1,721,800 research outputs found
Raw data of physical oceanography during RV POLARSTERN cruise PS134
No full textRaw physical oceanography data was acquired by a ship-based Seabird SBE911plus CTD-Rosette system onboard RV POLARSTERN during research cruise PS134. The CTD was equipped with duplicate sensors for temperature (SBE3plus) and conductivity (SBE4). Additional sensors such as an oxygen sensor (SBE43), a WET Labs C-Star transmissometer, a WET Labs ECO-AFL fluorometer (FLRTD) and an altimeter (Teledyne Benthos PSA-916) were mounted to the CTD. The data was recorded using pre-cruise calibration coefficients. No correction, post-cruise calibration or quality control was applied
Workshop - Amundsen Sea Embayment Tectonic and Glacial History - Programme and Abstracts
Full text linkOverall Objective: Review existing data and identify priorities for future geoscience research (terrestrial, marine and airborne) in the Amundsen Sea embayment (ASE) region required to develop a better understanding of the past, present and future behaviour of this sector of the West Antarctic Ice Sheet (WAIS).
Background: The ASE is the most rapidly changing sector of the WAIS and contains enough ice to raise global sea level by 1.2 m. Over the past few years considerable efforts have been made to acquire new data to improve knowledge of the geological structure, subglacial topography, continental shelf bathymetry and glacial history of this remote region. In this workshop we aim to review the current state of knowledge on the tectonic and glacial evolution of the Amundsen Sea embayment. Particular emphasis will be placed on work that will improve boundary conditions for ice sheet models (e.g. subglacial topography, shelf bathymetry, palaeotopography, heat flow and substrate types) and provide palaeo-data against which model outputs can be compared. There will also be a focus on plans and targets for future scientific drilling that will reveal the history of this sector of the WAIS and its sensitivity to major climate changes
Profile of sediment echo sounding during SONNE cruise SO169 with links to ParaSound data files
No full textAntarctic ice-shelf meltwater outflows in satellite radar imagery: ground-truthing and basal channel observations
No full textIce shelves regulate the flow of the Antarctic ice sheet toward the ocean and its contribution to sea-level rise. Accurately monitoring the basal and surface melting of ice shelves is therefore essential for predicting the ice sheet’s response to climatic warming. In this study, we utilize Sentinel-1A synthetic aperture radar satellite imagery combined with shipboard measurements of water temperature and salinity to investigate the presence of surficial meltwater plumes along the Antarctic coastline. Our approach reveals a strong correlation between areas of pronounced low radar backscatter extending from ice shelves and significant decreases in water temperature and salinity, suggesting meltwater-enriched ocean waters. We propose that the low radar backscatter signature of meltwater outflows is caused by stable stratification of the upper water column, driven by density contrasts from buoyant, low-salinity meltwater and surface current shear that reduce Bragg scattering waves. The resulting smooth water surfaces were observed adjacent to the surface expression of deep basal channels, documented in a helicopter survey along part of the Bellingshausen Sea ice edge. We present high-temporal resolution satellite radar as a tool for identifying meltwater release from beneath ice shelves, capable of all-weather, day-and-night imaging
Master track of POLARSTERN cruise PS134 in 1 sec resolution (zipped, 36.3 MB)
No full textRaw data acquired by position sensors on board RV Polarstern during expedition PS134 was processed to receive a validated master track which can be used as reference of further expedition data. During PS134 two Trimble Marine SPS855 GPS receivers and the iXBlue HYDRINS hydrographic survey inertial navigation system were used as navigation sensors. Data were downloaded from DAVIS SHIP data base (https://dship.awi.de) with a resolution of 1 sec. Processed data are provided as a master track with 1 sec resolution derived from the position sensors' data selected by priority and a generalized track with a reduced set of the most significant positions of the master track
