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ÖgeThe impact of climate change on future extreme precipitation in Turkey(Graduate School, 2021-08-06) Albayrak, Derya ; Şen, Ömer Lütfi ; 601191005 ; Earth System Science ; Yer Sistem BilimiThis study investigates the impact of climate change on extreme precipitation in Turkey with the aid of both historical and model-based future projection data. Firstly, we have applied the equidistant quantile matching method and generated bias-adjusted extreme precipitation daily and sub-daily time series of 73 stations in Turkey from a 14 member CMIP6 ensemble. The resulting data are utilized for deriving the Intensity-Duration-Frequency curves for two future periods (2020-2050 and 2070-2100) and results are spatially presented. Thus, annual extreme precipitation with 1-hr, 2-hr, 6-hr, 12-hr, and 24-hr durations over Turkey are examined for 10-yr, 25-yr, 50-yr, and 100-yr return periods in two future periods through a CMIP6 ensemble-based analysis. The impacts of climate change on annual extreme precipitation in the regions of Turkey are estimated. Our CMIP6-ensemble analyses reveal that for the reference period 1970-2000 the highest impacts over Turkey are estimated for shorter duration (≤ 6-hr) generally higher-frequent annual extreme precipitation which may be attributed to the thermal enhancement due to the mean temperature increase in Turkey. Moreover, for all durations and frequencies covered here, till the mid-century, change in regional medians varies between 4.6-10.4% in the Marmara region, 4.9-8.4% in south-eastern Anatolia, 7.4-10.4% in the Aegean region, -1.8-0.8% in central Anatolia, 6.8-12.1% in eastern Anatolia, 5.2-7.2% in Black Sea region, 4-14.2% in Mediterranean region. Due to the high spatial variability of the extreme precipitation, both decreasing and increasing relative changes occur in the regions. However, by the end-century, the impact of annual extreme precipitation in the regions noticeably intensifies, relative regional medians raise to 18.5-21.7% in Marmara region, 14.8-18.7% in south-eastern Anatolia, 10.2-13.9% in Aegean region, 13.4-16.6% in central Anatolia, 19.3-23.3% in eastern Anatolia, 16.2-20.7% in Black Sea region, 15.1-21.1% in Mediterranean region. Coastal regimes in Turkey receive a higher amount of annual extreme precipitation than the continental parts, especially local extremes that are noticeable on the coastal line, which is projected for all future periods and extreme precipitation durations presented in this study. Moreover, according to the median of the relative changes among the regions, the south and north coasts of Turkey are subject to the impact of different annual extreme precipitation durations. Northern coastal regimes are projected to have the highest impact by the intensification of the short-duration annual extremes (≤ 2-hr annual extreme precipitation). Southern coastal regimes are estimated to have the highest impact by the longer duration (≥ 6-hr) annual extreme precipitation events. Central Anatolia, the only region with persistent decreasing median changes till the mid-century, experiences a substantial increase in the impact of the 1-hr and 2-hr high-frequent convective precipitation extremes at the end-century. Crucial for adaptation and mitigation strategies, our current practice of deriving and implementing Intensity-Duration-Frequency curves rely on the historical data, which may be insufficient for capturing the variable impacts of climate change. Consequently, underestimating the impact of climate change on extreme precipitation may result in a decrease in the capacity of the numerous hydrological systems to deliver the required services at their optimum. Thus, decision and policymakers should evaluate and consider the intensification of different extreme precipitation durations among both the regions and the future periods to eliminate the exacerbated vulnerability of the hydrological systems to climate change-related extreme precipitation events and manage adverse socio-economic consequences.
