Papers by Mikhail Emelianov
We have pursued, in Parts 1 and 2, the re-analysis of the 1985-1986 GIBEX CTD data we initiated i... more We have pursued, in Parts 1 and 2, the re-analysis of the 1985-1986 GIBEX CTD data we initiated in the mid 2000's with a focus on the Mediterranean Outflow (MO) heterogeneity. At the Strait entrance (Part 1), a transect (5°40'W) and a yo-yo time series (5°43'W) show Mediterranean Waters (MWs) markedly stratified into relatively homogeneous layers where intense mixing processes occur, hence definitively showing that the MO there is composed of four-five different and essentially superimposed components. Within the Strait (Part 2), five north-south transects at both 5°50'W and 6°05'W, together with another yo-yo time series (6°05'W), show that the MO is markedly heterogeneous all along the Strait, but there on the horizontal, being composed of a set of different components juxtaposed side by side. All temperature-salinity diagrams from these transects are straight mixing lines between the Atlantic Waters (AWs) and each of the MWs, most of them evidence bottom homogeneous layers, the lightest of the MWs is split and starts sinking as soon as the Camarinal sills in the northern side of the Strait while the densest MWs are in its southern side, the MO has an overall density range > 0.5 kg.m-3 and it is markedly meandering at 6°05'W, and the AWs' variability is much larger than that of the MWs, which prevents from accurately specifying the MO characteristics downstream. Herein (Part 3) we re-analyze the whole CTD data set from the MO-2009 Experiment that was conducted at the Strait exit (near 6°20'W) by the Institut de Ciències del Mar from Barcelona (Spain) in order to specify the downstream momentum and energy evolution of the MO and investigate the mechanisms leading to its structure. Even without the above-mentioned results and our previous hypotheses in mind, 418 CTD profiles combining regional surveys (over 30 x 30 km²), repeated tow-yo transects (over ~6 km) performed with a relatively low sampling interval (~1 km) in cross-MO and along-MO directions, and yo-yo time series, provide valuable information about the hydrological structure of the MO there. Four components, with the lightest (densest) in the north (south), clearly juxtaposed side by side and relatively isolated from each others, being often separated by marked interface layers, spread over a ~0.7 kg.m-3 density range. Yo-yo time series confirm that short-term variability at a given place is essentially due to the MO meandering that allows evidencing locally two (up to three and even four) components, and density ranges up to 0.3 kg.m-3 within a couple of hours, which demonstrates that the MO heterogeneity is mainly due to the Sea functioning and the AWs-MWs mixing, its splitting does not needing any bathymetric effect. The fact that any of the four components can be missed with profiles 1 km apart accounts for their relatively small wideness and we claim that a single pair of tow and tow-yo (at a few-hundred m interval) cross-Strait transects performed near 6°20'W with basic instrumentation will provide definite information about the MO heterogeneity.
All most recent papers about the Mediterranean Outflow (MO) assume that it is homogeneous at leas... more All most recent papers about the Mediterranean Outflow (MO) assume that it is homogeneous at least in the western side of the Strait of Gibraltar and that its splitting into veins in the Atlantic Ocean is due to bathymetric effects at the Strait exit while we demonstrate that proofs about the MO heterogeneity within the whole Strait have been available since the mid 1980's at least. We focus herein on data collected at the Strait entrance in 1985 (Part 1), before analyzing 1985-1986 data within the Strait (Part 2) and data collected during the MO-2009 experiment at the Strait exit (Part 3). Having demonstrated that the MO is markedly heterogeneous from the Strait entrance to the Strait exit, our three papers demonstrate that the splitting into veins is essentially a direct consequence of the sea functioning. Indeed, veins have hydrological characteristics mainly dependent on those of the intermediate and deep Mediterranean Waters (MWs) formed in both the eastern and the western basins of the Sea, as well as on those of the Atlantic Waters (AWs) that mixed in the Strait with these MWs, the bathymetry at and downstream from the Strait exit playing a negligible role. Herein, we demonstrate that four-five MWs can be clearly identified at the Strait entrance, as we previously hypothesized, moreover forming relatively thick and homogeneous superimposed layers that are much more individualized than anywhere else in the Sea. For the first time ever, we provide numerous examples of density instabilities in all these layers that clearly illustrate the processes leading to such an increased stratification at the Strait entrance. So as to motivate theoretical analyses and numerical simulations that appear to be of dramatic interest, we hypothesize that the isopycnals slope (of a few %) across the Strait within the MO itself, that is a direct consequence of both the Coriolis effect and the different outflowing or overflowing velocities of the MWs, could be the main mechanism responsible for such a layering of the MO.
