Search

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2009.09.008 Byline: Christian B. Rodehacke (a)(b), Wolfgang Roether (a), Hartmut H. Hellmer (c), Timothy Hall (d) Abstract: The knowledge of chlorofluorocarbon (CFC11, CFC12) concentrations in ocean surface waters is a prerequisite for deriving formation rates of, and water mass ages in, deep and bottom waters on the basis of CFC data. In the Antarctic coastal region, surface-layer data are sparse in time and space, primarily due to the limited accessibility of the region. To help filling this gap, we carried out CFC simulations using a regional ocean general circulation model (OGCM) for the Southern Ocean, which includes the ocean-ice shelf interaction. The simulated surface layer saturations, i.e. the actual surface concentrations relative to solubility-equilibrium values, are verified against available observations. The CFC surface saturations driven by concentration gradients between atmosphere and ocean are controlled mainly by the sea ice cover, sea surface temperature, and salinity. However, no uniform explanation exists for the controlling mechanisms. Here, we present simulated long-term trends and seasonal variations of surface-layer saturation at Southern Ocean deep and bottom water formation sites and other key regions, and we discuss differences between these regions. The amplitudes of the seasonal saturation cycle vary from 22% to 66% and their long-term trends range from 0.1%/year to 0.9%/year. The seasonal surface saturation maximum lags the ice cover minimum by two months. By utilizing observed bottle data the full seasonal CFC saturation cycle can be determined offering the possibility to predict long-term trends in the future. We show that ignoring the trends and using instead the saturations actually observed can lead to systematic errors in deduced inventory-based formation rates by up to 10% and suggest an erroneous decline with time. Author Affiliation: (a) Universitat Bremen, Institut fur Umweltphysik (IUP), Abteilung Ozeanographie, Otto-Hahn-Allee, D-28359 Bremen, Germany (b) Columbia University, Department for Applied Physics and Applied Mathematics, 2880 Broadway, New York, NY 10025, USA (c) Alfred Wegener Institut, Department Climate Science, BussestraAe 24, D-27570 Bremerhaven, Germany (d) NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, USA Article History: Received 20 March 2008; Revised 29 August 2009; Accepted 22 October 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2009.10.003 Byline: Alonso Hernandez-Guerra (a), Terrence M. Joyce (b), Eugenio Fraile-Nuez (c), Pedro Velez-Belchi (c) Keywords: Meridional Overturning Circulation; Argo floats; Objective analysis; Box inverse model Abstract: Using a variety of oceanographic data, including direct volume transports in the Florida Strait, and Argo float profiles and drift velocities at 24[degrees]N and 36[degrees]N in the North Atlantic, inverse calculations are presented in which the net meridional transport, down to a depth of approximately 1600m, is estimated at both latitudes for a 5-year period 2003-2007. The upper ocean is divided into seven layers using neutral density, and mass conservation constraints have been applied to a closed box bounded by these latitudes, including the Florida Strait. Ekman layer transports have been included in the top-most layer, and the inverse calculation has solved for changes from the initial reference velocities, Ekman and Florida Strait transports, given a priori estimates on the accuracy of each of these quantities. Solutions with and without transformations due to Mediterranean Water (MW) formation are made. Our results indicate that (1) time-averaged transport estimates derived from Argo have significant less eddy noise than individual hydrographic sections, (2) Argo drift velocities provide information to the inverse solution for the ocean interior, and (3) comparison of the total integrated interior mass transports in the thermocline waters for the period 2003-2007 with the previous estimates based on trans-ocean hydrographic sections shows that, within the errors of our estimation, the upper limb of the Atlantic Meridional Overturning Circulation has not significantly changed since 1957. Author Affiliation: (a) Facultad de Ciencias del Mar, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas, Spain (b) Department of Physical Oceanography, Woods Hole Oceanographic Institution, 360 Woods Hole Road, Mail Stop 21, Woods Hole, MA 02543, USA (c) Instituto EspaA[+ or -]ol de Oceanografia, Avenida Tres de Mayo, 73, 38005 Santa Cruz de Tenerife, Spain Article History: Received 4 April 2009; Revised 29 September 2009; Accepted 2 October 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2009.07.001 Byline: A. Srinivasan (a)(b), Z. Garraffo (a)(b), M. Iskandarani (a) Abstract: Abyssal pathways and volume transports in the Indian Ocean obtained from a 1/12.sup.a global data assimilative hindcast for the years 2004-2006 are presented. The known features of bottom water circulation such as boundary currents and inter-basin exchanges are well represented in the hindcast solution. Further, the hindcast solution reveals a basin-wide, anti-cyclonic deep circulation pattern with the main inflow located in the east, in the Perth Basin, and outflow in the west along the African continent and Madagascar. Inter-basin westward transport at 10.sup.aS across the Ninetyeast Ridge and along the Mascarene Plateau connect the inflow and outflow locations. The model develops a net bottom water inflow of 10[+ or -]8Sv (mean[+ or -]standard deviation) across 32.sup.aS, below approximately 3500m of which 4[+ or -]7Sv are returned south across the same latitude in the deep layers between 2000 and 3500m. Significant variability on intra-seasonal, semi-annual and annual time scales is present in the abyssal flow fields. The vertical mixing algorithm, based on resolved vertical shear, suggests enhanced diapycnal upwelling in the vicinity of the Central Indian Ridge. Author Affiliation: (a) Meteorology and Physical Oceanography Division, RSMAS, University of Miami, FL 33149, USA (b) Center for Computational Science, University of Miami, FL 33124, USA Article History: Received 26 May 2008; Revised 23 June 2009; Accepted 3 July 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2009.05.010 Byline: Dagmar Kieke (a), Birgit Klein (b), Lothar Stramma (c), Monika Rhein (a), Klaus Peter Koltermann (b) Keywords: Subpolar North Atlantic; Ocean circulation; Water mass spreading; Labrador Sea Water; Mid-Atlantic Ridge Abstract: The variability of two modes of Labrador Sea Water (LSW) (upper and deep Labrador Sea Water) and their respective spreading in the interior North Atlantic Ocean are investigated by means of repeated ship surveys carried out along the zonal WOCE line A2/AR19 located at 43-48[degrees]N (1993-2007) and along the GOOS line at about 48-51[degrees]N (1997-2002). Hydrographic section data are complemented by temperature, salinity, and velocity time series recorded by two moorings. They have been deployed at the western flank of the Mid-Atlantic Ridge (MAR) in the Newfoundland Basin during 1996-2004. The analysis of hydrographic anomalies at various longitudes points to a gradual eastward propagation of LSW-related signals, which happens on time scales of 3-6 years from the formation region towards the MAR. Interactions of the North Atlantic Current (NAC) with the Deep Western Boundary Current (DWBC) close to Flemish Cap point to the NAC being the main distributor of the different types of LSW into the interior of the Newfoundland Basin. Comparisons between the ship data and the mooring records revealed that the mooring sites are located in a region affected by highly variable flow. The mooring time series demonstrate an elevated level of variability with eddy activity and variability associated with the NAC considerably influencing the LSW signals in this region. Hydrographic data taken from Argo profiles from the vicinity of the mooring sites turned out to mimic quite well the temporal evolution captured by the moorings. There is some indication of occasional southward flow in the LSW layer near the MAR. If this can be considered as a hint to an interior LSW-route, it is at least of minor importance in comparison to the DWBC. It acts as an important supplier for the interior North Atlantic, distributing older and recently formed LSW modes southward along the MAR. Author Affiliation: (a) Institut fur Umweltphysik, Abt. Ozeanographie, Universitat Bremen, Postfach 330440, 28334 Bremen, Germany (b) Bundesamt fur Seeschifffahrt und Hydrographie, Hamburg, Germany (c) Leibniz-Institut fur Meereswissenschaften an der Universitat Kiel, IFM-GEOMAR, Kiel, Germany Article History: Received 18 July 2008; Revised 11 May 2009; Accepted 18 May 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2009.04.007 Byline: Daniel M. Sigman (a), Peter J. DiFiore (a), Mathis P. Hain (b), Curtis Deutsch (c), Yi Wang (a), David M. Karl (d), Angela N. Knapp (e), Moritz F. Lehmann (f), Silvio Pantoja (g) Keywords: Nitrate; Stable isotope; Biogeochemistry; Numerical model; Nutrients Abstract: We compare the output of an 18-box geochemical model of the ocean with measurements to investigate the controls