rates of ˜0.12 h -1). Cell division rates peaked in the late afternoon and early evening. FDC decreased throughout the night, suggesting that dark-inhibition of cell division is weak or nonexistent in the picocyanobacteria we studied. While all cell types included in this study would be identified as Synechococcus by flow cytometry because they were small unicells with bright phycoerythrin fluorescence, morphological variability suggests that the community was actually taxonomically diverse and included cells other than Synechococcus, including Synechocystis. Despite this diversity, the strong diel patterns we observed persisted throughout the study region, suggesting that great care should be taken when interpreting picocyanobacterial survey data and experimental results that do not account for the effects of time-of-day.

  5. Live-dead agreement of benthic communities under pressure by chronic oil pollution in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Albano, Paolo G.; Tomašových, Adam; Stachowitsch, Michael; Filippova, Nadezhda; Steger, Jan; Zuschin, Martin

    2014-05-01

    Mismatch between the richness or species composition of a death assemblage (DA) and the local living assemblage (LA) is typically attributed to natural post-mortem processes, particularly preservational bias. Recent research, however, suggests that live-dead (LD) agreement is significantly lower in anthropogenically disturbed settings. This reflects the so-called "compositional inertia" of DAs to recent environmental change, i.e., DAs still capture earlier community states not affected by such disturbance. The inertia to changing ecological conditions should be particularly likely under conditions of anthropogenic modification because the rapidity of many human-driven changes is unprecedented in natural systems. Our research tests this hypothesis by evaluating the agreement between the LA and DA in benthic communities around the Zakum oil field in the Southern Arabian Sea, off the coast of the United Arab Emirates. This is an area of intense oil extraction, with almost 800 offshore oil and gas platforms and 25 major terminals, but no studies on the related impacts are widely available. This approach also sheds light on chronic pollution in tropical settings, an underrepresented topic in the literature. The size fraction between 2 and 5 mm was sorted for living molluscs and empty shells, which were then segregated to morphospecies and identified. The agreement was evaluated in terms of fidelity of species richness, evenness, and rank-order agreement. Compositional fidelity was also evaluated by multivariate analysis. The communities are dominated by bivalves. Polyplacophorans and scaphopods are occasionally present. Gastropod abundance is marginal compared to the bivalves, although their contribution is more significant when species diversity is taken into consideration. Moreover, the living assemblage in the studied size range was particularly poor in terms of species abundance.

  6. Nitrogen transformations as inferred from the activities of key enzymes in the Arabian Sea oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Shailaja, M. S.; Narvekar, P. V.; Alagarsamy, R.; Naqvi, S. W. A.

    2006-06-01

    Vertical distributions of the potential activities of some key enzymes mediating nitrification and denitrification were investigated within the oxygen (O 2) minimum zone of the Arabian Sea at a number of locations between latitudes 17°N and 21°N and longitudes 63°E and 68°E so as to get an insight into the predominant biochemical mode(s) of production and consumption of nitrous oxide (N 2O). Results revealed that the dissimilatory nitrate (NO -3) reduction activity was generally very low or absent within the σ θ range 26.6-26.8, which corresponds to the Persian Gulf Watermass (PGW). Depth profiles of nitrate reductase (NaR), nitrite reductase (NiR) and ammonia monooxygenase (AMO) activities were compared with those of O 2, NO -3, nitrite (NO -2) and N 2O, and it is concluded that nitrifier denitrification rather than heterotrophic denitrification is active within the core of PGW. The presence of multiple peaks of AMO activity coinciding with distinct maxima in the O 2 profile and with a trend opposite to that of NaR activity indicates that the two processes, viz., classical and nitrifier denitrification, occur in discrete layers, probably determined by the variations in the ambient O 2 concentrations at various depths surrounding the PGW core. Further, it appears that at the depths where nitrifier denitrification is active in the absence of heterotrophic denitrification, N 2O builds up as its consumption may be inhibited by O 2. Possible reasons for the occurrence of appreciable nitrate deficit within the core of PGW, where dissimilatory NO -3 reduction is lacking, are discussed.

  7. Dissimilatory nitrate reduction by Aspergillus terreus isolated from the seasonal oxygen minimum zone in the Arabian Sea

    PubMed Central

    2014-01-01

    Background A wealth of microbial eukaryotes is adapted to life in oxygen-deficient marine environments. Evidence is accumulating that some of these eukaryotes survive anoxia by employing dissimilatory nitrate reduction, a strategy that otherwise is widespread in prokaryotes. Here, we report on the anaerobic nitrate metabolism of the fungus Aspergillus terreus (isolate An-4) that was obtained from sediment in the seasonal oxygen minimum zone in the Arabian Sea, a globally important site of oceanic nitrogen loss and nitrous oxide emission. Results Axenic incubations of An-4 in the presence and absence of oxygen and nitrate revealed that this fungal isolate is capable of dissimilatory nitrate reduction to ammonium under anoxic conditions. A 15N-labeling experiment proved that An-4 produced and excreted ammonium through nitrate reduction at a rate of up to 175 nmol 15NH4+ g-1 protein h-1. The products of dissimilatory nitrate reduction were ammonium (83%), nitrous oxide (15.5%), and nitrite (1.5%), while dinitrogen production was not observed. The process led to substantial cellular ATP production and biomass growth and also occurred when ammonium was added to suppress nitrate assimilation, stressing the dissimilatory nature of nitrate reduction. Interestingly, An-4 used intracellular nitrate stores (up to 6–8 μmol NO3- g-1 protein) for dissimilatory nitrate reduction. Conclusions Our findings expand the short list of microbial eukaryotes that store nitrate intracellularly and carry out dissimilatory nitrate reduction when oxygen is absent. In the currently spreading oxygen-deficient zones in the ocean, an as yet unexplored diversity of fungi may recycle nitrate to ammonium and nitrite, the substrates of the major nitrogen loss process anaerobic ammonium oxidation, and the potent greenhouse gas nitrous oxide. PMID:24517718

  8. Characterization of harmful algal blooms (HABs) in the Arabian Gulf and the Sea of Oman using MERIS fluorescence data

    NASA Astrophysics Data System (ADS)

    Zhao, Jun; Temimi, Marouane; Ghedira, Hosni

    2015-03-01

    In this study, MERIS fluorescence data were utilized to monitor a toxin-producing dinoflagellate Cochlodinium bloom in 2008 in the Arabian Gulf and the Sea of Oman. The bloom was characterized using modified fluorescence line height (MFLH), enhanced Red-Green-Blue (ERGB) and true color composites, and the ratio of particulate backscattering (bbp) to MFLH (bbp/MFLH). In addition to high MFLH values and dark colors in ERGB images which are generally observed when blooms happen, it was found that the Cochlodinium bloom indicated species-specific signatures which consisted of reddish brown colors in true color composites and bbp/MFLH values below 0.2 mW-1 cm2 μm m-1 sr. Based on these findings, Cochlodinium blooms were successfully distinguished from blooms dominated by other species that were found in the study area, like diatom, Noctiluca, and Trichodesmium. Qualitative analysis showed that the fluorescence-based approach presented better performance than the chlorophyll-a anomaly approach for HAB detection, despite the sensitivity to atmospheric perturbations, benthic vegetation in coastal shallow waters, and variations in environmental conditions. The applicability of the HAB characterization approach tested for the first time over the study area using MERIS data was discussed and can be anticipated with sufficient knowledge of local bloom history. Combing different ocean color products is strongly recommended to improve our understanding of HAB dynamics and enhance our ability to characterize them. This is of great importance for marine environment protection and management and can lead to valuable information for contingency planning.

  9. Oxygen minimum zone of the open Arabian Sea: variability of oxygen and nitrite from daily to decadal timescales

    NASA Astrophysics Data System (ADS)

    Banse, K.; Naqvi, S. W. A.; Narvekar, P. V.; Postel, J. R.; Jayakumar, D. A.

    2014-04-01

    The oxygen minimum zone (OMZ) of the Arabian Sea is the thickest of the three oceanic OMZ. It is of global biogeochemical significance because of denitrification in the upper part leading to N2 and N2O production. The residence time of OMZ water is believed to be less than a decade. The upper few hundred meters of this zone are nearly anoxic but non-sulfidic and still support animal (metazoan) pelagic life, possibly as a result of episodic injections of O2 by physical processes. We report on discrete measurements of dissolved O2 and NO2-, temperature and salinity made between 1959 and 2004 well below the tops of the sharp pycnocline and oxycline near 150, 200, 300, 400, and 500 m depth. We assemble nearly all O2 determinations (originally there were 849 values, 695 of which came from the OMZ) by the visual endpoint detection of the iodometric Winkler procedure, which in our data base yields about 0.04 mL L-1 (~ 2 μM) O2 above the endpoint from modern automated titration methods. We acknowledge that much lower (nanomolar) O2 values have been measured recently with the STOX (Switchable Trace amount OXygen) sensor in the eastern tropical South Pacific, and that similar conditions may also prevail in the Arabian Sea OMZ. In spite of the error in O2 measurements at vanishingly low levels, we argue that the temporal trends of the historic data should still hold. We find 632 values acceptable (480 from 150 stations in the OMZ). The data are grouped in zonally paired boxes of 1° lat. and 2° long. centered at 8, 10, 12, 15, 18, 20, and 21° N along 65 and 67° E. The latitudes of 8-12° N, outside the OMZ, are treated in passing. The principal results are as follows: (1) an O2 climatology for the upper OMZ reveals a marked seasonality at 200 to 500 m depth with O2 levels during the northeast monsoon and spring intermonsoon seasons elevated over those during the southwest monsoon season (median difference, 0.08 mL L-1 [~ 3.5 μM]). The medians of the slopes of the

  10. Large Scale Patterns of Antimicrofouling Defenses in the Hard Coral Pocillopora verrucosa in an Environmental Gradient along the Saudi Arabian Coast of the Red Sea

    PubMed Central

    Wahl, Martin; Al Sofyani, Abdulmohsin; Saha, Mahasweta; Kruse, Inken; Lenz, Mark; Sawall, Yvonne

    2014-01-01

    Large scale patterns of ecologically relevant traits may help identify drivers of their variability and conditions beneficial or adverse to the expression of these traits. Antimicrofouling defenses in scleractinian corals regulate the establishment of the associated biofilm as well as the risks of infection. The Saudi Arabian Red Sea coast features a pronounced thermal and nutritional gradient including regions and seasons with potentially stressful conditions to corals. Assessing the patterns of antimicrofouling defenses across the Red Sea may hint at the susceptibility of corals to global change. We investigated microfouling pressure as well as the relative strength of 2 alternative antimicrofouling defenses (chemical antisettlement activity, mucus release) along the pronounced environmental gradient along the Saudi Arabian Red Sea coast in 2 successive years. Microfouling pressure was exceptionally low along most of the coast but sharply increased at the southernmost sites. Mucus release correlated with temperature. Chemical defense tended to anti-correlate with mucus release. As a result, the combined action of mucus release and chemical antimicrofouling defense seemed to warrant sufficient defense against microbes along the entire coast. In the future, however, we expect enhanced energetic strain on corals when warming and/or eutrophication lead to higher bacterial fouling pressure and a shift towards putatively more costly defense by mucus release. PMID:25485603

  11. Large scale patterns of antimicrofouling defenses in the hard coral Pocillopora verrucosa in an environmental gradient along the Saudi Arabian coast of the Red Sea.

    PubMed

    Wahl, Martin; Al Sofyani, Abdulmohsin; Saha, Mahasweta; Kruse, Inken; Lenz, Mark; Sawall, Yvonne

    2014-01-01

    Large scale patterns of ecologically relevant traits may help identify drivers of their variability and conditions beneficial or adverse to the expression of these traits. Antimicrofouling defenses in scleractinian corals regulate the establishment of the associated biofilm as well as the risks of infection. The Saudi Arabian Red Sea coast features a pronounced thermal and nutritional gradient including regions and seasons with potentially stressful conditions to corals. Assessing the patterns of antimicrofouling defenses across the Red Sea may hint at the susceptibility of corals to global change. We investigated microfouling pressure as well as the relative strength of 2 alternative antimicrofouling defenses (chemical antisettlement activity, mucus release) along the pronounced environmental gradient along the Saudi Arabian Red Sea coast in 2 successive years. Microfouling pressure was exceptionally low along most of the coast but sharply increased at the southernmost sites. Mucus release correlated with temperature. Chemical defense tended to anti-correlate with mucus release. As a result, the combined action of mucus release and chemical antimicrofouling defense seemed to warrant sufficient defense against microbes along the entire coast. In the future, however, we expect enhanced energetic strain on corals when warming and/or eutrophication lead to higher bacterial fouling pressure and a shift towards putatively more costly defense by mucus release. PMID:25485603

  12. Culturable bacterial flora associated with the dinoflagellate green Noctiluca miliaris during active and declining bloom phases in the Northern Arabian Sea.

    PubMed

    Basu, Subhajit; Deobagkar, Deepti D; Matondkar, S G Prabhu; Furtado, Irene

    2013-05-01

    A massive algal bloom of the dinoflagellate Noctiluca miliaris (green) was located in the Northern Arabian Sea by IRS-P4-2 (OCM-II) for microbiological studies, during two consecutive cruises of February-March 2009. Culturable bacterial load during bloom were ≈ 2-3-fold higher in comparison to non-bloom waters and ranged from 3.20 × 10(5) to 6.84 × 10(5) cfu ml(-1). An analysis of the dominant heterotrophs associated with Noctiluca bloom resulted in phylogenetic and a detailed metabolic characterization of 70 bacterial isolates from an overlapping active and declining bloom phase location near north-central Arabian Sea. The active phase flora was dominated by Gram-positive forms (70.59 %), a majority of which belonged to Bacillus (35.29 %) of Firmicutes. As the bloom declined, Gram-negative forms (61.11 %) emerged dominant, and these belonged to a diverse γ-proteobacterial population consisting of Shewanella (16.67 %) and equal fractions of a Cobetia-Pseudomonas-Psychrobacter-Halomonas population (36.11 %). A Unifrac-based principal coordinate analysis of partial 16S rDNA sequences showed significant differences among the active and declining phase flora and also with reported endocytic flora of Noctiluca (red). A nonparametric multidimensional scaling (NMDS) of antibiogram helped differentiation among closely related strains. The organic matter synthesized by N. miliaris appears to be quickly utilized and remineralized as seen from the high efficiency of isolates to metabolize various complex and simple C/N substrates such as carbohydrates, proteins/amino acids, lipids, sulfide production from organic matter, and solubilize phosphates. The ability of a large fraction of these strains (50-41.67 %) to further aerobically denitrify indicates their potential for nitrogen removal from these high-organic microniches of the Noctiluca bloom in the Arabian Sea, also known for high denitrification activity. The results indicate that culturable euphotic bacterial

  13. (abstract) Ekman Pumping/Suction and Wind-Driven Ocean Circulation from ERS-1 Scatterometer Measurements Over the Arabian Sea During October 1994-October 1995

    NASA Technical Reports Server (NTRS)

    Halpern, D.; Freilich, M. H.; Weller, R. A.

    1996-01-01

    Spatial variations of the east-west and north-south components of surface wind stress are critical in studies of ocean circulation and biological-physical interactions because surface wind stress curl produces a vertical velocity in the upper ocean at the bottom of the Ekman Layer.The ERS-1 scatterometer provides reasonable coverage and direct measurements of vector of winds. Three schemes are evaluated relative to high-quality moored-bouy wind observations recorded in the central Arabian Sea, where high surface waves and high atmospheric water content during the southeast monsoon adversely affect the estimation of satellite-derived winds.

  14. A new species of the rare nematode genus Paramicrolaimus Wieser, 1954 (Chromadorida: Paramicrolaimidae) from the south eastern Arabian Sea.

    PubMed

    Jacob, Jini; Jaleel, Abdul K U; Vijayan, Anil Kumar

    2015-01-01

    A new paramicrolaimid nematode, Paramicrolaimus damodarani sp. nov., is described based on specimens from the continental shelf (95 m) of the south eastern Arabian Sea. Paramicrolaimus damodarani sp. nov. differs from other known species of the genus in having a smaller body size, form of the spicular apparatus, presence of 7 cuticularised protruding precloacal supplements and a strongly cuticularised terminal spinneret. This is the first record of the genus Paramicrolaimus from the northern Indian Ocean. A pictorial key to the four species of Paramicrolaimus is also provided, supplemented with comparative characters, based on published information. PMID:25660800

  15. Chlorinated pesticide residues in sediments from the Arabian Sea along the central west coast of India

    SciTech Connect

    Sarkar, A.; Gupta, R.S.

    1987-12-01

    The problem of environmental contamination by persistent chlorinated pesticides still evokes major concern due to the presence of their residues in the environment and in human tissues. In developing countries like India organochlorine insecticides, especially DDT are extensively being used in agriculture and vector control programs. Few data are available on their levels of concentration from the seas around India. Persistent pesticides residues can be expected to accumulate in marine sediments. However, very little data on this are available along the Indian coast. An attempt has been made in the present communication to identify and quantify some of the chlorinated pesticides residues in the marine sediments collected from different region along the central west coast of India. This is a part of our ongoing project to monitor and map pollutants within the exclusive economic zone of India.

  16. Effects of warm Arabian Sea Surface Temperature on the Summer Monsoon over Peninsular Indian Region

    NASA Astrophysics Data System (ADS)

    Janardanan, Rajesh; Mohanakumar, Kesavapillai; Rajanayagam, Lorna

    This study investigates the characteristics of circulation and precipitation during monsoon season over peninsular Indian region, based on the sensitivity experiments performed by a regional climate model for the year 2002. The present study uses a recent version (Version-III) of National Center for Atmospheric Research (NCAR) Regional Climate Model (RegCM3). The planetary boundary layer scheme used is that of Holtslag, cumulus parameterization scheme Emanuel of MIT, SUBEX large scale precipitation scheme and BATS ocean flux parameterization scheme. The model is run from 1st May to 30th September. The first month is taken for the spin up. The next four months are taken to study the monsoon. RegCM3 has been integrated at 60 km horizontal resolution over the Indian domain. The experiments are carried out by changing the initial conditions of Sea Surface Temperature by 0.1 degree steps ie. 0.1, 0.2 etc. to 1 degree maximum. The sensitivity experiments showed that the wind strength increases significantly to the northeastern and central parts of India. The change in wind strength is pronounced over the southern peninsula when the Sea Surface Temperature increased by 0.4 degree. The response in precipitation over the peninsular Indian region is also studied. The monsoon circulation features simulated by RegCM3 are compared with those of the NCEP/NCAR reanalysis and the simulated rainfall is validated against observations from the Global Precipitation Climatology Centre (GPCC) Key words:- Peninsular India, model integration, Monsoon Rainfall Reference: K. C. chow, Yiming Liu, Johnny C. L. Chan and Yihui Ding, Int. J. Climatol. 26: 1339-1359 (2006) K. C. Chow, Hang-Wai Tong and Johnny C. L. Chan, Clim. Dyn. DOI 10.1007/s00382-007- 0301-6 G. P. Singh, Jai-Ho Oh, Jin-Young Kim and Ok-Yeon Kim; ", SOLA, Vol. 2, pp.29-32 (2006) Dash S. K., Shekhar M. S., Singh G. P. Theoretical and Applied Climatology 86(1-4): 161 (2006)

  17. Inhibition of mixed-layer deepening during winter in the northeastern Arabian Sea by the West India Coastal Current

    NASA Astrophysics Data System (ADS)

    Shankar, D.; Remya, R.; Vinayachandran, P. N.; Chatterjee, Abhisek; Behera, Ambica

    2015-10-01

    Though the deep mixed layers (MLs) that form in the northeastern Arabian Sea (NEAS) during the winter monsoon (November-February) have been attributed to convective mixing driven by dry, cool northeasterly winds from the Indian subcontinent, data show that the deepest MLs occur in the northern NEAS and the maxima of latent-heat and net heat fluxes in the southern NEAS. We use an oceanic general circulation model to show that the deep MLs in the NEAS extend up to ~20°N till the end of December, but are restricted poleward of ~22°N (~23°N) in January (February). This progressive restriction of the deep mixed layers within the NEAS is due to poleward advection of water of lower salinity by the West India Coastal Current (WICC). The deep MLs are sustained till February in the northern NEAS because convective mixing deepens the ML before the waters of lower salinity reach this region and the wind stirring and convective overturning generate sufficient turbulent energy for the ML to maintain the depth attained in January. Though the atmospheric fluxes tend to cool the ML in the southern NEAS, this cooling is countered by the warming due to horizontal advection. Likewise, the cooling due to entrainment, which continues in the southern NEAS even as the ML shallows during January-February, is almost cancelled by the warming caused by a downwelling vertical velocity field. Therefore, the SST changes very little during December-February even as the ML shallows dramatically in the southern NEAS. These deep MLs of the NEAS also preclude a strong intraseasonal response to the intraseasonal variability in the fluxes. This role of horizontal advection implies that the ML depth in the NEAS is determined by an interplay of physical processes that are forced differently. The convective mixing depends on processes that are local to the region, but the advection is due to the WICC, whose seasonal cycle is primarily forced by remote winds. By inhibiting the formation of deep MLs in

  18. A multiproxy approach to understanding the "enhanced" flux of organic matter through the oxygen deficient waters of the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Keil, R. G.; Neibauer, J.; Biladeau, C.; van der Elst, K.; Devol, A. H.

    2015-10-01

    Free-drifting sediment net traps were deployed 14 times at depths between 80 and 500 m for 1-3 days each during the late monsoon/intermonsoon transition in the central Arabian Sea. Two locations (19.5 and 15.5° N) were within the permanently oxygen deficient zone, and a third (11° N) had a shallow and thin oxygen minimum. The secondary nitrite maximum, which serves as a tracer of the oxygen deficient zone (ODZ) zone, thinned from ∼ 250 m thick at stations 19.5 and 15.5° N to ∼ 50 m thick at station 11° N. Overall, organic carbon fluxes ranged from 13.2 g m2 yr-1 at 80 m to a minimum of 1.1 g m2 yr-1 at 500 m. Fluxes at the more oxygenated 11° N station attenuate faster than within the permanent ODZ. Martin curve attenuation coefficients for 19.5 and 15.5° N are 0.59 and 0.63 and for 11° N it is 0.98. At least six potential mechanisms might explain why sinking particles sinking through the ODZ are more effectively transferred to depth; (M1) oxygen effects, (M2) microbial loop efficiencies and chemoautotrophy, (M3) changes in zooplankton dynamics, (M4) additions of ballast that might sorb and protect organic matter from decay, (M5) inputs of refractory organic matter, and (M6) changes in sinking speeds. These mechanisms are intertwined, and were explored using a combination of mineral (XPS) and organic matter characterizations of the sinking material and ship-board incubation experiments. Evidence was found supporting an oxygen effect and/or changes in the efficiency of the microbial loop including the addition of chemoautotrophic carbon to the sinking flux in the upper 500 m. Less evidence was found for the other potential mechanisms. A simple conceptual model consistent with our and other recent data suggests that the upper ODZ microbial community determines the initial flux attenuation, and that deeper in the water column zooplankton and sinking speed become more important. The exact interplay between the various mechanisms remains to be further

  19. Inhibition of mixed-layer deepening during winter in the northeastern Arabian Sea by the West India Coastal Current

    NASA Astrophysics Data System (ADS)

    Shankar, D.; Remya, R.; Vinayachandran, P. N.; Chatterjee, Abhisek; Behera, Ambica

    2016-08-01

    Though the deep mixed layers (MLs) that form in the northeastern Arabian Sea (NEAS) during the winter monsoon (November-February) have been attributed to convective mixing driven by dry, cool northeasterly winds from the Indian subcontinent, data show that the deepest MLs occur in the northern NEAS and the maxima of latent-heat and net heat fluxes in the southern NEAS. We use an oceanic general circulation model to show that the deep MLs in the NEAS extend up to ~20°N till the end of December, but are restricted poleward of ~22°N (~23°N) in January (February). This progressive restriction of the deep mixed layers within the NEAS is due to poleward advection of water of lower salinity by the West India Coastal Current (WICC). The deep MLs are sustained till February in the northern NEAS because convective mixing deepens the ML before the waters of lower salinity reach this region and the wind stirring and convective overturning generate sufficient turbulent energy for the ML to maintain the depth attained in January. Though the atmospheric fluxes tend to cool the ML in the southern NEAS, this cooling is countered by the warming due to horizontal advection. Likewise, the cooling due to entrainment, which continues in the southern NEAS even as the ML shallows during January-February, is almost cancelled by the warming caused by a downwelling vertical velocity field. Therefore, the SST changes very little during December-February even as the ML shallows dramatically in the southern NEAS. These deep MLs of the NEAS also preclude a strong intraseasonal response to the intraseasonal variability in the fluxes. This role of horizontal advection implies that the ML depth in the NEAS is determined by an interplay of physical processes that are forced differently. The convective mixing depends on processes that are local to the region, but the advection is due to the WICC, whose seasonal cycle is primarily forced by remote winds. By inhibiting the formation of deep MLs in

  20. Evolution and sub-surface characteristics of a sea-surface temperature filament and front in the northeastern Arabian Sea during November-December 2012

    NASA Astrophysics Data System (ADS)

    Vipin, P.; Sarkar, Kankan; Aparna, S. G.; Shankar, D.; Sarma, V. V. S. S.; Gracias, D. G.; Krishna, M. S.; Srikanth, G.; Mandal, R.; Rama Rao, E. P.; Srinivasa Rao, N.

    2015-10-01

    We used satellite-derived sea-surface-temperature (SST) data along with in-situ data collected along a meridional transect between 18.85 and 20.25°N along 69.2°E to describe the evolution of an SST filament and front during 25 November to 1 December in the northeastern Arabian Sea (NEAS). Both features were ~ 100 km long, lasted about a week, and were associated with weak temperature gradients (~ 0.07 °C km- 1). The in-situ data were collected first using a suite of surface sensors during a north-south mapping of this transect and showed the existence of a chlorophyll maximum within the filament. This surface data acquisition was followed by a high-resolution south-north CTD (conductivity-temperature-depth) sampling along the transect. In the two days that elapsed between the two in-situ measurements, the filament had shrunk in size and moved northward. In general, the current direction was northwestward and advected these mesoscale features. The CTD data also showed an SST front towards the northern end of the transect. In both these features, the chlorophyll concentration was higher than in the surrounding waters. The temperature and salinity data from the CTD suggest upward mixing or pumping of water from the base of the mixed layer, where a chlorophyll maximum was present, into the mixed layer that was about 60 m thick. A striking diurnal cycle was evident in the chlorophyll concentration, with higher values tending to occur closer to the surface during the night. The in-situ data from both surface sensors and CTD, and so also satellite-derived chlorophyll data, showed higher chlorophyll concentration, particularly at sub-surface levels, between the filament and the front, but there was no corresponding signature in the temperature and salinity data. Analysis of the SST fronts in the satellite data shows that fronts weaker than those associated with the filament and the front had crossed the transect in this region a day or two preceding the sampling of the

  1. Symbiodinium thermophilum sp. nov., a thermotolerant symbiotic alga prevalent in corals of the world's hottest sea, the Persian/Arabian Gulf

    PubMed Central

    Hume, B. C. C.; D'Angelo, C.; Smith, E. G.; Stevens, J. R.; Burt, J.; Wiedenmann, J.

    2015-01-01

    Coral reefs are in rapid decline on a global scale due to human activities and a changing climate. Shallow water reefs depend on the obligatory symbiosis between the habitat forming coral host and its algal symbiont from the genus Symbiodinium (zooxanthellae). This association is highly sensitive to thermal perturbations and temperatures as little as 1°C above the average summer maxima can cause the breakdown of this symbiosis, termed coral bleaching. Predicting the capacity of corals to survive the expected increase in seawater temperatures depends strongly on our understanding of the thermal tolerance of the symbiotic algae. Here we use molecular phylogenetic analysis of four genetic markers to describe Symbiodinium thermophilum, sp. nov. from the Persian/Arabian Gulf, a thermally tolerant coral symbiont. Phylogenetic inference using the non-coding region of the chloroplast psbA gene resolves S. thermophilum as a monophyletic lineage with large genetic distances from any other ITS2 C3 type found outside the Gulf. Through the characterisation of Symbiodinium associations of 6 species (5 genera) of Gulf corals, we demonstrate that S. thermophilum is the prevalent symbiont all year round in the world's hottest sea, the southern Persian/Arabian Gulf. PMID:25720577

  2. Symbiodinium thermophilum sp. nov., a thermotolerant symbiotic alga prevalent in corals of the world's hottest sea, the Persian/Arabian Gulf.

    PubMed

    Hume, B C C; D'Angelo, C; Smith, E G; Stevens, J R; Burt, J; Wiedenmann, J

    2015-01-01

    Coral reefs are in rapid decline on a global scale due to human activities and a changing climate. Shallow water reefs depend on the obligatory symbiosis between the habitat forming coral host and its algal symbiont from the genus Symbiodinium (zooxanthellae). This association is highly sensitive to thermal perturbations and temperatures as little as 1°C above the average summer maxima can cause the breakdown of this symbiosis, termed coral bleaching. Predicting the capacity of corals to survive the expected increase in seawater temperatures depends strongly on our understanding of the thermal tolerance of the symbiotic algae. Here we use molecular phylogenetic analysis of four genetic markers to describe Symbiodinium thermophilum, sp. nov. from the Persian/Arabian Gulf, a thermally tolerant coral symbiont. Phylogenetic inference using the non-coding region of the chloroplast psbA gene resolves S. thermophilum as a monophyletic lineage with large genetic distances from any other ITS2 C3 type found outside the Gulf. Through the characterisation of Symbiodinium associations of 6 species (5 genera) of Gulf corals, we demonstrate that S. thermophilum is the prevalent symbiont all year round in the world's hottest sea, the southern Persian/Arabian Gulf. PMID:25720577

  3. Three-dimensional imaging of the S-velocity structure for the crust and the upper mantle beneath the Arabian Sea from Rayleigh wave analysis

    NASA Astrophysics Data System (ADS)

    Corchete, V.

    2016-07-01

    A 3D imaging of S-velocity for the Arabian Sea crust and upper mantle structure is presented in this paper, determined by means of Rayleigh wave analysis, for depths ranging from zero to 300 km. The crust and upper mantle structure of this region of the earth never has been the subject of a surface wave tomography survey. The Moho map performed in the present study is a new result, in which a crustal thickening beneath the Arabian Fan sediments can be observed. This crustal thickening can be interpreted as a quasi-continental oceanic transitional structure. A crustal thickness of up to 20 km also can be observed for the Murray Ridge system in this Moho map. This crustal thickening can be due to that the Murray Ridge System consists of Indian continental crust. This continental crust is extremely thinned to the southwest of this region, as shown in this Moho map. This area can be interpreted as oceanic in origin. In the depth range from 30 to 60 km, the S-velocity presents its lower values at the Carlsberg Ridge region, because it is the younger region of the study area. In the depth range from 60 to 105 km of depth, the S-velocity pattern is very similar to that shown for the previous depth range, except for the regions in which the asthenosphere is reached, for these regions appear a low S-velocity pattern. The lithosphere-asthenosphere boundary (LAB), or equivalently the lithosphere thickness, determined in the present study is also a new result, in which the lithosphere thickness for the Arabian Fan can be estimated in 60-70 km. The lower lithospheric thickness observed in the LAB map, for the Arabian Fan, shows that this region may be in the transition zone between continental and oceanic structure. Finally, a low-velocity zone (LVZ) has been determined, for the whole study area, located between the LAB and the boundary of the asthenosphere base (or equivalently the lithosphere-asthenosphere system thickness). The asthenosphere-base map calculated in the

  4. Denitrifying Alphaproteobacteria from the Arabian Sea That Express nosZ, the Gene Encoding Nitrous Oxide Reductase, in Oxic and Suboxic Waters

    PubMed Central

    Hodgson, Sylvia; Bird, Clare

    2013-01-01

    Marine ecosystems are significant sources of the powerful greenhouse gas nitrous oxide (N2O). A by-product of nitrification and an intermediate in the denitrification pathway, N2O is formed primarily in oxygen-deficient waters and sediments. We describe the isolation of a group of alphaproteobacteria from the suboxic waters of the Arabian Sea that are phylogenetically affiliated with Labrenzia spp. and other denitrifiers. Quantitative PCR assays revealed that these organisms were very broadly distributed in this semienclosed ocean basin. Their biogeographical range extended from the productive, upwelling region off the Omani shelf to the clear, oligotrophic waters that are found much further south and also included the mesotrophic waters overlying the oxygen minimum zone (OMZ) in the northeastern sector of the Arabian Sea. These organisms actively expressed NosZ (N2O reductase, the terminal step in the denitrification pathway) within the OMZ, an established region of pelagic denitrification. They were found in greatest numbers outside the OMZ, however, and nosZ mRNAs were also readily detected near the base of the upper mixed layer in nutrient-poor, oxic regions. Our findings provide firm molecular evidence of a potential sink for N2O within well-ventilated, oceanic surface waters in this biogeochemically important region. We show that the Labrenzia-like denitrifiers and their close relatives are habitual colonizers of the pseudobenthic environment provided by Trichodesmium spp. We develop the conjecture that the O2-depleted microzones that occur within the colonies of these filamentous, diazotrophic cyanobacteria might provide unexpected niches for the reduction of nitrogen oxides in tropical and subtropical surface waters. PMID:23396348

  5. Millennial-scale oscillation of denitrification intensity in the Arabian Sea during the Late Quaternary and its potential influence on atmospheric N2O and global climate

    NASA Astrophysics Data System (ADS)

    Suthhof, Andreas; Ittekkot, Venugopalan; Gaye-Haake, Birgit

    2001-09-01

    The intensity of denitrification in the Arabian Sea during the last 65 kyr is reconstructed using high-resolution δ15N records of three sediment cores in conjunction with other geochemical tracers for water column oxygenation and productivity. The results reveal a close link to the Greenland ice core record with low or absent water column denitrification during the Last Glacial Maximum, the stadials, and at the time of the Heinrich Events including the Younger Dryas. In contrast, denitrification was high during the Holocene and the interstadials. The intensification of denitrification is related to stronger SW monsoonal upwelling, which enhances organic matter flux and degradation, resulting in a strengthening of the midwater oxygen deficiency. Such a combination of enhanced upwelling and denitrification has also been implied for the Eastern Tropical North Pacific (ETNP), where these events occur during the Holocene and to some extent during the interstadials, too. Today, the Arabian Sea and the ETNP together contribute substantially to the global marine water column denitrification, and a significant fraction of the ocean-atmosphere N2O flux originates from these areas. Changes in N2O emissions from these areas could thus have effected the recently described stadial/interstadial variations in the atmospheric concentration of this greenhouse gas as deduced from ice cores. Moreover, denitrification is the major sink for oceanic nitrate and provides a primary control for the oceanic nutrient inventory, which in turn influences global primary productivity and CO2 sequestration by the biological pump. Short-term switches between a nondenitrification mode and a denitrification mode in these marine regions therefore have an impact on global climate.

  6. Phylogenetic analyses and nitrate-reducing activity of fungal cultures isolated from the permanent, oceanic oxygen minimum zone of the Arabian Sea.

    PubMed

    Manohar, Cathrine Sumathi; Menezes, Larissa Danielle; Ramasamy, Kesava Priyan; Meena, Ram M

    2015-03-01

    Reports on the active role of fungi as denitrifiers in terrestrial ecosystems have stimulated an interest in the study of the role of fungi in oxygen-deficient marine systems. In this study, the culturable diversity of fungi was investigated from 4 stations within the permanent, oceanic, oxygen minimum zone of the Arabian Sea. The isolated cultures grouped within the 2 major fungal phyla Ascomycota and Basidiomycota; diversity estimates in the stations sampled indicated that the diversity of the oxygen-depleted environments is less than that of mangrove regions and deep-sea habitats. Phylogenetic analyses of 18S rRNA sequences revealed a few divergent isolates that clustered with environmental sequences previously obtained by others. This is significant, as these isolates represent phylotypes that so far were known only from metagenomic studies and are of phylogenetic importance. Nitrate reduction activity, the first step in the denitrification process, was recorded for isolates under simulated anoxic, deep-sea conditions showing ecological significance of fungi in the oxygen-depleted habitats. This report increases our understanding of fungal diversity in unique, poorly studied habitats and underlines the importance of fungi in the oxygen-depleted environments. PMID:25688692

  7. Rainouts over the Arabian Sea and Western Ghats during moisture advection and recycling explain the isotopic composition of Bangalore summer rains

    NASA Astrophysics Data System (ADS)

    Rahul, P.; Ghosh, Prosenjit; Bhattacharya, S. K.

    2016-06-01

    Variations in the isotope ratios (18O/16O and D/H) of meteoric water at continental stations serve as valuable tracers for the hydrological cycle. In the present study, we investigated the role of sea surface temperature, wind speed, relative humidity, and rainout processes on the stable isotopic composition of the 2010 monsoon rainwater of Bangalore. The wind over the ocean influences the sea surface temperature and humidity which in turn influence the vapor isotopic composition. The rainout over the Arabian Sea and the land mass (Western Ghats) during advection of the air parcel to Bangalore and its recycling further modify the vapor composition. The isotopic ratios (δ18O, δD, and d-excess) of the precipitation at Bangalore was estimated following a Rayleigh fractionation model involving rainout and recycling processes yield values consistent with our observation. In some samples, however, the observed isotopic ratios are higher (by 2 to 5‰), and a few of them are associated with high d-excess values. These discrepancies could be due to limitation of the model assumptions.

  8. Population history of the Red Sea--genetic exchanges between the Arabian Peninsula and East Africa signaled in the mitochondrial DNA HV1 haplogroup.

    PubMed

    Musilová, Eliška; Fernandes, Verónica; Silva, Nuno M; Soares, Pedro; Alshamali, Farida; Harich, Nourdin; Cherni, Lotfi; Gaaied, Amel Ben Ammar El; Al-Meeri, Ali; Pereira, Luísa; Cerný, Viktor

    2011-08-01

    Archaeological studies have revealed cultural connections between the two sides of the Red Sea dating to prehistory. The issue has still not been properly addressed, however, by archaeogenetics. We focus our attention here on the mitochondrial haplogroup HV1 that is present in both the Arabian Peninsula and East Africa. The internal variation of 38 complete mitochondrial DNA sequences (20 of them presented here for the first time) affiliated into this haplogroup testify to its emergence during the late glacial maximum, most probably in the Near East, with subsequent dispersion via population expansions when climatic conditions improved. Detailed phylogeography of HV1 sequences shows that more recent demographic upheavals likely contributed to their spread from West Arabia to East Africa, a finding concordant with archaeological records suggesting intensive maritime trade in the Red Sea from the sixth millennium BC onwards. Closer genetic exchanges are apparent between the Horn of Africa and Yemen, while Egyptian HV1 haplotypes seem to be more similar to the Near Eastern ones. PMID:21660931

  9. Planktic foraminiferal assemblages from laminated sediments of the northeastern Arabian Sea: a high-resolution study over the last two millennia

    NASA Astrophysics Data System (ADS)

    Munz, Philipp; Lückge, Andreas; Siccha, Michael; Kucera, Michal; Schulz, Hartmut

    2014-05-01

    Modern planktic foraminiferal assemblages in the Arabian Sea are largely controlled by seasonal shifts of surface water properties. Boreal summer (June-September) heating of the Asian landmass and Tibetan Plateau leads to northward migration of the ITCZ and develops an intense atmospheric pressure gradient. Strong monsoonal winds from the southwest lead to coastal- and open ocean upwelling, especially in the western Arabian Sea along the coast of Somalia and Oman. Opposite directed dry and cold winds lead to deep convective mixing during boreal winter (January-March) and breakup of the thermal stratification. Deepening of the mixed-layer thus enables nutrient transport into the photic zone with enhanced primary production. Here we study planktic foraminiferal assemblages from the dominantly winter monsoon controlled Pakistan Margin off Karachi. We sampled annually laminated sediments from box core SO90-39KG and ca. 2-m-long piston core SO130-275KL from the same station. High sedimentation rates and varve-like lamination provides a particular record with very precise age control. Box core 39KG offers a record of the last 100 years with 2-year-resolution and 275KL provides a ca. 10-year-resolution during the last 2100 years. We calculated foraminiferal flux rates after photometric identification and subtraction of light-colored event layers, consisting solely of terrigeneous matter to enable comparison with flux rates from sediment trap stations. We identified a total of 28 planktic foraminiferal (PF) species/morphotypes in the fraction >150μm. During the relatively short period of the past two millennia, several species showed comparatively large fluctuations on decadal time scales, not seen in bioturbated records. Globigerina bulloides, a species generally associated with high primary production rates, fluctuates between ca. 10% and 45%. Highest relative share was observed during periods 1593-1413, 1023-923, 483-393, 63- -7 years AD. Average PF accumulation rates

  10. The middle Holocene climatic records from Arabia: Reassessing lacustrine environments, shift of ITCZ in Arabian Sea, and impacts of the southwest Indian and African monsoons

    NASA Astrophysics Data System (ADS)

    Enzel, Yehouda; Kushnir, Yochanan; Quade, Jay

    2015-06-01

    A dramatic increase in regional summer rainfall amount has been proposed for the Arabian Peninsula during the middle Holocene (ca. 9-5 ka BP) based on lacustrine sediments, inferred lake levels, speleothems, and pollen. This rainfall increase is considered primarily the result of an intensified Indian summer monsoon as part of the insolation-driven, northward shift of the boreal summer position of the Inter-Tropical Convergence Zone (ITCZ) to over the deserts of North Africa, Arabia, and northwest India. We examine the basis for the proposed drastic climate change in Arabia and the shifts in the summer monsoon rains, by reviewing paleohydrologic lacustrine records from Arabia. We evaluate and reinterpret individual lake-basin status regarding their lacustrine-like deposits, physiography, shorelines, fauna and flora, and conclude that these basins were not occupied by lakes, but by shallow marsh environments. Rainfall increase required to support such restricted wetlands is much smaller than needed to form and maintain highly evaporating lakes and we suggest that rainfall changes occurred primarily at the elevated edges of southwestern, southern, and southeastern Arabian Peninsula. These relatively small changes in rainfall amounts and local are also supported by pollen and speleothems from the region. The changes do not require a northward shift of the Northern Hemisphere summer ITCZ and intensification of the Indian monsoon rainfall. We propose that (a) latitudinal and slight inland expansion of the North African summer monsoon rains across the Red Sea, and (b) uplifted moist air of this monsoon to southwestern Arabia highlands, rather than rains associated with intensification of Indian summer monsoon, as proposed before, increased rains in that region; these African monsoon rains produced the modest paleo-wetlands in downstream hyperarid basins. Furthermore, we postulate that as in present-day, the ITCZ in the Indian Ocean remained at or near the equator all

  11. The Jebel Ohier deposit—a newly discovered porphyry copper-gold system in the Neoproterozoic Arabian-Nubian Shield, Red Sea Hills, NE Sudan

    NASA Astrophysics Data System (ADS)

    Bierlein, F. P.; McKeag, S.; Reynolds, N.; Bargmann, C. J.; Bullen, W.; Murphy, F. C.; Al-Athbah, H.; Brauhart, C.; Potma, W.; Meffre, S.; McKnight, S.

    2016-08-01

    Ongoing exploration in the Red Sea Hills of NE Sudan has led to the identification of a large alteration-mineralization system within a relatively undeformed Neoproterozoic intrusive-extrusive succession centered on Jebel Ohier. The style of mineralization, presence of an extensive stockwork vein network within a zoned potassic-propylitic-argillic-advanced argillic-altered system, a mineralization assemblage comprising magnetite-pyrite-chalcopyrite-bornite (±gold, silver and tellurides), and the recurrence of fertile mafic to intermediate magmatism in a developing convergent plate setting all point to a porphyry copper-gold association, analogous to major porphyry Cu-Au-Mo deposits in Phanerozoic supra-subduction settings such as the SW Pacific. Preliminary U-Pb age dating yielded a maximum constraint of c. 730 Ma for the emplacement of the stockwork system into a significantly older ( c. 800 Ma) volcanic edifice. The mineralization formed prior to regional deformation and accretion of the host terrane to a stable continental margin at by c. 700 Ma, thus ensuring preservation of the deposit. The Jebel Ohier deposit is interpreted as a relatively well-preserved, rare example of a Neoproterozoic porphyry Cu-Au system and the first porphyry Cu-Au deposit to be identified in the Arabian-Nubian Shield.

  12. Carbon cycling in primary production bottle incubations: inferences from grazing experiments and photosynthetic studies using 14C and 18O in the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Laws, Edward A.; Landry, Michael R.; Barber, Richard T.; Campbell, Lisa; Dickson, Mary-Lynn; Marra, John

    Estimates of photosynthesis based on the incorporation of 14C-labeled inorganic carbon into particulate carbon were compared to estimates of gross photosynthesis based on net O 2 production and the production of 18O2 from H218O during the US Joint Global Ocean Flux Study (US JGOFS) Arabian Sea process cruises. For samples incubated below the surface and at optical depths<3, the 14C uptake : gross photosynthesis ratio averaged 0.45±0.1. This result is in accord with theoretical considerations of the combined effects of the Mehler reaction, photorespiration, dark respiration, excretion, and grazing effects on the two estimates of photosynthesis. The 14C uptake : gross photosynthesis ratio was distinctly higher (0.62) for samples incubated at the surface. This result is likely due to UV light effects, since the O 2 and 14C incubations were done in quartz and polysulfone bottles, respectively. The 14C uptake : gross photosynthesis ratio was lower (0.31) for bottles incubated at optical depths>3. This result probably reflects an increase in the ratio of dark respiration to net photosynthesis in the vicinity of the compensation light level.

  13. Near-inertial kinetic energy budget of the mixed layer and shear evolution in the transition layer in the Arabian Sea during the monsoons

    NASA Astrophysics Data System (ADS)

    Majumder, Sudip; Tandon, Amit; Rudnick, Daniel L.; Thomas Farrar, J.

