Lake changes in the permafrost region of the Mongolian Altai Mountain (1970-2021)
DOI:
https://doi.org/10.5564/mjgg.v60i44.2930Keywords:
Lake changes, Mongolian Altai Nuruu, Permafrost, Climate changesAbstract
In this study, we examined changes in the surface area of the lakes in the permafrost region of the Mongolian Altai Mountain range between 1970 and 2021. We aimed to (1) determine the dynamic changes in the surface areas of the lakes, and (2) compare and analyze them using long-term climate data. We used a topo map (1970), Landsat 5 TM, and ETM+ (2000, 2006, 2011, 2015, and 2020-2021) satellite imagery, and delineated the surface areas of the lakes using normalized difference water index (NDWI). The long-term historical data and satellite imagery were used to determine changes in the number and the surface areas of the lakes (>1 ha). We classified the surface areas of the lakes into five categories (1 - 5 ha, 5 - 10 ha, 10 - 50 ha, 50 - 100 ha, and >100 ha) and compared them over the years. During the study period, the number and the total surface areas of the lakes decreased by –24.3% (or 406 to 307) and –18.6% (or 13093 to 10646 ha), respectively. Among the five categories, the number of small lakes with an area of 1-5 ha was significantly decreased. In contrast, we found that 17 lakes with a total area of 70 ha were newly formed during the past 50 years. The air temperature has increased significantly in the permafrost region of the Mongolian Altai Mountain since 1940. Hence, we conclude that the dynamics of the lakes in the region are attributed to the microclimate regimes, permafrost extent, and glaciers.
Монгол Алтайн нурууны цэвдэгтэй бүсийн нууруудын өөрчлөлт (1970-2021)
ХУРААНГУЙ: Энэхүү судалгаагаар бид 1970-2021 оны хооронд Монгол Алтайн нурууны цэвдэгтэй бүсийн нууруудын өөрчлөлтийг судалсан. Бид (1) Монгол Алтайн нурууны цэвдэгтэй бүс нутагт тархсан нууруудын гадаргын усны динамик өөрчлөлтийг тодорхойлох; (2) цаг уурын урт хугацааны мэдээтэй нууруудын өөрчлөлтийг харьцуулан шинжлэхийг зорьсон. Уг судалгаанд байрзүйн зураг (1970), Landsat 5 TM болон ETM+ (2000, 2006, 2011, 2015, 2020-2021) хиймэл дагуулын зургуудыг ашиглаж, нууруудын гадаргын усны талбайн хэмжээг нормчлогдсон усны индекс (NDWI) ашиглан зурсан. Нууруудын тоо болон гадаргын усны талбайн (>1 га) өөрчлөлтийг тодорхойлохын тулд урт хугацааны мэдээ, хиймэл дагуулын мэдээ ашигласан. Бид нуурын гадаргын усны талбайг хэмжээгээр нь тав ангилж (1 - 5 га, 5 - 10 га, 10 - 50 га, 50 - 100 га, >100 га) хугацаагаар нь харьцуулсан. Судалгааны хугацаанд нуурын нийт тоо болон гадаргын усны талбайн хэмжээ –24.3%-иар (406-аас 307),–18.6%-иар (13093 га-10646 га) тус тус буурсан. Дээрх таван ангиллаас 1 - 5 га талбайтай жижиг нууруудын тоо эрс буурсан. Харин эсрэгээрээ сүүлийн 50 жилийн хугацаанд нийт 70 га талбай бүхий 17 нуур шинээр үүссэн. Монгол Алтайн нурууны цэвдэгтэй бүсэд 1940 оноос хойш жилийн дундаж агаарын температур эрс нэмэгдээд байгаа. Эндээс бид бүс нутгийн нууруудын динамик өөрчлөлт нь бичил уур амьсгалын горим, цэвдгийн тархалт, мөстлөгтэй холбоотой гэж дүгнэж байна.
Түлхүүр үгс: Нуурын өөрчлөлт, Монгол Алтайн нуруу, Цэвдэг, Уур амьсгалын өөрчлөлт
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