Global NEST International Conference on Environmental Science & Technology
The recent post-Glacial Mediterranean sea-level rise converted mountain valleys to islandic embay... more The recent post-Glacial Mediterranean sea-level rise converted mountain valleys to islandic embayments. These bays exhibit distinct hydrographic and biogeochemical characteristics, seasonally alternating thermohaline functioning and their coastal ecosystems support thriving coastal activities. The Kalloni Gulf, Lesvos island, Greece, constitutes a textbook example of the above type of embayments and -due to its proximity to the facilities of the University of the Aegean in the island’s capital, Mytilene- has become the focal point of the development of the prototype Coastal Environmental Observatory “AEGIS”. This laboratory has risen as the culmination of decade-long efforts of three Research Laboratories of the Department of Marine Sciences and includes both observational and forecasting components. The latter component comprises three levels of numerical modeling of the ocean circulation: The low-resolution (level 1) domain corresponds to the Central and North Aegean Sea, the inte...
In this study, a thermal spring located in the Gulf of Gera (Lesvos Island) is investigated in te... more In this study, a thermal spring located in the Gulf of Gera (Lesvos Island) is investigated in terms of radiotracers, water flow velocities and acoustic back-scattering properties by in situ observations. Water flow characteristics were deduced using in situ deployments of three marine sensors: an Acoustic Doppler Velocimeter (ADV), a High-Frequency Acoustic Doppler Current Profiler (ADCP), and a medium-resolution underwater gamma-ray detection system. The flow velocity combined with the activity concentration of natural radionuclides in the thermal spring provided information on the characteristics of the thermal spring in the specific gulf. The proposed methodology estimated the water supply, the residence time in the effective area of the in situ systems, and the residence time in the gulf. Eventually, the estimation of the characteristics of the discharged water source resulted from the synthetic evaluation of oceanographic measurements alongside appropriate models.
Combined micropaleontological and geochemical analyses of the high-sedimentation gravity core M-4... more Combined micropaleontological and geochemical analyses of the high-sedimentation gravity core M-4G provided new centennial-scale paleoceanographic data for sapropel S1 deposition in the NE Aegean Sea during the Holocene Climatic Optimum. Sapropel layer S1a (10.2–8.0 ka) was deposited in dysoxic to oxic bottom waters characterized by a high abundance of benthic foraminiferal species tolerating surface sediment and/or pore water oxygen depletion (e.g., Chilostomella mediterranensis, Globobulimina affinis), and the presence of Uvigerina mediterranea, which thrives in oxic mesotrophic-eutrophic environments. Preservation of organic matter (OM) is inferred based on high organic carbon as well as loliolide and isololiolide contents, while the biomarker record and the abundances of eutrophic planktonic foraminifera document enhanced productivity. High inputs of terrigenous OM are attributed to north Aegean borderland riverine inputs. Both alkenone-based sea surface temperatures (SSTs) and δO18G. bulloides records indicate cooling at 8.2 ka (S1a) and ~7.8 ka (S1 interruption). Sapropelic layer S1b (7.7–6.4 ka) is characterized by rather oxic conditions; abundances of foraminiferal species tolerant to oxygen depletion are very low compared with the U. mediterranea rise. Strongly fluctuating SSTs demonstrate repeated cooling and associated dense water formation, with a major event at 7.4 ka followed by cold spells at 7.0, 6.8, and 6.5 ka. The prominent rise of the carbon preference index within the S1b layer indicates the delivery of less degraded terrestrial OM. The increase of algal biomarkers, labile OM-feeding foraminifera and eutrophic planktonic species pinpoints an enhanced in situ marine productivity, promoted by more efficient vertical convection due to repeated cold events. The associated contributions of labile marine OM along with fresher terrestrial OM inputs after ~7.7 ka imply sources alternative/additional to the north Aegean riverine borderland sources for the influx of organic matter in the south Limnos Basin, plausibly related to the inflow of highly productive Marmara/Black Sea waters.
