GPR survey for safety logistics operations of Russian Antarctic expedition Sukhanova A.A.*, Saint-Petersburg State University; Popov S.V., Polar Marine Geological Survey Expedition, Saint-Petersburg State University; Kashkevich M.P., Saint-Petersburg State University. Summary Mirny station The discussion of the results of the fieldwork GPR Further, the results of experimental studies have become the investigations near Russian Antarctic stations and bases basis for a glaciological and geophysical investigation in the during 60-65th (2014-20) Russian Antarctic Expeditions Mirny station area during the 60–62nd RAE (2014-17). The (RAE) is described in this paper. This scientific research is aim of the GPR research was to find out a safe place of the dedicated to glacier crevasses detection in the areas of snow glacier to organize a new airfield for the landing of medium- runways and logistic traverse routes. GPR investigations range aircraft with ski landing gears (Fig. 1, а). The complex involve additional methods, such as multi-offset soundings of methods also included multi-offset sounding method (Fig. and ice core drilling, that has become the basis for safety 1, b) and ice core drilling in order to determine the velocity reason of logistics operations of RAE. model. In addition, a measuring polygon was set up to observe the dynamics of the glacier in this area. Besides, the Introduction area without dangerous cracks was defined according to the results of geophysical and glaciological researches. Thus, When transport operations are carried out in areas of Russian the main criteria of snow-runway were established and could Antarctic stations and field bases, safety has always had an be introduced as following: the direction of the central important role in the organization of snow runways and runway axis, the relief gradient and the glacier surface scientific and logistic traverse routes in the areas of high condition. In frames of this, an inspection list was firstly velocity glaciers. Due to their dynamic features they are formed, which is necessary for the organization of an airfield characterized by a formation of crevasses, which can cause on a glacier. As a result, the BT-67 “Turbobasler” aircraft accidents at stations (Popov et al., 2016). Сrevasses are often has successfully landed (Fig. 1, c) already at the beginning covered by snow and can not be detected on the glacier of 2017 (Popov et al., 2016; Popov et al., 2017; Popov et al., surface. Thus, the crucial task is to ensure safety and to have 2019). Also, the classification of crevasses according to a possibility to identity crevasses in the near-surface part of safety for transport operation was formed based on these glacier distantly. Such geophysical method as GPR manages studies. these tasks effectively, that was also confirmed by different researches abroad (Arcone, Delaney, 2000; Eder et al., DOI:10.1190/gpr2020-026.1 2008). This paper provides a short review of Russian GPR investigations in Antarctica in order to search for dangerous crevasses in glaciers. Experimental investigations The first experimental and methodological work for crevasse detection was done during the 60th RAE (2014/15) field season near the Progress and Mirny stations. The work included studies on a model object, as well as penetrating the crevasses at various frequencies in order to organize a correct study of the reflected signal (Popov and Polyakov, 2016). As a result, it was identified, that diffraction waves Figure 1: а) Performance of GPR radar «OKO-2» that were formed by crevasse could be used for the velocity investigation at the frequency of 400 MHz; b) Performance model creation, while other investigations such as ice core of the multi-offset sounding; c) Landing of the BT-67 drilling (Cumming, 1952; Tiuri, 1984; Kovacs et al., 1995) «Turbobasler» aircraft near Mirny station. or multi-off set sounding (Vladov and Starovoitov, 2004; Macheret, 2006; Glazovsky and Macheret, 2014) are Moreover, since the 62nd RAE field season (2016/17) impossible to realize. Besides, the analysis of the obtained additional works are carried out in order to identify zones of data confirms that specialities and сontrast of crevasse the blue ice as they are convenient for landing aircraft with configuration are improving with increasing frequency. This wheeled gear. The main method for this purpose is GPR leads data processing to have more correct interpretation. survey that is focused to determine the boundary between the Downloaded 11/16/20 to 178.71.137.38. Redistribution subject SEG license or copyright; see Terms of Use at https://library.seg.org/page/policies/terms 18th International Conference on Ground Penetrating Radar Golden, Colorado, 14–19 June 2020 © 2020 Society of Exploration Geophysicists 10.1190/gpr2020-026.1 Page 97 blue ice and the snow-firn, as well as to identify dangerous research was implemented near Progress station in the 