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a Depth to acoustic basement. The thick, dark red curve is a proposed Weddell Gyre pathway between Antarctica and Maud Rise. b Total sediment thickness at the Lazarev Sea and DML margin. The thickness distribution appears to be constrained by basement morphology. Black lines and red stars represent multichannel seismic lines and ODP drilling sites, respectively
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The relief of Dronning Maud Land (DML), formed by Middle and Late Mesozoic tectonic activity, had a strong spatial control on the early fluvial and subsequent glacial erosion and deposition. The sources, processes, and products of sedimentation along the DML margin and in the Lazarev Sea in front of the DML mountains have been barely studied. The o...
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Antarctica is surrounded by floating ice shelves, which play a crucial role in regulating the flow of ice from the continent into the oceans. The ice shelves are susceptible to melting from warm ocean waters beneath them. In order to better understand the melting, knowledge of the shape and depth of the ocean cavity beneath i...
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... Only limited attention has been given to the Lazarev Sea, although this area is probably the most important sink area for the DML mountains, as the mountain range acts as a barrier for the terrigenous sediments from the East Antarctic interior. Thus, the majority of the sediments along the DML margin in the Lazarev Sea probably is derived from the mountain range itself 6 . ...
The coast-parallel Dronning Maud Land (DML) mountains represent a key nucleation site for the protracted glaciation of Antarctica. Their evolution is therefore of special interest for understanding the formation and development of the Antarctic ice sheet. Extensive glacial erosion has clearly altered the landscape over the past 34 Myr. Yet, the total erosion still remains to be properly constrained. Here, we investigate the power of low-temperature thermochronology in quantifying glacial erosion in-situ. Our data document the differential erosion along the DML escarpment, with up to c. 1.5 and 2.4 km of erosion in western and central DML, respectively. Substantial erosion at the escarpment foothills, and limited erosion at high elevations and close to drainage divides, is consistent with an escarpment retreat model. Such differential erosion suggests major alterations of the landscape during 34 Myr of glaciation and should be implemented in future ice sheet models. The topography of the Dronning Maud Land Mountains, Antarctica, has become more pronounced and rugged since preglacial times due to higher glacial erosion at low elevations and lower erosion at high elevations, according to low-temperature thermochronology
... and internal sedimentary stacking pattern of the mounded drift (M) could share some similarities with asymmetric channel-levee systems 9,34 or, channel-levee drifts from a mixed turbidite-contourite system 4,5,35 . However, in the absence of an observed feeder channel (or submarine canyon), and given the clear alongslope orientation and lateral continuity of the depositional and erosional features along the continental rise (rather than in the downslope orientation typically assumed by mixed turbidite-contourite systems), we consider here a pure Contourite Depositional System (CDS) and follow Gruetzner et al. (2012) 15 in interpreting M as a large asymmetric mounded drift, because it meets criteria listed in Hernández-Molina et al. (2008) 36 . ...
Contourite features are increasingly identified in seismic data, but the mechanisms controlling their evolution remain poorly understood. Using 2D multichannel reflection seismic and well data, this study describes large Oligocene- to middle Miocene-aged sedimentary bodies that show prominent lateral migration along the base of the Argentine slope. These form part of a contourite depositional system with four morphological elements: a plastered drift, a contourite channel, an asymmetric mounded drift, and an erosive surface. The features appear within four seismic units (SU1–SU4) bounded by discontinuities. Their sedimentary stacking patterns indicate three evolutionary stages: an onset stage (I) (~ 34–25 Ma), a growth stage (II) (~ 25–14 Ma), and (III) a burial stage (< 14 Ma). The system reveals that lateral migration of large sedimentary bodies is not only confined to shallow or littoral marine environments and demonstrates how bottom currents and secondary oceanographic processes influence contourite morphologies. Two cores of a single water mass, in this case, the Antarctic Bottom Water and its upper interface, may drive upslope migration of asymmetric mounded drifts. Seismic images also show evidence of recirculating bottom currents which have modulated the system’s evolution. Elucidation of these novel processes will enhance basin analysis and palaeoceanographic reconstructions.
... The repetition of this pattern throughout wDML suggests a link to former glacial extents, most likely via the formation of end moraines by ice sheets that advanced to the continental shelf edges during the Last Glacial Maximum (LGM, at 23-19 kyr BP; Grobe & Mackensen, 1992;Hillenbrand et al., 2014). Subglacial sediments deposited at shelf edges might be displaced downslope or be remobilized by currents to form contourites, as observed in seismic data close to the ice shelves of Dronning Maud Land by Huang and Jokat (2016). ...