Global NEST International Conference on Environmental Science & Technology
This paper presents the state-of-the-art research conducted as part of EN.I.R.I.S.S.T. regarding ... more This paper presents the state-of-the-art research conducted as part of EN.I.R.I.S.S.T. regarding the emerging impact of shipping and transport to the environment. More specifically, it presents the digital platforms and services that are developed as part of the research infrastructure and are related to environmental sciences. The first is the “EcoMarpol Platform”, which caters for collecting and analyzing pollution-driven data as well as calculating the environmental imprint (atmospheric emissions, waste production, chemical pollution of marine waters and sediments) of maritime activities. This platform additionally includes the online monitoring of in-port emissions from shipping and pollution from ship-to-ship transfer operations or accidents and the environmental risk assessment management. The other platform is the “Passenger Sustainable Travel Platform”, as part of which a tool for calculating aircraft emissions (CO2 and air pollutants) will be developed and applied in the Gr...
The analysis of the 2002 Prestige tanker accident showed how public misinformation can worsen mar... more The analysis of the 2002 Prestige tanker accident showed how public misinformation can worsen marine pollution incidents, rendering their management suboptimal as these evolve, thus raising the issue of appropriately informing and educating coastal and island populations who are at risk. Two decades later, developments in electronic platforms, including Geographic Information Systems (GIS), the Automatic Identification System (AIS) for ship signal transmission, and social media, provide a set of means for public monitoring of such incidents, creating the possibility to antagonise effectively erroneous or malevolent information, which can hinder efficient actions for containing marine pollution risks even without active training of the populations concerned. The authors, in the framework of the development of the Marine Coastal Observatory and Risk Management project “AEGIS+”, have developed E-S.A.V.E., an online innovative platform that (a) meets the needs of different users as reve...
Understanding the processes that control the buoyancy fluxes of the Aegean Sea is important for v... more Understanding the processes that control the buoyancy fluxes of the Aegean Sea is important for various reasons. First, the Aegean is directly connected with the Black Sea and acts as a buffer between two opposite thermohaline systems, a concentration and a dilution basin (the Mediterranean vs the Black Sea), receiving and filtering the variability and changes of a much broader geographical area. Second, the Aegean is capable to produce large amounts of very dense water, having temporarily been the major originator of Eastern Mediterranean Bottom Water. These processes are controlled by the buoyancy fluxes, both through oceanic advection and atmospheric exchanges. In this work we examine the characteristics and variability of heat, freshwater and the overall buoyancy air-sea fluxes, focusing on the potential role of the interaction with the Black Sea. A thirty-year-long simulation (1985-2015) of the whole Eastern Mediterranean/Black Sea system, forced by ERA-Interim data, was used t...
The North Aegean Sea is one of the most interesting seas of the Mediterranean, being under the do... more The North Aegean Sea is one of the most interesting seas of the Mediterranean, being under the dominant impact of the Black Sea waters though the so-called Turkish Strait System (TSS – including the Dardanelles and Bosphorus Straits and the Marmara Sea). Moreover, it constitutes a potentially deep water formation site of the Eastern Mediterranean Sea along with the Adriatic Sea. Previous studies for the region focused – rightly – on the crucial role of low salinity Black Sea waters in controlling the overall thermohaline function and dynamics of the North Aegean. None of the previous modeling approaches studied the impact of tides in the mixing processes and the production of extremely dense water, especially during 1987, 1992 and 1993 when major deep water formation events took place in the region. In this work we examine the tidal impact via several long term simulations using a high resolution (1.0 km) ocean model covering the period from 1985 to 2013.The Regional Ocean Model Sys...
Three hydrographic cruises were undertaken to study the hydrology and to estimate the ecological ... more Three hydrographic cruises were undertaken to study the hydrology and to estimate the ecological status of the coastal ecosystem of the Strymonikos Gulf (North Aegean Sea) impacted by the riverine waters of the Strymon River. Surface sediments were also collected in order to determine the levels of organic contaminants in the gulf. Three main water masses were identified in the Strymonikos Gulf throughout the year: a) the surface river plume water, b) the surface and subsurface Black Sea Water and c) the near bottom (>50 m) water of Levantine origin. High nutrient concentrations were recorded close to the mouth of the river, indicating a rather eutrophic environment, which was restricted near the river discharge. The salinity-nutrient correlations of the surface waters of the study area were linear, indicating that the riverine waters are the major source of nutrient in the gulf. DIN:P ratios varied seasonally from relatively higher values during winter and early spring to lower ...
