Seasonal and interannual variations in the landfast ice mass balance between 2009 and 2018 in Prydz Bay, East Antarctica

Abstract. Landfast ice (LFI) plays an important role in the climate and ecosystem of the Antarctic coastal regions. We investigate the LFI snow and ice mass balance in Prydz Bay using data collected by 11 sea ice mass balance buoys (IMBs). The observations were distributed offshore from the Chinese Zhongshan Station (ZS) and Australian Davis Station (DS), and covered 2009–2010, 2013–2016 and 2018 ice seasons. The observed LFI annual maximum ice thickness and snow depth were 1.59±0.17 and 0.11–0.76 m off ZS and 1.64±0.08 and 0.11–0.38 m off DS, respectively. Early in the ice growth season, the LFI basal growth rate near DS (0.6±0.2 cm d−1) exceeds that around ZS (0.5±0.2 cm d−1). This is attributed to cooler air temperature and lower oceanic heat flux at that time in the DS region. Snow ice contributes up to 27 % of the LFI total ice thickness at the offshore site close to ground icebergs off ZS because of the substantial snow accumulation. Larger interannual and local spatial variabilities for the seasonality of LFI mass balance identified at ZS than at DS are due to local differences in topography and katabatic wind regime. Air temperature anomalies are more important in regulating the LFI growth rate in the early ice growth season because of thinner sea ice relative to later seasons due to the weak thermal inertia of thin ice. Offshore from ZS, the year-round supercooled water from the nearby Dålk Glacier reduces the oceanic heat flux, promoting the LFI growth at the associated sites throughout the entire ice growth season. During late austral spring and summer, we found the increased oceanic heat flux leading to a reduction of LFI growth at all investigated sites. At interannual timescale, we found that variability of LFI properties across the study domain prevailed, over any trend during the recent decades. We argue that an increased understanding of local atmospheric and oceanic conditions, as well as surface morphology and coastal bathymetry, are required to improve the Antarctic LFI modelling at local and regional scale.