CC BY
0УДК 528.8, 551.34
APPLICATION OF GIS ANALYSIS TO IMPROVE THE INFORMATIVITY OF
PERMAFROST MAPS
SHESTAKOVA ALENA ALEKSEEVNA Senior researcher of GIS and cryolithozone mapping laboratories, Melnikov Permafrost Institute of Siberian Branch of the Russian Academy of Sciences, Yakutsk, Russia
Abstract. For digital GIS mapping of pe rmafrost, it is proposed to conduct a spatial analysis of the landscape conditions controlling the permafrost parameter and include its results in the form of charts and relationship tables in the map legend. In this paper, the 1:5,000-scale geocryological map of the proposed bridge site on the Lena River near Yakutsk is used as an example illustrating what new information can be extracted when reading the map. The map legend displays the spatial distribution patterns of permafrost parameter values.
Keywords: permafrost, spatial analysis, GIS maps, ground temperature, active layer thickness, geocryological map.
The rapid development of northern natural resources and growing evidence of climate change requires an understanding of the spatial and temporal variability of permafrost conditions. Interest in permafrost-related problems is expanding across a wide range of disciplines (landscape research, ecology, soil science, etc.). Analysis of special geocryological (permafrost) maps is becoming of primary importance. The recent advances in GIS mapping provide great opportunities for a comprehensive analysis of the permafrost as a component of the geographical environment. Traditionally, permafrost map legends provide a list of values for a given parameter (temperature, thickness, ice content, etc.). Its relationship with another permafrost characteristics, such as permafrost distribution, is not displayed on the map and is reflected in the legend as a matrix table. Examples include the Circum-Arctic Map of Permafrost and Ground Ice [3], the Geocryological Map of the USSR [2], various typological maps, zoning maps, etc. In this approach, the geographical distribution patterns of permafrost parameters (ground temperature, permafrost thickness, ice content, active layer thickness), which are often of great importance as an indicator of permafrost phenomena, is lost. Aggregate permafrost maps provide a separate view of each permafrost element [2], and the map users themselves must identify their interrelationships.
When compiling digital permafrost GIS maps, we suggest that a spatial analysis of permafrost-landscape conditions controlling the mapped parameter is made and its results are presented in the map legend as charts and relation tables. Tables aid further interpretation of the map content, analysis of the distribution patterns of a given permafrost characteristics, identification of relationships, and, therefore, provide new knowledge and help identify errors in the map content. Charts reflect the structure of the map area in accordance with the traditional form of the legend and show the quantitative ratio of the areas with a particular value of the mapped parameter.
The proposed method for increasing the map informativity by presenting the generalized GIS analysis data as a chart in the legend was partially used for a preliminary 1:5,000-scale geocryological map of the Lena River bridge crossing site near Yakutsk.
Permafrost in the Republic of Sakha (Yakutia) is relatively well studied. Its characteristics, such as temperature, active layer thickness and related surficial processes, affect the state of the permafrost environment. Knowledge of the permafrost conditions is important for sustainable socio-economic development and for assessing environmental change under current climate change and increasing human impacts.
Ground temperature is the most important characteristics controlling not only the current state of landscapes, but also their dynamics. Changes in ground temperature can trigger the development of cryogenic processes, disturbing the stability of landscapes. For example, an increase in ground temperature by 1 °C over the last three decades in treeless landscapes in Central Yakutia has resulted
in thawing of the upper parts of ice wedges, causing extensive thermokarst development [4]. The older landscape maps presented ground temperature indirectly in a tabular form, while the more recent maps mainly show it as isotherms, which is quite inconvenient for spatial analysis. The use of GIS allows account for landscape differentiation to better represent the spatial distribution of ground temperature. This is especially important for the areas of discontinuous and sporadic permafrost.
The 1:5,000-scale geocryological map of the Lena River bridge site shows 16 ranges of ground temperature displayed on the map by color background within the landscape units. The colors for displaying the ground temperature ranges were chosen in such a way as to highlight the landscape units with the lowest and highest temperatures. The traditional form of the legend is shown in Fig. 1.
Ус поеные обозначения
Температура пород. С Криогенные процессы
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or -1.0 до -0.3 —» Морсэобоиное растресшмч)«
от -1.0 до -0 5 А Г>уче»чж
| or -1.5 до -0 5 Согмфло«иия
1 or-1 5 до-10
| or-2.0 до-1.0 э Тегам
| от -2 0 до-15 Термокарст
| от -2 5 до-15 $ Термопросад««
| от -3.0 до -2.0 /
| от -3 5 до -2 5 TepuoipojH*
| or -4 0 до -2.0 t) Эолоем * р>слова»е процесс»
| от -4 0 до -2 5 ■ Полосе отвода «есшпа т »оста
| or -4.0 до -3.0 - Геофтичеса* профил*
| от -5 0 до -4 0
Towoa : да «ww* СТС
| or -60ДО-40
нет :эеде->'1' • С*еекммь> с да—»«« температурь грумтое
| Гидрограф««
Fig. 1. Legend of the 1:5,000-scale geocryological map of the Lena River bridge crossing
area near Yakutsk.
