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Early Pleistocene Marine Isotope Stage (MIS)-31 (1.081 to 1.062 Ma) is a unique interval of extreme global warming, including evidence of a West Antarctic Ice Sheet (WAIS) collapse. Here we present a new 1000-year resolution, spanning 1.110-1.030 Ma, diatom-based reconstruction of primary productivity, relative sea surface temperature changes, sea-ice proximity/open ocean conditions and diatom species absolute abundances during MIS-31, from the Scotia Sea (59° S) using deep-sea sediments collected during International Ocean Discovery Program (IODP) Expedition 382. The lower Jaramillo magnetic reversal (base of C1r.1n, 1.071 Ma) provides a robust and independent time-stratigraphic marker to correlate records from other drill cores in the Antarctic Zone of the Southern Ocean (AZSO). An increase in open ocean species Fragilariopsis kerguelensis in early MIS-31 at 53° S (Ocean Drilling Program Site 1094) correlates with increased obliquity forcing, whereas at 59° S (IODP Site U1537; this study) three progressively increasing, successive peaks in the relative abundance of F. kerguelensis correlate with Southern Hemisphere-phased precession pacing. These observations reveal a complex pattern of ocean temperature change and sustained sea surface temperature increase lasting longer than a precession cycle within the Atlantic sector of the AZSO. Timing of an inferred WAIS collapse is consistent with delayed warmth (possibly driven by sea-ice dynamics) in the southern AZSO, supporting models that indicate WAIS sensitivity to local sub-ice shelf melting. Anthropogenically enhanced impingement of relatively warm water beneath the ice shelves today highlights the importance of understanding dynamic responses of the WAIS during MIS-31, a warmer than Holocene interglacial.

Gas hydrates (GHs) are susceptible to climate-induced perturbations such as changes in sea level and temperature and may provide feedback to such perturbations. The occurrence of GHs in the Pacific margin of the Antarctic Peninsula (PAP) is well known from seismic data, including a Bottom Simulating Reflector (BSR). Such BSR is widespread between Elephant and King George Is in water depths between 1000-3000 m. Previous studies in the area assessed the geothermal gradient from the BSR depth (~31°C/km±3.15 MAD) assuming the GH is in equilibrium. However, nearby heat flow determinations suggest that GHs are not in equilibrium, as the derived geothermal gradient is significantly higher (~97°C/km±36.4 MAD). Thus, the BSR is 100-400 m deeper than the theoretical Base of the GH Stability Zone (BGHSZ) in the area. Overpressure resulting from rapid sedimentation or tectonic stresses cannot explain alone the observed depth of the BSR, as it cannot balance for the thermal conditions at such depths. Vertical movements of tectonic and/or glacial-isostatic origin could be only partially responsible for the mismatch between observed BSR and theoretical BGHSZ depths. Hence, a better knowledge of the thermal regime of the PAP is needed to assess the dynamics of the GH system. A research cruise in 2024 aims to constrain better the dynamics of the GH system of the PAP using geophysical imaging and heat flow measurements. The cruise will also assess the potential export of methane into the ocean using a suite of geochemical indicators in sediments, pore waters and the water column