    2015-09-01

    We present the horizontal kinetic energy (KE) balance of near-inertial currents in the mixed layer and explain shear evolution in the transition layer using observations from a mooring at 15.26° N in the Arabian Sea during the southwest monsoon. The highly sheared and stratified transition layer at the mixed-layer base varies between 5 m and 35 m and correlates negatively with the wind stress. Results from the mixed layer near-inertial KE (NIKE) balance suggest that wind energy at times can energize the transition layer and at other times is fully utilized within the mixed layer. A simple two layer model is utilized to study the shear evolution in the transition layer and shown to match well with observations. The shear production in this model arises from alignment of wind stress and shear. Although the winds are unidirectional during the monsoon, the shear in the transition layer is predominantly near-inertial. The near-inertial shear bursts in the observations show the same phasing and magnitude at near-inertial frequencies as the wind-shear alignment term.

  14. The Jebel Ohier deposit—a newly discovered porphyry copper-gold system in the Neoproterozoic Arabian-Nubian Shield, Red Sea Hills, NE Sudan

    NASA Astrophysics Data System (ADS)

    Bierlein, F. P.; McKeag, S.; Reynolds, N.; Bargmann, C. J.; Bullen, W.; Murphy, F. C.; Al-Athbah, H.; Brauhart, C.; Potma, W.; Meffre, S.; McKnight, S.

    2015-12-01

    Ongoing exploration in the Red Sea Hills of NE Sudan has led to the identification of a large alteration-mineralization system within a relatively undeformed Neoproterozoic intrusive-extrusive succession centered on Jebel Ohier. The style of mineralization, presence of an extensive stockwork vein network within a zoned potassic-propylitic-argillic-advanced argillic-altered system, a mineralization assemblage comprising magnetite-pyrite-chalcopyrite-bornite (±gold, silver and tellurides), and the recurrence of fertile mafic to intermediate magmatism in a developing convergent plate setting all point to a porphyry copper-gold association, analogous to major porphyry Cu-Au-Mo deposits in Phanerozoic supra-subduction settings such as the SW Pacific. Preliminary U-Pb age dating yielded a maximum constraint of c. 730 Ma for the emplacement of the stockwork system into a significantly older (c. 800 Ma) volcanic edifice. The mineralization formed prior to regional deformation and accretion of the host terrane to a stable continental margin at by c. 700 Ma, thus ensuring preservation of the deposit. The Jebel Ohier deposit is interpreted as a relatively well-preserved, rare example of a Neoproterozoic porphyry Cu-Au system and the first porphyry Cu-Au deposit to be identified in the Arabian-Nubian Shield.

  15. Aspects of horizontal distribution and diet of myctophid fish in the Arabian Sea with reference to the deep water oxygen deficiency

    NASA Astrophysics Data System (ADS)

    Kinzer, Johannes; Böttger-Schnack, Ruth; Schulz, Knud

    Horizontal distribution of myctophid fishes were studied from two transects in the Arabian Sea in 1987. Species numbers exhibited a south-north decline in diversity, with only half of the fish taxa occupying the northeastern region. Diaphus arabicus was the dominant species both in the south and north. All recorded myctophid fish species migrate in a diel pattern, residing during daytime at depths of extremely low oxygen levels (<0.1 ml O 2 1 -1) and foraging in the oxygen-rich surface layer at night. Feeding patterns were determined for the six most abundant myctophid species. All species appeared to be opportunistic predators that prey on a comparatively narrow food spectrum consisting principally of small to medium sized copepods. Numerically, non-calanoid copepods (with Oncaea conifera and O. venusta dominating) made up to 70% of the diet of D. arabicus and Bolinichthys longipes. Of the 26 calanoid copepod species identified from the six myctophid taxa, the genera Euchaeta, Pleuromamma and Candacia generally dominated in the stomachs, with P. indica constituting between 21 and 95% (by numbers) of the calanoid copepod prey.

  16. Catch composition, reproductive biology and diet of the bramble shark Echinorhinus brucus (Squaliformes: Echinorhinidae) from the south-eastern Arabian Sea.

    PubMed

    Akhilesh, K V; Bineesh, K K; White, W T; Shanis, C P R; Hashim, M; Ganga, U; Pillai, N G K

    2013-11-01

    Fishery and biological data are presented for the poorly known bramble shark Echinorhinus brucus (Squaliformes: Echinorhinidae), from the deep waters of the south-eastern Arabian Sea. A total of 5318 individuals from by-catch landings of deep-water bottom set longlines, gillnets and shrimp trawl fisheries operating at depths of 200-1200 m were recorded between January 2008 and December 2011 at the Kochi Fisheries Harbour (Kerala). A total of 431 individuals, from 46 to 318 cm total length (L(T)) and 0·8 to 132 kg total mass (M(T)), were examined to determine biological data for this species. The LT at which 50% were mature (L(T)50) for females and males was estimated at 189 and 187 cm LT. Litter size ranged from 10 to 36 and size at birth was between 42 and 46 cm L(T). Dietary analysis of stomach contents revealed E. brucus feeds on a variety of prey including crustaceans (69% index of relative importance, I(RI)), teleosts (25·8% I(RI)), cephalopods (1·7% I(RI)) and elasmobranchs (0·7% I(RI)). This study provides the first detailed biological data for this species and also highlights the extent of the by-catch fishery for this species in Indian waters. PMID:24580658

  17. Metal concentrations in pearl oyster, Pinctada radiata, collected from Saudi Arabian coast of the Arabian Gulf

    SciTech Connect

    Sadig, M.; Alam, I.

    1989-01-01

    The Arabian Gulf is a shallow semi-closed water body. Several industrial complexes have been established along its coast line during the past decade. The effluent from these facilities is being discharged into the Gulf. These discharges pose potential hazards to the marine environment of the Arabian Gulf. The Saudi Arabian government is striving to protect the marine environment of the Gulf and has commissioned several studies to assess the damage from the industrial and municipal discharges. In these studies, marine organisms, for example, fish, clams, sea urchins, oysters, and plankton, along with sediments and seawater, have been analyzed for various pollutants. This study reports metal concentrations in pearl oysters collected from the Saudi Arabian coastal areas of the Arabian Gulf.

  18. Joint influence of the Indo-Pacific Warm Pool and Northern Arabian Sea Temperatures on the Indian Summer Monsoon in a Global Climate Model Simulation

    NASA Astrophysics Data System (ADS)

    Befort, Daniel J.; Leckebusch, Gregor C.; Cubasch, Ulrich

    2016-04-01

    Proxy-based studies confirmed that the Indian Summer Monsoon (ISM) shows large variations during the Holocene. These changes might be explained by changes in orbital conditions and solar insolation but are also thought to be associated to changes in oceanic conditions, e.g. over the Indo-Pacific-Warm-Pool region. However, due to the nature of these (proxy-based) analyses no conclusion about atmospheric circulation changes during dry and wet epochs are possible. Here, a fully-coupled global climate simulation (AOGCM) covering the past 6000 years is analysed regarding ISM variability. Several dry and wet epochs are found, the most striking around 2ka BP (dry) and 1.7ka BP (wet). As only orbital parameters change during integration, we expect these "shorter-term" changes to be associated with changes in oceanic conditions. During 1.7ka BP the sea surface temperatures (SST) over the Northern Arabian Sea (NARAB) are significantly warmer compared to 2ka BP, whereas cooler conditions are found over the western Pacific Ocean. Additionally, significant differences are found over large parts of the North Atlantic. To explain in how far these different ocean basins are responsible for anomalous conditions during 1.7ka BP, several sensitivity experiments with changed SST/SIC conditions are carried out. It is found that neither the SST's in the Pacific nor in the Indian Ocean are able to reproduce the anomalous rainfall and atmospheric circulation patterns during 1.7ka on its own. Instead, anomalous dry conditions during 2ka BP and wet conditions during 1.7ka BP are associated with a shift of the Indo-Pacific-Warm-Pool (IPWP) and simultaneous anomalous sea-surface temperatures over the NARAB region. Eventually, it is tested in how far this hypothesis holds true for other dry and wet events in the AOGCM data during the whole 6000 years. In general, a shift of the IPWP without anomalous SST conditions over the NARAB region (and vice versa) is not sufficient to cause long

  19. Evaluation of metal enrichment and trophic status on the basis of biogeochemical analysis of shelf sediments of the southeastern Arabian Sea, India

    NASA Astrophysics Data System (ADS)

    Cheriyan, Eldhose; Sreekanth, Athira; Mrudulrag, S. K.; Sujatha, C. H.

    2015-10-01

    The present study investigated the distribution of environmentally relevant metals and organic matter in the shelf sediments of the southeastern Arabian Sea using biogeochemical proxies for the assessment of environmental quality and trophic status. The distribution of metals in the study site followed the order: Fe>Mg>Pb>Ni>Mn>Co>Cu>Zn>Cd. High biological productivity associated with upwelling leads to significant accumulation of Cd higher than crustal abundance in the shelf region. The enrichment factor (EF) of metals demonstrate enrichment of Pb and Co which suggests the anthropogenic influence and not redox conditions. The sediment quality guidelines (SQG) in comparison with metal concentration revealed adverse effects, possibly occurring in marine benthic species. The spatial trend of metal enrichment along transects is appreciably controlled by the adsorption to fine grained sediments. The multivariate statistical analyses, such as correlations and principal component analysis (PCA) clearly indicated the control of texture, association of clay minerals in the degree of trace metal (Cd, Pb, Ni and Co) contamination from anthropogenic as well as natural sources. Low levels of Zn, preferably display scavenging by Fe/Mn metal oxides. Biochemical descriptors in sediments indicated meso-oligotrophic conditions prevailing in the summer monsoon. The ratios among various biogeochemical parameters such as total organic carbon/total nitrogen (TOC/TN<10), protein/carbohydrate (PRT/CHO<1) displayed that the organic matter deposited of marine origin which is relatively old with potentially low nutritional value. The close relationship between biochemical components and phytopigments suggest a major contribution of autochthonous phytodetritus derived organic matter. The study provides important information about sediment biogeochemistry and metal contamination from a potential fishery zone of Indian exclusive economic zone.

  20. Trophic organisation and predator-prey interactions among commercially exploited demersal finfishes in the coastal waters of the southeastern Arabian Sea

    NASA Astrophysics Data System (ADS)

    Abdurahiman, K. P.; Nayak, T. H.; Zacharia, P. U.; Mohamed, K. S.

    2010-05-01

    Trophic interactions in commercially exploited demersal finfishes in the southeastern Arabian Sea of India were studied to understand trophic organization with emphasis on ontogenic diet shifts within the marine food web. In total, the contents of 4716 stomachs were examined from which 78 prey items were identified. Crustaceans and fishes were the major prey groups to most of the fishes. Based on cluster analysis of predator feeding similarities and ontogenic diet shift within each predator, four major trophic guilds and many sub-guilds were identified. The first guild 'detritus feeders' included all size groups of Cynoglossus macrostomus, Pampus argenteus, Leiognathus bindus and Priacanthus hamrur. Guild two, named 'Shrimp feeders', was the largest guild identified and included all size groups of Rhynchobatus djiddensis and Nemipterus mesoprion, medium and large Nemipterus japonicus, P. hamrur and Grammoplites suppositus, small and medium Otolithes cuvieri and small Lactarius lactarius. Guild three, named 'crab and squilla feeders', consisted of few predators. The fourth trophic guild, 'piscivores', was mainly made up of larger size groups of all predators and all size groups of Pseudorhombus arsius and Carcharhinus limbatus. The mean diet breadth and mean trophic level showed strong correlation with ontogenic diet shift. The mean trophic level varied from 2.2 ± 0.1 in large L. bindus to 4.6 ± 0.2 in large Epinephelus diacanthus and the diet breadth from 1.4 ± 0.3 in medium P. argenteus to 8.3 ± 0.2 in medium N. japonicus. Overall, the present study showed that predators in the ecosystem have a strong feeding preference for the sergestid shrimp Acetes indicus, penaeid shrimps, epibenthic crabs and detritus.

  1. Carbon and Nitrogen Uptake of Calcareous Benthic Foraminifera along a Depth-Related Oxygen Gradient in the OMZ of the Arabian Sea

    PubMed Central

    Enge, Annekatrin J.; Wukovits, Julia; Wanek, Wolfgang; Watzka, Margarete; Witte, Ursula F. M.; Hunter, William R.; Heinz, Petra

    2016-01-01

    Foraminifera are an important faunal element of the benthos in oxygen-depleted settings such as Oxygen Minimum Zones (OMZs) where they can play a relevant role in the processing of phytodetritus. We investigated the uptake of phytodetritus (labeled with 13C and 15N) by calcareous foraminifera in the 0–1 cm sediment horizon under different oxygen concentrations within the OMZ in the eastern Arabian Sea. The in situ tracer experiments were carried out along a depth transect on the Indian margin over a period of 4 to 10 days. The uptake of phytodetrital carbon within 4 days by all investigated species shows that phytodetritus is a relevant food source for foraminifera in OMZ sediments. The decrease of total carbon uptake from 540 to 1100 m suggests a higher demand for carbon by species in the low-oxygen core region of the OMZ or less food competition with macrofauna. Especially Uvigerinids showed high uptake of phytodetrital carbon at the lowest oxygenated site. Variation in the ratio of phytodetrital carbon to nitrogen between species and sites indicates that foraminiferal carbon and nitrogen use can be decoupled and different nutritional demands are found between species. Lower ratio of phytodetrital carbon and nitrogen at 540 m could hint for greater demand or storage of food-based nitrogen, ingestion, or hosting of bacteria under almost anoxic conditions. Shifts in the foraminiferal assemblage structure (controlled by oxygen or food availability) and in the presence of other benthic organisms are likely to account for observed changes in the processing of phytodetritus in the different OMZ habitats. Foraminifera dominate the short-term processing of phytodetritus in the OMZ core but are less important in the lower OMZ boundary region of the Indian margin as biological interactions and species distribution of foraminifera change with depth and oxygen levels. PMID:26903959

  2. Southern Hemisphere imprint for Indo-Asian summer monsoons during the last glacial period as revealed by Arabian Sea productivity records

    NASA Astrophysics Data System (ADS)

    Caley, T.; Zaragosi, S.; Bourget, J.; Martinez, P.; Malaizé, B.; Eynaud, F.; Rossignol, L.; Garlan, T.; Ellouz-Zimmermann, N.

    2013-06-01

    The monsoon is one of the most important climatic phenomena: it promotes inter-hemispheric exchange of energy and affects the economical prosperity of several countries exposed to its seasonal seesaw. Previous studies in both the Indian and Asian monsoon systems have suggested a dominant north hemispheric (NH) control on summer monsoon dynamics at the scale of suborbital-millennial climatic changes, while the forcing/response of Indian and Asian monsoons at the orbital scale remains a matter of debate. Here nine marine sediment cores distributed across the whole Arabian Sea are used to build a regional surface marine productivity signal. The productivity signal is driven by the intensity of Indian summer monsoon winds. Results demonstrate the existence of an imprint of suborbital Southern Hemisphere (SH) temperature changes (i.e., Antarctica) on the Indian summer monsoon during the last glacial period, challenging the traditional and exclusive NH forcing hypothesis. Meanwhile, during the last deglaciation, the NH plays a more significant role. The δ18O signal recorded in the Asian monsoon speleothem records could be exported by winds from the Indian summer monsoon region, as recently proposed in modelling exercise, explaining the SH signature observed in Asian cave speleothems. Contrary to the view of a passive response of Indian and Asian monsoons to NH anomalies, the present results strongly suggest that the Indo-Asian summer monsoon plays an active role in amplifying millennial inter-hemispheric asymmetric patterns. Additionally, this study helps to decipher the observed differences between Indian and Asian-speleothem monsoonal records at the orbital-precession scale.

  3. Southern Hemisphere imprint for Indo-Asian summer monsoons during the last glacial period as revealed by Arabian Sea productivity records

    NASA Astrophysics Data System (ADS)

    Caley, T.; Zaragosi, S.; Bourget, J.; Martinez, P.; Malaizé, B.; Eynaud, F.; Rossignol, L.; Garlan, T.; Ellouz-Zimmermann, N.

    2013-11-01

    The monsoon is one of the most important climatic phenomena: it promotes inter-hemispheric exchange of energy and affects the economical prosperity of several countries exposed to its seasonal seesaw. Previous studies in both the Indian and Asian monsoon systems have generally suggested a dominant northern hemispheric (NH) control on summer monsoon dynamics at the scale of suborbital-millennial climatic changes, while the forcing/response of Indian and Asian monsoons at the orbital scale remains a matter of debate. Here, six marine sediment cores distributed across the whole Arabian Sea are used to build a regional surface marine productivity signal. The productivity signal is driven by the intensity of Indian summer monsoon winds. Our results demonstrate the existence of an imprint of suborbital southern hemispheric (SH) temperature changes (i.e. Antarctica) on the Indian summer monsoon during the last glacial period that is generally not recognized. During the last deglaciation, the NH played a more significant role. This suggests that fluctuations in the Indian monsoon are better explained in a bipolar context. The δ18O signal recorded in the Asian monsoon speleothem records could be exported by winds from the Indian summer monsoon region, as recently proposed in modelling exercise, explaining the SH signature observed in Asian cave speleothems. Contrary to the view of a passive response of Indian and Asian monsoons to NH anomalies, the present results appear to suggest that the Indo-Asian summer monsoon plays an active role in amplifying millennial inter-hemispheric asymmetric patterns. Additionally, this study confirms previously observed differences between Indian and Asian speleothem monsoonal records at the orbital-precession scale.

  4. Evaluation of changes in macrobenthic standing stock and polychaete community structure along the south eastern Arabian Sea shelf during the monsoon trawl-ban

    NASA Astrophysics Data System (ADS)

    Abdul Jaleel, K. U.; Parameswaran, Usha V.; Gopal, Aiswarya; Khader, Chippy; Ganesh, T.; Sanjeevan, V. N.; Shunmugaraj, T.; Vijayan, Anil Kumar; Gupta, G. V. M.

    2015-07-01

    The south eastern Arabian Sea is characterized by moderate coastal upwelling, high biological production and subsurface oxygen depletion during the southwest monsoon (June-September). Concurrently, a seasonal closure to trawling activities (15th June-31st July) is implemented here, as a sustainable ecosystem management practise. The effects of monsoon driven environmental changes and consequences of trawling cessation on macrofauna were assessed, based on surveys at 12 sites (30-200 m) preceding and during different phases of the southwest monsoon. Macrofaunal density and biomass increased considerably towards the mid and late monsoon along the inner shelf (30-50 m) where trawling is intense, while no temporal changes were observed along the outer shelf (100-200 m). Density increased four-folds at the 30 m contour and three-folds at 50 m, while biomass nearly doubled at both depths, reflecting a marked increase in density of polychaetes (61-87% of macrofauna). The disproportionate increase in faunal density and biomass along the inner shelf (30-50 m) was due to abundance of juvenile polychaetes and dominance of small-sized opportunists towards late monsoon (August-September). A concurrent hike in nominal species count of polychaetes was also observed in the study area. The increase in polychaete standing stock and high density of planktonic larvae during onset and peak monsoon, coupled with occurrence of juveniles as well as gamete-bearing adults in sediments, indicates that the southwest monsoon is a peak breeding season for the dominant polychaetes in the region. The trawl-ban during this period facilitates the recoupment of benthos by maximising spawning success and larval settlement, thereby enhancing overall ecosystem integrity.

  5. Carbon and Nitrogen Uptake of Calcareous Benthic Foraminifera along a Depth-Related Oxygen Gradient in the OMZ of the Arabian Sea.

    PubMed

    Enge, Annekatrin J; Wukovits, Julia; Wanek, Wolfgang; Watzka, Margarete; Witte, Ursula F M; Hunter, William R; Heinz, Petra

    2016-01-01

    Foraminifera are an important faunal element of the benthos in oxygen-depleted settings such as Oxygen Minimum Zones (OMZs) where they can play a relevant role in the processing of phytodetritus. We investigated the uptake of phytodetritus (labeled with (13)C and (15)N) by calcareous foraminifera in the 0-1 cm sediment horizon under different oxygen concentrations within the OMZ in the eastern Arabian Sea. The in situ tracer experiments were carried out along a depth transect on the Indian margin over a period of 4 to 10 days. The uptake of phytodetrital carbon within 4 days by all investigated species shows that phytodetritus is a relevant food source for foraminifera in OMZ sediments. The decrease of total carbon uptake from 540 to 1100 m suggests a higher demand for carbon by species in the low-oxygen core region of the OMZ or less food competition with macrofauna. Especially Uvigerinids showed high uptake of phytodetrital carbon at the lowest oxygenated site. Variation in the ratio of phytodetrital carbon to nitrogen between species and sites indicates that foraminiferal carbon and nitrogen use can be decoupled and different nutritional demands are found between species. Lower ratio of phytodetrital carbon and nitrogen at 540 m could hint for greater demand or storage of food-based nitrogen, ingestion, or hosting of bacteria under almost anoxic conditions. Shifts in the foraminiferal assemblage structure (controlled by oxygen or food availability) and in the presence of other benthic organisms are likely to account for observed changes in the processing of phytodetritus in the different OMZ habitats. Foraminifera dominate the short-term processing of phytodetritus in the OMZ core but are less important in the lower OMZ boundary region of the Indian margin as biological interactions and species distribution of foraminifera change with depth and oxygen levels. PMID:26903959

  6. The abundance of functional genes, cbbL, nifH, amoA and apsA, and bacterial community structure of intertidal soil from Arabian Sea.

    PubMed

    Keshri, Jitendra; Yousuf, Basit; Mishra, Avinash; Jha, Bhavanath

    2015-06-01

    The Gulf of Cambay is a trumpet-shaped inlet of the Arabian Sea, located along the west coast of India and confronts a high tidal range with strong water currents. The region belongs to a semi-arid zone and saline alkaline intertidal soils are considered biologically extreme. The selected four soil types (S1-S4) were affected by salinity, alkalinity and sodicity. Soil salinity ranged from 20 to 126 dS/m, soil pH 8.6-10.0 with high sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP). Abundance of the key functional genes like cbbL, nifH, amoA and apsA involved in biogeochemical cycling were targeted using qPCR, which varied from (2.36 ± 0.03) × 10(4) to (2.87 ± 0.26) × 10(8), (1.18 ± 0.28) × 10(6) to (1.01 ± 0.26) × 10(9), (1.41 ± 0.21) × 10(6) to (1.29 ± 0.05) × 10(8) and (8.47 ± 0.23) × 10(4) to (1.73 ± 0.01) × 10(6) per gram dry weight, respectively. The microbial community structure revealed that soils S1 and S3 were dominated by phylum Firmicutes whereas S4 and S2 showed an abundance of Proteobacterial clones. These soils also represented Bacteroidetes, Chloroflexi, Actinobacteria, Planctomycetes and Acidobacteria clones. Molecular phylogeny showed a significant variation in the bacterial community distribution among the intertidal soil types. A high number of novel taxonomic units were observed which makes the intertidal zone a unique reservoir of unidentified bacterial taxa that may be explored further. PMID:25862282

  7. Calappid and leucosiid crabs (Crustacea: Decapoda: Brachyura) from Kerala, India, with the description of a new species of Mursia Desmarest, 1823, from the Arabian Sea and redescription of M. bicristimana Alcock & Anderson, 1894.

    PubMed

    Kumar, Biju A; Kumar, M Sushil; Galil, Bella S

    2013-01-01

    Eleven species of calappid and leucosiid crabs were identified from by-catch landed by trawlers at four fishing ports in Kerala, India that were surveyed in 2007 and supplemented by material obtained in January 2013. Four species are reported for the first time from India, six are new records for Kerala. The status of Mursia bicristimana Alcock & Anderson, 1894, is clarified and the species redescribed. A new species of Mursia is described from the Gulf of Aden, Arabian Sea.  PMID:25113495

  8. Impact of sedimentary degradation and deep water column production on GDGT abundance and distribution in surface sediments in the Arabian Sea: Implications for the TEX86 paleothermometer

    NASA Astrophysics Data System (ADS)

    Lengger, Sabine K.; Hopmans, Ellen C.; Sinninghe Damsté, Jaap S.; Schouten, Stefan

    2014-10-01

    The TEX86 is a widely used paleotemperature proxy based on isoprenoid glycerol dibiphytanyl glycerol tetraethers (GDGTs) produced by Thaumarchaeota. Archaeal membranes are composed of GDGTs with polar head groups (IPL-GDGTs), most of which are expected to be degraded completely or transformed into more recalcitrant core lipid (CL)-GDGTs upon cell lysis. Here, we examined the differences in concentration and distribution of core lipid (CL)- and intact polar lipid (IPL)-GDGTs in surface sediments at different deposition depths, and different oxygen bottom water concentrations (<3-83 μmol L-1). Surface sediments were sampled from 900 to 3000 m depth on a seamount (Murray Ridge), whose summit protrudes into the oxygen minimum zone of the Arabian Sea. Concentrations of organic carbon, IPL- and CL-GDGTs decreased linearly with increasing maximum residence time in the oxic zone of the sediment (tOZ), suggesting increasing sedimentary degradation of organic matter and GDGTs. IPL-GDGT-0 was the only exception and increased with tOZ, indicating that this GDGT was probably produced in situ in the surface sediment. Concentrations of crenarchaeol with glycosidic headgroups decreased with increasing tOZ, while crenarchaeol with a hexose, phosphohexose head (HPH) group, in contrast, showed an increase with increasing tOZ, indicating that the concentration of HPH crenarchaeol was primarily determined by in situ production in surficial sediments. TEX86 values of both IPL-derived GDGTs and CL-GDGTs decreased by ∼0.08 units with increasing water depth, in spite of the sea surface temperatures being identical for the restricted area studied. In situ production in sediments could be excluded as the main cause, due to the slow production rates of GDGTs in sediments, and previous observations of the same trends in TEX86 in sediment trap material. Instead, the incorporation of GDGTs produced in the oxygen minimum zone (with high TEX86 values) and their preferential degradation during

  9. Flux and accumulation of sedimentary particles off the continental slope of Pakistan: a comparison of water column and seafloor estimates from the oxygen minimum zone, NE Arabian Sea

    NASA Astrophysics Data System (ADS)

    Schulz, H.; von Rad, U.

    2013-07-01

    Due to the lack of bioturbation, the laminated muds from the oxygen-minimum zone (OMZ) off Pakistan provide a unique opportunity to precisely determine the vertical and lateral sediment fluxes in the near shore part of the northeastern Arabian Sea, and to explore the effects of the margin topography and the low oxygen conditions on the accumulation of organic matter and other particles. West of Karachi, in the Hab river area of EPT and WPT (Eastern and Western PAKOMIN Traps), 16 short sediment profiles from water depths between 250 m and 1970 m on a depth transect crossing the OMZ (~ 120 to ~ 1200 m water depth) were investigated, and correlated on the basis of a thick, light-gray- to reddish-colored turbidite layer. Varve counting yielded a date for this layer of AD 1905 to 1888. We adopted the young age which agrees with 210Pb- dating, and used this isochronous stratigraphic marker bed to calculate sediment accumulation rates, that we could directly compare with the flux rates from the sediment traps installed within the water column above. All traps in the area show exceptionally high, pulsed winter fluxes of up to 5000 mg m-2 d-1 in this margin environment. The lithic flux at the sea floor is as high as 4000 mg m-2 d-1 , and agrees remarkably well with the bulk winter flux of material. This holds as well for the individual bulk components (organic carbon, calcium carbonate, opal, lithic fraction). However, the high winter flux events (HFE) by their extreme mass of remobilized matter terminated the recording in the shallow traps by clogging the funnels. Based on our comparisons, we argue that HFE for the past 5000 yr most likely occurred as regular events within the upper OMZ off Pakistan. Coarse fraction and foraminiferal accumulation rates from sediment surface samples along the Hab transect show distribution patterns that seem to be a function of water depth and distance from the shelf. Some of these sediment fractions show sudden shifts at the lower boundary

  10. Regional variation in the structure and function of parrotfishes on Arabian reefs.

    PubMed

    Hoey, Andrew S; Feary, David A; Burt, John A; Vaughan, Grace; Pratchett, Morgan S; Berumen, Michael L

    2016-04-30

    Parrotfishes (f. Labridae) are a unique and ubiquitous group of herbivorous reef fishes. We compared the distribution and ecosystem function (grazing and erosion) of parrotfishes across 75 reefs in Arabia. Our results revealed marked regional differences in the abundance, and taxonomic and functional composition of parrotfishes between the Red Sea, Arabian Sea, and Arabian Gulf. High densities and diversity of parrotfishes, and high rates of grazing (210% year(-1)) and erosion (1.57 kgm(-2)year(-1)) characterised Red Sea reefs. Despite Arabian Sea and Red Sea reefs having broadly comparable abundances of parrotfishes, estimates of grazing (150% year(-1)) and erosion (0.43 kgm(-2)year(-1)) were markedly lower in the Arabian Sea. Parrotfishes were extremely rare within the southern Arabian Gulf, and as such rates of grazing and erosion were negligible. This regional variation in abundance and functional composition of parrotfishes appears to be related to local environmental conditions. PMID:26608505

  11. Laminated Sediments of the Northern Arabian Sea: Tracking Climatic and Human Impacts on Late Holocene Erosion and Weathering Intensities in SW Asia

    NASA Astrophysics Data System (ADS)

    Forke, Sven; Rixen, Tim

    2014-05-01

    In the face of recent climate change, the need of understanding the mechanisms of climate variability increases continuously. However, most palaeo-climatic and -oceanographic records are restricted to timescales that have too low resolutions to take immediate appeal. Besides tree ring, speleothem and coral records, laminated lacustrine and marine sediments offer the required temporal resolution of decadal and also interannual scales to decipher climatic changes properly. Laminated sediments of the northern Arabian Sea provide such an excellent high-resolution archive for marine and terrestrial environmental changes. Fluvial and aeolian transported detritus are the major constituents of the sediment succession and give good indications of natural climatic and human impact by integrating precipitation and erosion signals of large continental areas of SW Asia. We present data of the seasonal laminated sediment core SO130-275KL (Lat 24°82', Lon 65°91'; 782 mbsl) from the oxygen minimum zone (OMZ) off Karachi, eastern Pakistan. The sediment core is well dated by varve counting and AMS 14C methods, and comprises the late Holocene period (ca. 5,000 years). We applied grain-size analysis in combination with the chemical index on alteration (CIA) on the lithogenic matter portion of the sediment in order to investigate the regional impact of climatic variability and human land use change on soil erosion, soil transport, and silicate weathering. Our data implies a significant distal and proximal aeolian dust contribution to both lithotypes, which were probably re-deposited in combination with riverine sediment load. In doing so, strong aeolian-fluvial interactions as observed in other semi-arid and arid environments of today are very obvious. Fluvial mud and distal aeolian dust percentages show a near-parallel increase after ca. 2,700 years B.P. in combination with reduction of coastal dune activity. Therefore, we assume an increase in winter precipitation intensity due to

  12. A multiproxy approach to understanding the "enhanced" flux of organic matter through the oxygen-deficient waters of the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Keil, Richard G.; Neibauer, Jacquelyn A.; Biladeau, Christina; van der Elst, Kelsey; Devol, Allan H.

    2016-04-01

    Free-drifting sediment net traps were deployed 14 times at depths between 80 and 500 m for 1-3 days each during the late monsoon-intermonsoon transition in the central Arabian Sea. Two locations (19.5 and 15.5° N) were within the permanently oxygen-deficient zone (ODZ), and a third (11° N) had a shallow and thin oxygen minimum. The secondary nitrite maximum, which serves as a tracer of the ODZ, thinned from ˜ 250 m thick at stations 19.5 and 15.5° N to ˜ 50 m thick at station 11° N. Overall, organic carbon fluxes ranged from 13.2 g m2 yr-1 at 80 m to a minimum of 1.1 g m2 yr-1 at 500 m. Fluxes at the more oxygenated 11° N station attenuate faster than within the permanent ODZ. Martin curve attenuation coefficients for 19.5 and 15.5° N are respectively 0.59 and 0.63 and for 11° N it is 0.98. At least six potential mechanisms might explain why particles sinking through the ODZ are more effectively transferred to depth: (M1) oxygen effects, (M2) microbial loop efficiencies and chemoautotrophy, (M3) changes in zooplankton dynamics, (M4) additions of ballast that might sorb and protect organic matter from decay (M4a) or change sinking speeds (M4b), (M5) inputs of refractory organic matter and (M6) temperature effects. These mechanisms are intertwined, and they were explored using a combination of mineral (XPS) and organic matter characterizations of the sinking material, shipboard incubation experiments, and evaluations of existing literature. Direct evidence was found supporting an oxygen effect and/or changes in the efficiency of the microbial loop including the addition of chemoautotrophic carbon to the sinking flux in the upper 500 m. Less direct evidence was found for the other potential mechanisms. A simple conceptual model consistent with our and other recent data suggests that the upper ODZ microbial community determines the initial flux attenuation, and that zooplankton and sinking speed become more important deeper in the water column. The exact

  13. Red Sea

    Atmospheric Science Data Center

    2013-04-16

    article title:  The Red Sea     View Larger Image ... Imaging SpectroRadiometer (MISR) image of the Red Sea was acquired on August 13, 2000. Located between the East African coast and the Saudi Arabian peninsula, the Red Sea got its name because the blooms of a type of algae,  Trichodesmium ...

  14. Lamellodiscus aff. euzeti Diamanka, Boudaya, Toguebaye & Pariselle, 2011 (Monogenea: Diplectanidae) from the gills of Cheimerius nufar (Valenciennes) (Pisces: Sparidae) collected in the Arabian Sea, with comments on the distribution, specificity and historical biogeography of Lamellodiscus spp.

    PubMed

    Machkewskyi, Volodymyr K; Dmitrieva, Evgenija V; Gibson, David I; Al-Jufaili, Sara

    2014-11-01

    Specimens of Lamellodiscus Johnston & Tiegs, 1922 (Monogenea: Diplectanidae) were collected from the gills of Cheimerius nufar (Valenciennes) (Sparidae) in the Arabian Sea. All of these parasites belonged to one and the same species, which is morphologically very close to L. euzeti Diamanka, Boudaya, Toguebaye & Pariselle, 2011. A different host, distant locality and small morphological differences compared with the original description of L. euzeti acted as a stimulus for a detailed redescription. The specimens from the Arabian Sea differ slightly in the details of the male copulatory organ (MCO) from the type-specimens of L. euzeti, which were re-examined, and from the respective drawings in its original description. Such differences include a longer inner process of the large element of the accessory piece associated with the proximal part of the copulatory tube, a longer point on the small element of the accessory piece associated with the distal part of the copulatory tube, and the presence of a smooth or slightly folded inner margin of this element rather than structures resembling spines which occur in the type-specimens of L. euzeti. Therefore, the present specimens infecting C. nufar in the Indo-Pacific may represent a different, but morphologically very similar species to the Atlantic form L. euzeti; consequently, they are recognised here as Lamellodiscus aff. euzeti. This form belongs to the 'ignoratus s. str.' subgroup of the genus. The composition of this subgroup is redefined to comprise 17 species, including L. corallinus Paperna, 1965 but excluding L. acanthopagri Roubal, 1981, and the morphology of the MCO of representatives of this group is clarified. A link between the diversity of Lamellodiscus species and the ancestral origin of present-day sparid species in the Tethys Sea is suggested. It is shown that Lamellodiscus spp. exhibit rather high levels of specificity to their hosts, since half of them parasitise only a single host species and c.90

  15. Acoustic Doppler current profiling from the JGOFS Arabian Sea cruises aboard the RV T.G. THOMPSON: TN043, January 8, 1995--February 4, 1995; TN044, February 8, 1995--February 25, 1995; TN045, March 14, 1995--April 10, 1995; TN046, April 14, 1995--April 29, 1995

    SciTech Connect

    Flagg, C.N.; Kim, H.S.; Shi, Y.

    1995-09-01

    Acoustic Doppler current profiler (ADCP) data from the R/V T.G. THOMPSON is part of the core data for the US JGOFS Arabian Sea project along with hydrographic and nutrient data. Seventeen cruises on the THOMPSON are scheduled to take place between September 1994 and January 1996. This is the second in a series of data reports covering the ADCP data from the Arabian Sea JGOFS cruises TNO43 through TNO46. ADCP data are being collected on all the JGOFS Arabian Sea cruises using an autonomous data acquisition system developed for ship-of-opportunity cruises. This system, referred to as the AutoADCP, makes it possible to collect the ADCP data without the constant monitoring usually necessary and assures constant data coverage and uniform data quality. This data report presents ADCP results from the second group of four JGOFS cruises, TNO43 through TNO46, concentrating on the data collection and processing methods. The ADCP data itself reside in a CODAS data base at Brookhaven National Laboratory and is generally available to JGOFS investigators through contact with the authors. The CODAS data base and associated ADCP processing software were developed over a number of years by Eric Firing and his group at the University of Hawaii. The CODAS software is shareware available for PC`s or Unix computers and is the single most widely used ADCP processing program for ship mounted units.

  16. High-resolution Sr/Ca ratios in a Porites lutea coral from Lakshadweep Archipelago, southeast Arabian Sea: An example from a region experiencing steady rise in the reef temperature

    NASA Astrophysics Data System (ADS)

    Sagar, Netramani; Hetzinger, Steffen; Pfeiffer, Miriam; Masood Ahmad, Syed; Dullo, Wolf-Christian; Garbe-Schönberg, Dieter

    2016-01-01

    Here we present the first record of Sr/Ca variability in a massive Porites lutea coral from the Lakshadweep Archipelago, Arabian Sea. The annual mean sea surface temperature (SST) in this region and the surrounding areas has increased steadily in the recent past. During some major El Niño events, SSTs are even higher, imposing additional thermal-stress on corals, episodically leading to coral bleaching. We infer from the coral-Sr/Ca record (1981-2008) that during some of these events high and persistent SSTs lead to a dampening of the temperature signal in coral-Sr/Ca, impairing the coral's ability to record full scale warming. Thus, coral-Sr/Ca may provide a history of past El Niño Southern-Oscillation (ENSO) induced thermal-stress episodes, which are a recurrent feature also seen in cross-spectral analysis between coral-Sr/Ca and the Nino3.4 index. Despite the impact of episodical thermal-stress during major El Niño events, our coral proxy faithfully records the seasonal monsoon-induced summer cooling on the order of ˜2.3°C. Calibration of coral-Sr/Ca with instrumental grid-SST data shows significant correlation to regional SST and monsoon variability. Hence, massive Porites corals of this region are highly valuable archives for reconstructing long-term changes in SST, strongly influenced by monsoon variability on seasonal scales. More importantly, our data show that this site with increasing SST is an ideal location for testing the future effects of the projected anthropogenic SST increase on coral reefs that are already under thermal-stress worldwide.

  17. Sediment sound velocities from sonobuoys: Arabian Fan

    NASA Astrophysics Data System (ADS)

    Bachman, Richard T.; Hamilton, Edwin L.

    1980-02-01

    Eight variable-angle seismic reflection stations in the Arabian Fan, Northwestern Indian Ocean, provided 40 determinations of sound velocity in sediment and sedimentary rock. Sound velocity in the homogeneous, largely terrigenous fan increases smoothly with depth. Regression analysis yielded the velocity-time relationship V (km/s) = 1.510 + 1.863t, where V is instantaneous velocity and t is one-way travel time below the sea floor to 1 s. The velocity-depth function is V (km/s) = 1.510 + 1.200h; - 0.253h2 + 0.034h3, where h is subbottom depth in km.

  18. Sediment sound velocities from sonobuoys: Arabian fan

    SciTech Connect

    Bachman, R.T.; Hamilton, E.L.

    1980-02-10

    Eight variable-angle seismic reflection stations in the Arabian Fan, Northwestern Indian Ocean, provided 40 determinations of sound velocity in sediment and sedimentary rock. Sound velocity in the homogeneous, largely terrigenous fan increases smoothly with depth. Regression analysis yielded the velocity-time relationship V (km/s)=1.510+1.863t, where V is instantaneous velocity and t is one-way travel time below the sea floor to 1 s. The velocity-depth function is V (km/s)=1.510+1.200h-0.253h/sup 2/+ 0.034h/sup 3/, where h is subbottom depth in km.

  19. Intact polar and core glycerol dibiphytanyl glycerol tetraether lipids in the Arabian Sea oxygen minimum zone. Part II: Selective preservation and degradation in sediments and consequences for the TEX86

    NASA Astrophysics Data System (ADS)

    Lengger, Sabine K.; Hopmans, Ellen C.; Reichart, Gert-Jan; Nierop, Klaas G. J.; Sinninghe Damsté, Jaap S.; Schouten, Stefan

    2012-12-01

    The TEX86 is a proxy based on a ratio of pelagic archaeal glycerol dibiphytanyl glycerol tetraether lipids (GDGTs), and used for estimating past sea water temperatures. Concerns exist that in situ production of GDGTs lipids by sedimentary Archaea may affect its validity. In this study, we investigated the influence of benthic GDGT production on the TEX86 by analyzing the concentrations and distributions of GDGTs present as intact polar lipids (IPLs) and as core lipids (CLs) in three sediment cores deposited under contrasting redox conditions across a depth range from 900 to 3000 m below sea level in and below the Arabian Sea oxygen minimum zone (OMZ). Direct analysis of IPLs with crenarchaeol as CL via HPLC/ESI-MS2 revealed that surface sediments in the OMZ were relatively depleted in the phospholipid hexose, phosphohexose (HPH)-crenarchaeol compared to suspended particulate matter from the water column, suggesting preferential and rapid degradation of this IPL. In sediment cores recovered from deeper, more oxic environments, concentrations of HPH-crenarchaeol peaked at the surface, probably due to in situ production by ammonia-oxidizing Archaea, followed by a rapid decrease with increasing depth. No surface maximum was observed in the sediment core from within the OMZ. In contrast, the glycolipids, monohexose-crenarchaeol and dihexose-crenarchaeol, did not change in concentration with depth in the sediment, indicating that they were relatively well preserved and likely mostly derived from fossil pelagic GDGTs. These results suggest that phospholipids are more sensitive to degradation, while glycolipids might be preserved over longer time scales, in line with previous incubation and modeling studies. Furthermore, in situ produced IPL-GDGTs did not accumulate as IPLs, and did not influence the CL-TEX86. This suggests that in-situ produced GDGT lipids were more susceptible to degradation than fossil CL and IPL and did not accumulate as CL. In agreement, no

  20. Intact polar and core glycerol dibiphytanyl glycerol tetraether lipids in the Arabian Sea oxygen minimum zone: I. Selective preservation and degradation in the water column and consequences for the TEX86

    NASA Astrophysics Data System (ADS)

    Schouten, Stefan; Pitcher, Angela; Hopmans, Ellen C.; Villanueva, Laura; van Bleijswijk, Judith; Sinninghe Damsté, Jaap S.

    2012-12-01

    Glycerol dibiphytanyl glycerol tetraether lipids (GDGTs) have proven to be important biomarker lipids for specific archaeal lineages and their distribution is used as a paleotemperature proxy. In this study, we analyzed GDGTs in suspended particles in the water column of the Arabian Sea at different positions above, in and below the oxygen minimum zone (OMZ). GDGTs, both as intact polar lipid (IPL) and as core lipids, were detected throughout the water column but were most abundant at the upper part of the OMZ. Core lipid GDGTs, derived from non-living organic matter, were always much more abundant than GDGTs released by acid hydrolysis of an IPL fraction (IPL-derived GDGTs). Comparisons with 16S rRNA gene abundance showed that likely only 1-14% of total archaeal cells present were caught on the 0.7 μm filter used for lipid analysis. Despite this undersampling, the depth profiles of crenarchaeol core lipid with a phosphohexose or dihexose head group match previously reported profiles of (expressed) genes specific for ammonia-oxidizing Thaumarchaeota, such as 16S rDNA and amoA. In contrast, the crenarchaeol with a hexose head group as well as core lipid and IPL-derived crenarchaeol matched the genetic depth profiles much less, suggesting a contribution of GDGTs from non-living matter. TEX86 values of both core lipid and IPL-derived GDGTs increased from surface waters to the core of the OMZ, below which they decreased again, and did not correlate with in situ water temperature. In contrast, TEX86 values of IPL-derived GDGTs correlated well the relative amount of glycosidic GDGTs and were consistently higher than that those of CL GDGTs. This suggests that selective preservation of glycosidic GDGTs may mask TEX86 values of in situ produced GDGTs in deep marine waters.

  1. Distribution of Permo-Carboniferous clastics of Greater Arabian basin

    SciTech Connect

    Al-Laboun, A.A.

    1987-05-01

    Strikingly correlative sequences of sediments composed of sandstones, siltstones, shales, and thin argillaceous carbonate beds are present, practically everywhere, underlying the Late Permian carbonates in the Greater Arabian basin. The Greater Arabian basin as defined here occupies the broad Arabian Shelf that borders the Arabian shield. This basin is composed of several smaller basins. These clastics are exposed as thin bands and scattered small exposures in several localities around the margins of the basin. The Permo-Carboniferous clastics are represented by the Unayzah Formation of Arabia, the Doubayat Group of Syria, the Hazro Formation of southeast Turkey, the Ga'arah Formation of Iraq, the Faraghan Formation of southwest Iran, and the Haushi Group of Oman. A Late Carboniferous-Early Permian age is assigned to these clastics because they contain fossil plants and palynomorphs. These sediments represent time-transgressive fluctuating sea deposits following a phase of regional emergence, erosion, and structural disturbance which preceded the Permian transgression. The basal contact of these clastics is marked by a well-pronounced angular unconformity with various older units, ranging in age from early Carboniferous to late Precambrian. This regional unconformity is probably related to the Hercynian movements. The upper contact is conformable with the Permian carbonates. The porous sandstones of the Permo-Carboniferous sediments are important hydrocarbon exploration targets. These reservoir rocks sometimes overlie mature source rocks and are capped by shales, marls, and tight carbonates. Significant quantities of hydrocarbons are contained in these reservoirs in different parts of the Greater Arabian basin.

  2. Provenance of the Heavy Mineral-enriched Alluvial Deposits at the West Coast of Red Sea. Implications to the Evolution of Arabian-Nubian Crust

    NASA Astrophysics Data System (ADS)

    Mahar, M. A.; Ibrahim, T.; Goodell, P.

