scholarly journals High-resolution diapycnal mixing map of the Alboran Sea thermocline from seismic reflection images

2017 ◽  
Author(s):  
Jhon F. Mojica ◽  
Valentí Sallares ◽  
Berta Biescas
Keyword(s):  
High Resolution ◽  
Atlantic Water ◽  
Thermocline Depth ◽  
Alboran Sea ◽  
Diapycnal Mixing ◽  
Acoustic Data ◽  
Mesoscale Structures ◽  
Acoustic Images ◽  
High Resolution Map ◽  
Alborán Sea

Abstract. The Alboran Sea is a dynamically active region where the salty and warm Mediterranean water first encounters the incoming milder and cooler Atlantic water. The interaction between these two water masses originates a set of sub-mesoscale structures and a complex sequence of processes that entail mixing close to the thermocline. Here we present a high-resolution map of the diapycnal diffusivity around the thermocline depth obtained using acoustic data recorded with a high-resolution multichannel seismic system. The map reveals a patchy thermocline, with areas of strong diapycnal mixing juxtaposed with others of weaker mixing. The patch size is of a few kms in the horizontal scale and of 10–15 m in the vertical one. The comparison of the obtained maps with the original acoustic images shows that vigorous mixing tends to occur in areas of internal wave instability, whereas mixing levels in more stable areas is lower. These results are also compared with others obtained using conventional probes. The values obtained using the two methods agree within uncertainty bounds, and they are also consistent with reference theoretical values. Overall, our results demonstrate that high-resolution seismic systems allow to remotely quantify mixing at the thermocline depth with a lateral resolution of O(101 m).

scholarly journals High-resolution diapycnal mixing map of the Alboran Sea thermocline from seismic reflection images

Ocean Science ◽  
2018 ◽  
Vol 14 (3) ◽  
pp. 403-415 ◽  
Author(s):  
Jhon F. Mojica ◽  
Valentí Sallarès ◽  
Berta Biescas
Keyword(s):  
High Resolution ◽  
Atlantic Water ◽  
Thermocline Depth ◽  
Turbulent Regime ◽  
Alboran Sea ◽  
Diapycnal Mixing ◽  
Acoustic Data ◽  
Mesoscale Structures ◽  
High Resolution Map ◽  
Alborán Sea

Abstract. The Alboran Sea is a dynamically active region where the salty and warm Mediterranean water first encounters the incoming milder and cooler Atlantic water. The interaction between these two water masses originates a set of sub-mesoscale structures and a complex sequence of processes that entail mixing close to the thermocline. Here we present a high-resolution map of the diapycnal diffusivity around the thermocline depth obtained using acoustic data recorded with a high-resolution multichannel seismic system. The map reveals a patchy thermocline, with spots of strong diapycnal mixing juxtaposed with areas of weaker mixing. The patch size is of a few kilometers in the horizontal scale and of 10–15 m in the vertical one. The comparison of the obtained maps with the original acoustic images shows that mixing tends to concentrate in areas where internal waves, which are ubiquitous in the surveyed area, become unstable and shear instabilities develop, enhancing energy transfer towards the turbulent regime. These results are also compared with others obtained using more conventional oceanographic probes. The values estimated based on the seismic data are within the ranges of values obtained from oceanographic data analysis, and they are also consistent with reference theoretical values. Overall, our results demonstrate that high-resolution seismic systems allow the remote quantification of mixing at the thermocline depth with unprecedented resolution.

Seafloor characterization and backscatter variability of the Almería Margin (Alboran Sea, SW Mediterranean) based on high-resolution acoustic data

2008 ◽  
Vol 250 (1-2) ◽  
pp. 1-18 ◽  
Author(s):  
Claudio Lo Iacono ◽  
Eulàlia Gràcia ◽  
Susana Diez ◽  
Graziella Bozzano ◽  
Ximena Moreno ◽  
...  
Keyword(s):  
High Resolution ◽  
Alboran Sea ◽  
Acoustic Data ◽  
Seafloor Characterization ◽  
Alborán Sea

scholarly journals Rapid climatic variability in the west Mediterranean during the last 25 000 years from high resolution pollen data

2009 ◽  
Vol 5 (3) ◽  
pp. 503-521 ◽  
Author(s):  
N. Combourieu Nebout ◽  
O. Peyron ◽  
I. Dormoy ◽  
S. Desprat ◽  
C. Beaudouin ◽  
...  
Keyword(s):  
High Resolution ◽  
North Atlantic ◽  
Climate Reconstruction ◽  
Mediterranean Vegetation ◽  
Pollen Record ◽  
Alboran Sea ◽  
Climatic Fluctuations ◽  
The Holocene ◽  
The Mediterranean ◽  
Alborán Sea

Abstract. High-temporal resolution pollen record from the Alboran Sea ODP Site 976, pollen-based quantitative climate reconstruction and biomisation show that changes of Mediterranean vegetation have been clearly modulated by short and long term variability during the last 25 000 years. The reliability of the quantitative climate reconstruction from marine pollen spectra has been tested using 22 marine core-top samples from the Mediterranean. The ODP Site 976 pollen record and climatic reconstruction confirm that Mediterranean environments have a rapid response to the climatic fluctuations during the last Termination. The western Mediterranean vegetation response appears nearly synchronous with North Atlantic variability during the last deglaciation as well as during the Holocene. High-resolution analyses of the ODP Site 976 pollen record show a cooling trend during the Bölling/Allerød period. In addition, this period is marked by two warm episodes bracketing a cooling event that represent the Bölling-Older Dryas-Allerød succession. During the Holocene, recurrent declines of the forest cover over the Alboran Sea borderlands indicate climate events that correlate well with several events of increased Mediterranean dryness observed on the continent and with Mediterranean Sea cooling episodes detected by alkenone-based sea surface temperature reconstructions. These events clearly reflect the response of the Mediterranean vegetation to the North Atlantic Holocene cold events.

