Large- to submesoscale surface circulation and its implications on biogeochemical/biological horizontal distributions during the OUTPACE cruise (southwest Pacific)

Abstract. The patterns of the large-scale, meso- and submesoscale surface circulation on biogeochemical and biological distributions are examined in the western tropical South Pacific (WTSP) in the context of the OUTPACE cruise (February–April 2015). Multi-disciplinary original in situ observations were achieved along a zonal transect through the WTSP and their analysis was coupled with satellite data. The use of Lagrangian diagnostics allows for the identification of water mass pathways, mesoscale structures, and submesoscale features such as fronts. In particular, we confirmed the existence of a global wind-driven southward circulation of surface waters in the entire WTSP, using a new high-resolution altimetry-derived product, validated by in situ drifters, that includes cyclogeostrophy and Ekman components with geostrophy. The mesoscale activity is shown to be responsible for counter-intuitive water mass trajectories in two subregions: (i) the Coral Sea, with surface exchanges between the North Vanuatu Jet and the North Caledonian Jet, and (ii) around 170∘ W, with an eastward pathway, whereas a westward general direction dominates. Fronts and small-scale features, detected with finite-size Lyapunov exponents (FSLEs), are correlated with 25 % of surface tracer gradients, which reveals the significance of such structures in the generation of submesoscale surface gradients. Additionally, two high-frequency sampling transects of biogeochemical parameters and microorganism abundances demonstrate the influence of fronts in controlling the spatial distribution of bacteria and phytoplankton, and as a consequence the microbial community structure. All circulation scales play an important role that has to be taken into account not only when analysing the data from OUTPACE but also, more generally, for understanding the global distribution of biogeochemical components.

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Large to submesoscale surface circulation and its implications on biogeochemical/biological horizontal distributions during the OUTPACE cruise (SouthWest Pacific)

10.5194/bg-2017-456 ◽

2017 ◽

Cited By ~ 1

Author(s):

Louise Rousselet ◽

Alain de Verneil ◽

Andrea M. Doglioli ◽

Anne A. Petrenko ◽

Solange Duhamel ◽

...

Keyword(s):

Large Scale ◽

Water Mass ◽

Finite Size ◽

Small Scale ◽

General Direction ◽

The North ◽

Mesoscale Structures ◽

Surface Circulation ◽

Biogeochemical Parameters

Abstract. The patterns of the large-scale, meso- and submesoscale surface circulation on biogeochemical and biological distributions are examined in the Western Tropical South Pacific (WTSP) in the context of the OUTPACE cruise (Feb–April 2015). Multi-disciplinary original in situ observations were achieved along a zonal transect through the WTSP and their analysis was coupled with satellite data. The use of Lagrangian diagnostics allows for the identification of water mass pathways, mesoscale structures, and submesoscale features such as fronts. In particular, we confirmed the existence of a global wind-driven southward circulation of surface waters in the entire WTSP, using a new high-resolution altimetry-derived product, validated by in situ drifters, that includes cyclogeostrophy and Ekman components with geostrophy. Two subregions show counter-intuitive water mass trajectories due to mesoscale circulation: i) the Coral Sea with surface exchanges between the North Vanuatu Jet and the North Caledonian Jet; and ii) the zonal band between 180° W and 170° W with an eastward propagation whereas a westward general direction dominates. Fronts and small-scale features, detected with Finite-Size Lyapunov Exponents (FSLE), are correlated with 25 % of surface tracer gradients which reveals the significance of such structures in the generation of submesoscale surface gradients. Additionally, two high-frequency sampling transects of biogeochemical parameters and micro-organism abundances demonstrate the influence of fronts in controlling the spatial distribution of bacteria and phytoplankton, and as a consequence the microbial community structure. All circulation scales play an important role that has to be taken into account when analysing the data from OUTPACE but also, more generally, to understand the global distribution of biogeochemical components.

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Daily to annual net primary production in the North Sea determined using autonomous underwater gliders and satellite Earth observation

10.5194/essd-2021-311 ◽

2021 ◽

Author(s):

Benjamin Loveday ◽

Timothy Smyth ◽

Anıl Akpinar ◽

Tom Hull ◽

Mark Inall ◽

...

