Lemnos Island Research Articles

HF Radar observations of the Dardanelles outflow current in North Eastern Aegean using validated WERA HF radar data

A two-site WERA HF radar station was installed in November 2009 at the eastern coast of Lemnos Island in North Aegean Sea, aiming to monitor the surface inflow of Black Sea waters exiting from the Dardanelles Strait, as well as to constitute a coastal management tool for incidents of oil-pollution or save-and-rescue operations. Strong interference by foreign transmissions is a source of noise deteriorating the quality of the backscattered signal, thus significantly reducing the HF radar’s effective data return rate. In order to ameliorate this problem, further quality-control and data gap interpolating procedures have been developed and applied, to be used in addition to the procedures incorporated and used by the manufacturer’s signal processing software. The second-level processing involves traditional despiking in the temporal domain, preceding Empirical Orthogonal Function analysis. The latter is used not only to filter high-frequency noise but also to fill data gaps in time and space. The data reconstruction procedure has been assessed via comparison of (a) HF radial with CODE-type drifter radial velocities as well as (b) HF-derived virtual drifter tracks with actual drifter tracks. The main circulation features and their variability, as revealed by the reconstructed fields, are presented.

Erratum to: The Lemnos 8 January 2013 (M w=5.7) earthquake: fault slip, aftershock properties and static stress transfer modeling in the north Aegean Sea

We investigate mainshock slip distribution and aftershock activity of the 8 January 2013 M w = 5.7 Lemnos earthquake, north Aegean Sea. We analyse the seismic waveforms to better understand the spatio-temporal characteristics of earthquake rupture within the seismogenic layer of the crust. Peak slip values range from 50 to 64 cm and mean slip values range from 10 to 12 cm. The slip patches of the event extend over an area of dimensions 16 × 16 km2. We also relocate aftershock catalog locations to image seismic fault dimensions and test earthquake transfer models. The relocated events allowed us to identify the active faults in this area of the north Aegean Sea by locating two, NE–SW linear patterns of aftershocks. The aftershock distribution of the mainshock event clearly reveals a NE–SW striking fault about 40 km offshore Lemnos Island that extends from 2 km up to a depth of 14 km. After the mainshock most of the seismic activity migrated to the east and to the north of the hypocenter due to (a) rupture directivity towards the NE and (b) Coulomb stress transfer. A stress inversion analysis based on 14 focal mechanisms of aftershocks showed that the maximum horizontal stress is compressional at N84°E. The static stress transfer analysis for all post-1943 major events in the North Aegean shows no evidence for triggering of the 2013 event. We suggest that the 2013 event occurred due to tectonic loading of the North Aegean crust.

Influence of Dardanelles outflow induced thermal fronts and winds on drifter trajectories in the Aegean Sea

The data provided by 12 drifters deployed in the Northern Aegean Sea in the vicinity of the Dardanelles Strait in August 2008 and February 2009 are used to explore the surface circulation of the basin and the connectivity to the Black Sea. The drifters were deployed within the Dardanelles outflow of waters of Black Sea origin in the Northeastern Aegean. Thanks to the particular choice of the drifter deployment positions, the data set provides a unique opportunity to observe the branching behaviour of the surface currents around Lemnos Island. Such pathways were notpossible to study with previous drifter deployments that were far from the Dardanelles Strait. In addition, the drifter tracks covered the Aegean basin quite thoroughly, mapping major circulation features and supporting the overall general circulation patterns described by previous observational and modelling studies. The collected data display cases in which drifters are driven by winds and thermal fronts. Wind products were used to estimate the influence of the atmospheric forcing on the drifter trajectories. Satellite sea surface temperature images were connected to the drifter tracks, demonstrating a high correlation between the remote and in situ observations. The waters of Black Sea origin were traced all the way to the Southern Aegean, establishing a strong connectivity link between the Aegean and Black Sea basins.