63rd crevasses. Based on the results of geophysical studies of the RAE (2017/18) field season. It was able to organize a new 64th RAE (2018/19), the blue ice zone boundaries were all-season track since the old road was destroyed by a huge determined. On the GPR time-section (Fig. 2, a) a change in depression in the glacier (Popov et. al, 2017). A new section signal contrast (red-yellow line) indicates the end of the blue for the organization of the all-season route was the area ice zone and the formation of snow cover with the around the dip. This meant that it was necessary to carry out characteristic layering 1. However, the blue ice zone did not GPR remote sensing of the glacier to find any cavities or meet the criteria of organizing there a runway for aircraft on cracks that could lead to the same collapse. a wheeled gear because of its limited size. Besides, three types of crevasses 2 were identified in the study area The complex of glaciological and geophysical surveys (Fig. 2, a). additionally included GPR works and ice core drilling. Using ice core is not only the best way to form the kinematic model for the near-surface area but also to get important information about the structure of the ice sheet. As a result, the permittivity was calculated (Fig. 3, a) based on the correlation between the permittivity and ice density. Besides, the calculation of the velocity of electromagnetic wave propagation was performed by using hodographs of diffracted waves (Fig. 3, b). Then a scheme of the glacier permittivity within the uppermost (1st meter) part of the glacier was made. All velocity computations let us formed the detailed kinematic model of the near-surface area. It was found that the area around the depression is safe, since the width of the identified crevasses did not exceed 0.6 m. The results of the work were reported to the station management, and then the new route was marked and small cracks were filled with snow (Fig. 3, c). After all, transport operations were realized precisely along this route. Oasis Bunger field base During the austral summer field season of the 64th RAE (2018/19) GPR survey carried out in the Oasis Banger DOI:10.1190/gpr2020-026.1 Russian field base, where the landing site was supposed to Figure 2: a) GPR time-section across the blue ice zone: be on the sea ice of the epishelf gulf. In this case, the 1 - the blue ice area; 2 – the snow-firn area; 3 – crevasses; importance of the studies was focused not only on the b) Crevasses of the type «CR1»; c) Crevasses of the type identification of crevasses of the ice sheet integrity, but also «CR2»; d) Crevasses of the type «CR3». on the ice thickness estimation. The results of the GPR research showed that the ice thickness all over the work area The first type «CR1» is widespread in the blue ice zone and is about 3 m. Reflection from the ice-water boundary is is presented on GPR sections by separate diffractions one observed in all the GPR time-sections as well as the multiple under the other (Fig. 2, b). The «CR2» and «CR3» types waves (Fig. 4, а). Concerning crevasses, they were identified correspond to the snow-firn area (Fig. 2, c, d). These mostly in the outer parts of the working area, but also crevasses are quite broad, but their main characteristic is melting areas were detected on the ice surface. The reason depth. Due to this difference, crevasses of the «CR2» type of their formation is the removal of weathering products of were marked as dangerous ones. The latest is mostly located rocks composing the hills by the prevailing winds (Fig. 4, b). in the central part of the investigated area, therefore, this Under the influence of solar radiation, the processes of sector can be not considered appropriative for the airfield thawing of such particles increased that led to the formation establishing. More detailed research in this area is needed of cavities. Their dimensions do not meet the requirements based on the list of recommendations as a result of studies. for runway coatings, therefore, area of their distribution is unsafe. Based on the obtained data, three zones were defined Progress station (Fig. 4, b): 1) «Green zone» for landing of small aircrafts with ski gears, 2) «Blue zone» for medium aircrafts with ski There were successful geophysical and glacial surveys by gears and 3) «Red zone», where aircraft landing without GPR that ensured the safety of transport operations. That preliminary rolling is prohibited (Sukhanova et al, 2019). Downloaded 11/16/20 to 178.71.137.38. Redistribution subject SEG license or copyright; see Terms of Use at https://library.seg.org/page/policies/terms 18th International Conference on Ground Penetrating Radar Golden, Colorado, 14–19 June 2020 © 2020 Society of Exploration Geophysicists 10.1190/gpr2020-026.1 Page 98 Figure 3: а) Permittivity of the ice core; b) Hodographs of diffracted waves and calculated permittivity; c) The view after the work is done.