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

2016 ◽  
Vol 43 (12) ◽  
pp. 6461-6468 ◽  
Author(s):  
Valenti Sallares ◽  
Jhon F. Mojica ◽  
Berta Biescas ◽  
Dirk Klaeschen ◽  
Eulàlia Gràcia
Keyword(s):  
Spectral Analysis ◽  
High Resolution ◽  
Energy Cascade ◽  
Alboran Sea ◽  
Alborán Sea

Analysis of Vertical Velocities Development through High-resolution Simulation and Glider Observations in the Alboran Sea

2021 ◽  
Author(s):  
Maximo Garcia-Jove ◽  
Baptiste Mourre ◽  
Nikolaos Zarokanellos ◽  
Pierre F. J. Lermusiaux ◽  
Daniel L. Rudnick ◽  
...  
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Naval Research ◽  
Alboran Sea ◽  
Surface Ocean ◽  
Office Of Naval Research ◽  
Research Initiative ◽  
Spatio Temporal ◽  
Alborán Sea ◽  
Resolution Simulation

<p>Vertical velocities associated with meso- and submeso-scale structures generate important vertical fluxes of carbon and other biogeochemical tracers from the surface layer to depths below the mixed layer. Vertical velocities are very weak and characterized by small scales which make them difficult to measure. The project entitled Coherent Lagrangian Pathways from the Surface Ocean to Interior (CALYPSO, Office of Naval Research initiative) addresses the challenge of observing, understanding, and predicting the vertical velocities and three-dimensional pathways on subduction processes in the frontal regions of the Alboran Sea. Within the framework of the CALYPSO project, we analysed the processes that give rise to vertical velocities in the Western Alboran Gyre Front (WAGF) and Eastern Alboran Gyre Front (EAGF). The periods of frontal intensification were analyzed in the perspective of the frontogenesis, instabilities, non-linear Ekman effects, and filamentogenesis using multi-platform in-situ observations and a high-resolution simulation in spring 2018. The spatio-temporal characteristics of the WAGF indicate a wider, deeper, and longer-lasting front than the EAGF. The WAGF intensification and vertical velocities development are explained through i) frontogenesis, ii) conditions for symmetric and ageostrophic baroclinic instabilities generation, and iii) nonlinear Ekman effects. These mechanisms participate to generate and strengthen an ageostrophic secondary circulation responsible for vertical velocities intensification in the front. In the case of the EAGF, the intensification and vertical velocities development are explained by filamentogenesis in both the model and glider observations. The EAGF intensification is characterized by a sharp and outcropping density gradient at the center of the filament, where two asymmetrical ageostrophic cells develop across the front with narrow upwelling region in the middle.</p>

Revision of the Alboran sea Tortonian-Pliocene record: possible new insights on Mediterranean-Atlantic connectivity during the Messinian Salinity Crises

2020 ◽  
Author(s):  
Francesca Bulian ◽  
Francisco J. Sierro
Keyword(s):  
Mediterranean Sea ◽  
High Amplitude ◽  
Atlantic Water ◽  
Time Interval ◽  
Alboran Sea ◽  
Base Level ◽  
Open Questions ◽  
Gibraltar Strait ◽  
The Mediterranean ◽  
Alborán Sea

<p>In August of 1970, during Mediterranean Sea Leg 13, when the Glomar challenger ventured Mediterranean waters, nobody was expecting to run into one of the most exiting scientific discoveries regarding the Mediterranean Sea evolution. Cores and seismic surveys made possible the discovery of a basin-wide Messinian evaporitic deposit buried beneath the deep-sea Pliocene sediments which was attributed to the Messinian Salinity Crises (MSC) already known and studied in onshore outcrops in the Apennines. Now, 50 years later the debate regarding the conditions and timing of the deposition of this salt giant is still ongoing as many theories are still open and in search for validating proof.</p><p>One of the main open questions certainly regards the base level drop during the MSC and the location, efficiency and dynamics of the Mediterranean – Atlantic connectivity. The Mediterranean level is thought to have dropped somewhere between a moderate 200 m up to an extreme high amplitude oscillation of 1500 m while according to different schools of thought the watergate to the Atlantic is considered as completely closed, intermittently open or to have been always open during the MSC. Gibraltar strait is the main candidate for a possible gateway during this time interval (5.96-5.33 Ma) as well as the leading cause of the re-establishment of open marine conditions in the Mediterranean. Consequently, understanding its evolution and opening is fundamental to endorse any of the MSC theories and a thorough investigation of the Messinian and early Pliocene sedimentological record of basins in its proximity is highly needed.</p><p>In this optic, the Alboran Sea is the place where many of those answers lie and its worth of further exploration. In the hope of a new oceanographic expedition in the near future, an effort should be made towards gathering and re-interpreting all the available data. We propose a refined planktonic foraminifer chronology of the Alboran DSDP and ODP sites 976B, 121 and 978A with a careful characterization of the main MSC facies that will clarify to a certain extent the MSC expression and the degree of Atlantic water influence in the Alboran basin.</p><p> </p>

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