The Optimal use of Renewable Energy Sources—The Case of Lemnos Island

The efficient use of renewable energy sources (RES) is one of the major issues in the modern energy sector. The objective of this work was to examine the potential of wind energy, solar energy (e.g., photovoltaics), and biomass energy sources to meet the current energy use in the island of Lemnos in Greece. An optimization methodology was applied to the energy system of the island, where various RES are abundant and could be exploited to satisfy part of the island's energy needs. An optimization model has been developed having as an objective the satisfaction of Lemnos Island energy needs from RES taking into consideration a multiplicity of criteria such as environmental impacts, energy demand, energy cost, and resources availability. A series of solutions have resulted, based on deterministic model runs, providing decision makers the flexibility to choose the appropriate solution based on the given situation.

A study of the 8 January 2013 Mw5.8 earthquake sequence (Lemnos Island, East Aegean Sea)

Abstract The 8 January 2013 Mw5.8 earthquake sequence south of Lemnos Island (East Aegean Sea) is investigated. The focal mechanisms of the strongest events, obtained by waveform modelling, together with the HypoDD relocated epicentres, clearly show the activation of a dextral strike-slip fault, no more than 14 km in length, trending N60°E, and extending in depth from approximately 3 to 25 km, with the best determined focal depths in the range 3 to ~ 13 km. The distribution of slip onto the fault plane shows a single patch of 7 × 8 km 2 , where the average and the peak slip are equal to 30 cm and 130 cm, respectively. The locus of the peak slip is well resolved to be ~ 2.5 km away from the hypocentre, towards SW. The slip model was used to forward model the distribution of Peak Ground Velocity (PGV in cm/s) in the near source. The PGV contours imply that if any directivity is associated with this event, this is towards SW. The sequence in study, is located in the eastward extension of the Agios Efstratios Fault Zone, which was the locus of the February 19, 1968 Mw7.2 earthquake, which produced surface rupture on the island itself. The Agios Efstratios Fault Zone terminates off shore, south of Lemnos Island. The 2013 sequence is not connected, in a strict sense, with the Agios Efstratios Fault. It indicates rupture of another fault, approximately parallel to it, and the characteristics of the sequence are in accordance with the regional tectonics and previous knowledge. The Coulomb stress change associated with the mainshock, is also examined to evaluate any significant enhance of stresses along the Agios Efstratios Fault Zone.

Key factors determining the seasonal population growth rate of European wild rabbits and their implications for management

Recently, the European rabbit (Oryctolagus cuniculus) has received contrasting considerations due to its multidimensional role in the Mediterranean ecosystems. Within this framework, knowledge of factors determining its population size may have important consequences for designing an effective management plan. In this paper, we quantified the combined influence of the major demographic and mechanistic factors on seasonal population fluctuation of European rabbits on Lemnos Island (Greece), during 2007–2009. We developed a hypothetical model taking into account direct (productivity, predation, hunting pressure, food shortage, habitat treatment) and indirect factors (soil moisture, adverse weather conditions) using structural equation modeling. We tested for their influence on the seasonal population growth rate (spgr) as determined by line transects to estimate rabbit abundance. The productivity induced higher pgr. Food shortage, which is affected by low soil moisture during the late summer and early autumn, is demonstrated to be the most important negative factor followed by the hunting pressure and predation. Demographic and mechanistic factors highlighted in this analysis could be used either for conservation or for controlling populations of the species.

Modeling the distribution of wild rabbits (Oryctolagus cuniculus) on a Mediterranean island

AbstractThe European rabbit (Oryctolagus cuniculus) is a widely distributed mammal with an often contradictory ecological role, imposing the need for population management. Sound management requires an in‐depth understanding of the complex species–habitat relationships. In this study, CART analysis was employed to identify the most important environmental and anthropogenic factors affecting the spatial distribution of wild rabbit on Lemnos Island, northeastern Aegean Sea in Greece. On Lemnos, this species is considered an agricultural pest due to its overabundance resulting from the long‐term absence of viral diseases, limited predation pressure, and lack of effective management. The study was carried out during the summer of 2008 by surveying rabbit densities in 181 2 × 2‐km squares. Seven environmental and 14 anthropogenic variables, measured at two spatial scales, were used as explanatory variables. Soil hardness was the most influential variable, dividing the island into two distinct areas, namely the rabbit‐poor areas with hard rocky soils and the rabbit‐rich areas where soft soils prevail. In the former, the presence of a sharp relief can lead to complete absence of the species, while a combination of gentle relief, low altitudes, and low presence of arable land can lead to moderate rabbit density. In the latter, human‐caused disturbance can reduce the number of rabbits, while a high density of ecotones and streams and a high presence of riparian vegetation can increase population densities to its highest levels observed. Our findings can formulate a scientific basis for the development of an effective management strategy for its population control.