This work presents the in situ calibration procedures developed for the sensors of conductivity, ... more This work presents the in situ calibration procedures developed for the sensors of conductivity, dissolved oxygen and chlorophyll-α, attached to eleven Oceanor Seawatch-type buoys deployed since 1999 in the Aegean Sea. The sensors are deployed in the upper ...
ABSTRACT Buoyancy exchanges in the Aegean Sea lead to the formation of deep and bottom water, whi... more ABSTRACT Buoyancy exchanges in the Aegean Sea lead to the formation of deep and bottom water, which occasionally overflows in the eastern Mediterranean. In this study we attempt an assessment of the buoyancy exchange between the North and South Aegean through budget estimations. This will provide a first-order estimate of the North Aegean contribution to the interannual variability of the eastern Mediterranean deep waters. Our budget estimation consists of comparing the buoyancy change of the deep basins between successive CTD campaigns and the time integrated buoyancy flux through the surface (considering the Dardanelles outflow as an equivalent surface flux). In the North Aegean the difference between the surface buoyancy exchanges and the deep basins buoyancy content must balance the difference between the change of buoyancy content of the upper layers and the buoyancy exchange between the North and the South Aegean. The same balance holds for the South Aegean, with an extra term representing the buoyancy exchange at the Cretan Straits included in the later difference. An estimate of the buoyancy exchange between the two basins is obtained from the two balance equations. Surface buoyancy exchanges are estimated using heat and freshwater data from the ECMWF dataset. A first order quality control of the dataset is possible through its comparison with the buoyancy fluxes in the Aegean estimated using a corrected version of the Comprehensive Ocean-Atmosphere Data Set, the UWM/COADS, which have been constrained to balance the Mediterranean heat budget. For the buoyancy forcing through the Dardanelles we exploit the output of a state-of-the-art hydraulic model simulating the exchange flow through the Turkish Straits system, developed and fine-tuned in the framework of the bilateral Greek-Ukrainian project. For the buoyancy content estimation of the deep basins we isolate periods where there are enough CTD observations covering the majority of the North and South Aegean. The results are discussed in view of recent findings regarding the possible role of North Aegean deep-water formation in triggering phenomena like the Eastern Mediterranean Transient.
Global NEST International Conference on Environmental Science & Technology
The recent post-Glacial Mediterranean sea-level rise converted mountain valleys to islandic embay... more The recent post-Glacial Mediterranean sea-level rise converted mountain valleys to islandic embayments. These bays exhibit distinct hydrographic and biogeochemical characteristics, seasonally alternating thermohaline functioning and their coastal ecosystems support thriving coastal activities. The Kalloni Gulf, Lesvos island, Greece, constitutes a textbook example of the above type of embayments and -due to its proximity to the facilities of the University of the Aegean in the island’s capital, Mytilene- has become the focal point of the development of the prototype Coastal Environmental Observatory “AEGIS”. This laboratory has risen as the culmination of decade-long efforts of three Research Laboratories of the Department of Marine Sciences and includes both observational and forecasting components. The latter component comprises three levels of numerical modeling of the ocean circulation: The low-resolution (level 1) domain corresponds to the Central and North Aegean Sea, the inte...
In this study, a thermal spring located in the Gulf of Gera (Lesvos Island) is investigated in te... more In this study, a thermal spring located in the Gulf of Gera (Lesvos Island) is investigated in terms of radiotracers, water flow velocities and acoustic back-scattering properties by in situ observations. Water flow characteristics were deduced using in situ deployments of three marine sensors: an Acoustic Doppler Velocimeter (ADV), a High-Frequency Acoustic Doppler Current Profiler (ADCP), and a medium-resolution underwater gamma-ray detection system. The flow velocity combined with the activity concentration of natural radionuclides in the thermal spring provided information on the characteristics of the thermal spring in the specific gulf. The proposed methodology estimated the water supply, the residence time in the effective area of the in situ systems, and the residence time in the gulf. Eventually, the estimation of the characteristics of the discharged water source resulted from the synthetic evaluation of oceanographic measurements alongside appropriate models.