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ÖgeEcological niche modeling of Myotis davidii(Graduate School, 2022-06-09) Aksakal, Emre Can ; Çoraman, Emrah ; 601181012 ; Earth System ScienceMyotis davidii is a whiskered bat species distributed in large areas of the Western Palaearctic. It has a cryptic sister species, Myotis mystacinus, which also has a similar distribution range in Europe and western Asia. The distribution of M. davidii extends from the Balkans to the Far East Asia, whereas M. mystacinus is found in Europe, Anatolia, and the Caucasus. They have a sympatric range in an area extending from the Balkans to the Transcaucasia via Anatolia. In this sympatric area, the populations of M. davidii had discordant patterns of mitochondrial and nuclear DNA, indicating that there were gene exchange between these species in the past. In this study, it was aimed to investigate the effects of the past climatic conditions on the evolutionary history of M. davidii and its cryptic sister species, M. mystacinus. The particular aims of this thesis are: 1) to construct the bioclimatic niches of M. davidii and M. mystacinus; 2) to identify their putative refugial areas during the last glacial period; and 3) to assess their responses to current climate change. In order to investigate these aims, ecological niche models were utilized. Ecological niche models aims to predict the distribution range of species by matching the environmental factors with species occurence points. Ecological niche modeling approach has become a common and practical application in conservation and biogeography study, especially with the advent of computer sciences and essential databases. In this study, ecological niche models are constructed by using the R programming language, as implemented in the BIOMOD2 package. A maximum entrophy appoach was used, which is a machine learning method developed for ecological niche modelling applications. The constructed models captured the current range of M. davidii but failed for M. mystacinus. For Myotis mystacinus, the lack of data from the Balkans and Anatolia was the likely reason for the unsuccessful model projections. The models for M. davidii suggest that inaccordance with the genetic lineages there might be to separate ecological units. Past projections suggest that Anatolia and the Balkans might have acted as refugial areas for both of the species during the Last Glacial Maximum. For M. davidii, the coastal regions of the Black Sea and the Mediterranean regions of Anatolia were likely refugial areas. These findings highlights the importance of Anatolia as a glacial refugium. Finally, the future projections suggested that there will major range shifts in the distribution of these species, especially for M. mystacinus moving towards norther Europe.
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ÖgeFire history and climate change: Black pine forests in Western Anatolia(Graduate School, 2022-06-15) Şahan, Evrim Ayşe ; Dalfes, Hasan Nüzhet ; Köse, Nesibe ; 601172003 ; Earth System ScienceWildfire is a part of the ecological processes that is highly important for the sustainability of forest ecosystems in the Mediterranean Basin. Species adapted to crown fires, such as Turkish pine, are capable of regeneration after a fire and establishing new forests. On the contrary, tree species such as black pine adapted to surface fires have regeneration problems after severe crown fires, and mass extinctions in some regions can be observed. Many studies have revealed that the fire frequency of forests in the Mediterranean Basin is expected to increase due to climate change and the fire regime of black pine forests will shift from surface fires to crown fires. In order to understand the fire regime changes in the black pine forests in the Mediterranean Basin, including Turkey, centuries-long fire records are needed. Thus, dendrochronology is one of the most reliable and effective methods commonly used in fire history studies. In this doctoral thesis, the aims are to develop a high-resolution fire reconstruction of black pine forests in Turkey, determine the seasonality of historical fires, understand the association between climate variability and fire occurrence, understand the variability of spatiotemporal patterns of fires throughout the main distribution areas of black pine forests in Turkey using tree-ring analysis, and monitor the cambium activity in black pine forest. Several spatial and temporal studies are conducted in order to understand the effects of fire management strategies, climate types or geographical gradients on regional fire regimes in the world. A large number of dendrochronology-based studies were conducted, especially in North America, to understand the spatiotemporal patterns in different geographical gradients and different climate types and also corroboration of empirical data. However, in the Mediterranean basin, a few fire history studies based on dendrochronological methods was conducted in Greece, France and Spain to understand the regional fire regime and the relationship between fire and climate. To my knowledge, there is no any conducted fire history study for any species based on tree-ring analysis in Turkey. A total of 211 samples were collected from ten sites throughout western Anatolia. The collected samples were dated by standard dendrochronological methods and the seasonality of each sample was determined. The site-level composite and regional fire chronologies were created for Kütahya, Isparta, Bolu, and western Anatolia. The major fire years were calculated with the criteria that greater than or equal to 25% of recording samples have fire scars on that year in at least two of the samples, while the regular fire years were determined by recording samples have fire scars on that year in at least two of the samples. The relationship between the major fire years and climate was