Institute of Hydrometeorology

Determination of the Likely Dates of Complete Melting of Glacial Basins where
There Are no Large Glaciers

One of the important issues of climate change is the determination of the likely dates of complete melting of glacial basins. Calculating the likely date of complete melting of the largest glaciers in each glacial basin makes it possible to determine the estimated date of complete melting of those glacial basins where large glaciers are observed. Methodologically, the melting of glaciers is considered using analytical representations of the retreat of large glaciers. At the same time, the estimated scenario(s) of climate change should be used. The simplest is to consider the so-called Business as Usual (BaU) scenario, when we consider the melting of glaciers in the future without the use of any mitigation measures [27].
For example, let's consider the issue of the complete melting of the North-Eastern Liadesh glacier. To determine the date of complete melting, we calculate the retreat length − Y₁ (for the entire observation time) and add to it the distance − Y₂, which remains for the complete melting of the glacier according to the latest data on the dynamics of the glacier retreat.

Y₁ + Y₂= Y

where is the total length of the glacier from the beginning of observation, i.e. the path of the glacier in case of complete melting. The North Liadeshti glacier length is 4273 m according to the 2022. From 1986 to 2022, the glacier was shortened by 392 m. The sum of these two numbers should be equal to the glacial Liadeshti ordinate in the Liadeshti regression equation (eq.2) and solve the resulting equation

0,1321x²+7.148x -12.027 = 4665

where x denotes time (years). The positive solution of this equation is 163.04 year. This means that if the current rate of retreat continues, the North Liadesh glacier will likely melt in about 163 years. If we add this value to the starting point (1986), we get that the estimated date of complete melting of the North Liadesh glacier is 2149.

The described method can similarly be used to determine the estimated dates of complete melting of the large glaciers we have considered. These dates are given in the table.

Estimated dates of complete melting of the great glaciers of Georgia

Let us use the estimated dates of complete melting of the large glaciers determined in Table 3 and define the likely dates of complete melting of each glacial basin. As a result, we obtain: 1. The estimated date of complete melting for the Abkhazian glacial basin is 2077 year; 2. The likely date for the complete melting of the Enguri River glacial basin is 2149 year; 3. For the Rioni River glacial basin, this date is 2161 year; and 4. For the East Georgian glacial basin, this date is 2153 year.

Determination of the Likely Dates of Complete Melting of Glacial Basins where
There Are no Large Glaciers

Consider the estimated date of complete melting of glacial basins, where there are no large glaciers. Let us define these dates in BaU scenario

In western Georgia, only two, the Bzipi and Kelasuri basins, do not have large glaciers (only one small glacier has survived in the Khobistskali basin). To determine the dynamics of changes in the areas of glacial basins, specific processing of satellite data is required , which includes several stages. First, let's define the research area. Then, let's identify the glacial basins of these two rivers. To determine the area of glaciers, let's process satellite data, namely, determine the reflectivity of the earth's surface, make topographic corrections of the obtained results, and classify the so-called unsupervised data. After classification, it is possible to determine the total area of glaciers in a separate basin and its chronological change.
The dynamics of glacier change in the Bzifi and Kelasuri basins The analysis used data from Landsat 5, 7, and 8 satellites for the time interval from 1986 to 2023. Satellite data for fourteen different dates were available for this period. Table 6 shows the total areas of glaciers determined by the SRS by date.

Total areas of glaciers determined by SRS in the glacial basins of the Bzipi and Kelasuri rivers by dates

The figure shows graphs of changes in the total area of glaciers determined by the SRS in the glacial basins of the Bzipi and Kelasuri rivers.

Total Areas Change Graphs: a − River Bzipi glacial basin and b − River Kelasuri glacial basin defined based on SRS.

Derived equations for glacier retreat have been used to estimate the dates of their complete melting. To determine. In the trend equations, let's set the ordinate equal to zero and determine the solution. We will obtain the estimated time of complete melting for each glacial basin, namely: for the Bzipi glacial basin this time is 58 years, and for the Kelasuri glacial basin it is 82 years. If we add these values to the initial observation date (1986), we will obtain that the estimated date of complete melting of the Bzipi glacial basin is 2044, and for the Kelasuri basin − 2068.

Similarly, let's perform calculations for five more river basins of East Georgia, where there are no large glaciers, and we will obtain the estimated time of complete melting for each of the basins. Let's add the estimated dates of melting of the glacial basins of West Georgia, and Table 7 presents the estimated dates of complete melting of the glacial basins where there are no large glaciers.

Estimated dates of complete melting of glacial basins where there are no large glaciers

The discussion shows that glacial basins where large glaciers are observed will not melt during this century, while those glacial basins where large glaciers are not observed will melt during this century.