Plain Language Summary
The grounded ice sheets of Antarctica are stabilized by floating ice shelves. Any loss in ice shelf mass is matched by an increase in ice sheet drainage, which contributes to rising sea level. The ice shelves of western Dronning Maud Land are currently in balance with an inland ice volume that has the potential to raise global sea level by nearly 1 m. Ice shelves lose most of their mass from their bases when warm water intrudes from the surrounding ocean. The extent to which this occurs depends on the depth and shape of the seafloor beneath the ice shelves. We have modeled water depths beneath the ice shelves of Dronning Maud Land using airborne gravity data and depth measurements from seismic, multibeam, and radar data. Our bathymetric models show deep troughs beneath the ice shelves and shallow sills close to the continental shelf. These sills currently limit water mass exchange with Warm Deep Water from the Southern Ocean and so protect the ice shelves from significant melting at their bases. A changing climate with increasing ocean temperatures or a shallowing of warm water masses may increase ice shelf melting and lead to an increased sea level contribution.
... Geographically, the present-day sedimentation pattern in the WG can be split into three geomorphological regions (Jerosch et al., 2016): (i) a southern and eastern region, influenced by downslope transport of sediments near the glaciated continental margin with channel-levee deposits and contourites (Michels et al., 2002); (ii) the central and northern WG, dominated by slowly accumulating sediments of mostly terrigenous origin (Geibert et al., 2005;Howe et al., 2007); and (iii) a northwestern part with contourites and hemipelagites (Gilbert et al., 1998;Pudsey et al., 1988). In addition, Maud Rise in the eastern part of the gyre (Huang & Jokat, 2016) and the Polarstern Bank in the southern Weddell Sea (Bart et al., 1999) stand out from the surrounding abyssal plain with a cover of biogenic sediments (Abelmann et al., 1990; Figure 2). ...
The Weddell Gyre (WG) is one of the main oceanographic features of the Southern Ocean south of the Antarctic Circumpolar Current which plays an influential role in global ocean circulation as well as gas exchange with the atmosphere. We review the state‐of‐the art knowledge concerning the WG from an interdisciplinary perspective, uncovering critical aspects needed to understand this system's role in shaping the future evolution of oceanic heat and carbon uptake over the next decades. The main limitations in our knowledge are related to the conditions in this extreme and remote environment, where the polar night, very low air temperatures, and presence of sea ice year‐round hamper field and remotely sensed measurements. We highlight the importance of winter and under‐ice conditions in the southern WG, the role that new technology will play to overcome present‐day sampling limitations, the importance of the WG connectivity to the low‐latitude oceans and atmosphere, and the expected intensification of the WG circulation as the westerly winds intensify. Greater international cooperation is needed to define key sampling locations that can be visited by any research vessel in the region. Existing transects sampled since the 1980s along the Prime Meridian and along an East‐West section at ~62°S should be maintained with regularity to provide answers to the relevant questions. This approach will provide long‐term data to determine trends and will improve representation of processes for regional, Antarctic‐wide, and global modeling efforts—thereby enhancing predictions of the WG in global ocean circulation and climate.
... The thicknesses are based on average interval velocities from sonobuoy records that enable a coarse depth migration of travel times in the network. Based on an error analysis of similar data sets further east around the East Antarctic margin, uncertainty in these thicknesses may reach 25% of the calculated values (Whittaker et al., 2013), with possible extra unquantifiable uncertainty attached to the fact that the onlap-defined stratigraphy can only be indirectly verified by extrapolation of the DSDP/ODP-tied stratigraphy in the Weddell Sea (Rogenhagen et al., 2004;Lindeque et al., 2013;Huang and Jokat, 2016). Using the 25% thickness uncertainty, and assuming average porosity to 7 km depth lies in the range 12-21% (based on Bahr et al.'s, 2001 compaction coefficients for sand and mud) the volume of clasts in basin A sediments amounts to something in the range between 2.9 × 10 5 and 4.2 × 10 5 km 3 . ...
Modelling-, rock cooling-, sedimentation- and exposure-based interpretations of the mechanisms by which topography evolves at extended continental margins vary widely. Observations from the margin of Dronning Maud Land, Antarctica, have until now not strongly contributed to these interpretations. Here, we present new airborne gravity and radar data describing the eastern part of this margin. Inland of a tall (2.5 km) great escarpment, a plateau topped by a branching network of valleys suggests preservation of a fluvial landscape with SW-directed drainage beneath a cold-based ice sheet. The valley floor slopes show that this landscape was modified during a period of alpine-style glaciation prior to the onset of the current cold-based phase around 34 Ma. The volume of sediments in basins offshore in the Riiser-Larsen Sea balances with the volume of rock estimated to have been eroded and transported by north-directed drainage from between the escarpment and the continental shelf break. The stratigraphy of these basins shows that most of the erosion occurred during the ~40 Myr following late Jurassic continental breakup. This erosion is unlikely to have been dominated by backwearing because the required rate of escarpment retreat to its present location is faster than numerical models of landscape evolution suggest to be possible. We suggest an additional component of erosion by downwearing seawards of a pre-existing inland drainage divide. The eastern termination of the great escarpment and inland plateau is at the West Ragnhild trough, a 300 km long, 15-20 km wide and up to 1.6 km deep subglacial valley hosting the West Ragnhild glacier. Numerous overdeepened (by >300 m) segments of the valley floor testify to its experience of significant glacial erosion. Thick late Jurassic and early Cretaceous sediments fanning out from the trough’s mouth into the eastern Riiser-Larsen Sea betray an earlier history as a river valley. The lack of late Jurassic relief-forming processes in this river’s catchment in the interior of East Antarctica suggests this erosion was related to regional climatic change.
