Extreme winter 2012 in the Adriatic: an example of climatic effect on the BiOS rhythm

Abstract. Adriatic and Ionian seas are Mediterranean sub-basins linked through the Bimodal Oscillating System mechanism responsible for decadal reversals of the Ionian basin-wide circulation. Altimetric maps showed that the last cyclonic mode started in 2011 but unexpectedly in 2012 reversed to anticyclonic. We related this "premature" inversion to the extremely strong winter in 2012, which caused the formation of very dense Adriatic waters, flooding Ionian flanks in May and inverting the bottom pressure gradient. Using Lagrangian float measurements, the linear regression between the sea surface height and three isopycnal depths suggests that the southward deep-layer flow coincided with the surface northward geostrophic current and the anticyclonic circulation regime. Density variations at depth in the northwestern Ionian revealed the arrival of Adriatic dense waters in May and maximum density in September. Comparison between the sea level height in the northwestern Ionian and in the basin centre showed that in coincidence with the arrival of the newly formed Adriatic dense waters the sea level was lowered in the northwestern flank, inverting the surface pressure gradient. Toward the end of 2012, the density gradient between the basin flanks and its centre went to zero, coinciding with the weakening of the anticyclonic circulation and eventually with its return to the cyclonic pattern. Thus, the premature and transient reversal of Ionian surface circulation originated from the extremely harsh winter in the Adriatic, resulting in the formation and spreading of highly dense bottom waters. The present study highlights the remarkable sensitiveness of the Adriatic–Ionian BiOS to climatic forcing.

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Extreme winter 2012 in the Adriatic: an example of climatic effect on the BiOS rhythm

Ocean Science Discussions ◽

10.5194/osd-11-425-2014 ◽

2014 ◽

Vol 11 (1) ◽

pp. 425-452 ◽

Cited By ~ 2

Author(s):

M. Gačić ◽

G. Civitarese ◽

V. Kovačević ◽

L. Ursella ◽

M. Bensi ◽

...

Keyword(s):

Pressure Gradient ◽

Sea Level ◽

Bottom Pressure ◽

Climatic Effect ◽

Climatic Forcing ◽

The North ◽

Surface Circulation ◽

Bottom Waters ◽

Layer Flow ◽

North Western

Abstract. Adriatic and Ionian Seas are Mediterranean sub-basins linked through the Bimodal Oscillating System mechanism responsible for decadal reversals of the Ionian basin-wide circulation. Altimetric maps showed that the last cyclonic mode started in 2011 but unexpectedly in 2012 reversed to anticyclone. We related this "premature" inversion to extremely strong winter in 2012, which caused the formation of very dense Adriatic waters, flooding Ionian flanks in May and inverting the bottom pressure gradient. Using Lagrangian float measurements, the linear regression between the sea surface height and three isopycnal depths suggests that the southward deep-layer flow coincided with the surface northward geostrophic current and the anti-cyclonic circulation regime. Density variations at depth in the north-western Ionian revealed the arrival of Adriatic dense waters in May and maximum density in September. Comparison between the sea level height in the north-western Ionian and in the basin centre showed that in coincidence with the arrival of the newly formed Adriatic dense waters the sea level lowered in the north-western flank inverting the surface pressure gradient. Toward the end of 2012, the density gradient between the basin flanks and its centre went to zero, coinciding with the weakening of the anticyclonic circulation and eventually with its return to the cyclonic pattern. Thus, the premature and transient reversal of Ionian surface circulation originated from the extremely harsh winter in the Adriatic, resulting in the formation and spreading of highly dense bottom waters. The present study highlights the remarkable sensitiveness of the Adriatic–Ionian BiOS to climatic forcing.

