The Experts below are selected from a list of 753 Experts worldwide ranked by ideXlab platform
Hofstede Coen - One of the best experts on this subject based on the ideXlab platform.
-
Detailed Seismic Bathymetry Beneath Ekström Ice Shelf, Antarctica: Implications for Glacial History and Ice‐Ocean Interaction
'American Geophysical Union (AGU)', 2021Co-Authors: Smith, Emma C., Hattermann Tore, Kuhn Gerhard, Gaedicke Christoph, Berger Sophie, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Gromig Rapahel, Hofstede CoenAbstract:Abstract The shape of ice shelf cavities are a major source of uncertainty in understanding ice‐ocean interactions. This limits assessments of the response of the Antarctic ice sheets to climate change. Here we use Vibroseis seismic reflection surveys to map the bathymetry beneath the Ekström Ice Shelf, Dronning Maud Land. The new bathymetry reveals an inland‐sloping trough, reaching depths of 1,100 m below sea level, near the current grounding line, which we attribute to erosion by palaeo‐ice streams. The trough does not cross‐cut the outer parts of the continental shelf. Conductivity‐temperature‐depth profiles within the ice shelf cavity reveal the presence of cold water at shallower depths and tidal mixing at the ice shelf margins. It is unknown if warm water can access the trough. The new bathymetry is thought to be representative of many ice shelves in Dronning Maud Land, which together regulate the ice loss from a substantial area of East Antarctica.Plain Language Summary 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 ice shelves is crucial. In this study, we present new measurements of the sea floor depth beneath Ekström Ice Shelf in East Antarctica. The measurements reveal a much deeper sea floor than previously known. We discuss the implications of this for access of warm ocean waters, which can melt the base of the ice shelf and discuss how the observed sea floor features were formed by historical ice flow regimes. Although Ekström Ice Shelf is relatively small, the geometry described here is thought to be representative of the topography beneath many ice shelves in this region, which together regulate the ice loss from a substantial area of East Antarctica.Key Points Vibroseis seismic surveys used to map the ice shelf cavity beneath Ekström Ice Shelf in Antarctica Deep trough with transverse sills and overdeepenings provide evidence of past ice streaming and retreat Two ocean circulation regimes inferred in the shallow and deep parts of the cavityBelgian Science Policy ContractDeutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659DFG Cost S2S projectRD http://dx.doi.org/10.13039/10000993
-
Detailed Seismic Bathymetry Beneath Ekström Ice Shelf, Antarctica: Implications for Glacial History and Ice‐Ocean Interaction
'American Geophysical Union (AGU)', 2020Co-Authors: Smith Emma, Hattermann Tore, Kuhn Gerhard, Gaedicke Christoph, Berger Sophie, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Gromig Raphael, Hofstede CoenAbstract:The shape of ice shelf cavities are a major source of uncertainty in understanding ice‐ocean interactions. This limits assessments of the response of the Antarctic ice sheets to climate change. Here we use Vibroseis seismic reflection surveys to map the bathymetry beneath the Ekström Ice Shelf, Dronning Maud Land. The new bathymetry reveals an inland‐sloping trough, reaching depths of 1,100 m below sea level, near the current grounding line, which we attribute to erosion by palaeo‐ice streams. The trough does not cross‐cut the outer parts of the continental shelf. Conductivity‐temperature‐depth profiles within the ice shelf cavity reveal the presence of cold water at shallower depths and tidal mixing at the ice shelf margins. It is unknown if warm water can access the trough. The new bathymetry is thought to be representative of many ice shelves in Dronning Maud Land, which together regulate the ice loss from a substantial area of East Antarctica
-
What lies beneath: A detailed bathymetry of the sea-floor below Ekström Ice Shelf, East Antarctica
2019Co-Authors: Smith Emma, Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Franke Dieter, Hofstede Coen, Mayer Christoph, Lambrecht Astrid, Ehlers Todd, Tiedemann RalfAbstract:An extensive grid of seismic reflection data collected on Ekstro ̈m Ice Shelf, East Antarctica, between 2010–2018, using an on-ice Vibroseis source and snowstreamer, are used to make a detailed bathymetry map of the sea floorand ice-shelf cavity. The maps shows a deep sea-floor trough, likely a paleao-ice stream, under the western side ofthe ice shelf. The trough contains a number of points of higher topography, indicating probable former grounding line positions. At the shelf front a sill running across the width of the shelf has implications for ocean circulation and thus ice-ocean interaction and ice shelf melt. This new bathymetry is markedly different from previous models, which show a generally flat and shallow sea floor in the region. This is presumably the case for many of the smaller ice-shelves in Dronning Maud Land, which highlights the need for better bathymetry measurements in these key threshold regions
-
What lies beneath: A detailed bathymetry of the sea-floor below Ekström Ice Shelf, East Antarctica
2019Co-Authors: Smith, Emma C., Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Franke Dieter, Hofstede Coen, Mayer Christoph, Lambrecht Astrid, Ehlers Todd, Tiedemann RalfAbstract:An extensive grid of seismic reflection data collected on Ekstro¨m Ice Shelf, East Antarctica, between 2010–2018, using an on-ice Vibroseis source and snowstreamer, are used to make a detailed bathymetry map of the sea floor and ice-shelf cavity. The maps shows a deep sea-floor trough, likely a paleao-ice stream, under the western side of the ice shelf. The trough contains a number of points of higher topography, indicating probable former grounding line positions. At the shelf front a sill running across the width of the shelf has implications for ocean circulation and thus ice-ocean interaction and ice shelf melt. This new bathymetry is markedly different from previous models, which show a generally flat and shallow sea floor in the region. This is presumably the case for many of the smaller ice-shelves in Dronning Maud Land, which highlights the need for better bathymetry measurements in these key threshold region
-
On-ice Vibroseis: What lie beneath Ekström Ice Shelf, East Antarctica?