on both the mean values and variation of nitrate [delta].sup.15N and [delta].sup.18O in the ocean interior. The [delta].sup.18O of nitrate is our focus because it has been explored less in previous work. Denitrification raises the [delta].sup.15N and [delta].sup.18O of mean ocean nitrate by equal amounts above their input values for N.sub.2 fixation (for [delta].sup.15N) and nitrification (for [delta].sup.18O), generating parallel gradients in the [delta].sup.15N and [delta].sup.18O of deep ocean nitrate. Partial nitrate assimilation in the photic zone also causes equivalent increases in the [delta].sup.15N and [delta].sup.18O of the residual nitrate that can be transported into the interior. However, the regeneration and nitrification of sinking N can be said to decouple the N and O isotopes of deep ocean nitrate, especially when the sinking N is produced in a low latitude region, where nitrate consumption is effectively complete. The [delta].sup.15N of the regenerated nitrate is equivalent to that originally consumed, whereas the regeneration replaces nitrate previously elevated in [delta].sup.18O due to denitrification or nitrate assimilation with nitrate having the [delta].sup.18O of nitrification. This lowers the [delta].sup.18O of mean ocean nitrate and weakens nitrate [delta].sup.18O gradients in the interior relative to those in [delta].sup.15N. This decoupling is characterized and quantified in the box model, and agreement with data shows its clear importance in the real ocean. At the same time, the model appears to generate overly strong gradients in both [delta].sup.18O and [delta].sup.15N within the ocean interior and a mean ocean nitrate [delta].sup.18O that is higher than measured. This may be due to, in the model, too strong an impact of partial nitrate assimilation in the Southern Ocean on the [delta].sup.15N and [delta].sup.18O of preformed nitrate and/or too little cycling of intermediate-depth nitrate through the low latitude photic zone. Author Affiliation: (a) Department of Geosciences, Princeton University, Princeton, NJ 08544, USA (b) Institute of Geosciences, University of Potsdam, PO Box 60 15 53, Potsdam D-14415, Germany (c) Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095, USA (d) Department of Oceanography, 1000 Pope Rd. MSB 629, University of Hawaii, Honolulu, HI 96822, USA (e) Department of Marine and Environmental Biological Sciences, University of Southern California, University of Southern California, 3616 Trousdale Parkway, AHF 108, Los Angeles, CA 90089-0371, USA (f) Institute for Environmental Geosciences, Bernoullistrasse 30, Universitat Basel, CH-4056 Basel, Switzerland (g) Department of Oceanography and Center for Oceanographic Research in the Eastern South Pacific, University of Concepcion, Casilla 160-C, Concepcion, Chile Article History: Received 21 January 2008; Revised 4 April 2009; Accepted 21 April 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2009.03.005 Byline: Martin Saraceno (a)(b), Christine Provost (c), Uriel Zajaczkovski (b)(d) Keywords: Zapiola Rise; South Atlantic circulation; Interannual variability Abstract: The Zapiola Rise (ZR) is a singular sedimentary deposit about 1200m in height and 1500km in width located in the Argentine Basin. In situ and satellite observations have revealed the presence of an intense counterclockwise circulation around the feature, with a volume transport comparable to those of the major ocean currents. The existence of a very low-frequency variability of the transport associated with the anticyclonic circulation is documented for the first time. As the Zapiola anticyclonic circulation plays a significant role in the mixing of the strongly contrasted water masses of the South Atlantic, variations in the anticyclonic transport can have a major impact on the mixing, hence a role in global climate variability. The circulation was clearly anticyclonic in the periods 1993-1999 and 2002-2007. In contrast, the 1999-2001 period did not show evidence of an anticyclonic flow in the mean surface velocity field. Moreover, the analysis of the weekly fields during that period of time revealed a cyclonic pattern from time to time. Previous work has shown that the flow can be considered as purely barotropic over the ZR region. A 15-year time-series of the transport was produced using absolute altimeter-derived geostrophic velocities. The estimated transport presents high-frequency variability associated with mesoscale activity superimposed on a low-frequency signal. The amplitude of the estimated transport is in good agreement with the only in situ-derived estimation available (80Sv, January 1993). The low-frequency signal presents a minimum during the period 1999-2001, further suggesting that at times the Zapiola anticyclonic flow may have significantly decreased in strength or even vanished. Possible causes of the low-frequency variability are discussed. Author Affiliation: (a) Centro de Investigaciones del Mar y la Atmosfera (CIMA), Intendente Guiraldes 2160, Ciudad Universitaria, Pab. II, 2do piso, Ciudad de Buenos Aires C1428EGA, Argentina (b) Departamento de la Atmosfera y los Oceanos, FCEyN, Universidad de Buenos Aires, Intendente Guiraldes 2160, Ciudad Universitaria, Pab. II, 2do piso, Ciudad de Buenos Aires C1428EGA, Argentina (c) Laboratoire d'Oceanographie et du Climat: Experimentation et Approche Numerique (LOCEAN), Universite Pierre et Marie Curie, Tour 45/55, 5eme etage, BoA[R]te 100, 4 Place Jussieu, 75252 Paris cedex 05, France (d) Departamento de Oceanografia, Servicio de Hidrografia Naval, Av. Montes de Oca 2124, Ciudad de Buenos Aires C1270ABV, Argentina Article History: Received 8 October 2008; Revised 3 March 2009; Accepted 11 March 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2009.01.003 Byline: R.E. Roman, J.R.E. Lutjeharms Keywords: Ocean circulation; Western Boundary Current; Mesoscale eddies; Intermediate water masses; Water types; Mixing Abstract: Red Sea Intermediate Water (RSIW) has been shown to move down the Agulhas Current as distinct lenses. It has been assumed that this intermittency is the result of variable input. To clarify and quantify the nature of RSIW contributions from the source regions of the Agulhas Current observations at 15 hydrographic sections were examined using a multi-parameter analysis. In the northern Mozambique Channel RSIW is found to be layer-like, but with patches of distinctly different contributions. In the southern part of the channel the layer-like distribution disappears with RSIW mostly confined within anticyclonic and cyclonic eddies exhibiting varying maximum contributions ranging from 15-20% to 25-30% purity. Net transports across the channel ranged from -0.45 to -0.7Sv. At the southern tip of Madagascar RSIW contributions exhibited similar purity variability ranging from 10-15% to 15-20%. The net southward transport of RSIW in the East Madagascar Current displayed an even greater variability due to changes in the flux of the undercurrent ranging from negligible to -0.3Sv. Indications therefore were that the transport of RSIW to the Agulhas Current occurs in both cyclones and anti-cyclones through the Mozambique Channel whilst from the East Madagascar Current it is mostly confined to anti-cyclones. This variability in the inflow was also reflected in the northern part of the Agulhas Current proper. The maximum contributions of RSIW range here from 10-15% to 20-25% purity and net transports from -0.75 to -1.39Sv off Durban. As it was east of Madagascar RSIW was mostly confined to the slope. Author Affiliation: Department of Oceanography, University of Cape Town, Rondebosch 7700, South Africa Article History: Received 22 August 2008; Revised 8 January 2009; Accepted 15 January 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2008.12.001 Byline: Ali Harzallah Keywords: Ocean circulation; Tide; Velocity; Density; Mediterranean Sea; Strait of Gibraltar Abstract: The vertical structure of the flow variability through the Strait of Gibraltar is studied based on the Gibraltar Experiment and the Word Ocean Circulation Experiment data sets. An analysis of the leading modes of velocity and density variability at the Strait of Gibraltar showed an adjustment of the water masses exchanged through the Strait. Mediterranean mass variations resulting from the water exchanged by barotropic tidal oscillations generate changes of the baroclinic component of the flow that damp these mass variations. This adjustment explains the previously observed fortnightly variation of the shear. Moreover, the adjustment is found to operate for the subinertial time scale flow variability forced by the atmospheric pressure. An analytical model aimed at reproducing variations of the velocity with time and in the vertical is derived. The model includes a depth-varying parameterisation of friction and takes into account density gradient fluctuations across the Strait. The model reproduces the main features of the flow, in particular the shear and the interface depth variations with the tide phase. Author Affiliation: Institut National des Sciences et Technologies de la Mer, 28, rue du 2 mars 1934, 2025 SalammbA[acute accent], Tunisia Article History: Received 1 March 2007; Revised 28 November 2008; Accepted 3 December 2008