analysed using Superposed Epoch Analsis. Understanding the seasonality of historical forest fires facilitates the development of concepts related to fire as an ecological and evolutionary process. In order to understand the fire regime of a region, determination of the seasonality is a must. In dendrochronology-based fire history studies, the seasonality of fire scars is mostly classified according to the intra-ring position of the fire scars as a classical method. However, studies of cambial phenology are needed to accurately correlate the position of a fire scar with the months in a year. Because the timing of the earlywood and latewood production (cambial cell production) varies according to the species, location and climate. In this context, the aim of this part of this thesis is to determine in which months the cambium activity of black pine forests starts and in which month the early/latewood cells form. In order to monitor cambium activity, a total of 144 microcores were sampled from three sites near the fire history reconstruction sites during a vegetation period (April-November 2021). Monitoring the cambial activity helped to obtain information about which month(s) are risky for forest fires. The first tree-ring based 553-year long fire history reconstruction and cambial activity of black pine forests were presented to improve our understanding of the regional fire regime components with the effect of climate in Turkey. The fire return interval of black pine forests in Anatolia was calculated from a minimum of one year and a maximum of 105-year intervals over the study period. The seasonality of most of the fire scars in western Anatolia occurred in the latewood period. As conducted in a cambial activity study of black pine forests in western Anatolia, latewood tracheid cells are formed from (August in Isparta) from September to November. Since most of the fires in western Anatolia occur in latewood, the risky months for fires in the study area are from (July in Isparta) August to November (the late summer and autumn) based on xylogenesis studies. The relationship between climate and fire years calculated with regional fire chronologies showed that the major fires in Kütahya and Bolu are associated with dry years, while the wet conditions two years prior to major fire events in Isparta. The decrease in fire frequency was observed in the late 19th and early 20th centuries due to human-induced fire suppression activities. That can cause the accumulation of combustible material and pose a risk for more intense fires. Based on future climate projections, as a result of increased drought frequency, we will face extended fire seasons that may shift the fire regime from the surface to crown fires and even cause mega fires. A large number of simultaneous fires were recorded in the period between the mid-1800s and the early 1900s. The decrease in fire frequency after the early 1900s coincides with the first forest protection law in 1937. As a result of the comparison of fire years in western Anatolia, Spain, and Greece, more common fire years were found in studies of Greece than in Spain. The differences in climate conditions of the eastern and western Mediterranean due to frontogenesis or depressional activity might explain these different common fire years. The year 1879 was the most extensive fire year in Greece in the 19th century and it was recorded as one of the most common fire years in western Anatolia. The year 1945 was the only common fire year in the Mediterranean region sites. Results in this study showed that the fires in 1945, observed simultaneously in Anatolia, Greece, and Spain, occurred in the most severe and widespread drought among the spatially visualized common fire years. In this study, long-term fire history data were developed by using dendrochronological methods to understand the fire regime of black pine forests for the first time in Turkey. These fires were analyzed with a new approach with the determination of the seasonality by taking samples with microcores. Unlike studies only current fires are analyzed or fire history reconstructions, the results were obtained by integrating both ecological and statistical methods.
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ÖgeDistribution of radionuclides in Arıklı region (Çanakkale/Ayvacık) and possible causes(Graduate School, 2022-06-28) Top, Gülcan ; Tutay Örgün, Yüksel ; Karahan, Gürsel ; 601112002 ; Earth System ScienceThe aim of this thesis is to determine the indoor and outdoor gamma dose rates in Arıklı (Çanakkale/Ayvacık/Turkey) uranium mineralization region, to determine the activity concentrations of 226Ra, 232Th, 40K in selected samples (building materials, rocks, surface soils, beach sands and soil samples collected from excavation ditches), to map the outdoor gamma dose rates and the activity concentrations of the radionuclides specified in the surface soils using geographic information systems, to identify the geological sources that cause high doses and to evaluate the possible health risks for the region based on all these measurement results. The measurement of mass concentrations for U, Th on some selected samples is also included into the study. This study is the first comprehensive study for the region. For this thesis, the Arıklı region was considered as a research area due to the presence of a uranium mineralization zone and the prevalence of felsic volcanic rocks containing above-average uranium, thorium and potassium concentrations. In order to determine the level of radioactivity in the Arıklı uranium mineralization region, preliminary field studies were started in 2015 measuring the outdoor gamma dose taking into account the geological formations. It has been determined that anomalies are especially concentrated in and around the drilling points determined by the General Directorate of Mineral Researches (MTA) to search for uranium.