Free-air anomaly data along profile AWI-20160400 during SONNE cruise SO246
No full textGravity data along seismic refraction profile AWI-20160400 was recorded during the cruise SO246 of the German RV SONNE along the central Chatham Rise, west of the Chatham Islands. This dataset contains the calculated free-air gravity anomaly data in 10s interval. See the SO246 cruise report for more information
Master tracks in different resolutions of POLARSTERN cruise PS134, Capetown – Punta Arenas, 2022-12-23 - 2023-03-06
No full textRaw data acquired by position sensors on board RV Polarstern during expedition PS134 was processed to receive a validated master track which can be used as reference of further expedition data. During PS134 two Trimble Marine SPS855 GPS receivers and the iXBlue HYDRINS hydrographic survey inertial navigation system were used as navigation sensors. Data were downloaded from DAVIS SHIP data base (https://dship.awi.de) with a resolution of 1 sec. Processed data are provided as a master track with 1 sec resolution derived from the position sensors' data selected by priority and a generalized track with a reduced set of the most significant positions of the master track
Track of SONNE cruise SO169 with links to navigation files in 1 and 10 sec interval
No full textTrack of SONNE cruise SO169 with links to navigation files in 1 and 10 sec interva
Thermal conductivities for geothermal heat flow estimates, cruise PS134
No full textThermal conductivities were measured on split sediment cores from cruise PS134 in the Bellingshausen Sea using the KD2 Decagon Thermal Properties Analyzer. The obtained values were corrected for ambient laboratory temperatures and used for geothermal heat flow estimates
Die Krustenentwicklung des Chatham Rise: Die Kollision mit dem Hikurangi Plateau und der Aufbruch zwischen dem Zealandia-Kontinent und der Antarktis in der mittleren Kreidezeit
No full textThe breakup of supercontinents is often associated with the changing polarity of tectonic forces from lithospheric convergence to lithospheric divergence. The initiation of the last supercontinent disintegration occurred simultaneously with the breakup of Gondwana. During the mid-Cretaceous, the East Gondwana margin underwent a remarkably fast transformation from a long-lived active subduction margin to a passive continental rifted margin, which led to the separation of southern Zealandia from West Antarctica. Recent studies suggest that the cessation of subduction and onset of extension in southern Zealandia was initiated by the collision and subduction of the thick oceanic Hikurangi Plateau with the East Gondwana subduction zone. However, little is known about the crustal structure of the Chatham Rise, east off New Zealand, although the Chatham Rise played a central role in change in tectonic forces. In particular, the nature of the southern Chatham Rise margin and the SE Chatham Terrace, an area of anomalously shallow seafloor hosting abundant seamounts and guyots, is poorly constrained.
To investigate the role of the Hikurangi Plateau collision and subduction on the onset of extension and rifting in southern Zealandia, geophysical data including wide-angle reflection and refraction seismic, multi-channel seismic reflection, and potential field data were acquired during RV Sonne cruise SO246 in 2016. Geophysical data were collected along four profiles across two sub-provinces of the Chatham Rise, the SE Chatham Terrace and adjacent oceanic crust. P-wave velocity and gravity modelling of the new geophysical data yield insights into the crustal structure and therefore the breakup mechanism of the southern Chatham Rise margin, constrain the extent of the Hikurangi Plateau underthrusted beneath the Chatham Rise, and enhance our understanding of the driving forces behind the abrupt change from subduction to rifting along the East Gondwana margin.
