A5040092043- Cryospheric studies and observations
- Landslides and related hazards
- Winter Sports Injuries and Performance
- Seismic Waves and Analysis
- Climate change and permafrost
- Arctic and Antarctic ice dynamics
- Geology and Paleoclimatology Research
- Polar Research and Ecology
- Seismic Imaging and Inversion Techniques
- Methane Hydrates and Related Phenomena
- Icing and De-icing Technologies
- Seismology and Earthquake Studies
- Geophysical Methods and Applications
- Atmospheric and Environmental Gas Dynamics
- Atmospheric chemistry and aerosols
- Indigenous Studies and Ecology
- Advanced Optical Sensing Technologies
- Geological and Geochemical Analysis
- Science and Climate Studies
- Advanced Fiber Optic Sensors
- Drilling and Well Engineering
- Meteorological Phenomena and Simulations
- Geological Modeling and Analysis
- Tree-ring climate responses
- Geochemistry and Geologic Mapping
Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung
2016-2025
Utrecht University
2004
Marine‐terminating outlet glaciers of the Greenland Ice Sheet make significant contributions to global sea level rise, yet conditions that facilitate their fast flow remain poorly constrained owing a paucity data. We drilled and instrumented seven boreholes on Store Glacier, Greenland, monitor subglacial water pressure, temperature, electrical conductivity, turbidity along with englacial ice temperature deformation. These observations were supplemented by surface velocity meteorological...
Ice streams are major regulators of sea level change. However, standard viscous flow simulations their evolution have limited predictive power due to incomplete understanding involved processes. On the Greenland ice sheet, borehole fiber-optic observations reveal a brittle deformation mode that is incompatible with over length scales similar resolution modern sheet models: englacial quake cascades unobservable at surface. Nucleating near volcanism-related impurities promote grain boundary...
Abstract Nioghalvfjerdsfjorden Glacier (79NG) is the largest of three marine‐terminating outlet glaciers draining Northeast Greenland Ice Stream. To understand how Atlantic waters supply in cavity beneath floating 79NG, we analyze historic and recent bathymetric, hydrographic, velocity observations obtained on continental shelf. The bathymetry characterized by a trough system, consisting Westwind Trough Norske northern southern part shelf, respectively. recirculating Fram Strait cross shelf...
Abstract We present distributed fiber-optic sensing data from an airplane landing near the EastGRIP ice core drilling site on Northeast Greenland Ice Stream. The recordings of exceptional clarity contain at least 15 easily visible wave propagation modes corresponding to various Rayleigh, pseudoacoustic, and leaky waves. In frequency range 8 55 Hz, seven can be identified unambiguously. Based a priori firn model that matches P-wave dispersion fundamental Rayleigh mode, Backus–Gilbert...
We investigate the propagation of seismic waves in anisotropic ice. Two effects are important: (i) sudden changes crystal orientation fabric (COF) lead to englacial reflections; (ii) induces an angle dependency on velocities and, thus, recorded travel times. Velocities calculated from polycrystal elasticity tensor derived for measured COF eigenvalues EDML ice core, Antarctica, show good agreement with velocity trend determined vertical profiling. The absolute values, however, depends choice...
Abstract The Filchner‐Ronne Ice Shelf, the ocean cavity beneath it, and Weddell Sea that bounds form an important part of global climate system by modulating ice discharge from Antarctic Sheet producing cold dense water masses feed thermohaline circulation. A prerequisite for modeling sheet oceanographic processes within is accurate knowledge sub‐ice bedrock elevation, but shelf where airborne radar cannot penetrate, bathymetric data are sparse. This paper presents new seismic point...
ABSTRACT We compared elastic moduli in polar firn derived from diving wave refraction seismic velocity analysis, firn-core density measurements and microstructure modelling based on data. The data were obtained with a small electrodynamic vibrator source near Kohnen Station, East Antarctica. analysis of waves resulted velocity–depth profiles for different types (P-, SH- SV-waves). Dynamic by combining P- S-wave velocities densities measurements. structural finite-element method (FEM) was...
Ice streams are river-like features of ice sheets that move much faster than the surrounding, ice. This contrast in velocity (100s m/yr vs 10s m/yr) results from flow being dominated by basal sliding with a fully temperate bed within streams, whereas is little or not at all outside, where below melting point. Here, we present initial an ERC-funded project, PHAST, which seeks to unravel physics driving stream formation and dynamics. As part this seek characterize observationally onset...
Ice streams are major contributors to ice sheet mass loss and critical regulators of sea level change. Despite their importance, standard viscous flow simulations stream deformation evolution have limited predictive power, mostly because our understanding the involved processes is limited. This leads, for instance, widely varying predictions rise during next decades.Here we report on a Distributed Acoustic Sensing experiment conducted in borehole East Greenland Core Project (EastGRIP)...
Subglacial drainage systems exert control on glacier motion; however, the nature and evolution of these are not well established. Here, we report co-evolving state friction, water pressure flows at base Sermeq Kujalleq (Store Glacier), a fast-moving in west Greenland. Seismic records from centreline location major subglacial axis show stick-slip impulsive events (icequakes) to be far more frequent winter than summer. In contrast, amplitude low-frequency tremor low but high Additional insight...
Abstract In 2010 a reflection seismic survey was carried out on the Alpine glacier Colle Gnifetti. The processed and depth-converted data could be compared to nearby ice core, drilled almost bed. Comparisons showed that depth of P-wave bed too shallow, while SH-wave fitted ice-core length well. We are now able explain major part these differences using existing crystal orientations at calculate anisotropic velocities for P- SH-waves usually picked stacking compare them with zero-offset...
