Large regions of East Antarctica lack a reasonable topographic model because, until recently, only a few observations of ice thickness have been available to constrain the bedrock elevation. The acquisition of GRACE satellite gravity data has created a new opportunity to model the sub-ice topography. Here we have applied two methods for predicting topography based on the satellite data. Gravity inversion is a classical geophysical technique that predicts topography based on the physics relating it to gravity. Cokriging is a statistical method that uses the spatial covariance between datasets to predict one in the absence of the other. The geophysical and statistical solutions are compared to the best-known topography model (BEDMAP) in an area that is relatively well constrained by the BEDMAP data coverage.
Abstract Using field observations followed by petrological, geochemical, geochronological, and geophysical data, we infer the presence of a previously unknown Miocene subglacial volcanic center ~230 km from the South Pole. Evidence of volcanism is from boulders of olivine‐bearing amygdaloidal/vesicular basalt and hyaloclastite deposited in a moraine in the southern Transantarctic Mountains. 40 Ar/ 39 Ar ages from five specimens plus U‐Pb ages of detrital zircon from glacial till indicate igneous activity 25–17 Ma. The likely source of the volcanism is a circular −735 nT magnetic anomaly 60 km upflow from the sampling site. Subaqueous textures of the volcanics indicate eruption beneath ice or into water at the margin of an ice mass during the early Miocene. These rocks record the southernmost Cenozoic volcanism in Antarctica and expand the known extent of the oldest lavas associated with West Antarctic Rift system. They may be an expression of lithospheric foundering beneath the southern Transantarctic Mountains.
Airborne gravimetry has played a vital role in contributing to our knowledge of the subglacial environment in polar regions. Previous programs have produced extensive gravity data sets in Antarctica, but the resolution and accuracy of the data have been limited. We have evaluated the relative performance and suitability of two different airborne gravimeters for research applications from flight tests over the Canadian Rocky Mountains near Calgary. Survey design, mission profiles, and demands on the performance of an airborne gravimeter are different for the remote polar environment than for most commercial exploration surveys. Both systems, the AIRGrav and GT-1A, can produce higher-resolution data with improved flight efficiency than can the BGM-3 and LaCoste & Romberg gravimeters used in Antarctica. The AIRGrav and GT-1A systems are capable of draped flying of airborne gravity, allowing new applications for polar use. Both systems could provide the academic community with a significant increase in accuracy and horizontal resolution to enable major advances in understanding the subglacial environment. Compared to the GT-1A system, the AIRGrav system has a lower noise level and higher accuracy, and it is less sensitive to changing flight conditions — in particular, vertical accelerations during turbulent flights.
Operation IceBridge, a six-year NASA mission, is the largest airborne survey of Earth's polar ice ever flown. Data collected during IceBridge will help scientists bridge the gap in polar observations between NASA's Ice, Cloud and Land Elevation Satellite (ICESat), in orbit from 2003 to 2009, and ICESat-2, planned for launch in late 2015, making IceBridge critical for ensuring a continuous series of observations. Operation IceBridge is using airborne instruments to map Arctic and Antarctic areas once a year, building on two decades of repeat airborne measurements of rapidly changing areas in the Arctic. Operation IceBridge is also producing critical data that cannot be measured from space such as ice thickness measurements. The first Operation IceBridge flights were conducted in boreal spring 2009 over Greenland and the boreal fall 2009 over Antarctica. Other smaller airborne surveys around the world are also part of NASA's Operation IceBridge campaign.
