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Yayın Impact of climate change and land cover dynamics on nitrate transport to surface waters(Springer Science and Business Media Deutschland GmbH, 2024-03) Boyacıoğlu, Hülya; Günaçtı, Mert Can; Barbaros, Filiz; Gül, Ali; Gül, Gülay Onuşluel; Öztürk, Tuğba; Kurnaz, M. LeventThe study investigated the impact of climate and land cover change on water quality. The novel contribution of the study was to investigate the individual and combined impacts of climate and land cover change on water quality with high spatial and temporal resolution in a basin in Turkey. The global circulation model MPI-ESM-MR was dynamically downscaled to 10-km resolution under the RCP8.5 emission scenario. The Soil and Water Assessment Tool (SWAT) was used to model stream flow and nitrate loads. The land cover model outputs that were produced by the Land Change Modeler (LCM) were used for these simulation studies. Results revealed that decreasing precipitation intensity driven by climate change could significantly reduce nitrate transport to surface waters. In the 2075–2100 period, nitrate-nitrogen (NO3-N) loads transported to surface water decreased by more than 75%. Furthermore, the transition predominantly from forestry to pastoral farming systems increased loads by about 6%. The study results indicated that fine-resolution land use and climate data lead to better model performance. Environmental managers can also benefit greatly from the LCM-based forecast of land use changes and the SWAT model’s attribution of changes in water quality to land use changes. Graphical abstract: (Figure presented.).Yayın Cement fabrics and optical luminescence ages of beachrock, North Cyprus: Implications for Holocene sea-level changes(Elsevier Ltd., 2016-05-16) Öztürk, Muhammed Zeynel; Erginal, Ahmet Evren; Güneç Kıyak, Nafiye; Öztürk, TuğbaCaCO3-cemented beachrocks are widely found along the northern coast of Cyprus. In this study, we aim to discuss the cementation history of beachrocks at ten particular sites within the context of Holocene sea-level changes. Cement fabrics, petrographic and geochemical characteristics, and optically-stimulated luminescence ages of buried quartz grains were studied. The seaward-inclined (~5-10°) parallel-stratified beds are composed mostly of sandstone alternating with conglomerate. Ooids, benthic and planktic foraminifera, bioclasts of red algae, echinoid spines and gastropods make up a significant proportion of the cemented beds. With CaCO3 content ranging between 37% and 65%, poorly-sorted grains are bonded by four distinct cements: circumgranular micritic coatings, sparry calcite infillings, pore fills, and meniscus bridges. This consecutive nature of cementation is typical of a marine phreatic and meteoric vadose environment when the sea level was lower than present but had a tendency to increase during middle to late Holocene. OSL ages ranging from 5.4 ka to 0.38 ka indicate that the deposition and ensuing cementation of the quartz grains occurred during two main stages; younger beds dated between 2.3 ka and 0.38 ka and older beds from 2.3 ka to 5.4 ka. A period devoid of beachrock formation was attested between 3.5 ka and 2.3 ka.Yayın Projected future changes in extreme climate indices over Central Asia using RegCM4.3.5(MDPI, 2023-06) Öztürk, TuğbaThis work projected future extreme climate indices' changes over Central Asia (The Coordinated Regional Climate Downscaling Experiment-CORDEX Region 8). Changes were calculated for 2071-2100 relative to 1971-2000. Climate simulations were obtained by downscaling the RegCM4.3.5 to 50 km resolution under RCP4.5 and 8.5 with HadGEM2-ES and MPI-ESM-MR. The results indicate that the Central Asian domain will experience warmer and more extreme temperatures with increasing radiative forcing. The annual lowest value of minimum daily temperature was simulated to increase remarkably, up to 8 degrees, especially in high latitudes, with a more than 12 degree increase projected over Siberia. A strong growth in the percentage of warm nights and an increase in the days of warm spells for the whole region, with a decrease in cold spell duration, are anticipated. Model results show an expected reduction of up to 30% in precipitation totals over the domain, except for the increased precipitation over Siberia, the Himalayas, and Tibetan Plateau. Extreme precipitation events are projected to have an increase of 20% over the whole domain, with an 80% increase over high topographical areas.Yayın Projected changes in extreme temperature and precipitation indices over CORDEX-MENA domain(MDPI AG, 2021-05) Öztürk, Tuğba; Saygılı Aracı, Fatma Sibel; Kurnaz, Mehmet LeventIn this study, projected changes in climate extreme indices defined by the Expert Team on Climate Change Detection and Indices were investigated over Middle East and North Africa. Changes in the daily maximum and minimum temperature-and precipitation-based extreme indices were analyzed for the end of the 21st century compared to the reference period 1971–2000 using regional climate model simulations. Regional climate model, RegCM4.4 was used to