ALBERT

Description: The West Antarctic Ice Sheet (WAIS) and Antarctic Peninsula Ice Sheet (APIS) have exhibited significant changes over recent decades but there is still great uncertainty about how rapidly and how far they will retreat in a warmer climate. For example, it remains unclear whether or not the marine-based WAIS “collapsed” during the last interglacial period, resulting in a global sea-level rise contribution of more than 3 m. Previous studies, including Ocean Drilling Program (ODP) Leg 178, have shown that sediment drifts on the continental rise west of the Antarctic Peninsula contain a rich high-resolution archive of Antarctic margin paleoceanography and APIS history that extends back to at least the Late Miocene. The potential of existing ODP cores from the drifts is, however, compromised by the fact that composite sections are incomplete and lack of precise chronological control. A new drilling proposal (732-Full2) has been scientifically approved and is with the JOIDES Resolution Facilities Board of the International Ocean Discovery Program for scheduling. The main aims of the proposal are to obtain continuous, high-resolution records from sites on sediment drifts off both the Antarctic Peninsula and West Antarctica (southern Bellingshausen Sea) and to achieve good chronological control on them using a range of techniques. We present preliminary results from a recent site survey investigation cruise on RRS James Clark Ross (JR298) that obtained high-resolution multichannel seismic reflection data over the proposed sites and adjacent working areas. The new data provide a basis for interpretation of (i) sedimentary processes that operated during the development of the drifts, and (ii) links between depositional systems on the continental rise, paleo-ice-sheet dynamics and paleoceanographic processes. Through further analyses of seismic and other geophysical data, in combination with marine sediment cores retrieved from the proposed sites, we aim to provide insight into polar margin sediment delivery, Antarctic ice-sheet history and stability, and Antarctic margin paleoceanography. Subsequently, the proposed drilling campaign will allow a detailed chronology to be established on extended records that will provide a basis for high-resolution interpretations extending back through the Pliocene.

Description: The West Antarctic Ice Sheet (WAIS) and Antarctic Peninsula Ice Sheet (APIS) have exhibited significant changes over recent decades but there is still great uncertainty about how rapidly and how far they will retreat in a warmer climate. For example, it remains unclear whether or not the marine-based WAIS “collapsed” during the last interglacial period, resulting in a global sea-level rise contribution of more than 3 m. Previous studies, including Ocean Drilling Program (ODP) Leg 178, have shown that sediment drifts on the continental rise west of the Antarctic Peninsula contain a rich high-resolution archive of Southern Ocean palaeoceanography and APIS history that extends back to at least the Late Miocene. The potential of existing ODP cores from the drifts is, however, compromised by incomplete composite sections and lack of precise chronological control. A proposal for future drilling on the drifts (732-Full2) has been scientifically approved and is with the JOIDES Resolution Facilities Board for scheduling. The main aims of the proposal are to obtain continuous, high-resolution records from sites on sediment drifts off both the Antarctic Peninsula and West Antarctica (southern Bellingshausen Sea) and to achieve good chronological control on them using a range of techniques. We present preliminary results from a recent site survey investigation cruise on RRS James Clark Ross (JR298) that obtained high-resolution multichannel seismic reflection data, piston cores and box cores to bolster this proposal. The new data and cores provide opportunities to improve understanding of the depositional setting, ensure that there is a comprehensive site survey data package to allay any concerns that the Environmental Protection and Safety Panel may raise, and allow testing of some of the hypotheses underpinning the proposal. The new seismic data provide a basis for interpretation of (i) sedimentary processes that operated during the development of the drifts, and (ii) links between depositional systems on the continental rise, palaeo-ice-sheet dynamics and palaeoceanographic processes. Through further analyses of the seismic and other geophysical data, in combination with the marine sediment cores, we aim to provide insight into polar margin sediment delivery, Antarctic ice-sheet history and stability, and Southern Ocean palaeoceanography. Subsequently, the proposed drilling campaign will allow a detailed chronology to be established on extended records that will provide a basis for high-resolution interpretations extending back through the Pliocene.

Description: Observations across both the West Antarctic and Antarctic Peninsula ice sheets over recent decades have confirmed that the region is warming and undergoing major and potentially rapid changes as a result. These changes have manifest in the form of significant ice-sheet thinning and retreat, and in dramatic short-lived events such as ice-shelf collapses. The longer-term backdrop to this recent change is vital information for our understanding of future ice and climate evolution, and for wider knowledge of ice-sheet function and sensitivity. Providing context on geological timescales, such records can be obtained from two main sources: (1) from ice cores extracted from the ice sheet interiors and (2) from continuous marine sedimentary sequences recovered from the sea floor surrounding the Antarctic continent. Whilst ice cores provide a very high-resolution archive of palaeo-climate, they offer data over only a relatively short window of time (〈1 million years) and provide little information on how the ice and oceans were changing at the ice sheet periphery. By contrast, sediments derived from the Antarctic continent have discharged continuously to the continental slope and deeper ocean over millions of years, and are sensitive recorders of both ice sheet an oceanographic variability. Repeated continental margin-derived turbidity currents, in combination with the activity of along-slope currents, have led to the accumulation of large hemi-pelagic depositional bodies, termed sediment drifts that are, today, oriented orthogonal to the continental margin and record continuous sedimentation on the continental rise since at least the Miocene. Along the Antarctic Peninsula Pacific margin, a chain of twelve large sediment drifts separated out by channels eroded by turbidity currents provide unique archives of environmental changes in Antarctica‘s ice sheets and the Southern Ocean. IODP proposal 732FULL2 aims to recover drill cores extending back into the Pliocene from the crests of a number of the drifts, as well as from the top of the Belgica trough mouth fan, during a future leg to the region. Two further sites will recover older strata that can be accessed at relatively shallow depth by drilling through eroded drift flanks where the overburden is particularly thin. However, before recovering sequences from these bodies, a full understanding of their geometry, internal architecture, age and stratigraphic evolution is required. We present preliminary results from recent Natural Environment Research Council (UKIODP Programme) funded site survey cruise JR298 that obtained high-resolution multichannel seismic (MCS) reflection data over the proposed drill sites and adjacent working areas. A first look at the seismic data from several of the drilling targets will be presented, and some initial interpretations regarding the (i) sedimentary processes that operated during the formation and evolution of the drifts and fan, and (ii) links between depositional systems on the continental rise, palaeo-ice-sheet dynamics and past oceanographic processes within the datasets will be discussed. Further geophysical analyses, in combination with marine sediment cores retrieved from the proposed sites, will aim to shed light upon continental margin sediment delivery, Antarctic ice-sheet history and stability, and Antarctic margin palae-oceanography that form the key scientific objectives of the planned drilling campaign.