2018Co-Authors: Smith Emma, Kuhn Gerhard, Gaedicke Christoph, Franke Dieter, Hofstede Coen, Tiedemann Ralf, Mayer Christoph, Lambrecht Astrid, Ehlers Todd, Eisen OlafAbstract:Between 2010-2018 an extensive grid of seismic reflection data were collected across the grounding line and on the Ekström ice-shelf, using an on-ice Vibroseis source and snowstreamer. Here they are used to investigate current ice dynamics and reconstruct the glaciological history of this region. These data show the ice-shelf thickness ranges from 170 m, near the ice-shelf front, to ~600 m near the grounding line. Relic crevasses are seen at the ice base, in the Western part of the ice shelf, which can be tracked back to a current crevasse field at the grounding line. There is also evidence of an ice-shelf basal channel, with a corresponding surface depression. Beneath the sea floor the outcrop and sub-ice extent of the volcanic Explora Wedge (generated through Jurassic rifting and seafloor spreading) is clearly imaged. The wedge is overlain by a sequence of truncated, dipping marine-sediment layers. The sediment layers were likely truncated by former ice advance and subsequent retreat; which has also left evidence in the form topographic over-deepening and glacial debris deposits at the sea floor. The debris deposits range from elongated bedforms in a topographic trough (indicating probable former ice-stream flow) to layered sediment wedges at the current ice-shelf front (indicating the likely former extent of grounded ice). The Vibroseis method is fast and effective allowing for a high volume of data collection. For example, in the 2016/17 season ~280 km of multi-fold seismic reflection data were collected over a 25-day period. Future integration of these results with numerical models will provide a better understanding of past and present interactions between the ice sheet and the solid Earth in Dronning Maud Land, which will in turn improve understanding of future contributions of this region to sea-level rise
Mayer Christoph - One of the best experts on this subject based on the ideXlab platform.
-
Sea floor depth under Ekström Ice Shelf, Antarctica, from seismic Vibroseis surveys 2010-2018
PANGAEA, 2021Co-Authors: Smith, Emma Clare, Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Lambrecht Astrid, Hofstede, Coen Matthijs, Läufer Andreas, Mayer ChristophAbstract:Sea floor depth under Ekström Ice Shelf, Antarctica - from seismic reflection profiles collected between 2010 and 2018. For each seismic profile, the reflection time of the sea floor and ice-shelf base was identified and the depth to the sea floor was calculated using an ice velocity of 3601 m/s a sea-water velocity of 1451 m/s. The depths are referenced to mean sea-level (geoid EIGEN-6C4 ). The seismic data used here were collected using two different seismic Vibroseis sources. The same snow streamer was used for all data acquisition - a 1500 m long, 60 channel snow streamer, with 25 m group spacing. Each group contains eight gimballed P-wave SM-4, 14 Hz geo-phones. Please note these data are the point data used to create the gridded bathymetry product of the region, found here: doi:10.1594/PANGAEA.907951 Details of data acquisition and processing are given here: doi:10.1029/2019GL086187
-
Sea floor bathymetry under Ekström Ice Shelf, Antarctica, from a compilation of seismic Vibroseis data
PANGAEA, 2019Co-Authors: Smith, Emma Clare, Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Lambrecht Astrid, Hofstede, Coen Matthijs, Läufer Andreas, Mayer ChristophAbstract:A gridded bathymetry of the sea floor under Ekström Ice Shelf, Antarctica. The seismic data used to map the bathymetry were collected between 2010 and 2018, using two different seismic Vibroseis sources. The same snow streamer was used for all data acquisition - a 1500 m long, 60 channel snow streamer, with 25 m group spacing. Each group contains eight gimballed P-wave SM-4, 14 Hz geo-phones. For each seismic profile, the reflection time of the sea floor horizon was identified. The data across all profiles was gridded and depth converted, using an ice velocity of 3601 m/s a sea-water velocity of 1451 m/s
-
What lies beneath: A detailed bathymetry of the sea-floor below Ekström Ice Shelf, East Antarctica
