24 research outputs found
ADMAP-2: The next-generation Antarctic magnetic anomaly map
The Antarctic Digital Magnetic Anomaly Project compiled the first international magnetic anomaly map of
the Antarctic region south of 60\ubaS (ADMAP-1) some six years after its 1995 launch (Golynsky et al., 2001;
Golynsky et al., 2007; von Frese et al., 2007). This magnetic anomaly compilation provided new insights into the
structure and evolution of Antarctica, including its Proterozoic-Archaean cratons, Proterozoic-Palaeozoic orogens,
Palaeozoic-Cenozoic magmatic arc systems, continental rift systems and rifted margins, large igneous provinces
and the surrounding oceanic gateways. The international working group produced the ADMAP-1 database from
more than 1.5 million line-kilometres of terrestrial, airborne, marine and satellite magnetic observations collected
during the IGY 1957-58 through 1999.
Since the publication of the first magnetic anomaly map, the international geomagnetic community has acquired
more than 1.9 million line-km of new airborne and marine data. This implies that the amount of magnetic
anomaly data over the Antarctic continent has more than doubled. These new data provide important constraints
on the geology of the enigmatic Gamburtsev Subglacial Mountains and Prince Charles Mountains, Wilkes Land,
Dronning Maud Land, and other largely unexplored Antarctic areas (Ferraccioli et al., 2011, Aitken et al., 2014 \u327
Mieth & Jokat, 2014, Golynsky et al., 2013).
The processing of the recently acquired data involved quality assessments by careful statistical analysis of the
crossover errors. All magnetic data used in the ADMAP-2 compilation were delivered as profiles, although several
of them were in raw form. Some datasets were decimated or upward continued to altitudes of 4 km or higher with
the higher frequency geological signals smoothed out. The line data used for the ADMAP-1 compilation were
reprocessed for obvious errors and residual corrugations. The new near-surface magnetic data were corrected for
the international geomagnetic reference field and diurnal effects, edited for high-frequency errors, and levelled to
minimize line-correlated noise.
The magnetic anomaly data collected mainly in the 21-st century clearly cannot be simply stitched together with
the previous surveys. Thus, mutual levelling adjustments were required to accommodate overlaps in these surveys.
The final compilation merged all the available aeromagnetic and marine grids to create the new composite grid
of the Antarctic with minimal mismatch along the boundaries between the datasets. Regional coverage gaps in
the composite grid will be filled with anomaly estimates constrained by both the near-surface data and satellite
magnetic observations taken mainly from the CHAMP and Swarm missions.
Magnetic data compilations are providing tantalizing new views into regional-scale subglacial geology and crustal
architecture in interior of East and West Antarctica. The ADMAP-2 map provides a new geophysical foundation
to better understand the geological structure and tectonic history of Antarctica and surrounding marine areas. In
particular, it will provide improved constraints on the lithospheric transition of Antarctica to its oceanic basins,
and thus enable improved interpretation of the geodynamic evolution of the Antarctic lithosphere that was a key
component in the assembly and break-up of the Rodinia and Gondwana supercontinents.
This work was supported by the Korea Polar Research Institute
Basal conditions for Pine Island and Thwaites Glaciers, West Antarctica, determined using satellite and airborne data
We use models constrained by remotely sensed data from Pine Island and Thwaites Glaciers, West Antarctica, to infer basal properties that are difficult to observe directly. The results indicate strong basal melting in areas upstream of the grounding lines of both glaciers, where the ice flow is fast and the basal shear stress is large. Farther inland, we find that both glaciers have 'mixed' bed conditions, with extensive areas of both bedrock and weak till. In particular, there are weak areas along much of Pine Island Glacier's main trunk that could prove unstable if it retreats past the band of strong bed just above its current grounding line. in agreement with earlier studies, our forward ice-stream model shows a strong sensitivity to small perturbations in the grounding line position. These results also reveal a large sensitivity to the assumed bed (sliding or deforming) model, with non-linear sliding laws producing substantially greater dynamic response than earlier simulations that assume a linear-viscous till rheology. Finally, comparison indicates that our results using a plastic bed are compatible with the limited observational constraints and theoretical work that suggests an upper bound exists on maximum basal shear stress
Analysing aeromagnetic, airborne gravity and radar data to unveil variable basal boundary conditions for the East Antarctic Ice Sheet in the Wilkes Subglacial Basin
The Wilkes Subglacial Basin (WSB) extends for ca 1,400 km from George V Land into the interior of East Antarc-
tica and hosts several major glaciers that drain a large sector of the East Antarctic Ice Sheet (EAIS). The region
is of major significance for assessing the long-term stability of the EAIS, as it lies well below sea level and its
bedrock deepens inland. This makes it potentially more prone to marine ice sheet instability, much like areas of the
West Antarctic Ice Sheet (WAIS) that are presently experiencing significant mass loss. This sector of the EAIS has
also become a focus of current research within IODP Leg 318 that aims to better comprehend the initial stages of
glaciation and the history and stability of the EAIS since the Eocene-Oligocene boundary. Understanding geologi-
cal boundary conditions onshore is important to assess their influence on ice sheet dynamics and long-term stability
and interpret the paleo-ice sheet record. Early geophysical models inferred the existence of a major extensional
sedimentary basin beneath the WSB. This could in principle be similar to some areas of the WAIS, where subglacial
sediments deposited within rift basins or forming thin marine sedimentary drapes have been inferred to exert a key
influence on both the onset and maintenance of fast-glacial flow. However, later geophysical models indicated that
the WSB contains little or no sediment, is not rift-related, and formed in response to Cenozoic flexural uplift of the
Transantarctic Mountains (TAM). A major joint Italian-UK aerogeophysical exploration campaign over parts of
the WSB is super-seeding all these earlier geophysical views of the basin (Ferraccioli et al., 2009, Tectonophysics).