Palaeoenvironmental evolution, sea-level changes and Human occupation in Lemnos Island during last 6000 years (North Aegean Sea, Greece)

Palaeoenvironmental evolution, sea-level changes and Human occupation in Lemnos Island during last 6000 years (North Aegean Sea, Greece)

Paleoclimatology and Paleoecology across the Eocene/Oligocene boundary, Thrace Basin, Northeast Aegean Sea, Greece

The detailed biostratigraphic and ichnological analysis of the Upper Eocene/Lower Oligocene forearc sedimentary sequence in the southern Greek part of the Thrace Basin on Lemnos Island reveals a relationship between eco-sedimentary factors and the base-level dynamics influencing calcareous nannofossils and trace fossil assemblages. The lower part of the ~350m thick succession was deposited in a sand-rich submarine fan system and upper part in a shelf environment. It contains nannofossil assemblages and distributions typical of the NP19–NP21 biozones. The Eocene/Oligocene (E/O) boundary (top of NP20 biozone) is clearly distinguished within the upper parts of the turbidite system where a decrease in water temperature, salinity, nutrient supply and oxygenation level is also revealed. Additionally, 19 ichnospecies, mostly graphoglyptids typical of deep-sea fan deposits, have been distinguished. The trace fossil diversity and abundance decrease upward reflecting the impact of the changing depositional environments from basin floor fans, to slope systems and then shelfal environments. The regional basin-fill history, rather than global climatic changes, was probably the fundamental controlling factor on the distribution of graphoglyptids and other trace fossils across the E/O boundary.

Palaeoenvironmental evolution and sea-level changes in the coastal area of NE Lemnos Island (Greece) during the Holocene

The study area is located on the northeastern coast of Lemnos Island (North Aegean Sea, 40°2′30″N, 25°00′00″E). It covers the archaeological settlement of Hephestia located in the Purnia Gulf and the coastal area of Alyki Lagoon. Reconstruction of the palaeogeography used palaeoenvironment data delivered from foraminifera and sea-level changes, providing archeological data about the presence of a potential harbour in the area.Geomorphological mapping as well as sedimentological and micropalaeontological studies of the Holocene coastal deposits were conducted. Four boreholes were drilled from the Alyki Lagoon, reaching 2.5 m to 11 m at the deepest and two from Hephestia area, reaching a depth of 6 m. Twenty-four samples were dated using the AMS radiocarbon method, providing a chronology of the sedimentary units.The calculated age from the boreholes provides dates from 7050 cal BP to 990 cal BP There was a constant sea-level rise during the last 7000 cal BP in the study area. Results from the model of Lambeck sea level curve and sea level index point from Hephestia and Alyki show a vertical difference of 0.5–1.5 m below sea level. The foraminiferal fauna analysis shows the development of shallow marine conditions with fresh water influx during 7000–4000 cal BP and a temporary lagoon environment with fluctuations to shallow bay environment from 4000 to 990 cal BP.

Slip preference on pre-existing faults: a guide tool for the separation of heterogeneous fault-slip data in extensional stress regimes

Synthetic fault-slip data have been considered in the present paper, in order to examine through a simple graphical manner the validity and use of the widely mentioned and applied criteria such as the slip preference, slip tendency, kinematic (P and T) axes, transport orientation and strain compatibility. The examination and description concern extensional stress regimes whose greatest principal stress axis (σ1) always remains in vertical position as in Andersonian stress states. In particular, radial extension (RE), radial–pure extension (RE–PE), pure extension (PE), pure extension–transtension (PE–TRN) and transtension (TRN) are examined with the aid of the Win-Tensor stress inversion software. In all of these extensional stress regimes only extensional faults can be activated. The lower dip angle of the reactivated faults is about 40° assuming that the coefficient of friction is no smaller than 0.6. The increase of the stress ratio and/or the fault dip angle up to 70° results in the increase of the slip deviation from the normal activation. Based on the present examination of the slip preference and slip tendency in different extensional stress regimes, a new simple and practical method is proposed herein in order to separate originally heterogeneous fault-slip data into homogeneous fault groups, by which different extensional stress regimes could be determined. The application of the method on the already published fault-slip data of Lemnos Island supports its validity since over 90% the resulted fault groups and stress regimes coincide to the already published ones.