2019Co-Authors: Smith, Emma C., Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Franke Dieter, Hofstede Coen, Mayer Christoph, Lambrecht Astrid, Ehlers Todd, Tiedemann RalfAbstract:An extensive grid of seismic reflection data collected on Ekstro¨m Ice Shelf, East Antarctica, between 2010–2018, using an on-ice Vibroseis source and snowstreamer, are used to make a detailed bathymetry map of the sea floor and ice-shelf cavity. The maps shows a deep sea-floor trough, likely a paleao-ice stream, under the western side of the ice shelf. The trough contains a number of points of higher topography, indicating probable former grounding line positions. At the shelf front a sill running across the width of the shelf has implications for ocean circulation and thus ice-ocean interaction and ice shelf melt. This new bathymetry is markedly different from previous models, which show a generally flat and shallow sea floor in the region. This is presumably the case for many of the smaller ice-shelves in Dronning Maud Land, which highlights the need for better bathymetry measurements in these key threshold region
-
What lies beneath: A detailed bathymetry of the sea-floor below Ekström Ice Shelf, East Antarctica
2019Co-Authors: Smith Emma, Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Franke Dieter, Hofstede Coen, Mayer Christoph, Lambrecht Astrid, Ehlers Todd, Tiedemann RalfAbstract:An extensive grid of seismic reflection data collected on Ekstro ̈m Ice Shelf, East Antarctica, between 2010–2018, using an on-ice Vibroseis source and snowstreamer, are used to make a detailed bathymetry map of the sea floorand ice-shelf cavity. The maps shows a deep sea-floor trough, likely a paleao-ice stream, under the western side ofthe ice shelf. The trough contains a number of points of higher topography, indicating probable former grounding line positions. At the shelf front a sill running across the width of the shelf has implications for ocean circulation and thus ice-ocean interaction and ice shelf melt. This new bathymetry is markedly different from previous models, which show a generally flat and shallow sea floor in the region. This is presumably the case for many of the smaller ice-shelves in Dronning Maud Land, which highlights the need for better bathymetry measurements in these key threshold regions
-
On-ice Vibroseis: Sediment features below Ekström Ice Shelf, East Antarctica
2018Co-Authors: Smith Emma, Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Franke Dieter, Hofstede Coen, Mayer Christoph, Lambrecht Astrid, Ehlers Todd, Tiedemann RalfAbstract:An extensive grid of seismic reflection data collected on Ekström Ice Shelf, East Antarctica, between 2010–2018, using an on-ice Vibroseis source and snowstreamer, are used to reconstruct the glaciological and tectonic history of this region. The data clearly image the outcrop and sub-ice extent of the volcanic Explora Wedge (generated through Jurassic rifting and seafloor spreading). The wedge is overlain by a sequence of truncated, dipping marine-sediment layers. The sediment were likely truncated by former ice advance and subsequent retreat; which has also left evidence in the form topographic over-deepening and glacial debris deposits at the sea floor. The debris deposits range from elongated bedforms in a topographic trough (indicating probable former ice-stream flow) to layered sediment wedges at the current ice-shelf front (indicating the likely former extent of grounded ice). A series of sub-ice shelf geological drilling campaigns in the area will take place (2017-2019) to recover sediments from the sea floor. Combining the topography and material characteristics from Vibroseis data with stratigraphic evidence from sediment cores allows a robust reconstruction in this area. Future integration of these results with numerical models will provide a better understanding of past and present interactions between the ice sheet and the solid Earth in Dronning Maud Land, which will in turn improve understanding of future contributions of this region to sea-level rise
Eisen Olaf - One of the best experts on this subject based on the ideXlab platform.
-
On-ice Vibroseis: What lie beneath Ekström Ice Shelf, East Antarctica?