Keyword(s):

Time Series ◽

Primary Production ◽

North Sea ◽

Large Scale ◽

Net Primary Production ◽

Earth Observation ◽

Small Scale ◽

The North ◽

The North Sea

Abstract. Shelf-seas play a key role in both the global carbon cycle and coastal marine ecosystems through the drawn-down and fixing of carbon, as measured through phytoplankton net primary production (NPP). Measuring NPP in situ, and extrapolating this to the local, regional and global scale presents challenges however because of limitations with the techniques utilised (e.g. radiocarbon isotopes), data sparsity and the inherent biogeochemical heterogeneity of coastal and open-shelf waters. Here, we introduce a powerful new technique based on the synergistic use of in situ glider profiles and satellite Earth Observation measurements which can be implemented in a real-time or delayed mode system. We apply this system to a fleet of gliders successively deployed over a 19-month time-frame in the North Sea, generating an unprecedented fine scale time-series of NPP in the region (Loveday and Smyth, 2020). At the large-scale, this time-series gives close agreement with existing satellite-based estimates of NPP for the region and previous in situ estimates. What has not been elucidated before is the high-frequency, small-scale, depth-resolved variability associated with bloom phenology, mesoscale phenomena and mixed layer dynamics.

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Coupled Thermo-Hydro-Geochemical Models of Engineered Barrier Systems: The Febex Project

MRS Proceedings ◽

10.1557/proc-663-561 ◽

2000 ◽

Vol 663 ◽

Cited By ~ 2

Author(s):

J. Samper ◽

R. Juncosa ◽

V. Navarro ◽

J. Delgado ◽

L. Montenegro ◽

...

Keyword(s):

Large Scale ◽

Reference Model ◽

Numerical Models ◽

Full Scale ◽

Small Scale ◽

Model Parameters ◽

In Situ Test ◽

Wide Range ◽

Engineered Barrier

ABSTRACTFEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of waste in a high level radioactive waste repository (HLWR). It includes two main experiments: an situ full-scale test performed at Grimsel (GTS) and a mock-up test operating since February 1997 at CIEMAT facilities in Madrid (Spain) [1,2,3]. One of the objectives of FEBEX is the development and testing of conceptual and numerical models for the thermal, hydrodynamic, and geochemical (THG) processes expected to take place in engineered clay barriers. A significant improvement in coupled THG modeling of the clay barrier has been achieved both in terms of a better understanding of THG processes and more sophisticated THG computer codes. The ability of these models to reproduce the observed THG patterns in a wide range of THG conditions enhances the confidence in their prediction capabilities. Numerical THG models of heating and hydration experiments performed on small-scale lab cells provide excellent results for temperatures, water inflow and final water content in the cells [3]. Calculated concentrations at the end of the experiments reproduce most of the patterns of measured data. In general, the fit of concentrations of dissolved species is better than that of exchanged cations. These models were later used to simulate the evolution of the large-scale experiments (in situ and mock-up). Some thermo-hydrodynamic hypotheses and bentonite parameters were slightly revised during TH calibration of the mock-up test. The results of the reference model reproduce simultaneously the observed water inflows and bentonite temperatures and relative humidities. Although the model is highly sensitive to one-at-a-time variations in model parameters, the possibility of parameter combinations leading to similar fits cannot be precluded. The TH model of the “in situ” test is based on the same bentonite TH parameters and assumptions as for the “mock-up” test. Granite parameters were slightly modified during the calibration process in order to reproduce the observed thermal and hydrodynamic evolution. The reference model captures properly relative humidities and temperatures in the bentonite [3]. It also reproduces the observed spatial distribution of water pressures and temperatures in the granite. Once calibrated the TH aspects of the model, predictions of the THG evolution of both tests were performed. Data from the dismantling of the in situ test, which is planned for the summer of 2001, will provide a unique opportunity to test and validate current THG models of the EBS.