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2008.05.016 Byline: Oliver Huhn, Wolfgang Roether, Reiner Steinfeldt Keywords: Transient tracers; Tracer ages; Transit time distributions; North Atlantic Deep Water; Tropical Atlantic; South Atlantic Abstract: An extensive set of transient-tracer observations has been used to determine age spectra in Upper and Lower North Atlantic Deep Water (UNADW, LNADW) along the western continental margin between [approximately equal to]10[degrees]N and 30[degrees]S. The tracers are CFC-11, CFC-12, CCl.sub.4, and tritium, and the observations cover 20 years. The procedure was to deduce from the data the free parameters of a transit time distribution (TTD; mean age or transit time I, age dispersion I, and dilution factor by tracer-free water f) of the common functional form (Inverse Gaussian). A novel northern boundary condition for the tracers was employed; it allows for enhanced halocarbon input during convective deep-water formation in winter and yields minimized biases between observed and TTD-based tracer concentrations in downstream NADW. We found that the common boundary condition of time-invariant apparent saturations gave inconsistent results. The TTD parameter fits covered the entire region and used all tracer data jointly, the parameters being prescribed to increase linearly along-stream and the Peclet number (Pe=2I.sup.2 I.sup.-2) to be constant. For the southward transit up to the equator, we obtained for UNADW I=54 years, I=33 years, and f=1.4, with uncertainties of about [+ or -]20% estimated on the basis of a thorough error analysis. A limiting factor was a significant scatter in the NADW tracer fields. The LNADW parameter values are similar but less well constrained than for UNADW. The age spectra are broad; they correspond to large-scale along-core diffusivities on the order of 10.sup.4 m.sup.2/s. The TTD-based mean NADW flow velocities are less than 1cm/s. The relative southward increases of the TTD-based ages exceed those of CFC-11 to CFC-12 ratio ages about three-fold. An additional result is an improved CCl.sub.4 decomposition rate of 0.011[+ or -]0.002year.sup.-1 at UNADW temperatures. Our TTDs can be used to estimate the NADW-related transfer of dissolved constituents. We present such estimates for.sup.3He generated by tritium decay from the pre-nuclear period onward and for anthropogenic dissolved inorganic carbon (DIC) as examples. The latter estimate yields a NADW-related transport of anthropogenic DIC southward across the equator of about 50Mt in 1994. A critical aspect of the TTD methodology is that the older part of the age spectra is essentially unconstrained by observations. The TTDs can furthermore be used as a diagnostic tool to check certain aspects of NADW transfer in numerical ocean circulation models. Author Affiliation: Institut fur Umweltphysik (IUP), Abt. Ozeanographie, Universitat Bremen, D-28359 Bremen, Germany Article History: Received 17 October 2007; Revised 14 May 2008; Accepted 27 May 2008

