**2. Research of small glaciers**

Scientists categorize small sustainable firn and ice features mainly in three types: small cirque

Small cirque glaciers and glacierets occupy small sections of Pleistocene glacial cirques (usually just below tall rock walls) and can be considered as remnants of former cirque glaciers, which existed during the termination phases of the Wuermian ice age. On the Balkan Peninsula, these features occupy areas of 0.5–5 ha and have thicknesses in the order of 10–20 m. Moraine ridges have framed their lower ends. Small cirque glaciers have elongated contour, a longitudinal profile with a concave upper part and convex lower section of a tongue shape. Glacierets have simpler longitudinal cross-section (convex or concave or straight), lack of a pronounced tongue-like end and the width is often greater than length [4–6]. The presence of dynamic

glaciers, glacierets and snow patches [3].

78 Glacier Evolution in a Changing World

**Figure 1.** Mountains in Southeastern Europe with present-day small glaciers.

A wide variety of methods are applied in the research of small glaciers, many of them are specific. The knowledge about these features can be addressed as 'microglaciology', a field of science that bridges between classical glaciology and periglacial geomorphology.

Mass balance studies reveal inter-annual variations of small glaciers. The most accurate would be to measure changes of firn/ice volume. This is hard to do as it requires detailed knowledge about glacier subsurface topography, and laborious measurements after both the accumulation and ablation season. If small glaciers are to be observed mainly as climatic indicators, it is often enough to know relative changes from year to year and in longer terms. In this context, it is easier to measure the surface area of small glaciers or, as alternative (or in addition), to record fluctuations in glacier front or ice level by a measurement on the field or by photographs. It is desirable that these are done at least once a year, in autumn, to summarize the results of the ending mass-balance cycle (balance year).

On the field, glacier area is measured usually with a measuring tape (or rope) and a laser range finder. Measurements are done along glacier contour (in cases of a simpler shape) or on selected lengths and widths (in cases of irregular contours). Satellite image data can also be used if done in the exact time of the year. Distances of glacier fronts from fixed positions are measured in cases of changeable lower ends, again with the use of a tape. Current positions of firn level can be marked with paint on the rock. Measured data are then processed in a laboratory: measured lines are entered in Geographic Information System (GIS) in an appropriate scale, and then, the software calculates the exact areas. When only selected lengths and widths are measured, they are entered in the software in a proper scale. They are used as a frame, on which photographs of the glacier surface, made from distant positions, are then fitted. After that glacier contour from those images is digitized, and the area is calculated.

Spatial overlay of data from multiple measurements allows for precise comparison between glacier states of different years. Repetitive photography is also an important technique to obtain inter-annual changes. Glaciers are photographed each time from same (fixed) positions, and then images are overlayed. Precise data about area and volume cannot be obtained by using this method, but it is highly indicative when tracing the relative changes and trends in the development of small glaciers. Later, if proper scaling is done on the field, accurate absolute values for surface area and level variations can be retrieved from such photographs.

The current state of snow and firn cover is also quite indicative for the mass balance from the past year, especially for the evaluation of accumulation and ablation varieties across glacier surface. It is assessed on the field, with the use of alpine equipment (crampons, ice axe, etc.).

Effects from accumulation season only are studied in spring (April–May) by measuring snow cover thickness and density in glacier vicinities. Such observations have been rare, especially in our region, due to the high avalanche danger and limited accessibility of glacier sites in that time of the year.

Morphology studies involve geomorphological, glaciological and geophysical methods. Morphology analysis aims to reveal how a glacier is formed. It requires a detailed description of glacier surface geometry (contours, tilts, bergschrund, crevasses, caverns) and the character of surrounding landforms (moraines, protalus ramparts, avalanche gullies, screes). Size and roundness and lichen cover of debris are assessed. Weathering of depositional forms can be examined, e.g. with a Schmidt hammer [21, 22]. However, only relative age can be assessed with these methods.

Internal structure of small glaciers is testified with various techniques, which require investments in labour and equipment. The easier way is to excavate pits in glacier body, but this is hard to do and not much informative as pits cannot be deep. It is better to study natural outcrops of glacier body instead (bergschrund or cracks). Drilling with appropriate ice drills allows to reach depths below 10 m and to retrieve unspoiled cores for analysis in a laboratory. Radar sounding makes possible to estimate underground structure (thickness, sediment layers, patches of buried ice) without digging [23]. Both drilling and sounding, however, require carrying out heavy and expensive equipment, and this sets limitations on the application of these techniques, especially in hardly accessible high mountain areas.

Isotope composition of firn and ice along with absolute ages of formation of glaciers and their surrounding landforms (e.g. moraines) can be verified with the use of laboratory techniques after taking samples of rock, ice or organic particles. Such analyses (isotope, radiocarbon, etc.) are costly and have been applied just for two of the small glaciers on the Balkan Peninsula (in Pirin [4–6] and Durmitor [24, 25]). Absolute ages of surrounding moraines have been also retrieved by lichenometry for a glacier in Durmitor mountains [13].