In the frame of ICEFLAME project (PID2020-114856RB-I00, Spanish Ministry of Science and Innovation), an inventory of BSRs levels in the west Antarctic Peninsula margin has been carried out. The aim of this inventory is to assess the theoretical transient state of these geological structures due to the global ice-sheet retreat in the Polar Regions.In the west Antarctic Peninsula margin, three areas with characteristics BSR levels have been found: (i) north South Shetland Islands (reported in previous studies, (ii) North Bransfield Island (Bransfield Strait, AP margin), and (iii) Anvers Island (AP margin). North of the South Shetland Islands, BSR levels had been reported in between the Elephant–King George islands accretionary wedge sector (Lodolo et al., 1993). Two extensive and discontinuous BSR levels (named BSR-1 and BSR-2) have been mapped in the inventory. The BSR-1 appears as local, disconnected and discontinuous patches, about 10 km diameter in geographical extension, of high amplitude reflections of inverse polarity. Its burial depth ranges from ca. 150-200 ms TWT (at the base of the accretionary wedge) to ca. 300 ms TWT (in the middle slope). BSR-2 shows more extensive spatial continuity than BSR-1. BSR-2 levels are well-defined high amplitude reflections of inverse polarity. They simulate the seafloor increasing the burial-depth with water depth from ca. 250 ms TWT in the upper slope to ca. 1s TWT at the base of the accretionary wedge. North off Bransfield Island, BSR levels had been reported in the distal continental shelf of the Antarctic Peninsula margin (Oliveira, 2017). The BSR in this area constitutes a continuous high amplitude reflection of inverse polarity. It shows a shallow and homogeneous burial depth ranging from 145 to 170 ms TWT. South of Anvers Island, a BSR level had been reported to the west of the island in the middle continental shelf of the Antarctic Peninsula margin (Solovyov et al., 2017). Here, the BSR forms an isolated patch of ca.

International Ocean Discovery Program (IODP) Expedition 382 in the Scotia Sea’s Iceberg Alley recovered among the most continuous and highest resolution stratigraphic records in the Southern Ocean near Antarctica spanning the last 3.3 Myr. Sites drilled in Dove Basin (U1536/U1537) have well‐resolved magnetostratigraphy and a strong imprint of orbital forcing in their lithostratigraphy. All magnetic reversals of the last 3.3 Myr are identified, providing a robust age model independent of orbital tuning. During the Pleistocene, alternation of terrigenous versus diatomaceous facies shows power in the eccentricity and obliquity frequencies comparable to the amplitude modulation of benthic δ18O records. This suggests that variations in Dove Basin lithostratigraphy during the Pleistocene reflect a similar history as globally integrated ice volume at these frequencies. However, power in the precession frequencies over the entire ∼3.3 Myr record does not match the amplitude modulation of benthic δ18O records, suggesting Dove Basin contains a unique record at these frequencies. Comparing the position of magnetic reversals relative to local facies changes in Dove Basin and the same magnetic reversals relative to benthic δ18O at North Atlantic IODP Site U1308, we demonstrate Dove Basin facies change at different times than benthic δ18O during intervals between ∼3 and 1 Ma. These differences are consistent with precession phase shifts and suggest climate signals with a Southern Hemisphere summer insolation phase were recorded around Antarctica. If Dove Basin lithology reflects local Antarctic ice volume changes, these signals could represent ice sheet precession‐paced variations not captured in benthic δ18O during the 41‐kyr world.

Oscillations in ice sheet extent during early and middle Miocene are intermittently preserved in the sedimentary record from the Antarctic continental shelf, with widespread erosion occurring during major ice sheet advances, and open marine deposition during times of ice sheet retreat. Data from seismic reflection surveys and drill sites from Deep Sea Drilling Project Leg 28 and International Ocean Discovery Program Expedition 374, located across the present-day middle continental shelf of the central Ross Sea (Antarctica), indicate the presence of expanded early to middle Miocene sedimentary sections. These include the Miocene climate optimum (MCO ca. 17−14.6 Ma) and the middle Miocene climate transition (MMCT ca. 14.6−13.9 Ma). Here, we correlate drill core records, wireline logs and reflection seismic data to elucidate the depositional architecture of the continental shelf and reconstruct the evolution and variability of dynamic ice sheets in the Ross Sea during the Miocene. Drill-site data are used to constrain seismic isopach maps that document the evolution of different ice sheets and ice caps which influenced sedimentary processes in the Ross Sea through the early to middle Miocene. In the early Miocene, periods of localized advance of the ice margin are revealed by the formation of thick sediment wedges prograding into the basins. At this time, morainal bank complexes are distinguished along the basin margins suggesting sediment supply derived from marine-terminating glaciers. During the MCO, biosiliceous-bearing sediments are regionally mapped within the depocenters of the major sedimentary basin across the Ross Sea, indicative of widespread open marine deposition with reduced glacimarine influence. At the MMCT, a distinct erosive surface is interpreted as representing large-scale marine-based ice sheet advance over most of the Ross Sea paleo-continental shelf. The regional mapping of the seismic stratigraphic architecture and its correlation to drilling da