downscale two different global climate model outputs to 50 km resolution under RCP4.5 and RCP8.5 scenarios. Results generally indicate an intensification of temperature-and precipitation-based extreme indices with increasing radiative forcing. In particular, an increase in annual minimum of daily minimum temperatures is more pronounced over the northern part of Mediterranean Basin and tropics. High increase in warm nights and warm spell duration all over the region with a pronounced increase in tropics are projected for the period of 2071–2100 together with decrease or no change in cold extremes. According to the results, a decrease in total wet-day precipitation and increase in dry spells are expected for the end of the century.Yayın Records of repeated drought stages during the Holocene, Lake Iznik (Turkey) with reference to beachrock(Pergamon-Elsevier Science Ltd., 2016-07-15) Öztürk, Muhammed Zeynel; Erginal, Ahmet Evren; Güneç Kıyak, Nafiye; Demirci, Alper; Ekinci, Yunus Levent; Cürebal, İsa; Avcıoğlu, Mustafa; Öztürk, TuğbaThe cement fabrics, subsurface nature and optically stimulated luminescence age of beachrocks along the shores of Lake Iznik in NW Turkey were studied within the context of Holocene lake level changes. With a maximum thickness of 1.5 m, the low-angle (average 5-10 degrees) beds are composed of coarse grains and small gravels and extend up to 5 m offshore at their most lakeward extremities. Cement textures on and around the poorly-rounded grains are made up of micrite envelopes and meniscus bridges as well as acicular aragonite rims. Geoelectrical resistivity sections taken from a representative location along the beach where the beds have maximum thickness showed that the sand-buried beds are followed up to about 24 m landward. Based on the OSL ages of 33 samples, the cemented beds occurred at four drier periods of the following: Pre- and Early Holocene (dated to 15-9 ka), Holocene Climatic Optimum (7.9-5.6 ka), Middle Holocene (4.9 ka-2.8 ka) and Late Holocene (2.0 ka-0.9 ka).Yayın Impact of climate change on natural snow reliability, snowmaking capacities, and wind conditions of ski Resorts in Northeast Turkey: a dynamical downscaling approach(Mdpi Ag, 2016-04) Demiroğlu, Osman Cenk; Turp, Mustafa Tufan; Öztürk, Tuğba; Kurnaz, Mehmet LeventMany ski resorts worldwide are going through deteriorating snow cover conditions due to anthropogenic warming trends. As the natural and the artificially supported, i.e., technical, snow reliability of ski resorts diminish, the industry approaches a deadlock. For this reason, impact assessment studies have become vital for understanding vulnerability of ski tourism. This study considers three resorts at one of the rapidly emerging ski destinations, Northeast Turkey, for snow reliability analyses. Initially one global circulation model is dynamically downscaled by using the regional climate model RegCM4.4 for 1971-2000 and 2021-2050 periods along the RCP4.5 greenhouse gas concentration pathway. Next, the projected climate outputs are converted into indicators of natural snow reliability, snowmaking capacity, and wind conditions. The results show an overall decline in the frequencies of naturally snow reliable days and snowmaking capacities between the two periods. Despite the decrease, only the lower altitudes of one ski resort would face the risk of losing natural snow reliability and snowmaking could still compensate for forming the base layer before the critical New Year's week. On the other hand, adverse high wind conditions improve as to reduce the number of lift closure days at all resorts. Overall, this particular region seems to be relatively resilient against climate change.Yayın Tectonic and climatic controls on Quaternary fluvial processes and river terrace formation in a Mediterranean setting, the Goksu River, southern Turkey(Cambridge University Press, 2019-03) Avşin Görendağlı, Nurcan; Vandenberghe, Jef; Van Balen, Ronald; Güneç Kıyak, Nafiye; Öztürk, TuğbaClimate and tectonics effect the fluvial evolution of the Mediterranean Mut basin. The basin contains a river terrace staircase of 16 levels (T16-T1) ranging from 365 to 10m above the current Goksu River in its middle and lower sections. These river terraces records tectonic uplift in the Mut basin. Optically stimulated luminescence (OSL) dating of the fluvial sediments of the youngest terrace (T16) provides a chronology for the assessment of the important impacts of climatic changes. The ages from the youngest river terrace deposits in T16 may be subdivided into two intervals: (1) 239-194.7 ka during the later part of Marine Oxygen Isotope Stage (MIS) 7, implying that the aggradation of T16 started in (the final phase of) this warm period; and (2) 187.9-171 ka during much of MIS 6. Thus, it appears that the Goksu River continued depositing sediment from an interglacial into a glacial time. The differences in climate-driven fluvial evolution between this Mediterranean fluvial system and the classical, well-studied temperate-periglacial river systems in Europe may be the result of different vegetation cover and greater thaw of more intense snowfalls.