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On the short-term variability of turbulence and temperature in the winter mesosphere

Annales Geophysicae ◽

10.5194/angeo-36-1099-2018 ◽

2018 ◽

Vol 36 (4) ◽

pp. 1099-1116

Author(s):

Gerald A. Lehmacher ◽

Miguel F. Larsen ◽

Richard L. Collins ◽

Aroh Barjatya ◽

Boris Strelnikov

Keyword(s):

Attitude Control ◽

Large Scale ◽

Lower Thermosphere ◽

Density Fluctuations ◽

Large Temperature ◽

Small Scale ◽

Spatial And Temporal Variability ◽

Temperature Structure ◽

Wind Shears

Abstract. Four mesosphere–lower thermosphere temperature and turbulence profiles were obtained in situ within ∼30 min and over an area of about 100 by 100 km during a sounding rocket experiment conducted on 26 January 2015 at Poker Flat Research Range in Alaska. In this paper we examine the spatial and temporal variability of mesospheric turbulence in relationship to the static stability of the background atmosphere. Using active payload attitude control, neutral density fluctuations, a tracer for turbulence, were observed with very little interference from the payload spin motion, and with high precision (<0.01 %) at sub-meter resolution. The large-scale vertical temperature structure was very consistent between the four soundings. The mesosphere was almost isothermal, which means more stratified, between 60 and 80 km, and again between 88 and 95 km. The stratified regions adjoined quasi-adiabatic regions assumed to be well mixed. Additional evidence of vertical transport and convective activity comes from sodium densities and trimethyl aluminum trail development, respectively, which were both observed simultaneously with the in situ measurements. We found considerable kilometer-scale temperature variability with amplitudes of 20 K in the stratified region below 80 km. Several thin turbulent layers were embedded in this region, differing in width and altitude for each profile. Energy dissipation rates varied between 0.1 and 10 mW kg−1, which is typical for the winter mesosphere. Very little turbulence was observed above 82 km, consistent with very weak small-scale gravity wave activity in the upper mesosphere during the launch night. On the other hand, above the cold and prominent mesopause at 102 km, large temperature excursions of +40 to +70 K were observed. Simultaneous wind measurements revealed extreme wind shears near 108 km, and combined with the observed temperature gradient, isolated regions of unstable Richardson numbers (0<Ri<0.25) were detected in the lower thermosphere. The experiment was launched into a bright auroral arc under moderately disturbed conditions (Kp∼5).

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Equilibria and condensates in Rossby and drift wave turbulence

Journal of Physics A Mathematical and Theoretical ◽

10.1088/1751-8121/ac3946 ◽

2021 ◽

Author(s):

Jonathan Skipp ◽

Sergey Nazarenko

Keyword(s):

Large Scale ◽

Finite Size ◽

Small Scale ◽

Simple Explanation ◽

Weakly Nonlinear ◽

Zonal Flows ◽

Drift Wave Turbulence ◽

Third Invariant ◽

Thermodynamic Potentials ◽

Singular Limits

Abstract We study the thermodynamic equilibrium spectra of the Charney- Hasegawa-Mima (CHM) equation in its weakly nonlinear limit. In this limit, the equation has three adiabatic invariants, in contrast to the two invariants of the 2D Euler or Gross-Pitaevskii equations, which are examples for comparison. We explore how the third invariant considerably enriches the variety of equilibrium spectra that the CHM system can access. In particular we characterise the singular limits of these spectra in which condensates occur, i.e. a single Fourier mode (or pair of modes) accumulate(s) a macroscopic fraction of the total invariants. We show that these equilibrium condensates provide a simple explanation for the characteristic structures observed in CHM systems of finite size: highly anisotropic zonal flows, large-scale isotropic vortices, and vortices at small scale. We show how these condensates are associated with combinations of negative thermodynamic potentials (e.g. temperature).

