Holocene water mass structure changes in Lake Nurume, Lützow-Holm Bay, East Antarctica

Abstract Paleoenvironmental reconstructions using sediments from isolation basins including lakes are useful approaches to obtain evidence of sea-level and ice-sheet changes in Antarctica. However, a detailed study using multiple sediment cores of how isolation basins respond to external forcings is needed to improve the accuracy of paleoenvironmental reconstructions. We reconstructed how the water mass structure of Lake Nurume, located in Langhovde, Lützow-Holm Bay, East Antarctica, changed in response to sea-level and ice-sheet changes during the Holocene using sediments from different water depths and nearby trenches. Sedimentary observations, diatom analyses, and X-ray fluorescence core scanner analyses were conducted to reconstruct the three-dimensional characterization of water mass structure combined with the paleotopographic reconstruction using glacial isostatic adjustment modelling. Sedimentation resumed at approximately 6.6 cal kyr BP when the lake became ice-free and marine conditions, as evidenced by the presence of marine diatoms and shell fossils. At approximately 2.0 cal kyr BP, laminated structures appeared in sediment cores, accompanied by a decrease in benthic diatoms. This transition is interpreted as a response to ice-sheet readvance, whereby the ice margin approached the lake, increasing freshwater input and reducing vertical mixing. The resulting stratification caused anoxic conditions in the bottom water. Finally, at approximately 0.5 cal kyr BP, the lake became completely isolated from the sea, establishing its current water mass structure. These findings contribute to more accurate paleoenvironmental reconstructions such as sea-level and ice-sheet changes using sediments from isolation basins in Antarctica.