باز سازی برف مرزهای دائمی کواترنر پایانی در ارتفاعات جنوبی ایران مرکزی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشیار گروه جغرافیای طبیعی، دانشکده علوم جغرافیایی و برنامه ریزی، دانشگاه اصفهان

2 دانشگاه اصفهان

10.22034/gmpj.2021.280051.1266

چکیده

بازسازی شرایط اقلیمی گذشته با توجه به پدیده‌های فرمی یخچالی و ارتباط آنها با ارتفاع خط تعادل آب و یخ صورت می-پذیرد. بازسازی ارتفاع خط تعادل یخچال‌های عهد حاضر و دیرینه از جمله پارامتری است که از آن به عنوان یک شاخص تغییر اقلیم استفاده می‌شود. هدف اصلی این پژوهش؛ بازسازی ارتفاع خط تعادل آب و یخ (ELA) در ارتفاعات ایران مرکزی در استان کرمان بر اساس شواهد ژئومورفیک یخچالی و با استفاده از روش لویز، هوفر و کف سیرک پورتر است. برای این کار با استفاده از بازدید میدانی مورن‌های پایانی در امتداد دره‌های اصلی شناسایی و ارتفاع آنها با استفاده از GPS اندازه‌گیری شد. پس از تهیه لایه‌های مختلف مورد نیاز در نهایت نقشه ژئومورفولوژی منطقه ترسیم و مکان دقیق مورن‌ها بر روی آن مشخص گردید. نتایج نشان می‌دهد که ارتفاع بالاترین و پاینترین ELA در هفت واحد مطالعاتی بر مبنای روش‌های فوق به ترتیب عبارتند از: بالاترین مقدار ELA بر اساس روش لویز 4063 متر در ارتفاعات هزار و کمترین آن 2858 متر در ارتفاعات جوپار است. همچنین بالاترین مقدار ELA بر اساس روش هوفر 3875 متر در ارتفاعات هزار و کمترین آن 2682 متر در ارتفاعات جوپار است. در حال حاضر مقدار ELA منطقه مطالعاتی بر اساس آمار اقلیمی 4629 متر است. بالاترین مقدار ELA بر اساس روش کف سیرک (پورتر) در ارتفاعات هزار 3518 متر و پایین ترین آن در ارتفاعات جبال بارز با ارتفاع 2953 متر بوده است. ارتفاع ناهمواری‌ها و برفگیر بودن آنها علت اصلی تفاوت ELA در این واحدهای کوهستانی است.

کلیدواژه‌ها


عنوان مقاله [English]

Snow reconstruction of the final Quaternary boundaries in the highlands of south-central Iran

نویسندگان [English]

  • Abdullah Seif 1
  • Hojatallah Beranvand 2
1 Associate Professor of Natural Geography, Faculty of Geography and Planning, Isfahan University
2 University of Esfahan
چکیده [English]

Introduction
In the current situation, although it is not possible to form glaciers in many heights of Iran, it must be acknowledged that exploiting the potential of water and soil is impossible without considering the climatic processes of the fourth period. Therefore, geoscientists, especially in the last two decades, have tried to estimate the height of the border snow and the water and ice balance line of the Quaternary Iran as accurately as possible in order to be more successful in presenting land management plans.To. Reconstruction of past climatic conditions takes place according to glacial Fermi phenomena and their relationship with the height of the equilibrium line (ELAs). The height of the equilibrium line of present and ancient glaciers is one of the parameters that is used as an indicator of climate change.


Methodology
At the altitudes of the study area according to glacial geomorphic evidence such as; Existing circuses, alluvial fans, various terminuses and traces of old lakes, 81 glacial sub-basins were identified within these altitudes. To determine the exact boundaries of the glacial basins, the hydrological map of the study area was made based on Staller classification from the DEM map. According to the height of these terminals, the exact height of the permanent snow line has been determined using the Lewis and Hofer methods. Also, using the circus floor method (Porter), the amount of past ELA was reconstructed at these heights. Reconstruction of past temperature and precipitation conditions and estimation of current line equilibrium height (ELA) using climatic data based on average annual temperature and precipitation data of 11 synoptic meteorological stations and based on the year of their establishment in different periods Took.

Results and discussion
According to the above figure and the obtained linear relationship between the average annual temperature and the height of ELA meteorological stations, currently 4629 meters were calculated in the study area. Comparing the past ELA with the present, we can see that the ELA line has changed a lot and is now much higher due to the warmer weather. According to the regression equation obtained between the average annual temperature and the height of synoptic and ELA stations obtained in the present and past, the adiabatic drop of the current temperature of the study area with a decrease of approximately 5.89 degrees per thousand meters. Estimated. Due to the adiabatic drop in temperature in the region during the rule of glaciers, the air temperature was 6.54 degrees colder at altitudes and the air temperature in the highlands was 9.86 degrees colder than now. Among these mountainous units, the highest ELA has been reconstructed using the Louise method at an altitude of 4063 meters and using the Hofer method at an altitude of 3875 meters at an altitude of one thousand and below the Rusk Glacier Basin. Also, the lowest ELA was reconstructed using the Louise method at an altitude of 2858 meters and using the Hofer method at an altitude of 2682 meters at the Jupar heights and below the Agharzi glacial basin. Reconstruction of the highest ELA according to Porter method at the heights of Hezar at an altitude of 3518 meters and the lowest at the heights of Barez with a height of 2953 meters The highest height of the glacial circus floor below the Sirch basin is at the heights of Plovar with a height of 3,703.2 meters and the lowest height of the circus floor below the difference basin is at the height of Jabal Barez with a height of 2912 meters.

Conclusion
In general, the ELA level in the northern slopes in the study area is lower than the ELA level in the southern slopes of these heights. Among these mountainous units, the highest ELA has been reconstructed using the Louise method at an altitude of 4063 meters and using the Hofer method at an altitude of 3875 meters at an altitude of one thousand and below the Rusk Glacier Basin. Also, the lowest ELA was reconstructed using the Louise method at an altitude of 2858 meters and using the Hofer method at an altitude of 2682 meters at the Jopar heights and below the Agharzi glacial basin. Reconstruction of the highest ELA according to Porter method at the heights of Hezar at an altitude of 3518 meters and the lowest at the heights of Barez with a height of 2953 meters The highest height of the glacial circus floor below the Sirch basin is at the heights of Plovar with a height of 3,703.2 meters and the lowest height of the circus floor below the difference basin is at the height of Jabal Barez with a height of 2912 meters.

Keywords: permanent snow line, Late Quaternary, central Iran, geomorphic evidence.

کلیدواژه‌ها [English]

  • permanent snow line
  • Late Quaternary
  • Central Iran
  • geomorphic evidence