The Airborne Topographic Mapper (ATM) was a scanning lidar developed and used by NASA for observing the Earth’s topography for several scientific applications, foremost of which was the measurement of changing Arctic and Antarctic ice sheets, glaciers and sea ice. ATM measured topography to an accuracy of better than 5 centimeters by incorporating measurements from GPS (global positioning system) receivers and inertial navigation system (INS) attitude sensors. The purpose of this data set is to enable users working with NASA’s ATM airborne lidar waveform data to estimate their own range calibration if using range tracking methods different from the centroid estimate included in the ATM data files (Studinger et al., 2022; https://doi.org/10.5194/tc-16-3649-2022). The airborne data are freely available from the National Snow and Ice Data Center (NSIDC) at the links listed in the table below. In pressurized aircraft the transmitted laser pulse travels through the aircraft’s optical window close to the scan mirror. Backscatter from both the scan mirror and the aircraft’s optical window in the fuselage are close in time to the transmitted laser pulse and partially overlap with the transmit waveform recorded by the ATM’s optical receiver. To record a “clean” transmit waveform the transmit pulse is sampled from behind a translucent beam splitter and subsequently injected into a multimode fiber-optic cable to provide a fixed optical delay that results in temporal separation between the recorded transmit pulse and contamination from backscattered photons from the scan mirror and the aircraft’s optical window. The delay due to the optical fiber and other system components introduce a laser time-of-flight range bias. The signal strength can also affect the calculated range in a way that depends on the waveform tracking algorithm. This variable influence, known as range walk, and the bias are determined from ground calibration measurements in which ATM data is collected from a stationary target at known range (true range) while varying the return intensity from signal extinction to detector saturation. The resulting signal-dependent deviation of measured range from the true range combine the system delay and range walk correction and are subtracted from the uncalibrated ranges to yield the calibrated range estimates "/laser/calrng" in the airborne waveform files (Studinger et al., 2022; Appendix B3; https://doi.org/10.5194/tc-16-3649-2022). This data set includes ATM ground test waveform data from the wide and narrow scanner, the true ranges, as well as the range calibration tables (caltables) used for processing the airborne data products. A MATLAB® function to read the ground test waveform data is available at: https://doi.org/10.5281/zenodo.6248436 ATM Data Product ID at NSIDCTemporal Coveragehttps://nsidc.org/data/ilatmw1b17 July 2017 - 20 November 2019https://nsidc.org/data/ilnsaw1b29 October 2017 - 20 November 2019 The file name of the groundtest calibration table that was used to process the airborne data is stored in the field "/ancillary_data/documentation/header_text" of each airborne data file. The corresponding groundtest waveform file has the same time tag and data set identifier as the calibration table file. E.g., the corresponding ground test waveform file for the calibration table “caltable_20170628_193814.atm6AT5.binned_data.txt” is “ILATMW1B_20170628_193814.atm6AT5.h5”. The table below lists the ground test waveform files that should be used for each campaign and instrument: YearCampaignData SetGroundtest Waveform Data201717-JUL-2017 25-JUL-2017ILATMW1BILATMW1B_20170628_193814.atm6AT5.h529-OCT-2017 25-NOV-2017ILATMW1BILATMW1B_20171017_141954.atm6AT6.h529-OCT-2017 25-NOV-2017ILNSAW1BILNSAW1B_20171208_122808.atm6BT7.h5201822-MAR-2018 01-MAY-2018ILATMW1BILATMW1B_20180309_110944.atm6AT6.h510-OCT-2018 16-NOV-2018ILATMW1BILATMW1B_20181002_151220.atm6AT6.h522-MAR-2018 01-MAY-2018ILNSAW1BILNSAW1B_20180301_115659.atm6DT7.h510-OCT-2018 16-NOV-2018ILNSAW1BILNSAW1B_20181002_160127.atm6DT7.h5201903-APR-2019 16-MAY-2019ILATMW1BILATMW1B_20190321_102239.atm6AT6.h503-SEP-2019 16-SEP-2019ILATMW1BILATMW1B_20190817_132201.atm6AT6.h523-OCT-2019 20-NOV-2019ILATMW1BILATMW1B_20191017_121209.atm6AT6.h503-APR-2019 16-MAY-2019ILNSAW1BILNSAW1B_20190327_105730.atm6DT7.h503-SEP-2019 16-SEP-2019ILNSAW1BILNSAW1B_20190817_131026.atm6DT7.h523-OCT-2019 20-NOV-2019ILNSAW1BILNSAW1B_20191017_122059.atm6DT7.h5See also: User guide for NASA's Airborne Topographic Mapper HDF5 Waveform Data: Products: https://doi.org/10.5281/zenodo.7246097 Collection of MATLAB® functions for working with ATM (Airborne Topographic Mapper, laser altimetry data products in HDF5 waveform format: https://github.com/mstudinger/ATM-waveform-tools Airborne Topographic Mapper (ATM) Bathymetry Toolkit (MATLAB® functions): https://doi.org/10.5281/zenodo.6341229
Using field observations followed by petrological, geochemical, geochronological, and geophysical data we infer the presence of a previously unknown Miocene subglacial volcanic center ~230 km from the South Pole. Evidence of volcanism is from boulders of olivine-bearing amygdaloidal/vesicular basalt and hyaloclastite deposited in a moraine in the southern Transantarctic Mountains. 40Ar/39Ar ages from five specimens plus U-Pb ages of detrital zircon from glacial till indicate igneous activity 25-17 Ma. The likely source of the volcanism is a circular -735 nT magnetic anomaly 60 km upflow from the sampling site. Subaqueous textures of the volcanics indicate eruption beneath ice or into water at the margin of an ice mass during the early Miocene. These rocks record the southernmost Cenozoic volcanism in Antarctica and expand the known extent of the oldest lavas associated with West Antarctic rift system. They may be an expression of lithospheric foundering beneath the southern Transantarctic Mountains.
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