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Xuelong Navigation in Fast Ice Near the Zhongshan Station, Antarctica

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Xuelong Navigation in Fast Ice Near the Zhongshan Station, Antarctica PAPER Xuelong Navigation in Fast Ice Near the Zhongshan Station, Antarctica AUTHORS ABSTRACT Xianwei Wang Navigation in polar sea regions requires special attention to the sea ice condition State Key Laboratory of Remote because it is a major barrier for an icebreaker to break the drift ice or fast ice, allowing Sensing Science and College the vessel to keep moving forward. The advancement of remote sensing imagery pro- of Global Change and Earth vides an effective means to classify and identify various features, including different System Science, Beijing types of sea ice. Hence, it permits fuel and time saving for the entire voyage, especially Normal University, and when drift ice or fast ice becomes a barrier for the icebreaker. In this study, we exploit The Ohio State University the potential usage of high-resolution synthetic aperture radar (SAR) imageries from Xiao Cheng Radarsat-2 to identify sea ice conditions for precise navigation of China’s icebreaker Fengming Hui vessel (Xuelong) during the 29th Chinese Antarctic Research Expedition in December State Key Laboratory of Remote 2012. Different features on the fast ice were identified from horizontal-transmit and Sensing Science and College horizontal-receive polarized imagery. The potential usage of SAR imagery for precise of Global Change and Earth navigation was confirmed by an expert witness on the Xuelong vessel at that time. System Science, Beijing The final voyage route has validated our analysis of fast ice and navigation of the Normal University Xuelong vessel. The predicted regions for unloading locations were also found to be matching well with the actual vessel unloading locations after the final voyage route. Cheng Cheng Keywords: CHINARE, fast ice, navigation, Radarsat-2, Xuelong vessel College of Global Change and Earth System Science, Beijing Normal University ing basic supplies to existing base sta- Navigation Challenge in H.S. Fok tions and some exploration tasks. the Prydz Bay School of Geodesy and Presently, three existing base stations The presence of sea ice in the Prydz Geomatics, Wuhan University in Antarctica are operated by China: Bay represents a great challenge to Yan Liu the Greatwall Station (62°12′59″S, Xuelong navigation between November State Key Laboratory of Remote 58°57′52″W, established in February and December every year. When the Sensing Science and College 1985), the Zhongshan Station temperature drops, ocean water could of Global Change and Earth (69°22′24″S, 76°22′40″E, established freeze below the freezing point and System Science, Beijing in February 1989), and the Kunlun form sea ice. Sea ice would be flat Normal University Station (80°25′01″S, 77°06′58″E, and homogeneous when the gradual established in January 2009) (Chen, thickening process does not collide 1997; Wang et al., 2013). The most with surrounding ice, rafting, or ridg- Background current mission, the 29th CHINARE, ing (Leppäranta, 2011). Otherwise, Introduction to Chinese Antarctic started a voyage from Guangzhou, sea ice with a rough surface or hetero- Research Expedition China, to Antarctica on November geneous character would occur. he Chinese Antarctic Research 5, 2012. The vessel, called Xuelong, Both drift ice and fast ice are en- TExpedition (CHINARE) team was es- was installed as an ice breaker, which countered when the Xuelong vessel tablished in 1984 (Chen, 2008). Its carried many researchers and equip- has to cross the Prydz Bay before ap- primary objectives were to conduct ment and supplies to the Zhongshan proaching the Zhongshan Station. various scientific research activities Station and the Kunlun Station. This Drift ice is the floating sea ice in the and to provide fundamental support voyage was accomplished on April 9, ocean primarily driven by wind and/or for research, which includes transport- 2013. ocean currents (Armstrong et al., 1966). 84 Marine Technology Society Journal Contrary to drift ice, fast ice is the ice Microwave Scanning Radiometer- routing for the navigation and selec- anchored to a landmass that remains EOS, Envisat, and Radarsat (Arkett tion of supply unloading locations for stationary in place (Leppäranta, 2011). et al., 2008; Cavalieri et al., 2006; China’s Xuelong vessel in the fast ice In this bay, the annual maximum ice Kern et al., 2007; Lythe et al., 1999; region in Antarctic seas. thickness was about 1.74 m, and its Ochilov & Clausi, 2012; Ramsay, In order to obtain the fast ice con- ice growth period was greater than 1998; Scheuchl et al., 2001; Spreen ditions around the Xuelong vessel, the 277 days (Lei et al., 2010). This type et al., 2008), have been used to identify necessary data identified for use were of ice is the major barrier for the sea ice and subsequently used to pro- at 15:59, November 29, 2012, data Xuelong vessel to