2018Co-Authors: Smith Emma, Kuhn Gerhard, Gaedicke Christoph, Franke Dieter, Hofstede Coen, Tiedemann Ralf, Mayer Christoph, Lambrecht Astrid, Ehlers Todd, Eisen OlafAbstract:Between 2010-2018 an extensive grid of seismic reflection data were collected across the grounding line and on the Ekström ice-shelf, using an on-ice Vibroseis source and snowstreamer. Here they are used to investigate current ice dynamics and reconstruct the glaciological history of this region. These data show the ice-shelf thickness ranges from 170 m, near the ice-shelf front, to ~600 m near the grounding line. Relic crevasses are seen at the ice base, in the Western part of the ice shelf, which can be tracked back to a current crevasse field at the grounding line. There is also evidence of an ice-shelf basal channel, with a corresponding surface depression. Beneath the sea floor the outcrop and sub-ice extent of the volcanic Explora Wedge (generated through Jurassic rifting and seafloor spreading) is clearly imaged. The wedge is overlain by a sequence of truncated, dipping marine-sediment layers. The sediment layers were likely truncated by former ice advance and subsequent retreat; which has also left evidence in the form topographic over-deepening and glacial debris deposits at the sea floor. The debris deposits range from elongated bedforms in a topographic trough (indicating probable former ice-stream flow) to layered sediment wedges at the current ice-shelf front (indicating the likely former extent of grounded ice). The Vibroseis method is fast and effective allowing for a high volume of data collection. For example, in the 2016/17 season ~280 km of multi-fold seismic reflection data were collected over a 25-day period. Future integration of these results with numerical models will provide a better understanding of past and present interactions between the ice sheet and the solid Earth in Dronning Maud Land, which will in turn improve understanding of future contributions of this region to sea-level rise
-
Sedimentary sequences below the Ekström Ice Shelf, Dronning Maud Land, Antarctica: A pre-site survey for deep drilling (Sub-EIS-Obs)
DGGV and DMG, 2017Co-Authors: Kuhn Gerhard, Smith Emma, Gaedicke Christoph, Franke Dieter, Eisen Olaf, Leitchenkov German, Biskaborn, Boris K., Fromm Tanja, Mayer Christoph, Tiedemann RalfAbstract:During the last season and ongoing planning, pre-site surveys are operated at the Ekströmisen, Dronning Maud Land, close to the Neumayer-Station III, with the primary target to build a stratigraphic age framework of the under-shelf-ice-sediments. These sediments are overlying the Explora Wedge [1], [2], a syn- or postrift volcanic deposit, and dipping north- to north-eastward. Expected ages could range from Late Mesozoic to Quaternary. From new Vibroseismic profiles we will select sites for short core seafloor sampling of the oldest and of the youngest sediment sequences to confine their age time span. After that, we could select one or several sites for potential deep drillings (several hundred-meter-deep) with the support of international partner, if we could rise interest. The deep drillings should recover the sediments overlying the Explora Escarpment, and should discover the nature of the Explora Wedge as well. We expect that the overlying sediment sequences could reveal the history of polar amplification and climate changes in this part of Antarctica, the build-up of the East Antarctic Ice Sheet during past warmer climates and its Cenozoic and future dynamic and variability. The plan for seasons 2017/18 and 2018/19 are the testing of different sea floor sampling techniques through Hot Water Drill (HWD) holes. To select the drill sites for this shallow coring additional high resolution seismic will be acquired as well. Having holes through the shelf ice and sampling the sea floor will provide the unique opportunity for further piggy bag experiments consisting of multi-disciplinary nature. Experiments and measuring setup for oceanography, sea and shelf ice physics, geophysics, geology, hydrography, and biogeochemistry could be planned to characterize the sea-ice and shelf ice system, underlying water column, and the sediments. Video characterization underneath the shelf ice and at the seafloor, sediment trap deployment, seafloor mapping with an AUV (Leng, DFKI, ROBEX) could lead as well to innovative new interdisciplinary observations and discoveries of the sub-ice environment and ecosystem [3]. References: [1] Eisen, O., Hofstede, C., Diez, A., Kristoffersen, Y., Lambrecht, A., Mayer, C., Blenkner, R. & Hilmarsson, S., (2015), On-ice Vibroseis and snowstream¬er systems for geoscientific research, Polar Science, 51-65, 9, http://dx.doi.org/10.1016/j.polar.2014.10.003. [2] Kristoffersen, Y., Hofstede, C., Diez, A., Blenkner, R., Lambrecht, A., Mayer, C. & Eisen, O., (2014), Reassembling Gondwana: A new high quality constraint from Vibroseis exploration of the sub-ice shelf geology of the East Antarctic continental margin, J. Geophys. Res. Solid Earth, 9171-9182, 119 [3] Kuhn, G. & Gaedicke, C., (2015), A plan for interdisciplinary process-studies and geoscientific observations beneath the Ekström Ice Shelf (Sub-EIS-Obs), Polarforschung, 99-102, 8
-
Sediment features at the grounding zone and beneath Ekström Ice Shelf, East Antarctica, imaged using on-ice Vibroseis
