Could Lake Joyce have acted as a long-lived proglacial refugium in Antarctica’s McMurdo Dry Valleys?

Lake Joyce of the McMurdo Dry Valleys (MDV), Antarctica, contains an endemic copepod population (Diacyclops joycei) that has not been identified from apparently suitable habitats in nearby lakes. The absence of a known source for colonization has led to speculation that Lake Joyce may have acted as a refugium during periods when MDV climate was sufficiently arid that freshwater lakes were largely extirpated. However, Lake Joyce is canonically viewed as a young MDV lake due to its low salt content, challenging its refuge status. In this contribution, we present a new lake bathymetric model, water δ18O and δ2H values, and chloride budget to reassess lake history. Results are consistent with previous estimates of lake age but indicate that the full water column is in contact with Taylor Glacier. We propose that, due to its topographic setting, Lake Joyce migrates with the waxing and waning of Taylor Glacier through glacial cycles, episodically losing salts, leading to an erroneously young age estimate and providing a mechanism to maintain fresh conditions during Holocene climate changes. These mechanisms may have facilitated the maintenance of copepod populations through changes in regional hydrology that rendered other lakes inhospitable due to elevated salinity.