It should be noted that the spatial differentiation of ground temperature is quite diverse. After some analysis of several thematic layers of the map, the temperature data were grouped into 4 classes and a chart of the areal coverage of ground temperature classes was additionally compiled (Fig. 2). The chart shows that the landscape units with warm (-1 to -2 °C) permafrost are dominant (19.4% of the map area), followed by the landscapes with moderate (-2 to -3 °C) permafrost (16.5%), cold (below -3 °C) permafrost (14.6%) and transitional (0.5 to -1 °C) permafrost (13.9%). No ground temperature are available for about 36% of the map area.
The active layer consists of seasonally thawed and seasonally frozen layers and its thickness is one of the most variable characteristics of permafrost. The values of the active layer thickness are inextricably linked with the study of landscape dynamics in the permafrost area. An increase or decrease in its parameters can lead to major changes in the landscape structure. Moisture storage, ecosystem productivity, activation of cryogenic processes and other landscape characteristics primarily depend on changes in the active layer thickness. Yakutia is included in the CALM program, a global monitoring system for assessing changes in the active layer thickness [5]. The data obtained by researchers from the Melnikov Permafrost Institute indicate that the active layer thickness in forest
landscapes of Central Yakutia remains fairly stable and has not increased since the 1980s [1]. It should be noted that this is most likely due to an increase in forest biomass.
Fig. 2. Chart of the areal coverage of ground temperature classes.
For representation of seasonal thawing and freezing depths on the geocryological map of the bridge crossing, points with corresponding active layer data were used. Based on the analysis of the active layer thickness data using the GIS attribute table, 15 units were distinguished clustered into 5 groups. The chart of the areal distribution by active layer thickness classes, compiled in addition to the map legend, makes it possible to identify the predominant area intervals characteristic of the territory under consideration. The most common landscapes are those with the active layer thickness of more than 2 m, occupying 43.5% of the map area. Landscapes with active layer thicknesses of 0.51.0 m, 1.0-1.5 m and 1.5-2.0 m occupy 1.2%, 12.5% and 6.6% of the map area, respectively. A small part of the area, 0.5%, is occupied by landscapes with the active layer thickness of less than 1 m. The area with no data on active layer thickness comprises 19% (Fig. 3).
Fig. 3. Chart of the areal coverage of active layer thickness classes.
The presented results of the quantitative analysis of spatial distribution patterns of permafrost parameter values should be used in the future when designing a bridge crossing over the Lena River
near Yakutsk. Further progress in GIS technologies entails the compilation of maps of more complex content aimed at a highly qualified consumer. In this regard, the author's attempts to show the transition to a new type of legends that reveal the interrelations of the components of the natural environment, increasing the information content of the maps compiled, are very relevant. Perhaps this transition complicates the traditional form of the legend, but at the same time significantly simplifies the reading of the map and facilitates its analysis.
1. Varlamov, S.P., Skryabin P.N., Skachkov Yu.B. Ground temperature monitoring of soils in the Tuymaada valley / S. P. Varlamov, P. N. Skryabin, Yu. B. Skachkov // Scientific Support for Solving Key Problems of the Development of Yakutsk. - Yakutsk: Sfera Publishing House LLC. - 2010. -P. 97-102.
2. Geocryological map of the USSR. Scale 1:2,500,000 / Ed. E.D. Ershov. Vinnitsa, Kart. enterprise, 1997.
3. Circum-arctic map of permafrost and ground ice conditions, scale 1:10 000 000 / Ed. By J. Brown, O.J. Ferrians, Jr., J.A. Heginbottom, E.S. Melnikov. Reston, Virginia, Interior-geol. survey, 1997.
4. Fedorov A.N., Ivanova R.N., Park H., Hiyama T., Iijima Y. Recent air temperature changes in the permafrost landscapes of northeastern Eurasia // Polar Science. - 2014. - Vol. 8. - Issue 2. - P. 114128. D0I://DX.D0I.0RG/10.1016/J.P0LAR.2014.02.001.
5. Nelson F.E., Shiklomanov N.I., Christiansen H.H., Hinkel K.M. The circumpolar active layer monitoring (CALM) Workshop: Introduction // Permafrost and Periglacial Processes. - 2004. - Vol. 15. - Issue 2. - P. 99-101. DOI: 10.1002/ppp.488.
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