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2006.03.007 Byline: Bettina A. Fach (a), Eileen E. Hofmann (b), Eugene J. Murphy (c) Abstract: A time-dependent, size-structured, physiologically based krill growth model was used in conjunction with a circulation model to test the hypothesis that Antarctic krill (Euphausia superba) populations at South Georgia are sustained by import of individuals from upstream regions. Surface phytoplankton concentrations along the simulated drifter trajectories were extracted from historical Coastal Zone Color Scanner (CZCS) measurements and sea ice biota concentrations were calculated from sea ice concentration and extent extracted along drifter trajectories from Special Sensor Microwave/Imager measurements. As additional food sources, a time series of heterotrophic food was constructed from historical data, and time series of detritus concentrations were calculated using phytoplankton concentrations extracted from CZCS measurements together with measured particulate organic carbon to chlorophyll a ratios. These food resources along specified drifter trajectories were then input to the krill growth model to determine the size and viability of krill during transport from the source region to South Georgia. The krill growth model simulations showed that no single food source can support continuous growth of krill during the 58-306 days needed for transport to South Georgia. However, under the current assumptions results indicate that combinations of food sources during the transport time enhanced krill survival, with heterotrophic food and detritus being particularly important during periods of low phytoplankton concentrations. The growth model simulations also showed that larval and juvenile krill originating along the western Antarctic Peninsula can grow to 1+ (14-36mm) and 2+ (26-45mm) age and size classes observed at South Georgia during the time needed for transport to this region. Krill originating in the Weddell Sea need 20 months for transport, which allows retention in a potentially high food environment, provided by sea ice, for almost 1 year. Krill then complete transport to South Georgia in the following year and larval and juvenile krill grow to 2+ (26-45mm) and 3+ (35-60mm) age and size classes during transport. The results of this study show that the successful transport of krill to South Georgia depends on a multitude of factors, such as the location of the spawning area and timing of spawning, food concentrations during transport, predation, and variations in the location of the Southern Antarctic Circumpolar Current Front (SACCF) and in sea ice extent. Author Affiliation: (a) Woods Hole Oceanographic Institution, Mail Stop 25, 266 Woods Hole Road, Woods Hole, MA 02543, USA (b) Center for Coastal Physical Oceanography, Crittenton Hall, Old Dominion University, Norfolk, VA 23529, USA (c) British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK Article History: Received 1 October 2004; Revised 23 September 2005; Accepted 7 March 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2006.03.006 Byline: Bettina A. Fach (a), John M. Klinck (b) Abstract: The Harvard Ocean Prediction System (HOPS) is configured to simulate the circulation of the Scotia Sea and environs. This is part of a study designed to test the hypothesis that Antarctic krill (Euphausia superba) populations at South Georgia in the eastern Scotia Sea are sustained by import of individuals from upstream regions, such as the western Antarctic Peninsula. Comparison of the simulated circulation fields obtained from HOPS with observations showed good agreement. The surface circulation, particularly through the Drake Passage and across the Scotia Sea, matches observations, with its northeastward flow characterized by three high-speed fronts. Also, the Weddell Sea and the Brazil Current, and their associated transports match observations. In addition, mesoscale variability, an important component of the flow in this region, is found in the simulated circulation and the model is overall well suited to model krill transport. Drifter simulations conducted with HOPS showed that krill spawned in areas coinciding with known krill spawning sites along the west Antarctic Peninsula continental shelf can be entrained into the Southern Antarctic Circumpolar Current Front (SACCF). They are transported across the Scotia Sea to South Georgia in 10 months or less. Drifters originating on the continental shelf of the Weddell Sea can reach South Georgia as well; however, transport from this region averages about 20 months. Additional simulations show that such transport is sensitive to changes in wind stress and the location of the SACCF. The results of this study show that krill populations along the Antarctic Peninsula and the Weddell Sea are possible source populations that can provide krill to the South Georgia population. However, successful transport of krill to South Georgia is shown to depend on a multitude of factors, such as the location of the spawning area and timing of spawning, and variations in the location of the SACCF. Therefore, this study provides insight into which environmental factors control the successful transport of krill across the Scotia Sea and with it a better understanding of krill distribution in the region. Author Affiliation: (a) Woods Hole Oceanographic Institution, Mail Stop 25, 266 Woods Hole Rd, Woods Hole, MA 02543, USA (b) Center for Coastal Physical Oceanography, Crittenton Hall, Old Dominion University, Norfolk, VA 23529, USA Article History: Received 1 October 2004; Revised 23 September 2005; Accepted 7 March 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2005.09.009 Byline: Yuan-Hui Li (a), Laurie Menviel (a), Tsung-Hung Peng (b) Keywords: Remineralization ratios; Nitrification; Partial nitrification; Denitrification; Anammox; Nitrate deficit; Indian Ocean Abstract: The three-end-member mixing model of Li and Peng [Latitudinal change of remineralization ratios in the oceans and its implication for nutrient cycles. Global Biogeochemical Cycles 16, 1130-1145] was applied to the World Ocean Circulation Experiment (WOCE) data from Indian Ocean to obtain additional estimates on the remineralization ratios (Pas.[sup.1]Nas.[sup.1]C.sub.orgas.[sup.1]aO.sub.2) of organic matter in the oxygenated regions. The results show systematic changes of the remineralization ratios with latitude and depth in the Indian Ocean. The average remineralization ratios for Indian warm water masses (potential temperature I[cedilla][approximately equal to]10.sup.aC) are Pas.[sup.1]Nas.[sup.1]C.sub.orgas.[sup.1]aO.sub.2=1as.[sup.1](15.6[+ or -]0.7)as.[sup.1](110[+ or -]9)as.[sup.1](159[+ or -]8). These are comparable to the traditional Redfield ratios (Pas.[sup.1]Nas.[sup.1]C.sub.orgas.[sup.1]aO.sub.2=1as.[sup.1]16as.[sup.1]106as.[sup.1]138), and are in good agreement with Anderson's [On the hydrogen and oxygen content of marine phytoplankton. Deep-Sea Research I 42, 1675-1680.] values of Pas.[sup.1]Nas.[sup.1]C.sub.orgas.[sup.1]aO.sub.2=1as.[sup.1]16as.[sup.1]106as.[sup.1]150 within the given uncertainties. Separation of nitrate deficits resulting from aerobic partial nitrification (dN) and anaerobic denitrification (dNa[sup.3]) processes using empirical equations is shown to be useful and consistent with other observations. The dN maximum coincides with the phosphate and nitrate maximums, lies within the oxycline below the oxygen minimum zone, and is in contact with the continental slope sediments. The dNa[sup.3] maximum lies within the oxygen minimum zone with O.sub.2 Author Affiliation: (a) Department of Oceanography, University of Hawaii, Honolulu, Hawaii 96822 (b) NOAA/AOML, Ocean Chemistry Division, Miami, Florida 33149, USA Article History: Received 3 March 2005; Revised 12 September 2005; Accepted 19 September 2005