Journal of Marine Science and Engineering, 2022
Biogeochemical cycles of carbon transformation throughout the euphotic zone of the sea are contro... more Biogeochemical cycles of carbon transformation throughout the euphotic zone of the sea are controlled by physical processes, e.g., daily thermocline, variation in solar irradiance, thermohaline convection, and intermittent mixing. These processes should be regularly observed with sufficient time resolution at fixed geographical locations. This study provides a brief overview of the carbon observational site in the Northeastern Black Sea. The focus is on the design of a new tethered profiler Winchi for the inner continental shelf part of the site. The profiler hull and two outriggers comprise an open trimaran platform that is positively buoyant and tends to maintain a horizontal position in the water. The lower end of the winch wire is secured to the bottom anchor. By unwinding/winding the wire, the profiler ascends/descends while measuring the depth profiles of marine environment parameters ranging from the seafloor to air–sea interface. After surfacing, the profiler determines its ...
This study analyses the distribution and diet overlap of the early stages of sardine and hake off... more This study analyses the distribution and diet overlap of the early stages of sardine and hake off the Catalan coast during the autumn spawning period. Data on horizontal and vertical distributions of eggs and larvae, the larval size structure in the overlapping zones and the diet composition are examined. Information derived from the study of larval diet was used to discuss the consequences of the overlapping distributions.
43 Annual Larval Fish Conference, 21-24 May 2019, Palma, Balearic IslandsThe species composition,... more 43 Annual Larval Fish Conference, 21-24 May 2019, Palma, Balearic IslandsThe species composition, distribution and abundance of meso- and bathypelagic species from oceanic waters of the NE Atlantic have been analysed to investigate the modifications in vertical distribution patterns from larvae to adult stages. Plankton and micronekton samples from surface to 1800 m depth, were taken in May 2018 in 8 stations placed in a transect from 20°N to 55°N. The transect crossed intense productivity, thermal and salinity gradients, from the North Atlantic Subtropical Gyral Province (NASGP) to the north Atlantic Artic Province (NAAP). Hydrographical boundaries were evident in the species composition and abundance, with lower diversity in the northernmost station in the NAAP. Larvae and transforming stages of myctophiforms and stomiiforms dominated all over the region. Although the Brunt-Väisälä frequency indicates higher water column stability in the NASGP stations than in the north, vertical distributions were similar along the region. Myctophid larvae were always concentrated in the first 100 m, irrespective of the time of the day. Their transforming stages occurred from surface to 1200 m at night (with no clear migration), and from 400-700 during the day. Stomiiform larvae appeared in the upper 200 m, while transforming showed a wide distribution from surface to 1000 m both day and night. The distribution of the gonostomatid Cyctothone (7 species) is an interesting case of study with larvae always in the upper 100 m, and non-migrating juvenile and adults located in the mesopelagic zone (even reaching the bathypelagic layers in the case of C. microdon). As in previous investigations, it was globally observed that the deepening in the water column is an ontogenetic process related with development that starts when ventral groups of photophores become formed. The wider vertical distribution of this transition stages compared to both larva and adult indicates that they have not developed yet the vertical displacement characteristic of adult stagesPeer Reviewe
Journal Of Geophysical Research: Oceans, May 1, 2023
IV Congress of Marine Sciences, 11-13 June 2014, Las Palmas de Gran Canaria.-- 1 pageContinuous m... more IV Congress of Marine Sciences, 11-13 June 2014, Las Palmas de Gran Canaria.-- 1 pageContinuous measurements of the thermohaline fields were carried out between March 22nd and April 8th on the Spanish research vessel B/O Sarmiento de Gamboa in the framework of the SPURS (Salinity Processes in the Upper ocean Regional Study) project focused on the processes responsible for the formation and maintenance of the salinity maximum associated to the North Atlantic subtropical gyre. The high spatio-temporal resolution scanning of the first 300 meters of the water column was performed with a towed undulating platform SeaSoar, equipped with two CTDs, and sensors of dissolved oxygen, fluorescence and turbidity. The obtained data allowed determining the 3D temperature and salinity fields characterized by high inhomogeneity. Various relatively fresh and warm, and salty and relatively cold waters were observed to intruded into the Surface Maximum Salinity water mass. The 3D distribution of Turner Angle values allows to detect the areas of small-scale mixing activity and helps to better understanding the interrelation between differently transformed water masses inside the sampled areaPeer Reviewe
