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The Southern Ocean is a key player in the climate, ocean, and atmospheric system. As the only direct connection between all three major oceans since the opening of the Southern Ocean gateways, the development of the Southern Ocean and its relationship with the Antarctic cryosphere has influenced the climate of the entire planet. Although the depths of the ocean floor have been recognized as an important factor in climate and paleoclimate models, appropriate paleobathymetric models including a detailed analysis of the sediment cover are not available. Here we utilize more than 40 years of seismic reflection data acquisition along the margins of Antarctica and its conjugate margins, along with multiple drilling campaigns by the International Ocean Discovery Program (IODP) and its predecessor programs. We combine and update the seismic stratigraphy across the regions of the Southern Ocean and calculate ocean‐wide paleobathymetry grids via a backstripping method. We present a suite of high‐resolution paleobathymetric grids from the Eocene‐Oligocene Boundary to modern times. The grids reveal the development of the Southern Ocean from isolated basins to an interconnected ocean affected by the onset and vigor of an Antarctic Circumpolar Current, as well as the glacial sedimentation and erosion of the Antarctic continent. The ocean‐wide comparison through time exposes patterns of ice sheet development such as switching of glacial outlets and the change from wet‐based to dry‐based ice sheets. Ocean currents and bottom‐water production interact with the sedimentation along the continental shelf and slope and profit from the opening of the ocean gateways. Plain Language Summary: The Southern Ocean is the only ocean which connects all three major world's oceans and therefore plays a vital role in our planet's oceanographic and atmospheric systems. We reconstruct the changing depth and geometry of the Southern Ocean seafloor since the establishment of a major ice sheet in Antarctica (34 Ma). We also provide an inventory of ice‐sheet eroded sediments deposited in the Southern Ocean, which has previously been highly underestimated. This ocean‐wide study shows the development of the Southern Ocean from individual, separated basins into the home of the strong Circumpolar current system, by the deepening of the land bridges between Antarctica and Australia and Antarctica and South America. The sediments deposited in the Southern Ocean, especially along the Antarctic margin, illustrate the growth and retreat of the Antarctic ice sheets showing two distinct pulses of enhanced sedimentation at the first continental‐scale glaciation of Antarctica (34 Ma) and after the warm phase of the Miocene Climatic Optimum. On a local and regional scale, we trace the amount of erosion provided by glacier systems along the Antarctic coast. The presented suite of seafloor grids will be made available to the geoscientific community and is an important additional input parameter for paleo‐models. Key Points: Suite of paleobathymetric grids encompassing key time intervals in Southern Ocean development since the Eocene/Oligocene BoundaryDetailed sediment isopachs reveal two distinct sedimentation surges in relation to the advancement of the Antarctic Ice SheetsReconstruction of the Southern Ocean gateways point to the potential of deep‐water exchange in the middle Oligocene [ABSTRACT FROM AUTHOR]

Abstract The thermal state of polar continental crust plays a crucial role for understanding the stability and thickness of large ice sheets, the visco-elastic response of the solid Earth due to unloading when large ice caps melt and, in turn, the accuracy of future sea-level rise prediction. Various studies demonstrate the need for precise measurements and estimation of geothermal heat flow (GHF) in Antarctica for better constrained boundary conditions to enhance the ice sheet model performance. This study provides ground-truth for regional indirect GHF estimates in the Amundsen Sea Embayment, which is part of the West Antarctic Rift System, by presenting in situ temperature measurements in continental shelf sediments. Our results show regionally elevated and heterogeneous GHF (mean of 65 mW m−2) in the Amundsen Sea Embayment. Considering thermal blanketing effects, induced by inflow of warmer water and sedimentary processes, the estimated GHF ranges between 65 mW m−2 and 95 mW m−2. Highlights • In-situ temperature gradient measurements show regional variability. • Temperature variations at the sea floor are induced by circum-polar deep water. • Skin depth correction implemented for Antarctic GHF studies. [ABSTRACT FROM AUTHOR]

New seismic reflection profiles have been interpreted to shed more light on the Neogene deposition in Bounty Trough, an aborted rift characterizing the eastern New Zealand continental margin. Two major processes influencing the deposition were identified. Magmatic activity led to the formation of basement highs, which deform the sedimentary sequences up to early and middle Miocene. The origin of the magmatism unfortunately cannot be solved with the new data presented here. It is difficult to say whether the magmatic activity is an on-going process. Drape structures in the youngest sedimentary unit argue against this. The Oligocene--Miocene represents a period of major change. Bottom current activity then took over as the most important depositional process. Strong cooling events in the late Miocene resulted in modification in the oceanographic regime east of New Zealand. This led to the formation of channels, sediment drifts, and sediment waves. At least since the Miocene, bottom current activity has been the dominating depositional process. [ABSTRACT FROM AUTHOR]