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2005.08.003 Byline: Monika Rhein, Kerstin Kirchner, Christian Mertens, Reiner Steinfeldt, Maren Walter, Ulrich Fleischmann-Wischnath Keywords: Ocean circulation; Water mass spreading; Western tropical Atlantic; Western Atlantic; Caribbean Abstract: CTD, vessel-mounted ADCP and LADCP measurements in the Caribbean passages south of Guadeloupe (three repeats) and along 16[degrees]N (five repeats) were carried out between December 2000 and July 2004. The CTD data were used to calculate the contribution of South Atlantic water (SAW) in the upper 1200m between the isopycnals I.sub.I[cedilla]=24.5 and 27.6. Northern and southern source water masses are defined and an isopycnal mixing approach is applied. The SAW fractions are then combined with the ADCP flow field to calculate the transport of SAW into the Caribbean and across 16[degrees]N. The SAW inflow into the Caribbean through the passages south of Guadeloupe ranges from 7.6 to 11.6Sv, which is 50-75% of the total inflow. The mean (9.1[+ or -]2.2Sv) is in the range of previous estimates. Ambiguities in the northern and southern source water masses of the salinity maximum water permitted us only to calculate the contribution of SAW from the eastern source in this water mass. We estimated the additional SAW transport by the western source to be of the order of 1.9[+ or -]0.7Sv. The calculation of the SAW transport across 16[degrees]N was hampered by the presence of several anticyclonic rings from the North Brazil Current (NBC) retroflection region, some of the rings were subsurface intensified. Provided that the rings observed at 16[degrees]N are typical rings and that all rings which are annually produced in the NBC retroflection area (6.5-8.5 per year) reach 16[degrees]N, the SAW ring transport across 16[degrees]N is calculated to 5.3[+ or -]0.7Sv. From the 5 repeats at 16[degrees]N, only two showed a net northward flow, suggesting that the mean northward SAW transport is dominated by ring advection. The joint SAW transports of the Caribbean inflow (9.1Sv) and the flow across 16[degrees]N (5.3Sv) sum up to 14.4Sv. The transport increases to 16.3Sv if the additional SAW transport from the western source of SMW (1.9[+ or -]0.7Sv) is included. These transport estimates and the following implications depend strongly on the assumption that the surface water in the Caribbean inflow is of South Atlantic origin. The transport estimates are, however, in the range of the inverse model calculations for the net cross-hemispheric flow. About 30-40% of this transport is intermediate water from the South Atlantic, presumably supporting studies which found the contributions of intermediate and upper warm water to be of a comparable magnitude. For the upper warm water (I.sub.I[cedilla] Author Affiliation: Institut fur Umweltphysik, FB1, Abt. Ozeanographie, Universitat Bremen, Postfach 330 440, D-28334 Bremen, Germany Article History: Received 10 November 2004; Revised 2 May 2005; Accepted 2 August 2005