2017Co-Authors: Smith, Emma C., Hofstede Coen, Eisen Olaf, Mayer Christoph, Lambrecht Astrid, Franke DieterAbstract:The grounding zone, where an ice sheet becomes a floating ice shelf, is known to be a key threshold region for ice flow and stability. A better understanding of ice dynamics and sediment transport across such zones will improve knowledge about contemporary and palaeo ice flow, as well as past ice extent. Here we present a set of seismic reflection profiles crossing the grounding zone and continuing to the shelf edge of Ekström Ice Shelf, East Antarctica. Using an on-ice Vibroseis source combined with a snowstreamer we have imaged a range of sub-glacial and sub-shelf sedimentary and geomorphological features; from layered sediment deposits to elongated flow features. The acoustic properties of the features as well as their morphology allow us to draw conclusions as to their material properties and origin. These results will eventually be integrated with numerical models of ice dynamics to quantify past and present interactions between ice and the solid Earth in East Antarctica; leading to a better understanding of future contributions of this region to sea-level rise
-
On-ice Vibroseis and snowstreamer systems for geoscientific research
'Elsevier BV', 2015Co-Authors: Eisen Olaf, Hofstede Coen, Mayer Christoph, Diez Anja, Kristoffersen Yngve, Lambrecht Astrid, Blenkner Rick, Hilmarsson, Sverrir Æ.Abstract:We present implementations of Vibroseis system configurations with a snowstreamer for over-ice long-distance seismic traverses (>100 km). The configurations have been evaluated in Antarctica on ice sheet and ice shelf areas in the period 2010–2014. We discuss results of two different Vibroseis sources: Failing Y-1100 on skis with a peak force of 120 kN in the frequency range 10–110 Hz; IVI EnviroVibe with a nominal peak force of 66 kN in the nominal frequency range 10–300 Hz. All measurements used a well-established 60 channel 1.5 km snowstreamer for the recording. Employed forces during sweeps were limited to less than 80% of the peak force. Maximum sweep frequencies, with a typical duration of 10 s, were 100 and 250 Hz for the Failing and EnviroVibe, respectively. Three different concepts for source movement were employed: the Failing vibrator was mounted with wheels on skis and pulled by a Pistenbully snow tractor. The EnviroVibe was operated self-propelled on Mattracks on the Antarctic plateau. This lead to difficulties in soft snow. For later implementations the EnviroVibe with tracks was put on a polyethylene (PE) sled. The sled had a hole in the center to lower the vibrator baseplate directly onto the snow surface. With the latter setup, data production varied between 20 km/day for 6-fold and 40 km/day for single fold for 9 h/day of measurements. The combination of tracks with the PE-sled was especially advantageous on hard and rough surfaces because of the flexibility of each component and the relatively lose mounting. The systems presented here are suitable to obtain data of subglacial and sub-seabed sediment layers and englacial layering in comparable quality as obtained from marine geophysics and land-based explosive surveys. The large offset aperture of the streamer overcomes limitations of radar systems for imaging of steep along-track subglacial topography. With joint international scientific and logistic efforts, large-scale mapping of Antarctica's and Greenland's subglacial geology, ice-shelf cavity geometries and sea-bed strata, as well as englacial structures can be achieved
-
Operational Vibroseis system for long-distance traverses
2014Co-Authors: Eisen Olaf, Hofstede Coen, Mayer Christoph, Diez Anja, Kristoffersen Yngve, Lambrecht Astrid, Blenkner Rick, Hilmarsson SverrirAbstract:This poster presents results and performance of an operational Vibroseis system used in Antarctica on the Ekströmisen and its catchment area. The about 500 km long overland traverse covered very different surface regimes in the elevation range from sea level up to 1000 m in the austral season 2013/14. The presentation is the successful culmination of a six-year effort to develop an operational Vibroseis system for Antarctica and Greenland. Over three weeks the campaign acquired: • 407 km of seismic profiles in total, thereof • 110 km in 6-fold resolution with 125 m shot spacing • 25 km in 3-fold resolution with 250 m shot spacing. The remaining distance was covered in single-fold with 750 m shot spacing. The traverse used a well-established 60 channel 1.5 km streamer and a new setup with a Vibroseis Buggy “EnviroVibe” with Mattracks on a polyethylen sled. The sled had a hole in the center to lower the vibrator pad directly onto the snow surface. With this setup data production varied between 20 km/day for 6-fold and 40 km/day for single fold for a decent 9h day of measurements. The combination of Mattracks with the PE-sled was especially advantageous on hard and rough surfaces because of the flexibility of each and the relatively lose mounting by cargo straps and wooden blocks. Production speeds were limited by the snow streamer, which had an increasing damage rate of geophone groups for velocities above 6 km/h. The source system itself could easily accommodate transfer velocities of 15 km/h. In combination with the streamer winch mounted in front of the source on a separate freight sled the channel spacing could be reduced to fractions of the 25 m spacing interval by combining several sweeps at the same location, thus increasing spatial resolution. The vibrator source was operated with a 10-250 Hz sweep over 10 s with 80% of the peak force of 66 kN. On soft surfaces a setup-sweep was utilized. Preliminary data analysis shows that sea floor geomorphology, subglacial sedimentary layering and englacial layering can be clearly imaged in the respective resolution of the source’s bandwidth. Interestingly, the ration of p-wave to s-wave energy varied considerably depending on the surface characteristics. In comparison to airborne and ground-based radar surveys, the system was able to image very steep sidewalls of subglacial trenches because of the large offset aperture where radar systems did not provide any reflections. Such system will help to considerably improve the future characterisation of sublglacial and englacial environments
Franke Dieter - One of the best experts on this subject based on the ideXlab platform.