    2014-12-01

    Here we present the LA-ICP-MS U-Pb ages and Hf isotopic record of detrital zircons from the active alluvial fans at the west coast of the Red Sea. The Ras Manazal alluvial fan (primarily composed of zircon, magnetite with some rutile, ilmenite and monazite) yielded a relatively restricted age population ranges from 765 to 666 Ma. These ages and present-day drainage pattern is consistent that the sediments are primarily derived from erosion of nearby subduction related granitoids in the immediate west (i.e., not more than 50 km from the Red Sea coast) of the fan. In contrast, approximately 160 km south, at the Egypt-Sudan border, the Wadi Diit fan is relatively more enriched in ilmenite and REE-bearing phases (e.g., thorite, monazite, xenotime, garnet etc.) and yielded five zircon age populations of 1) 824-733 Ma, 2) 730-705 Ma, 3) 646-608 Ma, 4) 516-500 Ma, and 5) 134-114 Ma. The age populations 1-3 if coupled with the present-day drainage pattern can be related to the earlier subduction related and later post collision granitoids in the southern part of the South Eastern Desert and Gebeit terrane of northern Sudan. Sparse Early Cretaceous zircons (134-114 Ma) are derived from the Mesozoic volcanic suits in the source region. However, the age group 516-500 Ma is enigmatic. Wadi Diit zircons are primarily derived from granitoids in the broad S-N directed Hamisana Shear Zone and its subordinate SW to NE directed Onib-Sol-Hamed Suture Zone. These shear zones provided pathways for the present-day drainage system for sediment transportation to the Wadi Diit and adjacent coastal region. We infer that the ca. 500 Ma late-stage magmatic zircons represent a hitherto unknown magmatic event, possibly related to the shear heating associated with the crustal scale shear zones. This implies that the shear zones in the South Eastern Desert and northern Sudan remained thermally active as late as ~500 Ma. The time resolved hafnium composition (ɛHf (t)) of both fans varies from +3

  3. Provenance of the heavy mineral-enriched alluvial deposits at the west coast of the Red Sea. Implications for evolution of Arabian-Nubian crust

    NASA Astrophysics Data System (ADS)

    Mahar, Munazzam Ali; Ibrahim, Tarek M. M.; Goodell, Philip C.

    2014-12-01

    Here we present the LA-ICP-MS U-Pb ages and Hf isotopic record of detrital zircons from the active alluvial fans at the west coast of the Red Sea. The Ras Manazal alluvial fan (primarily composed of zircon, magnetite with some rutile, ilmenite and monazite) yielded a relatively restricted age population ranges from 765 to 666 Ma. These ages and present-day drainage pattern is consistent that the sediments are primarily derived from erosion of nearby subduction related granitoids in the immediate west (i.e., not more than 50 km from the Red Sea coast) of the fan. In contrast, approximately 160 km south, at the Egypt-Sudan border, the Wadi Diit fan is relatively more enriched in ilmenite and REE-bearing phases (e.g., thorite, monazite, xenotime, garnet, etc.) and yielded five zircon age populations of (1) 824-733 Ma, (2) 730-705 Ma, (3) 646-608 Ma, (4) 516-500 Ma, and (5) 134-114 Ma. The age populations 1-3 if coupled with the present-day drainage pattern can be related to the earlier subduction related and later post collision granitoids in the southern part of the South Eastern Desert and Gebeit terrane of northern Sudan. Sparse Early Cretaceous zircons (134-114 Ma) are derived from the Mesozoic volcanic suits in the source region. However, the age group 516-500 Ma is enigmatic. Wadi Diit zircons are primarily derived from granitoids in the broad S-N directed Hamisana Shear Zone and its subordinate SW to NE directed Onib-Sol-Hamed Suture Zone. These shear zones provided pathways for the present-day drainage system for sediment transportation to the Wadi Diit and adjacent coastal region. We infer that the ca. 500 Ma late-stage magmatic zircons represent a hitherto unknown magmatic event, possibly related to the shear heating associated with the crustal scale shear zones. This implies that the shear zones in the South Eastern Desert and northern Sudan remained thermally active as late as ∼500 Ma. The time resolved hafnium composition (εHf (t)) of both fans varies

  4. Crustal evolution of the northern Arabian platform in Syria

    SciTech Connect

    Best, J.A.; Muawia, B.; Chaimov, T.A. ); Al-Saad, D.; Sawaf, T.; Gebran, A. )

    1991-03-01

    Analysis of available geological and geophysical data within Syria has allowed for further understanding of the geologic history of the northern Arabian platform from Proterozoic to present. Elements of the history involve: Proterozoic convergence and suturing of at least two distinct microplates, minor Cambrian extension and associated magmatism, development of a failed intracratonic rift in the early Mesozoic, and inversion of that sedimentary trough that began in the Late Cretaceous. The diverse Phanerozoic tectonic features in Syria may be due to reactivation along older zones of weaknesses in the northern Arabian plate; the proposed Proterozoic suture zone lies along strike of the present day Palmyride intracratonic mountain belt. The construction of isopach maps of the Ordovician through Quaternary sections in Syria based on regional well control and seismic reflection data demonstrates regional structural-stratigraphic relationships. Basement deformation maps, derived from superposition of the formation isopachs, indicate the transformation of an east-directed Paleozoic margin into a well-directed Mesozoic margin (Levantine margin). Contemporaneous with this margin transformation was the development of an east-northeast-trending rift (Palmyride trough) toward the craton interior. Finally, Cenozoic eastward tilting of the Arabian plate, associated with loading of the plate along the Mesopotamian foredeep and uplift of the plate along the Red Sea margin is observed across the southern Arabian platform. Eastward tilting is also observed across the southern Arabian platform. Eastward tilting is also observed on the northern platform with respect to the top of the crystalline basement, indicating a similarity in response of the entire Arabian plate to loading and uplift along its margins.

  5. Tectonic and deposition model of late Precambrian-Cambrian Arabian and adjoining plates

    SciTech Connect

    Husseini, M.I. )

    1989-09-01

    During the late Precambrian, the terranes of the Arabian and adjoining plates were fused along the northeastern flank of the African plate in Gondwanaland. This phase, which ended approximately 640 to 620 Ma, was followed by continental failure (620 to 580 Ma) and intracontinental extension (600 to approximately 550 Ma). During the Infracambrian extensional phase, a triple junction may have evolved near the Sinai Peninsula and may have consisted of the (1) Jordan Valley and Dead Sea rift branch, (2) Sinai and North Egypt rift branch, and (3) the Najd wrench-rift branch. The Najd, Hawasina, and Zagros fault systems may have been transverse faults that accompanied rifting in the Arabian Gulf and Zagros Mountains, southern Oman, Pakistan, and Kerman in central Iran. While the area was extending and subsiding, the Tethys Ocean flooded the eastern side of the Arabian plate and Iran and deposited calcareous clastics, carbonates, and evaporites (including the Hormuz and Ara halites). This transgression extended into the western part of the Arabian plate via the Najd rift system. The termination of the extensional phase during the late Early Cambrian was accompanied by a major regression and terrestrial conditions on the Arabian Peninsula. However, by the Early Ordovician, as sea level peaked to a highstand, the Arabian plate was blanketed with marginal marine sediments. 11 figs., 2 tabs.

  6. Structure of the Lithosphere and Upper Mantle Across the Arabian Peninsula

    SciTech Connect

    Al-Amri, A; Rodgers, A

    2007-01-05

    Analysis of modern broadband (BB) waveform data allows for the inference of seismic velocity structure of the crust and upper mantle using a variety of techniques. This presentation will report inferences of seismic structure of the Arabian Plate using BB data from various networks. Most data were recorded by the Saudi Arabian National Digital Seismic Network (SANDSN) which consists of 38 (26 BB, 11 SP) stations, mostly located on the Arabian Shield. Additional data were taken from the 1995-7 Saudi Arabian IRIS-PASSCAL Deployment (9 BB stations) and other stations across the Peninsula. Crustal structure, inferred from teleseismic P-wave receiver functions, reveals thicker crust in the Arabian Platform (40-45 km) and the interior of the Arabian Shield (35-40 km) and thinner crust along the Red Sea coast. Lithospheric thickness inferred from teleseismic S-wave receiver functions reveals very thin lithosphere (40-80 km) along the Red Sea coast which thickens rapidly toward the interior of the Arabian Shield (100-120 km). We also observe a step of 20-40 km in lithospheric thickness across the Shield-Platform boundary. Seismic velocity structure of the upper mantle inferred from teleseismic P- and S-wave travel time tomography reveals large differences between the Shield and Platform, with the Shield being underlain by slower velocities, {+-}3% for P-waves and {+-}6% for S-waves. Seismic anisotropy was inferred from shear-wave splitting, using teleseismic SKS waveforms. Results reveal a splitting time of approximately 1.4 seconds, with the fast axis slightly east of north. The shear-wave splitting results are consistent across the Peninsula, with a slight clockwise rotation parallel for stations near the Gulf of Aqaba. In summary, these results allow us to make several conclusions about the tectonic evolution and current state of the Arabian Plate. Lithospheric thickness implies that thinning near the Red Sea has accompanied the rupturing of the Arabian

  7. Active NE-SW Compressional Strain Within the Arabian Plate

    NASA Astrophysics Data System (ADS)

    Floyd, M. A.; ArRajehi, A.; King, R. W.; McClusky, S.; Reilinger, R. E.; Douad, M.; Sholan, J.; Bou-Rabee, F.

    2012-12-01

    Motion of the Arabian plate with respect to Eurasia has been remarkably steady over more than 25 Myr as revealed by comparison of geodetic and plate tectonic reconstructions (e.g., McQuarrie et al., 2003, GRL; ArRajehi et al., 2010, Tectonics). While internal plate deformation is small in comparison to the rate of Arabia-Eurasia convergence, the improved resolution of GPS observations indicate ~ NE-SW compressional strain that appears to affect much of the plate south of latitude ~ 30°N. Seven ~ NE-SW oriented inter-station baselines all indicated shortening at rates in the range of 0.5-2 mm/yr, for the most part with 1-sigma velocity uncertainties < 0.4 mm/yr. Plate-scale strain rates exceed 2×10-9/yr. The spatial distribution of strain can not be resolved from the sparse available data, but strain appears to extend at least to Riyadh, KSA, ~ 600 km west of the Zagros Fold and Thrust Belt that forms the eastern, collisional boundary of the Arabian plate with Eurasia (Iran). Geodetic velocities in the plate tectonic reference frame for Arabia, derived from magnetic anomalies in the Red Sea (Chu and Gordon, 1998, GJI), show no significant E-W motion for GPS stations located along the Red Sea coast (i.e., geodetic and plate tectonic spreading rates across the Red Sea agree within their resolution), in contrast to sites in the plate interior and along the east side of the plate that indicate east-directed motions. In addition, NE-SW contraction is roughly normal to ~ N-S striking major structural folds in the sedimentary rocks within the Arabian Platform. These relationships suggest that geodetically observed contraction has characterized the plate for at least the past ~ 3 Myr. Broad-scale contraction of the Arabian plate seems intuitively reasonable given that the east and north sides of the plate are dominated by active continental collision (Zagros, E Turkey/Caucasus) while the west and south sides are bordered by mid-ocean ridge spreading (Red Sea and Gulf of

  8. Petroleum geology of Arabian Peninsula

    SciTech Connect

    Billo, S.M.

    1982-05-01

    Petroleum activities in the Arabian Peninsula show new trends in the 1980s. Petroleum exploration is intensified and huge discoveries are anticipated. A giant Jurassic gas field along the coast of the Arabian Gulf discovered recently tops 150 tcf, the largest single reserve ever. Other giant oil fields in the area are undergoing expansion in development and productivity. Today, the Peninsula, with a total area that surpasses one million square miles, produces and exports more oil and gas and has greater reserves than any other area in the world. The excellent reservoir rocks are located in the Jurassic and Cretaceous formations between the Arabian Shield and the Tethyan Seaway. They represent porous and permeable marine cyclical beds sealed by impervious shales and anhydrites. Reservoir sedimentology was affected by 2 orogenies during late Cretaceous and Pliocene time portrayed by the Cratonic area to the southwest and the orthogeosynclinal area to the northeast. The eastern part was little deformed by these movements.

  9. Increasing Arabian dust activity and the Indian Summer Monsoon

    NASA Astrophysics Data System (ADS)

    Solmon, F.; Nair, V. S.; Mallet, M.

    2015-02-01

    Over the past decade, Aerosol Optical Depth (AOD) observations based on satellite and ground measurements have shown a significant increase over Arabia and the Arabian Sea, attributed to an intensification of regional dust activity. Recent studies have also suggested that west Asian dust forcing could induce a positive response of Indian monsoon precipitations on a weekly time scale. Using observations and a regional climate model including interactive slab ocean and dust aerosol schemes, the present study investigates possible climatic links between the increasing June-July-August-September (JJAS) Arabian dust activity and precipitation trends over southern India during the 2000-2009 decade. Meteorological reanalysis and AOD observations suggest that the observed decadal increase of dust activity and a simultaneous intensification of summer precipitation trend over southern India are both linked to a deepening of JJAS surface pressure conditions over the Arabian Sea. We show that the model skills in reproducing this trends and patterns are significantly improved only when an increasing dust emission trend is imposed on the basis of observations. We conclude that although climate variability might primarily determine the observed regional pattern of increasing dust activity and precipitation during the 2000-2009 decade, the associated dust radiative forcing might however induce a critical dynamical feedback contributing to enhanced regional moisture convergence and JJAS precipitation over Southern India.

  10. Biodeterioration of concrete piling in the Arabian Gulf

    SciTech Connect

    Jadkowski, T.K.; Wiltsie, E.A.

    1985-03-01

    Concrete is one of the most widely used materials in marine construction because of its characteristic durability in sea environments. Recent inspection of concrete piles installed in the Arabian Gulf has revealed that concrete with high content of calcareous aggregate is susceptible to biodeterioration. Marine rock borers and sponges, which are common in areas where the seabed is composed of limestone rock, have been identified as the marine species responsible for the biodeterioration. Boring organisms pose a significant threat to concrete pile structural integrity. Boreholes deteriorate concrete and expose outer pile reinforcement to seawater. This paper describes the causes and magnitude of biodeterioration of piles installed in the Arabian Gulf and presents design parameters and material specifications for the selected preventive repair system.

  11. Increasing Arabian dust activity and the Indian summer monsoon

    NASA Astrophysics Data System (ADS)

    Solmon, F.; Nair, V. S.; Mallet, M.

    2015-07-01

    Over the past decade, aerosol optical depth (AOD) observations based on satellite and ground measurements have shown a significant increase over Arabia and the Arabian Sea, attributed to an intensification of regional dust activity. Recent studies have also suggested that west Asian dust forcing could induce a positive response of Indian monsoon precipitations on a weekly timescale. Using observations and a regional climate model including interactive slab-ocean and dust aerosol schemes, the present study investigates possible climatic links between the increasing June-July-August-September (JJAS) Arabian dust activity and precipitation trends over southern India during the 2000-2009 decade. Meteorological reanalysis and AOD observations suggest that the observed decadal increase of dust activity and a simultaneous intensification of summer precipitation trend over southern India are both linked to a deepening of JJAS surface pressure conditions over the Arabian Sea. In the first part of the study, we analyze the mean climate response to dust radiative forcing over the domain, discussing notably the relative role of Arabian vs. Indo-Pakistani dust regions. In the second part of the study, we show that the model skills in reproducing regional dynamical patterns and southern Indian precipitation trends are significantly improved only when an increasing dust emission trend is imposed on the basis of observations. We conclude that although interannual climate variability might primarily determine the observed regional pattern of increasing dust activity and precipitation during the 2000-2009 decade, the associated dust radiative forcing might in return induce a critical dynamical feedback contributing to enhancing regional moisture convergence and JJAS precipitations over southern India.

  12. Interannual variability and predictability over the Arabian Penuinsula Winter monsoon region

    NASA Astrophysics Data System (ADS)

    Adnan Abid, Muhammad; Kucharski, Fred; Almazroui, Mansour; Kang, In-Sik

    2016-04-01

    Interannual winter rainfall variability and its predictability are analysed over the Arabian Peninsula region by using observed and hindcast datasets from the state-of-the-art European Centre for Medium-Range Weather Forecasts (ECMWF) seasonal prediction System 4 for the period 1981-2010. An Arabian winter monsoon index (AWMI) is defined to highlight the Arabian Peninsula as the most representative region for the Northern Hemispheric winter dominating the summer rainfall. The observations show that the rainfall variability is relatively large over the northeast of the Arabian Peninsula. The correlation coefficient between the Nino3.4 index and rainfall in this region is 0.33, suggesting potentially some modest predictability, and indicating that El Nino increases and La Nina decreases the rainfall. Regression analysis shows that upper-level cyclonic circulation anomalies that are forced by El Nino Southern Oscillation (ENSO) are responsible for the winter rainfall anomalies over the Arabian region. The stronger (weaker) mean transient-eddy activity related to the upper-level trough induced by the warm (cold) sea-surface temperatures during El Nino (La Nina) tends to increase (decrease) the rainfall in the region. The model hindcast dataset reproduces the ENSO-rainfall connection. The seasonal mean predictability of the northeast Arabian rainfall index is 0.35. It is shown that the noise variance is larger than the signal over the Arabian Peninsula region, which tends to limit the prediction skill. The potential predictability is generally increased in ENSO years and is, in particular, larger during La Nina compared to El Nino years in the region. Furthermore, central Pacific ENSO events and ENSO events with weak signals in the Indian Ocean tend to increase predictability over the Arabian region.

  13. Severe dust storms over the Arabian Peninsula: Observations and modeling

    NASA Astrophysics Data System (ADS)

    shalaby, ahmed

    2014-05-01

    Dust aerosols and dust storms have tremendous effects on human health and all development activities. Also atmospheric dust plays a major role in the Earth climate system by its interaction with radiation and clouds. Severe dust storms are considered the severest phenomena in the Arabian Peninsula, since they are occurring all the year round with maximum activity and frequency in Summer. The Regional Climate Model (RegCM4) has been used to simulate severe dust storms events in the Arabian Peninsula from 1998 up to 2011. This long period simulation shows a typical pattern and dynamical features of the large-scale severe dust storm in winter seasons and summer seasons. The Aerosol Optical Depth (AOD) from the model outputs have been compared against ground--base observations of three AERONET stations (i.e., Kuwait, Mazeria and Solar-Village) and daily space--based observations of MISR, Deepblue and OMI. The dynamical analysis of the large—scale severe dust storms reveal the difference between winter time storms and summer time storm. Winter time storm occurs when the cold air front in the north is coupled with the extension of the Red Sea trough from the south. However, the summer time storm is associated with strong Shamal wind that extend from northern Kuwait to the southern Arabian Peninsula.

  14. SeaWiFS: Pakistan Dust

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This SeaWiFS image collected on November 3, 2001 depicts a dust storm blowing southward over the northern end of the Arabian Sea from Pakistan and Iran. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  15. New heat flow measurements in Oman in the Arabian plate

    NASA Astrophysics Data System (ADS)

    Rolandone, F.; Lucazeau, F.; Jaupart, C.; Leroy, S.; Bache, F.; Amerjeed, M.; Lally, J.

    2009-04-01

    Precambrian shields are viewed as low heat flow provinces but detailed studies in Canada, South Africa and India shields demonstrate that large heat flow differences exist between them and within a single province, related to differences of crustal structures. Very few heat flow measurements are available on the Arabian shield and its thermal structure is poorly constrained. Heat flow reported for the Arabian Shield and its immediate platform (36-88 mWm-2) is broad. Thermal regime has a control on rheology and on deformation and the Arabian shield is of particular interest because it was affected by geodynamic processes such as the Red Sea and Gulf of Aden riftings starting around 30 Ma ago and the formation of the Dead Sea Transform fault starting at about 20 Ma. In December 2006, a marine heat-flow survey in the Gulf of Aden provided 169 new heat-flow measurements along multi-channel seismic profiles. One of the main results is that the high heat-flow (~120 mWm-2), characteristic of oceanic domains, extends into the deep continental margin and switches abruptly in the proximal margin to a low value (~40 mWm-2) typical of stable Precambrian domain. These low values have been confirmed by estimates derived from oil exploration data in few locations south of Oman. These data indicate a strong contrast of thermal regimes within the continental margin. Recent tomography studies on Arabia in Oman show that the lithosphere is significantly affected within Arabia in the vicinity of the Red Sea and the Gulf of Aden. This pattern is apparently different from the observed heat-flow pattern, which needs to be confirmed and extended into the Arabian platform. The survey we conducted in October 2008 was to evaluate the thermal regime in the onshore domains of Oman. We measured the temperature gradient in 9 water wells in Dhofar south of Oman and in 8 mining wells in northern Oman in the ophiolite belt. The goal is to investigate the thermal structure of the Arabian plate and

  16. Hypoxia in the central Arabian Gulf Exclusive Economic Zone (EEZ) of Qatar during summer season

    NASA Astrophysics Data System (ADS)

    Al-Ansari, Ebrahim M. A. S.; Rowe, G.; Abdel-Moati, M. A. R.; Yigiterhan, O.; Al-Maslamani, I.; Al-Yafei, M. A.; Al-Shaikh, I.; Upstill-Goddard, R.

    2015-06-01

    One of the most fascinating and unexpected discoveries during the Qatar University Marine Expeditions to the marine Exclusive Economic Zone (EEZ) of Qatar in 2000-2001, was the detection of a hypoxic water layer in the central region of the Arabian Gulf in waters deeper than 50 m. Hypoxia was defined as the region where the concentration of dissolved oxygen was less than 2 mg L-1. This article presents the discovery of hypoxia in the Arabian Gulf, based on samples collected (mainly during evening or night time) from vertical profiles along transects of the EEZ of Qatar and analyzed for physico-chemical properties, nutrients and chlorophyll-a. Hypoxia occurred in the summer months caused by an interaction between physical stratification of the water column that prevents oxygen replenishment, and biological respiration that consumes oxygen. Strong south-westerly winds (the SW monsoon) from June to September drive the relatively low-salinity nutrient-rich surface water from the Arabian Sea/Arabian Gulf (Sea of Oman) through the Strait of Hormuz into the central-Arabian Gulf, and this surface current penetration fertilizes the deep central-Arabian Gulf during the summer period. A strong seasonal pycnocline is formed between deeper waters at an ambient temperature of 20.9 °C and surface waters at 31.9 °C. This prevents the mixing of supersaturated O2 (>100-130%) water from the upper layer that would otherwise raise concentrations of dissolved oxygen below the thermocline, thus resulting in deep water hypoxia, i.e. dissolved oxygen levels of less than 0.86 ml L-1 at 17.3% saturation. These are the lowest values ever recorded for the Arabian Gulf. The calculated area of hypoxia is around 7220 square kilometers, and occurs in a layer about ≥15 m thick above the sea floor which extends toward the deep part of the Qatar Exclusive Economic Zone (EEZ). The biological consequences of this hypoxia on the sea floor are yet to be investigated.

  17. Evidence for anomalous mantle upwelling beneath the Arabian Platform from travel time tomography inversion

    NASA Astrophysics Data System (ADS)

    Koulakov, Ivan; Burov, Evgeniy; Cloetingh, Sierd; El Khrepy, Sami; Al-Arifi, Nassir; Bushenkova, Natalia

    2016-01-01

    We present a new model of P-velocity anomalies in the upper mantle beneath the Arabian Peninsula, Red Sea, and surrounding regions. This model was computed with the use of travel time data from the global catalogue of the International Seismological Center (ISC) for the years of 1980-2011. The reliability of the model was tested with several synthetic tests. In the resulting seismic model, the Red Sea is clearly associated with a higher P-velocity anomaly in the upper mantle at least down to 300 km depth. This anomaly might be caused by upward deviation of the main mantle interfaces caused by extension and thinning of the lithosphere due to passive rifting. Thick lithosphere of the Arabian Platform is imaged as a high-velocity anomaly down to 200-250 km depth. Below this plate, we observe a low-velocity structure that is interpreted as a hot mantle upwelling. Based on the tomography results, we propose that this upper mantle anomaly may represent hot material that migrates westward and play a major role in the formation of Cenozoic basaltic lava fields in western Arabia. On the northeastern side of the Arabian Plate, we clearly observe a dipping high-velocity zone beneath Zagros and Makran, which is interpreted as a trace of subduction or delamination of the Arabian Plate lithosphere.

  18. A Numerical Study of Circulation and Water Exchange in the Arabian Gulf

    NASA Astrophysics Data System (ADS)

    Azhar, Muchamad Al; Temimi, Marouane; Zhao, Jun; Ghedira, Hosni

    2015-04-01

    Ocean circulation and water mass variability in semi-enclosed and marginal sea of the Arabian Gulf are numerically simulated using a three-dimensional model of Regional Ocean Modeling System (ROMS). The model is forced by relatively high-frequency of atmospheric forcing and tides. The numerical simulations are compared with a set data of moored and spatially distributed measurements of temperature, salinity, current velocity, and sea-surface height. The model results generally agree well with temporal variation of the observed current velocity during spring and neap tide, as well as seasonal variation of temperature and salinity in surface and sub-surface depths. Seasonal variability of water mass and circulation in the Arabian Gulf affected by the propagation of Indian Ocean Surface Water to the Arabian Gulf, air-sea heat fluxes, and mesoscale eddy activities are discussed. Sensitivity study using different source of atmospheric data for forcing of the model, as well as climatology data and global ocean model for specifying values in open boundaries of the model are conducted towards implementation of the model operationally. Further development of the model by coupling it with atmospheric model most likely will increase the skill of the model and provide better understanding on how the complex air-sea interaction affecting circulation and water mass exchange in this region.

  19. The thermal state of the Arabian plate derived from heat flow measurements in Oman and Yemen

    NASA Astrophysics Data System (ADS)

    Rolandone, Frederique; Lucazeau, Francis; Leroy, Sylvie; Mareschal, Jean-Claude; Jorand, Rachel; Goutorbe, Bruno; Bouquerel, Hélène

    2013-04-01

    The dynamics of the Afar plume and the rifting of the Red Sea and the Gulf of Aden affect the present-day thermal regime of the Arabian plate. However, the Arabian plate is a Precambrian shield covered on its eastern part by a Phanerozoic platform and its thermal regime, before the plume and rifting activities, should be similar to that of other Precambrian shields with a thick and stable lithosphere. The first heat flow measurements in the shield, in Saudi Arabia, yielded low values (35-44 mW/m2), similar to the typical shields values. Recent heat flow measurements in Jordan indicate higher values (56-66 mW/m2). As part of the YOCMAL project (YOung Conjugate MArgins Laboratory), we have conducted heat flow measurements in southern and northern Oman to obtain 10 new heat flux values in the eastern Arabian plate. We also derived 20 heat flux values in Yemen and Oman by processing thermal data from oil exploration wells. The surface heat flux in these different locations is uniformly low (45 mW/m2). The heat production in samples from the Dhofar and Socotra Precambrian basement is also low (0.7 µW/m3). Differences in heat flow between the eastern (60 mW/m2) and the western (45 mW/m2) parts of Arabia reflect differences in crustal heat production as well as a higher mantle heat flux in the west. We have calculated a steady state geotherm for the Arabian platform that intersects the isentropic temperature profile at a depth of about 150 km, consistent with the seismic observations. Seismic tomography studies of the mantle beneath Arabia also show this east-west contrast. Seismic studies have shown that the lithosphere is rather thin, 100 km or less below the shield and 150 km below the platform. The lithospheric thickness for the Arabian plate is 150 km, and the progressive thinning near the Red Sea, caused by the thermal erosion of the plume material, is too recent to be detected at the surface. The Afar plume mostly affects the base of the Arabian lithosphere along

  20. Distribution of oceanic and continental leads in the Arabian-Nubian Shield

    USGS Publications Warehouse

    Stacey, J.S.; Stoeser, D.B.

    1983-01-01

    New common lead data for feldspar, whole-rock, and galena samples from the Arabian-Nubian Shield, together with data from previous work, can be divided into two main groups. Group I leads have oceanic (mantle) characteristics, whereas group II leads have incorporated a continental-crustal component of at least early Proterozoic age. The group I leads are found in rocks from the Red Sea Hills of Egypt and the western and southern parts of the Arabian Shield. Group II leads are found in rocks from the northeastern and eastern parts of the Arabian Shield, as well as from the southeastern Shield near Najran. They are also found in rocks to the south in Yemen, to the east in Oman, and to the west at Aswan, Egypt. This distribution of data suggests that the Arabian-Nubian Shield has an oceanic core flanked by rocks that have developed, at least in part, from older continental material. Two mechanisms are suggested by which this older lead component could have been incorporated into the late Proterozoic rocks, and each may have operated in different parts of the Shield. The older lead component either was derived directly from an underlying early Proterozoic basement or was incorporated from subducted pelagic sediments or sediments derived from an adjacent continent. New U-Pb zircon data indicate the presence of an early Proterozoic basement southeast of Jabal Dahul in the eastern Arabian Shield. These data, together with 2,000-Ma-old zircons from the Al Amar fault zone, verify the implication of the common lead data that at least a part of the eastern Arabian Shield has an older continental basement. Because continental margins are particularly favorable locations for development of ore deposits, these findings may have important economic implications, particularly for tin, tungsten, and molybdenum exploration. ?? 1983 Springer-Verlag.

  1. Arabian peninsula: zone of ferment

    SciTech Connect

    Stookey, R.W.

    1984-01-01

    The Arabian Peninsula is an area which must be approached in terms of its own values and traditions. The different states, however, present difficulties for even the most well-informed policymaker because the region is not homogeneous. Some of the states are tenuous congeries of tribal and sectarian communities that do not necessarily share the aims of the ruling group. The authors of these six essays consider (1) the economic position of the states, (2) how oil exports affect the economies of the exporting states, (3) how traditional tribal and religious societies react to change, (4) whether their social values are conducive to modernization, and (5) what factors lead to the development of dissent, and how they affect the expression of dissent. Separate abstracts were prepared for two of the essays selected for the Energy Data Base (EDB) and Energy Abstracts for Policy Analysis (EAPA). 23 tables.

  2. Cenozoic epeirogeny of the Arabian Peninsula from drainage modeling

    NASA Astrophysics Data System (ADS)

    Wilson, J. W. P.; Roberts, G. G.; Hoggard, M. J.; White, N. J.

    2014-10-01

    is generally accepted that the Arabian Peninsula has been uplifted by subcrustal processes. Positive residual depth anomalies from oceanic crust in the Red Sea and in the Gulf of Aden suggest that a region surrounding this peninsula is dynamically supported. Admittance calculations, surface wave tomography studies, and receiver function analyses all imply that regional topography is generated and maintained by some combination of mantle convective circulation and lithospheric thickness changes. Despite these significant advances, the spatial and temporal uplift rate history of the Arabian Peninsula is not well known. Here we show that a regional uplift rate history can be obtained by jointly inverting 225 longitudinal river profiles that drain this peninsula. Our strategy assumes that shapes of individual river profiles are controlled by uplift rate history and moderated by erosional processes. We used local measurements of incision rate to calibrate the relevant erosional parameters. In our inverse algorithm, uplift rate is permitted to vary smoothly as a function of space and time but upstream drainage area remains invariant. We also assume that knickzone migration is not lithologically controlled. Implications of these important assumptions have been investigated. Our results suggest that the Arabian Peninsula underwent two phases of asymmetric uplift during the last 20-30 Ma at rates of 0.05-0.1 mm a-1. The southwestern flank of the peninsula has been uplifted by 1.5-2.5 km. Regional stratigraphic constraints, the age and composition of volcanism, paleosol formation, incised peneplains, emergent marine terraces, and thermochronometric measurements corroborate our calculated patterns of uplift. Progressive development of three domal swells along the western margin of the peninsula is consistent with localized upwelling of hot asthenospheric mantle.

  3. Arabian Peninsula and northeast Africa as seen from Gemini 11 spacecraft

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Arabian Peninsula (on left) and northeast Africa (on right) as seen from the Gemini 11 spacecraft at an altitude of 340 nautical miles during its 27th revolution of the earth, looking southeast. Saudia Arabia, South Arabia, Yemen and Aden Protectorate are at left. At bottom right is Ethiopia. French Somaliland is in center on right shore. Somali is at upper right. Body of water at bottom is Red Sea. Gulf of Aden is in center; and at top left is Indian Ocean.

  4. Fate of oil hydrocarbons in fish and shrimp after major oil spills in the Arabian Gulf

    SciTech Connect

    Fayad, N.M.; El-Mubarak, A.H.; Edora, R.L.

    1996-03-01

    Pollution of the marine environment with crude oil represents one of the most serious environmental problems that confront Saudi Arabia and other Gulf states. Oil pollution in the Arabian Gulf environment may affect the inhabitants through (1) human health hazard resulting from the consumption of contaminated sea food, (2) loss of food due to alteration of species productivity or elimination of some species, and (3) deterioration of recreation areas. Moreover, the problem of oil spill may be more severe in this part of the world. This is mainly because the source of drinking water in various Gulf states depends largely on sea water from which desalinated water is produced. Contamination of sea water with crude oil may adversely affect the quality of desalinated water and may badly damage desalination plants. During the last twelve years, the Arabian Gulf has been affected by two major oil spills. The first spill occurred on February 4, 1983 during the Iraq-Iran War, and the second major oil spill occured during the 1991 Gulf War. There is limited information about the level of oil hydrocarbons in edible fish, but two studies were carried out after both spills. This paper summarized the results of both studies carried out to assess the extent of contamination of various fish species of commercial value from the Arabian Gulf with oil hydrocarbons.

  5. Tectonic and depositional model of the Arabian and adjoining plates during the Silurian-Devonian

    SciTech Connect

    Husseini, M.I. )

    1991-01-01

    During the Late Ordovician and Early Silurian, the western part of the Arabian Peninsula was covered by polar glaciers that advanced from the south pole in African Gondwana. During this period, nondeposition, erosion, or marginal marine conditions prevailed in eastern and northern Arabia. When the glaciers melted in the Early Silurian, sea level rose sharply and the paleo-Tethys Ocean transgressed the Arabian and adjoining plates depositing a thick, organic-rich shale directly over the glaciogenic and periglacial rocks and related unconformities. The post-glacial sequence coarsens upward reflecting the passage of a coastline prograding northward from African and Arabian Gondwana to northern Arabia. A sea level drop in the Late Silurian placed the study area in a terrestrial environment; however, as sea level recovered in the Early Devonian, a carbonate sequence blanketed most of the area. The transgression, however, was interrupted by regional uplift and local orogenic movements in the Middle and Late Devonian. These movements constitute the onset of Hercynian tectonism, which resulted in erosion of the older sequences, depositional hiatuses, and regional facies changes.

  6. Saudi Arabian seismic deep-refraction profiles; final project report

    USGS Publications Warehouse

    Healy, J.H.; Mooney, W.D.; Blank, H.R.; Gettings, M.E.; Kohler, W.M.; Lamson, R.J.; Leone, L.E.

    1983-01-01

    In February 1978 a seismic deep-refraction profile was recorded by the U.S. Geological Survey along a 1000-km line across the Arabian Shield in western Saudi Arabia. The line begins in Mesozoic cover rocks near Riyadh on the Arabian Platform, leads southwesterly across three major Precambrian tectonic provinces, traverses Cenozoic rocks of the coastal plain near Jizan (Tihamat-Asir), and terminates at the outer edge of the Farasan Bank in the southern Red Sea. More than 500 surveyed recording sites were occupied, including 19 in the Farasan Islands. Six shot points were used: five on land, with most charges placed below the water table in drill holes, and one at sea, with charges placed on the sea floor and detonated from a ship. Slightly more than 61 metric tons of explosives were used in 19 discrete firings. Seismic energy was recorded by 100 newly-developed portable seismic stations deployed in approximately 200 km-long arrays for each firing. Each station consisted of a standard 2-Hz vertical component geophone coupled to a self-contained analog recording instrument equipped with a magnetic-tape cassette. In this final report, we fully document the field and data-processing procedures and present the final seismogram data set as both a digital magnetic tape and as record sections for each shot point. Record sections include a normalized set of seismograms, reduced at 6 km/s, and a true-amplitude set, reduced at 8 km/s, which have been adjusted for amplifier gain, individual shot size, and distance from the shot point. Appendices give recorder station and shot information, digital data set descriptions, computer program listings, arrival times used in the interpretation, and a bibliography of reports published as a result of this project. We used two-dimensional ray-tracing techniques in the data analysis, and our interpretation is based primarily on horizontally layered models. The Arabian Shield is composed, to first-order, of two layers, each about 20 km

  7. The influence of extreme winds on coastal oceanography and its implications for coral population connectivity in the southern Arabian Gulf.

    PubMed

    Cavalcante, Geórgenes H; Feary, David A; Burt, John A

    2016-04-30

    Using long-term oceanographic surveys and a 3-D hydrodynamic model we show that localized peak winds (known as shamals) cause fluctuation in water current speed and direction, and substantial oscillations in sea-bottom salinity and temperature in the southern Persian/Arabian Gulf. Results also demonstrate that short-term shamal winds have substantial impacts on oceanographic processes along the southern Persian/Arabian Gulf coastline, resulting in formation of large-scale (52 km diameter) eddies extending from the coast of the United Arab Emirates (UAE) to areas near the off-shore islands of Iran. Such eddies likely play an important role in transporting larvae from well-developed reefs of the off-shore islands to the degraded reef systems of the southern Persian/Arabian Gulf, potentially maintaining genetic and ecological connectivity of these geographically distant populations and enabling enhanced recovery of degraded coral communities in the UAE. PMID:26506023

  8. Mitochondrial DNA structure in the Arabian Peninsula

    PubMed Central

    2008-01-01

    Background Two potential migratory routes followed by modern humans to colonize Eurasia from Africa have been proposed. These are the two natural passageways that connect both continents: the northern route through the Sinai Peninsula and the southern route across the Bab al Mandab strait. Recent archaeological and genetic evidence have favored a unique southern coastal route. Under this scenario, the study of the population genetic structure of the Arabian Peninsula, the first step out of Africa, to search for primary genetic links between Africa and Eurasia, is crucial. The haploid and maternally inherited mitochondrial DNA (mtDNA) molecule has been the most used genetic marker to identify and to relate lineages with clear geographic origins, as the African Ls and the Eurasian M and N that have a common root with the Africans L3. Results To assess the role of the Arabian Peninsula in the southern route, we genetically analyzed 553 Saudi Arabs using partial (546) and complete mtDNA (7) sequencing, and compared the lineages obtained with those present in Africa, the Near East, central, east and southeast Asia and Australasia. The results showed that the Arabian Peninsula has received substantial gene flow from Africa (20%), detected by the presence of L, M1 and U6 lineages; that an 18% of the Arabian Peninsula lineages have a clear eastern provenance, mainly represented by U lineages; but also by Indian M lineages and rare M links with Central Asia, Indonesia and even Australia. However, the bulk (62%) of the Arabian lineages has a Northern source. Conclusion Although there is evidence of Neolithic and more recent expansions in the Arabian Peninsula, mainly detected by (preHV)1 and J1b lineages, the lack of primitive autochthonous M and N sequences, suggests that this area has been more a receptor of human migrations, including historic ones, from Africa, India, Indonesia and even Australia, than a demographic expansion center along the proposed southern coastal

  9. Comparison of Arabian plate motion using satellite laser ranging and GPS observations

    NASA Astrophysics Data System (ADS)

    Alothman, A. O.; Fernandes, R. M.; Schillak, S. R.

    2013-12-01

    Two different space based observations have been used to estimate the velocity of the Arabian plate motion. The first set of observations is using the Saudi Arabia Laser Ranging Observatory (SALRO - 7832), which is situated in the middle of Arabian tectonic plate. Satellite Laser Ranging (SLR) observations of about 20 global SLR stations to LAGEOS-1 and LAGEOS-2 satellites collected for 14 years (1996-2009) have been used to determine Riyadh SLR station positions. The NASA Godard's GEODYN-II orbital software has been used to perform orbit determination of these two satellites. The velocities of SALRO were computed in reference to the ITRF2008 terrestrial reference frame. The second set of observations consists of Global Positioning System (GPS) observations of 15 GPS stations acquired in campaign and continuous mode for the period 2003 to 2009 (having at least 3 years' data span). Multi-year processing of stations having at least 3 years' time span and excluding stations within the deformation zone of Red Sea Ridge, such that they are distributed evenly within the rigid (interior) part of the Arabian plate. The Bernese 5.0/ADNEQ2 and GIPSY/OASIS 6.1 software packages were used to compute the daily solutions of coordinate time series applying the Precise Point Positioning (PPP) strategy. The velocities were estimated with respect to ITRF2008 and four estimates of the angular velocities for the Arabian plate have been computed using different datasets: independent Bernese and GIPSY solutions, combination of the GPS solutions only, and including the SLR solution. We present direct comparison between all different solutions showing that the Arabian tectonic plate motion determined from Riyadh SLR data and GPS data are in a good agreement with recent estimates, in particular with the global geodetic model GEODVEL and the geophysical MORVEL model.

  10. Conservation in the Arabian Gulf countries

    SciTech Connect

    Akkad, A.A.

    1990-05-01

    In the Arabian Gulf region in general, and in Saudi Arabia in particular, demand for water in the agricultural, domestic, and industrial sectors has increased dramatically as a result of rapid development, and improved standard of living, and diversification of economic activity in agriculture and industry. This article presents an overview of supply and demand situations prevailing in the Arabian Gulf region and discusses various conventional and unconventional alternatives for meeting the growing demand for water. It also describes conservation measures and their socioeconomic effects.

  11. Sequential stratigraphy of Jurassic and Cretaceous in the central Saudi Arabian platform

    SciTech Connect

    Le Nindre, Y.M.; Manivit, J.; Vaslet, D. ); Manivit, H. Univ. Pierre et Marie Curie, Paris )

    1991-08-01

    Depositional sequences and system tracts in the Jurassic and Cretaceous sedimentary rocks of the Central Saudi Arabian platform have been established on the basis of precise lithofacies analysis, detailed sedimentologic interpretation, and accurate age determination by ammonites, nautoli, brachipods, echinoids, and nannoflora. A eustatic depositional model integrated with accepted worldwide sequential stratigraphic data is proposed, and appears to correlate fairly well with the 1988 global sea level chart by Haq and others, particularly for the Lower and Middle Jurassic and the Middle and Upper Cretaceous. Ages determined by accurate biostratigraphic data enable time correlations to be made with third-order eustatic cycles from Vail's 1988 global chart. Eustatic changes therefore appear to be the main factors of sedimentary control during the Jurassic and Cretaceous on the Arabian platform.

  12. Tectonic synthesis of the northern Arabian platform

    SciTech Connect

    Everett, J.R.; Russell, O.R.; Stasxkowski, R.J.; Loyd, S.P.; Tabbutt, V.M. ); Dolan, P.; Stein, A. ); Scott, J. )

    1990-05-01

    The creation and destruction of Tethys oceans from the early Mesozoic to the present has created a complex suture zone along the Zagros/Bitlus trend. The fundamental interactions are between the Arabian and Euasian plates, but several microplates trapped between the major plates further complicate the tectonic fabric of the region. On the west, the Arabian plate slides past the African plate and the Sinai microplate along the Levant fault. The Palmyrides are related to a bend in this plate boundary and are not an offset extension of the Syrian arc. As Arabia penetrates Eurasia the Anatolian block is escaping to the west along the northern (right-lateral) and eastern (left-lateral) faults. Convergence of the Eurasian and Arabian plates resulted in ophiolite abduction (Late Cretaceous), followed by continent-continent collision (Miocene to present). The zone of collision is marked by the Bitlis-Zagrosa suture. Structural features associated with the collision include overthrusting, impactogens, and complexly folded and faulted mountain systems. Intensity and complexity of structuring decreases southward into open long-wavelength folds on the Arabian Platform. The fortuitous combination of rich source rocks, abundant reservoir rocks with primary and fracture porosity, and numerous trapping structures make this an extraordinary prolific hydrocarbon province. A structural and lithologic interpretation of 53 contiguous Landsat Multispectral Scanner scenes covering all of Syria, Iraq, and Kuwait, and portions of Turkey, Iran, Jordan, Lebanon, and Saudi Arabia has provided insights into the tectonic history of this area and its hydrocarbon accumulation.

  13. Mandibular degloving injury in an Arabian filly.

    PubMed

    Tirosh-Levy, Sharon; Tatz, Amos; Kelmer, Gal

    2013-06-01

    A 6-month-old Arabian filly escaped its handler while being led and slipped on pavement. The referring veterinarian recognized severe, soft tissue damage to the filly's lower jaw and referred the filly to the Veterinary Teaching Hospital for surgical management. PMID:24155453

  14. Saudi Arabian seismic-refraction profile: A traveltime interpretation of crustal and upper mantle structure

    USGS Publications Warehouse

    Mooney, W.D.; Gettings, M.E.; Blank, H.R.; Healy, J.H.

    1985-01-01

    The crustal and upper mantle compressional-wave velocity structure across the southwestern Arabian Shield has been investigated by a 1000-km-long seismic refraction profile. The profile begins in Mesozoic cover rocks near Riyadh on the Arabian Platform, trends southwesterly across three major Precambrian tectonic provinces, traverses Cenozoic rocks of the coastal plain near Jizan, and terminates at the outer edge of the Farasan Bank in the southern Red Sea. More than 500 surveyed recording sites were occupied, and six shot points were used, including one in the Red Sea. Two-dimensional ray-tracing techniques, used to analyze amplitude-normalized record sections indicate that the Arabian Shield is composed, to first order, of two layers, each about 20 km thick, with average velocities of about 6.3 km/s and 7.0 km/s, respectively. West of the Shield-Red Sea margin, the crust thins to a total thickness of less than 20 km, beyond which the Red Sea shelf and coastal plain are interpreted to be underlain by oceanic crust. A major crustal inhomogeneity at the northeast end of the profile probably represents the suture zone between two crustal blocks of different composition. Elsewhere along the profile, several high-velocity anomalies in the upper crust correlate with mapped gneiss domes, the most prominent of which is the Khamis Mushayt gneiss. Based on their velocities, these domes may constitute areas where lower crustal rocks have been raised some 20 km. Two intracrustal reflectors in the center of the Shield at 13 km depth probably represent the tops of mafic intrusives. The Mohorovic??ic?? discontinuity beneath the Shield varies from a depth of 43 km and mantle velocity of 8.2 km/s in the northeast to a depth of 38 km and mantle velocity of 8.0 km/s depth in the southwest near the Shield-Red Sea transition. Two velocity discontinuities occur in the upper mantle, at 59 and 70 km depth. The crustal and upper mantle velocity structure of the Arabian Shield is

  15. Crustal Deformation at the Arabian Plate-Boundary observed by InSAR

    NASA Astrophysics Data System (ADS)

    Jonsson, S.; Cavalié, O.; Akoglu, A. M.; Wang, T.; Xu, W.; Feng, G.; Dutta, R.; Abdullin, A. K.

