Ocean currents are strongly controlled by seafloor topography. Recent studies have shown that small-scale features with slopes steeper than 0.05° significantly affect subsurface eddy velocities and the vertical structure of ocean circulation patterns. Such slope gradients represent the majority of the present-day oceanic basins. Modeling past oceanographic conditions for key climate stages requires similarly detailed paleo seafloor topography grids, in order to capture ocean currents accurately, especially for ocean models with sufficient resolution (<0.1°) to resolve eddies. However, existing paleobathymetry reconstructions use either a forward modeling approach, resulting in global grids lacking detailed seafloor roughness, or a backward modeling technique based on sediment backstripping, capturing realistic slope gradients, but for a spatially restricted area. Both approaches produce insufficient boundary conditions for high-resolution global paleo models. Here, we compute high-resolution global paleobathymetry grids, with detailed focus on the Southern Ocean, for key Cretaceous and early Cenozoic climate stages. We backstrip sediments from the modern global bathymetry, allowing the preservation of present-day seafloor slope gradients. Sediment isopach data are compiled from existing seismo-stratigraphic interpretations along the Southern Ocean margins, and expanded globally using total sediment thickness information and constant sedimentation rates. We also consider the effect of mantle flow on long-wavelength topography. The resulting grids contain realistic seafloor slope gradients and continental slopes across the continent-ocean transition zones that are similar to present-day observations. Using these detailed paleobathymetry grids for high-resolution global paleo models will help to accurately reconstruct oceanographic conditions of key climate stages and their interaction with the evolving seafloor.

In support of future science missions, an engineering demonstration was conducted to show the ability of the nupiri muka AUV to be deployed and operated at an ice shelf. The AUV was deployed from Davis Station, Antarctica, to conduct underwater surveys in the vicinity of, and beneath, the Sørsdal ice shelf. The AUV conducted several surface transits from the station to the ice shelf, where dive missions at various depths were conducted. The primary mode of operation was the AUV tracking near the seafloor. In addition, a patch survey was conducted near the stations, where several sediment grabs were taken.

We have used a quantitative definition of marine heatwaves to detect all events which have occurred in 12 regions across the continental shelf off eastern Tasmania over 1993-2015. For each event in each region this atlas includes information on (i) event properties including intensity, duration and depth, (ii) maps of regional ocean circulation and ocean temperature during the event, and (iii) maps of regional atmospheric conditions during the event (air temperature and surface wind). Also provided are summary statistics including the typical conditions which give rise to marine heatwaves in each region and annual time series demonstrating interannual variability and long term trends in marine heatwave properties. Provided is a comprehensive document presenting the atlas and a set of CSV files containing the underlying data.

The Whole-Antarctic Ocean Model (WAOM) is based on the Regional Ocean Modelling System (ROMS) with thermodynamic ice shelf interactions following Galton-Fenzi et al. (2012)¹. WAOM simulations of the present-day (year 2007) were used to investigate the physical drivers of Antarctic ice shelf basal melting via an ocean heat budget in a longitudinal framework. Ice shelves buttress the Antarctic Ice Sheet and therefore are critical in the dynamics of ice sheet instability and its contribution to sea level rise. New insights into the seasonal melting mechanisms and its importance at circum-Antarctic scale were investigated in Dias et al (2025)². 1) Galton-Fenzi B, Hunter JR, Coleman R, Marsland SJ, & Warner RC. (2012) Modeling the basal melting and marine ice accretion of the Amery Ice Shelf, Journal of Geophysical Research: Oceans, 117 (C9). https://doi.org/10.1029/2012JC008214 2) Boeira Dias F, England MH, Morrison AK, & Galton-Fenzi B. (2025).: On the seasonal variability of ocean heat transport and ice shelf melt around Antarctica, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2024-3905

Southeastern Australia's marine waters are undergoing a trend of increased warming, surpassing the global average. This area has emerged as an alluring location for research on planktic microfossils, particularly dinoflagellate cysts, which are abundant in contemporary and Late Quaternary sediments. The composition of dinoflagellate cyst assemblages offers valuable information about the physical and biogeochemical properties of mid-latitude waters in this region. This study presents an analysis of cyst assemblages from marine sediment cores from waters inshore and offshore Maria Island, Tasmania, southeast Australia, up to 9 kyrs BP. The dominant cysts were Protoceratium reticulatum, Protoperidinium spp. (P. avellana, P. conicum, P.minutum, P. oblongum, P. subinerme, P. shanghaiense) and Spiniferites spp. (S. bulloideus, S. hyperacanthus, S. membranaceus, S. mirabilis, S. pachydermus, and S. ramosus). Inshore, Spiniferites spp. were more abundant (up to 61%), while P. reticulatum was dominant (up to 80%) at the offshore site. Impagidinium spp. and Nematosphaeropsis labyrinthus were exclusively detected offshore, with their increasing occurrence from 6 kyrs BP to present suggesting a transition from shallow coastal to stable deep-water habitat. Cysts of the Alexandrium tamarense complex were detected over the past 140 years and 9 kyrs BP at the inshore and offshore sites respectively, indicating an endemic long-term presence. Low abundances of Gymnodinium catenatum cysts were detected exclusively inshore from 50 years ago to present, suggesting recent bloom events. The limited southward penetration of the East Australian Current is indicated by the lack of warm-water cyst taxa such as Lingulodinium machaerophorum. Unlike coccolithophores, previously studied in the same sediment core, no discernible shift from cold to warm-water dinoflagellate cyst species was observed. The documentation of dinoflagellate cyst assemblages presented in this study will aid in predicting the effects of climate change, eutrophication, and introduction of novel species on local and broader community dynamics.