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Numerical simulation of supersonic turbulent boundary layer flow with mild pressure gradient

10.2514/6.1996-2059 ◽

1996 ◽

Author(s):

E. Fick ◽

D. Gaitonde ◽

T. Buter

Keyword(s):

Numerical Simulation ◽

Boundary Layer ◽

Turbulent Boundary Layer ◽

Pressure Gradient ◽

Boundary Layer Flow ◽

Turbulent Boundary Layer Flow ◽

Layer Flow

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Bottom Pressure and Sea Level Measurements in the Gulf of Lions

Journal of Physical Oceanography ◽

10.1175/1520-0485(1981)011<0394:bpaslm>2.0.co;2 ◽

1981 ◽

Vol 11 (3) ◽

pp. 394-409 ◽

Cited By ~ 14

Author(s):

A. Lamy ◽

C. Millot ◽

J. M. Molines

Keyword(s):

Sea Level ◽

Bottom Pressure ◽

Gulf Of Lions ◽

And Sea Level

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Compressibility Effects on the Extended Crocco Relation and the Thermal Recovery Factor in Laminar Boundary Layer Flow

Journal of Fluids Engineering ◽

10.1115/1.1637626 ◽

2004 ◽

Vol 126 (1) ◽

pp. 32-41 ◽

Cited By ~ 8

Author(s):

B. W. van Oudheusden

Keyword(s):

Boundary Layer ◽

Prandtl Number ◽

Pressure Gradient ◽

Boundary Layer Flow ◽

Numerical Solutions ◽

Thermal Recovery ◽

Recovery Factor ◽

Perturbation Approach ◽

Layer Flow ◽

Compressibility Effects

The relation between velocity and enthalpy in steady boundary layer flow is known as the Crocco relation. It describes that for an adiabatic wall the total enthalpy remains constant throughout the boundary layer, when the Prandtl number (Pr) is one, irrespective of pressure gradient and compressibility. A generalization of the Crocco relation for Pr near one is obtained from a perturbation approach. In the case of constant-property flow an analytic expression is found, representing a first-order extension of the standard Crocco relation and confirming the asymptotic validity of the square-root dependence of the recovery factor on Prandtl number. The particular subject of the present study is the effect of compressibility on the extended Crocco relation and, hence, on the thermal recovery in laminar flows. A perturbation analysis for constant Pr reveals two additional mechanisms of compressibility effects in the extended Crocco relation, which are related to the viscosity law and to the pressure gradient. Numerical solutions for (quasi-)self-similar as well as non-similar boundary layers are presented to evaluate these effects quantitatively.

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Clay mineral distribution related to rift activity, sea-level changes and paleoceanography in the Cretaceous of the Atlantic Ocean

Clay Minerals ◽

10.1180/claymin.1993.028.1.07 ◽

1993 ◽

Vol 28 (1) ◽

pp. 61-84 ◽

Cited By ~ 51

Author(s):

M. Thiry ◽

T. Jacquin

Keyword(s):

Atlantic Ocean ◽

Sea Level ◽

Clay Minerals ◽

Clay Mineral ◽

Deep Sea ◽

Depositional Environments ◽

Sea Level Changes ◽

Sea Floor ◽

Deep Sea Sediments ◽

Bottom Waters

AbstractThe distribution of clay minerals from the N and S Atlantic Cretaceous deep-sea sediments is related to rifting, sea-floor spreading, sea-level variations and paleoceanography. Four main clay mineral suites were identified: two are inherited and indicative of ocean geodynamics, whereas the others result from transformation and authigenesis and are diagnostic of Cretaceous oceanic depositional environments. Illite and chlorite, together with interstratified illite-smectite and smectite occur above the sea-floor basalts and illustrate the contribution of volcanoclastic materials of basaltic origin to the sediments. Kaolinite, with variable amounts of illite, chlorite, smectite and interstratified minerals, indicates detrital inputs from continents near the platform margins. Kaolinite decreases upward in the series due to open marine environments and basin deepening. It may increase in volume during specific time intervals corresponding to periods of falling sea-level during which overall facies regression and erosion of the surrounding platforms occurred. Smectite is the most abundant clay mineral in the Cretaceous deep-sea sediments. Smectite-rich deposits correlate with periods of relatively low sedimentation rates. As paleoweathering profiles and basal deposits at the bottom of Cretaceous transgressive formations are mostly kaolinitic, smectite cannot have been inherited from the continents. Smectite is therefore believed to have formed in the ocean by transformation and recrystallization of detrital materials during early diagenesis. Because of the slow rate of silicate reactions, transformation of clay minerals requires a long residence time of the particles at the water/sediment interface; this explains the relationships between the observed increases in smectite with long-term sea-level rises that tend to starve the basinal settings of sedimentation. Palygorskite, along with dolomite, is relatively common in the N and S Atlantic Cretaceous sediments. It is not detrital because correlative shelf deposits are devoid of palygorskite. Palygorskite is diagnostic of Mg-rich environments and is indicative of the warm and hypersaline bottom waters of the Cretaceous Atlantic ocean.