Porosity-Permeability and Textural Parameters of the Palaeogene Forearc Sedimentary Fill on Lemnos Island, NE Greece

The Palaeogene forearc sedimentary fill on Lemnos Island, NE Greece, was examined to determine reservoir characteristics and textural parameters. During this time interval the studied area was the site of accumulation of submarine fans that underlie shelf deposits, with tectonic activity responsible for the shallowing upward trend. Turbidites were deposited in both inner (slope fan facies) and outer parts (basin floor fan facies) of the submarine fan system and consist of alternating sandstone and mudstone beds. Sandstones occur in both complete and incomplete Bouma sequences while shelf deposits have been interpreted as storm-surge deposits on the deeper parts of shelves. The 'Mercury Porosimetry Technique' was carried out on 20 sandstone samples, while 30 sandstone samples were examined under a polarizing microscope for grain-size analysis. This porosity-permeability study suggests that these rocks can be considered as both oil and gas reservoirs. 'Slope' fan facies generally reveal the most efficient values, making them the most promising sub-environment for further hydrocarbon research. Most samples display two pore-size distributions suggesting major textural heterogeneity. Textural parameter analysis reveals that sorting was of great importance during sedimentation. Rocks are generally well to very well-sorted while samples with moderate sorting are also present. This fact can be both attributed to the restricted grain-size range and their possible great distance from the source area. This generally well-sorted sequence argues well for further hydrocarbon research in the Northeast Aegean Sea, since the higher the sorting the higher the porosity. Selected samples are generally very fine to fine grained, whereas medium-grained sandstones are extremely rare and mostly seen on 'slope' fan facies. The finest grained sandstones are the best sorted.

Plant genetic resources of Lemnos (Greece), an isolated island in the Northern Aegean Sea, with emphasis on landraces

Lemnos Island is located in the Northern Aegean Sea and presents a rich biodiversity in plant genetic resources including wild species and crop landraces. Landraces have been cultivated under traditional agricultural systems and many have survived genetic erosion. They are mainly conserved in home gardens or in small fields, usually by elderly people, and are limited to local consumption. Two collecting expeditions were organized in Lemnos, a minor one in 2009 and a larger one in 2010. The results of the two current expeditions are discussed and compared with previous expeditions in the island. An overview is given on the crops cultivated, the landraces collected and those considered as lost, alongside with some information about their traditional uses. Finally, the importance of landraces in modern agriculture and preservation policies in Lemnos are discussed.

Hydrography of the eastern part of the Aegean Sea during the Eastern Mediterranean Transient (EMT)

Hydrographic features of the Aegean Sea were studied using CTDs collected in 4 cruises from 1991 to 1993. This period covers an interesting large-scale change in the thermohaline circulation in the Eastern Mediterranean and the Aegean Sea known as the Eastern Mediterranean Transient (EMT) and was first described during early 1990s. The cruise data is analyzed to depict the spatial variability of the water masses of the Aegean Sea in this period. We found Levantine Waters to be particularly prominent during the spring of 1992, more than in the other seasons. In the Central Aegean Sea the circulated cold water mixes with the upwelling water and very dense water remains behind in summer 1991. The Levantine Surface Water (LSW) is blocked and does not penetrate further to the north because of the existing upwelling water seen near Saros (Buyukkemikli Cape) and off-shore side of Baba Cape (product of northerly wind) especially in summer 1991 and in fall 1992. The water masses are nearly homogeneous vertically with the influence of strong wind and convective mixing in winter time. In this study, we underline the contribution of the eastern part of the Aegean to the rising isopycnal levels during the EMT. In turn, i) the dense water cascades from eastern shelf of the Aegean Sea, ii) the upwelling and downwelling processes in the northern and central basins, iii) the cooling effect of Black Sea Water (BSW) on upwelled water at the south of the Lemnos Island (open sea convection) and iv) local wind forcing.