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2005.01.010 Byline: A. Elmoussaoui, M. Arhan, A.M. Treguier Abstract: The seasonal regime associated with the eastern part of the cyclonic tropical gyre in the North Atlantic is studied using a high-resolution model. The model reproduces a vertical water mass transition (between South and North Atlantic Central Water) previously observed near I.sub.0=26.8, which approximately coincides with the base of the North Equatorial Undercurrent (NEUC). The same density may be taken as the lower limit of the large-scale cyclonic flow. The gyre southern flank is formed of the North Equatorial Countercurrent (NECC) in the near-surface layer, and of the NEUC and deep NECC (when this current is developed) in the Central Water. Its poleward limb is made up from the Ekman drift of the trade winds, a northeastward extension of the NEUC/deep NECC, and reinforced by an extension of the Guinea undercurrent along the African continental slope. Model experiments with two different wind forcings were carried out to estimate the transports across 12[degrees]N, an approximate gyre central latitude. The time-averaged transport for densities lower than I.sub.1=32.3 and to the east of 35[degrees]W is around 4Sv northward, about one-third of the basin-wide net value which measures the Meridional Overturning Circulation. The near-surface layer accounts for about 3Sv, and the Central Water for more than 1Sv, in keeping with the presence of South Atlantic Central Water in the tropical eastern basin. The eastern basin near-surface flow is lowest in summer, when the trade winds nearly vanish at this latitude. In this season the NECC, though having entered its phase of intensification, leaves the region of positive wind stress curl, and temporarily does not act as the tropical gyre southern limb. At the subsurface, most of the NEUC folds up westward at [approximately equal to]10[degrees]N in winter, thus forming an inner circulation of the basin-wide gyre, previously reported from observations. The cyclonic flow associated with the Guinea Dome is another inner circulation, which the model found to be permanent below the surface down to 400-500m, but masked in the Ekman layer, except in summer. Author Affiliation: Laboratoire de Physique des Oceans, CNRS/IFREMER/UBO, Brest, France Article History: Received 15 March 2004; Revised 20 December 2004; Accepted 13 January 2005