Combined micropaleontological and geochemical analyses of the high-sedimentation gravity core M-4... more Combined micropaleontological and geochemical analyses of the high-sedimentation gravity core M-4G provided new centennial-scale paleoceanographic data for sapropel S1 deposition in the NE Aegean Sea during the Holocene Climatic Optimum. Sapropel layer S1a (10.2–8.0 ka) was deposited in dysoxic to oxic bottom waters characterized by a high abundance of benthic foraminiferal species tolerating surface sediment and/or pore water oxygen depletion (e.g., Chilostomella mediterranensis, Globobulimina affinis), and the presence of Uvigerina mediterranea, which thrives in oxic mesotrophic-eutrophic environments. Preservation of organic matter (OM) is inferred based on high organic carbon as well as loliolide and isololiolide contents, while the biomarker record and the abundances of eutrophic planktonic foraminifera document enhanced productivity. High inputs of terrigenous OM are attributed to north Aegean borderland riverine inputs. Both alkenone-based sea surface temperatures (SSTs) and δO18G. bulloides records indicate cooling at 8.2 ka (S1a) and ~7.8 ka (S1 interruption). Sapropelic layer S1b (7.7–6.4 ka) is characterized by rather oxic conditions; abundances of foraminiferal species tolerant to oxygen depletion are very low compared with the U. mediterranea rise. Strongly fluctuating SSTs demonstrate repeated cooling and associated dense water formation, with a major event at 7.4 ka followed by cold spells at 7.0, 6.8, and 6.5 ka. The prominent rise of the carbon preference index within the S1b layer indicates the delivery of less degraded terrestrial OM. The increase of algal biomarkers, labile OM-feeding foraminifera and eutrophic planktonic species pinpoints an enhanced in situ marine productivity, promoted by more efficient vertical convection due to repeated cold events. The associated contributions of labile marine OM along with fresher terrestrial OM inputs after ~7.7 ka imply sources alternative/additional to the north Aegean riverine borderland sources for the influx of organic matter in the south Limnos Basin, plausibly related to the inflow of highly productive Marmara/Black Sea waters.
Global NEST International Conference on Environmental Science & Technology
This paper presents the state-of-the-art research conducted as part of EN.I.R.I.S.S.T. regarding ... more This paper presents the state-of-the-art research conducted as part of EN.I.R.I.S.S.T. regarding the emerging impact of shipping and transport to the environment. More specifically, it presents the digital platforms and services that are developed as part of the research infrastructure and are related to environmental sciences. The first is the “EcoMarpol Platform”, which caters for collecting and analyzing pollution-driven data as well as calculating the environmental imprint (atmospheric emissions, waste production, chemical pollution of marine waters and sediments) of maritime activities. This platform additionally includes the online monitoring of in-port emissions from shipping and pollution from ship-to-ship transfer operations or accidents and the environmental risk assessment management. The other platform is the “Passenger Sustainable Travel Platform”, as part of which a tool for calculating aircraft emissions (CO2 and air pollutants) will be developed and applied in the Gr...
The analysis of the 2002 Prestige tanker accident showed how public misinformation can worsen mar... more The analysis of the 2002 Prestige tanker accident showed how public misinformation can worsen marine pollution incidents, rendering their management suboptimal as these evolve, thus raising the issue of appropriately informing and educating coastal and island populations who are at risk. Two decades later, developments in electronic platforms, including Geographic Information Systems (GIS), the Automatic Identification System (AIS) for ship signal transmission, and social media, provide a set of means for public monitoring of such incidents, creating the possibility to antagonise effectively erroneous or malevolent information, which can hinder efficient actions for containing marine pollution risks even without active training of the populations concerned. The authors, in the framework of the development of the Marine Coastal Observatory and Risk Management project “AEGIS+”, have developed E-S.A.V.E., an online innovative platform that (a) meets the needs of different users as reve...
Understanding the processes that control the buoyancy fluxes of the Aegean Sea is important for v... more Understanding the processes that control the buoyancy fluxes of the Aegean Sea is important for various reasons. First, the Aegean is directly connected with the Black Sea and acts as a buffer between two opposite thermohaline systems, a concentration and a dilution basin (the Mediterranean vs the Black Sea), receiving and filtering the variability and changes of a much broader geographical area. Second, the Aegean is capable to produce large amounts of very dense water, having temporarily been the major originator of Eastern Mediterranean Bottom Water. These processes are controlled by the buoyancy fluxes, both through oceanic advection and atmospheric exchanges. In this work we examine the characteristics and variability of heat, freshwater and the overall buoyancy air-sea fluxes, focusing on the potential role of the interaction with the Black Sea. A thirty-year-long simulation (1985-2015) of the whole Eastern Mediterranean/Black Sea system, forced by ERA-Interim data, was used t...