    2013-12-01

    The Arabian plate is bounded by a variety of active plate boundaries, with extension in the Red Sea and Gulf of Aden to the south, compression in Turkey and Iran to the north, and transform faults to the west and to the east. Internally, however, the Arabian plate has been shown to be tectonically rather stable, despite evidence of recent volcanism and earthquake faulting. We use InSAR observations to study recent tectonic and volcanic activity at several locations at the Arabian plate boundary as well within the plate itself. The region near the triple junction between the Arabian, Eurasian, and Anatolian plates has often been the focus of studies on continental deformation behavior and interseismic deformation. Here we use large-scale InSAR data processing to map the deformation near the triple junction and find the deformation to be focused on major faults with little intra-plate deformation. The eastern part of the East Anatolian Fault appears to have a very shallow locking depth with limited fault-normal deformation. Several major earthquakes that have occurred in recent years on the Arabian plate boundary, including the 2011 magnitude 7.1 Van earthquake in eastern Turkey. It occurred as a result of convergence of the Arabian plate towards Eurasia and caused significant surface deformation that we have analyzed with multiple coseismic InSAR, GPS, and coastal uplift observations. We use high-resolution Cosmo-Skymed and TerraSAR-X data to derive 3D coseismic displacements from offsets alone, as some of the interferograms are almost completely incoherent. By identifying point-like targets within the images, we were able to derive accurate pixel offsets between SAR sub-images containing such targets, which we used to estimate the 3D coseismic displacements. The derived 3D displacement field helped in constraining the causative northward dipping thrust-fault. The Qadimah fault is a recently discovered fault located on the Red Sea coast north of Jeddah and under the

  16. Population genetics of four heavily exploited shark species around the Arabian Peninsula

    PubMed Central

    Spaet, Julia L Y; Jabado, Rima W; Henderson, Aaron C; Moore, Alec B M; Berumen, Michael L

    2015-01-01

    The northwestern Indian Ocean harbors a number of larger marine vertebrate taxa that warrant the investigation of genetic population structure given remarkable spatial heterogeneity in biological characteristics such as distribution, behavior, and morphology. Here, we investigate the genetic population structure of four commercially exploited shark species with different biological characteristics (Carcharhinus limbatus, Carcharhinus sorrah, Rhizoprionodon acutus, and Sphyrna lewini) between the Red Sea and all other water bodies surrounding the Arabian Peninsula. To assess intraspecific patterns of connectivity, we constructed statistical parsimony networks among haplotypes and estimated (1) population structure; and (2) time of most recent population expansion, based on mitochondrial control region DNA and a total of 20 microsatellites. Our analysis indicates that, even in smaller, less vagile shark species, there are no contemporary barriers to gene flow across the study region, while historical events, for example, Pleistocene glacial cycles, may have affected connectivity in C. sorrah and R. acutus. A parsimony network analysis provided evidence that Arabian S. lewini may represent a population segment that is distinct from other known stocks in the Indian Ocean, raising a new layer of conservation concern. Our results call for urgent regional cooperation to ensure the sustainable exploitation of sharks in the Arabian region. PMID:26120422

  17. Population genetics of four heavily exploited shark species around the Arabian Peninsula.

    PubMed

    Spaet, Julia L Y; Jabado, Rima W; Henderson, Aaron C; Moore, Alec B M; Berumen, Michael L

    2015-06-01

    The northwestern Indian Ocean harbors a number of larger marine vertebrate taxa that warrant the investigation of genetic population structure given remarkable spatial heterogeneity in biological characteristics such as distribution, behavior, and morphology. Here, we investigate the genetic population structure of four commercially exploited shark species with different biological characteristics (Carcharhinus limbatus, Carcharhinus sorrah, Rhizoprionodon acutus, and Sphyrna lewini) between the Red Sea and all other water bodies surrounding the Arabian Peninsula. To assess intraspecific patterns of connectivity, we constructed statistical parsimony networks among haplotypes and estimated (1) population structure; and (2) time of most recent population expansion, based on mitochondrial control region DNA and a total of 20 microsatellites. Our analysis indicates that, even in smaller, less vagile shark species, there are no contemporary barriers to gene flow across the study region, while historical events, for example, Pleistocene glacial cycles, may have affected connectivity in C. sorrah and R. acutus. A parsimony network analysis provided evidence that Arabian S. lewini may represent a population segment that is distinct from other known stocks in the Indian Ocean, raising a new layer of conservation concern. Our results call for urgent regional cooperation to ensure the sustainable exploitation of sharks in the Arabian region. PMID:26120422

  18. Assessing the potential of Landsat 8 OLI for retrieving salinity in the hypersaline Arabian Gulf

    NASA Astrophysics Data System (ADS)

    Zhao, Jun; Temimi, Marouane

    2016-04-01

    The Arabian Gulf, located in an arid region in the Middle East, has high salinity that can exceed 43 practical salinity units (psu) due to its special conditions, such as high evaporation, low precipitation, and desalination discharge. In this study, a regional algorithm was developed to retrieve salinity using in situ measurements conducted between June 2013 and November 2014 along the western coast of Abu Dhabi, United Arab Emirates (UAE). A multivariate linear regression model using the visible bands of Operational Land Imager (OLI) was proposed and indicated good performance with a determination coefficient (R2) of 0.7. The algorithm was then applied to an OLI scene, which revealed the spatial distribution of salinity over the study area. The findings are favorable for better interpretation of the complex water mass exchange between the Arabian Gulf and the Sea of Oman through the Strait of Hormuz, validating salinity from numerical models, studying the effects of anthropogenic activities and climate change on ecosystem in the hypersaline Arabian Gulf, etc.

  19. Seasonal characteristics of the large-scale moisture flux transport over the Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Athar, H.; Ammar, K.

    2016-05-01

    The relationship between the lower tropospheric (1000 to 850 hPa) large-scale moisture flux transport and the precipitation over the Arabian Peninsula (AP), on a seasonal basis, using the NCEP-NCAR gridded dataset for the 53-year period (1958-2010), is investigated. The lower tropospheric moisture flux divergence occurs due to the Hadley cell-based descending air over the AP, as well as due to the presence of Somali jet in dry season (June to September) for the southern (≤22° N) AP domain, leading to significantly reduced precipitation in the AP. The AP thus acts more as a net transporter of moisture flux from adjacent Sea areas to nearby regions. The North Atlantic Oscillation (NAO) and the Artic Oscillation (AO) climatic indices are found to modulate significantly the net seasonal moisture flux into the AP region animating from the Mediterranean Sea, and the Arabian Sea, both for the northern (≥22° N) and southern AP domains.

  20. Molecular biodiversity of Red Sea demosponges.

    PubMed

    Erpenbeck, Dirk; Voigt, Oliver; Al-Aidaroos, Ali M; Berumen, Michael L; Büttner, Gabriele; Catania, Daniela; Guirguis, Adel Naguib; Paulay, Gustav; Schätzle, Simone; Wörheide, Gert

    2016-04-30

    Sponges are important constituents of coral reef ecosystems, including those around the Arabian Peninsula. Despite their importance, our knowledge on demosponge diversity in this area is insufficient to recognize, for example, faunal changes caused by anthropogenic disturbances. We here report the first assessment of demosponge molecular biodiversity from Arabia, with focus on the Saudi Arabian Red Sea, based on mitochondrial and nuclear ribosomal molecular markers gathered in the framework of the Sponge Barcoding Project. We use a rapid molecular screening approach on Arabian demosponge collections and analyze results in comparison against published material in terms of biodiversity. We use a variable region of 28S rDNA, applied for the first time in the assessment of demosponge molecular diversity. Our data constitutes a solid foundation for a future more comprehensive understanding of sponge biodiversity of the Red Sea and adjacent waters. PMID:26776057

  1. Deposition Rates and Characterization of Arabian Mineral Dust

    NASA Astrophysics Data System (ADS)

    Puthan Purakkal, J.; Stenchikov, G. L.; Engelbrecht, J. P.

    2015-12-01

    Airborne mineral dust directly and indirectly impacts on global climate, continental and marine biochemistry, human and animal health, agriculture, equipment, and visibility. Annual global dust emissions are poorly known with estimates differing by a factor of at least two. Local dust emission and deposition rates are even less quantified. Dust deposition rate is a key parameter, which helps to constrain the modeled dust budget of the atmosphere. However, dust deposition remains poorly known, due to the limited number of reliable measurements. Simulations and satellite observations suggest that coastal dusts contribute substantially to the total deposition flux into the Red Sea. Starting December 2014, deposition samplers, both the "frisbee" type, and passive samplers for individual particle scanning electron microscopy were deployed at King Abdullah University of Science and Technology (KAUST), along the Red Sea in Saudi Arabia. Sampling periods of one month were adopted. The deposition rates range from 3 g m-2 month-1 for fair weather conditions to 23 g m-2 month-1 for high dust events. The X-ray diffraction (XRD) analyses of deposited dust samples show mineralogical compositions different from any of the parent soils, the former consisting mainly of gypsum, calcite, and smaller amounts of albite, montmorillonite, chlorite, quartz and biotite. The deposited dust samples on the other hand contain more gypsum and less quartz than the previously collected soil samples. This presentation discusses the results from XRD, chemical analysis and SEM-based individual particle analysis of the soils and the deposited dust samples. The monthly dust accumulation rates and their seasonal and spatial variability are compared with the regional model predictions. Data from this study provide an observational basis for validating the regional dust mass balance along the Arabian Red Sea coastal plain.

  2. NASA Sees Heavy Rain in Arabian Sea Tropical Cyclone

    NASA Video Gallery

    On June 29, GPM showed Tropical Cyclone 02A had a few powerful convective thunderstorms southwest of the center of circulation were dropping rain at the extreme rate of over 209 mm (8.2 inches) per...

  3. Neotectonic map of Syria and some aspects of Late Cenozoic evolution of the northwestern boundary zone of the Arabian plate

    NASA Astrophysics Data System (ADS)

    Rukieh, M.; Trifonov, V. G.; Dodonov, A. E.; Minini, H.; Ammar, O.; Ivanova, T. P.; Zaza, T.; Yusef, A.; Al-Shara, M.; Jobaili, Y.

    2005-09-01

    The neotectonic map of Syria, 1:500,000, was compiled by the authors in 2003-2004. The map shows tectonic features formed or continued to develop during the Neogene and Quaternary in Syria and adjacent territories, including the Mediterranean realm. The neotectonic structure of the region was formed as a result of three phases of deformation. During the Early Miocene first phase, the Arabian plate moved along the Dead Sea-Jordan segments of the Levant (Dead Sea) transform fault zone, Roum fault and its continuation in the continental slope of the Mediterranean. The chain of the coastal anticlines in the "Arabian" side of the transform zone and the Lattaqie oblique (sinistral-thrust) boundary fault zone in the north were formed under the NNW-trending compression. The Lattaqie zone continued by the Cyprus arc in the west and by the Taurus (Bitlis) thrust in the east and further by the Main Thrust of the Zagros. After "quiet" (for Syria) epoch of the Middle Miocene when the Arabian plate moved to the NE, during the Late Miocene second phase of deformation, the Arabian plate moved again to the NNW along the same transform boundary. But a part of the Late Miocene plate motion (up to 20 km) resulted by shortening in the Anti-Leban-Palmyride fold-thrust belt that separated the Aleppo block from the main part of the Arabian plate. During the Pliocene-Quaternary third phase of deformation, the recent structural pattern of the Levant zone was formed in Lebanon and the northwestern Syria. At the same time, the Serghaya and smaller sinistral faults branched out the Levant zone and the system of the W-E-trending convex to the south dextral faults ruptured the Palmyrides and the stable part of the Arabian plate. The total Pliocene-Quaternary sinistral offset on the young Levant zone segments and the associated faults has reached 35-40 km, like on the Dead Sea-Jordan segments of the Levant fault zone. The faults, demonstrating the Pliocene-Quaternary activity are still active now

  4. The climatology of dust aerosol over the arabian peninsula

    NASA Astrophysics Data System (ADS)

    Shalaby, A.; Rappenglueck, B.; Eltahir, E. A. B.

    2015-01-01

    Dust storms are considered to be a natural hazard over the Arabian Peninsula, since they occur all year round with maximum intensity and frequency in Spring and Summer. The Regional Climate Model version 4 (RegCM4) has been used to study the climatology of atmospheric dust over the Arabian Peninsula from 1999 to 2012. This relatively long simulation period samples the meteorological conditions that determine the climatology of mineral dust aerosols over the Arabian Peninsula. The modeled Aerosol Optical Depth (AOD) has been compared against ground-based observations of three Aerosol Robotic Network (AERONET) stations that are distributed over the Arabian Peninsula and daily space based observations from the Multi-angle Imaging SpectroRadiometer (MISR), the Moderate resolution Imaging SpectroRadimeter (MODIS) and Ozone Monitoring Instrument (OMI). The large scale atmospheric circulation and the land surface response that lead to dust uplifting have been analyzed. While the modeled AOD shows that the dust season extends from March to August with two pronounced maxima, one over the northern Arabian Peninsula in March with AOD equal to 0.4 and one over the southern Arabian Peninsula in July with AOD equal to 0.7, the observations show that the dust season extends from April to August with two pronounced maxima, one over the northern Arabian Peninsula in April with AOD equal to 0.5 and one over the southern Arabian Peninsula in July with AOD equal to 0.5. In spring a high pressure dominates the Arabian Peninsula and is responsible for advecting dust from southern and western part of the Arabian Peninsula to northern and eastern part of the Peninsula. Also, fast developed cyclones in northern Arabian Peninsula are responsible for producing strong dust storms over Iraq and Kuwait. However, in summer the main driver of the surface dust emission is the strong northerly wind ("Shamal") that transport dust from the northern Arabian Peninsula toward south parallel to the

  5. Continental lithosphere of the Arabian Plate: A geologic, petrologic, and geophysical synthesis

    NASA Astrophysics Data System (ADS)

    Stern, Robert J.; Johnson, Peter

    2010-07-01

    The Arabian Plate originated ˜ 25 Ma ago by rifting of NE Africa to form the Gulf of Aden and Red Sea. It is one of the smaller and younger of the Earth's lithospheric plates. The upper part of its crust consists of crystalline Precambrian basement, Phanerozoic sedimentary cover as much as 10 km thick, and Cenozoic flood basalt (harrat). The distribution of these rocks and variations in elevation across the Plate cause a pronounced geologic and topographic asymmetry, with extensive basement exposures (the Arabian Shield) and elevations of as much as 3000 m in the west, and a Phanerozoic succession (Arabian Platform) that thickens, and a surface that descends to sea level, eastward between the Shield and the northeastern margin of the Plate. This tilt in the Plate is partly the result of marginal uplift during rifting in the south and west, and loading during collision with, and subduction beneath, the Eurasian Plate in the northeast. But a variety of evidence suggests that the asymmetry also reflects a fundamental crustal and mantle heterogeneity in the Plate that dates from Neoproterozoic time when the crust formed. The bulk of the Plate's upper crystalline crust is Neoproterozoic in age (1000-540 Ma) reflecting, in the west, a 300-million year process of continental crustal growth between ˜ 850 and 550 Ma represented by amalgamated juvenile magmatic arcs, post-amalgamation sedimentary and volcanic basins, and granitoid intrusions that make up as much as 50% of the Shield's surface. Locally, Archean and Paleoproterozoic rocks are structurally intercalated with the juvenile Neoproterozoic rocks in the southern and eastern parts of the Shield. The geologic dataset for the age, composition, and origin of the upper crust of the Plate in the east is smaller than the database for the Shield, and conclusions made about the crust in the east are correspondingly less definitive. In the absence of exposures, furthermore, nothing is known by direct observation about the

  6. Stratigraphy and paleogeography of the Cretaceous in Arabian Peninsula

    SciTech Connect

    Alsharhan, A.S.; Nairn, A.E.M.

    1986-05-01

    The Cretaceous of the Arabian Peninsula is divided into three major units by regional unconformities: Lower Cretaceous Thamama Group (Berriasian-middle Aptian), middle Cretaceous Wasia Group (Albian-Turonian), and Upper Cretaceous Aruma Group (Coniacian-Maestrichtian). The profusion of named stratigraphic units in the area reflects not only the lithologic variation resulting from facies changes, but also terminologies adopted by different companies. The authors provide a stratigraphic nomenclature defining standard type sections and indicate synonymies, which follow the recommendation of 10th Geological Liaison Meeting and hence are acceptable to operators in the area. The sedimentologic history of the area was presented in a series of paleogeographic maps, which they relate to the regional tectonic framework. The maps show a predominantly carbonate shelf ramp bordering a land area to the north and west. The principal change in depositional environment occurs during the Upper Cretaceous, as a result of tectonic activity. Less significant changes are attributed to eustatic sea level fluctuations, on which tilting caused by tectonic movement may be superposed during the Lower and middle Cretaceous. The major producing horizons lie below the regional unconformities; secondary porosity in the shelf reefal buildups was developed during subaerial exposure in the Shuaiba Formation (early-middle Aptian), in the Mishrif Formation (late Cenomanian), and in the Simsima Formation (Maestrichtian).

  7. Data Collection in the Arabian Peninsula for Nuclear Explosion Monitoring

    SciTech Connect

    Rodgers, A; Tkalcic, H; Al-Amri, A M S

    2003-07-11

    We report results from the second year of our project (ROA0101-35) to collect seismic event and waveform data recorded in and around the Arabian Peninsula. This effort involves several elements. We have a temporary broadband seismic station operating near the IMS primary array site (PS38) in central Saudi Arabia. We recently installed two temporary broadband stations in the United Arab Emirates (funded by NNSA NA-24 Office of Non-Proliferation & International Security). We are working with King Abdulaziz city for Science and Technology to collect and analyze data from the Saudi National Seismic Network, that consist of 37 digital three-component stations (26 broadband and 11 short-period). We are collaborating with Kuwait Institute for Scientific Research (KISR) to analyze data from their 8 station national seismic network. We participated in the Workshop on Reference Events odnear the Dead Sea Rift held in Paris, France in October 2002. In this paper we present results of these efforts including integration of the raw data into LLNL's Seismic Research Database and preliminary analysis of event locations and source parameters and inference of earth structure.

  8. Upper mantle seismic velocity structure beneath the Kenya Rift and the Arabian Shield

    NASA Astrophysics Data System (ADS)

    Park, Yongcheol

    Upper mantle structure beneath the Kenya Rift and Arabian Shield has been investigated to advance our understanding of the origin of the Cenozoic hotspot tectonism found there. A new seismic tomographic model of the upper mantle beneath the Kenya Rift has been obtained by inverting teleseismic P-wave travel time residuals. The model shows a 0.5--1.5% low velocity anomaly below the Kenya Rift extending to about 150 km depth. Below ˜150 km depth, the anomaly broadens to the west toward the Tanzania Craton, suggesting a westward dip to the structure. The P- and S-wave velocity structure beneath the Arabian Shield has been investigated using travel-time tomography. Models for the seismic velocity structure of the upper mantle between 150 and 400 depths reveal a low velocity region (˜1.5% in the P model and ˜3% in the S model) trending NW-SE along the western side of the Arabian Shield and broadening to the northeast beneath the MMN volcanic line. The models have limited resolution above 150 km depth everywhere under the Shield, and in the middle part of the Shield the resolution is limited at all depths. Rayleigh wave phase velocity measurements have been inverted to image regions of the upper mantle under the Arabian Shield not well resolved by the body wave tomography. The shear wave velocity model obtained shows upper mantle structure above 200 km depth. A broad low velocity region in the lithospheric mantle (depths of ≤ ˜100 km) across the Shield is observed, and below ˜150 km depth a region of low shear velocity is imaged along the Red Sea coast and MMN volcanic line. A westward dipping low velocity zone beneath the Kenya Rift is consistent with an interpretation by Nyblade et al. [2000] suggesting that a plume head is located under the eastern margin of the Tanzania Craton, or alternatively a superplume rising from the lower mantle from the west and reaching the surface under Kenya [e.g., Debayle et al., 2001; Grand et al., 1997; Ritsema et al., 1999]. For

  9. The uplift history of the Arabian Plateau as inferred from geomorphologic analysis of its northwestern edge

    NASA Astrophysics Data System (ADS)

    Bar, Oded; Zilberman, Ezra; Feinstein, Shimon; Calvo, Ran; Gvirtzman, Zohar

    2016-03-01

    The Arabian Plateau (AP) is an Oligocene sub-horizontal regional planation surface, extending throughout the western half of the Arabian Peninsula. Its present elevation of about 1 km required a prominent uplift since the Late Eocene. In order to reconstruct the uplift history, we documented abundant abrasive and fluvial terraces that were left along and across the raised Judea Mountains (JM), which comprised the NW edge of the AP. Using the ages of those terraces and the differences in height between them, we found that the JM was uplifted in three major phases: a few hundred meters during the Late Eocene-Early Oligocene, ~ 500 m during the Early Miocene-early Middle Miocene, and ~ 350 m during the Late Pliocene. The two earliest uplift phases predate the formation of the Dead-Sea Transform (DST), which today separates the JM from the AP, meaning that these two phases affected the continuous rigid lithosphere extending southeastwards to the AP interiors. Moreover, restoration of the paleogeography predating the lateral offset along the DST eliminates the main height differences across it and suggests that the DST does not play a major role in the vertical position of its bordering plates, but rather forms a relatively narrow deformation strip within the AP. Those two early phases of uplift can be corroborated by previous thermochronology studies, which exhibit similar ages around the Red Sea but may reflect the uplift age of the entire region. The present sub-horizontal morphology of the AP is in contrast to the presumed original northeastward drainage and may suggest a subsequent long-wave moderate tilting to the SW. Three possible mechanisms were suggested for the uplift of the AP: a long wavelength flexure of the Arabian plate during early stages of the uplift, and lithospheric thinning or dynamic topography during later stages of the uplift.

  10. Probiotics in the Arabian Gulf Region

    PubMed Central

    Senok, Abiola C.

    2009-01-01

    Objective Available reports on adherence to recommended guidelines for labeling of probiotic products are based on assessment of these products in developed countries. In the Arabian Gulf region, there is a paucity of data on the characterization of probiotic products and an absence of local guidelines for their labeling. This study, carried out in the United Arab Emirates (UAE), represents the first evaluation of probiotic products available in the Arabian Peninsula. Methods Probiotic products were purchased over the counter from a variety of sources, including pharmacies, healthfood stores, and supermarkets across the UAE. All identified products were listed and information regarding type of product preparation and labeling information were recorded. Results A total of 37 probiotic products, 15 dairy-based and 22 non-dairy-based were identified. The dairy products comprised of 12 yogurts, two fermented milk products and one powdered baby formula. The majority of non-dairy products were in capsule form (n = 16). While all the non-dairy products gave information about the strain of probiotic microorganism and number present at time of manufacture, this information was provided for only one dairy-based product. Strains of Lactobacillus acidophilus were the most common probiotic organisms identified. However, one probiotic product listed Enterococcus faecalis (750 million viable bacteria per capsule) as a component. With the exception of one non-dairy-based product, all health-related claims were structure/function statements, according to the US Food and Drug Administration nomenclature. Conclusion These findings indicate that a wide variety of probiotic products are available in the Arabian Gulf. Development of guidelines for labeling of these probiotic products and use of structure/function statements and health claims should be addressed. PMID:19266044

  11. Arabian plate hydrocarbon geology and potential

    SciTech Connect

    Beydoun, Z.R.

    1991-01-01

    This book provides a thought-provoking, succinct presentation of the geologic evolution and hydrocarbon potential of the world's most prolific petroleum province. The fascinating subjects discussed and documented include: What are the unique geologic factors that make the Middle East such a prolific province Where are the future Mesozoic and Tertiary plays What is the virtually untapped potential of the Paleozoic section What are the play potentials for underexplored areas such as Jordan, Syria, Yemen How are deeper drilling results shaping and modifying concepts of the Arabian plate history and pointing the way to future hydrocarbon targets

  12. Geochronologic data for the Arabian Shield

    USGS Publications Warehouse

    Aldrich, Lyman Thomas; Brown, G.F.; Hedge, Carl; Marvin, Richard

    1978-01-01

    The radiometric ages reported below were completed during the period 1957-1936. the rock samples were provided and examined petrographically by Glen F. Brown and his associates at the U.S. Geological Survey. The 25 Rb-Sr ages of biotites and feldspars and the 25 K-Ar ages of biotites, hornblendes, and total rock samples constituted the initial suite of ages for the Arabian Shield. Zircons in the quantity required for analysis were not found in any of the rocks examined.

  13. Interpretation of the data of USGS seismic refraction profile across the Arabian Shield in western Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Prodehl, C.

    Based on the record sections distributed a preliminary traveltime interpretation assuming horizontally flat layering is presented in the form of velocity-depth functions and a corresponding cross section of the lithosphere to a depth of 60 to 80 km across the Arabian Shield in western Saudi Arabia. The crust thickens abruptly from 15 km beneath the Red Sea Rift to about 40 km beneath the Arabian Shield. The upper crust of the western Arabian Shield yields relatively high-velocity material at about 10 km depth underlain by velocity inversions, while the upper crust of the eastern Shield is relatively uniform. The lower crust with a velocity of about 7 km/s is underlain by a transitional crust-mantle boundary. For the lower lithosphere beneath 40 km depth a laterally discontinuous lamellar structure may exist where high-velocity zones are mixed with zones of lower velocities. Beneath the crust-mantle boundary of the Red Sea Rift strong velocity inversions with velocities as low as 6.0 km/s may be encountered between 25 and 44 km depth. This model was prepared before the CCSS workshop. The model was tested using ray-tracing and amplitude studies and agreed well with observed traveltimes, except between shotpoints 5 and 6.

  14. Assessment of arsenic in coastal sediments, seawaters and molluscs in the Tarut Island, Arabian Gulf, Saudi Arabia

    NASA Astrophysics Data System (ADS)

    El-Sorogy, Abdelbaset S.; Youssef, Mohamed; Al-Kahtany, Khaled; Al-Otaiby, Naif

    2016-01-01

    In order to assess arsenic on the Tarut coast, Saudi Arabian Gulf, 38 sediment samples, 26 seawater samples and 40 gastropod and bivalve specimens were collected for analyses by Inductively Coupled Plasma-Mass Spectrometer. The Enrichment Factor (EF), the Geoaccumulation Index (Igeo) and the Contamination Factor (CF) indicated that coastal sediments of Tarut Island are severely enriched, strongly polluted and very highly contaminated with arsenic as a result of anthropogenic inputs. Comparison with arsenic in coastal sediments, seawaters and molluscs in the Red Sea, the Arabian Gulf and abroad coasts suggested that the studied samples have higher concentrations of As. The suggested natural sources of arsenic in the study area are the weathering and decomposition of neighboring deserts. The anthropogenic sources include the land reclamation, petrochemical industries, boat exhaust emissions, oil leakage, desalination plants and sewage effluents. These anthropogenic sources are the dominant sources of As in the study area and mostly came from Al Jubail industrial city to the north.

  15. Episodic sea-floor spreading in the Southern Red Sea

    NASA Astrophysics Data System (ADS)

    Almalki, Khalid A.; Betts, Peter G.; Ailleres, Laurent

    2014-03-01

    The Red Sea represents the most spectacular example of a juvenile ocean basin on the modern Earth. Synthesis of regional aeromagnetic data, gravity data, seismic refraction data coupled with structural mapping from the Farasan Islands suggest that the opening of the Red Sea is complex and episodic. Modeling of magnetic and gravity data constrained by seismic refraction data reveals the Arabian Shelf is underlain by oceanic and transitional crust and that mafic diking and intrusions are focused at the continental-transitional crust boundary. This relationship is interpreted to indicate that early Miocene diking along the Arabian Escarpment heralded termination of oceanic basin formation and a shift in the locus of extension focused from a central mid-ocean ridge spreading center to the continental-transitional crust zone. Uplift along the Arabian Escarpment caused erosion and Middle to Late Miocene sedimentation of the Farasan Bank onto existing oceanic crust, suggesting that the extensive sedimentary banks of the southern Red Sea are not passive margins. Re-initiation of spreading occurred at ca 5 Ma. Pliocene to Pleistocene Shelf reef systems (Farasan Islands), developed on the flanks of the spreading ridge, are extensively overprinted by normal faults, suggesting that not all crustal extension is accommodated by active spreading.

  16. Environmental protection in the Arabian Gulf

    SciTech Connect

    Al-Minhali, A.A.N.

    1996-12-31

    The Arabian Gulf had been subjected to tremendous development activities in the past 40 years, this, in addition to two fierce wars which must have had some impact on the marine environment. This paper will investigate and summarize through review of numerous scientific studies, the recommended applied and or implemented strategies for conservation and how these may have an impact on the Offshore Oil and Gas Industry. The conclusions and recommendations made (in both, global terms and for oil and gas industry) primarily represent the author`s own views and in some parts acknowledged views of a number of professionals who were asked to contribute their vision on the future of protection of the Gulf marine environment. Whilst this paper is directed towards the Marine Environment, similar conclusions can be drawn for land and atmospheric issues.

  17. Carbon isotope stratigraphy of the upper Kharaib and Shuaiba formations: Implications for the Early Cretaceous evolution of the Arabian Gulf Region

    SciTech Connect

    Vahrenkamp, V.C.

    1996-05-01

    The carbon isotope profiles of shallow-marine carbonates from the Barremian-Aptian Kharaib and Shuaiba formations of the Arabian Gulf region range between 0.5 and 7{per_thousand} {delta}{sup 13}C PDB (Peedee belemnite). Systematic variations can be correlated with isotope profiles reported from Tethyan pelagic limestone sequences. The detailed correspondence between the isotopic signature of the relatively well-dated pelagic limestones and the poorly dated shallow-water limestones from the Arabian Gulf region suggests that global marine carbon isotope changes apparently affected deep-sea and shallow-water carbonate sediments similarly and at a similar time resolution. Although oxygen isotopes have been reset during diagenesis, carbon isotopes appear to have maintained their primary marine signature through time. No evidence has been found to connect carbon isotope trends to subaerial exposure or later meteoric diagenesis. In combination with other data, the investigated carbon isotope profiles can be used for basin-to-platform and regional correlations beyond the current resolution of biostratigraphy in shallow-water limestones. Carbon isotope stratigraphy confirms significant hiatuses in the investigated shallow-water carbonate sequences. Using carbon isotope trends as a proxy for sea level fluctuations, the carbon isotope cycles of the late Early Cretaceous of the Arabian Gulf region may represent four cycles of rising and falling sea level with a duration corresponding to that of third-order sea level fluctuations. Regional correlations derived from isotope trends provide a scenario for the larger scale stratigraphic evolution of the Arabian peninsula during the end of the Early Cretaceous.

  18. Distribution and Phase Association of Some Major and Trace Elements in the Arabian Gulf Sediments

    NASA Astrophysics Data System (ADS)

    Basaham, A. S.; El-Sayed, M. A.

    1998-02-01

    Twenty-four sediment samples were collected from the Arabian Gulf (ROPME Sea) and analysed for their grain size distribution and carbonate contents as well as the major elements Ca, Mg, Fe and Al and macro and trace elements Mn, Sr, Ba, Zn, Cu, Cr, V, Ni and Hg. Concentration of trace elements are found comparable to previous data published for samples taken before and after the Gulf War, and reflect the natural background level. Grain size analyses, aluminium and carbonate measurements support the presence of two major sediment types: (1) a terrigenous, fine-grained and Al rich type predominating along the Iranian side; and (2) a coarse-grained and carbonate rich type predominating along the Arabian side of the Gulf. Investigation of the correlation of the elements analysed with the sediment type indicates that they could be grouped under two distinct associations: (1) carbonate association including Ca and Sr; and (2) terrigenous association comprising Al, Fe, Mg, Ba, Mn, Zn, Cu, Cr, V, Ni and Hg. Element/Al ratios calculated for the mud non-carbonate fraction indicate that the Euphrates and Tigris rivers have minor importance as sediment sources to the Gulf. Most of the elements have exceptionally high aluminium ratios in sediments containing more than 85-90% carbonate. These sediments are restricted to the southern and south-eastern part of the area where depth is shallow and temperature and salinity are high. Both biological accumulation and chemical and biochemical coprecipitation could be responsible for this anomaly.

  19. Rapid late Pleistocene/Holocene uplift and coastal evolution of the southern Arabian (Persian) Gulf

    NASA Astrophysics Data System (ADS)

    Wood, Warren W.; Bailey, Richard M.; Hampton, Brian A.; Kraemer, Thomas F.; Lu, Zhong; Clark, David W.; James, Rhodri H. R.; Al Ramadan, Khalid

    2012-03-01

    The coastline along the southern Arabian Gulf between Al Jubail, Kingdom of Saudi Arabia, and Dubai, UAE, appears to have risen at least 125 m in the last 18,000 years. Dating and topographic surveying of paleo-dunes (43-53 ka), paleo-marine terraces (17-30 ka), and paleo-marine shorelines (3.3-5.5 ka) document a rapid, > 1 mm/a subsidence, followed by a 6 mm/a uplift that is decreasing with time. The mechanism causing this movement remains elusive but may be related to the translation of the coastal area through the backbasin to forebulge hinge line movement of the Arabian plate or, alternatively, by movement of the underlying Infracambrian-age Hormuz salt in response to sea-level changes associated with continental glaciation. Independent of the mechanism, rapid and episodic uplift may impact the design of engineering projects such as nuclear power plants, airports, and artificial islands as well as the interpretation of sedimentation and archeology of the area.

  20. Monitoring of oil pollution in the Arabian Gulf based on medium resolution satellite imagery

    NASA Astrophysics Data System (ADS)

    Zhao, J.; Ghedira, H.

    2013-12-01

    A large number of inland and offshore oil fields are located in the Arabian Gulf where about 25% of the world's oil is produced by the countries surrounding the Arabian Gulf region. Almost all of this oil production is shipped by sea worldwide through the Strait of Hormuz making the region vulnerable to environmental and ecological threats that might arise from accidental or intentional oil spills. Remote sensing technologies have the unique capability to detect and monitor oil pollutions over large temporal and spatial scales. Synoptic satellite imaging can date back to 1972 when Landsat-1 was launched. Landsat satellite missions provide long time series of imagery with a spatial resolution of 30 m. MODIS sensors onboard NASA's Terra and Aqua satellites provide a wide and frequent coverage at medium spatial resolution, i.e. 250 m and 500, twice a day. In this study, the capability of medium resolution MODIS and Landsat data in detecting and monitoring oil pollutions in the Arabian Gulf was tested. Oil spills and slicks show negative or positive contrasts in satellite derived RGB images compared with surrounding clean waters depending on the solar/viewing geometry, oil thickness and evolution, etc. Oil-contaminated areas show different spectral characteristics compared with surrounding waters. Rayleigh-corrected reflectance at the seven medium resolution bands of MODIS is lower in oil affected areas. This is caused by high light absorption of oil slicks. 30-m Landsat image indicated the occurrence of oil spill on May 26 2000 in the Arabian Gulf. The oil spill showed positive contrast and lower temperature than surrounding areas. Floating algae index (FAI) images are also used to detect oil pollution. Oil-contaminated areas were found to have lower FAI values. To track the movement of oil slicks found on October 21 2007, ocean circulations from a HYCOM model were examined and demonstrated that the oil slicks were advected toward the coastal areas of United Arab

  1. Continental margin evolution of the northern Arabian platform in Syria

    SciTech Connect

    Best, J.A.; Barazangi, M. ); Al-Saad, D.; Sawaf, T.; Gebran, A. )

    1993-02-01

    Synthesis of available geological and geophysical data in the Syrian Arab Republic permits a descriptive account of the pre-Cenozoic geologic history of the northern Arabian platform. The northern Arabian platform appears to be a composite plate similar up to that interpreted in the rocks of the Arabian shield. The structural and stratigraphic relationships of the Paleozoic and Mesozoic sedimentary sections in Syria record the transformation of an eastward-facing Gondwana passive margin in the early Paleozoic into a westward-facing Levantine margin in the Mesozoic, at which time the northern platform was closely associated with the creation of the eastern Mediterranean basin. Timing of the margin transformation is inferred from the orientation and thickness variations of Lower Triassic rocks, but the transformation may have initiated as early as the Permian. The diversity and timing of geological features in Syria suggest that the northern Arabian platform did not behave as a rigid plate throughout its geological history. The present-day Palmyride mountain belt, located within the northern Arabian platform in Syria and initiated in the early Mesozoic as a northeast-trending rift nearly perpendicular to the Levantine margin, subsequently was inverted in the Cenozoic by transpression. The location of the rift may be associated with the reactivation of a zone of crustal weakness, i.e., a Proterozoic suture zone previously proposed from modeling of Bouguer gravity data. Thus, the northern and southern parts of the Arabian platform are similar in their respective geologic histories during the Proterozoic and Paleozoic; however, the northern Arabian platform was greatly affected by Mesozoic rifting and the creation of the eastern Mediterranean basin during the Mesozoic. 13 figs.

  2. Dynamics of sea level variations in the coastal Red Sea

    NASA Astrophysics Data System (ADS)

    Churchill, James; Abulnaja, Yasser; Nellayaputhenpeedika, Mohammedali; Limeburner, Richard; Lentz, Steven

    2016-04-01

    Sea level variations in the central Red Sea coastal zone span a range of roughly 1.2 m. Though relatively small, these water level changes can significantly impact the environment over the shallow reef tops prevalent in the central Red Sea, altering the water depth by a factor or two or more. While considerable scientific work has been directed at tidal and seasonal variations of Red Sea water level, very little attention has been given to elevation changes in an 'intermediate' frequency band, with periods of 2-30 d, even though motions in this band account for roughly half of the sea level variance in central Red Sea. We examined the sea level signal in this band using AVISO sea level anomaly (SLA) data, COARDAS wind data and measurements from pressure sensors maintained for more than five years at a number of locations in Saudi Arabian coastal waters. Empirical orthogonal function analysis of the SLA data indicates that longer-period (10-30 d) sea level variations in the intermediate band are dominated by coherent motions in a single mode that extends over most of the Red Sea axis. Idealized model results indicate that this large-scale mode of sea level motion is principally due to variations in the large-scale gradient of the along-axis wind. Our analysis indicates that coastal sea level motions at shorter periods (2-10 d) are principally generated by a combination of direct forcing by the local wind stress and forcing associated with large-scale wind stress gradients. However, also contributing to coastal sea level variations in the intermediate frequency band are mesoscale eddies, which are prevalent throughout the Red Sea basin, have a sea level signal of 10's of cm and produce relatively small-scale (order 50 km) changes in coastal sea level.

  3. Perspective View, Landsat Overlay, Salalah, Oman, Southern Arabian Peninsula

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This perspective view includes the city of Salalah, the second largest city in Oman. The city is located on the broad, generally bright coastal plain and includes areas of green irrigated crops. This view was generated from a Landsat image draped over a preliminary elevation model produced by the Shuttle Radar Topography Mission (SRTM). The edges of the dataset are to the upper right, left, and lower left. The Arabian Sea (lower right) is represented by the blue false-colored area. Vertical exaggeration of topography is 3X.

    This scene illustrates how topography determines local climate and, in turn, where people live. The Arabian Peninsula is very arid. However, the steep escarpment of the Qara Mountains wrings moisture from the summer monsoons allowing for growth of natural vegetation (green along the mountain fronts and in the canyons), and soil development (dark brown areas), as well as cultural development of the coastal plain. The monsoons also provide moisture for Frankincense trees growing on the desert (north) side of the mountains. In ancient times, incense derived from the sap of the Frankincense tree was the basis for an extremely lucrative trade.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot)spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The Landsat 7 Thematic Mapper image used here was provided to the SRTM project by the United States Geological Survey, Earth Resources Observation Systems (EROS) Data Center,Sioux Falls, South Dakota.

    Elevation data used in this image was acquired by SRTM aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar(SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was

  4. 3-D seismology in the Arabian Gulf

    SciTech Connect

    Al-Husseini, M.; Chimblo, R.

    1995-08-01

    Since 1977 when Aramco and GSI (Geophysical Services International) pioneered the first 3-D seismic survey in the Arabian Gulf, under the guidance of Aramco`s Chief Geophysicist John Hoke, 3-D seismology has been effectively used to map many complex subsurface geological phenomena. By the mid-1990s extensive 3-D surveys were acquired in Abu Dhabi, Oman, Qatar and Saudi Arabia. Also in the mid-1990`s Bahrain, Kuwait and Dubai were preparing to record surveys over their fields. On the structural side 3-D has refined seismic maps, focused faults and fractures systems, as well as outlined the distribution of facies, porosity and fluid saturation. In field development, 3D has not only reduced drilling costs significantly, but has also improved the understanding of fluid behavior in the reservoir. In Oman, Petroleum Development Oman (PDO) has now acquired the first Gulf 4-D seismic survey (time-lapse 3D survey) over the Yibal Field. The 4-D survey will allow PDO to directly monitor water encroachment in the highly-faulted Cretaceous Shu`aiba reservoir. In exploration, 3-D seismology has resolved complex prospects with structural and stratigraphic complications and reduced the risk in the selection of drilling locations. The many case studies from Saudi Arabia, Oman, Qatar and the United Arab Emirates, which are reviewed in this paper, attest to the effectiveness of 3D seismology in exploration and producing, in clastics and carbonates reservoirs, and in the Mesozoic and Paleozoic.

  5. Monitoring red tide with satellite imagery and numerical models: a case study in the Arabian Gulf.

    PubMed

    Zhao, Jun; Ghedira, Hosni

    2014-02-15

    A red tide event that occurred in August 2008 in the Arabian Gulf was monitored and assessed using satellite observations and numerical models. Satellite observations revealed the bloom extent and evolution from August 2008 to August 2009. Flow patterns of the bloom patch were confirmed by results from a HYCOM model. HYCOM data and satellite-derived sea surface temperature data further suggested that the bloom could have been initiated offshore and advected onshore by bottom Ekman layer. Analysis indicated that nutrient sources supporting the bloom included upwelling, Trichodesmium, and dust deposition while other potential sources of nutrient supply should also be considered. In order to monitor and detect red tide effectively and provide insights into its initiation and maintenance mechanisms, the integration of multiple platforms is required. The case study presented here demonstrated the benefit of combing satellite observations and numerical models for studying red tide outbreaks and dynamics. PMID:24461701

  6. Environmental assessment of coastal surface sediments at Tarut Island, Arabian Gulf (Saudi Arabia).

    PubMed

    Youssef, Mohamed; El-Sorogy, Abdelbaset; Al Kahtany, Khaled; Al Otiaby, Naif

    2015-07-15

    Thirty eight surface sediments samples have been collected in the area around Tarut Island, Saudi Arabian Gulf to determine the spatial distribution of metals, and to assess the magnitude of pollution. Total concentrations of Fe, Mn, As, B, Cd, Co, Cr, Cu, Hg, Mo, Pb, Se, and Zn in the sediments were measured using ICP-MS (Inductively Coupled Plasma-Mass Spectrometer). Nature of sediments and heavy metals distribution reflect marked changes in lithology, biological activities in Tarut bay. Very high arsenic concentrations were reported in all studied locations from Tarut Island. The concentrations of Mercury are generally high comparing to the reported values from the Gulf of Oman, Red Sea. The concentrations of As and Hg exceeded the wet threshold safety values (MEC, PEC) indicating possible As and Hg contamination. Dredging and land filling, sewage, and oil pollution are the most important sources of pollution in the study area. PMID:25963571

  7. Investigating Transition Zone Thickness Variation under the Arabian Plate: Evidence Lacking for Deep Mantle Upwellings

    NASA Astrophysics Data System (ADS)

    Juliá, J.; Tang, Z.; Mai, P. M.; Zahran, H.

    2014-12-01

    Cenozoic volcanic outcrops in Arabia - locally known as harrats - span more than 2000 km along the western half of the Arabian plate, from eastern Yemen to southern Syria. The magmatism is bimodal in character, with older volcanics (30 to 20 My) being tholeiitic-to-transitional and paralleling the Red Sea margin, and younger volcanics (12 Ma to Recent) being transitional-to-strongly-alkalic and aligning in a more north-south direction. The bimodal character has been attributed to a two-stage rifting process along the Red Sea, where the old volcanics would have produced from shallow sources related to an initial passive rifting stage, and young volcanics would have originated from one or more deep-seated mantle plumes driving present active rifting. Early models suggested the harrats would have resulted from either lateral flow from the Afar plume in Ethiopia, or more locally from a separate mantle plume directly located under the shield. Most recently, tomographic images of the Arabian mantle have suggested the northern harrats could be resulting from flow originating at a deep plume under Jordan. In this work, we investigate the location of deep mantle plumes under the Arabian plate by mapping transition zone thickness with teleseismic receiver functions. The transition zone is bounded by seismic discontinuities, nominally at 410 and 660 km depth, originating from phase transitions in the olivine-normative component of the mantle. The precise depth of the discontinuities is strongly dependent on temperature and, due to the opposing signs of the corresponding Clapeyron slopes, positive temperature anomalies are expected to result in thinning of the transition zone. Our dataset consists of ~5000 low-frequency (fc < 0.25 Hz) receiver function waveforms obtained at ~110 broadband stations belonging to a number of permanent and temporary seismic networks in the region. The receiver functions were migrated to depth and stacked along a ~2000 km long record section

  8. Shear wave velocity structures of the Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Mokhtar, Talal A.; Al-Saeed, Mohammed M.

    1994-02-01

    The shear velocity structures of the different tectonic provinces of the Arabian Peninsula has been studied using surface wave data recorded by the RYD (Riyadh) station. The inversion of Rayleigh wave group velocities indicates that the Arabian shield can be modeled by two layers, each of which is 20 km thick with a shear velocity of 3.61 km/s in the upper crust and 3.88 km/s in the lower crust. The underlying upper mantle velocity is 4.61 km/s. Inversion of both Love and Rayleigh waves group velocities shows that the Arabian platform upper and lower crusts are comparable in their thicknesses to those of the shield, but with shear velocities of 3.4 and 4 km/s, respectively. The upper mantle velocity beneath the platform is 4.4 km/s and the average total thickness of the crust is 45 km.