-
Detailed Seismic Bathymetry Beneath Ekström Ice Shelf, Antarctica: Implications for Glacial History and Ice‐Ocean Interaction
'American Geophysical Union (AGU)', 2021Co-Authors: Smith, Emma C., Hattermann Tore, Kuhn Gerhard, Gaedicke Christoph, Berger Sophie, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Gromig Rapahel, Hofstede CoenAbstract:Abstract The shape of ice shelf cavities are a major source of uncertainty in understanding ice‐ocean interactions. This limits assessments of the response of the Antarctic ice sheets to climate change. Here we use Vibroseis seismic reflection surveys to map the bathymetry beneath the Ekström Ice Shelf, Dronning Maud Land. The new bathymetry reveals an inland‐sloping trough, reaching depths of 1,100 m below sea level, near the current grounding line, which we attribute to erosion by palaeo‐ice streams. The trough does not cross‐cut the outer parts of the continental shelf. Conductivity‐temperature‐depth profiles within the ice shelf cavity reveal the presence of cold water at shallower depths and tidal mixing at the ice shelf margins. It is unknown if warm water can access the trough. The new bathymetry is thought to be representative of many ice shelves in Dronning Maud Land, which together regulate the ice loss from a substantial area of East Antarctica.Plain Language Summary 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 ice shelves is crucial. In this study, we present new measurements of the sea floor depth beneath Ekström Ice Shelf in East Antarctica. The measurements reveal a much deeper sea floor than previously known. We discuss the implications of this for access of warm ocean waters, which can melt the base of the ice shelf and discuss how the observed sea floor features were formed by historical ice flow regimes. Although Ekström Ice Shelf is relatively small, the geometry described here is thought to be representative of the topography beneath many ice shelves in this region, which together regulate the ice loss from a substantial area of East Antarctica.Key Points Vibroseis seismic surveys used to map the ice shelf cavity beneath Ekström Ice Shelf in Antarctica Deep trough with transverse sills and overdeepenings provide evidence of past ice streaming and retreat Two ocean circulation regimes inferred in the shallow and deep parts of the cavityBelgian Science Policy ContractDeutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659DFG Cost S2S projectRD http://dx.doi.org/10.13039/10000993
-
Sea floor depth under Ekström Ice Shelf, Antarctica, from seismic Vibroseis surveys 2010-2018
PANGAEA, 2021Co-Authors: Smith, Emma Clare, Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Lambrecht Astrid, Hofstede, Coen Matthijs, Läufer Andreas, Mayer ChristophAbstract:Sea floor depth under Ekström Ice Shelf, Antarctica - from seismic reflection profiles collected between 2010 and 2018. For each seismic profile, the reflection time of the sea floor and ice-shelf base was identified and the depth to the sea floor was calculated using an ice velocity of 3601 m/s a sea-water velocity of 1451 m/s. The depths are referenced to mean sea-level (geoid EIGEN-6C4 ). The seismic data used here were collected using two different seismic Vibroseis sources. The same snow streamer was used for all data acquisition - a 1500 m long, 60 channel snow streamer, with 25 m group spacing. Each group contains eight gimballed P-wave SM-4, 14 Hz geo-phones. Please note these data are the point data used to create the gridded bathymetry product of the region, found here: doi:10.1594/PANGAEA.907951 Details of data acquisition and processing are given here: doi:10.1029/2019GL086187
-
Detailed Seismic Bathymetry Beneath Ekström Ice Shelf, Antarctica: Implications for Glacial History and Ice‐Ocean Interaction
'American Geophysical Union (AGU)', 2020Co-Authors: Smith Emma, Hattermann Tore, Kuhn Gerhard, Gaedicke Christoph, Berger Sophie, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Gromig Raphael, Hofstede CoenAbstract:The shape of ice shelf cavities are a major source of uncertainty in understanding ice‐ocean interactions. This limits assessments of the response of the Antarctic ice sheets to climate change. Here we use Vibroseis seismic reflection surveys to map the bathymetry beneath the Ekström Ice Shelf, Dronning Maud Land. The new bathymetry reveals an inland‐sloping trough, reaching depths of 1,100 m below sea level, near the current grounding line, which we attribute to erosion by palaeo‐ice streams. The trough does not cross‐cut the outer parts of the continental shelf. Conductivity‐temperature‐depth profiles within the ice shelf cavity reveal the presence of cold water at shallower depths and tidal mixing at the ice shelf margins. It is unknown if warm water can access the trough. The new bathymetry is thought to be representative of many ice shelves in Dronning Maud Land, which together regulate the ice loss from a substantial area of East Antarctica