Outlet glaciers of the Greenland Ice Sheet transport ice from interior to ocean and contribute directly sea level rise because discharge ablation often exceed accumulation. To develop a better understanding these fast‐flowing glaciers, we investigate basal conditions Store Glacier, large outlet glacier flowing into Uummannaq Fjord in west Greenland. We use two crossing seismic profiles acquired near centerline, 30 km upstream calving front, interpret physical nature bed. identify one notably...
Abstract The shape of ice shelf cavities are a major source uncertainty in understanding ice‐ocean interactions. This limits assessments the response Antarctic sheets to climate change. Here we use vibroseis seismic reflection surveys map bathymetry beneath Ekström Ice Shelf, Dronning Maud Land. new reveals an inland‐sloping trough, reaching depths 1,100 m below sea level, near current grounding line, which attribute erosion by palaeo‐ice streams. trough does not cross‐cut outer parts...
Abstract. Ice shelves play a key role in the stability of Antarctic Sheet due to their buttressing effect. A loss as result increased basal melting or ice shelf disintegration will lead discharge. Some exhibit channels at base that are not yet fully understood. In this study, we present situ melt rates channel which is up 330 m high and located southern Filchner Shelf. Maximum observed 2 yr−1. Melt inside decrease direction flow turn freezing ∼55 km downstream grounding line. While closer...
SUMMARY Ice streams are major contributors to ice sheet mass loss and sea level rise. Effects of their dynamic behaviour imprinted into seismic properties, such as wave speeds anisotropy. Here, we present results from a distributed acoustic sensing (DAS) experiment in deep ice-core borehole the onset region Northeast Greenland Stream, with focus on phenomenological methodological aspects. A series active surface sources produced clear recordings P S wavefield, including internal reflections,...
Abstract Radio Echo Sounding (RES) surveys conducted in May 2010 and April 2011 revealed a 2 km flat area with increased bed reflectivity at the base of Isunnguata Sermia western margin Greenland Ice Sheet. This reflector was located within localized subglacial hydraulic potential (hydropotential) minimum, as part complex elongated trough system. By analogy comparable features Antarctica, initial interpretation such feature lake. In September 2013 co‐located seismic survey 1,750 m by 540 37...
Abstract This paper presents an overview of firn accumulation in Dronning Maud Land (DML), Antarctica, over the past 1000 years. It is based on a chronology established with dated volcanogenic horizons detected by dielectric profiling six medium-length cores. In 1998 British Antarctic Survey retrieved core from western DML. During Nordic EPICA (European Project for Ice Coring Antarctica) traverse 2000/01, 160 m long was drilled eastern Together previously published data four other ice cores...
Abstract A 100 m long ice core was retrieved from the coastal area of Dronning Maud Land (DML), Antarctica, in 2000/01 austral summer. The dated to AD 1737 by identification volcanic horizons dielectrical profiling and electrical conductivity measurement records combination with seasonal layer counting high-resolution oxygen isotope (δ 18 O) data. mean long-term accumulation rate 0.29 ma –1 w.e. derived δ O record as well rates during periods between identified horizons. statistically...
Abstract The breakup of Gondwana is manifested by coeval early Jurassic Karoo magmatism in South Africa and East Antarctica. In Africa, the large volumes volcanic rocks adjoining Lebombo Mwenetzi‐Save monoclines represent a rift margin, Antarctica, corresponding feature, Explora Wedge buried below sediments floating ice shelves on continental margin Dronning Maud Land. We use seismic vibrator source to explore sub‐ice geology new reflection available regional aeromagnetic data enable us...
Abstract. Curvilinear channels on the surface of an ice shelf indicate presence large at base. Modelling studies have shown that where these expressions intersect grounding line, they coincide with likely outflow subglacial water. An understanding initiation and ice–ocean evolution basal is required to understand present behaviour future dynamics sheets shelves. Here, we focused active seismic radar surveys a channel, ∼950 m wide ∼200 high, its upstream continuation beneath Support Force...
Abstract We investigate and quantify the variability of snow accumulation rate around a medium-depth firn core (160 m) drilled in east Dronning Maud Land, Antarctica (75°00′ S, 15°00’ E; 3470 m h.a.e. (ellipsoidal height)). present data from five pits shallow (20 cores distributed within 3.5–7 km distance, retrieved during 2000/01 Nordic EPICA (European Project for Ice Coring Antarctica) traverse. Snow rates estimated shorter periods show higher spatial variance than longer periods....
Firn air was sampled on the Antarctic plateau in Dronning Maud Land (DML), during Norwegian Research Expedition (NARE) 2000/2001. In this paper, we describe analyses for methyl chloride and nonmethane hydrocarbons (NMHCs) these firn samples. For first time, NMHCs ethane, propane, acetylene have been measured air, concentration profiles gases derived. A one‐dimensional numerical diffusion model used to interpret derive atmospheric concentrations as a function of time. The trends derived NMHC...
Abstract Explosive seismic reflection data from Halvfarryggen, a 910 m thick local ice dome of the Antarctic sheet, show numerous laterally continuous reflections within between 300 and 870 depth. We compare quality obtained with explosive sources that using vibroseis source for detecting englacial snowstreamer, investigate origin reflections. find in combination snowstreamer is ten times more productive than seismics. However, are clearly visible explosives, which have broader bandwidth...