  9. Change Detection Analysis of Costal Habitat Using Remote Sensing Technologies in the Western Arabian Gulf (Saudi Arabian Coast) over a Thirty-Year Period.

    NASA Astrophysics Data System (ADS)

    El-Askary, H. M.; Idris, N.; Johnson, S. H.; Qurban, M. A. B.

    2014-12-01

    Many factors can severely affect the growth and abundance of the marine ecosystems. For example, due to anthropogenic and natural forces, benthic habitats including but not limited to mangroves, sea grass, salt marshes, macro algae, and coral reefs have been experiencing high levels of declination. Furthermore, aerosols and their propellants are suspected contributors to marine habitat degradation. Although several studies reveal that the Arabian Gulf habitats have suffered deleterious impacts after the Gulf War and the following six month off-shore oil spill, limited research exists to track the changes in benthic habitats over the past three decades using remote sensing. Document changes in costal habitats over the past thirty years were better observed with the use of multispectral remote sensors such as Landsat-5, Landsat-7, and Landsat8 (OLI). Change detection analysis was performed on the three Landsat images (Landsat-5 for the 1987 image, Landsat-7 for the 2000, and Landsat-8 for the 2013 image). The images were then modified, masked off from open water and land. An unsupervised classification was performed which cluster similar classes together. The supervised classification displayed the seven following classes: coral reefs, macro algae, sea grass, salt marshes, mangroves, water, and land. Compared to 1987 image to 2000 scene, there was a noticeable increase in the extensiveness of salt marsh and macro algae habitats. However, a significant decrease in salt marsh habitats were apparent in the 2013 scene.

  10. Skin lipids from Saudi Arabian birds.

    PubMed

    Khan, Haseeb A; Arif, Ibrahim A; Williams, Joseph B; Champagne, Alex M; Shobrak, Mohammad

    2014-04-01

    Skin lipids play an important role in the regulation of cutaneous water loss (CWL). Earlier studies have shown that Saudi desert birds exhibit a tendency of reduced CWL than birds from temperate environment due to adaptive changes in composition of their skin lipids. In this study, we used thin-layer chromatography (TLC) for separation and detection of non-polar and polar lipids from the skin of six bird species including sooty gull, brown booby, house sparrow, Arabian waxbill, sand partridge, and laughing dove. The lipids were separated and detected on Silica gel G coated TLC plates and quantified by using densitometric image analysis. Rf values of the non-polar lipids were as follows: cholesterol (0.29), free fatty acids (0.58), triacylglycerol (0.69), fatty acids methyl esters (0.84) and cholesterol ester (0.97). Rf values for the polar lipids were: cerebroside (0.42), ceramide (0.55) and cholesterol (0.73). The results showed the abundance of fatty acids methyl esters (47.75-60.46%) followed by triacylglycerol (12.69-24.14%). The remaining lipid compositions were as follows: cholesterol (4.09-13.18%), ceramide (2.18-13.27%), and cerebroside (2.53-12.81%). In conclusion, our findings showed that TLC is a simple and sensitive method for the separation and quantification of skin lipids. We also reported a new protocol for lipid extraction using the zirconia beads for efficient disruption of skin tissues. This study will help us better understand the role of skin lipids in adaptive physiology towards adverse climatic conditions. PMID:24600311

  11. Skin lipids from Saudi Arabian birds

    PubMed Central

    Khan, Haseeb A.; Arif, Ibrahim A.; Williams, Joseph B.; Champagne, Alex M.; Shobrak, Mohammad

    2013-01-01

    Skin lipids play an important role in the regulation of cutaneous water loss (CWL). Earlier studies have shown that Saudi desert birds exhibit a tendency of reduced CWL than birds from temperate environment due to adaptive changes in composition of their skin lipids. In this study, we used thin-layer chromatography (TLC) for separation and detection of non-polar and polar lipids from the skin of six bird species including sooty gull, brown booby, house sparrow, Arabian waxbill, sand partridge, and laughing dove. The lipids were separated and detected on Silica gel G coated TLC plates and quantified by using densitometric image analysis. Rf values of the non-polar lipids were as follows: cholesterol (0.29), free fatty acids (0.58), triacylglycerol (0.69), fatty acids methyl esters (0.84) and cholesterol ester (0.97). Rf values for the polar lipids were: cerebroside (0.42), ceramide (0.55) and cholesterol (0.73). The results showed the abundance of fatty acids methyl esters (47.75–60.46%) followed by triacylglycerol (12.69–24.14%). The remaining lipid compositions were as follows: cholesterol (4.09–13.18%), ceramide (2.18–13.27%), and cerebroside (2.53–12.81%). In conclusion, our findings showed that TLC is a simple and sensitive method for the separation and quantification of skin lipids. We also reported a new protocol for lipid extraction using the zirconia beads for efficient disruption of skin tissues. This study will help us better understand the role of skin lipids in adaptive physiology towards adverse climatic conditions. PMID:24600311

  12. The Tetramorium squaminode species group (Hymenoptera, Formicidae) in the Arabian Peninsula, with a new record from the Kingdom of Saudi Arabia and keys to Arabian species

    PubMed Central

    Sharaf, Mostafa R.; Al Dhafer, Hathal M.; Aldawood, Abdulrahman S.

    2015-01-01

    Abstract The Arabian species of the Tetramorium squaminode-group are treated. Tetramorium squaminode Santschi, 1911 is recorded for the first time from the Kingdom of Saudi Arabia and the Arabian Peninsula. Keys to the two Arabian species of the Tetramorium squaminode-group, Tetramorium latinode Collingwood & Agosti, 1996 and Tetramorium squaminode, based on worker and queen castes, are given and a regional distribution map is provided. Notes on habitats of Tetramorium squaminode are presented. PMID:26019665

  13. On Selected Morphemes in Saudi Arabian Sign Language

    ERIC Educational Resources Information Center

    Morris, Carla; Schneider, Erin

    2012-01-01

    Following a year of study of Saudi Arabian Sign Language (SASL), we are documenting our findings to provide a grammatical sketch of the language. This paper represents one part of that endeavor and focuses on a description of selected morphemes, both manual and non-manual, that have appeared in the course of data collection. While some of the…

  14. "Going Mobile" in Business Communication at an Arabian Gulf University

    ERIC Educational Resources Information Center

    Rapanta, Chrysi; Nickerson, Catherine; Goby, Valerie Priscilla

    2014-01-01

    In this article, we describe a project in which undergraduate business seniors at a university in the Arabian Gulf created or evaluated the chapters of an iBook as part of their final course in business communication. Students were surveyed throughout the project, and they also participated in a focus group discussion at the end. The aim was to…

  15. Selected Lexical Patterns in Saudi Arabian Sign Language

    ERIC Educational Resources Information Center

    Young, Lesa; Palmer, Jeffrey Levi; Reynolds, Wanette

    2012-01-01

    This combined paper will focus on the description of two selected lexical patterns in Saudi Arabian Sign Language (SASL): metaphor and metonymy in emotion-related signs (Young) and lexicalization patterns of objects and their derivational roots (Palmer and Reynolds). The over-arcing methodology used by both studies is detailed in Stephen and…

  16. Academic Integrity and Oral Examination: An Arabian Gulf Perspective

    ERIC Educational Resources Information Center

    Thomas, Justin; Raynor, Monique; McKinnon, Merryn

    2014-01-01

    Academic dishonesty is a major challenge facing educational institutions worldwide. Within the context of undergraduate education in the Arabian Gulf, oral assessment can help validate the originality of student work, whilst simultaneously facilitating assessment in a mode highly resonant with the region's own educational traditions and…

  17. Observations on Word Order in Saudi Arabian Sign Language

    ERIC Educational Resources Information Center

    Sprenger, Kristen; Mathur, Gaurav

    2012-01-01

    This article focuses on the syntactic level of the grammar of Saudi Arabian Sign Language by exploring some word orders that occur in personal narratives in the language. Word order is one of the main ways in which languages indicate the main syntactic roles of subjects, verbs, and objects; others are verbal agreement and nominal case morphology.…

  18. On Selected Phonological Patterns in Saudi Arabian Sign Language

    ERIC Educational Resources Information Center

    Tomita, Nozomi; Kozak, Viola

    2012-01-01

    This paper focuses on two selected phonological patterns that appear unique to Saudi Arabian Sign Language (SASL). For both sections of this paper, the overall methodology is the same as that discussed in Stephen and Mathur (this volume), with some additional modifications tailored to the specific studies discussed here, which will be expanded…

  19. Upper mantle structure under western Saudi Arabia from Rayleigh wave tomography and the origin of Cenozoic uplift and volcanism on the Arabian Shield

    SciTech Connect

    Park, Y; Nyblade, A; Rodgers, A; Al-Amri, A

    2007-11-09

    The shear velocity structure of the shallow upper mantle beneath the Arabian Shield has been modeled by inverting new Rayleigh wave phase velocity measurements between 45 and 140 s together with previously published Rayleigh wave group velocity measurement between 10 and 45 s. For measuring phase velocities, we applied a modified array method that minimizes the distortion of raypaths by lateral heterogeneity. The new shear velocity model shows a broad low velocity region in the lithospheric mantle across the Shield and a low velocity region at depths {ge} 150 km localized along the Red Sea coast and Makkah-Madinah-Nafud (MMN) volcanic line. The velocity reduction in the upper mantle corresponds to a temperature anomaly of {approx}250-330 K. These finding, in particular the region of continuous low velocities along the Red Sea and MMN volcanic line, do not support interpretations for the origin of the Cenozoic plateau uplift and volcanism on the Shield invoking two separate plumes. When combined with images of the 410 and 660 km discontinuities beneath the southern part of the Arabian Shield, body wave tomographic models, a S-wave polarization analysis, and SKS splitting results, our new model supports an interpretation invoking a thermal upwelling of warm mantle rock originating in the lower mantle under Africa that crosses through the transition zone beneath Ethiopia and moves to the north and northwest under the eastern margin of the Red Sea and the Arabian Shield. In this interpretation, the difference in mean elevation between the Platform and Shield can be attributed to isostatic uplift caused by heating of the lithospheric mantle under the Shield, with significantly higher region along the Red Sea possibly resulting from a combination of lithosphere thinning and dynamic uplift.

  20. Major events in the late Precambrian to early Triassic geohistory of the Arabian Peninsula

    SciTech Connect

    Stump, T.E.; Connally, T.C.; Van der Eem, J.G.L.A. )

    1993-09-01

    The late Precambrian to Early Triassic of the Arabian Peninsula occur in five supergroups. Their geohistory resulted from sedimentation along fluvial to midshelf facies tracts, eustatic oscillation and periodic uplift. The first supergroup, Plate Precambrian-Middle Cambrian, includes the Siq/Salib and Yatib formations. Deposited by north-eastward-flowing braided streams, they eroded and buried an Arabian shield topography. The Saq Formation lies in angular unconformity on the Siq which documents early Middle Cambrian uplift. Supergroup two, Middle Cambrian-middle Caradocian, the Burj and Saq formations, the Hanadir, Kahfah, and Ra'an members, Qasim Formation, were deposited on a stable continental margin in fluvio-deltaic to midshelf settings. Coastal onlap occurred in the Middle Cambrian, early Llanvirn, middle Llandeilo and early Caradoc. Middle Caradocian uplift deeply eroded parts of central and southern Arabia. Supergroup three of middle Caradocian-early Llandoverian are the Quwarah Member, Qasim Formation and the Zarqa/Sarah formations. They were deposited in a fluvio-deltaic shallow shelf. Late Ashgill uplift, combined with glacially induced sea level lowering, incised valleys up to 2000 ft (610 m) deep. Supergroup four, early Llandovery-Middle Carboniferous, includes the Qalibah, Tawil, Jauf, Jubah and Berwath formations. They were deposited in a fluvio-deltaic marine, river dominated system. The Quysaiba and Sharawra members, Qalibah Formation, were the offshore clays and prodelta sands, the Tawil-Jubah were the fluvial to delta front, and the Berwath the delta plain facies. Deep pre-Tawil erosion documents late Silurian-Early Devonian uplift. The fifth supergroup are the Juwayl, Unayzah, Khuff and Sudair formations. The first two units were deposited in a glacio-fluvial system which eroded and infilled a Hercynian topography. The Khuff transgression occurred during the Artinsklan-Tartarian and the Early Triassic regressive Sudair documents renewed uplift.

  1. Early cretaceous platform-margin configuration and evolution in the central Oman mountains, Arabian peninsula

    SciTech Connect

    Pratt, B.R. ); Smewing, J.D. )

    1993-02-01

    The Hajar Supergroup (Middle Permian-Lower Cretaceous) of northeastern Oman records rifting and development of a passive margin along the edge of the Arabian platform facing Neo-Tethys. The Jurassic and Lower Cretaceous part, comprising the Sahtan, Kahmah, and Wasia groups, was deposited during the maximum extent of the broad epicontinental sea landward of this margin. These limestone units reach a total of 1500 m in thickness and correlate with the hydrocarbon reservoirs of the Arabian Peninsula. The trace of the Jurassic and Cretaceous margin in northeastern Oman followed a zigzag series of rift segments, resulting in promontories and reentrants that changed in position through time in response to the configuration and differential motion of underlying rift blocks. Synsedimentary normal faulting occurred locally in the Middle Jurassic, whereas in the Late Jurassic, the margin was eroded from variable uplift of up to 300 m before subsiding to below storm wave base. This uplift may have been caused by compression from oceanic crust that obducted along the southeastern side of the platform. The Lower Cretaceous succession in the central Oman Mountains and adjacent subsurface began with regional drowning around the Jurassic-Cretaceous boundary. The succession in the east (Saih Hatat) records a single regressive sequence, ending in the progradation of the shallow-water carbonate platform by the Cenomanian. However, the succession in the west (Jebel Akhdar and interior) is dominated by shallow-water carbonate facies, but punctuated by a second regional drowning in the late Aptian. A third, Late Cretaceous drowning terminated deposition of the Wasia Group in the Turonian and was caused by convergence of oceanic crust and foreland basic formation. The record of tectonic behavior of carbonate platforms has important implications for the development of hydrocarbon source rocks and porosity. 68 refs., 11 figs., 1 tab.

  2. Differential GPS measurements as a tool to quantify Late Cenozoic crustal deformation (Oman, Arabian Peninsula)

    NASA Astrophysics Data System (ADS)

    Rupprechter, M.; Roepert, A.; Hoffmann, G.

    2012-04-01

    The Sultanate of Oman is situated in the north-eastern part of the Arabian Plate. It therefore represents the leading edge as the plate is drifting north relative to the Eurasian Plate. The movement results in continent-continent collision in the northwest (Zagros fold and thrust belt) and ocean-continent collision in the northeast (Makran subduction zone). We follow the hypothesis that this plate tectonic setting results in an internal deformation of the Arabian Plate. The study presented here is part of a larger project that aims at quantifying the forcing factors of coastal evolution (Hoffmann et al. 2012). The sea level development, climate - and associated rates of weathering and sediment supply - and differential land movement (neotectonics) are identified as key factors during the Late Cenozoic. Recent vertical land movement is obvious and expressed in differences of the coastal morphology. Parts of the coastline are subsiding: these areas show drowned wadi mouths. Other parts are characterised by a straightened coastline and raised wave-cut terraces are evident well above present mean sea-level. Despite these erosional terraces, depositional terraces on alluvial fans are also encountered in close vicinity to the mountain chain. Detailed topographic profile measurements are carried out using a LEICA Viva GNSS-GS15 differential GPS. The instrument yields data with an accuracy of 1-2 cm relatively to the base station. The profile measurements are orientated perpendicular to the coastline and therefore perpendicular to the raised wave-cut terraces. Up to 6 terraces are encountered in elevations up to 400 m above present sea level with the older ones being the highest. The data allow calculating the scarp height, tread length and tread angle of the terraces. The results indicate that the terraces show an increased seaward tilting with age. This observation is interpreted as reflecting ongoing uplift. A coast-parallel deformation pattern becomes obvious when

  3. Low Arabian dust extinction-to-backscatter ratio

    NASA Astrophysics Data System (ADS)

    Mamouri, R. E.; Ansmann, A.; Nisantzi, A.; Kokkalis, P.; Schwarz, A.; Hadjimitsis, D.

    2013-09-01

    Compared to typical values of 50-60 sr of the extinction-to-backscatter ratio (lidar ratio) at 532 nm of western Saharan mineral dust, low dust lidar ratios from 33.7±6.7 to 39.1±5.1 sr were derived from polarization lidar observations at Limassol, Cyprus (34°N, 33°E) during an outbreak of Arabian dust mainly from Syria in September 2011, indicated by particle linear depolarization ratios up to 28%-35%. The applied new polarization-lidar/photometer method for the extraction of the dust-related lidar-ratio information from the lidar data is outlined, and the results of the dust outbreak which lasted over several days are discussed. The results confirm an Aerosol Robotic Network photometer study on Arabian dust lidar ratios.

  4. Polynuclear aromatic hydrocarbons (PAHs) in fish from the Arabian Gulf

    SciTech Connect

    DouAbdul, A.A.Z.; Abaychi, J.K.; Al-Edanee, T.E.; Ghani, A.A.; Al-Saad, H.T.

    1987-03-01

    Emphasis has been placed upon the identification and qualification of compounds with potential adverse health effects on humans. Prominent among this group are polynuclear aromatic hydrocarbons (PAHs), several of which are known or suspected carcinogens. PAHs enter the marine environment from a variety of sources including petroleum pollution, industrial and domestic effluents, atmospheric particles, and biosynthesis by plants and microorganisms. Although one-third of the world's oil is produced around the Arabian Gulf, no detailed analysis have been conducted to determine PAHs in this region. Nevertheless, numerous investigations have shown the ability of marine organisms including fish to accumulation PAHs from solution or dispersion in seawater. When fish are harvested, a human health hazard may result. In the present communication, high performance liquid chromatography (HPLC) was used to identify and measure sixteen PAHs priority pollutants issued by US Environmental Protection Agency (EPA) in fourteen species of commercially significant fish from the NW Arabian Gulf.

  5. Microsatellite analysis of genetic diversity and population structure of Arabian horse populations.

    PubMed

    Khanshour, Anas; Conant, Eleanore; Juras, Rytis; Cothran, Ernest Gus

    2013-01-01

    The Arabian horse ignites imagination throughout the world. Populations of this breed exist in many countries, and recent genetic work has examined the diversity and ancestry of a few of these populations in isolation. Here, we explore 7 different populations of Arabians represented by 682 horses. Three of these are Middle Eastern populations from near the historical origin of the breed, including Syrian, Persian, and Saudi Arabian. The remaining Western populations are found in Europe (the Shagya Arabian and Polish Arabian) and in America (American Arabian). Analysis of genetic structure was carried out using 15 microsatellite loci. Genetic distances, analysis of molecular variance, factorial correspondence analysis, and a Bayesian method were applied. The results consistently show higher level of diversity within the Middle Eastern populations than the Western populations. The Western Arabian populations were the main source among population variation. Genetic differentiation was not strong among all Middle Eastern populations, but all American Arabians showed differentiation from Middle Eastern populations and were somewhat uniform among themselves. Here, we explore the diversities of many different populations of Arabian horses and find that populations not from the Middle East have noticeably lower levels of diversity, which may adversely affect the health of these populations. PMID:23450090

  6. Guidelines to classification and nomenclature of Arabian felsic plutonic rocks

    USGS Publications Warehouse

    Ramsay, C.R.; Stoeser, D.B.; Drysdall, A.R.

    1986-01-01

    Well-defined procedures for classifying the felsic plutonic rocks of the Arabian Shield on the basis of petrographic, chemical and lithostratigraphic criteria and mineral-resource potential have been adopted and developed in the Saudi Arabian Deputy Ministry for Mineral Resources over the past decade. A number of problems with conventional classification schemes have been identified and resolved; others, notably those arising from difficulties in identifying precise mineral compositions, continue to present difficulties. The petrographic nomenclature used is essentially that recommended by the International Union of Geological Sciences. Problems that have arisen include the definition of: (1) rocks with sodic, zoned or perthitic feldspar, (2) trondhjemites, and (3) alkali granites. Chemical classification has been largely based on relative molar amounts of alumina, lime and alkalis, and the use of conventional variation diagrams, but pilot studies utilizing univariate and multivariate statistical techniques have been made. The classification used in Saudi Arabia for stratigraphic purposes is a hierarchy of formation-rank units, suites and super-suites as defined in the Saudi Arabian stratigraphic code. For genetic and petrological studies, a grouping as 'associations' of similar and genetically related lithologies is commonly used. In order to indicate mineral-resource potential, the felsic plutons are classed as common, precursor, specialized or mineralized, in order of increasing exploration significance. ?? 1986.

  7. Multiscale Local Forcing of the Arabian Desert Daytime Boundary Layer, and Implications for the Dispersion of Surface-Released Contaminants.

    NASA Astrophysics Data System (ADS)

    Warner, Thomas T.; Sheu, Rong-Shyang

    2000-05-01

    Four 6-day simulations of the atmospheric conditions over the Arabian Desert during the time of the 1991 detonation and release of toxic material at the Khamisiyah, Iraq, weapons depot were performed using a mesoscale model run in a data-assimilation mode. These atmospheric simulations are being employed in a forensic analysis of the potential contribution of the toxic material to so-called Gulf War illness. The transport and concentration of such surface-released contaminants are related strongly to the planetary boundary layer (PBL) depth and the horizontal wind speed in the PBL. The product of the PBL depth and the mean wind speed within it is referred to as the ventilation and is used as a metric of the horizontal transport within the PBL. Thus, a corollary study to the larger forensic analysis involves employing the model solutions and available data in an analysis of the multiscale spatial variability of the daytime desert PBL depth and ventilation as they are affected by surface forcing from terrain elevation variations, coastal circulations, and contrasts in surface physical properties.The coarsest computational grid spanned the entire northern Arabian Desert and surrounding areas of the Middle East, and represented the large-scale PBL modulation by the orography. The PBL depths were greatest over the high elevations of the western Arabian Peninsula and over the Zagros Mountains in western Iran and were shallowest over water bodies and the lower elevations in the Tigris-Euphrates Valley. Higher-resolution grids in the nest (the smallest grid increment was 3.3 km) showed that the PBL depth minimum in the Tigris-Euphrates Valley was likely a consequence of compensating subsidence associated with the thermally forced daytime upward motion over the Zagros Mountains to the east in Iran, with possible contributions from an elevated mixed layer. Further local modulation of the daytime desert PBL occurred as a result of the inland penetration of the coastal sea

  8. Estimation of Dust Emission from the Western Coastal Plains of Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Anisimov, Anatolii; Stenchikov, Georgiy

    2016-04-01

    This study is aimed at quantifying local-scale dust emission from the coastal areas of western Arabian Peninsula. The dust emitted from these areas is frequently deposited directly to the Red Sea, acting as an important component of the nutrient balance of marine ecosystems. Most chemicals including iron, phosphorus, and nitrogen are introduced to the Red Sea with airborne dust. This process is especially significant for the oligotrophic northern Red Sea, where nutrients from the Indian Ocean cannot reach and the nutrient supply from land river discharge is negligible. The dust deposition to the Red Sea associated with major dust storms was recently estimated to be about 6 Tg/yr, but this estimate does not account for local, small-scale dust outbreaks occurring during fair weather conditions or moderate winds. The seasonality and the magnitude of this nutrient supply are largely unknown. In the present study, we quantify dust emissions using the fine-scale off-line version-4 of the Community Land Model (CLM4) with the high-resolution datasets as input parameters. We examine the model sensitivity to the spatial resolution of input land cover and vegetation data, and compare the results with weather station observations and reanalysis to choose the best model configuration. The model results are shown to be in reasonable agreement with station visibility measurements and the frequency of dust event reports. To improve the spatial characteristics of dust emission, we apply two state-of-the-art dust source functions. We found that the source function based on measurements from SEVIRI satellite substantially improves the simulation results, being in good agreement with both reanalysis data and station measurements. We identify the major dust source hot-spot areas over the coastal plain and analyze the seasonal and diurnal variability of dust emissions. The annual dust generation from the 145000 km2 coastal area reaches 6 Tg/yr. Roughly half of emitted dust could be

  9. Assessment of heavy metal contamination in intertidal gastropod and bivalve shells from central Arabian Gulf coastline, Saudi Arabia

    NASA Astrophysics Data System (ADS)

    El-Sorogy, Abdelbaset S.; Youssef, Mohamed

    2015-11-01

    In order to assess pollutants and impact of environmental changes along the Saudi Arabian Gulf coast, forty specimens of gastropod and bivalve shells belonging to Diodora funiculata, Lunella coronata, Cerithium caeruleum, Barbatia parva, Pinctada margaritifera, Amiantis umbonella, Acrosterigma assimile and Asaphis violascens from five localities are selected for Fe, Cu, Pb, Mn, Cd, Se, As, Co, B, Cr, Hg, Mo analysis. The analysis indicated that heavy metal values (except Fe) were less than those recorded in molluscan shells from Gulf of Oman, Red Sea and Indian Ocean. D. funiculate, L. coronata, B. parva and P. margaritifera are good accumulators of Cu, As, Cr. The other species gave a nearly constant concentration in all the studied areas. Al Jubail coast recorded the highest heavy metal concentrations (except Mn at Ras Al-Ghar and Se at Al Jubail industrial city). Heavy metal contamination is mostly attributed to anthropogenic sources, especially effluents from petrochemical industries, sewage and desalination plants.

  10. The Dead Sea

    NASA Technical Reports Server (NTRS)

    2006-01-01

    The Dead Sea is the lowest point on Earth at 418 meters below sea level, and also one of the saltiest bodies of water on Earth with a salinity of about 300 parts-per-thousand (nine times greater than ocean salinity). It is located on the border between Jordan and Israel, and is fed by the Jordan River. The Dead Sea is located in the Dead Sea Rift, formed as a result of the Arabian tectonic plate moving northward away from the African Plate. The mineral content of the Dead Sea is significantly different from that of ocean water, consisting of approximately 53% magnesium chloride, 37% potassium chloride and 8% sodium chloride. In the early part of the 20th century, the Dead Sea began to attract interest from chemists who deduced that the Sea was a natural deposit of potash and bromine. From the Dead Sea brine, Israel and Jordan produce 3.8 million tons potash, 200,000 tons elemental bromine, 45,000 tons caustic soda, 25, 000 tons magnesium metal, and sodium chloride. Both countries use extensive salt evaporation pans that have essentially diked the entire southern end of the Dead Sea.

    With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet.

    ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

    The broad spectral coverage and high spectral resolution of ASTER provides scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop

  11. Three new species of Pararhabdepyris Gorbatovsky (Hymenoptera, Bethylidae) from Central Africa and the Arabian Peninsula.

    PubMed

    Vargas, Juan M; Azevedo, Celso O

    2016-01-01

    Three new species of Pararhabdepyris are described and illustrated: P. arabo sp. nov. (United Arabian Emirates and Yemen), P. wafrika sp. nov. (Central African Republic), P. ngangu sp. nov. (Central African Republic). The genus is recorded for the first time from the Saharo-Arabian region. A key for all species of the genus is presented. PMID:27395185

  12. Examining the Experiences and Adjustment Challenges of Saudi Arabian Students in the California State University System

    ERIC Educational Resources Information Center

    Caldwell, Jeremy Dean

    2013-01-01

    The purpose of this study was to examine the experiences and adjustment challenges of Saudi Arabian students in the California State University (CSU) system. Specifically, the study was conducted to better understand and serve the Saudi Arabian students studying in the system. The design for this mixed method study integrated both quantitative and…

  13. Regional joint sets in the Arabian platform as indicators of intraplate processes

    SciTech Connect

    Hancock, P.L.; Sha'At, N.A.; Al Kadhi, A.

    1984-02-01

    The eastern part of the Saudi Arabian craton is a platform underlain by gently tilted and horizontal Mesozoic-Cenozoic sedimentary rocks. The platform contains several laterally extensive, but subdued, structures and lineaments. New microtectonic observations of dominant sets of extension and conjugate hybrid joints permit regionally significant extension directions to be inferred and the origin of the macrostructures to be assessed. The central Arabian arch developed during the Late Cretaceous to Eocene when the basin inverted as a consequence of the emplacement of ophiolite-bearing nappes on the Zagros and Oman margins. During arching, there was strike-parallel elongation of beds. At the same time as the arch amplified, the central Arabian graben system evolved as a result of the northward displacement of an East Arabian block. An important Neogene response in the Arabian platform to northeast-southwest shortening in the Zagros ranges was the formation of a swarm of northeast-striking master joints and lineaments. 41 references.

  14. Bottom Pressure Variability in the Red Sea

    NASA Astrophysics Data System (ADS)

    Limeburner, R.; Abualnaja, Y.; Beardsley, R.

    2012-04-01

    We deployed an array of three bottom pressure/temperature/conductivity (PTC) instruments at Jeddah, Thuwal and Rabigh along the Saudi Arabian coast of the eastern Red Sea for a period of 3 years. This PTC array accurately measured the regional tidal variability of the bottom pressure field and characterized the low frequency along-shore pressure, temperature and salinity gradients and their variability. Surface sea level/height was calculated from the bottom pressure measurements using the hydrostatic equation. On time scales of order 1 day the most energetic component of sea level variability was the semidiurnal and diurnal tides dominated by the M2, N2, K1 and O1 tidal constituents. On time scales of order 10 days the sea level variability was wind driven with setup and set down up to 40 cm due to the local wind stress. On yearly time scales the sea level varied approximately 50 cm and was highest in winter (January-February) and lowest in summer (July-August). Barometric pressure also had an annual cycle of approximately 10 mb and was highest in January thus attenuating the amplitude of the annual sea level variability. Higher sea level in winter months may be due to a convergence in the large-scale Red Sea wind stress. The amplitude of the principal tidal and subtidal sea level variability was coherent at the three sites, but the direction of phase propagation could not be resolved with confidence.

  15. Geodynamic and Magmatic Evolution of the Eastern Anatolian-Arabian Collision Zone, Turkey

    NASA Astrophysics Data System (ADS)

    Keskin, Mehmet

    2014-05-01

    The Eastern Anatolian-Arabian Collision Zone represents a crucial site within the Tethyan domain where a subduction system involving a volcanic arc (i.e. Cretaceous to Oligocene Pontide volcanic arc in the north) associated with a large subduction-accretion complex (i.e. Cretaceous to Oligocene Eastern Anatolian Accretionary Complex i.e. "EAAC" in the south) turned later into a major continental collision zone that experienced a series of geodynamic events including lithospheric delamination, slab-steepening & breakoff, regional domal uplift, widespread volcanism and tectonic escape via strike slip fault systems. The region includes some of the largest volcanic centers (e.g. Karacadaǧ, Aǧırkaya caldera, Ararat, Nemrut, Tendürek and Süphan volcanoes) and plateaus (e.g. The Erzurum-Kars Plateau) as well as the largest transform fault zones in the Mediterranean region. A recent geodynamic modeling study (Faccenna et al., 2013) has suggested that both the closure of the Tethys Ocean and the resultant collision were driven by a large scale and northerly directed asthenospheric mantle flow named the "Tethyan convection cell". This convection cell initiated around 25 Ma by combined effects of mantle upwelling of the Afar super plume located in the south, around 3,000 km away from the collision zone and the slab-pull of the Tethyan oceanic lithosphere beneath Anatolia in the north. The aforementioned mantle flow dragged Arabia to the north towards Eastern Anatolia with an average velocity of 2 cm/y for the last 20 My, twice as fast as the convergence of the African continent (i.e. 1 cm/y) with western and Central Turkey. This 1 cm/y difference resulted in the formation of the left lateral Dead Sea Strike Slip Fault between the African and Arabian plates. Not only did this mantle flow result in the formation of a positive dynamic topography in the west of Arabian block, but also created a dynamic tilting toward the Persian Gulf (Faccenna et al., 2013). Another

  16. Seismic reflection structure of intracratonic palmyride fold-thrust belt and surrounding Arabian platform, Syria

    SciTech Connect

    McBride, J.H.; Barazangi, M.; Best, J. ); Al-Saad, D.; Sawaf, T.; Al-Otri, M.; Gebran, A. )

    1990-03-01

    Seismic reflection and drill-hole data from central Syria provide a detailed view of the subsurface structure (10-15 km depth) of the relatively little-studied intracratonic Palmyride fold and thrust belt. The data set, together with surface geologic mapping, constrains a structural/stratigraphic section spanning the northeast sector of the belt and the surrounding subprovinces of the Arabian platform. The seismic reflection and drill-hole data show Mesozoic stratigraphic sequences thickening abruptly into the Palmyrides from the adjacent, arched Paleozoic platforms Neogene (alpine) folding and thrusting of the Mesozoic basin, as documented on the seismic data, are sharply restricted to the narrow width of the belt ({approximately}100 km), in contrast to the relatively undeformed Phanerozoic strata of the platforms to the north and south. The seismic and drill-hole data support the hypothesis that the palmyrides began as a Permian-Triassic failed rift connected to the Levantine passive continental margin, which was inverted and complexly deformed by the interfering effects of Cenozoic movements along the Dead Sea transform fault system and the Turkish Bitlis convergent zone. The seismic data provide a first view into the extent and depth of the early basin formation and subsequent compressional deformation, and as such represent a necessary element for constraining reconstructions of northern Middle East plate motions. 20 figs.

  17. Geology and hydrocarbon potential in the state of Qatar, Arabian Gulf

    SciTech Connect

    Alsharhan, A.S. ); Nairn, A.E.M. )

    1990-05-01

    The state of Qatar is situated in the southern Arabian Gulf and covers an area of 12,000 km{sup 2}. It is formed by a large, broad anticline, which is part of the regional south-southwest-north-northeast-trending Qatar-South Fars arch. The arch separates the two Infracambrian salt basins. The Dukhan field was the first discovery, made in 1939, in the Upper Jurassic limestones. Since then, a series of discoveries have been made so that Qatar has become one of the leading OPEC oil states. Hydrocarbon accumulations are widely dispersed throughout the stratigraphic column from upper Paleozoic to Cretaceous producing strata. The most prolific reservoirs are the Permian and Mesozoic shelf carbonate sequences. Minor clastic reservoirs occur in the Albian and Paleozoic sequences. Seals, mainly anhydrite and shale. occur both intraformationally and regionally. Several stratigraphic intervals contain source rocks or potential source rocks. The Silurian shales arc the most likely source of the hydrocarbon stored in the upper Paleozoic clastics and carbonates. The upper Oxfordian-middle Kimmeridgian rocks formed in the extensive starved basin during the Mesozoic period of sea level rise. Total organic carbon ranges between 1 and 6%, with the sulfur content approximately 9%. The source material consists of sapropelic liptodetrinite and algae. The geological background of the sedimentary facies through geologic time, stratigraphy, and structural evolution which control source, and the subsequent timing and migration of large-scale hydrocarbon generation are presented in detail.

  18. The Arabian Cradle: Mitochondrial Relicts of the First Steps along the Southern Route out of Africa

    PubMed Central

    Fernandes, Verónica; Alshamali, Farida; Alves, Marco; Costa, Marta D.; Pereira, Joana B.; Silva, Nuno M.; Cherni, Lotfi; Harich, Nourdin; Cerny, Viktor; Soares, Pedro; Richards, Martin B.; Pereira, Luísa

    2012-01-01

    A major unanswered question regarding the dispersal of modern humans around the world concerns the geographical site of the first human steps outside of Africa. The “southern coastal route” model predicts that the early stages of the dispersal took place when people crossed the Red Sea to southern Arabia, but genetic evidence has hitherto been tenuous. We have addressed this question by analyzing the three minor west-Eurasian haplogroups, N1, N2, and X. These lineages branch directly from the first non-African founder node, the root of haplogroup N, and coalesce to the time of the first successful movement of modern humans out of Africa, ∼60 thousand years (ka) ago. We sequenced complete mtDNA genomes from 85 Southwest Asian samples carrying these haplogroups and compared them with a database of 300 European examples. The results show that these minor haplogroups have a relict distribution that suggests an ancient ancestry within the Arabian Peninsula, and they most likely spread from the Gulf Oasis region toward the Near East and Europe during the pluvial period 55–24 ka ago. This pattern suggests that Arabia was indeed the first staging post in the spread of modern humans around the world. PMID:22284828

  19. Analysis of the spatio-temporal variability of seawater quality in the southeastern Arabian Gulf.

    PubMed

    Mezhoud, Nahla; Temimi, Marouane; Zhao, Jun; Al Shehhi, Maryam Rashed; Ghedira, Hosni

    2016-05-15

    In this study, seawater quality measurements, including salinity, sea surface temperature (SST), chlorophyll-a (Chl-a), Secchi disk depth (SDD), pH, and dissolved oxygen (DO), were made from June 2013 to November 2014 at 52 stations in the southeastern Arabian Gulf. Significant variability was noticed for all collected parameters. Salinity showed a decreasing trend, and Chl-a, DO, pH, and SDD demonstrated increasing trends from shallow onshore stations to deep offshore ones, which could be attributed to variations of ocean circulation and meteorological conditions from onshore to offshore waters, and the likely effects of desalination plants along the coast. Salinity and temperature were high in summer and low in winter while Chl-a, SDD, pH, and DO indicated an opposite trend. The CTD profiles showed vertically well-mixed structures. Qualitative analysis of phytoplankton showed a high diversity of species without anomalous species found except in Ras Al Khaimah stations where diatoms were the dominating ones. PMID:27012536

  20. Depression, Anxiety and Stress among Saudi Arabian Dermatology Patients

    PubMed Central

    Ahmed, Anwar E.; Al-Dahmash, Abdulaziz M.; Al-Boqami, Qamra T.; Al-Tebainawi, Yazeed F.

    2016-01-01

    Objectives: This study aimed to determine the prevalence of depression, anxiety and stress among Saudi Arabian dermatology patients and to assess associations with sociodemographic and clinical characteristics. Methods: This cross-sectional study was conducted among 300 consecutive dermatology patients visiting King Abdulaziz Medical City in Riyadh, Saudi Arabia, in August 2015. The Arabic version of the Depression, Anxiety and Stress Scale was used to screen for symptoms of depression, anxiety and stress. Quality of life (QOL) was assessed using the Dermatology Life Quality Index. Results: A total of 254 dermatology patients participated in the study (response rate: 84.7%). The prevalence of depression, anxiety and stress was 12.6%, 22.1% and 7.5%, respectively. The presence of at least one of these negative emotional states was noted among 24.4% of the cohort (95% confidence interval: 19.3–30.2%). Depression was significantly higher among subjects who lacked family support (26.5% versus 10.7%; P = 0.006) while anxiety was less common among patients who engaged in physical exercise (14.5% versus 29.4%; P = 0.005). According to the multivariate logistic regression analysis, poor QOL and a lack of family support were significant predictors of a negative emotional state. Conclusion: Almost a quarter of the studied Saudi Arabian dermatology patients were found to suffer from at least one negative emotional state. A lack of family support and poor QOL were the primary factors associated with a negative emotional state. Interventional studies are needed to examine the effects of social and family support on psychological conditions among Saudi Arabian dermatology patients. PMID:27226914

  1. Hydrogeological influences on petroleum accumulations in the Arabian Gulf

    SciTech Connect

    Vizgirda, J.; Burke, L.

    1995-08-01

    The stratigraphic and topographic conditions in the Arabian Gulf are appropriate for the instigation and maintenance of an active hydrodynamic regime. The setting is that of a gentle basin surrounded by topographic highs. The central Arabian highlands to the west-southwest, the Tarus-Zagros mountains to the north, and the Oman mountains to the east rim the structural low occupied by the Gulf. Elevations in these areas reach maximum values of approximately 1000 meters. Paleozoic through Cenozoic strata stretch continuously across the basin, are relatively unfaulted, and outcrop in the topographic highs. Such a setting is propitious for a regional hydrodynamic system with meteoric recharge in the topographic highs and discharge in the middle of the Gulf. The prolific oil and gas accumulations of this region would be subject to influence by these hydrodynamic processes. The existence of such a hydrodynamic regime is documented by a variety of evidence, including potentiometric data, water salinity measurements, and observed tilts in oil-water contacts. Potentiometric data for several Tertiary and Cretaceous units on the Arabian platform, in the Gulf, and in Iraq show a pattern of consistently decreasing potential from topographic highs to lows. Water salinities show a consistent, but inverse, variation with the potentiometric data. Tilted oil-water contacts in Cretaceous and Jurassic reservoirs are observed in several fields of the Gulf region. The direction and magnitude of the observed tilts are consistent with the water potential and salinity data, and suggest that petroleum accumulations are being influenced by a regional hydrodynamic drive. Basin modelling is used to simulate petroleum generation and migration scenarios, and to integrate these histories with the structural evolution of the Gulf. The integrated modelling study illustrates the influence of hydrodynamic processes on the distribution of petroleum accumulations.

  2. Dominant role of winds near Sri Lanka in driving seasonal sea level variations along the west coast of India

    NASA Astrophysics Data System (ADS)

    Suresh, I.; Vialard, J.; Izumo, T.; Lengaigne, M.; Han, W.; McCreary, J.; Muraleedharan, P. M.

    2016-07-01

    The strong seasonal cycle of sea level along the west coast of India (WCI) has important consequences for ecosystem and fisheries, and the Lakshadweep high/low in the southeast Arabian Sea is important for fisheries and the Indian summer monsoon. Previous studies suggested that WCI sea level variability is primarily driven by remote wind forcing from the Bay of Bengal and equatorial Indian Ocean through coastal Kelvin wave propagation. Using a linear ocean model, we demonstrate that wind forcing in a relatively small region around the southern tip of India and east of Sri Lanka contribute to ~60% of this variability. Wind variations from the rest of the Bay and the equator only account respectively for ~20% and ~10%. Sea level signals forced by the "southern tip" winds extend westward into the eastern Arabian Sea through Rossby wave propagation, with more than 50% contribution in the Lakshadweep high/low region.

  3. Insights into Seismic and Volcanic Processes around the Arabian Plate from InSAR Observations

    NASA Astrophysics Data System (ADS)

    Jónsson, Sigurjón; Wang, Teng; Akoglu, Ahmet; Feng, Guangcai; Xu, Wenbin; Harrington, Jonathan; Cavalié, Olivier

    2014-05-01

    We use InSAR observations to study a variety of seismic and volcanic processes at the plate boundary surrounding the Arabian plate. The plate-boundary motion ranges from extension in the Red Sea and Gulf of Aden to the south, to compression in Turkey and Iran to the north, with transform motion to the west and to the east. Many large earthquakes have occurred during the past two decades in the region, some of which we are studying, including the 1995 magnitude 7.2 earthquake in the Gulf of Aqaba, the 2011 magnitude 7.1 Van earthquake in eastern Turkey, the 2012 Ahar earthquake duplet in northwestern Iran, as well as the 2013 magnitude 7.7 Baluchistan (Pakistan) earthquake. These earthquakes took place in tectonic settings ranging from a transtension in the Gulf of Aqaba, to transpression in Baluchistan, to almost pure compression in eastern Turkey. For the Aqaba earthquake we add previously unused InSAR data and use modern data processing methods to improve earlier fault-model estimations. In the case of the Baluchistan earthquake we find surprisingly uniform and simple fault slip along the over 200 km long rupture, with maximum slip of almost 10 m near the surface. In addition, for the Van earthquake we use SAR-image offset tracking in the near-field, as some of the interferograms are almost completely incoherent. By identifying point-like targets within the images, we are able to derive better pixel offsets between SAR sub-images than with standard offset-tracking methods. We use the azimuth- and range offsets to derive the 3D coseismic displacements, which help constraining the geometry and slip of the causative northward-dipping thrust fault. Further west, in the region near the triple junction between the Arabian, Eurasian, and Anatolian plates, we use large-scale InSAR data processing to map the interseismic deformation near the triple junction and find very shallow locking depth of the eastern part of the East Anatolian Fault, indicating limited strain

  4. XY male pseudohermaphroditism in a captive Arabian oryx (Oryx leucoryx).

    PubMed

    Padilla, Luis R; Dutton, Christopher J; Bauman, Joan; Duncan, Mary

    2005-09-01

    A 2-yr-old Arabian oryx (Oryx leucoryx) was presented for evaluation of abnormal genitalia and infantile behavior. The oryx had a penis and a scrotum, but testes were not palpable within the scrotum or inguinal canal. The total serum testosterone for the individual was lower than in age-matched males of the same species. Surgical exploration showed markedly hypoplastic intra-abdominal gonads, which demonstrated both testicular and uterine tissue on histologic examination. After karyotype analysis, the individual was classified as an XY male pseudohermaphrodite. This condition resembles two human intersex syndromes: embryonic testicular regression syndrome and partial gonadal dysgenesis syndrome, which occur in familial lines. PMID:17312771

  5. Purkinje cell apoptosis in arabian horses with cerebellar abiotrophy.

    PubMed

    Blanco, A; Moyano, R; Vivo, J; Flores-Acuña, R; Molina, A; Blanco, C; Monterde, J G

    2006-08-01

    Purkinje cerebellar cells were studied in three Arabian horses aged between 6 and 8 months with clinical disorders in their movements, tremors and ataxia; the occurrence of apoptosis in this cell population was investigated by the (terminal deoxynucleotidyl transferase biotin-dUTP nick-end labelling (TUNEL) method. Both optical and electron microscopical images showed a scant number of Purkinje cells, most of them with morphological features of apoptosis such as condensation of the nucleus and cytoplasm as well as segregation and fragmentation of the nucleus into apoptotic bodies. The TUNEL technique revealed a substantial number (65%) of positive immunoreactive Purkinje cells. PMID:16901270

  6. A Late Jurasssic to Cretaceous sedimentological and chemostratigraphic transect trough the Oman Mountains; from the Arabian Platform into the Hawasina Basin

    NASA Astrophysics Data System (ADS)

    Wohlwend, Stephan; Celestino, Ricardo; Rehakova, Daniela; Weissert, Helmut

    2014-05-01

    The Oman mountains preserve a Late Jurassic to Cretaceous continental margin transect with the Arabian carbonate shelf and the adjacent deep Hawasina Basin which is outcropping in the nappe pile of the Oman Mountains today. The whole nappe pile containing the continental margin transect is today outcropping in the Central Oman Mountains. The sediment successions of the Platform (Kahmah & Wasia Group) and the Hawasina Basin (Sumeini, Hamrat Duru and Kawr Group) provide the opportunity to investigate the response of an eastern Tethyan equatorial ocean system to multiple perturbations of the carbon cycle during the Cretaceous. Shallow water sediments on the Arabian carbonate shelf and continental slope to turbiditic basinal successions are difficult to date with biostratigraphy and sequence stratigraphy. Therefore we complement existing sequence and biostratigraphy with our newly established carbon isotope chemostratigraphy. The Hawasina Basin and also the easternmost Arabian Platform were affected by the Late Jurassic sea level rise, by changes in oceanography and also by regional tectonics. The widespread shift towards a "pelagic Maiolica Limestone Facies" (Lower Sid'r, Nadan Fm, Rayda Fm) documents this transition in oceanography. Chemo- and biostratigraphy serve for correlation of the pelagic facies across the Hawasina Basin. Pelagic to hemipelagic conditions existed until the time of the Valanginian carbon isotope excursion. With the onset of this excursion chert and silicification features in the pelagic sediments disappeared for a while. Coarse turbidites indicate that the Arabian carbonate platform prograded during Valaginian and Hauterivian time more than 300 km towards the northeast. Facies changes towards coarser turbidites complicates the use of chemostratigraphy as a correlation tool. However, chemostratigraphy of the Barremian to Cenomanian combined with existing radiolarian biostratigraphy in the Hamrat Duru Group shows episodes of reduced sedimentation

  7. Arabian killifish (Aphanius dispar) embryos: A model organism for the risk assessment of the Arabian Gulf coastal waters.