-
Sea floor bathymetry under Ekström Ice Shelf, Antarctica, from a compilation of seismic Vibroseis data
PANGAEA, 2019Co-Authors: Smith, Emma Clare, Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Lambrecht Astrid, Hofstede, Coen Matthijs, Läufer Andreas, Mayer ChristophAbstract:A gridded bathymetry of the sea floor under Ekström Ice Shelf, Antarctica. The seismic data used to map the bathymetry were collected between 2010 and 2018, using two different seismic Vibroseis sources. The same snow streamer was used for all data acquisition - a 1500 m long, 60 channel snow streamer, with 25 m group spacing. Each group contains eight gimballed P-wave SM-4, 14 Hz geo-phones. For each seismic profile, the reflection time of the sea floor horizon was identified. The data across all profiles was gridded and depth converted, using an ice velocity of 3601 m/s a sea-water velocity of 1451 m/s
-
What lies beneath: A detailed bathymetry of the sea-floor below Ekström Ice Shelf, East Antarctica
2019Co-Authors: Smith, Emma C., Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Franke Dieter, Hofstede Coen, Mayer Christoph, Lambrecht Astrid, Ehlers Todd, Tiedemann RalfAbstract:An extensive grid of seismic reflection data collected on Ekstro¨m Ice Shelf, East Antarctica, between 2010–2018, using an on-ice Vibroseis source and snowstreamer, are used to make a detailed bathymetry map of the sea floor and ice-shelf cavity. The maps shows a deep sea-floor trough, likely a paleao-ice stream, under the western side of the ice shelf. The trough contains a number of points of higher topography, indicating probable former grounding line positions. At the shelf front a sill running across the width of the shelf has implications for ocean circulation and thus ice-ocean interaction and ice shelf melt. This new bathymetry is markedly different from previous models, which show a generally flat and shallow sea floor in the region. This is presumably the case for many of the smaller ice-shelves in Dronning Maud Land, which highlights the need for better bathymetry measurements in these key threshold region
Kuhn Gerhard - One of the best experts on this subject based on the ideXlab platform.
-
Detailed Seismic Bathymetry Beneath Ekström Ice Shelf, Antarctica: Implications for Glacial History and Ice‐Ocean Interaction
'American Geophysical Union (AGU)', 2021Co-Authors: Smith, Emma C., Hattermann Tore, Kuhn Gerhard, Gaedicke Christoph, Berger Sophie, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Gromig Rapahel, Hofstede CoenAbstract:Abstract The shape of ice shelf cavities are a major source of uncertainty in understanding ice‐ocean interactions. This limits assessments of the response of the Antarctic ice sheets to climate change. Here we use Vibroseis seismic reflection surveys to map the bathymetry beneath the Ekström Ice Shelf, Dronning Maud Land. The new bathymetry reveals an inland‐sloping trough, reaching depths of 1,100 m below sea level, near the current grounding line, which we attribute to erosion by palaeo‐ice streams. The trough does not cross‐cut the outer parts of the continental shelf. Conductivity‐temperature‐depth profiles within the ice shelf cavity reveal the presence of cold water at shallower depths and tidal mixing at the ice shelf margins. It is unknown if warm water can access the trough. The new bathymetry is thought to be representative of many ice shelves in Dronning Maud Land, which together regulate the ice loss from a substantial area of East Antarctica.Plain Language Summary 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 ice shelves is crucial. In this study, we present new measurements of the sea floor depth beneath Ekström Ice Shelf in East Antarctica. The measurements reveal a much deeper sea floor than previously known. We discuss the implications of this for access of warm ocean waters, which can melt the base of the ice shelf and discuss how the observed sea floor features were formed by historical ice flow regimes. Although Ekström Ice Shelf is relatively small, the geometry described here is thought to be representative of the topography beneath many ice shelves in this region, which together regulate the ice loss from a substantial area of East Antarctica.Key Points Vibroseis seismic surveys used to map the ice shelf cavity beneath Ekström Ice Shelf in Antarctica Deep trough with transverse sills and overdeepenings provide evidence of past ice streaming and retreat Two ocean circulation regimes inferred in the shallow and deep parts of the cavityBelgian Science Policy ContractDeutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659DFG Cost S2S projectRD http://dx.doi.org/10.13039/10000993