EAEJA, Apr 1, 2003
Data from two oceanographic surveys carried out in the Catalano-Balearic Sea, in February-March 1... more Data from two oceanographic surveys carried out in the Catalano-Balearic Sea, in February-March 1999 and January-February 2000, together with ocean colour imagery (SeaWifs), have been used to analyze the distribution of phytoplankton biomass and composition in relationship with the mesoscale hydrographic features of the area. In 1999, the water mass structure was chraraterised by the presence of an intense anticiclonic
Progress in Oceanography, Aug 1, 2005
Currents, particle fluxes and ecology were studied in the Palamó s submarine canyon (also known a... more Currents, particle fluxes and ecology were studied in the Palamó s submarine canyon (also known as the Fonera canyon), located in the northwestern Mediterranean. Seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis, on the canyon walls and on the adjacent slope. Additionally, local and regional hydrographic cruises were carried out. Current data showed that mean near surface and mid-depth currents were oriented along the mean flow direction (NE-SW), although at 400 and 1200 m depth within the canyon current reversals were significant, indicating a more closed circulation inside the canyon. Mean near-bottom currents were constrained by the local bathymetry, especially at the canyon head. The most significant frequency at all levels was the inertial frequency. A second frequency of about three days, attributed to a topographic wave, was observed at all depths, suggesting that this wave was probably not trapped near the bottom. The current field observed during the most complete survey revealed a meandering pattern with cyclonic vorticity just upstream from and within the canyon. The associated vertical velocity ranged between 10 and 20 m/day and was constrained to the upper 300 m. This latter feature, together with other computations, suggests that during this survey the meander was not induced by the canyon but by some kind of instability of the mean flow. In the canyon, suspended sediment concentration, downward particle fluxes, chlorophyll and particulate C and N were significantly higher up-canyon from about 1200 m depth than offshore, defining, along with the different
Journal of Marine Systems, Aug 1, 2019
The temporal evolution of water column turbidity was studied on a submarine canyon on the Barcelo... more The temporal evolution of water column turbidity was studied on a submarine canyon on the Barcelona continental margin. From April to June 2014, an instrumented mooring array equipped with an autonomous hydrographic profiler with a CTD and a turbidimeter was deployed in the Foix canyon axis at 870 m depth. The instruments were programmed to collect hydrographic profiles once per day to provide a view of the temporal evolution of water column characteristics from 200 to 800 m water depth. The results illustrate a well-defined water turbidity structure of particulate matter distributed in intermediate nepheloid layers (INLs) developed between 300 and 500 m water depth and above the canyon rims, and INLs and near-bottom nepheloid layers (BNLs) confined inside the canyon between 650 and 800 m water depth. Data from fishing vessels activity at the time of the deployment was obtained from Vessel Monitoring System (VMS). The presence and location of the fishing vessels in the study area suggested a relationship between trawling activity and the generation of such layers. Nepheloid layers were absent during the first part of the deployment, when there was no fishing activity within the Foix Canyon axis or at the adjacent continental slope. Later, with the beginning of trawling activity on the fishing grounds close to the canyon, both INLs and BNLs were observed in the profiling casts, suggesting a causative relationship with fishing activities. Additionally, the hydrodynamic conditions within the canyon also seem to favour particle retention and to increase water turbidity in thick BNLs when water circulation is directed up-canyon. Bottom trawling appears to act as a main sediment resuspension mechanism in the Barcelona continental slope regions, increasing suspended sediment concentration at specific water depths where fishing grounds are located. Suspended particles are then advected and propagate along and across-margin by ambient currents via nepheloid layers.