Knowledge of Antarctica's sedimentary basins builds our understanding of the coupled evolution of tectonics, ice, ocean, and climate. Sedimentary basins have properties distinct from basement‐dominated regions that impact ice‐sheet dynamics, potentially influencing future ice‐sheet change. Despite their importance, our knowledge of Antarctic sedimentary basins is restricted. Remoteness, the harsh environment, the overlying ice sheet, ice shelves, and sea ice all make fieldwork challenging. Nonetheless, in the past decade the geophysics community has made great progress in internationally coordinated data collection and compilation with parallel advances in data processing and analysis supporting a new insight into Antarctica's subglacial environment. Here, we summarize recent progress in understanding Antarctica's sedimentary basins. We review advances in the technical capability of radar, potential fields, seismic, and electromagnetic techniques to detect and characterize basins beneath ice and advances in integrated multi‐data interpretation including machine‐learning approaches. These new capabilities permit a continent‐wide mapping of Antarctica's sedimentary basins and their characteristics, aiding definition of the tectonic development of the continent. Crucially, Antarctica's sedimentary basins interact with the overlying ice sheet through dynamic feedbacks that have the potential to contribute to rapid ice‐sheet change. Looking ahead, future research directions include techniques to increase data coverage within logistical constraints, and resolving major knowledge gaps, including insufficient sampling of the ice‐sheet bed and poor definition of subglacial basin structure and stratigraphy. Translating the knowledge of sedimentary basin processes into ice‐sheet modeling studies is critical to underpin better capacity to predict future change.
Little is known of the movements and seasonal occurrence of humpback whales (Megaptera novaeangliae) of South Africa and the Antarctic, populations once brought to near extinction by historic commercial whaling. We investigated the seasonal occurrence and diel-vocalizing pattern of humpback whale songs off the west coast of South Africa (migration route and opportunistic feeding ground) and the Maud Rise, Antarctica (feeding ground), using passive acoustic monitoring data collected between early 2014 and early 2017. Data were collected using acoustic autonomous recorders deployed 200-300 m below the sea surface in waters 855, 1,118 and 4,400 m deep. Acoustic data were manually analyzed for humpback whale vocalizations. While non-song calls were never identified, humpback whale songs were detected from June through December in South African waters, with a peak in percentage of acoustic occurrence around September/October in the austral spring. In Antarctic waters, songs were detected from March through May and in July (with a peak occurrence in April) where acoustic occurrence of humpback whales was negatively correlated to distance to the sea ice extent. Humpback whales were more vocally active at night than in the day at all recording sites. Detection range modelling indicates that humpback whale vocalizations could be detected as far as 18 and 45 km from recorders in South African and Antarctic waters, respectively. This study provides a multi-year description of the offshore acoustic occurrence of humpback whales off the west coast of South Africa and Maud Rise, Antarctica, regions that should continue to be monitored to understand these recovering populations.
Atolls are faithful recorders helping us understand eustatic variations, the evolution of carbonate production through time, and changes in magmatic hotspots activity. Several early Cretaceous Mid‐Pacific atolls were previously investigated through ocean drilling, but due to the low quality of vintage seismic data available few spatial constraints exist on their stratigraphic evolution and large‐scale diagenesis. Here we present results from an integrated core‐log‐seismic study at Resolution Guyot and comparison with modern and ancient analogues. We identify six seismic stratigraphic units: (1) platform initiation with aggradation and backstepping through the Hauterivian which ended by platform emersion; (2) reflooding of the platform with progradation and aggradation through the Barremian till the early‐Aptian when ocean anoxic event 1a resulted in incipient drowning; (3) platform backstepping till the mid‐Aptian when the platform shifted to progradation and aggradation till the mid‐Albian; (4) platform emersion; (5) reflooding with backstepping ending at the latest‐Albian by platform emersion; and (6) final drowning. The stratigraphic surfaces bounding these units are coeval with some of the Cretaceous eustatic events which suggest an eustatic control on the evolution of this atoll and confirm that several previously reported sea‐level variations in the early Cretaceous are driven by eustasy. Changes in subsidence and carbonate production rates and suspected later magmatism have also impacted the stratigraphic evolution. The suspected later magmatism could lead to environmental perturbations and potentially platform demise. Contrary to previous studies we identify two emersion events during the mid‐ and late‐Albian which resulted in intensive meteoric dissolution and karstification. The platform margin syndepositional fractures interacted with the subaerial exposure events by focusing the dissolution which formed vertically stacked flank‐margin fracture‐cave system. The study gives a unique insight on the interplay between eustasy, subsidence, and volcanic activity(ies) on long‐term evolution of early Cretaceous shallow‐marine carbonates. It also documents the impact and distribution of hypogenic and epigenic fluid‐flow in atolls serving as an analogue for isolated carbonate platforms.
