The Denman/Scott glacier system is currently one of the fastest retreating glaciers in East Antarctica, however the trigger and mechanisms of this retreat are currently poorly understood.
During the “Denman Marine Voyage” in 2025 and the EASI-3 voyage in 2024, we collected geophysical data to map the seafloor and subseafloor of the region to investigate the regional geological boundary conditions of this glacier system. Together with the results of the “Denman Terrestrial Campaign” and re-evaluation of airborne magnetic data, the Denman/Scott Glacier system emerges to show clear inheritance of the underlying tectonic basement structure modulating its dynamics and current retreat. We identified a chain of tectonic basins, along the flow path of the Denman/Scott glacier, which continue offshore onto the continental shelf. The widely expected deep glacial trough carved by localised erosion by the ice streams is completely absent offshore hinting at very different glacial processes dominating this region.
This new bathymetric dataset sheds light on the crucial role basement structure and tectonics play in glacial dynamics. It provides valuable insights into the erosional patterns of the Denman and Scott glaciers and emphasises the unique vulnerability and triggering mechanisms along the East Antarctic coastline.

The Southern Ocean plays a major role in absorbing anthropogenic carbon dioxide and regulating the Earth’s climate, of which phytoplankton plays a key part through photosynthesis. Southern Ocean phytoplankton growth undergoes strong seasonality driven by light and nutrient conditions, with blooms typically encountered in austral spring and summer. While lower productivity is expected in autumn, recent evidence showed that significant phytoplankton growth can still occur along the Antarctic coast. Here, we present a suite of biological measurements collected within deep phytoplankton features observed near the Denman Glacier (East Antarctica), in autumn. Our results suggest that these biological features, measured down to 300 m, hosted healthy phytoplankton (photochemical efficiency > 0.5), consisting mainly of diatoms that quickly responded to increasing light. These deep phytoplankton were associated with warmer temperatures, high bacterial production (up to 10 nmol/L/d) and lower macronutrient concentrations compared to other regions sampled during the voyage. The presence of this deep feature suggests large carbon export may still occur in this region in autumn. This study provides new insights into subsurface biological processes that are undetectable from space, in a region with little to no biogeochemical profiling float coverage, and during a season rarely targeted by field campaigns.

The ocean processes controlling basal melting of the Denman–Shackleton Ice Shelf system and its connectivity with neighbouring East Antarctic ice shelves remain poorly understood. Denman glacier is the westernmost outlet of the Aurora Subglacial Basin. To the east, Totten Glacier and Moscow University Ice Shelf are part of the same drainage system, and are undergoing rapid changes. Here we explore ocean-mediated feedbacks between Denman and these upstream glaciers using a high-resolution regional ocean–ice shelf model. We compare two model experiments: one including basal melting from all ice shelves and another in which melting of the ice shelves upstream (to the east) of the Denman–Shackleton system is turned off. Our results show that remotely generated meltwater cools surface waters in front of the Denman–Shackleton Ice Shelf, reducing basal melt rates in the upper 100-300 m (the shallow melting mode). Remote meltwater also freshens shelf waters in the Denman region, strengthening the Antarctic Slope Front (ASF) and suppressing cross-shelf intrusions of Circumpolar Deep Water. This reduces basal melting at depth (the deep melting mode), particularly near the grounding line. These findings demonstrate strong along-shelf connectivity between East Antarctic ice shelves and highlight the role of remote meltwater in modulating ice-shelf–ocean interactions. They further suggest that meltwater feedbacks may lead to complex and regionally varying ice-shelf responses to a warming climate.

Phytoplankton play a key role in the biological carbon pump via photosynthesis, a process regulated by light and iron (Fe) availability; both of which exhibit spatial and seasonal variability in the Southern Ocean. To add to this complexity, over 99% of Fe is bound to ligands, which are molecules that retain Fe in the surface ocean. Variation of light and Fe can explain broad seasonal changes in annual primary productivity, but we have limited knowledge of how light availability interacts with ligand-bound Fe to impact phytoplankton productivity, particularly in autumn. To fill this knowledge gap, we incubated East Antarctica coastal phytoplankton communities from deep chlorophyll features observed East of the Denman glacier, and within the Shackleton polynya, to light and Fe bound to different ligands. Contrary to previous studies, phytoplankton were observed to be both Fe and light limited East of the glacier but were only light limited in the Shackleton polynya. However, phytoplankton in the Shackleton polynya became Fe limited after being exposed to a higher light level. Preliminary data suggest that responses of the phytoplankton communities to Fe bound to different ligands did not differ significantly between sites. We hypothesise that the contrasts observed in responses to Fe are due to differences in phytoplankton communities. Understanding what drives phytoplankton productivity seasonally is crucial for understanding the BCP under future climate scenarios.