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Solving the Nonlinear Boundary Layer Flow Equations with Pressure Gradient and Radiation

Symmetry ◽

10.3390/sym12050710 ◽

2020 ◽

Vol 12 (5) ◽

pp. 710

Author(s):

Michalis A. Xenos ◽

Eugenia N. Petropoulou ◽

Anastasios Siokis ◽

U. S. Mahabaleshwar

Keyword(s):

Boundary Layer ◽

Partial Differential Equations ◽

Differential Equations ◽

Pressure Gradient ◽

Boundary Layer Flow ◽

Mathematical Formulation ◽

Dimensionless Temperature ◽

Partial Differential ◽

Analytical Results ◽

Layer Flow

The physical problem under consideration is the boundary layer problem of an incompressible, laminar flow, taking place over a flat plate in the presence of a pressure gradient and radiation. For the mathematical formulation of the problem, the partial differential equations of continuity, energy, and momentum are taken into consideration with the boundary layer simplifications. Using the dimensionless Falkner–Skan transformation, a nonlinear, nonhomogeneous, coupled system of partial differential equations (PDEs) is obtained, which is solved via the homotopy analysis method. The obtained analytical solution describes radiation and pressure gradient effects on the boundary layer flow. These analytical results reveal that the adverse or favorable pressure gradient influences the dimensionless velocity and the dimensionless temperature of the boundary layer. An adverse pressure gradient causes significant changes on the dimensionless wall shear parameter and the dimensionless wall heat-transfer parameter. Thermal radiation influences the thermal boundary layer. The analytical results are in very good agreement with the corresponding numerical ones obtained using a modification of the Keller’s-box method.

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Seasonal Variation of Surface Circulation Along Peninsular Malaysia' East Coast

Jurnal Teknologi ◽

10.11113/jt.v71.3823 ◽

2014 ◽

Vol 71 (4) ◽

Author(s):

Muhammad Faiz Pa'suya ◽

Kamaludin Mohd Omar ◽

Benny N. Peter ◽

Ami Hassan Md Din ◽

Mohd Fadzil Mohd Akhir

Keyword(s):

Sea Level ◽

East Coast ◽

Peninsular Malaysia ◽

Environmental Data ◽

Sea Surface ◽

Northeast Monsoon ◽

Radar Altimeter ◽

Sea Level Anomaly ◽

Surface Circulation ◽

Altimetric Data

The sea surface circulation pattern over the coast of Peninsula Malaysia's East Coast during Northeast Monsoon (NE) and Southwest Monsoon (SW) are derived using the seasonally averaged sea level anomaly (SLA) data from altimetric data and 1992-2002 Mean Dynamic Ocean Topography. This altimetric data has been derived from multi-mission satellite altimeter TOPEX, ERS-1, ERS-2, JASON-1, and ENVISAT for the period of nineteen years (1993 to 2011) using the Radar Altimeter Database System (RADS). The estimated sea level anomaly (SLA) have shown similarity in the pattern of sea level variations observed by four tide gauges. Overall, the sea surface circulations during the NE and SW monsoons shows opposite patterns, northward and southward respectively. During the SW monsoon, an anti-cyclonic circulation has been detected around the Terengganu coastal area centred at (about 5.5° N 103.5° E) and nearly consistent with previous study using numerical modelling. The estimated geostrophic current field from the altimeter is consistent with the trajectories of Argos-tracked Drifting Buoys provided by the Marine Environmental Data Services (MEDS) in Canada.

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