Precambrian and Paleozoic basement faults can now be recognised as exerting fundamental controls on the loca-
tion of both the topographic margins of the basin and it sub-basins; ii) the crust underlying the basin is thinner
compared to the TAM (Jordan et al., 2013, Tectonophysics), but is unlikely to be strongly affected by Cretaceous
or Cenozoic-age rifting, in contrast to the WAIS, which is largely underlain by the West Antarctic Rift System;
iii) its bedrock is composed of rocks of different ages and composition, including Proterozoic basement, Neopro-
terozoic and Cambrian sediments intruded by Cambrian arc rocks, and cover rocks formed primarily by Beacon
sediments intruded by Jurassic Ferrar sills (e.g. Cook et al., 2013 Nature Geoscience). Within the framework of
the collaborative Italian-US-UK BABOC project a new international initiative has been launched to analyse and
model variable geological boundary conditions in the WSB using geophysical data. A large amount of new ICE-
CAP aerogeophysical observations have been acquired over four campaigns over the region since the International
Polar Year, in particular over the southern part of the basin, and some profiles over the northern coastal margin of
the basin. We will present an initial interpretation of the potential field signatures and radar data over the northern
and central parts of the basin to help establish tectonic and lithological controls on the subglacial topography and
different EAIS flow regimes within the WSB
Recommended from our members
UTIG's approach to managing polar aerogeophysical data in the field: philosophy and examples from fixed wing and helicopter surveys, 27 pages, 2022.
This report documents UTIG’s approach to managing aerogeophysical data in the field. This
approach to fieldwork has taken shape in the course of over 20+ years of polar campaigns
based out of over 10 Antarctic stations. Aerogeophysical survey is not simply about the act of
making measurements and observations. A key component of conducting surveys is managing
data as it is collected and providing feedback for quality control. We want to document that
institutional knowledge for the benefit of researchers who are continuing in this work as well as
for the users of our data.
While this document focuses on data management in the field, we start by providing the context
for a typical aerogeophysical campaign and describe how the work is broken up amongst
teams. We then discuss the philosophy behind field data processing, with a focus on what the
goals are for preliminary processing and how it differs from the final products. With that
motivation, we describe how the Base Operations team typically meets those goals, along with
case studies of how we have applied this approach when based at a variety of stations and field
camps, with the differing logistical challenges imposed by each.
Companion documents focusing on instrumentation and airborne operations are forthcoming.Institute for Geophysic
Supporting Data: Characterizing Sub-Glacial Hydrology Using Radar Simulations
<p>Raw data from "A Simulation Approach to Characterizing Sub-Glacial Hydrology". </p>
<p>THW2_UBH0c_X243a.M1D1 is the 1 dimensionally focused, high gain radargram from the IPR radar survey. </p>
<p>Actual along-track IPR pick data for THW2_UBH0c_X243a are contained in file X243a_rad_data_foc.csv. Metadata are as follows:</p>
<ul>
<li>pst: flight line name</li>
<li>long: observation longitude in decimal degrees (EPSG:4326)</li>
<li>lat: observation latitude in decimal degrees (EPSG:4326)</li>
<li>bed: bed pick elevation in [m]</li>
<li>year: timestamp year</li>
<li>day: timestamp day</li>
<li>t_ms: timestamp miliseconds</li>
<li>srf: surface pick elevation in [m]</li>
<li>echo: bed echo strength [dB]</li>
<li>thk: ice thickness [m]</li>
<li>Lice: estimated 2-way attenuation loss [dB]</li>
<li>R_bed: bed absolute reflectivity [dB]</li>
<li>L_unc: 2-way attenuation loss uncertainty [dB]</li>
</ul>
<p>Simulated data: A folder for each simulation contains the files listed below.</p>
<ul>
<li>Inputs:
<ul>
<li>[INPUT] Trajectory_MRS.mat: values for simulated aircraft trajectory, including total # of rangelines (TrackLengthTot), aircraft position at each rangeline in [m] (sc_position_x, sc_position_y, sc_position_z), and aircraft velocity in [m/s] (sc_vel_x, sc_vel_y, sc_vel_z)</li>
<li>bed.csv: lists all z-values in [m] for the bed surface</li>
<li>chan.csv: lists all z-values in [m] for the channel surface</li>
<li>params.txt: lists all pertinent parameters from the simulation</li>
<li>surf.csv: lists all z-values in [m] for the ice surface</li>
<li>xx.csv: lists all x-values in [m] for the ice surface</li>
<li>xx_b.csv: lists all x-values in [m] for the bed and channel surface</li>
<li>yy.csv: lists all y-values in [m] for the ice surface</li>
<li>yy_b.csv: lists all y-values in [m] for the bed and channel surface</li>
</ul>
</li>
<li>Radargrams:
<ul>
<li>RgramFocPWR_RM3_hamm.mat: Focused radargram power [dB]</li>
<li>RgramRawPWR.mat: Raw radargram power [dB]</li>
<li>RgramRCPWR.mat: Range-compressed radargram power [dB]<br>
</li>
</ul>
</li>
</ul>
EWU Open House Faculty Convocation
https://dc.ewu.edu/music_performances/1809/thumbnail.jp