    PubMed

    Saeed, Suhur; Al-Naema, Nayla; Butler, Josh D; Febbo, Eric J

    2015-12-01

    Fish embryos are excellent models for studies aimed at understanding toxic mechanisms and indications of possible acute and chronic effects. For the past 3 yr, an Arabian killifish (Aphanius dispar) fish embryo test has been developed in the authors' laboratory as a routine ecotoxicological test that can be used to support risk assessment of potential contaminants in Arabian Gulf coastal waters. Tests were conducted with 3 reference toxicants (3,4-dichloroaniline [DCA], sodium dodecyl sulfate, and zinc sulfate [Zn]) and chlorine, a disinfectant used widely in industrial cooling systems around the Arabian Gulf region. The 50% effect concentration (EC50) for DCA was 0.47 mg/L and 1.89 mg/L for embryos exposed before 6 hpf and after 168 hpf, respectively. Sublethal effects were mainly observed at concentrations above 2.5 mg/L, the effects included severe pericardial edema and tail shortage. The sodium dodecyl sulfate ionic surfactant caused mortality at both early and late stages of embryo development; it caused coagulation, severe deformity, and hemolysis. Both the EC50 and the 50% lethal concentration (LC50) for sodium dodecyl sulfate were 9.37 mg/L. Salinity influenced the toxicity of Zn to killifish embryos: at 40 psu Zn was found not to be toxic, whereas at 20 psu toxicity had increased significantly (p < 0.05). Values of EC50 and LC50 were 2.5 mg/L and 4 mg/L, respectively. Concentrations above 15 mg/L in embryos were often accompanied by upper abdominal edema and inhibition of growth, especially evident in the tail. Chlorine caused mortality at a lower concentration; for example, at 0.05 mg/L 33% of embryos were found dead at the end of the experiment. The LC50 for chlorine was determined to be 0.08 mg/L. Examination of the existing literature showed similar results to the present study's findings. The results suggest a more comparable sensitivity of killifish embryos to that of other fish embryo test recommended species. The present study

  8. Seascape genetics along environmental gradients in the Arabian Peninsula: insights from ddRAD sequencing of anemonefishes.

    PubMed

    Saenz-Agudelo, Pablo; Dibattista, Joseph D; Piatek, Marek J; Gaither, Michelle R; Harrison, Hugo B; Nanninga, Gerrit B; Berumen, Michael L

    2015-12-01

    Understanding the processes that shape patterns of genetic structure across space is a central aim of landscape genetics. However, it remains unclear how geographical features and environmental variables shape gene flow, particularly for marine species in large complex seascapes. Here, we evaluated the genomic composition of the two-band anemonefish Amphiprion bicinctus across its entire geographical range in the Red Sea and Gulf of Aden, as well as its close relative, Amphiprion omanensis endemic to the southern coast of Oman. Both the Red Sea and the Arabian Sea are complex and environmentally heterogeneous marine systems that provide an ideal scenario to address these questions. Our findings confirm the presence of two genetic clusters previously reported for A. bicinctus in the Red Sea. Genetic structure analyses suggest a complex seascape configuration, with evidence of both isolation by distance (IBD) and isolation by environment (IBE). In addition to IBD and IBE, genetic structure among sites was best explained when two barriers to gene flow were also accounted for. One of these coincides with a strong oligotrophic-eutrophic gradient at around 16-20˚N in the Red Sea. The other agrees with a historical bathymetric barrier at the straight of Bab al Mandab. Finally, these data support the presence of interspecific hybrids at an intermediate suture zone at Socotra and indicate complex patterns of genomic admixture in the Gulf of Aden with evidence of introgression between species. Our findings highlight the power of recent genomic approaches to resolve subtle patterns of gene flow in marine seascapes. PMID:26577830

  9. Trace metals in gills of fish from the Arabian Gulf

    SciTech Connect

    Al-Yakoob, S.; Bahloul, M. ); Bou-Olayan, A.H.

    1994-11-01

    Complexation of metals by coordinate linkages with appropriate organic molecules in biological tissues is an important process involved in metal accumulation by aquatic organisms. Fish respiratory systems differ from all other systems because damage to gills has immediate impacts on the rest of the fish's body. Veer et al. observed significant correlation between gill-metal concentration and whole-body weight. More nickel is accumulated in gill tissue of the catfish (Clarias batrachus) than in the liver or intestine. More cadmium is accumulated in gill tissue of the fish Heteropneustes fossilis (Bloch) and Channa punctatus (Bloch) than in the liver or kidney. When exposed to lethal and sublethal concentrations of copper, gills of the freshwater fish Labeo rohita (Hamilton) showed the highest degree of copper accumulation. Petroleum and petrochemical industry wastes contribute significantly to metal enrichment of the Arabian Gulf marine environment. Because accumulation of metal ions is significant in gills, levels of Cd, Cr, Cu, Ni and Pb were investigated in gills of fish from potentially impacted areas along the western side of the Arabian Gulf after the 1991 oil-spill. 15 refs., 3 figs., 1 tab.

  10. Evaluation of the long-term variability of seawater salinity and temperature in response to natural and anthropogenic stressors in the Arabian Gulf.

    PubMed

    Elhakeem, Abubaker; Elshorbagy, Walid

    2013-11-15

    Evaluating the long-term variability of the seawater salinity and temperature due to climate change is a limiting economical and operational factor in planning the design of new and expansion of existing desalination plants. This need is amplified in the Arabian Gulf due to the natural arid climate and anthropological stresses related to energy exploration and ongoing major developments. The lack of data in this region further adds additional dimension to the problem. The present work represents a systematic innovative approach to evaluate the anticipated long-term changes in the seawater salinity and temperature under the stresses of projected climate change and massive industrial effluents using statistical correlation and hydrodynamic simulation. The proposed approach employs the direct relation between the net freshwater losses (evaporation) entrenched with the investigated stressors and the mean sea salinity and sea temperature variation of an inverse estuary to formulate the statistical correlation and the hydrodynamic simulation conditions. PMID:24055462

  11. Style of extensional tectonism during rifting, Red Sea and Gulf of Aden

    USGS Publications Warehouse

    Bohannon, R.G.

    1989-01-01

    Geologic and geophysical studies from the Arabian continental margin in the southern Red Sea and LANDSAT analysis of the northern Somalia margin in the Gulf of Aden suggest that the early continental rifts were long narrow features that formed by extension on closely spaced normal faults above moderate- to shallow-dipping detachments with break-away zones defining one rift flank and root zones under the opposing rift flank. The rift flanks presently form the opposing continental margins across each ocean basin. The detachment on the Arabian margin dips gently to the west, with a breakaway zone now eroded above the deeply dissected terrain of the Arabian escarpment. A model is proposed in which upper crustal breakup occurs on large detachment faults that have a distinct polarity. -from Author

  12. Geodynamic and Magmatic Evolution of the Eastern Anatolian-Arabian Collision Zone, Turkey

    NASA Astrophysics Data System (ADS)

    Keskin, Mehmet

    2014-05-01

    The Eastern Anatolian-Arabian Collision Zone represents a crucial site within the Tethyan domain where a subduction system involving a volcanic arc (i.e. Cretaceous to Oligocene Pontide volcanic arc in the north) associated with a large subduction-accretion complex (i.e. Cretaceous to Oligocene Eastern Anatolian Accretionary Complex i.e. "EAAC" in the south) turned later into a major continental collision zone that experienced a series of geodynamic events including lithospheric delamination, slab-steepening & breakoff, regional domal uplift, widespread volcanism and tectonic escape via strike slip fault systems. The region includes some of the largest volcanic centers (e.g. Karacadaǧ, Aǧırkaya caldera, Ararat, Nemrut, Tendürek and Süphan volcanoes) and plateaus (e.g. The Erzurum-Kars Plateau) as well as the largest transform fault zones in the Mediterranean region. A recent geodynamic modeling study (Faccenna et al., 2013) has suggested that both the closure of the Tethys Ocean and the resultant collision were driven by a large scale and northerly directed asthenospheric mantle flow named the "Tethyan convection cell". This convection cell initiated around 25 Ma by combined effects of mantle upwelling of the Afar super plume located in the south, around 3,000 km away from the collision zone and the slab-pull of the Tethyan oceanic lithosphere beneath Anatolia in the north. The aforementioned mantle flow dragged Arabia to the north towards Eastern Anatolia with an average velocity of 2 cm/y for the last 20 My, twice as fast as the convergence of the African continent (i.e. 1 cm/y) with western and Central Turkey. This 1 cm/y difference resulted in the formation of the left lateral Dead Sea Strike Slip Fault between the African and Arabian plates. Not only did this mantle flow result in the formation of a positive dynamic topography in the west of Arabian block, but also created a dynamic tilting toward the Persian Gulf (Faccenna et al., 2013). Another

  13. Remnants of Miocene fluvial sediments in the Negev Desert, Israel, and the Jordanian Plateau: Evidence for an extensive subsiding basin in the northwestern margins of the Arabian plate

    NASA Astrophysics Data System (ADS)

    Zilberman, Ezra; Calvo, Ran

    2013-06-01

    fluvial sediments, reflecting a subsidence of the northern margins of the African continent (Arabian plate) before its breakup and the splitting of the Sinai-Israel subplate by the Dead Sea Transform. During the early Middle Miocene the subsidence was inversed as the mountainous backbone of Israel was uplifted. The uplift triggered a large scale denudation that removed the thick Early Miocene fluvial sequence from the Negev and transported the eroded sediments northwestward toward the eastern Mediterranean basin. Additional uplift during the late-Middle Miocene was associated with entrenchment of the Be'er Sheva Valley between the Judea Mountains in the north and the Negev Highlands in the south. This valley was flooded by the sea during the Late Miocene. We suggest that the formation of the Early Miocene subsiding basin at the northern edge of the Arabian sub-plate predated the breakup of the Arabian plate by the DST. The inversion of the subsiding regime, which led to the establishment of the Negev Highlands seems to be intimately related to the detachment of the Sinai-Israel sub-plate from the Arabian plate during the Middle Miocene.

  14. Using NASA EOS in the Arabian and Saharan Deserts to Examine Dust Particle Size and Spectral Signature of Aerosols

    NASA Astrophysics Data System (ADS)

    Brenton, J. C.; Keeton, T.; Barrick, B.; Cowart, K.; Cooksey, K.; Florence, V.; Herdy, C.; Luvall, J. C.; Vasquez, S.

    2012-12-01

    Exposure to high concentrations of airborne particulate matter can have adverse effects on the human respiratory system. Ground-based studies conducted in Iraq have revealed the presence of potential human pathogens in airborne dust. According to the Environmental Protection Agency (EPA), airborne particulate matter below 2.5μm (PM2.5) can cause long-term damage to the human respiratory system. Given the relatively high incidence of new-onset respiratory disorders experienced by US service members deployed to Iraq, this research offers a new glimpse into how satellite remote sensing can be applied to questions related to human health. NASA's Earth Observing System (EOS) can be used to determine spectral characteristics of dust particles, the depth of dust plumes, as well as dust particle sizes. Comparing dust particle size from the Sahara and Arabian Deserts gives insight into the composition and atmospheric transport characteristics of dust from each desert. With the use of NASA SeaWiFS DeepBlue Aerosol, dust particle sizes were estimated using Angström exponent. Brightness Temperature Difference (BTD) equation was used to determine the distribution of particle sizes, the area of the dust storm, and whether silicate minerals were present in the dust. The Moderate-resolution Imaging Spectroradiometer (MODIS) on Terra satellite was utilized in calculating BTD. Minimal research has been conducted on the spectral characteristics of airborne dust in the Arabian and Sahara Deserts. Mineral composition of a dust storm that occurred 17 April 2008 near Baghdad was determined using imaging spectrometer data from the Jet Propulsion Laboratory Spectral Library and EO-1 Hyperion data. Mineralogy of this dust storm was subsequently compared to that of a dust storm that occurred over the Bodélé Depression in the Sahara Desert on 7 June 2003.

  15. Neoproterozoic structural evolution of the NE-trending Ad-Damm Shear Zone, Arabian Shield, Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Hamimi, Zakaria; El-Sawy, El-Sawy K.; El-Fakharani, Abdelhamid; Matsah, Mohamed; Shujoon, Abdulrahman; El-Shafei, Mohamed K.

    2014-11-01

    The Ad-Damm Shear Zone (AdSZ) is a major NE- (to NNE-) trending fault zone separating Jiddah and Asir tectonic terranes in the Neoproterozoic Juvenile Arabian Shield (AS). AdSZ is characterized by the development of dextral transcurrent shear-sense indicators and moderately to steeply NW plunging stretching lineations. It is mainly developed under high amphibolite-to greenschist-facies conditions and extends ∼380 km, with an average width ∼2-4 km, from the conspicuous Ruwah Fault Zone in the eastern shield to the Red Sea Coastal plain. It was believed to be one of the conjugate shears of the NW- to NNW-trending sinistral Najd Shear System. This assumption is, based on the noteworthy dextral shear criteria recorded within the 620 Ma mylonitic granite of No'man Complex. A total shear-zone strike length exceeding 117 km is carefully investigated during this study to reconstruct its structural evolution. Shear-sense indicators and other field observations including overprinting relations clearly demonstrate a complicated Neoproterozoic history of AdSZ, involving at least three phases of deformations (D1-D3). Both D1 and D2 phases were of contractional regime. During D1 phase a NW-SE compression led to the formation of NE-oriented low-angle thrusts and tight-overturned folds. D2 is represented by a NE-SW stress oriented that led to the development of an open folding. D3 is expressed by the NE-SW intensive dextral transcurrent brittle-ductile shearing. It is overprinting the early formed fabrics and played a significant role in the creation of AdSZ and the mega-scale related folds. Such deformation history reflects the same Neoproterozoic deformation regime recognized in the NE-trending shear zones in the Arabian-Nubian Shield (ANS).

  16. Decadal stability of Red Sea mangroves

    NASA Astrophysics Data System (ADS)

    Almahasheer, Hanan; Aljowair, Abdulaziz; Duarte, Carlos M.; Irigoien, Xabier

    2016-02-01

    Across the Earth, mangroves play an important role in coastal protection, both as nurseries and carbon sinks. However, due to various human and environmental impacts, the coverage of mangroves is declining on a global scale. The Red Sea is in the northern-most area of the distribution range of mangroves. Little is known about the surface covered by mangroves at this northern limit or about the changes experienced by Red Sea mangroves. We sought to study changes in the coverage of Red Sea mangroves by using multi-temporal Landsat data (1972, 2000 and 2013). Interestingly, our results show that there has been no decline in mangrove stands in the Red Sea but rather a slight increase. The area covered by mangroves is about 69 Km2 along the African shore and 51 Km2 along the Arabian Peninsula shore. From 1972 to 2013, the area covered by mangroves increased by about 0.29% y-1. We conclude that the trend exhibited by Red Sea mangroves departs from the general global decline of mangroves. Along the Red Sea, mangroves expanded by 12% over the 41 years from 1972 to 2013. Losses to Red Sea mangroves, mostly due to coastal development, have been compensated by afforestation projects.

  17. Analysis of Shuttle Multispecral Infrared Radiometer measurements of the western Saudi Arabian shield.

    USGS Publications Warehouse

    Rowan, L.C.; Goetz, A.F.H.; Abbott, E.

    1987-01-01

    During the November 12-14, 1981 mission of the space shuttle Columbia, the Shuttle Multispectral Infrared Radiometer (SMIRR) recorded radiances in 10 channels along a 100m wide groundtrack across the western Saudi Arabian shield.-from Authors

  18. Application of Space Technology to Discovery of Ancient Desert Trade Routes in the Southern Arabian Peninsula

    NASA Technical Reports Server (NTRS)

    Blom, Ronald; Crippen, Robert; Hedges, George; Zarins, Juris

    1997-01-01

    Over the last decade, an unusual combination of historical research, traditional archaeology, and application of space technolgy has demonstrated the existence of trans-desert trade routes in the sourthern Arabian peninsula.

  19. The prehistory of the Arabian peninsula: deserts, dispersals, and demography.

    PubMed

    Groucutt, Huw S; Petraglia, Michael D

    2012-05-01

    As a geographic connection between Africa and the rest of Eurasia, the Arabian Peninsula occupies a central position in elucidating hominin evolution and dispersals. Arabia has been characterized by extreme environmental fluctuation in the Quaternary, with profound evolutionary and demographic consequences. Despite the importance of the region, Arabia remains understudied. Recent years, however, have seen major developments in environmental studies and archeology, revealing that the region contains important records that should play a significant role in future paleoanthropological narratives.(1-3) The emerging picture of Arabia suggests that numerous dispersals of hominin populations into the region occurred. Populations subsequently followed autochthonous trajectories, creating a distinctive regional archeological record. Debates continue on the respective roles of regional hominin extinctions and population continuity, with the latter suggesting adaptation to arid conditions. PMID:22718479

  20. SEISMIC DATA FOR NUCLEAR EXPLOSION MONITORING IN THE ARABIAN PENINSULA

    SciTech Connect

    Rodgers, A; Al-Amri, A

    2004-07-08

    We report results from the third and final year of our project (ROA0101-35) to collect seismic event and waveform data recorded in and around the Arabian Peninsula. This effort involves several elements. We are working with King Abdulaziz City for Science and Technology to collect data from the Saudi National Seismic Network, that consists of 38 digital three-component stations (27 broadband and 11 short-period). We have an ongoing collaboration with the Kuwait Institute for Scientific Research, which runs the eight station Kuwait National Seismic Network. We installed two temporary broadband stations in the United Arab Emirates (funded by NNSA NA-24 Office of Non-Proliferation & International Security). In this paper we present a summary of data collected under these efforts including integration of the raw data into LLNL's Seismic Research Database and preliminary analysis of souce parameters and earth structure.

  1. Performance modeling of Arabian asphalt using HP-GPC

    NASA Astrophysics Data System (ADS)

    Asi, I. M.; Wahhab, H. I. Al-Abdul; Al-Dubabi, I. A.; Ali, M. F.

    1997-08-01

    In this study, Arabian neat asphalt samples were collected from different asphalt producing refineries in the Gulf countries. Another set of polymer modified samples was also included in this study. In the polymer modification process, 5,10, and 15% crumb rubber (CRT) and 3,6, and 9% styrene-butadiene-styrene (SBS) were used. All asphalt samples were subjected to two aging processes to simulate heating, mixing, compaction, and in-service aging. The asphalt samples at the different aging stages were subjected to performance-based tests that were adapted and/or modified by the Strategic Highway Research Program (SHRP) team. High pressure gel permeation chromatography (HP-GPC) was used to chemically analyze the test samples by generating profiles of their molecular size distribution. Models were built to predict the performance-based properties from the produced HP-GPC profiles.

  2. Wintertime precipitation variability over the Arabian Peninsula and its relationship with ENSO in the CAM4 simulations

    NASA Astrophysics Data System (ADS)

    Niranjan Kumar, K.; Ouarda, T. B. M. J.; Sandeep, S.; Ajayamohan, R. S.

    2016-01-01

    The climate variability on Earth is strongly influenced by the changes in the Sea Surface Temperature (SST) anomalies in the tropical oceans. More specifically, the inter-annual climate variability in the tropics as well as extra-tropical areas has large impact due to the anomalous SSTs in the tropical Pacific coupled with the El Niño Southern Oscillation (ENSO) through atmospheric teleconnections. However, the effect of ENSO on Middle Eastern region, specifically the Arabian Peninsula (AP) is marginally explored in previous studies. Hence, this study explicitly focuses on the assessment of ENSO variability and its winter climate teleconnections to the AP using the Community Atmospheric Model Version 4.0 (CAM4) simulations and Reanalysis datasets. ENSO teleconnections are also evaluated based on two sensitivity experiments (ENSO-related and ENSO-unrelated) using the CAM4 model. It is observed that during El Niño years the peninsular region receives more rainfall through enhanced moisture transport associated with anomalous westerly winds from adjoining Seas. The Rossby wave energy propagation in the atmosphere underlies important teleconnections involving ENSO. It is also noticed that there exist a distinct change in the phase of the Rossby wave pattern during El Niño and La Niña years which further causes the shift in the position of the jet stream over the Middle East.

  3. The ant genus Carebara Westwood in the Arabian Peninsula (Hymenoptera, Formicidae)

    PubMed Central

    Sharaf, Mostafa R.; Aldawood, Abdulrahman S.

    2013-01-01

    Abstract The ant genus Carebara of the Arabian Peninsula is revised. Carebara abuhurayri Sharaf & Aldawood, 2011 is synonymized under Carebara arabica Collingwood & van Harten, 2001. Carebara arabica is redescribed and a Neotype is fixed based on a specimen collected from southwestern Kingdom of Saudi Arabia. A new species, C. fayrouzae sp. n. is described from Saudi Arabia based on queens, major and minor workers. Keys to major and minor workers of the two Arabian Carebara species are given. PMID:24363580

  4. Attitudes of Saudi Arabian Undergraduate Medical Students towards Health Research

    PubMed Central

    Al-Hilali, Sara M.; Al-Kahtani, Eman; Zaman, Babar; Khandekar, Rajiv; Al-Shahri, Abdullah; Edward, Deepak P.

    2016-01-01

    Objectives: This study aimed to evaluate attitudes, perceptions and perceived barriers towards health research among Saudi Arabian undergraduate medical students. Methods: This cross-sectional study took place between August and October 2014 and included 520 students from five medical schools across Saudi Arabia. An anonymous online survey with 21 close-ended questions was designed to assess students’ attitudes towards research, contribution to research-related activities, awareness of the importance of research, perception of available resources/opportunities for research, appreciation of medical students’ research contributions and perceived barriers to research. Responses were scored on a 5-point Likert scale. Results: A total of 401 students participated in the study (response rate: 77.1%). Of these, 278 (69.3%) were female. A positive attitude towards research was reported by 43.9% of the students. No statistically significant differences were observed between genders with regards to attitudes towards and available resources for research (P = 0.500 and 0.200, respectively). Clinical students had a significantly more positive attitude towards research compared to preclinical students (P = 0.007). Only 26.4% of the respondents believed that they had adequate resources/opportunities for research. According to the students, perceived barriers to undertaking research included time constraints (n = 200; 49.9%), lack of research mentors (n = 95; 23.7%), lack of formal research methodology training (n = 170; 42.4%) and difficulties in conducting literature searches (n = 145; 36.2%). Conclusion: Less than half of the surveyed Saudi Arabian medical students had a positive attitude towards health research. Medical education policies should aim to counteract the barriers identified in this study. PMID:26909216

  5. Sea Level Variability in the Central Region of the Red Sea

    NASA Astrophysics Data System (ADS)

    Abualnaja, Yasser O.; Limeburner, Richard; Farrar, J. Thomas; Beardsley, Robert

    2013-04-01

    An array of three bottom pressure/temperature/conductivity (PTC) instruments was deployed along the Saudi Arabian coast of the eastern Red Sea since 2008. These locations, represent the central region of the Red Sea; Al-Lieth (100km south of Jeddah), Thuwal (KAUST) and Arriyas (100km north of Rabigh). Surface sea level/height was calculated from the bottom pressure measurements using the hydrostatic equation. The data analysis displayed the sea level variability into three different scales: 1) On daily time scales: the data showed the most energetic component of sea level variability was the diurnal and semidiurnal tides dominated by the M2, N2, K1 and O1 tidal constituents. 2) On weekly time scales (~10 days): the sea level variability was wind driven with setup and set down up to 40 cm due to the local wind stress. 3) On yearly time scales: the sea level varied approximately 50 cm and was highest in winter (January-February) and lowest in summer (July-August). Barometric pressure also had an annual cycle of approximately 10mb and was highest in January, thus attenuating the amplitude of the annual sea level variability. The data analysis postulate that the only mechanism behind the higher sea level in the central Red Sea during winter months was due to a response to the convergent in the large-scale Red Sea wind stress associated with the Indian Monsoon, which is consisting of NNW winds in the northern part of the Red Sea and SSE winds in the southern part. The amplitude of the principal tidal and sub-tidal sea level variability was coherent at the three sites, but the direction of phase propagation could not be resolved with confidence.

  6. Grandidierella bonnieroides Stephensen, 1948 (Amphipoda, Aoridae)-first record of an established population in the Mediterranean Sea.

    PubMed

    Brutto, Sabrina Lo; Iaciofano, Davide; Lubinevsky, Hadas; Galil, Bella S

    2016-01-01

    The first record in the Mediterranean Sea of the invasive aorid amphipod crustacean Grandidierella bonnieroides is presented. A widespread circumtropical species, recorded off the Saudi coast of the Arabian Gulf, the Red Sea and the Suez Canal, it may have been introduced into the Mediterranean through the Suez Canal. This tube-builder species of soft bottoms recently established a population in the polluted Haifa Bay, Israel. Further, this is the first Mediterranean record of the genus. PMID:27394471

  7. Tomographic Imaging of Upper Mantle P- and S-wave Velocity Heterogeneity Beneath the Arabian Peninsula

    SciTech Connect

    Park, Y; Nyblade, A; Rodgers, A; Al-Amri, A

    2005-08-30

    We report the estimates of three-dimensional P- and S-wave velocity structure beneath the Arabian Peninsula estimated from travel time delay tomography. We have completed travel time measurements and inversion of a partial data set provided by King Abdulaziz City for Science and Technology (KACST). This study builds on previous work by Benoit et al. (2003) following the methods of VanDecar and Crosson (1990) and VanDecar (1991). Data were collected from the Saudi Arabian National Digital Seismic Network (SANDSN) operated by KACST. The network consists of 38 stations (27 broadband and 11 short-period). We augmented the KACST data with delay times measured from permanent Incorporated Research Institutions for Seismology (IRIS) stations in the region (RAYN, EIL and MRNI) and the 1996 Saudi Arabian PASSCAL Experiment. This study shows the inverted P- and S-wave models computed with the combined data with all three different seismic networks (KASCST, IRIS, and the 1996 Saudi Arabian PASSCAL experiment) with best coverage beneath the Arabian Shield. Tomographic images reveal low velocity features in the upper mantle along a north-south line from the southern Asir region to the northeastern portion of the Arabian Shield.

  8. The Role of Tigris Euphrates Discharge on Coastal SST in the Arabian Gulf

    NASA Astrophysics Data System (ADS)

    Becker, R.; Sanders, J.

    2013-12-01

    The Tigris-Euphrates (T-E) river system provides most of the freshwater recharge into the Arabian/Persian Gulf, through the Shatt el-Arab, into the northern Gulf. Over the past decades, increased dam storage for irrigation and hydropower throughout the region has modified the characteristics of this flow. As a result, flow into the Iraqi Marshes has been reduced by at least half, with reduction in both peak and overall flow, and a corresponding decrease in flow through the Shatt el-Arab. This change in flow characteristics is observable in the waters on the Northern Gulf and in Kuwait bay. AVHRR Pathfinder v5.0 8 day data was assembled for the time period 1985-2010. Time series were extracted for sea surface temperature (SST) for locations in the Northern and Central Gulf and Kuwait Bay. These were compared with regional precipitation and GRACE water equivalent thickness variations in the upper and lower T-E basin, and published flow estimates. Results were used to examine 1) the overall impact of discharge on SST in the coastal area affected by T-E watershed discharge; 2) the impact of reduced flow years due to damming and drought years on the differences between coastal and bay SST and central Gulf SST. Annual peak flow in the period Dec-April was found to provide a lowering of coastal SST by more than 1C compared with more well mixed water in the central Gulf. This effect was not seen to be less than half during drought years (e.g. 2006-2008). Climate models predict end of century scenarios of precipitation similar to those seen during 2007-2008. The impact of this lower discharge from the Shatt el-Arab combined with predicted regional warming may result in habitat changes in coastal waters in the Northern Gulf.

  9. Geological evolution of the Iraqi Mesopotamia Foredeep, inner platform and near surroundings of the Arabian Plate

    NASA Astrophysics Data System (ADS)

    Sissakian, Varoujan K.

    2013-08-01

    west of the Ga'ara Depression, represented by Early-Late Paleocene phosphatic facies, which is well developed east of Rutbah Uplift and extends eastwards in the Foredeep. Eocene rocks; west of Rutbah Uplift are represented by marine carbonates that has wide aerial coverage in south Iraq. Locally, east of Rutbah Uplift unconformable contacts are recorded between Early, Middle and Late Eocene rocks. During Oligocene, in the eastern margin of the Inner Platform, the Outer Platform was uplifted causing very narrow depositional Oligocene basin. Therefore, very restricted exposures are present in the northern part of the Inner Platform (north of Ga'ara Depression), represented by reef, forereef sediments of some Oligocene formations. The Miocene rocks have no exposures west of Rutbah Uplift, but north and northwestwards are widely exposed represented by Early Miocene of marine carbonates with marl intercalations. Very locally, Early Miocene deltaic clastics and carbonates, are interfingering with the marine carbonates. The last marine open sea sediments, locally with reef, represent the Middle Miocene rocks and fore reef facies that interfingers with evaporates along the northern part of Abu Jir Fault Zone, which is believed to be the reason for the restriction of the closed lagoons; in the area. During Late Miocene, the continental phase started in Iraq due to the closure of the Neo-Tethys and collision of the Sanandaj Zone with the Arabian Plate. The continental sediments consist of fine clastics. The Late Miocene - Middle Pliocene sediments were not deposited in the Inner Platform. The Pliocene-Pleistocene sediments are represented by cyclic sediments of conglomeratic sandstone overlain by fresh water limestone, and by pebbly sandstone. The Quaternary sediments are poorly developed in the Inner Platform. Terraces of Euphrates River and those of main valleys represent pleistocene sediments. Flood plain of the Euphrates River and those of large valleys represent Holocene

  10. New records of species of Saemundssonia (Insecta: Phthiraptera: Philopteridae) infesting breeding terns in the Arabian Peninsula, with notes on their phylogeny and ecology.

    PubMed

    Shobrak, Mohammed; Alahmed, Azzam; Palma, Ricardo; Almalki, Mohammed; Nasser, Mohamed Gamal El-Den

    2015-07-01

    Six species of terns, which breed on the Arabian Peninsula, were examined for head chewing lice of the genus Saemundssonia in four different islands around the coasts of Saudi Arabia, both in the Red Sea and in the Arabian Gulf. Four louse species were collected: Saemundssonia laticaudata, Saemundssonia melanocephalus, Saemundssonia meridiana and Saemundssonia sternae, of which three are recorded for the first time from this region. Also, we record three new host-louse associations for the world-Saemundssonia laticaudata and Saemundssonia sternae from white-cheeked terns and Saemundssonia melanocephalus from Saunders's terns-including a host-switch event of Saemundssonia laticaudata on white-cheeked terns in the Karan Island population. Gene bank data for the COI gene from seven species of Saemundssonia that infest marine birds were used to propose evolutionary trees using two different statistical methods: maximum parsimony (MP) and neighbour joining (NJ). The result indicated that the tree which was produced by NJ is likely to be more accurate as it appeared more compatible with hosts' phylogeny. The trees indicate relationships between tern Saemundssonia and congeneric species from other marine birds, especially from gulls. An ANOVA was also conducted to test the mean parasite load for each tern species studied, and results indicate that there is a relation between louse loads and colonization behaviour of the hosts. Data from lice examined and illustrations of lice and their hosts are also included. PMID:25924793

  11. Monsoon oscillations regulate fertility of the Red Sea

    NASA Astrophysics Data System (ADS)

    Raitsos, Dionysios E.; Yi, Xing; Platt, Trevor; Racault, Marie-Fanny; Brewin, Robert J. W.; Pradhan, Yaswant; Papadopoulos, Vassilis P.; Sathyendranath, Shubha; Hoteit, Ibrahim

    2015-02-01

    Tropical ocean ecosystems are predicted to become warmer, more saline, and less fertile in a future Earth. The Red Sea, one of the warmest and most saline environments in the world, may afford insights into the function of the tropical ocean ecosystem in a changing planet. We show that the concentration of chlorophyll and the duration of the phytoplankton growing season in the Red Sea are controlled by the strength of the winter Arabian monsoon (through horizontal advection of fertile waters from the Indian Ocean). Furthermore, and contrary to expectation, in the last decade (1998-2010) the winter Red Sea phytoplankton biomass has increased by 75% during prolonged positive phases of the Multivariate El Niño-Southern Oscillation Index. A new mechanism is reported, revealing the synergy of monsoon and climate in regulating Red Sea greenness.

  12. Interannual variability of the Indian summer monsoon associated with the air-sea feedback in the northern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Shukla, Ravi P.; Huang, Bohua

    2016-03-01

    Using observation-based analyses, this study identifies the leading interannual pattern of the Indian summer monsoon rainfall (ISMR) independent of ENSO and examines the potential mechanisms of its formation. For this purpose, an objective procedure is used to isolate the variability of the summer precipitation associated with the contemporary ENSO state and in previous winter-spring, which influence the Indian summer monsoon (ISM) region in opposite ways. It is shown that the leading pattern of these ENSO-related monsoon rainfall anomalies reproduces some major ISMR features and well represents its connections to the global-scale ENSO features in both lower and upper troposphere. On the other hand, the leading pattern derived from the precipitation anomalies with the ENSO component removed in the ISM and surrounding region also accounts for a substantial amount of the monsoon precipitation centered at the eastern coast of the subtropical Arabian Sea, extending into both the western Indian Ocean and the Indian subcontinent. The associated atmospheric circulation change is regional in nature, mostly confined in the lower to mid troposphere centered in the Arabian Sea, with a mild connection to an opposite tendency centered at the South China Sea. Further analyses show that this regional pattern is associated with a thermodynamic air-sea feedback during early to mid summer season. Specifically, before the monsoon onset, an anomalous atmospheric high pressure over the Arabian Sea causes excessive shortwave radiation to the sea surface and increases SST in May. The warm SST anomalies peak in June and reduce the sea level pressure. The anomalous cyclonic circulation generates regional convection and precipitation, which also induces subsidence and anticyclonic circulation over the South China Sea. The combined cyclonic-anticyclonic circulation further transport moisture from the western Pacific into the Indian Ocean and causes its convergence into the Arabian Sea. As a

  13. 75 FR 2920 - In the Matter of the Designation of al-Qa'ida in the Arabian Peninsula (AQAP), Also Known as al...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-19

    ... al-Qa'ida Organization in the Arabian Peninsula (AQAP), Also Known as al-Qa'ida in Yemen (AQY), Also... Organization in the Arabian Peninsula (AQAP), also known as al-Qa'ida in Yemen (AQY), also known as...

  14. Chromatographic metasomatism of the Arabian-Nubian lithosphere

    NASA Astrophysics Data System (ADS)

    Kessel, R.; Navon, O.; Stein, M.

    1997-11-01

    Trace elements and isotopic ratios of calc-alkaline and tholeiitic dikes from the very last stage of the late Proterozoic, Pan-African orogeny in the northern Arabian-Nubian Shield (ANS), and alkali basalts from the overlying Phanerozoic section are used to constrain the composition and model the evolution of the lithospheric mantle in this region. The dikes and basalts are interpreted as lithospheric melts formed during the post-orogenic (and post-subduction) history of the shield. While the mafic member of all suites share a primitive La/Th ratio, the Nb/Th and Ce/Pb are distinct for each suite. The (Nb/Th)PM (primitive mantle normalized) is ~0.2 in the calc-alkaline dikes and 1.4 in the tholeiitic dikes and the Phanerozoic alkali basalts. The (Ce/Pb)PM ratios are low in the dikes (0.4 in the calc-alkaline and 0.3 in the tholeiitic) and high in the Phanerozoic basalts (2.8). We suggest that the variations in the trace element ratios reflect sampling of different zones in the lithospheric mantle, which were formed by subduction related metasomatism of the mantle wedge. We constructed a chromatographic model to explain this zonation. In this model a plume-derived oceanic lithosphere is subducted and dehydrates at depth. Fluids released from the dehydrating slab metasomatize the overlying wedge and form amphibole-rich channels. Nb is preferentially taken by the amphibole and is enriched only in the lower zones of the column. The other elements (U, Th, REE and especially Pb and Rb) behave incompatibly. They are enriched in the fluid and transported efficiently to the melting zone in the centre of the wedge. Dehydration of the base of the wedge as it descends below the amphibole stability field depletes this region in Pb and Rb. After the end of subduction, the wedge is fossilized and forms the lithospheric mantle. The zone above the Nb concentration front is sampled by the calc-alkaline magmas. The tholeiitic magmas sample the zone below the Nb front. The Phanerozoic

  15. Mantle Flow beneath Arabia Offset from the Opening Red Sea

    NASA Astrophysics Data System (ADS)

    Stein, S. A.; Chang, S.; Merino, M.; van der Lee, S.; Stein, C. A.

    2010-12-01

    The rifting of continents involves a complex and poorly understood sequence of lithospheric stretching, volcanism, and mantle flow that eventually gives rise to seafloor spreading that forms a new ocean basin. The Red Sea, forming as the Arabian plate diverges from Africa, is a classic area for studying this process. Here, we present new insight from joint inversion of seismic wave travel times and waveforms to map velocity structure beneath Arabia and its surroundings. We find the low velocities expected for hot upwelling mantle material centered beneath the southern Red Sea and Gulf of Aden, consistent with the active spreading there. However, this hot material extends not below the northern Red Sea, but is instead offset to the east beneath Arabia, showing northward upper mantle flow from the Afar hotspot. The location of this low velocity channel beneath volcanic rocks erupted since rifting began 30 million years ago indicates that although the flow originates from the hotspot that is essentially fixed in the upper mantle, the channel moves with the Arabian plate. We thus propose that the absence of seafloor spreading in the northern Red Sea reflects the offset mantle flow. Because this offset has existed for millions of years, it is unclear whether it will evolve into seafloor spreading, rifting of Arabia above the channel, or both. This situation has aspects of the end-member models of rifting initiated by either mantle flow or lithospheric extension, and thus shows that the two can occur somewhat independently in different places before coalescing to seafloor spreading.

  16. Seagrass habitat complexity and macroinvertebrate abundance in Lakshadweep coral reef lagoons, Arabian Sea

    NASA Astrophysics Data System (ADS)

    Ansari, Z. A.; Rivonker, C. U.; Ramani, P.; Parulekar, A. H.

    1991-09-01

    Macrofauna of seagrass community in the five Lakshadweep atolls were studied and compared. The associated epifaunal and infaunal taxa comprising nine major taxonomic groups, showed significant differences in the total number of individuals (1041 8411 m-2) among sites and habitats. The density of macrofauna was directly related to mean macrophytic biomass (405 895 g wet wt. m-2). The fauna was dominated by epifaunal polychaetes, amphipods and isopods in the vegetated areas. When compared with the density of nearby unvegetated areasleft( {bar x = 815{text{m }}^{ - 2} } right), seagrass meadows harbour a denser and richer macroinvertebrate assemblageleft( {bar x = 4023{text{m }}^{ - 2} } right).

  17. Biodegradation of low-density polyethylene by marine bacteria from pelagic waters, Arabian Sea, India.

    PubMed

    Harshvardhan, Kumar; Jha, Bhavanath

    2013-12-15

    Sixty marine bacteria isolated from pelagic waters were screened for their ability to degrade low-density polyethylene; among them, three were positive and able to grow in a medium containing polythene as the sole carbon source. The positive isolates were identified as Kocuria palustris M16, Bacillus pumilus M27 and Bacillus subtilis H1584 based on the 16S rRNA gene sequence homology. The weight loss of polyethylene was 1%, 1.5% and 1.75% after 30 days of incubation with the M16, M27 and H1584 isolates, respectively. The maximum (32%) cell surface hydrophobicity was observed in M16, followed by the H1584 and M27 isolates. The viability of the isolates growing on the polyethylene surface was confirmed using a triphenyltetrazolium chloride reduction test. The viability was also correlated with a concomitant increase in the protein density of the biomass. Polyethylene biodegradation was further confirmed by an increase in the Keto Carbonyl Bond Index, the Ester Carbonyl Bond Index and the Vinyl Bond Index, which were calculated from FT-IR spectra. PMID:24210946

  18. The sacrificial cathodic protection of UNS C71500 heat exchanger tubes in Arabian Gulf sea water

    SciTech Connect

    Al-Hashem, A.; Carew, J.A.; Al-Sayegh, A.

    1997-12-01

    A laboratory investigation using a specially designed circulating test rig was carried out to study the effectiveness of achieving complete cathodic protection of UNS C71500 heat exchanger tubes in seawater applications. Results indicated that the galvanic current distribution covered the entire 6m length of the tube. The presence of sulfide ions as pollutants in seawater shifted the galvanic potentials of the tubes to more active potentials and prevented the formation of protective films that normally form.

  19. Himalaya evolution at Paleogene-Neogene boundary unraveled by zircon age spectrum from Arabian Sea Sediments

    NASA Astrophysics Data System (ADS)

    Feng, Han; Lu, Huayu; Zhang, Hanzhi

    2016-04-01

    Although virtually all the intensive orogenic activities of Himalaya occurred in Neogene, the tectonic evolution of this high mountain range in Paleogene is poorly understood. Investigations of tectonic change pattern at Paleogene-Neogene boundary are important to better understand the interaction between mountain building and climate evolution. Here we present new U-Pb ages of zircon grains from Indus Fan sediments to constrain the orogenic history of Himalaya at Paleogene-Neogene boundary. 11 samples between late Oligocene and early Miocene from ODP 117 cores are dated by the zircon U-Pb technique. We calculate relative contributions of potential sources by counting zircon grains for each sample, and the quantized results indicate Himalaya contributed sediments to the coring site, and an extremely high input from Great and Tethyan Himalaya during late Oligocene-early Miocene. Four samples in Pleistocene are also dated for comparison, which indicates that high proportion of Lesser Himalaya has contributed to the sediment in Pleistocene. Our results suggest that the high contribution of Great and Tethyan Himalaya at Paleogene-Neogene boundary might correlate with the beginning of activity of MCT and extension of STD with leucogranite intrusion along Himalaya, which give rise to the extensive Great Himalaya exhumation. Our study demonstrates that zircon U-Pb dating technique is a good tool to reconstruct erosional history of mountain building on a tectonic timescale. Key words: ODP, Himalaya, Indus Fan, zircon U-Pb dating, Paleogene-Neogene boundary

  20. A relook into the crustal architecture of Laxmi Ridge, northeastern Arabian Sea from geopotential data

    NASA Astrophysics Data System (ADS)

    Nair, Nisha; Anand, S. P.; Rajaram, Mita; Rao, P. Rama

    2015-04-01

    In this study, we undertake analysis of ship-borne gravity-magnetic and satellite-derived free-air gravity (FAG) data to derive the crustal structure of Laxmi Ridge and adjacent areas. 2D and 3D crustal modelling suggests that the high resolution FAG low associated with the ridge is due to underplating and that it is of continental nature. From Energy Spectral Analysis, five-depth horizons representing interface between different layers are demarcated that match those derived from 2D models. Magnetic sources from EMAG2 data, various filtered maps and absence of underplating in the EW section suggest that the EW and NW-SE segment of the Laxmi Ridge is divided by the Girnar fracture zone and probably associated with different stages of evolution. From the derived inclination parameters, we infer that the region to the north of Laxmi Ridge, between Laxmi and Gop Basins, is composed of volcanic/basaltic flows having Deccan affinity, which might have been emplaced in an already existing crust. The calculated inclination parameters derived from the best fit 2D model suggests that the rifting in the Gop Basin preceded the emplacement of the volcanics in the region between Laxmi and Gop Basins. The emplacement of volcanic/basaltic flows may be associated with the passage of India over the Reunion hotspot.

  1. The Influence of Wind and Basin Eddies in Controlling Sea Level Variations in the Coastal Red Sea

    NASA Astrophysics Data System (ADS)

    Abualnaja, Yasser O.; Churchill, James H.; Nellayaputhenpeedika, Mohammedali; Limeburner, Richard

    2015-04-01

    Sea level variations in the central Red Sea coastal zone span a range of roughly 1.2 m. Though relatively small, these water level changes can significantly impact the environment over the shallow reef tops prevalent in the central Red Sea, altering the water depth by a factor or two or more. Roughly half of the coastal sea level variance in central Red Sea is due to elevation changes in an 'intermediate' frequency band, with periods between 2 days and 1 month. We examined the sea level signal in this band using the data from pressure sensors maintained for more than five years at a number of locations in Saudi Arabian coastal waters between 20.1 and 23.5 oN. We find that the intermediate-band sea level variations are strongly correlated with the local wind stress measured at a meteorological buoy. The maximum pressure-wind correlation occurs at wind direction closely aligned with the alongshore orientation and at a lag (wind leading) of 45 hr, which is consistent with the expected response of the coastal sea level to local wind forcing. However, less than half of the sea level variance in the intermediate band is related, through linear correlation, with local wind forcing. Our analysis indicates that the residual coastal sea level signal, not associated with wind forcing, is largely driven remotely by the passage of mesoscale eddies, revealed by satellite altimeter-derived sea level anomaly fields of the central Red Sea. These eddy-driven coastal sea level changes occur on time scales of 10-30 days. They span a range of 0.5 m, and thus constitute an import component of the sea level signal in the coastal Red Sea.