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2004.11.005 Byline: Alvaro Peliz (a), Jesus Dubert (a), A. Miguel P. Santos (b), Paulo B. Oliveira (b), Bernard Le Cann (c) Abstract: An overview of the winter circulation and upper ocean structure offshore of Western Iberia is presented. The focus is on winter slope currents, fronts and mesoscale eddies, as well as on the connection of these local features to the large-scale circulation of the region. Satellite sea surface temperature; sea surface elevation data from altimetry; cross-shore and meridional hydrological surveys and current meter observations, mainly obtained during winter periods, are used to illustrate features of the winter upper ocean structure and of the generation and evolution of the Iberia Poleward Current. A schematic/hypothetical model of winter upper ocean circulation on the scale of the Western Iberian Basin is given which attempts to systematize and resolve certain ambiguities in the existing circulation schemes and in the concepts and terminology used to describe observed features in the area. Author Affiliation: (a) Departamento de Fisica (Centro de Estudos do Ambiente e do Mar), Universidade de Aveiro, 3810-194 Aveiro, Portugal (b) Instituto Nacional de Investigacao Agraria e das Pescas-IPIMAR, Av.Brasilia s/n, 1449-006 Lisboa, Portugal (c) Laboratoire de Physique des Oceans, CNRS/IFREMER/UBO, UFR Sciences 6, Av. Le Gorgeu, C.S. 93837, 29238 Brest Cedex 3, France Article History: Received 10 November 2003; Revised 13 August 2004; Accepted 1 November 2004

The authors have used dissolved silicate, oxygen, and a ternary mixing model to distinguish between diagenetic release and remineralization as sources for Antarctic bottom water's silicate concentrations. These data combined with earlier research produce an estimate for deep water silicates and contribute to future estimates of global silicate balance.

The authors describe their discovery of 4 bottom water flows from the Antarctic's Weddell Sea into the Southwest Indian Ocean. These routes include flows through a gap in the Southwest Indian Ridge, two through the Del Cano Rise, and one passing into the Crozet Basin by the Crozet-Kerguelen Gap.

Results show that the oxygen consumption rate by the deep-waters of the Eastern Mediterranean is much higher, which may be due to high temperature conditions prevailing in deep waters. However, the circulation model shows only moderate differences from the previous data.

The oceanic upwelling areas of the Philippine archipelago exhibit unusual cold subsurface temperature rendering them not detectable by satellite imagery. The temperature field data at standard depths, extending up to 500 meter, reveal a change in heat content to be greater than 300 Watts per meter square in upwelling areas.

Research demonstrates that the depletion of the dissolved iodine and enrichment of the surface iodine are associated with nitrate uptake. Data indicate that iodine and nitrate are taken up in definite ratios to each other with almost all the dissolved iodine being exuded as surface iodine.

Tracer-derived 'age' and the transit-time probability density function analyses of oceanic fluid parcels' contact with the surface demonstrate that the former manifests towards the leading part of the latter and the ideal 'age' is more sensitive to the 'tail'.

Determination of vertical velocity for calculating heat and salt exchanges between the ocean surface and interior is presented. Computation of pseudo-synoptic data set gathered from a non-synoptic data set, along with a geostrophic relocation of the stations, corrects the synopticity errors in hydrographic data.

Results demonstrate significant ascending and descending particle fluxes from hydrothermal plumes at all depths and mooring sites off Endeavour Segment, Juan de Fuca Ridge. Data show that the ascending particle organic carbon comes from mid to deep-depth zooplankton and the descending type from the surface of the sea.

The distribution pattern of zooplankton biomass in the Canary Island waters reveal vertical profiles of two sizes, with higher biomass in the shallow layers by night and at a depth of 0-200m by day. The electron transfer system and fluorescence of the biomass are higher by day than in night.

Research demonstrates that the physical variability of the Pacific Ocean spans a wide range of time scales from interannual El Nino conditions to oscillations on a weekly periodicity. These currents affect biological events as revealed by variability in the phytoplankton chlorophyll, zooplankton biomass, rate of primary production, and mineral concentration.

The deep currents in the Northwest Pacific Basin reveal that the currents enter from south in a northward direction along the western boundary at a longitude of 148 degrees E and in the deep passage near a longitude of 170 degrees E, and from the north in the Kamchatka Current.

