Over the past 34 Million years, the Antarctic continental shelf has gradually deepened due to ice sheet loading, thermal subsidence, and erosion from repeated glaciations. The deepening that is recorded in the sedimentary deposits around the Antarctic margin indicates that after the mid-Miocene Climate Optimum (≈15 Ma), Antarctic Ice Sheet (AIS) dynamical response to climate conditions changed. We explore end-members for maximum AIS extent, based on ice-sheet simulations of a late-Pleistocene and a mid-Miocene glaciation. Fundamental dynamical differences emerge as a consequence of atmospheric forcing, eustatic sea level and continental shelf evolution. We show that the AIS contributed to the amplification of its own sensitivity to ocean forcing by gradually expanding and eroding the continental shelf, that probably changed its tipping points through time. The lack of past topographic and bathymetric reconstructions implies that so far, we still have an incomplete understanding of AIS fast response to past warm climate conditions, which is crucial to constrain its future evolution.

The Southern Ocean surrounding Antarctica is a region that is key to a range of climatic and oceanographic processes with worldwide effects, and is characterised by high biological productivity and biodiversity. Since 2013, the International Bathymetric Chart of the Southern Ocean (IBCSO) has represented the most comprehensive compilation of bathymetry for the Southern Ocean south of 60°S. Recently, the IBCSO Project has combined its efforts with the Nippon Foundation – GEBCO Seabed 2030 Project supporting the goal of mapping the world’s oceans by 2030. New datasets initiated a second version of IBCSO (IBCSO v2). This version extends to 50°S (covering approximately 2.4 times the area of seafloor of the previous version) including the gateways of the Antarctic Circumpolar Current and the Antarctic circumpolar frontal systems. Due to increased (multibeam) data coverage, IBCSO v2 significantly improves the overall representation of the Southern Ocean seafloor and resolves many submarine landforms in more detail. This makes IBCSO v2 the most authoritative seafloor map of the area south of 50°S.

The Terror Rift, which is located in the southwestern sector of the Ross Sea (Antarctica), is a narrow and deep basin that extends for 350 km, between Ross Island and Cape Washington, within the broader Victoria Land Basin (VLB; Figure 1). The Terror Rift is ∼75 km-wide and includes the 25-35 km-wide faulted Discovery Graben; it is flanked on the eastern side by the 25-40 km-wide volcanically intruded Lee Arch (Cooper et al., 1987a). Southward continuation of the Terror Rift for an additional 300 km beneath the Ross Ice Shelf is suggested by airborne gravity and magnetic data (Tankersley et al., 2018). Inversion of the gravity data reveals a deep, narrow sedimentary basin, with a left stepover (jog to the east looking south) near Ross Island (Jordan et al., 2020; Tinto et al., 2019). The Terror Rift is one of the youngest parts of the West Antarctic Rift System (WARS), which is a Mesozoic-Cenozoic continental rift system that extends along a strike for 3,200 km from the Weddell Sea to the Ross Sea. The WARS extensional area includes the crustal block assemblage of West Antarctica and the rift shoulder on the border of the East Antarctic craton. During the Late Cretaceous and Paleogene WARS phases within the Ross Sea, part of the Ross Embayment, the E-W stretching of continental crust resulted in several hundred kilometers of extension (e.g., D. S. Wilson & Luyendyk, 2009). The subsidence related to this crustal thinning produced four main broad N-S basins (e.g., Victoria Land Basin, connected to Northern

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