The North Aegean Sea is one of the most interesting seas of the Mediterranean, being under the do... more The North Aegean Sea is one of the most interesting seas of the Mediterranean, being under the dominant impact of the Black Sea waters though the so-called Turkish Strait System (TSS – including the Dardanelles and Bosphorus Straits and the Marmara Sea). Moreover, it constitutes a potentially deep water formation site of the Eastern Mediterranean Sea along with the Adriatic Sea. Previous studies for the region focused – rightly – on the crucial role of low salinity Black Sea waters in controlling the overall thermohaline function and dynamics of the North Aegean. None of the previous modeling approaches studied the impact of tides in the mixing processes and the production of extremely dense water, especially during 1987, 1992 and 1993 when major deep water formation events took place in the region. In this work we examine the tidal impact via several long term simulations using a high resolution (1.0 km) ocean model covering the period from 1985 to 2013.The Regional Ocean Model Sys...
Three hydrographic cruises were undertaken to study the hydrology and to estimate the ecological ... more Three hydrographic cruises were undertaken to study the hydrology and to estimate the ecological status of the coastal ecosystem of the Strymonikos Gulf (North Aegean Sea) impacted by the riverine waters of the Strymon River. Surface sediments were also collected in order to determine the levels of organic contaminants in the gulf. Three main water masses were identified in the Strymonikos Gulf throughout the year: a) the surface river plume water, b) the surface and subsurface Black Sea Water and c) the near bottom (>50 m) water of Levantine origin. High nutrient concentrations were recorded close to the mouth of the river, indicating a rather eutrophic environment, which was restricted near the river discharge. The salinity-nutrient correlations of the surface waters of the study area were linear, indicating that the riverine waters are the major source of nutrient in the gulf. DIN:P ratios varied seasonally from relatively higher values during winter and early spring to lower ...
This work presents the in situ calibration procedures developed for the sensors of conductivity, ... more This work presents the in situ calibration procedures developed for the sensors of conductivity, dissolved oxygen and chlorophyll-α, attached to eleven Oceanor Seawatch-type buoys deployed since 1999 in the Aegean Sea. The sensors are deployed in the upper ...
ABSTRACT Buoyancy exchanges in the Aegean Sea lead to the formation of deep and bottom water, whi... more ABSTRACT Buoyancy exchanges in the Aegean Sea lead to the formation of deep and bottom water, which occasionally overflows in the eastern Mediterranean. In this study we attempt an assessment of the buoyancy exchange between the North and South Aegean through budget estimations. This will provide a first-order estimate of the North Aegean contribution to the interannual variability of the eastern Mediterranean deep waters. Our budget estimation consists of comparing the buoyancy change of the deep basins between successive CTD campaigns and the time integrated buoyancy flux through the surface (considering the Dardanelles outflow as an equivalent surface flux). In the North Aegean the difference between the surface buoyancy exchanges and the deep basins buoyancy content must balance the difference between the change of buoyancy content of the upper layers and the buoyancy exchange between the North and the South Aegean. The same balance holds for the South Aegean, with an extra term representing the buoyancy exchange at the Cretan Straits included in the later difference. An estimate of the buoyancy exchange between the two basins is obtained from the two balance equations. Surface buoyancy exchanges are estimated using heat and freshwater data from the ECMWF dataset. A first order quality control of the dataset is possible through its comparison with the buoyancy fluxes in the Aegean estimated using a corrected version of the Comprehensive Ocean-Atmosphere Data Set, the UWM/COADS, which have been constrained to balance the Mediterranean heat budget. For the buoyancy forcing through the Dardanelles we exploit the output of a state-of-the-art hydraulic model simulating the exchange flow through the Turkish Straits system, developed and fine-tuned in the framework of the bilateral Greek-Ukrainian project. For the buoyancy content estimation of the deep basins we isolate periods where there are enough CTD observations covering the majority of the North and South Aegean. The results are discussed in view of recent findings regarding the possible role of North Aegean deep-water formation in triggering phenomena like the Eastern Mediterranean Transient.
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Papers by Vassilis Zervakis