  2. Identification of upwelling areas in the Oman Sea Using Satellite Data

    NASA Astrophysics Data System (ADS)

    Moradi, Masoud

    2016-07-01

    Satellite-derived sea-surface temperature, TOPEX/POSEIDON (T/P) sea-level anomalies (SLAs), modeled wind data, and hydrodynamic data from World Ocean Database were used to characterize the upwelling along the Oman Sea coasts during 2002 - 2012. Principal Component Analysis (PCA) of the satellite-derived sea-surface temperature (SST) shows the first mode affected by upwelling processes, which represents a biannual variability. In addition, the SST shows the upwelling front moving offshore with the development of Southwest (SW) Monsoon in early June. SST shows the persistence of cold upwelling waters for nearly a month after the end of the SW Monsoon within the bays along the Oman coast. TOPEX/POSEIDON SLAs indicate that with the onset of the SW Monsoon, a 30-cm drop in height is observed along the Oman coast associated the presence of the cool upwelled waters. This drop in height sets up a horizontal pressure gradient and results in a compensating along-shore, northeastward flowing, geostrophic current (East Arabian Current) during the SW Monsoon. Similarly, the altimeter data slow an offshore decrease in height during the Northeast (NE) Monsoon, indicating a seasonal reversal in direction of the East Oman Currents with flow to the southwest. The following upwelling characteristics are identified for the Oman upwelling zone: 1- Upwelling zones have seen along Oman and Pakistan coasts and in the western coasts, like Iran, persistent upwelling zones are not available. 2- Upwelling zones along Oman coasts are more persistent and developed than in Pakistan coastal area. 3- Upwelling in the Oman and East Pakistan coasts starts with SW-Monsoon and will developed in the mid-August, adjusted with summer cooling. 4- Along Oman Sea, upwelling zones were developed between Rasal-Haddad and the southern bay. Mean SST during SW-Monsoon is about 22 °C. 5-Waters with temperature about 23°C were upwelled from depth 50-75 m along Oman coasts, and about 50 m along Pakistan coasts. 6

  3. A pedigree-based study of mitochondrial D-loop DNA sequence variation among Arabian horses.

    PubMed

    Bowling, A T; Del Valle, A; Bowling, M

    2000-02-01

    Through DNA sequence comparisons of a mitochondrial D-loop hypervariable region, we investigated matrilineal diversity for Arabian horses in the United States. Sixty-two horses were tested. From published pedigrees they traced in the maternal line to 34 mares acquired primarily in the mid to late 19th century from nomadic Bedouin tribes. Compared with the reference sequence (GenBank X79547), these samples showed 27 haplotypes with altogether 31 base substitution sites within 397 bp of sequence. Based on examination of pedigrees from a random sampling of 200 horses in current studbooks of the Arabian Horse Registry of America, we estimated that this study defined the expected mtDNA haplotypes for at least 89% of Arabian horses registered in the US. The reliability of the studbook recorded maternal lineages of Arabian pedigrees was demonstrated by haplotype concordance among multiple samplings in 14 lines. Single base differences observed within two maternal lines were interpreted as representing alternative fixations of past heteroplasmy. The study also demonstrated the utility of mtDNA sequence studies to resolve historical maternity questions without access to biological material from the horses whose relationship was in question, provided that representatives of the relevant female lines were available for comparison. The data call into question the traditional assumption that Arabian horses of the same strain necessarily share a common maternal ancestry. PMID:10690354

  4. Secondary pores in carbonate reservoirs on Arabian Peninsula

    SciTech Connect

    Nurmi, R.; Waterhouse, M.; Watfa, M.

    1987-05-01

    Nearly all of the giant carbonate reservoirs on the Arabian Peninsula have both primary and secondary pore systems. There are, however, significant stratigraphic and geographic variations of origin, volume, and reservoir importance of secondary pores. The Permian Khuff reservoir zones generally has more secondary porosity than any younger, or shallower, reservoir formations. Highly permeable idiotopic (sucrosic) dolomites are commonly developed in zones which originally contained primary pores. The zones with the highest porosity often contain secondary pores, with calcite-free oomoldic dolomites having higher permeability than oomoldic limestones. Fractures resulting from halokinetics and/or salt dissolution are generally the most important secondary pores in Khuff reservoirs. The prolific Jurassic Arab reservoir zones, generally have lesser amounts of secondary pores than Khuff reservoirs, but a variety of secondary pores are present. Commonly the Arab C zone contains the greatest volume of secondary pores, generally of a moldic (grain and/or skeletal) nature. Secondary porosity associated with dolomitization is regionally more common in the eastern Gulf. Cretaceous (rudist) reefal and chalk reservoirs often contain zones of secondary porosity with enhanced permeability resulting from the leaching of aragonitic and high-magnesium calcite skeletal material. Secondary porosity is present in the western gulf in both the Minagish grainstones and dolomitized Shuaiba Formation, whereas the grainstones of the eastern gulf have little secondary porosity. Large fracture systems are present everywhere in low-permeability chalks and wackestones. An unusually high degree of porosity heterogeneity appears to be ubiquitous in Cretaceous sequences.

  5. The potential of high heat generating granites as EGS source to generate power and reduce CO2 emissions, western Arabian shield, Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Chandrasekharam, D.; Lashin, A.; Al Arifi, N.; Al Bassam, A.; El Alfy, M.; Ranjith, P. G.; Varun, C.; Singh, H. K.

    2015-12-01

    Saudi Arabia's dependence on oil and gas to generate electricity and to desalinate sea water is widely perceived to be economically and politically unsustainable. A recent business as usual simulation concluded that the Kingdom would become an oil importer by 2038. There is an opportunity for the country to over come this problem by using its geothermal energy resources. The heat flow and heat generation values of the granites spread over a cumulative area of 161,467 sq. km and the regional stress regime over the western Saudi Arabian shield strongly suggest that this entire area is potential source of energy to support 1) electricity generation, 2) fresh water generation through desalination and 3) extensive agricultural activity for the next two decades. The country can adopt a policy to harness this vast untapped enhanced geothermal systems (EGS) to mitigate climate and fresh water related issues and increase the quantity of oil for export. The country has inherent expertise to develop this resource.

  6. Allelic polymorphism in arabian camel ribonuclease and the amino acid sequence of bactrian camel ribonuclease.

    PubMed

    Welling, G W; Mulder, H; Beintema, J J

    1976-04-01

    Pancreatic ribonucleases from several species (whitetail deer, roe deer, guinea pig, and arabian camel) exhibit more than one amino acid at particular positions in their amino acid sequences. Since these enzymes were isolated from pooled pancreas, the origin of this heterogeneity is not clear. The pancreatic ribonucleases from 11 individual arabian camels (Camelus dromedarius) have been investigated with respect to the lysine-glutamine heterogeneity at position 103 (Welling et al., 1975). Six ribonucleases showed only one basic band and five showed two bands after polyacrylamide gel electrophoresis, suggesting a gene frequency of about 0.75 for the Lys gene and about 0.25 for the Gln gene. The amino acid sequence of bactrian camel (Camelus bactrianus) ribonuclease isolated from individual pancreatic tissue was determined and compared with that of arabian camel ribonuclease. The only difference was observed at position 103. In the ribonucleases from two unrelated bactrian camels, only glutamine was observed at that position. PMID:962846

  7. Local adaptation constrains the distribution potential of heat-tolerant Symbiodinium from the Persian/Arabian Gulf

    PubMed Central

    D'Angelo, Cecilia; Hume, Benjamin C C; Burt, John; Smith, Edward G; Achterberg, Eric P; Wiedenmann, Jörg

    2015-01-01

    The symbiotic association of corals and unicellular algae of the genus Symbiodinium in the southern Persian/Arabian Gulf (PAG) display an exceptional heat tolerance, enduring summer peak temperatures of up to 36 °C. As yet, it is not clear whether this resilience is related to the presence of specific symbiont types that are exclusively found in this region. Therefore, we used molecular markers to identify the symbiotic algae of three Porites species along >1000 km of coastline in the PAG and the Gulf of Oman and found that a recently described species, Symbiodinium thermophilum, is integral to coral survival in the southern PAG, the world's hottest sea. Despite the geographic isolation of the PAG, we discovered that representatives of the S. thermophilum group can also be found in the adjacent Gulf of Oman providing a potential source of thermotolerant symbionts that might facilitate the adaptation of Indian Ocean populations to the higher water temperatures expected for the future. However, corals from the PAG associated with S. thermophilum show strong local adaptation not only to high temperatures but also to the exceptionally high salinity of their habitat. We show that their superior heat tolerance can be lost when these corals are exposed to reduced salinity levels common for oceanic environments elsewhere. Consequently, the salinity prevailing in most reefs outside the PAG might represent a distribution barrier for extreme temperature-tolerant coral/Symbiodinium associations from the PAG. PMID:25989370

  8. Local adaptation constrains the distribution potential of heat-tolerant Symbiodinium from the Persian/Arabian Gulf.

    PubMed

    D'Angelo, Cecilia; Hume, Benjamin C C; Burt, John; Smith, Edward G; Achterberg, Eric P; Wiedenmann, Jörg

    2015-12-01

    The symbiotic association of corals and unicellular algae of the genus Symbiodinium in the southern Persian/Arabian Gulf (PAG) display an exceptional heat tolerance, enduring summer peak temperatures of up to 36 °C. As yet, it is not clear whether this resilience is related to the presence of specific symbiont types that are exclusively found in this region. Therefore, we used molecular markers to identify the symbiotic algae of three Porites species along >1000 km of coastline in the PAG and the Gulf of Oman and found that a recently described species, Symbiodinium thermophilum, is integral to coral survival in the southern PAG, the world's hottest sea. Despite the geographic isolation of the PAG, we discovered that representatives of the S. thermophilum group can also be found in the adjacent Gulf of Oman providing a potential source of thermotolerant symbionts that might facilitate the adaptation of Indian Ocean populations to the higher water temperatures expected for the future. However, corals from the PAG associated with S. thermophilum show strong local adaptation not only to high temperatures but also to the exceptionally high salinity of their habitat. We show that their superior heat tolerance can be lost when these corals are exposed to reduced salinity levels common for oceanic environments elsewhere. Consequently, the salinity prevailing in most reefs outside the PAG might represent a distribution barrier for extreme temperature-tolerant coral/Symbiodinium associations from the PAG. PMID:25989370

  9. Current Arabian Plate Motion From Campaign GPS Measurements in Saudi Arabia: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Almuslmani, B.; Teferle, F. N.; Bingley, R. M.; Moore, T.

    2007-12-01

    Current investigations of the motions of the Arabian and its neighboring plates are primarily based on GPS measurements obtained in the surrounding areas of the Arabian plate, with few stations actually located on the Arabian plate itself in the Kingdom of Saudi Arabia. In order to advance the knowledge of the dynamics of the Arabian plate and its intra-plate deformations, the General Directorate of Military Survey (GDMS), through collaboration with the Institute of Engineering Surveying and Space Geodesy (IESSG), densified the GPS network in Saudi Arabia, covering nearly two thirds of the tectonic plate. Since July 2002, a network of 32 GPS stations has been established at locations of the Saudi Arabia geodetic network. At all of these GPS stations a concrete pillar has been used as the monument and the locations have been selected in order to give the broadest distribution of observing sites. During 2005, 27 additional GPS stations in the Hejaz and Asser Mountains, and the Farasan Islands, all in south-western Saudi Arabia, have been established, for which the past and future campaign GPS measurements will provide valuable data for investigations of crustal deformations close to the plate boundaries between the Nubia, Somalian and Arabian plates. In this presentation we will show results in the form of velocity field and plate motion estimates based on data from at least three campaigns occupying the initial 32 GDMS GPS network stations, but also from a number of IGS stations in the region. Our reference frame is aligned to ITRF2005 and uses approximately 40 IGS reference frame stations located on all major tectonic plates, e.g. Nubia and Somalia, surrounding the Arabian plate. Furthermore, we apply absolute satellite and receiver antenna phase center models together with newly available GPS products from a recent global re-processing effort.

  10. Water scarcity in the Arabian Peninsula and socio-economic implications

    NASA Astrophysics Data System (ADS)

    Odhiambo, George O.

    2016-06-01

    The Arabian Gulf, one of the driest parts of the world, is already passing the water scarcity line as defined by the World Health Organization (WHO). The scarcity of renewable water resources and the growing discrepancy between demand and supply of water is a major challenge. Water scarcity is further worsened by rapidly growing demands due to rapid population growth, unsustainable consumption, climate change and weak management institutions and regulations. Water scarcity erodes the socio-economic sustainability of the communities that depend on the depleting storage. In this paper, an analysis of the water security situation within the Arabian Gulf region and the consequent socio-economic implications is presented.

  11. Earliest Phanerozoic or latest Proterozoic fossils from the Arabian Shield

    USGS Publications Warehouse

    Cloud, P.; Awramik, S.M.; Morrison, K.; Hadley, D.G.

    1979-01-01

    We report here the first biologically definable fossils from pre-Saq (pre-Middle Cambrian) rocks of the Arabian Shield. They include the distinctive helically coiled tubular filaments of the oscillatorialean blue-green alga Obruchevella parva as well as two size classes of spheroidal unicells of uncertain affinity. Also present is the conical stromatolite Conophyton and unidentified stromatolites. All occur in cherty limestones of the Jubaylah Group, northern Saudi Arabia, a nonmarine to locally marine taphrogeosynclinal sequence that fills depressions along the northwest-trending Najd faults. Conophyton has heretofore been found only in strata older than about 680 Ma (except for puzzling records in modern hot springs) while Obruchevella is so far known only from rocks between about 680 and 470 Ma old. Thus it appears that the Jubaylah Group is close to the Proterozoic-Phanerozoic transition. The simple spheroidal nanno-fossils are not diagnostic as to age. Their relationships within what appears to be early diagenetic chert suggest a classical algal-mat association. The brecciated and microchanneled appearance of much of the fossiliferous rock, its locally dolomitic nature, and the prevalence of cryptalgalaminate favors a very shallow, locally turbulent, and perhaps episodically exposed marine or marginal marine setting. The Jubaylah Group lies unconformably beneath the Siq Sandstone (basal member of the Saq Sandstone) of medial Cambrian age, rests nonconformably on crystalline basement, and has yielded a K-Ar whole-rock age (on andesitic basalt) of ???540 Ma. To judge from the fossils, however, that age may be as much as 100 Ma or more too young. ?? 1979.

  12. External rhinoplasty for the Arabian nose: a columellar scar analysis.

    PubMed

    Foda, Hossam M T

    2004-01-01

    This study aimed to evaluate columellar scar problems after external rhinoplasty in the Arabian population, and to analyze the technical factors that help prevent such problems and maximize the scar cosmesis. The investigation was conducted in university and private practice settings of the author in Alexandria, Egypt. A total of 600 Arab patients who underwent external rhinoplasty were included in the study. All the patients underwent surgery using the external rhinoplasty approach, in which bilateral alar marginal incisions were connected by an inverted V-shaped transcolumellar incision. At completion of the procedure, a two-layer closure of the columellar incision was performed. At a minimum of 1 year postoperatively, the columellar scar was evaluated subjectively by means of a patient questionnaire, and objectively by clinical examination and comparison of the close-up pre- and postoperative basal view photographs. Objectively, anything less than a barely visible, leveled, thin, linear scar was considered unsatisfactory. Subjectively, 95.5% of the patients rated the scar as unnoticeable, 3% as noticeable but acceptable, and 1.5% as unacceptable. Objectively, the scar was unsatisfactory in 7% of the cases. This was because of scar widening with or without depression (5%), hyperpigmentation (1.5%), and columellar rim notching (0.5%). The use of a deep 6/0 polydioxanon (PDS) suture significantly decreased the incidence of scar widening (p < 0.005).The columellar incision can be used safely in the Arab population regardless of their thick, dark, and oily skin. Technical factors that contributed to the favorable outcome of the columellar scar included proper planning of location and design of the incision used, precise execution, meticulous multilayered closure, and good postoperative care. PMID:15666046

  13. Atmospheric circulation patterns in the Arab region and its relationships with Saudi Arabian surface climate: A preliminary assessment

    NASA Astrophysics Data System (ADS)

    Almazroui, Mansour; Dambul, Ramzah; Islam, Md. Nazrul; Jones, P. D.

    2015-07-01

    This paper establishes and analyses the principal circulation patterns in and around Saudi Arabia (domain: 10°E-70°E; 5°N-40°N) based on the daily mean sea-level pressure (MSLP) 0.75° × 0.75° gridded data derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) re-analysis ERA-Interim for the period 1979-2012. Association of the circulation patterns to the local climate is investigated using observed daily temperature and rainfall data at 27 locations over Saudi Arabia for the period 1979-2010. Using the widely-used mathematical technique principal component analysis (PCA) we determine with MSLP data the principal patterns. We only analyse data for the wet season (October-May). The automated typing procedure establishes 12 circulation types, which represent all the main synoptic features especially those that originate from the Mediterranean, the European and African continents, Siberia, and also the Red and Arabian seas. There is a strong link between the circulation types and surface climate that is synoptically and spatially interpretable. Particular circulation types are associated with specific climatic conditions across the country: rainfall is linked with Types 9, 10 and 11, whilst warm days (nights) with 1, 2, 3, 9, 10, 11 and 12 (1, 2, 3, 10, 11 and 12), and cold days (nights) with 2, 3, 4, 5, 6, 7, 11 and 12 (2, 4, 5, 6, 7 and 8). In terms of regional influences, the circulation types also exhibit specific links between certain types and climatic divisions across Saudi Arabia.

  14. Ballast water exchangeable seas identified by ocean color satellite

    NASA Astrophysics Data System (ADS)

    Kozai, K.; Ishida, H.; Okamoto, K.; Fukuyo, Y.

    The paper describes the identification of ballast water exchangeable seas with MODIS Aqua-derived diffuse attenuation coefficient K 490 along the LNG carrier s routes between Japan and Qatar during the period from 2002 to 2005 Study areas include the northwestern Pacific Ocean the East China Sea the South China Sea the Bay of Bengal and the Arabian Sea Based on the relationship between K 490 and corresponding number of in situ plankton cell densities ballast water exchangeable seas are identified to meet the regulation of ballast water performance standard imposed by International Maritime Organization IMO Furthermore ballast water exchangeable seas are extracted from MODIS-derived K 490 images overlaid with the depth and the distance from shore to meet the IMO regulation of ballast water exchange area As a result the Bay of Bengal is identified as an suitable ballast water exchangeable sea except an anomalously high K 490 area off the coast of Sri Lanka during the northeast monsoon in 2005 Seasonal and annual variations of K 490 along the LNG carrier s routes are also discussed in order to implement an early routing system for suitable ballast water exchangeable seas

  15. Bering Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Much of the Bering Sea is clear in this SeaWiFS image. The large expanse of bright aquamarine water is clearly visible. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  16. Bering Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The skies of the Bering Sea were relatively clear again in this SeaWiFS image showing a band of aquamarine colored water. Credit: Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

  17. Timing of uplift peripheral to the Red Sea, Saudi Arabia

    USGS Publications Warehouse

    Naeser, C.W.; Zimmermann, R.A.; Bohannon, R.G.; Schmidt, D.L.

    1990-01-01

    A Prominent escarpment is found along the western margin of the Arabian Shield. Elevations along this escarpment are up to 3200 m above the Red Sea. Between the Red Sea and the crest of the escarpment is a relatively featureless coastal plane that is ??? 50 km across. The coastal plane abruptly gives way to the steep mountainous terrain, the elevation of which increases abruptly towards the high crest. The elevation slowly decreases to the east of the high crest. Forty-four apatite fission-track ages have been determined on rocks from the Proterozoic Arabian Shield in southwestern Saudi Arabia. These ages range from 13.8 to 568 Ma. In general, the youngest ages are found at low elevations along the base of the escarpment near the eastern edge of the coastal plane. The oldest ages are from along and to the east of the crest. The fission-track data from Saudi Arabia show that there was a period of minor uplift and cooling during the Cretaceous. This was followed by a relatively stable period which lasted until the Mid to Upper Miocene. The latest uplift and erosion began slightly younger than 13.8 Ma. This latest episode resulted in a minimum uplift of 3 km and is related to the Red Sea Rift. Samples totally annealed prior to this latest episode of uplift and cooling have not yet reached the surface.

  18. 250 years of SW Indian Monsoon Variability from Red Sea Corals

    NASA Astrophysics Data System (ADS)

    Bryan, S.; Hughen, K. A.; Karnauskas, K. B.; Farrar, J. T.

    2015-12-01

    During the northern hemisphere summer, strong dust storms develop in the Tokar Delta region of Sudan. These massive dust storms are funneled through a gap in the coastal mountains and blow out across the Red Sea. The generation and transport of these dust storms is driven by the large-scale atmospheric pressure gradient across the Red Sea, which is a component of the Southwest Indian Monsoon. Dust deposited on the Red Sea is recorded in skeletal geochemistry of corals that live on the Saudi Arabian coast, and provides an opportunity to reconstruct variability in the monsoon system prior to instrumental records. We have generated annually-resolved records of coral Ba/Ca, which display strong correlations to the zonal pressure gradient across the Red Sea during the instrumental period. Our coral-based monsoon records show an increasing trend in the strength of SW Indian Monsoon circulation since the Little Ice Age, in agreement with lower-resolution Arabian Sea upwelling based records. Our records also show strong decadal-scale variability, which was strongest during the late 19th century and has declined during the past century. In this presentation, we will discuss the decadal-scale variability in the SW Indian Monsoon circulation over the past 250 years as revealed by Red Sea Corals and the implications of the relationships and trends observed in this study for projections of future monsoon variability.

  19. Quaternary climate change on the northern margins of Saharo-Arabian Desert with possible impact on human evolution, evidence from Negev Desert speleothems, Israel

    NASA Astrophysics Data System (ADS)

    Vaks, A.; Bar-Matthews, M.; Ayalon, A.; Matthews, A.; Halicz, L.; Frumkin, A.

    2006-12-01

    The Saharo-Arabian Desert belt is the largest and driest desert in the world and its margins are vulnerable to climatic change. The paleoclimate of the northern margins of Saharo-Arabian Desert is not yet fully understood, and it is the subject of our study. The Negev Desert, southern Israel, located in the northern part of the Saharo-Arabian Desert is ideal for paleoclimate research, because of its very steep north-south precipitation gradient and numerous caves rich with carbonate cave deposits (speleothems). Speleothems grow only when precipitation is high enough to enable meteoric water to reach the caves. No present day speleothem deposition occurs in the Negev Desert. The aims of the study were: timing of the humid periods by U-Th dating of the speleothem deposition periods; origin of the rainfall by speleothem δ18O and fluid inclusions δ2H; correlations between local and global climate changes and between the climate changes to out of Africa dispersals of Early Modern Humans (EMH). Speleothems were collected from 7 caves located on the north-south transect of the Negev Desert, between 300 mm to 30 mm isohyets. Whereas in the Mediterranean climate zone (>350 mm) of central and northern Israel the speleothem deposition was continuous, in the Negev Desert periods of speleothem deposition alternated with multiple hiatuses. In the mildly arid transition zone of northern Negev (300 to 150 mm) speleothem deposition occurred most of the time during the last 210 ka, with hiatuses at 150-144 ka, ~140 ka, 117-96 ka, 93-85 ka, 25- 23 ka, and 14-0 ka. In present-day arid and hyper-arid zone of central and southern Negev (150 to 30 mm) no speleothem deposition occurred most of the last 350 ka, with humid intervals at 350-290 ka, 220-190 ka, 137- 110 ka, and ~85 ka. The origin of the precipitation in the Negev Desert during these intervals was from Eastern Mediterranean Sea, i. e. mid-latitude cyclones (as present day). The latter conclusion is based on three evidences

  20. From Traditional to Formal Education in the Lower Arabian Gulf, 1820-1971

    ERIC Educational Resources Information Center

    Davidson, Christopher M.

    2008-01-01

    This article charts the development of education in the lower Arabian Gulf from its traditional beginnings in the nineteenth century to the provision of more formal schooling and eventually a ministry of education following Britain's withdrawal from the region in 1971. In order to provide a better understanding of the complexities and relative…

  1. Selective brain cooling in Arabian oryx (Oryx leucoryx): a physiological mechanism for coping with aridity?

    PubMed

    Hetem, Robyn S; Strauss, W Maartin; Fick, Linda G; Maloney, Shane K; Meyer, Leith C R; Fuller, Andrea; Shobrak, Mohammed; Mitchell, Duncan

    2012-11-15

    Selective brain cooling is a thermoregulatory effector proposed to conserve body water and, as such, may help artiodactyls cope with aridity. We measured brain and carotid blood temperature, using implanted data loggers, in five Arabian oryx (Oryx leucoryx) in the desert of Saudi Arabia. On average, brain temperature was 0.24±0.05°C lower than carotid blood temperature for four oryx in April. Selective brain cooling was enhanced in our Arabian oryx compared with another species from the same genus (gemsbok Oryx gazella gazella) exposed to similar ambient temperatures but less aridity. Arabian oryx displayed a lower threshold (37.8±0.1°C vs 39.8±0.4°C), a higher frequency (87±6% vs 15±15%) and a higher maximum magnitude (1.2±0.2°C vs 0.5±0.3°C) of selective brain cooling than did gemsbok. The dominant male oryx displayed less selective brain cooling than did any of the other oryx, but selective brain cooling was enhanced in this oryx as conditions became hotter and drier. Enhanced selective brain cooling in Arabian oryx supports the hypothesis that selective brain cooling would bestow survival advantages for artiodactyl species inhabiting hot hyper-arid environments. PMID:22899527

  2. Tectonic controls on the stratigraphic architecture and hydrocarbons systems of the Arabian Plate

    SciTech Connect

    Grabowski, G.J. Jr.; Norton, I.O.

    1995-12-31

    Arabian Platform sediments consist of major sequences separated by tectonically controlled unconformities. These tectonic events, at the plate margins, controlled the orientation and distribution of sedimentary facies on the stable platform. Eustacy and subsidence were the principle controls on the actual facies that formed.

  3. Saharan and Arabian Dust Aerosols: A Comparative Case Study of Lidar Ratio

    NASA Astrophysics Data System (ADS)

    Córdoba-Jabonero, Carmen; Sabbah, Ismail; Sorribas, Mar; Adame, José Antonio; Cuevas, Emilio; Sharifi, Faisal Al; Gil-Ojeda, Manuel

    2016-06-01

    This work presents a first comparative study of the Lidar Ratio (LR) values obtained for dust particles in two singular dust-influenced regions: the Canary Islands (Spain, close to the African coast in the North Atlantic Ocean), frequently affected by Saharan dust intrusions, and the Kuwait area (Arabian Peninsula) as usually influenced by Arabian dust storms. Synergetic lidar and sun-photometry measurements are carried out in two stations located in these particular regions for that purpose. Several dusty cases were observed during 2014 in both stations and, just for illustration, two specific dusty case studies have been selected and analyzed to be shown in this work. In general, mean LR values of 54 sr and 40 sr were obtained in these studies cases for Saharan and Arabian dust particles, respectively. Indeed, these results are in agreement with other studies performed for dust particles arriving from similar desert areas. In particular, the disparity found in Saharan and Arabian dust LR values can be based on the singular composition of the suspended dust aerosols over each station. These results can be useful for CALIPSO extinction retrievals, where a single LR value (40 sr) is assumed for pure dust particles independently on the dust source region.

  4. Kunjin flaviviral encephalomyelitis in an Arabian gelding in New South Wales, Australia.

    PubMed

    Tee, S Y; Horadagoda, N; Mogg, T D

    2012-08-01

    Flaviviruses, including Kunjin virus, are arboviruses that cause encephalomyelitis in humans and horses. This case report describes an Arabian gelding exhibiting neurological signs of flavivirus encephalomyelitis, the diagnostic investigation and confirmation of an unreported case of Kunjin virus equine encephalomyelitis in Australia. PMID:22827627

  5. Ileal impaction and jejunal enterotomy in a 4-month-old Arabian filly.

    PubMed

    Davis, Heather A; Munsterman, Amelia

    2012-01-01

    A 4-month-old Arabian filly was treated by surgical correction of an ileal impaction. The impaction was resolved through a distal jejunal enterotomy. One-year follow-up showed no post-operative complications secondary to the enterotomy. Jejunal enterotomy may be a surgical option for resolution of an ileal impaction. PMID:22753967

  6. Bioinformatics in Middle East Program Curricula--A Focus on the Arabian Gulf

    ERIC Educational Resources Information Center

    Loucif, Samia

    2014-01-01

    The purpose of this paper is to investigate the inclusion of bioinformatics in program curricula in the Middle East, focusing on educational institutions in the Arabian Gulf. Bioinformatics is a multidisciplinary field which has emerged in response to the need for efficient data storage and retrieval, and accurate and fast computational and…

  7. New initiatives for managment of red palm weevil threats to historical Arabian date palms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The date palm is an important part of the religious, cultural, and economic heritage of the Arabian Peninsula. This heritage is threatened by the recent invasion of the red palm weevil(RPW) from Southeast Asia. In Saudi Arabia, a national campaign for control of RPW by containment/destruction of inf...

  8. Reproductive Performance of Arabian and Thoroughbred Mares under Subtropical Conditions of Pakistan

    PubMed Central

    Warriach, H. M.; Memon, M. A.; Ahmad, N.; Norman, S. T.; Ghafar, A.; Arif, M.

    2014-01-01

    Breeding records of 57 Arabian and 66 Thoroughbred mares were analysed to assess their reproductive performance under the subtropical conditions of Pakistan. The Arabian mares showed significantly higher conception rates (p<0.05) in second mated oestrus and foal heat mated oestrus compared to Thoroughbred mares. However, conception rates for first lifetime mated oestrus were similar in both breeds of mares. Age at first mating (1,301±40 vs 1,500±32 days) was significantly (p<0.05) less in Arabian compared to Thoroughbred mares. Both breeds of mares showed significantly (p<0.05) higher frequencies of oestrous cycles and conception rates during the winter (October to March) compared to summer (June to August) months. Age of mares affected the conception rates, as mares at ages 3 to 7 and 8 to 12 years of ages had significantly higher conception rates (p<0.05) than those ≥18 years old in both breeds. This study demonstrates that i) reproductive performance in Arabians is better than Thoroughbred mares under the subtropical conditions of Pakistan, ii) mares remain cyclic throughout the year and iii) conception rates were higher in mares bred during winter compared to summer months. PMID:25050033

  9. Biological data from a data-deficient shark: the Arabian smoothhound Mustelus mosis (Carcharhiniformes: Triakidae).

    PubMed

    Moore, A B M; Henderson, A C; Farrell, E D; Weekes, L B

    2016-06-01

    The present study provides information on length distribution, reproductive biology and diet of Mustelus mosis based on individuals caught in waters off the eastern Arabian Peninsula. Although ageing of vertebral centra was attempted, band pairs were of low clarity and counts could not be confidently assigned. PMID:27245625

  10. Factors Influencing the Use of Learning Management System in Saudi Arabian Higher Education: A Theoretical Framework

    ERIC Educational Resources Information Center

    Asiri, Mohammed J. Sherbib; Mahmud, Rosnaini bt; Bakar, Kamariah Abu; Ayub, Ahmad Fauzi bin Mohd

    2012-01-01

    The purpose of this paper is to present the theoretical framework underlying a research on factors that influence utilization of the Jusur Learning Management System (Jusur LMS) in Saudi Arabian public universities. Development of the theoretical framework was done based on library research approach. Initially, the existing literature relevant to…

  11. Molecular Assay and Genotyping of Hepatitis C Virus among Infected Egyptian and Saudi Arabian Patients

    PubMed Central

    Farag, Mohamed MS; Sofy, Ahmed R; Mousa, Adel A; Ahmed, Mohamed A; Alganzory, Mohamed R

    2015-01-01

    Hepatitis C virus (HCV) infection is a major health problem recognized globally. HCV is a common cause of liver fibrosis that may lead to liver cirrhosis or hepatocellular carcinoma. The aim of this study was to estimate the prevalence of HCV infection and genotyping among Egyptian and Saudi Arabian chronic patients using different molecular techniques. HCV RNA viral load was assessed by real-time polymerase chain reaction (RT-PCR) technology. For HCV genotyping, RT-PCR hybridization fluorescence-based method and reverse hybridization line probe assay (INNO-LiPA) were used. A total of 40 anti-HCV-positive patients with chronic hepatitis C were examined for HCV RNA, genotyping, and different laboratory investigations. In the present study, HCV genotypes 4, mixed 4.1b, and 1 were detected in patients of both countries, while genotype 2 was only detected in Saudi Arabian patients. Genotyping methods for HCV showed no difference in the classification at the genotype level. With regard to HCV subtypes, INNO-LiPA assay was a reliable test in HCV genotyping for the detection of major genotypes and subtypes, while RT-PCR-based assay was a good test at the genotype level only. HCV genotype 4 was found to be the predominant genotype among Egyptian and Saudi Arabian chronic patients. In conclusion, data analysis for detecting and genotyping HCV was an important factor for understanding the epidemiology and treatment strategies of HCV among Egyptian and Saudi Arabian chronic patients. PMID:26512201

  12. Ileal impaction and jejunal enterotomy in a 4-month-old Arabian filly

    PubMed Central

    Davis, Heather A.; Munsterman, Amelia

    2012-01-01

    A 4-month-old Arabian filly was treated by surgical correction of an ileal impaction. The impaction was resolved through a distal jejunal enterotomy. One-year follow-up showed no post-operative complications secondary to the enterotomy. Jejunal enterotomy may be a surgical option for resolution of an ileal impaction. PMID:22753967

  13. Origins of wind-driven intraseasonal sea level variations in the North Indian Ocean coastal waveguide

    NASA Astrophysics Data System (ADS)

    Suresh, I.; Vialard, J.; Lengaigne, M.; Han, W.; McCreary, J.; Durand, F.; Muraleedharan, P. M.

    2013-11-01

    this paper, we show that a linear, continuously stratified ocean model reproduces observed wind-driven intraseasonal sea level variability in the coastal waveguide of the Northern Indian Ocean (NIO). Sensitivity experiments with intraseasonal wind forcing selectively applied in the equatorial region, Bay of Bengal, and Arabian Sea show that a large part of the basin-scale sea level variations are driven by zonal wind fluctuations along the equator. Within the NIO coastal waveguide, the contribution of remote equatorial forcing decreases from ~80-90% in the Andaman Sea to ~50% northeast of Sri Lanka and then increases to ~60-70% along the west coast of India. During the southwest monsoon, intraseasonal wind variations become stronger over the NIO, resulting in a larger contribution of local wind forcing to sea level variability along the west (up to 60%) and east (up to 40%) coasts of India.

  14. Assessment of the Climate Vulnerabilities of the Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Alharbi, T.; Sultan, M.; Ahmed, M.; Chouinard, K.

    2014-12-01

    The Arabian Peninsula (AP), like many places around the world, is apparently witnessing the impacts (amount, patterns, and frequency of precipitation) of global warming. Precipitation over the AP is largely controlled by two main wind regimes, the winter (October to March) northerlies or northwesterlies, hereafter referred to as westerlies, and the summer (April to September) monsoonal wind regimes. The global monthly Climate Prediction Centers (CPC) Merged Analysis of Precipitation (CMAP) data (spatial resolution: 2.5° × 2.5°; temporal resolution: monthly; operational period: January 1979 to November 2011) was used to investigate the nature and magnitude of precipitation variations over the AP throughout 1979 - 2010. Trends in CMAP-derived precipitation patterns were examined over the winter and summer seasons throughout Periods I (1979-1995) and II (1996-2010). Reversals in precipitation patterns were observed in Periods I and II, where areas witnessing an increase in precipitation in Period I showed a decrease in precipitation throughout Period II, and vice versa for the remaining areas. Our findings suggest: (1) an increase in precipitation during Period I over the southeastern and southwestern coastal areas of AP (e.g., Muscat, Sanaa, and Jeddah) that is probably related to the intensification of the monsoons at the expense of the westerlies, (2) an increase in precipitation during Period II over the northwestern and southeastern of AP (e.g., northwestern Saudi Arabia, Empty Quarter, western and southwestern Oman, and eastern Yemen) is here attributed to intensification of the westerlies, and 3) the general similarity of annual trend patterns to the summer trend (Period I) and to winter trend (Period II) suggest that the annual trends are largely controlled by monsoonal wind regimes in Period I and by the westerlies in Period II. Outputs (i.e., precipitation) of climatic models (CCSM4.0) over the AP are being extracted (for upcoming 100 years) , downscaled

  15. Recent observed climate change over the Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Alsarmi, Said; Washington, Richard

    2011-06-01

    We have examined trends in temperature and precipitation parameters for the Arabian Peninsula (AP) during the last 2 to 3 decades. The data set has been carefully quality controlled and checked for homogeneity. Although of low density (21 stations) and relatively short time period, a clear picture of climate change in the region has emerged. The general pattern of the AP mean annual temperature trend is one of warming, with 14 of 21 stations show statistically significant warming at 0.05 level and most at 0.001 level and only one (Seeb) showing statistically significant cooling. The highest statistically significant mean annual warming trends are found in Oman (Sur = 1.03°C decade-1) and Emirates (Dubai = 0.81°C decade-1). The season of maximum warming in mean temperature is March to April. The highest monthly mean temperature trend in the AP occurs in Sur in May (1.47°C decade-1). There is a broad statistically significant increase in mean annual maximum temperature in AP in 12 out of 21 stations, with the highest trends in central and eastern/southeastern AP. Only SW AP and the Gulf of Oman do not show warming. The highest monthly maximum temperature trend in the AP occurs in Bahrain in March (2.27°C decade-1). The second highest significant warming trends are reported in Doha in February (1.54°C decade-1). For minimum temperature, 16 out of 21 stations show statistically significant warming trends, with the highest annual trends observed in the Emirates (Dubai = 1.24°C decade-1), northwest Oman (Sohar = 1.17°C decade-1) and Qatar (Doha = 1.13°C decade-1). The highest monthly minimum temperature warming rate occurred in October. Both Dubai and Kuwait reported the highest significant rate of 2.00°C decade-1. The general mean annual diurnal temperature range trend is negative in the AP, with six out of 21 stations show statistically significant negative trends while three stations show statistically significant positive trends. Trends in mean annual

  16. High-Resolution Physical-Biological Surveys in the Red Sea

    NASA Astrophysics Data System (ADS)

    Hodges, B. A.; Fratantoni, D. M.; Lund, J. M.; Davis, C. S.; Idrisi, N.; Bahr, F.; Kirincich, A. R.; Petrik, C. M.; Eaton, J. A.; Woods, N. W.

    2008-12-01

    The Red Sea is a unique oceanic environment whose fringing coral reefs support a diverse coastal ecosystem. The coastal circulation driving the exchange of biota between the reef environment and the open Red Sea is strongly influenced by complex bathymetry and is largely undescribed due to a scarcity of oceanographic observations. Here, we present preliminary results from a recent survey cruise along the Saudi Arabian coast near Jeddah. High-resolution hydrographic and optical measurements obtained with a robotic undulating towfish are used to characterize physical and biological variability on time scales of days and spatial scales of 1-10 km.

  17. Red-Sea rift magmatism near Al Lith, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Pallister, J.S.

    1986-01-01

    A model of poly-baric mantle-melt derivation, producing several alkalinesubalkaline cycles, best explains magmatism in the Red Sea region. Differences in the depths and dynamics of mantle-melt extraction and transport brought about through changes in crust and mantle structure as the rift and paar developed may account for the transition from mixed alkaline-subalkaline bimodal magmatism of the pre-20 Ma rift basin to exclusively subalkaline (tholeiitic) magmatism at the Red Sea spreading axis and to predominantly alkali basalt volcanism within the Arabian Shield.

  18. Isostatic Model and Isostatic Gravity Anomalies of the Arabian Plate and Surroundings

    NASA Astrophysics Data System (ADS)

    Kaban, Mikhail K.; El Khrepy, Sami; Al-Arifi, Nassir

    2016-04-01

    The isostatic modeling represents one of the most useful "geological" reduction methods of the gravity field. With the isostatic correction, it is possible to remove a significant part of the effect of deep density heterogeneity, which dominates in the Bouguer gravity anomalies. Although there exist several isostatic compensation schemes, it is usually supposed that a choice of the model is not an important factor to first order, since the total weight of compensating masses remains the same. We compare two alternative models for the Arabian plate and surrounding area. The Airy model gives very significant regional isostatic anomalies, which cannot be explained by the upper crust structure or disturbances of the isostatic equilibrium. Also, the predicted "isostatic" Moho is very different from existing seismic observations. The second isostatic model includes the Moho, which is based on seismic determinations. Additional compensation is provided by density variations within the lithosphere (chiefly in the upper mantle). According to this model, the upper mantle under the Arabian Shield is less dense than under the Platform. In the Arabian platform, the maximum density coincides with the Rub' al Khali, one of the richest oil basin in the world. This finding agrees with previous studies, showing that such basins are often underlain by dense mantle, possibly related to an eclogite layer that has caused their subsidence. The mantle density variations might be also a result of variations of the lithosphere thickness. With the combined isostatic model, it is possible to minimize regional anomalies over the Arabian plate. The residual local anomalies correspond well to tectonic structure of the plate. Still very significant anomalies, showing isostatic disturbances of the lithosphere, are associated with the Zagros fold belt, the collision zone of the Arabian and Eurasian plates.

  19. Nd, Pb, Sr, and O isotopic characterization of Saudi Arabian Shield terranes

    USGS Publications Warehouse

    Stoeser, D.B.; Frost, C.D.

    2006-01-01

    New Nd, Sr and O isotopic data for granitoid rocks of the Saudi Arabian Shield are presented together with published Nd, Pb, Sr and O isotopic data and all available geologic and geochronologic information to re-evaluate the terranes defined for the Saudi Arabian part of the Arabian-Nubian Shield. Three groups of terranes are identified: 1) the western arc terranes, 2) the eastern arc terranes, and 3) the Khida terrane. The Khida terrane is the only terrane composed of pre-Neoproterozoic continental crust. The western arc terranes are of oceanic arc affinity, and have the least radiogenic Pb and Sr and most radiogenic Nd isotopic compositions and some of the lowest ??18O values of any rocks of the Saudi Arabian Shield. Although some previous studies have characterized the eastern arc terranes as of continental affinity, this study shows that they too are composed of Neoproterozoic oceanic arcs, although their sources have slightly elevated 208Pb/204Pb, Nd, Sri, and ??18O values compared to the western arc terranes. These data suggest that either the isotopic composition of the mantle source for the western arc terranes is more depleted than that of the eastern arc terranes or the eastern arc terranes have been mixed with a small amount of cratonic source material, or both. We further elaborate on the Hulayfah-Ad Dafinah fault zone as a major boundary within the Saudi Arabian portion of the East African Orogen. With further study, its northern extension may be shown to pass through what has been defined as the Hail terrane, and its southern extension appears to lie under cover east of the Tathlith-Malahah terrane and extend into Yemen. It may represent the collision zone between East and West Gondwana, and at the very least it is an important suture between groups of arc terranes of contrasting isotopic composition caught between two converging continents.

  20. Accelerated subsidence and sedimentation in the Levant Basin during the Late Tertiary and concurrent uplift of the Arabian platform: Tectonic versus counteracting sedimentary loading effects

    NASA Astrophysics Data System (ADS)

    Bar, Oded; Gvirtzman, Zohar; Feinstein, Shimon; Zilberman, Ezra

    2013-06-01

    Since the Middle Eocene, the northwest Arabian Platform has been emerging from the water and rising above sea level, whereas the adjacent Levant Basin has been subsiding and accumulating a thick sedimentary section. This study investigates these opposing vertical motions and the relative roles of tectonic-driven versus isostatic adjustment forces involved. Such a distinction is strongly dependent on a reliable estimation of the paleobathymetry, which in pelagic environments may vary substantially. We use two different methods to estimate the paleo-water-depth in the deep Levant Basin in the Tertiary time. Isostatic balancing calculations with the adjacent inland region are employed to estimate the paleo-water-depth in the deep Levant Basin in the Middle Eocene, just before the commencement of the Late Tertiary tectonic phase. For later periods, we use morpho-structural elements such as abrasion surfaces and incised canyons to build laterally changing topo-bathymetry profiles. Our results indicate that in the Mid-Eocene water depth in the deep Levant Basin was 2-3.5 km, which gradually decreased to 1.5 km today. Based on these results, our analysis shows that the enhanced subsidence of the Levant Basin reflects an isostatic response to sedimentary filling of a pre-existing deep-water basin with no involvement of a downward tectonic force. On the contrary, we suggest that the regional tectonic force was upward, counteracting a sedimentary loading effect. Further regional implication of this understanding is that the cause for uplifting and exposure of the NW Arabian Platform in the Late Tertiary extended far westward beyond the inland region.

  1. Neoproterozoic Structural Evolution of the NE-trending 620-540 Ma Ad-Damm Shear Zone, Arabian Shield, Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Hamimi, Z.; El-Sawy, E. K.; El-Fakharan, A. S.; Shujoon, A.; Matsah, M.; El-Shafei, M.

    2012-04-01

    Ad-Damm Shear Zone (ASZ) is a NE-trending fault zone separating Jeddah and Asir tectonostratigraphic terranes in the Neoproterozoic juvenile Arabian Shield. ASZ extends ~380 km, with an average width ~2-3 km, from the eye-catching Ruwah Fault Zone in the eastern shield to the Red Sea Coastal plain. It was believed to be one of the conjugate shears of the NW- to NNW- trending sinistral Najd Shear System based on noteworthy dextral shear criteria recorded within the 620 Ma sheared granites of Numan Complex, as well as right-lateral offsets within quartz veins and dikes transected by the shear zone. The present study is an integrated field-based structural analysis and remote sensing. We utilized the ASTER data for lithologic discrimination and automatic structural lineament extraction and analysis of the Neoproterozoic basement lithologies encountered along and within the vicinity of ASZ. Various false color composite images were generated and evaluated for lithological mapping and structural lineaments. The obtained map was analyzed using GIS techniques to interpret the behavior of the existing lineaments and their spatial distribution. Based on the results of the ASTER data, two significant areas; around Bir Ad-Damm and to the south of Wadi Numan, are selected for detailed field investigation. Shear-sense indicators and overprinting relations clearly show a complicated Neoproterozoic history of ASZ, involving at least three deformations: (1) an early attenuated NE-SW sinistral shearing; followed by (2) a SE-directed thrusting phase resulted in the formation SE-verging thrusts and associated thrust-related folds; and (3) late NE-SW intensive dextral transcurrent shearing played a significant role in the creation of mesoscopic shear-zone related folds, particularly in the area near Bir Ad-Damm. Such deformation history demonstrates the same episode of Neoproterozoic deformation exhibited in the NE-trending shear zones in the Arabian-Nubian Shield (ANS).

