@2024 Afarand., IRAN

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ISSN: 2538-4384    Geographical Researches 2020;35(4):343-354

Background
Climate change is one of the most outstanding features of the Quaternary era that has transformed the earth's landforms.
Previous Studies
Encountering global warming, the study of the glacial deposits and their remains is of great importance because future climate change trends can be predicted by studying the past climate. Glacial remains are the most important documents for the evaluation of the past and future climate changes [Abramowskia et al., 2006]. The earth's weather and also Iran's weather have undergone various severe changes in Quaternary era [Gafari & Avaji, 2015]. Although climate change is a global phenomenon, its trends and remains are different in various regions [Sharma & Shakia, 2006]. One of the most significant climate heritages of the fourth era in Iran's mountains is the glacial remains [Yamani, 1381].
Aim(s)
This study aimed to determine the domain of the glaciers in the last quaternary era and prepare a pattern of the geomorphologic and climatic situations of the studied region. Moreover, this study tends to compare the climatic differences in the current situation and that of the quaternary era.
Research type
This is an empirical and descriptive survey.
Research society, place and time
The current research is carried out using data and statistics extracted from topography and geology maps as well weather data from 7 stations (2010-2019) in the Shahdad basin.
Sampling method and number
104 glacial cirques were detected in the studied area.
Used devices&materials
Excel, ARC GIS, and GPS are the main devices used in this study.
Findings by Text
Enumeration, determination, abundance and location of the region's cirques and their analysis using Wright and Porter methods: According to the topographic maps, 104 small and large cirques were detected in the studied area that were scattered at an altitude inside 2500 to 3600 m. while they were denser at an altitude inside 2700 to 2900m account for 32% of them. The highest cirque is located at the altitude of 3523m and the lowest one is at the altitude of 2514m (Figure 2 & Table 1). Permanent snow border using Wright method: 104×60=62.4 0.4×100=40 2948-40=2908 According to the Wright method, the permanent snow border in the region is at an altitude of 2980 m. Permanent snow border using Porter method (cirques floor altitude): 2800-17=2783 2900-17=2883 2800+(2783÷5666)×100=2849 According to the Porter method, the permanent snow border is at an altitude of 2849m. According to the mentioned calculations, there is a height difference of 59 m between the altitude calculated using the Wright method and the Porter method. This difference is normal. Permanent snow border using Porter method (altitude ratio method) 3523+2514=6037 6037÷2=3018 Permanent snow border using Porter method (accumulation-area ratio): 2800+2900=5700 5700÷2=2850 All calculated means for the permanent snow border are 2906. Temperature and precipitation in the studied area and speculating them in the past: The statistical information of 7 stations was collected for 10 years so as to draw isotherm and isohyetal maps in past and present. There were just 7 stations that had the needed data from 1st January of 2010 to 31st December 2019 (Table 2). Present isotherm map in the studied area : According to the map, the minimum and maximum recorded temperatures in the basin (inside the basin and in the area of the studied stations) are -2.26˚C and 29.70˚C. The maximum recorded temperature inside the basin is 25˚C which is recorded in the eastern part of the basin, while the minimum temperature is 5˚C recorded in the western part (Figure 3). Present isohyetal map in the studied area: According to the map, the maximum and minimum recorded precipitation in the basin (inside the basin and in the area of the studied stations) are 282.92 and 12.64 mm. Maximum and minimum precipitation inside the basin are 210 mm and 60 mm recorded in the northern-west and eastern parts of the basin, respectively (Figure 4). Past isotherm map (last quaternary era) in the studied area: Past isotherm map was prepared using the past permanent altitude of the snow border of the basin and its adiabatic decline. According to the map, maximum and minimum temperature in the basin (inside the basin and in the area of the studied stations) are 28.06˚C and -35.88˚C. The maximum and minimum temperatures inside the basin are 20˚C and -20˚C recorded in the eastern and northern-west part of the basin, respectively (Table 5). Past isohyetal map (last quaternary) in the studied area According to the map, the maximum and minimum recorded precipitation in the basin (inside the basin and in the area of the studied stations) are 567.13 mm and 26.58 mm. Maximum and minimum precipitation inside the basin are 450 mm and 150 mm recorded in the northern-west and eastern parts of the basin, respectively (Figure 6 & Table 3). Alluvial terraces are the climate heritages. Although terraces are still forming in the rivers and lakes, the old ones are at higher altitudes and more expanded in comparison to the current terrace. There are two important points about the terraces: flow changes in rainy periods and tectonic activities changing the environmental situations [Asghari Moghadam, 2004]. To rebuild Lut lake in thecondition of the immobility of the crust layer, 237 ice tongues were detected on topographic maps (1:50000). In relation to the glacial tongues in the same altitudes, five terraces at the altitudes of 250, 400, 550, 800, and 1000m. The first terrace with the highest altitude (1000m) has the largest volume of the lake and the fifth terrace with an altitude of 250m has the smallest volume of the lake. Shahdad city is between the terrace of 400m and that of 550m (Figure 7).
Main comparison to the similar studies
Analyzing the old climate in the southern west of Turkey, Sarikaya et al. (2008) found out that the precipitation in the last ice age was 1.9 current amount. They (2011) estimated that the altitude of the snow border in Honaz mountains in Turkey in the quaternary era and in the present are 2600 and 3600m. according to Jafarbeygloo et al. (2014) Wurm snow border in Bidkhan mountains of Kerman using cirques floor altitude average is 3166 m, this border is calculated to be 3100-3200 using Wright method and currently, it is at an altitude of 500 m. Khosravi et al. (2016) found more than 39 large and small cirques in their research on geomorphological quaternary glacial evidence in Binalood. Speculating old climate in Alvand, Jafari & Barati found out that temperature was 9.26˚C colder and was 317mm more than present,
Suggestions
There is no suggestion reported.
Limitations
There is no limitation reported.
Conclusions
The use of the glacial geomorphological evidence and balance line altitude is one of the best methods to speculate the old climate in the last era of the glaciers' expansion. To speculate Lut Lake, 327 glacial tongues were detected and five iso-hype terraces were found. The first terrace with the highest altitude (1000m) has the largest volume of the lake and the fifth terrace with an altitude of 250m has the smallest volume of the lake
Acknowledgments
The authors thank the meteorological organization of Kerman for providing all needed data immediately and free.
Conflict of interest
None
Ethical Permissions
None.
Funding Sources
Kerman Shahid Bahonar University granted all needed budget for this study.

TABLES and CHARTS

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