[U-11] Climate change during the Quaternary and Anthropocene

[U11-P01] Investigation of water-mass mixing near the Denman Glacier using dissolved inorganic radiocarbon

*Yaojia Sun¹, Laura Herraiz-Borreguero^2,3, Stewart Fallon⁴, Michael Ellwood^4,5, Yosuke Miyairi¹, Yusuke Yokoyama¹ (1.Atmosphere and Ocean Research Institute, University of Tokyo, 2.Australian Antarctic Program Partnership (AAPP), University of Tasmania, Hobart, TAS, Australia, 3.Commonwealth Scientific and Industrial Research Organization Environment, Hobart, TAS, Australia, 4.Research School of Earth Sciences, Australian National University, Canberra, Australia, 5.Australian Centre for Excellence in Antarctic Science (ACEAS), Australian National University, Canberra, ACT, Australia)

Keywords:

dissolved inorganic radiocarbon,Denman Glacier,Antarctica,water mixing

Ocean warming has emerged as a key driver of ice-sheet change during the Anthropocene, posing an increasing threat to Antarctic ice shelves. While most attention has focused on rapid mass loss in West Antarctica, East Antarctica contains approximately five times more ice and includes ice shelves that are increasingly exposed to relatively warm ocean waters, with potentially large implications for future sea level rise. Among these, the Denman Glacier is one of the fastest retreating glacier systems in East Antarctica and alone holds ice equivalent to ~1.5 m of global sea level rise. Recent float observations show that warm modified Circumpolar Deep Water (mCDW) has already reached the cavity beneath the Denman Glacier, driving basal melt at depth. While it is known that mCDW is found on the continental shelf, the residence time of mCDW on the continental shelf and extent of its mixing with shelf and ice-shelf-modified waters remain poorly constrained. Radiocarbon (¹⁴C) of dissolved inorganic carbon (DIC) provides a tracer of water mass age and mixing, allowing for distinction between recently ventilated surface waters and older deep-water contributions. In this study, we will measure ¹⁴C-DIC in depth profiles from Denman Glacier region to constrain water-mass mixing and deep-water influence near the ice shelf. This work aims to improve understanding of how ocean warming influences ice-ocean interaction in East Antarctica ice shelves and to evaluate the potential of ¹⁴C-DIC as an early-warning indicator of increased warm deep-water influence on vulnerable ice shelves.