-
Sea floor depth under Ekström Ice Shelf, Antarctica, from seismic Vibroseis surveys 2010-2018
PANGAEA, 2021Co-Authors: Smith, Emma Clare, Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Lambrecht Astrid, Hofstede, Coen Matthijs, Läufer Andreas, Mayer ChristophAbstract:Sea floor depth under Ekström Ice Shelf, Antarctica - from seismic reflection profiles collected between 2010 and 2018. For each seismic profile, the reflection time of the sea floor and ice-shelf base was identified and the depth to the sea floor was calculated using an ice velocity of 3601 m/s a sea-water velocity of 1451 m/s. The depths are referenced to mean sea-level (geoid EIGEN-6C4 ). The seismic data used here were collected using two different seismic Vibroseis sources. The same snow streamer was used for all data acquisition - a 1500 m long, 60 channel snow streamer, with 25 m group spacing. Each group contains eight gimballed P-wave SM-4, 14 Hz geo-phones. Please note these data are the point data used to create the gridded bathymetry product of the region, found here: doi:10.1594/PANGAEA.907951 Details of data acquisition and processing are given here: doi:10.1029/2019GL086187
-
Detailed Seismic Bathymetry Beneath Ekström Ice Shelf, Antarctica: Implications for Glacial History and Ice‐Ocean Interaction
'American Geophysical Union (AGU)', 2020Co-Authors: Smith Emma, Hattermann Tore, Kuhn Gerhard, Gaedicke Christoph, Berger Sophie, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Gromig Raphael, Hofstede CoenAbstract:The shape of ice shelf cavities are a major source of uncertainty in understanding ice‐ocean interactions. This limits assessments of the response of the Antarctic ice sheets to climate change. Here we use Vibroseis seismic reflection surveys to map the bathymetry beneath the Ekström Ice Shelf, Dronning Maud Land. The new bathymetry reveals an inland‐sloping trough, reaching depths of 1,100 m below sea level, near the current grounding line, which we attribute to erosion by palaeo‐ice streams. The trough does not cross‐cut the outer parts of the continental shelf. Conductivity‐temperature‐depth profiles within the ice shelf cavity reveal the presence of cold water at shallower depths and tidal mixing at the ice shelf margins. It is unknown if warm water can access the trough. The new bathymetry is thought to be representative of many ice shelves in Dronning Maud Land, which together regulate the ice loss from a substantial area of East Antarctica
-
Sea floor bathymetry under Ekström Ice Shelf, Antarctica, from a compilation of seismic Vibroseis data
PANGAEA, 2019Co-Authors: Smith, Emma Clare, Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Ehlers, Todd A., Franke Dieter, Lambrecht Astrid, Hofstede, Coen Matthijs, Läufer Andreas, Mayer ChristophAbstract:A gridded bathymetry of the sea floor under Ekström Ice Shelf, Antarctica. The seismic data used to map the bathymetry were collected between 2010 and 2018, using two different seismic Vibroseis sources. The same snow streamer was used for all data acquisition - a 1500 m long, 60 channel snow streamer, with 25 m group spacing. Each group contains eight gimballed P-wave SM-4, 14 Hz geo-phones. For each seismic profile, the reflection time of the sea floor horizon was identified. The data across all profiles was gridded and depth converted, using an ice velocity of 3601 m/s a sea-water velocity of 1451 m/s
-
What lies beneath: A detailed bathymetry of the sea-floor below Ekström Ice Shelf, East Antarctica
2019Co-Authors: Smith, Emma C., Kuhn Gerhard, Gaedicke Christoph, Drews Reinhard, Franke Dieter, Hofstede Coen, Mayer Christoph, Lambrecht Astrid, Ehlers Todd, Tiedemann RalfAbstract:An extensive grid of seismic reflection data collected on Ekstro¨m Ice Shelf, East Antarctica, between 2010–2018, using an on-ice Vibroseis source and snowstreamer, are used to make a detailed bathymetry map of the sea floor and ice-shelf cavity. The maps shows a deep sea-floor trough, likely a paleao-ice stream, under the western side of the ice shelf. The trough contains a number of points of higher topography, indicating probable former grounding line positions. At the shelf front a sill running across the width of the shelf has implications for ocean circulation and thus ice-ocean interaction and ice shelf melt. This new bathymetry is markedly different from previous models, which show a generally flat and shallow sea floor in the region. This is presumably the case for many of the smaller ice-shelves in Dronning Maud Land, which highlights the need for better bathymetry measurements in these key threshold region
