Physiography and basal melt rate of subglacial Lake 90°E

Lake 90°E in Antarctica encompasses an area of 2,000 km², ranking it the second largest subglacial lake identified in the country by area, following Vostok Subglacial Lake (VSL). In this study, the overlying ice thickness and lake elevation of Lake 90°E determined using airborne radio-echo sounding across two survey lines conducted by the International Collaborative Exploration of the Cryosphere by Airborne Profiling in Princess Elizabeth Land (ICECAP/PEL) campaign during the 32nd Chinese National Antarctic Research Expedition (CHINARE 32, 2015/16), and depth of lake water was inversed by coupling with synchronous airborne gravity data. The analysis reveals a 15 m elevation increase in the ice sheet surface from the southeast to the northwest, correlating with a gradient in ice thickness that progresses from thin in the southeast to thick in the northwest. The maximum water depth of Lake 90°E is estimated as 320 m along the central line, bifurcated by a topographic ridge into two zones of varying depths, with exceptionally shallow water at its periphery. Thermodynamic modeling using data from two points along the survey lines indicates that melt rates at the ice-water interface have been consistently low over the last 400,000 years, varying between 0.56 to 0.95 mm/yr and 2.70 to 3.41 mm/yr, balanced by either basal freezing to the south or downstream water loss, thereby maintaining a thermodynamically stable state. Satellite imagery and altimetry data analyses did not identify any significant changes in the ice surface’s outline or elevation over the past 20 years. This study presents novel insights into the physiography and thermodynamic state of Lake 90°E, establishing a foundation for future drilling initiatives.