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Internal tide energy flux over a ridge measured by a co-located ocean glider and moored ADCP

10.5194/os-2019-15 ◽

2019 ◽

Author(s):

Rob Hall ◽

Barbara Berx ◽

Gillian Damerell

Keyword(s):

Energy Flux ◽

Large Scale ◽

Low Frequency ◽

Internal Tide ◽

Small Scale ◽

Potential Density ◽

The North ◽

Model Study ◽

Continental Shelves ◽

Alternative Approach

Abstract. Internal tide energy flux is an important diagnostic for the study of energy pathways in the ocean, from large-scale input by the surface tide, to small-scale dissipation by turbulent mixing. Accurate calculation of energy flux requires repeated full-depth measurements of both potential density (ρ) and horizontal current velocity (u) over at least a tidal cycle and over several weeks to resolve the internal spring-neap cycle. Typically, these observations are made using full-depth oceanographic moorings that are vulnerable to being fished-out by commercial trawlers when deployed on continental shelves and slopes. Here we test an alternative approach to minimise these risks, with u measured by a low-frequency ADCP moored near the seabed and ρ measured by an autonomous ocean glider holding station by the ADCP. The method is used to measure the M2 internal tide radiating from the Wyville Thompson Ridge in the North Atlantic. The observed energy flux (4.2 ± 0.2 kW m−1) compares favourably with historic observations and a previous numerical model study. Error in the energy flux calculation due to imperfect co-location of the glider and ADCP is estimated by sub-sampling potential density in an idealised internal tide field along pseudorandomly distributed glider paths. The error is considered acceptable (

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Monitoring the Influence of the Mesoscale Ocean Dynamics on Phytoplanktonic Plumes around the Marquesas Islands Using Multi-Satellite Missions

Remote Sensing ◽

10.3390/rs12162520 ◽

2020 ◽

Vol 12 (16) ◽

pp. 2520 ◽

Cited By ~ 1

Author(s):

Angelina Cassianides ◽

Elodie Martinez ◽

Christophe Maes ◽

Xavier Carton ◽

Thomas Gorgues

Keyword(s):

Finite Size ◽

Ocean Dynamics ◽

Dynamic Activity ◽

Marquesas Islands ◽

The North ◽

Run Off ◽

Dynamical Regimes ◽

North And South

The Marquesas islands are a place of strong phytoplanktonic enhancement, whose original mechanisms have not been explained yet. Several mechanisms such as current−bathymetry interactions or island run-off can fertilize waters in the immediate vicinity or downstream of the islands, allowing phytoplankton enhancement. Here, we took the opportunity of an oceanographic cruise carried out at the end of 2018, to combine in situ and satellite observations to investigate two phytoplanktonic blooms occurring north and south of the archipelago. First, Lagrangian diagnostics show that both chlorophyll-a concentrations (Chl) plumes are advected from the islands. Second, the use of Finite-size Lyaponov Exponent and frontogenesis diagnostics reveal how the Chl plumes are shaped by the passage of a mesoscale cyclonic eddy in the south and by a converging front and finer-scale dynamic activity in the north. Our results based on these observations provide clues to the hypothesis of a fertilization from the islands themselves allowing phytoplankton to thrive. They also highlight the role of advection to disperse and shape the Chl plumes in two regions with contrasting dynamical regimes.

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Characteristics of shallow thermally driven flow in the complex topography of the south-eastern Adriatic

Annales Geophysicae ◽

10.5194/angeo-28-1905-2010 ◽

2010 ◽

Vol 28 (10) ◽

pp. 1905-1922 ◽

Cited By ~ 4

Author(s):

M. T. Prtenjak ◽

I. Tomažić ◽

I. Kavčič ◽

S. Đivanović

Keyword(s):