  2. Vanadium and nickel content of Nowruz spill tar flakes on the Saudi Arabian coastline and their probable environmental impact

    SciTech Connect

    Sadiq, M.; Zaidi, T.H.

    1984-06-01

    The Arabian Gulf is experiencing the worst oil spill in its history. The spill originates from two war damaged Iranian oil wells in the Nowruz oil field. Much of the oil is entering Saudi Arabian waters and washes ashore in the form of tar like flakes. In late March and early April 1983, fish, snake, turtle, and bird kills of different magnitude were noted along the Saudi Arabian coastline. In the early days of the spill Saudi Arabian authorities suspected sources other than the Nowruz spill to be causing the kills. Research was initiated to identify the origin of tar like flakes, their environmental impact and the cause of fish, snake, turtle and bird kills. This paper discusses some of the results of this research.

  3. Extreme precipitation events in the Middle East: Dynamics of the Active Red Sea Trough

    NASA Astrophysics Data System (ADS)

    Vries, A. J.; Tyrlis, E.; Edry, D.; Krichak, S. O.; Steil, B.; Lelieveld, J.

    2013-07-01

    The Active Red Sea Trough (ARST) is an infrequent weather phenomenon that is associated with extreme precipitation, flash floods, and severe societal impacts in the Middle East (ME). Using reanalysis (ERA-Interim) and observational precipitation (Aphrodite and stations) data, we investigate its underlying dynamics, geographical extent, and seasonality. Twelve ARST events affecting the Levant have the same dynamical characteristics as those associated with a major flood in Jeddah (Saudi Arabia) on 25 November 2009. Hence, the Jeddah flooding was caused by an ARST, which implies that ARSTs can affect a much larger part of the ME than previously assumed. We present an ARST concept involving six dynamical factors: (1) a low-level trough; the Red Sea Trough (RST), (2) an anticyclone over the Arabian Peninsula; the Arabian Anticyclone (AA), (3) a transient midlatitude upper trough, (4) an intensified subtropical jet stream, (5) moisture transport pathways, and (6) strong ascent resulting from tropospheric instability and the synoptic-scale dynamical forcing. We explain the ARST as the interaction of a persistent stationary wave in the tropical easterlies (i.e., the RST) with a superimposed amplifying Rossby wave, resulting in northward propagating moist air masses over the Red Sea. Our findings emphasize the relevance of the AA, causing moisture transport from the Arabian and Red Seas. The particular topography in the Red Sea region and associated low-level circulation makes the ARST unique among tropical-extratropical interactions. The ARST seasonality is explained by the large-scale circulation and in particular the seasonal cycle of the semipermanent quasi-stationary RST and AA.

  4. Maternal phylogenetic relationships and genetic variation among Arabian horse populations using whole mitochondrial DNA D-loop sequencing

    PubMed Central

    2013-01-01

    Background Maternal inheritance is an essential point in Arabian horse population genetics and strains classification. The mitochondrial DNA (mtDNA) sequencing is a highly informative tool to investigate maternal lineages. We sequenced the whole mtDNA D-loop of 251 Arabian horses to study the genetic diversity and phylogenetic relationships of Arabian populations and to examine the traditional strain classification system that depends on maternal family lines using native Arabian horses from the Middle East. Results The variability in the upstream region of the D-loop revealed additional differences among the haplotypes that had identical sequences in the hypervariable region 1 (HVR1). While the American-Arabians showed relatively low diversity, the Syrian population was the most variable and contained a very rare and old haplogroup. The Middle Eastern horses had major genetic contributions to the Western horses and there was no clear pattern of differentiation among all tested populations. Our results also showed that several individuals from different strains shared a single haplotype, and individuals from a single strain were represented in clearly separated haplogroups. Conclusions The whole mtDNA D-loop sequence was more powerful for analysis of the maternal genetic diversity in the Arabian horses than using just the HVR1. Native populations from the Middle East, such as Syrians, could be suggested as a hot spot of genetic diversity and may help in understanding the evolution history of the Arabian horse breed. Most importantly, there was no evidence that the Arabian horse breed has clear subdivisions depending on the traditional maternal based strain classification system. PMID:24034565

  5. Coastal sea level response to the tropical cyclonic forcing in the northern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Mehra, P.; Soumya, M.; Vethamony, P.; Vijaykumar, K.; Balakrishnan Nair, T. M.; Agarvadekar, Y.; Jyoti, K.; Sudheesh, K.; Luis, R.; Lobo, S.; Harmalkar, B.

    2015-02-01

    The study examines the observed storm-generated sea level variation due to deep depression (event 1: E1) in the Arabian Sea from 26 November to 1 December 2011 and a cyclonic storm "THANE" (event 2: E2) over the Bay of Bengal during 25-31 December 2011. The sea level and surface meteorological measurements collected during these extreme events exhibit strong synoptic disturbances leading to storm surges of up to 43 cm on the west coast and 29 cm on the east coast of India due to E1 and E2. E1 generated sea level oscillations at the measuring stations on the west coast (Ratnagiri, Verem and Karwar) and east coast (Mandapam and Tuticorin) of India with significant energy bands centred at periods of 92, 43 and 23 min. The storm surge is a well-defined peak with a half-amplitude width of 20, 28 and 26 h at Ratnagiri, Verem and Karwar, respectively. However, on the east coast, the sea level oscillations during Thane were similar to those during calm period except for more energy in bands centred at periods of ~ 100, 42 and 24 min at Gopalpur, Gangavaram and Kakinada, respectively. The residual sea levels from tide gauge stations in Arabian Sea have been identified as Kelvin-type surges propagating northwards at a speed of ~ 6.5 m s-1 with a surge peak of almost constant amplitude. Multi-linear regression analysis shows that the local surface meteorological data (daily mean wind and atmospheric pressure) is able to account for ~ 57 and ~ 69% of daily mean sea level variability along the east and west coasts of India. The remaining part of the variability observed in the sea level may be attributed to local coastal currents and remote forcing.

  6. Suspected myofibrillar myopathy in Arabian horses with a history of exertional rhabdomyolysis

    PubMed Central

    VALBERG, S. J.; McKENZIE, E. C.; EYRICH, L. V.; SHIVERS, J.; BARNES, N. E.; FINNO, C. J.

    2016-01-01

    Summary Reasons for performing study Although exertional rhabdomyolysis (ER) is common in Arabian horses, there are no dedicated studies describing histopathological characteristics of muscle from Arabian horses with ER. Objectives To prospectively identify distinctive histopathological features of muscle from Arabian endurance horses with a history of ER (pro-ER) and to retrospectively determine their prevalence in archived samples from Arabian horses with exertional myopathies (retro-ER). Study design Prospective and retrospective histopathological description. Methods Middle gluteal muscle biopsies obtained from Arabian controls (n = 14), pro-ER (n = 13) as well as archived retro-ER (n = 25) muscle samples previously classified with type 2 polysaccharide storage myopathy (15/25), recurrent exertional rhabdomyolysis (7/25) and no pathology (3/25) were scored for histopathology and immunohistochemical staining of cytoskeletal proteins. Glutaraldehyde-fixed samples (2 pro-ER, one control) were processed for electron microscopy. Pro-ER and retro-ER groups were compared with controls using Mann–Whitney U and Fisher's exact tests. Results Centrally located myonuclei in mature myofibres were found in significantly more (P<0.05) pro-ER (12/13) and retro-ER (21/25) horses than controls (4/14). Degenerating myofibres were not evident in any biopsies. Retro-ER horses had amylase-resistant polysaccharide (6/25, P<0.05) and higher scores for cytoplasmic glycogen, rimmed vacuoles and rod-like bodies. A few control horses (3/14) and significantly (P<0.05) more pro-ER (12/13) and retro-ER (18/25) horses had disrupted myofibrillar alignment and large desmin and αβ-crystallin positive cytoplasmic aggregates. Prominent Z-disc degeneration and focal myofibrillar disruption with regional accumulation of β-glycogen particles were identified on electron microscopy of the 2 pro-ER samples. Conclusions In a subset of Arabian horses with intermittent episodes of exertional

  7. Evidence of buried paleodrainage in the Wahiba Sands, Oman: New perspective in understanding paleorecharge in the Southern Arabian Peninsula

    NASA Astrophysics Data System (ADS)

    Normand, J.; Heggy, E.; Rouchdi, M.; Scabbia, G.; Al-Maktoumi, A.; Avouac, J. P.

    2015-12-01

    The dynamic of the monsoon and position of its Intertropical Convergence Zone, as well as global sea level fluctuation are associated and have controlled the paleoclimate of the Wahiba Sands in Oman (Radies et al., 2004). Today the climate of the area is considered as hyper-arid but has also known wetter periods in the past, e.g. Early Holocene, and the paleodrainage mapped in the highland areas around the desert of Wahiba Sands by Robinson et al. 2007, using Radarsat-1 C-band SAR images, are supporting evidences of substantial surficial flows events. However, no drainage networks were detected under the Wahiba desert itself, which motivated our study to explore the area with a lower radar frequency to penetrate deeper into the desiccated dunes. Using ALOS PALSAR L-band radar SAR images, we observe NW-SE and NE-SW oriented paleochannels, under meters to few tens of meters of the linear dunes forming the Wahiba Sands area. The paleochannels are detectable with the loss of radar backscatter that we attribute to different sedimentary materials and their permittivity, porosity and scattering properties. To validate their detection, we perform a 500 MHz ground radar (GPR) survey in the interdunal area and observe them to be few tens of meters wide and about 1m deep. The scattering observed on the radargrams suggests these paleochannels to be filled with centimetric size gravels, which we believe cause the signal attenuation observed on the SAR images. Dunes are found to be highly favorable for the L-band penetration, with power loss of 0.2 dB/m derived from dielectric characterizations of field collected samples. The discovery of these buried paleochannels under the linear dunes brings new insights to construct the paleoclimatic evolution of the southern area of the Arabian peninsula and better understand the indeterminate tropical climate changes during the Late Pleistocene and Holocene.

  8. The East Africa Oligocene intertrappean beds: Regional distribution, depositional environments and Afro/Arabian mammal dispersals

    NASA Astrophysics Data System (ADS)

    Abbate, Ernesto; Bruni, Piero; Ferretti, Marco Peter; Delmer, Cyrille; Laurenzi, Marinella Ada; Hagos, Miruts; Bedri, Omar; Rook, Lorenzo; Sagri, Mario; Libsekal, Yosief

    2014-11-01

    exceed thousands of square kilometers in only a single case (Mendefera), but were quite restricted in most cases. Their most likely endorheic and local character, together with a regional ill-defined fluvial network, was the effect of a water-course rerouting caused by the progressive rising of the eastern African and Arabian plateaux. Chronological constraints for the intertrappean beds can be inferred from the age of the hosting Trap succession and by the stratigraphical position that they occupy. Intervolcanic sedimentary episodes are typically found in the basaltic and subordinately rhyolitic successions that followed the 31-29 Ma old basaltic widespread paroxysm. With due caveats deriving from the discontinuous availability of datings specifically dedicated to this issue, we regard the age of the intertrappean beds as mostly encompassed in the interval from 29 to 27 Ma at the transition between the Early and Late Oligocene in the Ethiopia/Yemen Trap core. In marginal areas, such as SW Arabia, Eritrea and Kenya, the volcanic activity above the intertrappean beds resumed later, and its quiescence allowed a more prolonged period of sedimentation. The intertrappean beds fall in the second cooling event of the Oligocene climatic deterioration. During the contemporaneous apparent drop in the global sea-level and closure of the Tethyan Ocean between Arabia and southwestern Asia, connections were established between the African and the Eurasian continents. At that time, southwestern Asia was experiencing severe aridity with faunal exchanges toward the luxuriously vegetated eastern Africa.

  9. Modelling the Seasonal Overturning Circulation in the Red Sea

    NASA Astrophysics Data System (ADS)

    Yao, Fengchao; Hoteit, Ibrahim; Pratt, Larry; Bower, Amy; Koehl, Armin; Gopalakrishnan, Ganesh

    2015-04-01

    The overturning circulation in the Red Sea exhibits a distinct seasonally reversing pattern and is studied using 50-year, high-resolution MIT general circulation model simulations. The seasonal water exchange in the Strait of Bab el Mandeb is successfully simulated, and the structures of the intruding subsurface Gulf of Aden intermediate water are in good agreement with summer observations in 2011. The model results suggest that the summer overturning circulation is driven by the combined effect of the shoaling of the thermocline in the Gulf of Aden resulting from remote winds in the Arabian Sea and an upward surface slope from the Red Sea to the Gulf of Aden set up by local surface winds in the Red Sea. For the winter overturning circulation, the climatological model mean results suggest that the surface inflow intensifies in a western boundary current in the southern Red Sea that switches to an eastern boundary current north of 24°N. The overturning is accomplished through a cyclonic recirculation and a cross-basin overturning circulation in the northern Red Sea, with major sinking occurring along a narrow band of width about 20 km along the eastern boundary and weaker upwelling along the western boundary. The northward pressure gradient force, strong vertical mixing, and horizontal mixing near the boundary are the essential dynamical components in the model's winter overturning circulation.

  10. Blood phagocyte activity after race training sessions in Thoroughbred and Arabian horses.

    PubMed

    Cywinska, Anna; Szarska, Ewa; Degorski, Andrzej; Guzera, Maciej; Gorecka, Renata; Strzelec, Katarzyna; Kowalik, Sylwester; Schollenberger, Antoni; Winnicka, Anna

    2013-10-01

    Intensive exercise and exertion during competition promote many changes that may result in the impairment of immunity and increased susceptibility to infections. The aim of this study was to evaluate the activity of "the first line of defense": neutrophils and monocytes in racing Thoroughbred and Arabian horses after routine training sessions. Twenty-three (12 Thoroughbred and 11 Arabian) horses were examined. Routine haematological (number of red blood cells - RBC, haemoglobin concentration - HGB, haematocrit - HCT, total number of white blood cells - WBC), biochemical (creatine phosphokinase activity - CPK and total protein concentration - TP) parameters, cortisol concentration as well as phagocytic and oxidative burst activity of neutrophils and monocytes were determined. The values of basic parameters and the activity of phagocytes differed between breeds and distinct patterns of exercise-induced changes were observed. The training sessions did not produce the decrease in phagocyte activity that might lead to the suppression of immunity. PMID:23664016

  11. Depositional history of polychlorinated biphenyls in a dated sediment core from the northwestern Arabian Gulf.

    PubMed

    Gevao, Bondi; Aba, Abdul Aziz; Al-Ghadban, Abdul Nabi; Uddin, Saif

    2012-05-01

    The vertical distribution of polychlorinated biphenyls (PCBs) was measured in a dated sediment core from the northwestern Arabian Gulf to reconstruct their depositional history. The downcore profile showed an increase in concentrations from depth to a subsurface maximum of approximately 1,500 pg g(-1) in approximately 1991, followed by an exponential decrease to the sediment-water interface. Current concentrations of ΣPCBs are similar to levels predating the episodic input of PCBs in sediments dated coincident with the 1991 Arabian Gulf war. The spike in ΣPCB concentrations during the war may be related to the destruction of PCB-laden transformers during the conflict. The 15-fold decrease in ΣPCB concentrations from the period of maximum flux to prewar levels suggests that the factors delivering PCBs to sediments at present are similar to those that that existed before the war-related inputs. PMID:22218707

  12. Localized hyper saline waters in Arabian Gulf from desalination activity--an example from South Kuwait.

    PubMed

    Uddin, Saif; Al Ghadban, Abdul Nabi; Khabbaz, Ahmed

    2011-10-01

    Desalination is the only means of reliable water supply in most of the Arabian Gulf States including Kuwait, Saudi Arabia, Bahrain, Qatar, and United Arab Emirates. Huge desalination capacities are installed on the western margin of the Arabian Gulf contributing to increased salinity off the coast. This paper presents long term salinity observation made near outfall of Az Zour Power and Desalination Plant in South Kuwait. The salinity values peak at around 50 ppt at observation station located in open gulf around 5 km from the outfall of the power and desalination plant. The observation highlights the stress on the local marine environment continued incremental salinity can impair the marine biodiversity in the area. The study suggests that a stringent post construction and operational offshore water quality assessment can help in early detection of potentially complex environmental issues. PMID:21213041

  13. Fatal transmission of contagious caprine pleuropneumonia to an Arabian oryx (Oryx leucoryx).

    PubMed

    Chaber, A L; Lignereux, L; Al Qassimi, M; Saegerman, C; Manso-Silván, L; Dupuy, V; Thiaucourt, F

    2014-09-17

    Contagious caprine pleuropneumonia (CCPP) is an infectious respiratory disease mainly affecting domestic goats. As CCPP has never been documented in grazing antelopes (subfamily hippotraginae), they were not considered susceptible. Mycoplasma capricolum subspecies capripneumoniae (Mccp) was isolated from pleural liquid collected during the necropsy of a severely emaciated Arabian oryx with mild nasal discharge. The Mccp isolate was then genotyped using a multilocus sequence scheme; the sequence type was identical to the Mccp strain previously identified in a sand gazelle from a nearby enclosure. This case shows for the first time that members of the hippotraginae subfamily, here the Arabian oryx, can be affected by CCPP. In addition, genotyping shows that the oryx was most probably infected, at a distance, by sand gazelles. PMID:25069622

  14. Pathogenic micro-organisms and helminths in sewage products, Arabian Gulf, country of Bahrain.

    PubMed Central

    Amin, O M

    1988-01-01

    Fecal and sludge samples from the Arabian Gulf country of Bahrain contained poliomyelitis and coxackie viruses, coliform bacteria, Escherichia coli, Salmonella spp., Shigella sonni, fecal streptococci, Balantidium coli, Ascaris lumbricoides and Hymenolepis nana eggs, and Strongyloides stercoralis. Sludge produced in the central sewage treatment plant is used for agricultural purposes and poses a threat to public health. Recommendations to reduce the potential health hazards are made. PMID:3341504

  15. The history of the Arabian platform evolution in the Late Permian and Triassic

    SciTech Connect

    Bebeshev, I.I.

    1995-03-01

    On the basis of comprehensive investigations of the Upper Permian and Triassic sequences of the Arabian platform, three stages were recognized, corresponding to distinct time intervals. The first stage corresponds to the Latest Permian-Early Triassic, the second - to the Early-Middle Triassic, the third - to the Late Triassic. Special maps were plotted for the second and third stages, reflecting major paleogeographic and paleotectonic events. An effort was made to test the oil potential of the sequences.

  16. Role of KCNQ2 and KCNQ3 genes in juvenile idiopathic epilepsy in Arabian foals.

    PubMed

    Lichter-Peled, Anat; Polani, Sagi; Stanyon, Roscoe; Rocchi, Mariano; Kahila Bar-Gal, Gila

    2013-04-01

    Juvenile idiopathic epilepsy (JIE) in Arabian foals resembles benign-familial neonatal convulsion (BFNC) syndrome, a rare idiopathic epilepsy of new-born humans. BFNC syndrome exhibits genetic heterogeneity, as has been hypothesised to occur in Arabian foals, and is known to be caused by mutations in the voltage-gated potassium channel subunit KCNQ2 and KCNQ3 genes. The close phenotypic characteristics of both Arabian foals and children suggest these epileptic syndromes are caused by the same genetic disorder. In horses, the KCNQ2 and KCNQ3 genes are located on the terminal region of chromosomes 22 and 9, respectively, essentially homologous to their location on chromosomes 20q13.3 and 8q24 in humans. Gene trees for the KCNQ2 and KCNQ3 genes between horses and other mammals, particularly humans and mice, were constructed and compared to widely accepted mammalian phylogenetic trees. The KCNQ2 gene tree exhibited close clustering between horses and humans, relative to horses and mice, in contrast to the evolutionary trees of other mammals. Distance values between the horse and human groups were lower as opposed to those found between the horse and mouse groups. The similarity between the horse and the human, especially for the KCNQ2 gene, where the majority of mutations causing BFNC have been found, supports the hypothesis of similar heritable and genetic patterns of the disease in both species and suggests that contrary to the classic mouse-model concept, humans may be a more suitable model for the study of JIE in Arabian foals. PMID:23182620

  17. Assessment of undiscovered conventionally recoverable petroleum resources of Arabian-Iranian basin

    SciTech Connect

    Masters, C.D.; Klemme, H.D.; Coury, A.B.; Peterson, J.A.

    1986-05-01

    Undiscovered, conventionally recoverable petroleum resources in the Arabian-Iranian basin are estimated at probability levels of 95%, 5%, and statistical mean. Estimates for oil are 72, 337, and 174 billion bbl; for gas, they are 299, 1, 792, and 849 tcf. Petroleum occurrences can be accounted for in five definitive geologic settings of plays. Undiscovered resource potential is assessed, assuming that new discoveries will expand the occurrence of petroleum in these basic plays. The five plays listed in sequence are: (1) Upper Cretaceous and Tertiary, (2) Lower and middle Cretaceous sandstone, (3) Lower and middle Cretaceous limestone, (4) Jurassic, and (5) Permian. The Permian play is located in the south-central Arabian Gulf region and extends northeast-southwest from southern Iran to the Ar Rub'al Khali in Saudi Arabia. It accounts for more than four-fifths of the mean estimate of undiscovered gas. The Jurassic play, located on the south side of the Arabian Gulf, accounts for slightly less than one-third of the estimated undiscovered oil, which is split equally between Saudi Arabia and Iraq. The Lower and middle Cretaceous limestone play is located in the southern gulf region and accounts for about one-fifth of the undiscovered oil. The Lower and middle Cretaceous sandstone play is centralized in Kuwait at the heat of the Arabian Gulf, with significant potential extending northwest into Iraq. This play accounts for about one-third of the undiscovered oil. The Upper Cretaceous-Tertiary play is located in the Zagros foldbelt of Iran and Iraq, and accounts for about one-fifth of the undiscovered oil.

  18. Assessment of undiscovered conventionally recoverable petroleum resources of the Arabian-Iranian Basin

    SciTech Connect

    Masters, C.D.; Klemme, H.D.; Coury, A.B.

    1982-01-01

    The estimates of undiscovered conventionally recoverable petroleum resources in the Arabian-Iranian basin at probability levels of 95 percent, 5 percent, and statistical mean are for oil (in billions of barrels); 72,337, and 174; and for gas (in trillions of cubic feet): 299, 1792, and 849. The occurrence of petroleum can be accounted for in five definitive geological settings or plays. The five plays listed by geologic age are: (I) Upper Cretaceous and Tertiary, (II) Lower and Middle Cretaceous sandstone, (III) Lower and Middle Cretaceous limestone, (IV) Jurassic, and (V) Permian. The Permian play, located in the south-central Arabian Gulf region and extending northeast-southwest from southern Iran to the Ar Rub'al Khali in Saudi Arabia, accounts for over four-fifths of the mean estimate of undiscovered gas. The remainder of the gas is divided about equally among the other four plays. The Jurassic play, located on the south side of the Arabian Gulf, accounts for slightly less than one-third of the estimated undiscovered oil, which is split equally between Saudi Arabia and Iraq. The Lower and Middle Cretaceous limestone play is located in the southern Gulf region and accounts for about one-fifth of the undiscovered oil, most of which is located in Saudi Arabia and the remainder in the United Arab Emirates. The Lower and Middle Cretaceous sandstone play is centralized in Kuwait at the head of the Arabian Gulf with significant potential extending to the northwest in Iraq; the play accounts for about one-third of the undiscovered oil, the great majority of which is estimated to be in Iraq with the remainder divided between Saudi Arabia and Kuwait. The upper Cretaceous-Tertiary play is located in the Zagros fold belt of Iran and Iraq and accounts for about one-fifth of the undiscovered oil. 5 references, 16 figures, 3 tables.

  19. Controls on Albian-Cenomanian carbonate platform sedimentation in middle eastern region: Kesalon event, a middle Cretaceous sea level change in Israel and its correlation with global sea level changes

    SciTech Connect

    Braun, M.; Hirsch, F.

    1987-05-01

    After Neocomian regional denudation, Aptian Telemim (= Blanche) carbonates onlapped the Arabian subplate, followed by Yavne-Tammun regression and Albian transgression. Near the Levant coast, the Albian-early Coniacian Judea carbonate platform interfingers with the Talme Yaffe basin to the west. To the south and east, Judea-type carbonates gradually onlap the mainly continental Kurnub (Nubia type) clastics of the peri-Arabian belt. Detailed analysis of the cyclic sedimentation within the 700-m thick Judea Limestone reveals a regressive trend near the top of the Albian Yagur Formation in Galilee, the Hevyon Formation in the Negev, and the ledge of the Kesalon formation in central Israel Judean Hills, which represents the end of the Early Cretaceous sedimentary cycle. The early Cenomanian marly chalk of the En Yorqeam Formation starts the Cenomanian cycle, followed by bedded and massive dolomite and ammonoid-bearing limestone. Platform sedimentation before this Kesalon event is dominated by bank facies with some rudistid bioherms of presumable Albian age. After the Kesalon event, Cenomanian and Turonian platforms have fast-changing paleogeography on basinal chalks, shales, bioherms and backreef lagoons. Facies boundaries, running mainly east-west to southwest-northeast up to the Early Cretaceous, became close to north-south in the Late Cretaceous. Albian-Cenomanian regressive-transgressive cycles in Israel match fairly well with global sea level changes, in particular the Kesalon event, which corresponds to the Ka-Kb sea level change of Vail et al. Late Turonian-early Senonian thrusting of the peri-Arabian alpine belt and folding in the Syrian arc heavily affect the unraveling of global sea level changes on the Arabian subplate.

  20. Regime shift in Arabian dust activity, triggered by persistent Fertile Crescent drought

    NASA Astrophysics Data System (ADS)

    Notaro, Michael; Yu, Yan; Kalashnikova, Olga V.

    2015-10-01

    The Arabian Peninsula has experienced pronounced interannual to decadal variability in dust activity, including an abrupt regime shift around 2006 from an inactive dust period during 1998-2005 to an active period during 2007-2013. Corresponding in time to the onset of this regime shift, the climate state transitioned into a combined La Niña and negative phase of the Pacific Decadal Oscillation, which incited a hiatus in global warming in the 2000s. Superimposed upon a long-term regional drying trend, synergistic interactions between these teleconnection modes triggered the establishment of a devastating and prolonged drought, which engulfed the Fertile Crescent, namely, Iraq and Syria, and led to crop failure and civil unrest. Dried soils and diminished vegetation cover in the Fertile Crescent, as evident through remotely sensed enhanced vegetation indices, supported greater dust generation and transport to the Arabian Peninsula in 2007-2013, as identified both in increased dust days observed at weather stations and enhanced remotely sensed aerosol optical depth. According to backward trajectory analysis of dust days on the Arabian Peninsula, increased dust lifting and atmospheric dust concentration in the Fertile Crescent during this recent, prolonged drought episode supported a greater frequency of dust events across the peninsula with associated northerly trajectories and led to the dust regime shift. These findings are particularly concerning, considering projections of warming and drying for the eastern Mediterranean region and potential collapse of the Fertile Crescent during this century.

  1. A new view on dam lines in Polish Arabian horses based on mtDNA analysis

    PubMed Central

    Głażewska, Iwona; Wysocka, Anna; Gralak, Barbara; Prus, Renata; Sell, Jerzy

    2007-01-01

    Polish Arabian horses are one of the oldest and the most important Arab populations in the world. The Polish Arabian Stud Book and the Genealogical Charts by Skorkowski are the main sources of information on the ancestors of Polish Arabs. Both publications were viewed as credible sources of information until the 1990s when the data regarding one of the dam lines was questioned. The aim of the current study was to check the accuracy of the pedigree data of Polish dam lines using mtDNA analysis. The analyses of a 458 bp mtDNA D-loop fragment from representatives of 15 Polish Arabian dam lines revealed 14 distinct haplotypes. The results were inconsistent with pedigree data in the case of two lines. A detailed analysis of the historical sources was performed to explain these discrepancies. Our study revealed that representatives of different lines shared the same haplotypes. We also noted a genetic identity between some lines founded by Polish mares of unknown origin and lines established by desert-bred mares. PMID:17897600

  2. Application of mitochondrial genes sequences for measuring the genetic diversity of Arabian oryx.

    PubMed

    Khan, Haseeb A; Arif, Ibrahim A; Shobrak, Mohammad; Homaidan, Ali A Al; Farhan, Ahmad H Al; Sadoon, Mohammad Al

    2011-01-01

    Arabian oryx (Oryx leucoryx) had faced extinction in the wild more than three decades ago and was saved by the prudent efforts of captive breeding programs. A clear understanding of the molecular diversity of contemporary Arabian oryx population is important for the long term success of captive breeding and reintroduction of this potentially endangered species. We have sequenced the segments of mitochondrial DNA including12S rRNA, 16S rRNA, cytochrome b (Cyt-b) and control region (CR) genes of 24 captive-bred and reintroduced animals. Although the sequences of 12S rRNA, 16S rRNA and Cyt-b were found to be identical for all the samples, typical sequence variations in the CR gene were observed in the form of 7 haplotypes. One of these haplotypes has been reported earlier while the remaining 6 haplotypes are novel and represent different lineages from the founders. The haplotype and nucleotide diversities were found to be 0.789 and 0.009 respectively. The genetic distances among the 7 mtDNA haplotypes varied from 0.001 to 0.017. These findings are of potential relevance to the management of captive breeding programs for the conservation of Arabian oryx. PMID:21498924

  3. Measuring the genetic diversity of Arabian Oryx using microsatellite markers: implication for captive breeding.

    PubMed

    Arif, Ibrahim A; Khan, Haseeb A; Shobrak, Mohammad; Homaidan, Ali A Al; Sadoon, Mohammad Al; Farhan, Ahmad H Al

    2010-04-01

    Arabian oryx (Oryx leucoryx) is an endangered antelope that is being protected by captive breeding programs. However, the long term success of these programs mainly depends on the prudent use of molecular information for conservation management. We have used an array of seven microsatellite loci to examine the molecular diversity in a representative population of 24 captive-bred and reintroduced Arabian oryx. The locus-wise mean observed heterozygosity (0.601) was found to be comparatively higher than the mean expected heterozygosity (0.565). The specimen-wise observed heterozygosity ranged from 0.143 to 1.00 with an average of 0.60 whereas the mean d(2) varied from 0.57 to 1023.428 with an average value of 223.357. The results of Shannon information index (I = 0.898) also indicated a high level of within population genetic diversity. The average gene flow was 0.298, ranging between 0.204 and 0.424 for different loci. In conclusion, the information about the extent of heterozygosity, allelic diversity and inbreeding/outbreeding depression using microsatellite markers could be of potential relevance for the management of captive breeding programs for the conservation of Arabian oryx. PMID:20558900

  4. Red cell parameters in infant and children from the Arabian Peninsula

    PubMed Central

    Mekaini, Lolowa A Al; Denic, Srdjan; Jabri, Omar N Al; Narchi, Hassib; Souid, Abdul-Kader; Al-Hammadi, Suleiman

    2015-01-01

    α+-Thalassemia trait and iron deficiency anemia are frequent causes of microcytosis and a common diagnostic challenge in Arabian children. In this study, their prevalences and effects on the red cell parameters were evaluated in 28,457 children aged one day to 6 years. α+-Thalassemia trait was considered to be present when mean cell volume (MCV) was <94 fL at birth and iron deficiency anemia when red cell distribution width (RDW) was >14.5%. The prevalence of α+-thalassemia trait was 15.7% (502/3,191), which was similar to previously reported values for adults (9-14%). Iron deficiency anemia peaked at 7 months (53%) and then declined at a rate of 8% per year. The nadirs of red blood cell count (RBC) and hemoglobin concentration (Hb) occurred at two months of age (physiological anemia). Subsequently, Hb increased at a rate similar to that of MCV, demonstrating the two processes are coupled. The third percentile MCV in children older than 3 months was ≤64 fL, which was significantly lower than that in European children. The third percentile Hb, on the other hand, was similar to that in European children. Thus, α+-thalassemia trait and iron deficiency anemia are exceptionally frequent in Arabian children and their red cell indices are considerably different from European-based norms. Careful interpretation of red cell parameters is required for the evaluation of microcytic anemia in Arabian children. PMID:27069759

  5. Isostatic models and isostatic gravity anomalies of the Arabian plate and surroundings

    NASA Astrophysics Data System (ADS)

    Kaban, Mikhail K.; El Khrepy, Sami; Al-Arifi, Nassir

    2015-04-01

    Isostaic anomalies represent one of the most useful "geological" reduction of the gravity field. With the isostatic correction it is possible to remove a significant part of the effect of deep density heterogeneity, which dominates in the Bouguer gravity anomalies. This correction is based on the fact that a major part of the near-surface load is compensated by variations of the lithosphere boundaries (chiefly the Moho and LAB) and by density variations within the crust and upper mantle. It is usually supposed that it is less important to a first order, what is the actual compensation model when reducing the effect of compensating masses, since their total weight is exactly opposite to the near-surface load. We compare several compensating models for the Arabian plate and surrounding area. The Airy model gives very significant regional isostatic anomalies, which can not be explained by the upper crust structure or disturbances of the isostatic equilibrium. Also the predicted "isostatic" Moho is very different from the existing observations. The second group of the isostatic models includes the Moho, which is based on existing seismic determinations. Additional compensation is provided by density variations within the lithosphere (chiefly in the upper mantle). In this way we minimize regional anomalies over the Arabian plate. The residual local anomalies well correspond to tectonic structure of the plate. Still very significant anomalies are associated with the Zagros fold belt, the collision zone of the Arabian and Eurasian plates.

  6. Oil and development in the Arabian Gulf: A selected annotated bibliography

    SciTech Connect

    Sharif, W.I.

    1985-01-01

    This past decade has witnessed a vast proliferation of literature on the Arabian Gulf region. In this book the author provides a systematic guide to the literature in order to assist those conducting research on the area. The author is primarily concerned with the national, regional and international role of Arabian Gulf oil between 1973 and 1983. He includes more general sources, however, if they are partly devoted to the subject or if they provide information essential to the understanding of the particular economic systems or the place of Arabian Gulf oil within the world energy situation. Sources of a technical nature have been excluded, such as those dealing with the science and technology of Arab oil. The main languages of the material selected for inclusion are English and Arabic, with French, German, Italian, and Spanish sources in smaller number. The Arabic sources are appended separately after the Western language sections in each chapter. The sources of information cited include books, monographs, articles, journals, theses, annual reports, directories, government documents, and various unpublished papers and documents.

  7. Trace elements in fish from the Arabian Gulf and the Shatt al-Arab river, Iraq

    SciTech Connect

    Abaychi, J.; Al-Saad, H.T.

    1988-02-01

    In the Arabian Gulf region, recently, vast industrial, agricultural, economic and social developments have taken place, in addition to an increase in population. This may enhance the magnitude of environmental pollution year by year. No detailed study has been undertaken to assess the concentrations of trace elements in commercial species of fish from the Arabian Gulf and the Shatt al-Arab River, despite the fact that fish are considered an essential part of the diet in the region. Therefore, an investigation was carried out on the concentration of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn in the following fish species from the Arabian Gulf: Tylosurus strongylurus, Eleutheoronema tetradactum, Pomadasys arel, Platycephalus indicus, Ilisha elongata, Thryssa hamiltonii, Arius thalassinus, Acanthophagrus luteus, Johnieops sina, Liza dussumeiri, Hilsa ilisha, Nematolosa nasus and Otoliths argenteus, and on species from the Shatt al-Arab River: Mesopotamichthys sharpeyi, Barbus xanthopterus, Barbus scheich, Aspius vorax, Cyprinus carpio, and Barbus grypus. Trace element levels in sediment samples from the area were also determined since sediments can accumulate different elements and may reflect the extent of pollution by these elements.

  8. Carbonate-evaporite sequences of the late Jurassic, southern and southwestern Arabian Gulf

    SciTech Connect

    Alsharhan, A.S.; Whittle, G.L.

    1995-11-01

    The carbonate-evaporite sequences of the Upper Jurassic Arab and overlying Hith formations in the southern and southwestern Arabian Gulf form many supergiant and giant fields that produce from the Arab Formation and are excellent examples of a classic reservoir/seal relationship. The present-day sabkha depositional setting that extends along most of the southern and southwestern coasts of the Arabian Gulf provides an analog to these Upper Jurassic sedimentary rocks. In fact, sabkha-related diagenesis of original grain-supported sediments in the Arab and Hith formations has resulted in five distinct lithofacies that characterize the reservoir/seal relationship: (1) oolitic/peloidal grainstone, (2) dolomitic grainstone, (3) dolomitic mudstone, (4) dolomitized grainstone, and (5) massive anhydrite. Interparticle porosity in grainstones and dolomitic grainstones and intercrystalline porosity in dolomitized rocks provide the highest porosity in the study area. These sediments accumulated in four types of depositional settings: (1) supratidal sabkhas, (2) intertidal mud flats and stromatolitic flats, (3) shallow subtidal lagoons, and (4) shallow open-marine shelves. The diagenetic history of the Arab and Hith formations in the southern and southwestern Arabian Gulf suggests that the anhydrite and much of the dolomitization are a result of penecontemporaneous sabkha diagenesis. The character and timing of the paragenetic events are responsible for the excellent porosity of the Arab Formation and the lack of porosity in the massive anhydrites of the Hith, which together result in the prolific hydrocarbon sequences of these formations.

  9. Physiographic discontinuity along the Levant-Margin hinge-belt of the Arabian Plate (Late Cenomanian, northern Israel)

    NASA Astrophysics Data System (ADS)

    Frank, Ran; Buchbinder, Binyamin; Benjamini, Chaim

    2014-07-01

    The paleo-depositional hinge-belt of the Levant is a zone of rapid proximal-to-distal carbonate facies transitions that defined the western edge of the passive Mesozoic Levant Margin of the Arabian Plate. It was striking parallel to the present day Mediterranean coastline, from northern Sinai to northern Lebanon, but in the mid-Cretaceous a “gap zone”, in which the facies transitions are unclear, extended from northern Israel to southern Mt. Lebanon. This study examines the paleo-physiography and sedimentary evolution in this “gap zone” in the Late Cenomanian of northern Israel. The sedimentary evolution in this region is reflected by five genetic-stratigraphic units representing systems tracts, which were proximal in the Galilee region to the north and distal to the SSW in the Carmel region. During the early Late Cenomanian a carbonate ramp sloped gently from the Galilee towards the Carmel region. Later in the Cenomanian the Galilean part of the ramp was strongly uplifted and faulting enhanced the topography of this region. A steep SSW-facing slope was formed in the Galilee, subdivided into extensional basins tens to hundreds of meters in length. Carbonate sand filled these small basins and was mass-transported further downslope, forming sheeted calciturbidites to the south in the Carmel region. This depositional phase terminated in sea-level fall and subaerial exposure. During the latest Cenomanian, faulting was renewed in the Galilee region, muddy carbonate was deposited on the slope and shelf, and debrites and slides were mass-transported downslope as far as the Carmel region. This depositional phase ended by a second episode of subaerial exposure that was followed by Early Turonian sea-level rise. The direction of mass transport in this region and the trend of proximal-to-distal facies transitions, as well as the strike of the Cenomanian faults, indicate that the depositional strike of the Levantine hinge-belt shifted in this region toward the east

  10. Sea Legs

    NASA Astrophysics Data System (ADS)

    Macdonald, Kenneth C.

    Forty-foot, storm-swept seas, Spitzbergen polar bears roaming vast expanses of Arctic ice, furtive exchanges of forbidden manuscripts in Cold War Moscow, the New York city fashion scene, diving in mini-subs to the sea floor hot srings, life with the astronauts, romance and heartbreak, and invading the last bastions of male exclusivity: all are present in this fast-moving, non-fiction account of one woman' fascinating adventures in the world of marine geology and oceanography.

  11. The interaction of the sea breezes with the boundary layer along the Red Sea coast and its effect on the dust transport

    NASA Astrophysics Data System (ADS)

    Khan, Basit Ali; Stenchikov, Georgiy; Abualnaja, Yasser

    2013-04-01

    Sea and land breezes are common meteorological phenomena in most coastal regions of the world. The thermally induced mesoscale circulation of sea breezes modifies the planetary boundary layer (PBL) by forming a convective internal boundary layer (CIBL), which can trap dust and other pollutants in the thin convective layer while the return flow can transport dust and pollutants from the land towards the sea. We used the Advanced Research WRF (ARW) modeling system to study the structure and dynamics of sea breezes in the middle region of the Red Sea (around 25°N) on the western coast of Saudi Arabia. Results showed the existence of two thermal circulations on both the western and eastern coasts of the Red Sea. The modeling results are consistent with observations from buoys and meteorological towers along the Saudi Arabian coast and suggest that the onset of the sea breeze in this area typically occurs at about 0800 Local Standard Time (LST). The sea breeze decays after 1700 LST, although the timing of the onset and decay could be affected by the sea-land thermal gradient, topography, the sea-land orientation and the direction and strength of the wind. The depth of the predicted inflow layer reaches one kilometer while the height of sea breeze head may reach three kilometers. The rocky mountain range of Al-Sarawat, along the Saudi coast line, restricts the inland propagation of the sea breeze and significantly affects the structure of the flow. We conducted a detailed process analysis of our simulation results to understand the sea breeze and PBL interaction and its effect on local meteorology and dust transport.

  12. The impact of North Indian Ocean sea surface temperatures on the Indian summer monsoon

    NASA Astrophysics Data System (ADS)

    Levine, Richard; Turner, Andrew

    2010-05-01

    The relationship between sea surface temperature (SST) in the North Indian Ocean and Indian monsoon rainfall is investigated in both observational/re-analyses and climate model simulations. We focus on the partially land-enclosed Arabian Sea and Bay of Bengal, where SSTs are found to have significant correlations with All Indian Rainfall (AIR). This part of the Indian Ocean is therefore important for monsoon predictions, while this area tends to provide significant problems in coupled atmosphere-ocean model simulations. The observational variability of the SST-rainfall relationship is investigated on seasonal to decadal time-scales. This highlights a predominantly negative correlation over the monsoon trough area in North East India and a positive correlation over the rest of India, while these relationships are found to be weakened by the ENSO-monsoon teleconnection. Mechanisms are further investigated by performing a series of atmosphere-only model simulations using the Met Office Unified Model (MetUM). In these experiments we determine the response of the atmosphere to forced cold SST anomalies over isolated areas, which we also extend out into the equatorial Indian Ocean. The cold SSTs in the Arabian Sea and Bay of Bengal lead to a dramatic reduction in Indian rainfall, while cold biases in the equatorial Indian Ocean have the opposite effect, highlighting the competition between oceanic and continental Tropical Convergence Zones (TCZ). However, the impacts for the Arabian Sea and Bay of Bengal experiments are found to change between the pre-monsoon and post-monsoon onset periods.The impact on monsoon rainfall for cold SST biases in these regions is found to be the result of a balance between changes in regional low-level temperature gradients and the availability of moisture over the oceans, which determine the pathway of the monsoon jet and the moisture transport towards India. These experiments suggest that the intra-seasonal variability of the relationship

  13. Propagation of Gulf of Aden Intermediate Water (GAIW) in the Red Sea during autumn and its importance to biological production

    NASA Astrophysics Data System (ADS)

    Wafar, Mohideen; Ashraf, Mohamed; Manikandan, K. P.; Qurban, Mohammad Ali; Kattan, Yasser

    2016-02-01

    Analysis of high-resolution CTD data acquired at closely spaced stations during two cruises in the Saudi Arabian waters of the Red Sea (17 to 27°N), supported by the multiple tracer analysis (Mackas et al., 1987), showed that the Gulf of Aden Intermediate Water (GAIW) is clearly detectable as far as north as 26°N in the Red Sea basin albeit at a fraction less than 10%. Continuity of core salinity minima of the GAIW layer also showed that the northward propagation of GAIW north of 20°N happens mainly along the Saudi Arabian coast. The discontinuity of core minima of GAIW properties in a section along the axis, coincidence of these with alternating directions of zonal currents, the good relationships between concentrations of nutrients and salinity in the GAIW layer, and the cores of high nutrient concentrations in this section led to the conclusions that the GAIW is entrained in eddy circulations across the basin and that it is a significant source of nutrients to the entire Red Sea basin. However, the addition of nutrients with GAIW could account for only a small fraction of the nutrients (as nitrogen) needed for primary production, suggesting that recycling within the Red Sea and input from other sources will have to be significant enough to sustain the current levels of primary production measured in Red Sea waters.

  14. The Road to Culturally Relevant Pedagogy: Expatriate Teachers' Pedagogical Practices in the Cultural Context of Saudi Arabian Higher Education

    ERIC Educational Resources Information Center

    Hamdan, Amani K.

    2014-01-01

    This case study explored the need for culturally relevant pedagogy (CRP) in Saudi Arabian higher education, especially when students have a cultural background that differs from that of their instructor. The study documented how expatriate teachers structured their pedagogical practices in the Saudi Arabian context. It examined how these…

  15. 77 FR 61046 - The Amendment of the Designation of Al-Qa'ida in the Arabian Peninsula, aka Al-Qa'ida of Jihad...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-05

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF STATE The Amendment of the Designation of Al-Qa'ida in the Arabian Peninsula, aka Al-Qa'ida of Jihad Organization in the Arabian Peninsula, aka Tanzim Qa'idat al-Jihad fi Jazirat al-Arab, aka Al- Qa'ida in Yemen, aka...

  16. 77 FR 61046 - The Review and Amendment of the Designation of Al-Qa'ida in the Arabian Peninsula, aka Al-Qa'ida...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-05

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF STATE The Review and Amendment of the Designation of Al-Qa'ida in the Arabian Peninsula, aka Al-Qa'ida of Jihad Organization in the Arabian Peninsula, aka Tanzim Qa'idat al-Jihad fi Jazirat al-Arab, aka Al- Qa'ida in...

  17. Black Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Black