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ÖgePotential implications of sea-level rise in Türkiye and its vicinity(Graduate School, 2022-10-08) Alabay, Ebru ; Karaca, Mehmet ; Baykara, Metin ; 601201007 ; Earth System SciencesIn the last century, the sea-level rise has accelerated due to anthropogenic climate change. With the growing population, the consequences of climate change have become more adverse. As in the rest of the world, the population pressure is high on the Turkish Coasts, where 45 million people live in. Türkiye, which has a long shoreline with 8333 km covered with seas on three sides will be affected adversely by the consequences of accelerated sea-level rise (e.g. flooding, salt intrusion, erosion, etc.). In addition to physical hazards, also socio-economic losses will have consequences. The purpose of this study is to determine the potential implications of the sea-level rise on Turkish coasts. For this purpose, the monthly sea-level data in the Turkish Seas (the Black Sea, the Marmara Sea, the Aegean Sea, and the Mediterranean Sea) are received from the Permanent Service for Mean Sea Level. However, some tide gauge stations have data gaps and insufficient data for determining long-term sea-level change. Therefore, cubic interpolation was applied to eliminate the data gaps, also the tide gauge station data in the same sea are combined to create a longer time series of sea-level change. Thus, the mean sea-level rise rates in the Black Sea, the Marmara, the Aegean, and the Mediterranean Sea are calculated at 5,31 mm/yr in 1874-2018, 8,79 mm/yr in 1984-2009, 0,844 mm/yr in 1969-2019, 0,8455mm/yr in 1923-2019, respectively. It is determined that sea-level rise has accelerated in recent decades. The accelerated sea-level rise causes the increasing frequency and intensity of disaster floods, inundations, coastal erosion, landslides, saltwater intrusion, and even storm surges. The main economic activities in this region are tourism, agriculture, fishing, port, and industry sectors. In Turkey, the coastal low-lying delta areas (i.e. Cukurova, Bafra, Carsamba, Meric, Goksu, etc.) are important in agricultural production. Especially one-third of Samsun is covered with agricultural lands its agricultural contribution to the economy is approximately $1 billion. Thanks to their long sandy beaches, the Mediterranean and the Aegean are among the destinations that attract a lot of international tourists and play an important role in the development of the region locally and nationally. Another popular destination for international tourists is Istanbul with its natural beauty, rich culture, and historical places. Hence, the socio-economic factors on the Turkish coast were examined. The contribution of the coastal region is estimated at two-thirds of the Turkish Gross Domestic Product (GDP): the Marmara, the Aegean, the Mediterranean, and the Black Sea coastal regions' contributions are 44.5%, 8.3%, 8.4%, and %4.7 respectively. As a result, these economically active regions are essential to be protected against sea-level rise. In this study, adaptation strategies have been determined for the protection of coastal areas from the destructive consequences of sea-level rise. In addition, the adaptation costs for agricultural areas (Bafra and Carsamba) in Samsun, and the sandy beaches are also examined.
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ÖgeTemporal and spatial investigation of maritime accidents in the strait of Istanbul in the perspective of navigational safety(Graduate School, 2022-10-24) Kodak, Gizem ; Ünal, Alper ; Acarer, Tayfun ; 601142001 ; Earth System SciencesThe Strait of Istanbul is located on the primary routes of international maritime transport. The strait, which is the second busiest waterway in the world with average of 50.000 ships per year, has four times more maritime traffic than the Panama Canal and three times more than the Suez Canal. When compared to its peer waterways the biggest threat in the Strait, the risk of accidents created by difficult navigational conditions. Some of the accidents that took place in the strait in the recent past have caused worldwide concern due to the environmental disaster they have caused. Considering that today, ships carrying dangerous goods serve at much larger capacities compared to the past, the maritime traffic in the region poses a risk both for the ships passing and for the city and people of Istanbul, which is densely populated on its shores. In this context, the development of solutions to reduce maritime accidents in the region plays a key role in strengthening navigational safety. In this study, the accidents that took place in the strait were discussed in terms of temporal/spatial and were examined simultaneously with the environmental factors affecting the navigational safety. For this purpose, hourly wind speed and wind direction data of Sarıyer and Atatürk meteorology stations located on the traffic route in the strait were obtained from the Turkish State Meteorological Service and wind dynamics affecting maritime traffic were examined. On the other hand, accidents also were evaluated in terms of the number of ships passing and the effect of maritime traffic on accidents were examined with the regression analysis. In this direction the monthly movement of international ship traffic in the strait was examined on a micro scale with the data of the Directorate General of Coastal Safety and accident rate per passing ship was calculated. In addition to dynamic factors such as wind speed, wind direction and traffic flow, another factor affecting the occurrence of accidents in the strait is the navigational regulations carried out in relation to the traffic order. In this context, the regulations for maritime traffic in the strait were examined chronologically and compared with the accident data. Thus, not only the effects of the regulations regarding navigational safety on the accidents were observed, but also the strengths and weaknesses of the developed solution proposals were revealed. The results of the study have shown that patrol tugs can be an effective solution to prevent accidents when the wind and current dynamics in the region and the spatial distribution of the accidents are evaluated together. In this direction, the response time of the proposed patrol tugboats to a possible accident was calculated and the response options were evaluated under two different scenarios as parallel to the current and antiparallel.