Large Scale ◽

Sea Breeze ◽

Small Scale ◽

The South ◽

Fine Grid ◽

Easterly Wind ◽

Sodar Data ◽

South Eastern ◽

The North ◽

Convergence Zones

Abstract. Characteristics of thermally induced flow, namely the sea breeze, are investigated along the south-eastern Adriatic. The chosen period 24–25 April 2006 favoured sea breeze development and simultaneously allowed a comparison of the large-scale wind influence (north-westerly wind versus south-easterly wind) and the complex terrain on the local circulations. Particular attention is paid to the small-scale formation of the wind field, convergence zones (CZs), channelling flows and small scale eddies, especially in the vicinity of two airports in the central part of south-eastern Adriatic. The results are based on wind measurements (from meteorological surface stations, radiosoundings, satellite data and sodar data) and further supplemented by model data at fine grid spacing. This study shows the formation of numerous irregular daytime and nighttime CZs, which occurred along the coastline in the lee of mountains and over the larger, elongated islands. The results show that the above mentioned airports are surrounded by daytime CZ formations within the lowermost 1000 m and associated updrafts of 1 m s−1, especially if CZs are maintained by the north-westerly large-scale winds. Whereas the daytime CZ was generated due to merged sea breezes, the weaker and shallower nighttime CZs were formed by wind convergence of the seaward breezes, and significantly modified by the large-scale flow of the topography (e.g., accelerated flow in the sea channels and substantial swirled flows around the islands). The passes between the coastal mountain peaks changed the inflow penetration, provoking the increase in wind speed of the channelled flow. The strongest sea breeze channelling was observed above the valley of the Neretva River, where the onshore flow reached 40 km inland with a strength of 8 m s−1, and the highly asymmetric offshore part was confined within the sea channel.

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Magnetospheric Processes Possibly Related to the Origin of Cosmic Rays

Symposium - International Astronomical Union ◽

10.1017/s0074180900074921 ◽

1981 ◽

Vol 94 ◽

pp. 373-391

Author(s):

Gerhard Haerendel

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Small Scale ◽

Shear Stresses ◽

Acceleration Process ◽

Dayside Magnetopause ◽

Field Lines ◽

The Magnetic Field ◽

Auroral Particles

Two processes are discussed which violate the frozen-in condition in a highly conducting plasma, reconnection and the auroral acceleration process. The first applies to situations in which . It plays an important role in the interaction of the solar wind with the Earth's magnetic field and controls energy input into as well as energetic particle release from the magnetosphere. Detailed in situ studies of the process on the dayside magnetopause reveal its transient and small-scale nature. The auroral acceleration process occurs in the low magnetosphere (β « 1) and accompanies sudden releases of magnetic shear stresses which exist in large-scale magnetospheric-ionospheric current circuits. The process is interpreted as a kind of breaking. The movements of the magnetospheric plasma which lead to a relief of the magnetic tensions occur in thin sheets and are decoupled along the magnetic field lines by parallel electric potential drops. It is this voltage that accelerates the primary auroral particles. The visible arcs are then traces of the magnetic breaking process at several 1000 km altitude.

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On the Variability of the Circulation and Water Mass Properties in the Eastern Levantine Sea between September 2016–August 2017

Water ◽

10.3390/w11091741 ◽

2019 ◽

Vol 11 (9) ◽

pp. 1741 ◽

Cited By ~ 5

Author(s):

Mauri ◽

Sitz ◽

Gerin ◽

Poulain ◽

Hayes ◽

...

Keyword(s):

High Salinity ◽

Autonomous Systems ◽

Vertical Mixing ◽

The North ◽

Levantine Sea ◽

Surface Circulation ◽

Basin Scale ◽

Geographical Position ◽

Surface Drifters

The surface circulation and the thermohaline properties of the water masses of the eastern Levantine Sea (Mediterranean Sea) were monitored with mobile autonomous systems (surface drifters and gliders) during the period September 2016–August 2017. The drifters provided data for more than a year and revealed complex circulation features at scales ranging from the basin scale to the sub-mesoscale. Three drifters were captured in a semi-permanent gyre (Cyprus Eddy) allowing a quantitative study of its kinematics. During the experiment, three gliders were operated, in two different periods: September to December 2016 and February to March 2017. The autonomous instruments crossed the prevailing sub-basin structures several times. The collected in-situ observations were analyzed and interpreted in concert with remote sensing products (sea surface temperature and altimetry). The evolution of some of the prevailing features confirmed the complexity of the circulation of the basin. The Cyprus Eddy is the most persistent anticyclone, moving its geographical position and sometimes merging with the North Shikmona Eddy in a bigger structure. The gliders sampled this wide anticyclonic feature revealing its vertical structure in the two different periods. In fall, in stratified conditions, a high salinity core is evident below the thermocline. The isopycnals are characterized by an upward bending over the high salinity lens and a downward bending below it, typical of an anticyclonic modewater eddy. In winter, the core disappears following the vertical mixing that, homogenizes the upper Cyprus Eddy water down to 300 m.

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