RESEARCH/REVIEW ARTICLE Re-assessment of recent (2008 2013) surface mass balance over Dome Argus, Antarctica Á Minghu Ding,1,2 Cunde Xiao,1,2 Yuande Yang,3 Yetang Wang,4 Chuanjin Li,2 Naiming Yuan,1 Guitao Shi,5 Weijun Sun4 & Jing Ming2 1 Institute of Climate System, Chinese Academy of Meteorological Sciences, Beijing 100081, China 2 State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China 3 Chinese Antarctic Center of Surveying and Mapping, Wuhan University, 129 Luoyu Road, Wuhan 430079, China 4 College of Population, Resources and Environment, Shandong Normal University, Jinan 250014, China 5 Polar Research Institute of China, Shanghai 200136, China Keywords Abstract Snow accumulation; Kunlun Station; CHINARE; digital elevation model; deep ice At Dome Argus, East Antarctica, the surface mass balance (SMB) from 2008 core sites; East Antarctic Ice Sheet. to 2013 was evaluated using 49 stakes installed across a 3030 km area. Spatial analysis showed that at least 12 and 20 stakes are needed to obtain reliable Correspondence estimates of SMB at local scales (a few hundred square metres) and regional Cunde Xiao, Institute of Climate System, scales (tens of square kilometres), respectively. The estimated annual mean Chinese Academy of Meteorological SMB was 22.995.9 kg m2 yr1, including a net loss by sublimation of 2.229 Sciences, Beijing 100081, China. E-mail: 0.02 kg m2 yr1 and a mass gain by deposition of 1.3790.01 kg m2 yr1. [email protected] Therefore, ca. 14.3% of precipitation was modified after deposition, which should be considered when interpreting snow or ice core records produced by future drilling projects. The surface snow density and SMB in the western portion of Dome Argus are higher than in other areas, and these differences are likely related to the katabatic wind, which is strengthened by topography in this sector. A new digital elevation model (DEM) of Dome Argus was generated, confirming that both peaks of the dome can be considered as the summit of the East Antarctic Ice Sheet. Findings from this study should be valuable for validating SMB estimates obtained from regional climate models and DEMs established using remote-sensing data. To access the supplementary material for this article, please see the supplementary file under Article Tools, online. As the highest region of the EAIS, Dome Argus is one of contributed important information to the selection of the the most important candidate sites from which to acquire best site for ice core drilling and for the construction of the oldest East Antarctic ice core (Fig. 1). Previous studies Kunlun Station, which is located between the two highest have shown that on-going deep ice core drilling may points of Dome Argus (Fig. 1a). provide a unique paleoclimate record extending to 1.2 SMB, snow accumulation rate and surface ice velocity Mya (e.g., Xiao et al. 2008). In preparation for the project, are key parameters for glaciological and meteorological the surface topography was investigated, and an AWS studies. To estimate the SMB, snow pit and stake array was deployed by the 21st CHINARE in the austral summer measurements were collected on the northern peak of the of 2004/05 (Zhang et al. 2007; Cheng et al. 2009; Ma Dome Argus area. The b activity horizon in the snow pit et al. 2010). Ice sheet thickness and bed topography were revealed an SMB value of 23 kg m2 yr1 during the surveyed with ground-based ice-penetrating radar by the period 1966Á2005 (Hou et al. 2007). During the period 24th CHINARE in 2007/08 (Bo et al. 2009). These efforts 2005Á08, stake array measurements indicated an SMB of Polar Research 2016. # 2016 M. Ding et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 1 International License (http://creativecommons.org/licenses/by-nc/4.0/), permitting all non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Citation: Polar Research 2016, 35, 26133, http://dx.doi.org/10.3402/polar.v35.26133 (page number not for citation purpose) Surface mass balance over Dome Argus, Antarctica M. Ding et al. Argus, as well as new estimates of SMB and surface Abbreviations in this article AWS: automatic weather station sublimation rates for the period of January 2008 to CHINARE: Chinese National Antarctic Research January 2013. Expedition CV: coefficient of variation DA: 100100 m stake array on Dome Argus Field observations DEM: digital elevation model DZ: 3030 km stake array around Dome Argus In January 2008, during the 24th CHINARE, 49 bamboo EAIS: East Antarctic Ice Sheet poles were installed to measure the SMB across a 3030 ECMWF: European Centre for Medium-Range Weather km square area (Fig. 1b). The distance between the stakes Forecasts was ca. 5 km. In January 2011, the 27th CHINARE GPS: Global Positioning System re-measured the heights of these stakes and examined JRA-55: Japan Meteorological Agency 55-year re-analysis the snow layers at sites with damaged stakes. In January LE: latent heat flux 2013, a second re-measurement campaign was con- MERRA: Modern-Era Retrospective Analysis for ducted. Hence, snow height change observations have Research and Applications been collected for two periods: 2008Á2011 and 2011Á13. NCEP: National Centers for Environmental Prediction The surface density to a depth of 0.20 m was calculated P-E: precipitation minus evaporation/sublimation RTK: real-time kinematic analysis using a tube sampler. To reduce local spatial noise, at least SHC: surface height change two measurements at each site were collected with SMB: surface mass balance an interval of about 4 m. If the difference between the two measurements exceeded 5%, another sample, 19 kg m2 yr1 (Ding et al. 2011). During the austral located so as to form an equilateral triangle with the first summer of 2004/05, a 109.91 m ice core was drilled two measurement sites, was collected. Because of the low to study the preliminary climatic information of Dome A; snowfall rate and weak winds around Dome Argus, the however, the dating results differed greatly between two densification process is negligible on a time scale of five research groups. One team suggested a 2840-year history years (Ding et al. 2015). Therefore, the use of the surface for the top 104.42 m, whereas the other group suggested density to translate snow height changes into SMB does a 41159150-year history for the entire core (Jiang et al. not reduce the reliability of the results. The calculated 2012; Li et al. 2012). Additionally, many studies have SMB uncertainty should be within 2% if visual error of shown that single site measurements may have low local stake height measurement is also considered. representativeness (e.g., Frezzotti et al. 2007; Kameda GPS coordinates of the SMB measurement sites were et al. 2008). also recorded and used to construct a DEM and a surface Better knowledge of the SMB distribution over Dome velocity map for Dome Argus. The GPS data were gathered Argus is needed to support future glaciological studies in using RTK and differential GPS analysis. In January 2013, this region. In this study, we present a new DEM of Dome two Leica AS10 GPS receivers were used to produce the Fig. 1 (a) Location of Dome Argus, East Antarctica. The locations of Dome Fuji, Dome B, Vostok, Dome C and South Pole are also shown. (b) Sketch map of sites for GPS and stake measurements. The base map was generated using QGIS 2.6 (http://www.qgis.com/). Contour line intervals are 500 m. 2 Citation: Polar Research 2016, 35, 26133, http://dx.doi.org/10.3402/polar.v35.26133 (page number not for citation purpose) M. Ding et al. Surface mass balance over Dome Argus, Antarctica DEM of Dome Argus. One GPS receiver was used as a optimal number that minimizes spatial noise at local and reference station at Kunlun Station and made continuous regional scales. measurements from 8 to 14 January 2013 at 5 s intervals. To determine this optimal number, the Monte Carlo The other receiver was used as a roving station to collect method (Metropolis & Ulam 1949) was used to generate data near the stakes. For the roving station, the GPS different combinations of stake numbers. Then, the CV, receiver operated in RTK mode and collected data for also known as relative standard deviation, of each combi- two minutes under good communication conditions. nation was calculated using the following equation: Otherwise, at least 25 min were required to collect data 2sPffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiÂÃ3 r z in differential GPS mode. The collected data were post- 6 j Aj À A 7 ri;r ¼ 6 7 (1) processed, and the horizontal and vertical errors were 6 r 7 i estimated to be 1.2 and 3.9 cm, respectively. The DEM uncertainty is estimated to be B0.03 m and B0.10 m in n25 for DA or n49 for DZ; 25r5n1; j1, ..., r; r the horizontal and vertical respectively. and i1, ..., Cn. The Dome Argus stake array, which included a 55 Here, s represents the CV, and {Aj}, in which j1,..., matrix over a 100100 m area, was also measured to r, is a combinationP when r is the number of degrees of record snow accumulation during the fieldwork (Fig. 1). freedom and A ¼ Aj =r. The mean CV is then calculated These observations were used to determine the SMB and using this equation: P assess the reliability of local-scale single-stake measure- Cr n r ments. Here, DA designates the smaller scale of the two r ¼ i¼1 i;r (2) r arrays (100100 m), that is the Dome Argus stake array, Cn whereas DZ represents the larger scale array (3030 To illustrate the relative error on the estimated degree of km), comprising 49 stakes installed across a wider area spatial coherence, we also calculated the CV of si,r for around Dome Argus.