Research describes hydrography and quantifies transport and flow structure of the Atlantic inflow to the Nordic Seas in both time and space using SeaSoar-CTD and VM-ADCP shipboard equipment. The Norwegian Atlantic current is a two-branched system, eastern and western, with annual mean transport of 4.2Sv and 3.4Sv, respectively.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/S0967-0637(99)00078-3 Byline: Richard J. Greatbatch, Guoqing Li Keywords: Eddy parameterization; Alongslope flow; Climate models; Coastal ocean processes Abstract: We explore a parameterization for mesoscale turbulence, closely related to that of Gent and McWilliams, in which forcing terms proportional to the isopycnal flux of potential vorticity appear in the averaged momentum equations. We show that in the presence of variable bottom topography, the parameterization predicts alongslope mean flow and a corresponding upslope bolus (eddy) flux of tracer that is associated with an alongslope-directed bottom eddy stress. The upslope bolus flux is in qualitative agreement with observations of a cold dome over seamounts. The predicted alongslope flow corresponds to flow fields found in geostrophic turbulence experiments and has some similarity (although conceptually very different, as discussed in the text) to Holloway's prediction based on statistical mechanics. By considering continuous stratification as a limiting case of a multilayer model, we show how to treat the surface and bottom boundaries. Practical application of the parameterization is illustrated using a three-dimensional z-coordinate ocean circulation model that is very similar to the Bryan-Cox-Semtner model. The model-computed flow is consistent with observations of anticyclonic flow around a seamount. We show that the bottom eddy stress associated with the parameterization can be large, even compared to the annual mean surface wind stress, and hence could have important implications for the biology and water mass distribution of the coastal ocean as well as for the large-scale ocean circulation. From the climate modelling perspective, the approach adopted here provides a single formalism that combines the advantages of the Gent and McWilliams parameterization with alongslope mean flow similar to that suggested by Holloway. Article History: Received 6 May 1998; Revised 20 November 1998; Accepted 15 July 1999

The authors discuss direct current measurements carried out in the Kuroshio boundry current of the Pacific Ocean.

The author discusses the development of a model for ocean general circulation and the parameterizing of eddy fluxes.

The authors discuss their investigation of the position of calcite saturation horizon, sedimentary calcite lysocline, and calcium carbonate compensation depth in the South Atlantic Ocean, using planktic foraminifer Globigerina bulloides.

The authors use barium data taken from sediment traps in the Bay of Biscay in evaluating organic carbon transport in the northeast Atlantic margin environment.

The authors discuss data obtained from 94 stations located on the edge and slope of the Iberian Margin relating to particulate matter distributions prior to the seasonal upwelling period.

A study of the effect of the day-night cycle and wind on particle flux in the open waters of Ligurian Sea is discussed. Changes in flux intensity and quality were attributed largely to the transient regime of production from the late-spring bloom to pre-oligotrophy.

The authors discuss day-night variations observed in the size distribution of particulate matter in the Mediterranean Sea. The Underwater Video Profiler, which records objects larger than 0.15 mm within its field of view, was used in the experiment.

A study monitoring the composition and distribution of planktonic ciliates within the surface layer of the Ligurian Sea over four diel cycles is discussed. Variations in total ciliate biomass over each cycle was noted.

The author discusses a four-day study measuring rates of consumption and production of inorganic carbon, nitrate and oxygen by plankton. The study, conducted at a station in the Mediterranean Sea, noted variations in production of carbon and chlorophyll.

A study measuring phytoplankton taxonomic pigment variations in the Mediterranean Sea during the transition from late-spring bloom to pre-oligotrophyic is discussed. Changes in phytoplankton composition and their biogeochemical implications are addressed.

The authors discuss two separate wind events in the Mediterranean Sea observed over a month-long period. The strategies and multi-disciplinary observation methods used in the study are covered, along with an overview of chemical and biological features encountered.

The authors discuss a research study that revealed a consistent drop in the abundance of large particles of marine snow at night. The study was conducted in the upper 100m of the Santa Barbara Channel, California, using an in situ camera.

A year-long study of deep slope currents and particulate matter concentrations on the Barcelona continental margin in the Mediterranean Sea is discussed. Near bottom slope currents in and around the Foix submarine canyon showed the influence of bottom topography.

An experiment to determine the absolute transport of the North Atlantic Current at a location where previous experiments had been conducted is discussed. Flows inshore and offshore the North Atlantic Current were also studied.

The authors discuss methodology and results of a study intended to estimate anthropogenic carbon dioxide levels in the intermediate and deep water of the Labrador Sea region, an area dominated by recently-ventilated water masses.

The authors anyalze the results of study comparing the flux and composition of sinking material caught using two different types of upper ocean sediment traps. The traps were deployed in the Sargasso Sea.

The authors discuss patterns of species diversity in deep-sea benthic foraminifera. Data from five locations in the Atlantic Ocean were used in the analysis.

Data resulting from a study of the interannual variability of nutrients and plankton cycles at a time-series station in the Indian sector of the Antarctic Ocean is discussed.

The authors analyze proposed criteria for determining dense water formation sites, periods and characteristics in the Mediterranean Sea though the use of thermal satellite imagery. Field observations of DWF processes were reviewed.

The author discusses research to determine the concentration of dimethylsulfide in surface seawater at 26 stations in the South China Sea. The relationship between DMS concentration and water temperature, salinity, nutrients and dissolved oxygen was also studied.

The authors use historical data to describe the seasonal cycle of phosphate in the ecosystems of the World's ocean basins, excluding the Arctic and Southern Oceans.

A study was conducted to analyze macrobenthic assemblages in the Toulon Canyon. The assemblages were quantified based on sampling carried out between 250 and 2,000 m depth on the Mediterranean continental slope. Results indicated that the assemblages are characterized by continental shelf eurybathic species. Findings also showed variations in the qualitative and quantitative composition of the population.