Repeat Subglacial Lake Drainage and Filling Beneath Thwaites Glacier

Active subglacial lakes have been identified throughout Antarctica, offering a window into subglacial environments and their impact on ice sheet mass balance. Here we use high-resolution altimetry measurements from 2010 to 2019 to show that a lake system under the Thwaites Glacier undertook a large episode of activity in 2017, only four years after the system underwent a substantial drainage event. Our observations suggest significant modifications of the drainage system between the two events, with 2017 experiencing greater upstream discharge, faster lake-to-lake connectivity, and the transfer of water within a closed system. Measured rates of lake recharge during the inter-drainage period are 137% larger than modeled estimates, suggesting processes that drive subglacial meltwater production, such as geothermal heat flux or basal friction, are currently underestimated. Plain Language Summary Antarctic subglacial lakes can play an important role in ice sheet dynamics. When subglacial lakes drain, they release large amounts of water that interact with the subglacial drainage system. Here we show lakes draining only four years after a previous drainage event. Our results suggest that lake activity increases the efficiency of the subglacial drainage network. Rates of lake recharge indicate that basal melt-water production is significantly higher than previously thought. Key Points There is evidence of drainage and filling of sub-glacial lakes under Thwaites Glacier in 2017, four years after previous activity There is contrasting lake behavior, drainage volume, discharge, and timing of drainage onset between the 2013 and 2017 events Observations of recharge rates suggest that modeled melt water production is underestimated