Yazar "Candaş, Adem" ile AYBE- Katı Yer Bilimleri Lisansüstü Programı - Yüksek Lisans'a göz atma
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ÖgeReconstruction Of The Paleoclimate On Dedegol Mountain With Paleoglacial Records And Numerical İce Flow Models(Eurasia Institute of Earth Sciences, 2017-05-05) Candaş, Adem ; Sarıkaya, Mehmet Akif ; 602151009 ; Solid Earth Sciences ; Katı Yer Bilimleri Anabilim DalıThe current glaciers in Anatolia have been gradually disappearing with the ongoing climate changes. There are geological proxies left behind from the ice, which is an indication of paleoclimate changes. It is known that the glaciers carry large amounts of sediments in their life cycles. After they retreat, these sediments remain where they were. They are called as moraine, which has been well preserved in some Anatolia mountains. In this study, the paleoglaciers that existed in the Late Quaternary period on the Dedegöl Mountain were reconstructed under the prescribed paleoclimatic conditions. The main idea is to recreate paleoglaciers under different climatic conditions; it is the recreation of the paleoclimate. This approach, in a sense, is aimed at understanding the past-term climate. Thus the proxies left behind by the glaciers have been used as an important proxy to estimate the paleoclimate conditions. Dedegöl Mountain is located within the boundaries of Konya and Isparta provinces. The maximum elevation of the mountain is 2997 m above the sea level. Beys ̧ehir Lake is located about 15 km to the east of the study area. 30 m × 30 m resolution digital elevation model of Dedegöl Mountain was used. The model domain is covering 37.5670 - 37.7237 North latitudes and 31.2100 - 31.3667 East longitudes. The model area is about 16.92 km × 16.92 km = 286 km2. Glacial mass balance was calculated with today's climatic conditions. Then the paleoclimate was modeled. A two-dimensional numerical glacier flow model was written in MATLAB to reconstruct the flow of glaciers under different paleoclimatic conditions. An open source glacier flow model software named Parallel Ice Sheet Model (PISM) was also used. The glacier valleys in the area are identified during two field studies in the summer months of 2015 and 2016. The Sayacak Glacial Valley on the north, the Elmadere Glacial Valley on the east, the Muslu and Karagöl and the Karçukuru Glacier Valleys in the south and the Kisbe Glacial Valley in the north-west were studied. The moraine crests positions were identified and paleoglacier boundaries were determined. Then, paleoclimatic conditions of that fit the modeled glacier extent were determined. Positive Degree Days approach was used to calculate the ablation of a glacial. This approach is briefly based on the idea that there is a correlation between the sum of all the temperatures above the melting point and melting of snow (or ice) at the same location over a year. A decrease in glacial mass occurs for days with a temperature higher than 2°C. In the calculation of the accumulation mass, the amount of precipitation in the area is used. If the precipitation occurs at a temperature higher than 0°C degrees, all precipitation occurs as rain. The accumulation linearly increases between 2 and 0°C and it contributes to the annual mass balance. The precipitation is considered to be entirely snow below 0°C air temperature. Therefore, glacier's annual budget is based on the difference between accumulation and ablation. It is thus possible to establish a direct relationship between the amount of ice in a particular area and climate conditions. In these calculations, factors such as surface energy mass, the cloudiness, and the wind effect can be also used, but these factors are not included in this study. Previous studies in the region have indicated that paleoclimate was cooler and wetter than present-day climate during the Last Glacial Maximum period. It is stated that the temperatures were 8 to 11°C lower than today, with the precipitation being 20% higher. In this study, temperatures in the model of paleoglaciers were decreased by 8, 9, and 10°C. Precipitation values were increased by 0%, 25% and 50% than today. The best way as a glacial flow model is to solve the Full Stokes equations. However, the solution of these equations is not efficient in terms of processor requirements and time. Different models have been developed for the flow of glaciers moving. In this work, open source software named Parallel Ice Sheet Model (PISM) was used. However, a two-dimensional time-dependent glacial flow model has also been developed. The results obtained in these two models were discussed. PISM uses the netCDF file type as input. In this file, data such as temperature, precipitation, glacial thickness were stored. Within the scope of the thesis, a code was developed to provide appropriate data input for PISM. This code calculates the glacial mass balance under the paleoclimatic conditions and then transforms this data into an input for PISM. The results obtained from the study include: (1) although the Parallel Ice Sheet Model (PISM) has been developed for modeling larger-scale ice sheets, it is proved it can be also used as a model for valley glaciers, such as Dedegöl Glacier Valleys (2) a temperature depression between 10°C with an increase in precipitation of 25%, and 9°C with 25% for LGM and Early Holocene respectively, (3) existing digital elevation data used in the models may cause some degradation of glacier reconstruction because they contain moraine deposits of different glacial periods, (4) the results obtained from the models indicate that the moraine deposits formed at different times should be evaluated with different climatic conditions. There are various sources of uncertainty in the model. Firstly, the resolution of the climate models is 570 m. The digital elevation model resolution is 30 m, so this dismatching can create some uncertainty. However, sudden elevation changes in the digital elevation model can lead to high slopes. From the past, it can be assumed that the boundaries of the changing structure with erosional processes created uncertainty. Moreover, seasonal fluctuations in climate data can create uncertainty in the model. In further studies, the removal of the moraine deposits to reconstruct the digital elevation model will positively affect the ice flow. This is because these obstacles prevent the glaciers to advance to the past moraines. The glacier flow and climate models applied in this study can be used in other paleoglacial areas in the region which can increase the proxy data about Turkey's paleoclimatic conditions.