Geometry and sequence stratigraphy of the Late Eocene-Early Oligocene shelf and basin floor to slope turbidite systems, Lemnos Island, NE Greece

The Late Eocene-Early Oligocene sedimentary fill of the Lemnos Island, NE Greece, is represented by a submarine fan and shelf deposits. Turbidites in the system occur as a laterally isolated body, with one sediment influx center present. The influx center is a proximal distributary channel that occupies a position approximately in the fan’s center and displays the coarsest sediment in the study area. It also suggests in association with the main palaeocurrent direction toward NE a curved shape for the fan. The stratigraphic succession of the submarine fans indicates that their sedimentation started during the base level fall and completed shortly after the base level rise. As a consequence, the study area was filled by turbidites that correspond to forced regressive, lowstand normal regressive, and transgressive genetic units. The progradational bedsets, within the basal part of the turbidite deposits, recorded the history of the base level fall. The mixed progradational/aggradational style of the upper part of the submarine fan system suggests that the regression of the shoreline is driven by sediment supply during a period of base-level rise at the shoreline, or at a time of baselevel stillstand. The overlying shelf facies consist of thick to medium bedded sandstones and mudstones, which display a general thinning upward trend. The base of the mudstone facies that overlie the thick-bedded, amalgamated sandstones corresponds to a transgressive surface. This surface separates the low-stand deposits (thick-bedded sandstones) from the high stand deposits (mudstone facies), suggesting that deposition of shelf facies occurred during a transgressive system tract.

Meteorological influences on the surface hydrographic patterns of the North Aegean Sea

Hydrographic data from the North Aegean Sea were used to examine the summer variability of surface water masses during the period 1998–2001. Attention was placed on the surface hydrographic features of the area, such as the Black Sea Water (BSW) plume expansion, the frontal characteristics of the BSW with the Levantine Intermediate Water (LIW) and the variability of submesoscale hydrographic features (such as the Samothraki Anticyclone). Strong southerly wind stresses were found responsible for relaxing the horizontal density gradients across the BSW-LIW frontal zone and displacing this front to the north of Lemnos Island, thus suppressing the Samothraki Anticyclone towards the Thracian Sea continental shelf. Under northerly winds, the BSW-LIW front returns to its regular position (south of Lemnos Island), thus allowing the horizontal expansion of the Samothraki gyre up to the Athos Peninsula. Present results indicate the importance of medium-term wind stress effects on the generation of Samothraki Anticyclone suppression/expansion events.

North–Central Aegean Sea surface and intermediate water masses and their role in triggering the Eastern Mediterranean Transient

Interrannual variability in the surface and intermediate water masses of the North–Central Aegean Sea is being investigated through data collected by the Hellenic Navy Hydrographic Service (HNHS) during the Eastern Mediterranean Transient (EMT) post-peak period. Data suggest that following the last major deep-water formation episode in the Aegean Sea (1993), Black Sea Water (BSW) is confined to the northernmost part of the basin, while saline Levantine Surface Water (LSW) becomes the dominant Central Aegean surface water mass, intruding below the BSW layer even north of Lemnos Island. Furthermore, highly saline intermediate masses transfer additional salt to the North–Central Aegean basin. After the early 90s, BSW gradually reclaims most of the Central Aegean while the salinity of both LSW and intermediate masses is reduced. The enhanced presence of these highly saline water masses in the early 90s, presumably signifies the intrusion of high salinity water of Levantine origin into the North–Central Aegean following the massive outflow of dense Aegean water into the Eastern Mediterranean. This salinity intrusion was one of the preconditioning factors that enhanced dense water formation in the Aegean during the last major deep-water formation phase of the EMT, affecting the characteristics of the deep-water masses produced.