keep moving forward duce sea ice concentration maps. from Radarsat-2 C band SAR Geo- during the voyage, because the ice- These sea ice extent and concentration referenced Fine resolution data with breaker can only break up the fast ice maps are publicly available for scientific fine mode, dual polarization, and spa- at a thickness of about 1.2 m (Chen, or civil usage at http://www.natice. tial resolution of about 8 m. The data 1997; Chircop, 2011). In addition to noaa.gov/ims/, http://arctic.atmos. were ordered on November 27, 2012, icebreaking, containers with different uiuc.edu/cryosphere/, and http://www. 2 days before the Xuelong approaching supplies (e.g., food, fuel, equipment, iup.uni-bremen.de/seaice/amsr/. this region. etc.) have to be unloaded on the fast In fact, the spatial coverage vari- To derive effective information ice first and then transferred to the ation and fast ice movement in polar from the imagery, three processing Zhongshan Station by snowmobile regions are of great concern to the steps have to be done, which include or helicopter. The fuel being supplied scientific community (Giles et al., (1) image geocoding, (2) image inter- is also required to fill the fuel tanks 2008, 2011; Hirose & Vachon, 1998; pretation, and (3) thematic mapping. at the Zhongshan Station through Ushio, 2006; Yackel & Barber, 2007). pipelines. Mahoney et al. (2004, 2007a, 2007b) Image Geocoding Thus, finding an optimal path for carried out research on the extent To geocode the imagery, Next the Xuelong vessel during the voyage and movement of fast ice in Alaska. European Space Agency SAR Toolbox to the Zhongshan Station is critical A method for retrieving the fast ice 4C-1.1 was used. Universal Transverse to safe and swift navigation across the extent with high spatio-temporal res- Mercator (UTM) 43(S) was selected fast ice zone, in addition to searching olution data was introduced, and as the projected coordinate system. Be- for a proper place for unloading dif- fast ice maps in the East Antarctica cause horizontal-transmit and vertical- ferent supplies. This paper aims to were generated by Fraser et al. (2010, receive (HV) data may not be useful describe synergetic usage of different 2012) with MODIS data. Fast ice for classification of new, young, and data sets (Radarsat-2, Landsat) that evolution over the Resolute Channel, smooth first-year sea ice (Abreu et al., could help find the optimal path be- Northwest Territories, Canada, was 2003), the geocoded imagery with fore navigation in fast ice zones, which observed by 1-day interferograms with horizontal-transmit and horizontal- has rarely been reported in the recent European remote sensing tandem receive (HH) polarization was selected literature. data from which cracks could be as the primary data source owing to its identified clearly (Hirose & Vachon, better performance on crack identifi- 1998). Additionally, a system for cation than the HV data. Remote Sensing Data icebreaker navigation in the Baltic Usage and Methodology Sea was developed by Berglund et al. Image Interpretation Sea ice properties and its spatial (2007). All the above-described An ice jam shows a light color with coverage in polar regions have been works are of utmost importance for a high digital number (DN) value (“A” studied for the past two decades. expedition planning. in Figure 1) but a wrinkled pattern in Both optical and microwave remotely Because of the limitation of optical the HH polarized imagery. The im- sensed data, for example, advanced sensors, data are unavailable when clouds agery feature is shown in Figure 2(a). very-high-resolution radiometer, are present. In this paper, we present We speculated that the ice jam was Landsat, Moderate Resolution Im- our results using the high-resolution formed by refrozen pack ice, which aging Spectroradiometer Onboard synthetic aperture radar (SAR) imagery was caused by the collision of neigh- Terra and Auqa (MODIS), Advanced and an associated method for scientific boring fast ice by strong wind and January/February 2014 Volume 48 Number 1 85 FIGURE 1 fectively. Additionally, the tide cracks always stretch for several miles in fast Radarsat-2 imagery used for Xuelong navigation during the 29th CHINARE. At the time of data acquisition, the Xuelong vessel did not appear in this imagery. The locations of the Xuelong vessel ice. from November 29, 2012 to December 2, 2012 were identified using GPS (green dots). Tide cracks Smooth fast ice shows homogenous were indicated with yellow polylines. The boundary of smooth fast ice was indicated with green dark color in the imagery with low DN polyline. The ice jam (ridged ice) was indicated with green rectangle “A.” Tide cracks were indicated values because of the specular reflec- by light blue rectangle marked with “B.” Smooth and flat fast ice was indicated by green rectangle tion of radar wave [“C” in Figure 1 marked with “C.” The rugged fast ice was indicated by dark blue rectangle marked with “D.” and Figure 2(c)].
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