Along the Chatham Rise, the P-wave velocity models highlight distinct differences in the crustal thickness between the eastern and western sub-provinces, but also reveal common characteristics in crustal composition. The crust of the western Chatham Rise is up to 25 km thick, whereas the eastern Chatham Rise is substantially thinner (14-18 km). Modelled P-wave velocities and densities suggest a similar geology for both parts. The Chatham Rise mainly consists of greywackes, meta-greywackes, and schist in the upper crust, and their high-temperature equivalents in the lower crust. This is consistent with its past position at an active continental margin. Seismic imaging and gravity data show that the 10-16 km thick Hikurangi Plateau is restricted to the lower crust of the western Chatham Rise. The geophysical data suggest that the Hikurangi Plateau does not reach as far south as previously proposed. Furthermore, southward thinning of the lower crustal layer along the westernmost profile, together with previously published data, indicates that a piece of the subducted oceanic Phoenix Plate is still present below the Chatham Rise and southern Zealandia. The crustal thickness of the SE Chatham Terrace varies between 5 and 8 km, which can be correlated to slightly thinner or thicker than Pacific oceanic crust (~6 km thickness). The velocity structure can be interpreted as similar to Pacific oceanic crust, but at the same time also shows characteristics of hyper-extended continental crust. Since graben structures are present, I interpret the SE Chatham Terrace as a broad continent-ocean transition zone, which consists of very thin continental crust modified by magmatic activity. Typical Pacific oceanic crust has been only found close to the easternmost Chatham Rise and is presumably not older than 88 Ma. The Pacific oceanic crust is separated from the Chatham Rise by a highly faulted area, which I interpret as exhumed lower continental crust.
High-velocity lower crust (VP > 7 km/s) has been identified along the eastern Chatham Rise and at the easternmost Chatham Rise. These two areas of high-velocity lower crust are interpreted as magmatic underplating and intrusions. Seaward-dipping reflector sequences typical of volcanic-rifted margins are completely absent along the southern Chatham Rise margin. Moreover, the southern Chatham Rise margin is largely fault-controlled, but the geophysical data do not support the presence of exhumed and serpentinised upper mantle, which is typical for magma-poor margins. On this basis, I interpret the southern Chatham Rise margin as a unique hybrid rifted margin, which shows features typical of both, volcanic-rifted and magma-poor margins.
Based on these observations, I developed a tectonic model that explains the multi-stage tectonic evolution of the southern Chatham Rise margin. Accordingly, the Hikurangi Plateau entered the subduction zone at ~110 Ma. Subsequently, convergence velocities slowed down until subduction ceased at ~100 Ma. The thicker crust of the western Chatham Rise is a result of the subduction and underthrusting of the Hikurangi Plateau, which most likely attenuated subsequent crustal extension along the western Chatham Rise. Slowing subduction in the sector of the Hikurangi Plateau led to development of subduction-transform edge propagator (STEP) faults on both sides of the plateau after 110 Ma. I suggest that the Hikurangi Plateau collision, together with fragmentation of the Phoenix Plate by these STEP faults, triggered and / or contributed to the previously hypothesized global-scale plate reorganisation event between 105 and 100 Ma. At the same time, rifting and crustal extension in southern Zealandia started. The rifting in southern Zealandia and the evolution of the southern Chatham Rise were likely the result of complex slab dynamics triggered by the Hikurangi Plateau subduction. First, rifting was initiated by shallowing of the subducted slab due to the higher buoyancy of the young and thick Hikurangi Plateau. Initial extension was oblique to the margin and arc, and led to the reactivation of former arc-parallel E-W thrust faults as normal faults. With prolonged extension, new generations of NE-SW normal faults started to form, and lower crust was exhumed along the easternmost tip of the Chatham Rise was initiated. Secondly, progressive eclogitisation of the land-ward Phoenix Plate slab is likely to have caused the slab to rollback after convergence ceased. This led to a prolonged episode of rifting during which extension focussed on the southern Chatham Rise margin (i.e. the SE Chatham Terrace and Bounty Trough). Finally, the style of extension changed after most of the Phoenix Plate slab became detached at around 90 Ma. The slab detachment opened a pathway for deep-seated and hot upwelling mantle, which resulted in (I) intrusions and magmatic underplating, (II) formation of the first oceanic crust along the easternmost tip of the Chatham Rise, (III) alkaline magmatism on the Chatham Island between 85 and 82 Ma and (IV) magmatic overprint of the SE Chatham Terrace leading to seamount formation. After 85 Ma, spreading segments became connected and the formation of the young Pacific-Antarctic Ridge led to the final separation of Zealandia from Antarctica
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