Petrography and geochemistry of the late Eocene–early Oligocene submarine fans and shelf deposits on Lemnos Island, NE Greece. Implications for provenance and tectonic setting

AbstractProvenance and tectonic history of the late Eocene‐early Oligocene submarine fans and shelf deposits on Lemnos Island, NE Greece, were studied using sandstone framework composition, sedimentological data and sandstone and mudstone geochemistry. The resulting tectonic–sedimentological model is based on the late Eocene–early Oligocene Lemnos Island being in a forearc basin with the outer arc ridge as a major sediment source. Modal petrographic analysis of the studied sandstones shows that the source area comprises sedimentary, metamorphic and plutonic igneous rocks deposited in the studied area in a recycled orogenic environment. Moreover, within the above sediments, the minor occurrence of volcanic fragments suggests little or no influence of a volcanic source. Provenance results, based on major, trace and rare earth element (REE) data, suggest an active continental margin/continental island arc signature. All the samples are LREE, enriched relative to HREE, with a flat HREE pattern and positive Eu anomalies, suggesting that the processes of intracrustal differentiation (involving plagioclase fractionation) were not of great importance. Results derived from the multi‐element diagrams also suggest an active margin character, and a mafic/ultramafic source rock composition, while the positive anomaly of Zr that can be attributed to a passive continental margin source, is most likely associated with reworking and sorting during sediment transfer. Palaeocurrents, with a NE–NNE direction, indicate a northeast flow, towards the location of the late Eocene–early Oligocene magmatic belt in the north‐east Aegean region. Conglomerates are composed of chert, gneiss and igneous fragments, such as basalts and gabbros, suggesting this outer arc ridge as a likely source area. Copyright © 2009 John Wiley & Sons, Ltd.

Organic geochemical characteristics of the late Eocene–early Oligocene submarine fans and shelf deposits on Lemnos Island, NE Greece

The Paleogene deep-sea clastic and shelf deposits on Lemnos Island, NE Greece were studied regarding their organic geochemical characteristics. This study suggests that the above rocks can be designated as source rocks that have some moderate to fair potential for gaseous hydrocarbons. Studied sediments have been deposited in a forearc basin, with the outer arc ridge as a major sediment source. During late Eocene–early Oligocene Lemnos was the site of accumulation of submarine fans that underlay shelf deposits, with tectonic activity being responsible for the upward shallowing of the depositional environment. Areas of turbidites have been seen in parts of a sand-rich submarine fan, on the base of the slope to basin floor environment. On these rocks the Rock-Eval 6 pyrolysis method was performed to evaluate their hydrocarbon potential. Kerogens of both environments and subenvironments are of Type III and Type IV. Both submarine fans present considerable TOC content, but the ‘basin floor’ fan is the most enriched sub-environment. Shelf is presented in an immature oil stage, whereas both ‘slope’ and ‘basin floor’ fans are in the immature/mature oil stage.

Temporal and spatial distribution of 137Cs in Eastern Mediterranean Sea. Horizontal and vertical dispersion in two regions

Caesium-137 activity concentration in the water columns of the Gulf of Patras (Central Greece) and the North-Eastern Aegean Sea (easterward to Lemnos Island) was investigated in selected sampling stations during the period September 2004–June 2006. The methodology followed was based on the sorption of caesium (Cs) on cotton wound cartridge filters impregnated by Cu 2[Fe(CN) 6] via in-situ pumping. In terms of the horizontal and vertical records, the activity concentrations of 137Cs in the Gulf of Patras ranged between 1.2 and 6.7 Bq m −3, depending on the sampling period and the prevailing physicochemical regime at the sampling station. The general pattern of the decreased activity concentrations of 137Cs with increasing depth was reversed in the Gulf of Patras during the cold period attributed to the prevailing advective processes of the area. The activity concentrations of 137Cs in the North-Eastern Aegean Sea ranged from 2.6 to 12.8 Bq m −3, whereas significant stratified curves were observed during the warm period and also, in one station during the cold period. In terms of temporal variation, the discharges in the Gulf of Patras resulted in enhanced levels of 137Cs, whereas in the North Aegean Sea the incoming water masses form the Black Sea had an apparent influence throughout the year by increasing the 137Cs levels, hence presenting a weak seasonal variation. Comparing the two studied areas, one could say that the North Aegean Sea, as an open sea environment, presented higher concentrations due to the influence of the Black Sea water masses. The estimated inventories of 137Cs in the Gulf of Patras ranged 0.25 ± 0.03–0.79 ± 0.03 kBq m −2, whereas in the North-Eastern Aegean Sea they ranged 0.33 ± 0.02–0.92 ± 0.03 kBq m −2.