Highlights • Core-log-seismic correlation allows to assign ages to the Scotia Sea seismic record. • Major implications are derived on the relation between regional and global events. • The main stratigraphic events are much younger than previously proposed. • Three major phases for the regional oceanography are observed from late Miocene. • These phases appear to be closely linked to the Antarctic Ice Sheet dynamics. Scotia Sea and the Drake Passage is key towards understanding the development of modern oceanic circulation patterns and their implications for ice sheet growth and decay. The sedimentary record of the southern Scotia Sea basins documents the regional tectonic, oceanographic and climatic evolution since the Eocene. However, a lack of accurate age estimations has prevented the calibration of the reconstructed history. The upper sedimentary record of the Scotia Sea was scientifically drilled for the first time in 2019 during International Ocean Discovery Program (IODP) Expedition 382, recovering sediments down to ∼643 and 676 m below sea floor in the Dove and Pirie basins respectively. Here, we report newly acquired high resolution physical properties data and the first accurate age constraints for the seismic sequences of the upper sedimentary record of the Scotia Sea to the late Miocene. The drilled record contains four basin-wide reflectors – Reflector-c, -b, -a and -a' previously estimated to be ∼12.6 Ma, ∼6.4 Ma, ∼3.8 Ma and ∼2.6 Ma, respectively. By extrapolating our new Scotia Sea age model to previous morpho-structural and seismic-stratigraphic analyses of the wider region we found, however, that the four discontinuities drilled are much younger than previously thought. Reflector-c actually formed before 8.4 Ma, Reflector-b at ∼4.5/3.7 Ma, Reflector-a at ∼1.7 Ma, and Reflector-a' at ∼0.4 Ma. Our updated age model of these discontinuities has major implications for their correlation with regional tectonic, oceanographic and cryospheric events. Acco

Multibeam bathymetric imagery and acoustic sub-bottom profiles are used to reveal distribution patterns of sub-surface sedimentation in Dove Basin (Scotia Sea). The goals of the study are to determine the imprint of the inflow of deep Antarctic water masses from the Weddell Sea into the Scotia Sea, to establish the factors driving the styles of contourite deposition and to discern the relative contribution of alongslope versus downslope processes to the construction of the uppermost late Quaternary sedimentary record in the basin. The most significant morpho-sedimentary features in Dove Basin are linked to contouritic processes and to mass movements. Plastered drifts on the flanks of the basin constitute the most common contouritic deposits. Basement-controlled drifts on top of structural elevations are common along the central ridge, the central basin plain and scattered along the basin flanks. Sheeted drifts occur on top of adjacent banks or are restricted to the deep basin. In contrast, mounded drifts are poorly represented in Dove basin. A laterally extensive contouritic channel runs along the central ridge. Contouritic channels are also identified in the upper parts of the lateral banks and slopes. Numerous slide scars along the upper parts of the slopes evolve downslope into semitransparent lens-shaped bodies, with occasional development of across-slope channels. Semitransparent lenses occur intercalated within stratified deposits in the slopes of the basin, in the central ridge and in the deepest basin plain. The spatial arrangement of contouritic morphologies points to the influence of the water column structure and the basin physiography. In the eastern sub-basin, two different fractions (lower and upper) of Weddell Sea Deep Water (WSDW) leave an imprint on contourite deposits owing to the sloping interface between the two fractions. Contouritic influence is more subdued in the western sub-basin, and limited to the imprint of the lower WSDW. The upper parts