Progress in Oceanography, 2019
Progress in Oceanography, Apr 1, 2013
The analysis of a compilation of deep CTD casts conducted in the western Mediterranean from 1998 ... more The analysis of a compilation of deep CTD casts conducted in the western Mediterranean from 1998 to 2011 has documented the role that dense water formation, and particularly deep dense shelf water cascading off the Gulf of Lions, plays in transporting suspended particulate matter from the coastal regions down to the basin. Deep CTD casts reveal that after the 1999 and 2005-2006 deep cascading events the Western Mediterranean Deep Water (WMDW) was characterized by the presence of a thick bottom nepheloid layer (BNL) that corresponded in thickness with a thermohaline anomaly generated by the mixture of dense waters formed by deep convection in the
ABSTRACT An intensive observational programme of the Balearic Front, in the Western Mediterranean... more ABSTRACT An intensive observational programme of the Balearic Front, in the Western Mediterranean Sea, was carried out using conventional (CTDs from a ship) and new technologies (gliders). The strategy consisted of repeated sampling of a section almost perpendicular to the Balearic Current situated to the north of Mallorca Island. This section is coincident with track 773 of the ENVISAT satellite. In this work we present results of missions undertaken in July and September 2007. In July the sampling was designed to collect in-situ data from a ship and a coastal glider, almost simultaneously with the passage of the radar altimeter on board the ENVISAT satellite. In September the sampling was done only by the glider platform, and also simultaneously with the passage of the satellite. The Balearic Front was clearly detected by salinity (not temperature), with lower values (37.4 PSU) near the coast that are likely to be related to the input of recent Atlantic Water through the Mallorca Channel. The observed width of the front was about 35–40 km, with a vertical extension of 200 m. It had a significantly different pattern between the July and September samplings, which confirms the high mesoscale variability of this frontal area. Using a reference depth level of 180 m we have obtained maximum geostrophic velocities of 40–45 cm/s, flowing northeastwards along the north Mallorca coast. These velocity estimates are not sensitive to the test reference level (600 m), indicating that the layer between 200 and 600 m does not play a key role in the dynamics of the upper layer (200 m). A dynamic height rise from July to September (in 70 days) of about 3–7 cm reflects the seasonal cycle of sea level due mainly to thermosteric expansion of the water column. This gives a rise rate in the range of 1.3–3 cm/month, which is in agreement with previous estimates in the Mediterranean Sea. Absolute dynamic topography from altimetry data reveals good coherence with the dynamic height from the glider data in the area where there are common observations. In September, ENVISAT captured the sharp gradient observed with in-situ data, with mean velocities of about 24 cm/s, but with a smaller variance than the glider due to the larger wavelength of the filter applied to the altimeter data. From the technological point of view the observational experiment has confirmed the feasibility of using a coastal glider to monitor the spatial and low-frequency variability of the coastal ocean. The coastal glider was appropriate in this particular case since the vertical extension of the front only reaches up to 200 m. The autonomous platform was shown to be strongly robust, and able to monitor the area even under adverse meteorological conditions. This represents an important achievement, since under the same conditions the CTD sampling from a traditional research vessel would normally have been cancelled. Moreover, this type of platform allows autonomous collection of CTD casts and biogeochemical measurements at high spatial resolutions and at very low costs compared to conventional methods.
Marine Geophysical Researches, Jun 24, 2022
Terrestrial Multidisciplinary distributed Observatories for the Study of Arctic Connections (T-MO... more Terrestrial Multidisciplinary distributed Observatories for the Study of Arctic Connections (T-MOSAiC) Workshop - Arctic Science Summit Week (ASSW), 31 March - 7 April 2017, Prague, Czech Republic
V Encuentro de la Oceanografia Fisica (EOF 2018) - V Physical Oceanography Meeting, VI Simposio I... more V Encuentro de la Oceanografia Fisica (EOF 2018) - V Physical Oceanography Meeting, VI Simposio Internacional de Ciencias del Mar - VI International Symposium of Marine Sciences (ISMS 2018), 20- 22 June 2018, Vigo.-- 1 page
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Papers by Mikhail Emelianov