En este proyecto se presenta un modelo computacional, en un Sistema de Información Geográfica (SIG), para el mapeo de la distribución en 3D en la que los hidratos de gas del fondo marino serían estables. La construcción del modelo se compone de dos pasos principales:(i) la construcción de modelos digitales del terreno para las tres variables que controlan el campo de los hidratos en el medio marino (temperatura del fondo marino, gradiente geotérmico y batimetría/presión) a partir de los datos 3D disponibles en bases de datos públicas y de acceso libre y (ii) el cálculo de la potencia de la zona de estabilidad de los hidratos mediante las funciones de equilibrio de gas para los hidratos de gas biogénicos. La solución se basa en una función trascendental, que ese resuelve de forma iterativa en un entorno SIG. El modelo se ha aplicado en los márgenes continentales europeos y representa la distribución de la base de la zona de estabilidad de los hidratos de gas para composiciones de gas biogénicas = This project shows a computational model implemented in a Geographic Information System (GIS) environment, for the 3D mapping of the gas hydrate stability field in the subseafloor. The construction of the model consists of two main steps: (i) the development of digital terrain models for the three oceanographic variables that control the gas hydrate stability field (seafloor temperature, geothermal gradient and bathymetry/pressure) from 3D information avaible in public and free databases; and (ii) the calculation of the thickness of the hydrate stability zone using the gas balance functions for biogenic gas hydrates. The solution is based on a transcendental function, which is solved iteratively in a GIS environment. The model has been applied to the European continental margins and represents the base distribution of the gas hydrate stability zone for biogenic gas compositions.

Dove Basin, a small oceanic domain located within the southern Scotia Sea, evidences a complex tectonic evolution linked to the development of the Scotia Arc. The basin also straddles the junction between the main Southern Ocean water masses: the Antarctic Circumpolar Current (ACC), the Southeast Pacific Deep Water (SPDW) and the Weddell Sea Deep Water (WSDW). Analysis of multichannel seismic reflection profiles, together with swath bathymetry data, reveals the main structure and sediment distribution of the basin, allowing a reconstruction of the tectonostratigraphic evolution of the basin and assessment of the main bottom water flows that influenced its depositional development. Sediment dispersed in the basin was largely influenced by gravity‐driven transport from adjacent continental margins, later modified by deep bottom currents. Sediments derived from melting icebergs and extensive ice sheets also contributed to a fraction of the basin deposits. We identify four stages in the basin evolution which – based on regional age assumptions – took place during the early Miocene, middle Miocene, late Miocene–early Pliocene and late Pliocene–Quaternary. The onsets of the ACC flow in Dove Basin during the early Miocene, the WSDW flow during the middle Miocene, and the SPDW during the late Miocene were influenced by tectonic events that facilitated the opening of new oceanic gateways in the region. The analysis of Dove Basin reveals that tectonics is a primary factor influencing its sedimentary stacking patterns, the structural development of new oceanic gateways permitting the inception of deep‐water flows that have since controlled the sedimentary processes.

Dove Basin, a small oceanic domain located within the southern Scotia Sea, evidences a complex tectonic evolution linked to the development of the Scotia Arc. The basin also straddles the junction between the main Southern Ocean water masses: the Antarctic Circumpolar Current (ACC), the Southeast Pacific Deep Water (SPDW) and the Weddell Sea Deep Water (WSDW). Analysis of multichannel seismic reflection profiles, together with swath bathymetry data, reveals the main structure and sediment distribution of the basin, allowing a reconstruction of the tectonostratigraphic evolution of the basin and assessment of the main bottom water flows that influenced its depositional development. Sediment dispersed in the basin was largely influenced by gravity‐driven transport from adjacent continental margins, later modified by deep bottom currents. Sediments derived from melting icebergs and extensive ice sheets also contributed to a fraction of the basin deposits. We identify four stages in the basin evolution which – based on regional age assumptions – took place during the early Miocene, middle Miocene, late Miocene–early Pliocene and late Pliocene–Quaternary. The onsets of the ACC flow in Dove Basin during the early Miocene, the WSDW flow during the middle Miocene, and the SPDW during the late Miocene were influenced by tectonic events that facilitated the opening of new oceanic gateways in the region. The analysis of Dove Basin reveals that tectonics is a primary factor influencing its sedimentary stacking patterns, the structural development of new oceanic gateways permitting the inception of deep‐water flows that have since controlled the sedimentary processes.